Potomacapnos apeleutheron gen. et sp. nov., a new Early Cretaceous angiosperm from the Potomac Group and its implications for the evolution of eudicot leaf architecture.

PubMed

Jud, Nathan A; Hickey, Leo J

2013-12-01

Eudicots diverged early in the evolution of flowering plants and now comprise more than 70% of angiosperm species. In spite of the importance of eudicots, our understanding of the early evolution of this clade is limited by a poor fossil record and uncertainty about the order of early phylogenetic branching. The study of Lower Cretaceous fossils can reveal much about the evolution, morphology, and ecology of the eudicots. Fossils described here were collected from Aptian sediments of the Potomac Group exposed at the Dutch Gap locality in Virginia, USA. Specimens were prepared by degaging, then described and compared with leaves of relevant extant and fossil plants. We conducted a phylogenetic analysis of morphological characters using parsimony while constraining the tree search with the topology found through molecular phylogenetic analyses. The new species is closely related to ranunculalean eudicots and has leaf architecture remarkably similar to some living Fumarioideae (Papaveraceae). These are the oldest eudicot megafossils from North America, and they show complex leaf architecture reflecting developmental pathways unique to extant eudicots. The morphology and small size of the fossils suggest that they were herbaceous plants, as is seen in other putative early eudicots. The absence of co-occurring tricolpate pollen at Dutch Gap either (1) reflects low preservation probability for pollen of entomophilous herbs or (2) indicates that some leaf features of extant eudicots appeared before the origin of tricolpate pollen.

The morphophysiological dormancy in Amborella trichopoda seeds is a pleisiomorphic trait in angiosperms

PubMed Central

Gâteblé, Gildas; Villegente, Matthieu; Fabre, Isabelle; Klein, Nicolas; Anger, Nicolas; Baskin, Carol C; Scutt, Charlie P

2017-01-01

Abstract Background and Aims Recent parsimony-based reconstructions suggest that seeds of early angiosperms had either morphophysiological or physiological dormancy, with the former considered as more probable. The aim of this study was to determine the class of seed dormancy present in Amborella trichopoda, the sole living representative of the most basal angiosperm lineage Amborellales, with a view to resolving fully the class of dormancy present at the base of the angiosperm clade. Methods Drupes of A. trichopoda without fleshy parts were germinated and dissected to observe their structure and embryo growth. Pre-treatments including acid scarification, gibberellin treatment and seed excision were tested to determine their influence on dormancy breakage and germination. Character-state mapping by maximum parsimony, incorporating data from the present work and published sources, was then used to determine the likely class of dormancy present in early angiosperms. Key Results Germination in A. trichopoda requires a warm stratification period of at least approx. 90 d, which is followed by endosperm swelling, causing the water-permeable pericarp–mesocarp envelope to split open. The embryo then grows rapidly within the seed, to radicle emergence some 17 d later and cotyledon emergence after an additional 24 d. Gibberellin treatment, acid scarification and excision of seeds from the surrounding drupe tissues all promoted germination by shortening the initial phase of dormancy, prior to embryo growth. Conclusions Seeds of A. trichopoda have non-deep simple morphophysiological dormancy, in which mechanical resistance of the pericarp–mesocarp envelope plays a key role in the initial physiological phase. Maximum parsimony analyses, including data obtained in the present work, indicate that morphophysiological dormancy is likely to be a pleisiomorphic trait in flowering plants. The significance of this conclusion for studies of early angiosperm evolution is discussed. PMID:28087660

Angiosperm ovules: diversity, development, evolution

PubMed Central

Endress, Peter K.

2011-01-01

Background Ovules as developmental precursors of seeds are organs of central importance in angiosperm flowers and can be traced back in evolution to the earliest seed plants. Angiosperm ovules are diverse in their position in the ovary, nucellus thickness, number and thickness of integuments, degree and direction of curvature, and histological differentiations. There is a large body of literature on this diversity, and various views on its evolution have been proposed over the course of time. Most recently evo–devo studies have been concentrated on molecular developmental genetics in ovules of model plants. Scope The present review provides a synthetic treatment of several aspects of the sporophytic part of ovule diversity, development and evolution, based on extensive research on the vast original literature and on experience from my own comparative studies in a broad range of angiosperm clades. Conclusions In angiosperms the presence of an outer integument appears to be instrumental for ovule curvature, as indicated from studies on ovule diversity through the major clades of angiosperms, molecular developmental genetics in model species, abnormal ovules in a broad range of angiosperms, and comparison with gymnosperms with curved ovules. Lobation of integuments is not an atavism indicating evolution from telomes, but simply a morphogenetic constraint from the necessity of closure of the micropyle. Ovule shape is partly dependent on locule architecture, which is especially indicated by the occurrence of orthotropous ovules. Some ovule features are even more conservative than earlier assumed and thus of special interest in angiosperm macrosystematics. PMID:21606056

Morphological rates of angiosperm seed size evolution.

PubMed

Sims, Hallie J

2013-05-01

The evolution of seed size among angiosperms reflects their ecological diversification in a complex fitness landscape of life-history strategies. The lineages that have evolved seeds beyond the upper and lower boundaries that defined nonflowering seed plants since the Paleozoic are more dispersed across the angiosperm phylogeny than would be expected under a neutral model of phenotypic evolution. Morphological rates of seed size evolution estimated for 40 clades based on 17,375 species ranged from 0.001 (Garryales) to 0.207 (Malvales). Comparative phylogenetic analysis indicated that morphological rates are not associated with the clade's seed size but are negatively correlated with the clade's position in the overall distribution of angiosperm seed sizes; clades with seed sizes closer to the angiosperm mean had significantly higher morphological rates than clades with extremely small or extremely large seeds. Likewise, per-clade taxonomic diversification rates are not associated with the seed size of the clade but with where the clade falls within the angiosperm seed size distribution. These results suggest that evolutionary rates (morphological and taxonomic) are elevated in densely occupied regions of the seed morphospace relative to lineages whose ecophenotypic innovations have moved them toward the edges. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Functional Monoecy Due to Delayed Anther Dehiscence: A Novel Mechanism in Pseuduvaria mulgraveana (Annonaceae)

PubMed Central

Pang, Chun-Chiu; Scharaschkin, Tanya; Su, Yvonne C. F.; Saunders, Richard M. K.

2013-01-01

Unlike most genera in the early-divergent angiosperm family Annonaceae, Pseuduvaria exhibits a diversity of floral sex expression. Most species are structurally andromonoecious (or possibly androdioecious), although the hermaphroditic flowers have been inferred to be functionally pistillate, with sterile staminodes. Pseuduvaria presents an ideal model for investigating the evolution of floral sex in early-divergent angiosperms, although detailed empirical studies are currently lacking. The phenology and pollination ecology of the Australian endemic species Pseuduvaria mulgraveana are studied in detail, including evaluations of floral scent chemistry, pollen viability, and floral visitors. Results showed that the flowers are pollinated by small diurnal nitidulid beetles and are protogynous. Pollen from both hermaphroditic and staminate flowers are shown to be equally viable. The structurally hermaphroditic flowers are nevertheless functionally pistillate as anther dehiscence is delayed until after petal abscission and hence after the departure of pollinators. This mechanism to achieve functional unisexuality of flowers has not previously been reported in angiosperms. It is known that protogyny is widespread amongst early-divergent angiosperms, including the Annonaceae, and is effective in preventing autogamy. Delayed anther dehiscence represents a further elaboration of this, and is effective in preventing geitonogamy since very few sexually mature flowers occur simultaneously in an individual. We highlight the necessity for field-based empirical interpretations of functional floral sex expression prior to evaluations of evolutionary processes. PMID:23555844

The progamic phase of an early-divergent angiosperm, Annona cherimola (Annonaceae)

PubMed Central

Lora, J.; Hormaza, J. I.; Herrero, M.

2010-01-01

Background and Aims Recent studies of reproductive biology in ancient angiosperm lineages are beginning to shed light on the early evolution of flowering plants, but comparative studies are restricted by fragmented and meagre species representation in these angiosperm clades. In the present study, the progamic phase, from pollination to fertilization, is characterized in Annona cherimola, which is a member of the Annonaceae, the largest extant family among early-divergent angiosperms. Beside interest due to its phylogenetic position, this species is also an ancient crop with a clear niche for expansion in subtropical climates. Methods The kinetics of the reproductive process was established following controlled pollinations and sequential fixation. Gynoecium anatomy, pollen tube pathway, embryo sac and early post-fertilization events were characterized histochemically. Key Results A plesiomorphic gynoecium with a semi-open carpel shows a continuous secretory papillar surface along the carpel margins, which run from the stigma down to the obturator in the ovary. The pollen grains germinate in the stigma and compete in the stigma-style interface to reach the narrow secretory area that lines the margins of the semi-open stylar canal and is able to host just one to three pollen tubes. The embryo sac has eight nuclei and is well provisioned with large starch grains that are used during early cellular endosperm development. Conclusions A plesiomorphic simple gynoecium hosts a simple pollen–pistil interaction, based on a support–control system of pollen tube growth. Support is provided through basipetal secretory activity in the cells that line the pollen tube pathway. Spatial constraints, favouring pollen tube competition, are mediated by a dramatic reduction in the secretory surface available for pollen tube growth at the stigma–style interface. This extramural pollen tube competition contrasts with the intrastylar competition predominant in more recently derived lineages of angiosperms. PMID:19939980

An Ancestral Role for CONSTITUTIVE TRIPLE RESPONSE1 Proteins in Both Ethylene and Abscisic Acid Signaling1[OPEN

PubMed Central

Yasumura, Yuki; Pierik, Ronald; Kelly, Steven; Sakuta, Masaaki; Voesenek, Laurentius A.C.J.; Harberd, Nicholas P.

2015-01-01

Land plants have evolved adaptive regulatory mechanisms enabling the survival of environmental stresses associated with terrestrial life. Here, we focus on the evolution of the regulatory CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) component of the ethylene signaling pathway that modulates stress-related changes in plant growth and development. First, we compare CTR1-like proteins from a bryophyte, Physcomitrella patens (representative of early divergent land plants), with those of more recently diverged lycophyte and angiosperm species (including Arabidopsis [Arabidopsis thaliana]) and identify a monophyletic CTR1 family. The fully sequenced P. patens genome encodes only a single member of this family (PpCTR1L). Next, we compare the functions of PpCTR1L with that of related angiosperm proteins. We show that, like angiosperm CTR1 proteins (e.g. AtCTR1 of Arabidopsis), PpCTR1L modulates downstream ethylene signaling via direct interaction with ethylene receptors. These functions, therefore, likely predate the divergence of the bryophytes from the land-plant lineage. However, we also show that PpCTR1L unexpectedly has dual functions and additionally modulates abscisic acid (ABA) signaling. In contrast, while AtCTR1 lacks detectable ABA signaling functions, Arabidopsis has during evolution acquired another homolog that is functionally distinct from AtCTR1. In conclusion, the roles of CTR1-related proteins appear to have functionally diversified during land-plant evolution, and angiosperm CTR1-related proteins appear to have lost an ancestral ABA signaling function. Our study provides new insights into how molecular events such as gene duplication and functional differentiation may have contributed to the adaptive evolution of regulatory mechanisms in plants. PMID:26243614

Defining the limits of flowers: the challenge of distinguishing between the evolutionary products of simple versus compound strobili

PubMed Central

Rudall, Paula J.; Bateman, Richard M.

2010-01-01

Recent phylogenetic reconstructions suggest that axially condensed flower-like structures evolved iteratively in seed plants from either simple or compound strobili. The simple-strobilus model of flower evolution, widely applied to the angiosperm flower, interprets the inflorescence as a compound strobilus. The conifer cone and the gnetalean ‘flower’ are commonly interpreted as having evolved from a compound strobilus by extreme condensation and (at least in the case of male conifer cones) elimination of some structures present in the presumed ancestral compound strobilus. These two hypotheses have profoundly different implications for reconstructing the evolution of developmental genetic mechanisms in seed plants. If different flower-like structures evolved independently, there should intuitively be little commonality of patterning genes. However, reproductive units of some early-divergent angiosperms, including the extant genus Trithuria (Hydatellaceae) and the extinct genus Archaefructus (Archaefructaceae), apparently combine features considered typical of flowers and inflorescences. We re-evaluate several disparate strands of comparative data to explore whether flower-like structures could have arisen by co-option of flower-expressed patterning genes into independently evolved condensed inflorescences, or vice versa. We discuss the evolution of the inflorescence in both gymnosperms and angiosperms, emphasising the roles of heterotopy in dictating gender expression and heterochrony in permitting internodal compression. PMID:20047867

Defining the limits of flowers: the challenge of distinguishing between the evolutionary products of simple versus compound strobili.

PubMed

Rudall, Paula J; Bateman, Richard M

2010-02-12

Recent phylogenetic reconstructions suggest that axially condensed flower-like structures evolved iteratively in seed plants from either simple or compound strobili. The simple-strobilus model of flower evolution, widely applied to the angiosperm flower, interprets the inflorescence as a compound strobilus. The conifer cone and the gnetalean 'flower' are commonly interpreted as having evolved from a compound strobilus by extreme condensation and (at least in the case of male conifer cones) elimination of some structures present in the presumed ancestral compound strobilus. These two hypotheses have profoundly different implications for reconstructing the evolution of developmental genetic mechanisms in seed plants. If different flower-like structures evolved independently, there should intuitively be little commonality of patterning genes. However, reproductive units of some early-divergent angiosperms, including the extant genus Trithuria (Hydatellaceae) and the extinct genus Archaefructus (Archaefructaceae), apparently combine features considered typical of flowers and inflorescences. We re-evaluate several disparate strands of comparative data to explore whether flower-like structures could have arisen by co-option of flower-expressed patterning genes into independently evolved condensed inflorescences, or vice versa. We discuss the evolution of the inflorescence in both gymnosperms and angiosperms, emphasising the roles of heterotopy in dictating gender expression and heterochrony in permitting internodal compression.

A critical transition in leaf evolution facilitated the Cretaceous angiosperm revolution.

PubMed

de Boer, Hugo Jan; Eppinga, Maarten B; Wassen, Martin J; Dekker, Stefan C

2012-01-01

The revolutionary rise of broad-leaved (flowering) angiosperm plant species during the Cretaceous initiated a global ecological transformation towards modern biodiversity. Still, the mechanisms involved in this angiosperm radiation remain enigmatic. Here we show that the period of rapid angiosperm evolution initiated after the leaf interior (post venous) transport path length for water was reduced beyond the leaf interior transport path length for CO2 at a critical leaf vein density of 2.5-5 mm mm(-2). Data and our modelling approaches indicate that surpassing this critical vein density was a pivotal moment in leaf evolution that enabled evolving angiosperms to profit from developing leaves with more and smaller stomata in terms of higher carbon returns from equal water loss. Surpassing the critical vein density may therefore have facilitated evolving angiosperms to develop leaves with higher gas exchange capacities required to adapt to the Cretaceous CO2 decline and outcompete previously dominant coniferous species in the upper canopy.

Characterization of the basal angiosperm Aristolochia fimbriata: a potential experimental system for genetic studies

PubMed Central

2013-01-01

Background Previous studies in basal angiosperms have provided insight into the diversity within the angiosperm lineage and helped to polarize analyses of flowering plant evolution. However, there is still not an experimental system for genetic studies among basal angiosperms to facilitate comparative studies and functional investigation. It would be desirable to identify a basal angiosperm experimental system that possesses many of the features found in existing plant model systems (e.g., Arabidopsis and Oryza). Results We have considered all basal angiosperm families for general characteristics important for experimental systems, including availability to the scientific community, growth habit, and membership in a large basal angiosperm group that displays a wide spectrum of phenotypic diversity. Most basal angiosperms are woody or aquatic, thus are not well-suited for large scale cultivation, and were excluded. We further investigated members of Aristolochiaceae for ease of culture, life cycle, genome size, and chromosome number. We demonstrated self-compatibility for Aristolochia elegans and A. fimbriata, and transformation with a GFP reporter construct for Saruma henryi and A. fimbriata. Furthermore, A. fimbriata was easily cultivated with a life cycle of just three months, could be regenerated in a tissue culture system, and had one of the smallest genomes among basal angiosperms. An extensive multi-tissue EST dataset was produced for A. fimbriata that includes over 3.8 million 454 sequence reads. Conclusions Aristolochia fimbriata has numerous features that facilitate genetic studies and is suggested as a potential model system for use with a wide variety of technologies. Emerging genetic and genomic tools for A. fimbriata and closely related species can aid the investigation of floral biology, developmental genetics, biochemical pathways important in plant-insect interactions as well as human health, and various other features present in early angiosperms. PMID:23347749

Leaf evolution in Southern Hemisphere conifers tracks the angiosperm ecological radiation

PubMed Central

Biffin, Ed; Brodribb, Timothy J.; Hill, Robert S.; Thomas, Philip; Lowe, Andrew J.

2012-01-01

The angiosperm radiation has been linked to sharp declines in gymnosperm diversity and the virtual elimination of conifers from the tropics. The conifer family Podocarpaceae stands as an exception with highest species diversity in wet equatorial forests. It has been hypothesized that efficient light harvesting by the highly flattened leaves of several podocarp genera facilitates persistence with canopy-forming angiosperms, and the angiosperm ecological radiation may have preferentially favoured the diversification of these lineages. To test these ideas, we develop a molecular phylogeny for Podocarpaceae using Bayesian-relaxed clock methods incorporating fossil time constraints. We find several independent origins of flattened foliage types, and that these lineages have diversified predominantly through the Cenozoic and therefore among canopy-forming angiosperms. The onset of sustained foliage flattening podocarp diversification is coincident with a declining diversification rate of scale/needle-leaved lineages and also with ecological and climatic transformations linked to angiosperm foliar evolution. We demonstrate that climatic range evolution is contingent on the underlying state for leaf morphology. Taken together, our findings imply that as angiosperms came to dominate most terrestrial ecosystems, competitive interactions at the foliar level have profoundly shaped podocarp geography and as a consequence, rates of lineage diversification. PMID:21653584

Leaf evolution in Southern Hemisphere conifers tracks the angiosperm ecological radiation.

PubMed

Biffin, Ed; Brodribb, Timothy J; Hill, Robert S; Thomas, Philip; Lowe, Andrew J

2012-01-22

The angiosperm radiation has been linked to sharp declines in gymnosperm diversity and the virtual elimination of conifers from the tropics. The conifer family Podocarpaceae stands as an exception with highest species diversity in wet equatorial forests. It has been hypothesized that efficient light harvesting by the highly flattened leaves of several podocarp genera facilitates persistence with canopy-forming angiosperms, and the angiosperm ecological radiation may have preferentially favoured the diversification of these lineages. To test these ideas, we develop a molecular phylogeny for Podocarpaceae using Bayesian-relaxed clock methods incorporating fossil time constraints. We find several independent origins of flattened foliage types, and that these lineages have diversified predominantly through the Cenozoic and therefore among canopy-forming angiosperms. The onset of sustained foliage flattening podocarp diversification is coincident with a declining diversification rate of scale/needle-leaved lineages and also with ecological and climatic transformations linked to angiosperm foliar evolution. We demonstrate that climatic range evolution is contingent on the underlying state for leaf morphology. Taken together, our findings imply that as angiosperms came to dominate most terrestrial ecosystems, competitive interactions at the foliar level have profoundly shaped podocarp geography and as a consequence, rates of lineage diversification.

Exceptional preservation of tiny embryos documents seed dormancy in early angiosperms.

PubMed

Friis, Else Marie; Crane, Peter R; Pedersen, Kaj Raunsgaard; Stampanoni, Marco; Marone, Federica

2015-12-24

The rapid diversification of angiosperms through the Early Cretaceous period, between about 130-100 million years ago, initiated fundamental changes in the composition of terrestrial vegetation and is increasingly well understood on the basis of a wealth of palaeobotanical discoveries over the past four decades and their integration with improved knowledge of living angiosperms. Prevailing hypotheses, based on evidence both from living and from fossil plants, emphasize that the earliest angiosperms were plants of small stature with rapid life cycles that exploited disturbed habitats in open, or perhaps understorey, conditions. However, direct palaeontogical data relevant to understanding the seed biology and germination ecology of Early Cretaceous angiosperms are sparse. Here we report the discovery of embryos and their associated nutrient storage tissues in exceptionally well-preserved angiosperm seeds from the Early Cretaceous. Synchrotron radiation X-ray tomographic microscopy of the fossil embryos from many taxa reveals that all were tiny at the time of dispersal. These results support hypotheses based on extant plants that tiny embryos and seed dormancy are basic for angiosperms as a whole. The minute size of the fossil embryos, and the modest nutrient storage tissues dictated by the overall small seed size, is also consistent with the interpretation that many early angiosperms were opportunistic, early successional colonizers of disturbance-prone habitats.

Bayesian phylogeny of sucrose transporters: ancient origins, differential expansion and convergent evolution in monocots and dicots

PubMed Central

Peng, Duo; Gu, Xi; Xue, Liang-Jiao; Leebens-Mack, James H.; Tsai, Chung-Jui

2014-01-01

Sucrose transporters (SUTs) are essential for the export and efficient movement of sucrose from source leaves to sink organs in plants. The angiosperm SUT family was previously classified into three or four distinct groups, Types I, II (subgroup IIB), and III, with dicot-specific Type I and monocot-specific Type IIB functioning in phloem loading. To shed light on the underlying drivers of SUT evolution, Bayesian phylogenetic inference was undertaken using 41 sequenced plant genomes, including seven basal lineages at key evolutionary junctures. Our analysis supports four phylogenetically and structurally distinct SUT subfamilies, originating from two ancient groups (AG1 and AG2) that diverged early during terrestrial colonization. In both AG1 and AG2, multiple intron acquisition events in the progenitor vascular plant established the gene structures of modern SUTs. Tonoplastic Type III and plasmalemmal Type II represent evolutionarily conserved descendants of AG1 and AG2, respectively. Type I and Type IIB were previously thought to evolve after the dicot-monocot split. We show, however, that divergence of Type I from Type III SUT predated basal angiosperms, likely associated with evolution of vascular cambium and phloem transport. Type I SUT was subsequently lost in monocots along with vascular cambium, and independent evolution of Type IIB coincided with modified monocot vasculature. Both Type I and Type IIB underwent lineage-specific expansion. In multiple unrelated taxa, the newly-derived SUTs exhibit biased expression in reproductive tissues, suggesting a functional link between phloem loading and reproductive fitness. Convergent evolution of Type I and Type IIB for SUT function in phloem loading and reproductive organs supports the idea that differential vascular development in dicots and monocots is a strong driver for SUT family evolution in angiosperms. PMID:25429293

Leaf economic traits from fossils support a weedy habit for early angiosperms.

PubMed

Royer, Dana L; Miller, Ian M; Peppe, Daniel J; Hickey, Leo J

2010-03-01

Many key aspects of early angiosperms are poorly known, including their ecophysiology and associated habitats. Evidence for fast-growing, weedy angiosperms comes from the Early Cretaceous Potomac Group, where angiosperm fossils, some of them putative herbs, are found in riparian depositional settings. However, inferences of growth rate from sedimentology and growth habit are somewhat indirect; also, the geographic extent of a weedy habit in early angiosperms is poorly constrained. Using a power law between petiole width and leaf mass, we estimated the leaf mass per area (LMA) of species from three Albian (110-105 Ma) fossil floras from North America (Winthrop Formation, Patapsco Formation of the Potomac Group, and the Aspen Shale). All LMAs for angiosperm species are low (<125 g/m(2); mean = 76 g/m(2)) but are high for gymnosperm species (>240 g/m(2); mean = 291 g/m(2)). On the basis of extant relationships between LMA and other leaf economic traits such as photosynthetic rate and leaf lifespan, we conclude that these Early Cretaceous landscapes were populated with weedy angiosperms with short-lived leaves (<12 mo). The unrivalled capacity for fast growth observed today in many angiosperms was in place by no later than the Albian and likely played an important role in their subsequent ecological success.

Molecular mechanisms underlying origin and diversification of the angiosperm flower.

PubMed

Theissen, Guenter; Melzer, Rainer

2007-09-01

Understanding the mode and mechanisms of the evolution of the angiosperm flower is a long-standing and central problem of evolutionary biology and botany. It has essentially remained unsolved, however. In contrast, considerable progress has recently been made in our understanding of the genetic basis of flower development in some extant model species. The knowledge that accumulated this way has been pulled together in two major hypotheses, termed the 'ABC model' and the 'floral quartet model'. These models explain how the identity of the different types of floral organs is specified during flower development by homeotic selector genes encoding transcription factors. We intend to explain how the 'ABC model' and the 'floral quartet model' are now guiding investigations that help to understand the origin and diversification of the angiosperm flower. Investigation of orthologues of class B and class C floral homeotic genes in gymnosperms suggest that bisexuality was one of the first innovations during the origin of the flower. The transition from dimer to tetramer formation of floral homeotic proteins after establishment of class E proteins may have increased cooperativity of DNA binding of the transcription factors controlling reproductive growth. That way, we hypothesize, better 'developmental switches' originated that facilitated the early evolution of the flower. Expression studies of ABC genes in basally diverging angiosperm lineages, monocots and basal eudicots suggest that the 'classical' ABC system known from core eudicots originated from a more fuzzy system with fading borders of gene expression and gradual transitions in organ identity, by sharpening of ABC gene expression domains and organ borders. Shifting boundaries of ABC gene expression may have contributed to the diversification of the angiosperm flower many times independently, as may have changes in interactions between ABC genes and their target genes.

Molecular Mechanisms Underlying Origin and Diversification of the Angiosperm Flower

PubMed Central

Theissen, Guenter; Melzer, Rainer

2007-01-01

Background Understanding the mode and mechanisms of the evolution of the angiosperm flower is a long-standing and central problem of evolutionary biology and botany. It has essentially remained unsolved, however. In contrast, considerable progress has recently been made in our understanding of the genetic basis of flower development in some extant model species. The knowledge that accumulated this way has been pulled together in two major hypotheses, termed the ‘ABC model’ and the ‘floral quartet model’. These models explain how the identity of the different types of floral organs is specified during flower development by homeotic selector genes encoding transcription factors. Scope We intend to explain how the ‘ABC model’ and the ‘floral quartet model’ are now guiding investigations that help to understand the origin and diversification of the angiosperm flower. Conclusions Investigation of orthologues of class B and class C floral homeotic genes in gymnosperms suggest that bisexuality was one of the first innovations during the origin of the flower. The transition from dimer to tetramer formation of floral homeotic proteins after establishment of class E proteins may have increased cooperativity of DNA binding of the transcription factors controlling reproductive growth. That way, we hypothesize, better ‘developmental switches’ originated that facilitated the early evolution of the flower. Expression studies of ABC genes in basally diverging angiosperm lineages, monocots and basal eudicots suggest that the ‘classical’ ABC system known from core eudicots originated from a more fuzzy system with fading borders of gene expression and gradual transitions in organ identity, by sharpening of ABC gene expression domains and organ borders. Shifting boundaries of ABC gene expression may have contributed to the diversification of the angiosperm flower many times independently, as may have changes in interactions between ABC genes and their target genes. PMID:17670752

Leaf energy balance modelling as a tool to infer habitat preference in the early angiosperms.

PubMed

Lee, Alexandra P; Upchurch, Garland; Murchie, Erik H; Lomax, Barry H

2015-03-22

Despite more than a century of research, some key aspects of habitat preference and ecology of the earliest angiosperms remain poorly constrained. Proposed growth ecology has varied from opportunistic weedy species growing in full sun to slow-growing species limited to the shaded understorey of gymnosperm forests. Evidence suggests that the earliest angiosperms possessed low transpiration rates: gas exchange rates for extant basal angiosperms are low, as are the reconstructed gas exchange rates for the oldest known angiosperm leaf fossils. Leaves with low transpirational capacity are vulnerable to overheating in full sun, favouring the hypothesis that early angiosperms were limited to the shaded understorey. Here, modelled leaf temperatures are used to examine the thermal tolerance of some of the earliest angiosperms. Our results indicate that small leaf size could have mitigated the low transpirational cooling capacity of many early angiosperms, enabling many species to survive in full sun. We propose that during the earliest phases of the angiosperm leaf record, angiosperms may not have been limited to the understorey, and that some species were able to compete with ferns and gymnosperms in both shaded and sunny habitats, especially in the absence of competition from more rapidly growing and transpiring advanced lineages of angiosperms.

The evolution of pollen germination timing in flowering plants: Austrobaileya scandens (Austrobaileyaceae)

PubMed Central

Williams, Joseph H.

2012-01-01

Background and aims The pollination to fertilization process (progamic phase) is thought to have become greatly abbreviated with the origin of flowering plants. In order to understand what developmental mechanisms enabled the speeding of fertilization, comparative data are needed from across the group, especially from early-divergent lineages. I studied the pollen germination process of Austrobaileya scandens, a perennial vine endemic to the Wet Tropics area of northeastern Queensland, Australia, and a member of the ancient angiosperm lineage, Austrobaileyales. Methodology I used in vivo and in vitro hand pollinations and timed collections to study development from late pollen maturation to just after germination. Then I compared the contribution of pollen germination timing to progamic phase duration in 131 angiosperm species (65 families). Principal findings Mature pollen of Austrobaileya was bicellular, starchless and moderately dehydrated—water content was 31.5 % by weight and volume increased by 57.9 % upon hydration. A callose layer in the inner intine appeared only after pollination. In vivo pollen germination followed a logarithmic curve, rising from 28 % at 1 hour after pollination (hap) to 97 % at 12 hap (R2 = 0.98). Sufficient pollen germination to fertilize all ovules was predicted to have occurred within 62 min. Across angiosperms, pollen germination ranged from 1 min to >60 h long and required 8.3 ± 9.8 % of the total duration of the progamic phase. Significance Pollen of Austrobaileya has many plesiomorphic features that are thought to prolong germination. Yet its germination is quite fast for species with desiccation-tolerant pollen (range: <1 to 60 h). Austrobaileya and other early-divergent angiosperms have relatively rapid pollen germination and short progamic phases, comparable to those of many insect-pollinated monocots and eudicots. These results suggest that both the pollen germination and pollen tube growth periods were marked by acceleration of developmental processes early in angiosperm history. PMID:22567221

The evolution of pollen germination timing in flowering plants: Austrobaileya scandens (Austrobaileyaceae).

PubMed

Williams, Joseph H

2012-01-01

The pollination to fertilization process (progamic phase) is thought to have become greatly abbreviated with the origin of flowering plants. In order to understand what developmental mechanisms enabled the speeding of fertilization, comparative data are needed from across the group, especially from early-divergent lineages. I studied the pollen germination process of Austrobaileya scandens, a perennial vine endemic to the Wet Tropics area of northeastern Queensland, Australia, and a member of the ancient angiosperm lineage, Austrobaileyales. I used in vivo and in vitro hand pollinations and timed collections to study development from late pollen maturation to just after germination. Then I compared the contribution of pollen germination timing to progamic phase duration in 131 angiosperm species (65 families). Mature pollen of Austrobaileya was bicellular, starchless and moderately dehydrated-water content was 31.5 % by weight and volume increased by 57.9 % upon hydration. A callose layer in the inner intine appeared only after pollination. In vivo pollen germination followed a logarithmic curve, rising from 28 % at 1 hour after pollination (hap) to 97 % at 12 hap (R(2) = 0.98). Sufficient pollen germination to fertilize all ovules was predicted to have occurred within 62 min. Across angiosperms, pollen germination ranged from 1 min to >60 h long and required 8.3 ± 9.8 % of the total duration of the progamic phase. Pollen of Austrobaileya has many plesiomorphic features that are thought to prolong germination. Yet its germination is quite fast for species with desiccation-tolerant pollen (range: <1 to 60 h). Austrobaileya and other early-divergent angiosperms have relatively rapid pollen germination and short progamic phases, comparable to those of many insect-pollinated monocots and eudicots. These results suggest that both the pollen germination and pollen tube growth periods were marked by acceleration of developmental processes early in angiosperm history.

Paleocene floral diversities and turnover events in eastern North America and their relation to diversity models

USGS Publications Warehouse

Frederiksen, N.O.

1994-01-01

This paper uses angiosperm pollen taxon turnover (first and last appearance) and diversity events as metrics to describe the Paleocene floral history of the eastern Gulf Coast; data are from 64 samples and 67 angiosperm pollen taxa. Angiosperm pollen diversity was very low at the beginning of the Paleocene, rose slowly and then somewhat more rapidly to a maximum for the epoch in the middle of the late Paleoceneas a result of the maximum in rate of first appearances during the late early Paleocene and earliest late Paleocene. Diversity then dropped very rapidly at or near the end of the epoch as the rate of last appearances reached its maximum, resulting in the Terminal Paleocene Extinction Event. The latest Paleocene diversity decline coincided with an increase in mean annual temperature and probably in rainfall, representing the beginning of the climatic maximum for the Tertiary which characterized the early Eocene. The increase in diversity of early Paleocene floras in the eastern Gulf Coast resulted from exploitation of unfilled ecospace originating from (1) low regional diversity following the Terminal Cretaceous Extinction Event, and (2) creation of many new niches during the Paleocene, resulting, according to megafloral evidence, from a change to a new vegetation type (multistratal tropical rainforest) brought about by an increase in rainfall. The slow rate of recovery of earliest Paleocene angiosperm diversity in the eastern Gulf Coast may be explained in part by the diversity-dependence model of Carr and Kitchell (1980). However, additional factors may have contributed to the slow recovery: (1) the adverse terminal Cretaceous climates may have extended into the early Paleocene, (2) the initial Paleocene environment of the eastern Gulf Coast may have contained relatively few niches, (3) some earliest Paleocene angiosperms, particularly trees, may have had inherently poor capabilities for rapid evolution, and (4) there was a lack of significant immigration of new taxa to the region. In contrast, the earliest Eocene angiosperm flora recovered very rapidly from the Terminal Paleocene Extinction Event, and this high recovery rate resulted to a significant degree from immigration of new taxa from Europe; thus, the shape of the earliest Eocene diversity curve supports the immigration-dependence recovery model of Barry et al. (1991). ?? 1994.

Dioecy in Amborella trichopoda: evidence for genetically based sex determination and its consequences for inferences of the breeding system in early angiosperms.

PubMed

Anger, Nicolas; Fogliani, Bruno; Scutt, Charles P; Gâteblé, Gildas

2017-03-01

This work aimed to gain insight into the breeding system at the base of living angiosperms through both character state reconstructions and the study of sex ratios and phenotypes in the likely sister to all other living angiosperms, Amborella trichopoda . Sex phenotypes were mapped onto a phylogeny of basally diverging angiosperms using maximum parsimony. In parallel, sex ratios and phenotypes were studied over two consecutive flowering seasons in an ex situ population of A. trichopoda , while the sex ratio of an in situ population was also assessed. Parsimony analyses failed to resolve the breeding system present at the base of living angiosperms, but indicated the importance of A. trichopoda for the future elucidation of this question. The ex situ A. trichopoda population studied showed a primary sex ratio close to 1:1, though sex ratio bias was found in the in situ population studied. Instances of sexual instability were quantified in both populations. Sex ratio data support the presence of genetic sex determination in A. trichopoda , whose further elucidation may guide inferences on the breeding system at the base of living angiosperms. Sexual instability in A. trichopoda suggests the operation of epigenetic mechanisms, and the evolution of dioecy via a gynodioecious intermediate. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Impact of spatial constraints during seed germination on the evolution of angiosperm cotyledons: a case study from tropical Hydatellaceae (Nymphaeales).

PubMed

Sokoloff, Dmitry D; Remizowa, Margarita V; Beer, Anton S; Yadav, Shrirang R; Macfarlane, Terry D; Ramsay, Margaret M; Rudall, Paula J

2013-05-01

A bipolar embryo with cotyledons is a characteristic feature that appeared early in the evolution of seed plants. Cotyledon number is an important character in angiosperm classification. We explore the links between functional aspects of seed germination and the number and location of the cotyledons, using as a model the early-divergent angiosperm family Hydatellaceae, in which seedlings are superficially monocot-like. • Seedlings of two species of tropical Hydatellaceae were studied using light and scanning electron microscopy. • Seedlings of Trithuria cowieana bear two free cotyledons. Each cotyledon possesses a green, filiform, vascularized blade that resembles subsequent leaves, and a basal, nonvascularized, haustorial outgrowth that remains in close contact with the endosperm. Seedlings of Trithuria konkanensis have two free cotyledonary haustoria inserted close to each other and a leaf blade probably belonging to one of the cotyledons. The cotyledonary node elongates between the haustoria and the leaf blade to form a mesocotyl. • To date, the absence or presence of a cotyledonary tube represents the only known qualitative morphological difference between the two major clades of Hydatellaceae. Cotyledons with a haustorium and leaf blade are unusual at the scale of seed plants and probably evolved due to homeosis. The mesocotyl of T. konkanensis resembles that of grasses and sedges. Seedling diversity in Hydatellaceae and other seed plants is linked with the principal physical and spatial constraint of their embryo structure, with the primary root and shoot apical meristems located at opposite poles, and haustorial cotyledon tips.

Conservation of Male Sterility 2 function during spore and pollen wall development supports an evolutionarily early recruitment of a core component in the sporopollenin biosynthetic pathway.

PubMed

Wallace, Simon; Chater, Caspar C; Kamisugi, Yasuko; Cuming, Andrew C; Wellman, Charles H; Beerling, David J; Fleming, Andrew J

2015-01-01

The early evolution of plants required the acquisition of a number of key adaptations to overcome physiological difficulties associated with survival on land. One of these was a tough sporopollenin wall that enclosed reproductive propagules and provided protection from desiccation and UV-B radiation. All land plants possess such walled spores (or their derived homologue, pollen). We took a reverse genetics approach, consisting of knock-out and complementation experiments to test the functional conservation of the sporopollenin-associated gene MALE STERILTY 2 (which is essential for pollen wall development in Arabidopsis thaliana) in the bryophyte Physcomitrella patens. Knock-outs of a putative moss homologue of the A. thaliana MS2 gene, which is highly expressed in the moss sporophyte, led to spores with highly defective walls comparable to that observed in the A. thaliana ms2 mutant, and extremely compromised germination. Conversely, the moss MS2 gene could not rescue the A. thaliana ms2 phenotype. The results presented here suggest that a core component of the biochemical and developmental pathway required for angiosperm pollen wall development was recruited early in land plant evolution but the continued increase in pollen wall complexity observed in angiosperms has been accompanied by divergence in MS2 gene function. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Seed development in Trimenia (Trimeniaceae) and its bearing on the evolution of embryo-nourishing strategies in early flowering plant lineages.

PubMed

Friedman, William E; Bachelier, Julien B

2013-05-01

Seeds of most families in the ancient angiosperm lineage Austrobaileyales produce a full-fledged genetically biparental embryo-nourishing endosperm. However, seeds of fossil and extant Trimeniaceae have been described as having a perisperm, a maternal nutrient-storing and embryo-nourishing tissue derived from the nucellus of the ovule. Because perisperm is also found in Nymphaeales, another ancient angiosperm clade, the presence of a perisperm in Trimeniaceae, if confirmed, would be congruent with the hypothesis that the first angiosperms used a perisperm in addition to a minute (nutrient-transferring) endosperm. • Seed development was studied from fertilization through maturity/dormancy in Trimenia moorei and in maturing fruits of T. neocaledonica. • A persistent layer of nucellar tissue surrounds the endosperm but does not contain stored nutrients and does not function as a perisperm. The nutrient-storing and embryo-nourishing tissue in Trimenia seeds is an endosperm, as is the case in all other members of the Austrobaileyales studied to date. • The absence of a perisperm and the presence of a typical nutrient-storing and embryo-nourishing endosperm in Trimeniaceae may represent the ancestral condition for angiosperms. However, the combination of a copious nutrient-storing and embryo-nourishing perisperm with a minute endosperm, as in Nymphaeales, remains a plausible plesiomorphic condition for angiosperms as a whole. In either case, the developmental and functional biology of the diploid endosperm of Trimenia (and other Austrobaileyales) differs markedly from the diploid endosperm of Nymphaeales, and is fundamentally similar to the triploid endosperms of most other angiosperms.

Occurrence of plastids in the sperm cells of Caprifoliaceae: biparental plastid inheritance in angiosperms is unilaterally derived from maternal inheritance.

PubMed

Hu, Yingchun; Zhang, Quan; Rao, Guangyuan; Sodmergen

2008-06-01

It is widely held that organelles inherit from the maternal lineage. However, the plastid genome in quite a few angiosperms appears to be biparentally transmitted. It is unclear how and why biparental inheritance of the genome became activated. Here, we detected widespread occurrence of plastids in the sperm cells (a cellular prerequisite for biparental inheritance) of traditional Caprifoliaceae. Of the 12 genera sampled, the sperm cells of Abelia, Dipelta, Heptacodium, Kolkwitzia, Leycesteria, Linnaea, Lonicera, Symphoricarpos, Triosteum and Weigela possessed inheritable plastids. The other genera, Sambucus and Viburnum, lacked plastids in sperm cells. Interestingly, such exclusion of plastids in the sperm cells of some Caprifoliaceae appeared to be associated with the divergence of Dipsacales phylogeny. Closer examination of Weigela florida revealed that both plastids and plastid DNA were highly duplicated in the generative cells. This implies that the appearance of plastids in sperm cells involved cellular mechanisms. Because such mechanisms must enhance the strength of plastid transmission through the paternal lineage and appear ubiquitous in species exhibiting biparental or potential biparental plastid inheritance, we presume that biparental plastid genetics may be a derived trait in angiosperms. This is consistent with our extended phylogenetic analysis using species with recently discovered modes of potential plastid inheritance. The results show that basal and early angiosperms have maternal plastid transmission, whereas all potential biparental transmission occurs at terminal branches of the tree. Thus, unlike previous studies, we suggest that biparental plastid inheritance in angiosperms was unilaterally converted from the maternal transmission mode during late angiosperm evolution.

The Complete Chloroplast and Mitochondrial Genome Sequences of Boea hygrometrica: Insights into the Evolution of Plant Organellar Genomes

PubMed Central

Wang, Xumin; Deng, Xin; Zhang, Xiaowei; Hu, Songnian; Yu, Jun

2012-01-01

The complete nucleotide sequences of the chloroplast (cp) and mitochondrial (mt) genomes of resurrection plant Boea hygrometrica (Bh, Gesneriaceae) have been determined with the lengths of 153,493 bp and 510,519 bp, respectively. The smaller chloroplast genome contains more genes (147) with a 72% coding sequence, and the larger mitochondrial genome have less genes (65) with a coding faction of 12%. Similar to other seed plants, the Bh cp genome has a typical quadripartite organization with a conserved gene in each region. The Bh mt genome has three recombinant sequence repeats of 222 bp, 843 bp, and 1474 bp in length, which divide the genome into a single master circle (MC) and four isomeric molecules. Compared to other angiosperms, one remarkable feature of the Bh mt genome is the frequent transfer of genetic material from the cp genome during recent Bh evolution. We also analyzed organellar genome evolution in general regarding genome features as well as compositional dynamics of sequence and gene structure/organization, providing clues for the understanding of the evolution of organellar genomes in plants. The cp-derived sequences including tRNAs found in angiosperm mt genomes support the conclusion that frequent gene transfer events may have begun early in the land plant lineage. PMID:22291979

Synteny analysis in Rosids with a walnut physical map reveals slow genome evolution in long-lived woody perennials

USDA-ARS?s Scientific Manuscript database

Mutations often accompany DNA replication. Since there may be fewer cell cycles per year in the germlines of long-lived than short-lived angiosperms, the genomes of long-lived angiosperms may be diverging more slowly than those of short-lived angiosperms. Here we test this hypothesis. We first const...

Identification, Functional Characterization, and Evolution of Terpene Synthases from a Basal Dicot1[OPEN

PubMed Central

Yahyaa, Mosaab; Matsuba, Yuki; Brandt, Wolfgang; Doron-Faigenboim, Adi; Bar, Einat; McClain, Alan; Davidovich-Rikanati, Rachel; Lewinsohn, Efraim; Pichersky, Eran; Ibdah, Mwafaq

2015-01-01

Bay laurel (Laurus nobilis) is an agriculturally and economically important dioecious tree in the basal dicot family Lauraceae used in food and drugs and in the cosmetics industry. Bay leaves, with their abundant monoterpenes and sesquiterpenes, are used to impart flavor and aroma to food, and have also drawn attention in recent years because of their potential pharmaceutical applications. To identify terpene synthases (TPSs) involved in the production of these volatile terpenes, we performed RNA sequencing to profile the transcriptome of L. nobilis leaves. Bioinformatic analysis led to the identification of eight TPS complementary DNAs. We characterized the enzymes encoded by three of these complementary DNAs: a monoterpene synthase that belongs to the TPS-b clade catalyzes the formation of mostly 1,8-cineole; a sesquiterpene synthase belonging to the TPS-a clade catalyzes the formation of mainly cadinenes; and a diterpene synthase of the TPS-e/f clade catalyzes the formation of geranyllinalool. Comparison of the sequences of these three TPSs indicated that the TPS-a and TPS-b clades of the TPS gene family evolved early in the evolution of the angiosperm lineage, and that geranyllinalool synthase activity is the likely ancestral function in angiosperms of genes belonging to an ancient TPS-e/f subclade that diverged from the kaurene synthase gene lineages before the split of angiosperms and gymnosperms. PMID:26157114

Developmental evolution of flowering plant pollen tube cell walls: callose synthase (CalS) gene expression patterns

PubMed Central

2011-01-01

Background A number of innovations underlie the origin of rapid reproductive cycles in angiosperms. A critical early step involved the modification of an ancestrally short and slow-growing pollen tube for faster and longer distance transport of sperm to egg. Associated with this shift are the predominantly callose (1,3-β-glucan) walls and septae (callose plugs) of angiosperm pollen tubes. Callose synthesis is mediated by callose synthase (CalS). Of 12 CalS gene family members in Arabidopsis, only one (CalS5) has been directly linked to pollen tube callose. CalS5 orthologues are present in several monocot and eudicot genomes, but little is known about the evolutionary origin of CalS5 or what its ancestral function may have been. Results We investigated expression of CalS in pollen and pollen tubes of selected non-flowering seed plants (gymnosperms) and angiosperms within lineages that diverged below the monocot/eudicot node. First, we determined the nearly full length coding sequence of a CalS5 orthologue from Cabomba caroliniana (CcCalS5) (Nymphaeales). Semi-quantitative RT-PCR demonstrated low CcCalS5 expression within several vegetative tissues, but strong expression in mature pollen. CalS transcripts were detected in pollen tubes of several species within Nymphaeales and Austrobaileyales, and comparative analyses with a phylogenetically diverse group of sequenced genomes indicated homology to CalS5. We also report in silico evidence of a putative CalS5 orthologue from Amborella. Among gymnosperms, CalS5 transcripts were recovered from germinating pollen of Gnetum and Ginkgo, but a novel CalS paralog was instead amplified from germinating pollen of Pinus taeda. Conclusion The finding that CalS5 is the predominant callose synthase in pollen tubes of both early-diverging and model system angiosperms is an indicator of the homology of their novel callosic pollen tube walls and callose plugs. The data suggest that CalS5 had transient expression and pollen-specific functions in early seed plants and was then recruited to novel expression patterns and functions within pollen tube walls in an ancestor of extant angiosperms. PMID:21722365

Repeated Evolution of the Pyrrolizidine Alkaloid–Mediated Defense System in Separate Angiosperm LineagesW⃞

PubMed Central

Reimann, Andreas; Nurhayati, Niknik; Backenköhler, Anita; Ober, Dietrich

2004-01-01

Species of several unrelated families within the angiosperms are able to constitutively produce pyrrolizidine alkaloids as a defense against herbivores. In pyrrolizidine alkaloid (PA) biosynthesis, homospermidine synthase (HSS) catalyzes the first specific step. HSS was recruited during angiosperm evolution from deoxyhypusine synthase (DHS), an enzyme involved in the posttranslational activation of eukaryotic initiation factor 5A. Phylogenetic analysis of 23 cDNA sequences coding for HSS and DHS of various angiosperm species revealed at least four independent recruitments of HSS from DHS: one within the Boraginaceae, one within the monocots, and two within the Asteraceae family. Furthermore, sequence analyses indicated elevated substitution rates within HSS-coding sequences after each gene duplication, with an increased level of nonsynonymous mutations. However, the contradiction between the polyphyletic origin of the first enzyme in PA biosynthesis and the structural identity of the final biosynthetic PA products needs clarification. PMID:15466410

Are there symplastic connections between the endosperm and embryo in some angiosperms?--a lesson from the Crassulaceae family.

PubMed

Kozieradzka-Kiszkurno, Małgorzata; Płachno, Bartosz Jan

2012-10-01

It is believed that there is symplastic isolation between the embryo (new sporophyte) and the endosperm (maternal-parental origin tissue, which nourishes the embryo) in angiosperms. However, in embryological literature there are rare examples in which plasmodesmata between the embryo suspensor and endosperm cells have been recorded (three species from Fabaceae). This study was undertaken in order to test the hypothesis that plasmodesmata between the embryo suspensor and the endosperm are not so rare but also occur in other angiosperm families; in order to check this, we used the Crassulaceae family because embryogenesis in Crassulaceae has been studied extensively at an ultrastructure level recently and also we tread members of this family as model for suspensor physiology and function studies. These plasmodesmata even occurred between the basal cell of the two-celled proembryo and endosperm cells. The plasmodesmata were simple at this stage of development. During the development of the embryo proper and the suspensor, the structure of plasmodesmata changes. They were branched and connected with electron-dense material. Our results suggest that in Crassulaceae with plasmodesmata between the endosperm and suspensor, symplastic connectivity at this cell-cell boundary is still reduced or blocked at a very early stage of embryo development (before the globular stage). The occurrence of plasmodesmata between the embryo suspensor and endosperm cells suggests possible symplastic transport between these different organs, at least at a very early stage of embryo development. However, whether this transport actually occurs needs to be proven experimentally. A broader analysis of plants from various families would show whether the occurrence of plasmodesmata between the embryo suspensor and the endosperm are typical embryological characteristics and if this is useful in discussions about angiosperm systematic and evolution.

A perfect flower from the Jurassic of China

PubMed Central

Liu, Zhong-Jian; Wang, Xin

2016-01-01

Flower, enclosed ovule and tetrasporangiate anther are three major characters distinguishing angiosperms from other seed plants. Morphologically, typical flowers are characterised by an organisation with gynoecium and androecium surrounded by corolla and calyx. Theoretically, flowers are derived from their counterparts in ancient ancestral gymnosperms. However, as for when, how and from which groups, there is no consensus among botanists yet. Although angiosperm-like pollen and angiosperms have been claimed in the Triassic and Jurassic, typical flowers with the aforesaid three key characters are still missing in the pre-Cretaceous age, making many interpretations of flower evolution tentative. Thus searching for flower in the pre-Cretaceous has been a tantalising task for palaeobotanists for a long time. Here, we report a typical flower, Euanthus panii gen. et sp. nov., from the Middle–Late Jurassic of Liaoning, China. Euanthus has sepals, petals, androecium with tetrasporangiate dithecate anthers and gynoecium with enclosed ovules, organised just like in perfect flowers of extant angiosperms. The discovery of Euanthus implies that typical angiosperm flowers have already been in place in the Jurassic, and provides a new insight unavailable otherwise for the evolution of flowers. PMID:27134345

Conservation and canalization of gene expression during angiosperm diversification accompany the origin and evolution of the flower

PubMed Central

Chanderbali, André S.; Yoo, Mi-Jeong; Zahn, Laura M.; Brockington, Samuel F.; Wall, P. Kerr; Gitzendanner, Matthew A.; Albert, Victor A.; Leebens-Mack, James; Altman, Naomi S.; Ma, Hong; dePamphilis, Claude W.; Soltis, Douglas E.; Soltis, Pamela S.

2010-01-01

The origin and rapid diversification of the angiosperms (Darwin's “Abominable Mystery”) has engaged generations of researchers. Here, we examine the floral genetic programs of phylogenetically pivotal angiosperms (water lily, avocado, California poppy, and Arabidopsis) and a nonflowering seed plant (a cycad) to obtain insight into the origin and subsequent evolution of the flower. Transcriptional cascades with broadly overlapping spatial domains, resembling the hypothesized ancestral gymnosperm program, are deployed across morphologically intergrading organs in water lily and avocado flowers. In contrast, spatially discrete transcriptional programs in distinct floral organs characterize the more recently derived angiosperm lineages represented by California poppy and Arabidopsis. Deep evolutionary conservation in the genetic programs of putatively homologous floral organs traces to those operating in gymnosperm reproductive cones. Female gymnosperm cones and angiosperm carpels share conserved genetic features, which may be associated with the ovule developmental program common to both organs. However, male gymnosperm cones share genetic features with both perianth (sterile attractive and protective) organs and stamens, supporting the evolutionary origin of the floral perianth from the male genetic program of seed plants. PMID:21149731

Conservation and canalization of gene expression during angiosperm diversification accompany the origin and evolution of the flower.

PubMed

Chanderbali, André S; Yoo, Mi-Jeong; Zahn, Laura M; Brockington, Samuel F; Wall, P Kerr; Gitzendanner, Matthew A; Albert, Victor A; Leebens-Mack, James; Altman, Naomi S; Ma, Hong; dePamphilis, Claude W; Soltis, Douglas E; Soltis, Pamela S

2010-12-28

The origin and rapid diversification of the angiosperms (Darwin's "Abominable Mystery") has engaged generations of researchers. Here, we examine the floral genetic programs of phylogenetically pivotal angiosperms (water lily, avocado, California poppy, and Arabidopsis) and a nonflowering seed plant (a cycad) to obtain insight into the origin and subsequent evolution of the flower. Transcriptional cascades with broadly overlapping spatial domains, resembling the hypothesized ancestral gymnosperm program, are deployed across morphologically intergrading organs in water lily and avocado flowers. In contrast, spatially discrete transcriptional programs in distinct floral organs characterize the more recently derived angiosperm lineages represented by California poppy and Arabidopsis. Deep evolutionary conservation in the genetic programs of putatively homologous floral organs traces to those operating in gymnosperm reproductive cones. Female gymnosperm cones and angiosperm carpels share conserved genetic features, which may be associated with the ovule developmental program common to both organs. However, male gymnosperm cones share genetic features with both perianth (sterile attractive and protective) organs and stamens, supporting the evolutionary origin of the floral perianth from the male genetic program of seed plants.

A perfect flower from the Jurassic of China.

PubMed

Liu, Zhong-Jian; Wang, Xin

2016-07-03

Flower, enclosed ovule and tetrasporangiate anther are three major characters distinguishing angiosperms from other seed plants. Morphologically, typical flowers are characterised by an organisation with gynoecium and androecium surrounded by corolla and calyx. Theoretically, flowers are derived from their counterparts in ancient ancestral gymnosperms. However, as for when, how and from which groups, there is no consensus among botanists yet. Although angiosperm-like pollen and angiosperms have been claimed in the Triassic and Jurassic, typical flowers with the aforesaid three key characters are still missing in the pre-Cretaceous age, making many interpretations of flower evolution tentative. Thus searching for flower in the pre-Cretaceous has been a tantalising task for palaeobotanists for a long time. Here, we report a typical flower, Euanthus panii gen. et sp. nov. , from the Middle-Late Jurassic of Liaoning, China. Euanthus has sepals, petals, androecium with tetrasporangiate dithecate anthers and gynoecium with enclosed ovules, organised just like in perfect flowers of extant angiosperms. The discovery of Euanthus implies that typical angiosperm flowers have already been in place in the Jurassic, and provides a new insight unavailable otherwise for the evolution of flowers.

Isoprene synthase genes form a monophyletic clade of acyclic terpene synthases in the TPS-B terpene synthase family.

PubMed

Sharkey, Thomas D; Gray, Dennis W; Pell, Heather K; Breneman, Steven R; Topper, Lauren

2013-04-01

Many plants emit significant amounts of isoprene, which is hypothesized to help leaves tolerate short episodes of high temperature. Isoprene emission is found in all major groups of land plants including mosses, ferns, gymnosperms, and angiosperms; however, within these groups isoprene emission is variable. The patchy distribution of isoprene emission implies an evolutionary pattern characterized by many origins or many losses. To better understand the evolution of isoprene emission, we examine the phylogenetic relationships among isoprene synthase and monoterpene synthase genes in the angiosperms. In this study we identify nine new isoprene synthases within the rosid angiosperms. We also document the capacity of a myrcene synthase in Humulus lupulus to produce isoprene. Isoprene synthases and (E)-β-ocimene synthases form a monophyletic group within the Tps-b clade of terpene synthases. No asterid genes fall within this clade. The chemistry of isoprene synthase and ocimene synthase is similar and likely affects the apparent relationships among Tps-b enzymes. The chronology of rosid evolution suggests a Cretaceous origin followed by many losses of isoprene synthase over the course of evolutionary history. The phylogenetic pattern of Tps-b genes indicates that isoprene emission from non-rosid angiosperms likely arose independently. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

The "fossilized" mitochondrial genome of Liriodendron tulipifera: ancestral gene content and order, ancestral editing sites, and extraordinarily low mutation rate.

PubMed

Richardson, Aaron O; Rice, Danny W; Young, Gregory J; Alverson, Andrew J; Palmer, Jeffrey D

2013-04-15

The mitochondrial genomes of flowering plants vary greatly in size, gene content, gene order, mutation rate and level of RNA editing. However, the narrow phylogenetic breadth of available genomic data has limited our ability to reconstruct these traits in the ancestral flowering plant and, therefore, to infer subsequent patterns of evolution across angiosperms. We sequenced the mitochondrial genome of Liriodendron tulipifera, the first from outside the monocots or eudicots. This 553,721 bp mitochondrial genome has evolved remarkably slowly in virtually all respects, with an extraordinarily low genome-wide silent substitution rate, retention of genes frequently lost in other angiosperm lineages, and conservation of ancestral gene clusters. The mitochondrial protein genes in Liriodendron are the most heavily edited of any angiosperm characterized to date. Most of these sites are also edited in various other lineages, which allowed us to polarize losses of editing sites in other parts of the angiosperm phylogeny. Finally, we added comprehensive gene sequence data for two other magnoliids, Magnolia stellata and the more distantly related Calycanthus floridus, to measure rates of sequence evolution in Liriodendron with greater accuracy. The Magnolia genome has evolved at an even lower rate, revealing a roughly 5,000-fold range of synonymous-site divergence among angiosperms whose mitochondrial gene space has been comprehensively sequenced. Using Liriodendron as a guide, we estimate that the ancestral flowering plant mitochondrial genome contained 41 protein genes, 14 tRNA genes of mitochondrial origin, as many as 7 tRNA genes of chloroplast origin, >700 sites of RNA editing, and some 14 colinear gene clusters. Many of these gene clusters, genes and RNA editing sites have been variously lost in different lineages over the course of the ensuing ∽200 million years of angiosperm evolution.

Mimosoid legume plastome evolution: IR expansion, tandem repeat expansions, and accelerated rate of evolution in clpP.

PubMed

Dugas, Diana V; Hernandez, David; Koenen, Erik J M; Schwarz, Erika; Straub, Shannon; Hughes, Colin E; Jansen, Robert K; Nageswara-Rao, Madhugiri; Staats, Martijn; Trujillo, Joshua T; Hajrah, Nahid H; Alharbi, Njud S; Al-Malki, Abdulrahman L; Sabir, Jamal S M; Bailey, C Donovan

2015-11-23

The Leguminosae has emerged as a model for studying angiosperm plastome evolution because of its striking diversity of structural rearrangements and sequence variation. However, most of what is known about legume plastomes comes from few genera representing a subset of lineages in subfamily Papilionoideae. We investigate plastome evolution in subfamily Mimosoideae based on two newly sequenced plastomes (Inga and Leucaena) and two recently published plastomes (Acacia and Prosopis), and discuss the results in the context of other legume and rosid plastid genomes. Mimosoid plastomes have a typical angiosperm gene content and general organization as well as a generally slow rate of protein coding gene evolution, but they are the largest known among legumes. The increased length results from tandem repeat expansions and an unusual 13 kb IR-SSC boundary shift in Acacia and Inga. Mimosoid plastomes harbor additional interesting features, including loss of clpP intron1 in Inga, accelerated rates of evolution in clpP for Acacia and Inga, and dN/dS ratios consistent with neutral and positive selection for several genes. These new plastomes and results provide important resources for legume comparative genomics, plant breeding, and plastid genetic engineering, while shedding further light on the complexity of plastome evolution in legumes and angiosperms.

Towards a comprehensive picture of C-to-U RNA editing sites in angiosperm mitochondria.

PubMed

Edera, Alejandro A; Gandini, Carolina L; Sanchez-Puerta, M Virginia

2018-05-14

Our understanding of the dynamic and evolution of RNA editing in angiosperms is in part limited by the few editing sites identified to date. This study identified 10,217 editing sites from 17 diverse angiosperms. Our analyses confirmed the universality of certain features of RNA editing, and offer new evidence behind the loss of editing sites in angiosperms. RNA editing is a post-transcriptional process that substitutes cytidines (C) for uridines (U) in organellar transcripts of angiosperms. These substitutions mostly take place in mitochondrial messenger RNAs at specific positions called editing sites. By means of publicly available RNA-seq data, this study identified 10,217 editing sites in mitochondrial protein-coding genes of 17 diverse angiosperms. Even though other types of mismatches were also identified, we did not find evidence of non-canonical editing processes. The results showed an uneven distribution of editing sites among species, genes, and codon positions. The analyses revealed that editing sites were conserved across angiosperms but there were some species-specific sites. Non-synonymous editing sites were particularly highly conserved (~ 80%) across the plant species and were efficiently edited (80% editing extent). In contrast, editing sites at third codon positions were poorly conserved (~ 30%) and only partially edited (~ 40% editing extent). We found that the loss of editing sites along angiosperm evolution is mainly occurring by replacing editing sites with thymidines, instead of a degradation of the editing recognition motif around editing sites. Consecutive and highly conserved editing sites had been replaced by thymidines as result of retroprocessing, by which edited transcripts are reverse transcribed to cDNA and then integrated into the genome by homologous recombination. This phenomenon was more pronounced in eudicots, and in the gene cox1. These results suggest that retroprocessing is a widespread driving force underlying the loss of editing sites in angiosperm mitochondria.

Dynamic evolution of plant mitochondrial genomes: Mobile genes and introns and highly variable mutation rates

PubMed Central

Palmer, Jeffrey D.; Adams, Keith L.; Cho, Yangrae; Parkinson, Christopher L.; Qiu, Yin-Long; Song, Keming

2000-01-01

We summarize our recent studies showing that angiosperm mitochondrial (mt) genomes have experienced remarkably high rates of gene loss and concomitant transfer to the nucleus and of intron acquisition by horizontal transfer. Moreover, we find substantial lineage-specific variation in rates of these structural mutations and also point mutations. These findings mostly arise from a Southern blot survey of gene and intron distribution in 281 diverse angiosperms. These blots reveal numerous losses of mt ribosomal protein genes but, with one exception, only rare loss of respiratory genes. Some lineages of angiosperms have kept all of their mt ribosomal protein genes whereas others have lost most of them. These many losses appear to reflect remarkably high (and variable) rates of functional transfer of mt ribosomal protein genes to the nucleus in angiosperms. The recent transfer of cox2 to the nucleus in legumes provides both an example of interorganellar gene transfer in action and a starting point for discussion of the roles of mechanistic and selective forces in determining the distribution of genetic labor between organellar and nuclear genomes. Plant mt genomes also acquire sequences by horizontal transfer. A striking example of this is a homing group I intron in the mt cox1 gene. This extraordinarily invasive mobile element has probably been acquired over 1,000 times separately during angiosperm evolution via a recent wave of cross-species horizontal transfers. Finally, whereas all previously examined angiosperm mtDNAs have low rates of synonymous substitutions, mtDNAs of two distantly related angiosperms have highly accelerated substitution rates. PMID:10860957

Seedless fruits and the disruption of a conserved genetic pathway in angiosperm ovule development

PubMed Central

Lora, Jorge; Hormaza, José I.; Herrero, María; Gasser, Charles S.

2011-01-01

Although the biological function of fruiting is the production and dissemination of seeds, humans have developed seedless fruits in a number of plant species to facilitate consumption. Here we describe a unique spontaneous seedless mutant (Thai seedless; Ts) of Annona squamosa (sugar apple), a member of the early-divergent magnoliid angiosperm clade. Ovules (seed precursors) of the mutant lack the outer of two normal integuments, a phenocopy of the inner no outer (ino) mutant of Arabidopsis thaliana. Cloning of the INO ortholog from A. squamosa confirmed conservation of the outer integument-specific expression pattern of this gene between the two species. All regions of the gene were detectable in wild-type A. squamosa and in other members of this genus. However, no region of the INO gene could be detected in Ts plants, indicating apparent deletion of the INO locus. These results provide a case of a candidate gene approach revealing the apparent molecular basis of a useful agronomic trait (seedless fruit) in a crop species, and indicate conservation of the role of a critical regulator of ovule development between eudicots and more ancient lineages of angiosperms. The outer integument is one synapomorphy of angiosperms separating them from other extant seed plants, and the results suggest that the evolution of this structure was contemporaneous with the derivation of INO from ancestral YABBY genes. Thus, a unique lateral structure appears to have coevolved with a novel gene family member essential for the structure's formation. PMID:21402944

Changes to Cretaceous surface fire behaviour influenced the spread of the early angiosperms.

PubMed

Belcher, Claire M; Hudspith, Victoria A

2017-02-01

Angiosperms evolved and diversified during the Cretaceous period. Early angiosperms were short-stature weedy plants thought to have increased fire frequency and mortality in gymnosperm forest, aiding their own expansion. However, no explorations have considered whether the range of novel fuel types that diversified throughout the Cretaceous also altered fire behaviour, which should link more strongly to mortality than fire frequency alone. We measured ignitability and heat of combustion in analogue Cretaceous understorey fuels (conifer litter, ferns, weedy and shrubby angiosperms) and used these data to model palaeofire behaviour. Variations in ignition, driven by weedy angiosperms alone, were found to have been a less important feedback to changes in Cretaceous fire activity than previously estimated. Our model estimates suggest that fires in shrub and fern understories had significantly greater fireline intensities than those fuelled by conifer litter or weedy angiosperms, and whilst fern understories supported the most rapid fire spread, angiosperm shrubs delivered the largest amount of heat per unit area. The higher fireline intensities predicted by the models led to estimates of enhanced scorch of the gymnosperm canopy and a greater chance of transitioning to crown fires. Therefore, changes in fire behaviour driven by the addition of new Cretaceous fuel groups may have assisted the angiosperm expansion. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Evolutionarily stable size of a megagametophyte: evolution of tiny megagametophytes of angiosperms from large ones of gymnosperms.

PubMed

Sakai, Satoki

2013-02-01

To examine the factors favoring large megagametophytes of gymnosperms and tiny ones of angiosperms, a game model for seed production was developed in which megagametophytes growing in the same female parent compete for resources provided by the parent. In the model, megagametophytes may continue to grow until seed completion or may cease to grow at a certain time and regrow at pollination or fertilization. Autonomous abortion of unpollinated or unfertilized megagametophytes may occur either at pollination or fertilization. Those megagametophytes absorb a certain amount of resources before abortion, due to constraints in the signal process, in addition to the resources absorbed before pollination or fertilization. It was found that both growth habits can be the ESS: megagametophytes continue to grow without cessation and monopolize resources, such as gymnosperms, or cease to grow until fertilization to reduce the loss of resources due to autonomous abortion, such as angiosperms. The former and the latter are the ESS if the time interval between pollination and fertilization is long and short, respectively. Thus, the fertilization interval may be a critical factor selecting for large megagametophytes of gymnosperms or tiny ones of angiosperms. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Gene expression analysis of aquatic angiosperms podostemaceae to gain insight into the evolution of their enigmatic morphology.

PubMed

Koi, Satoshi; Katayama, Natsu

2013-01-01

Podostemaceae is a family of aquatic angiosperms growing submerged on rocks in fast-flowing water and called moss-like or alga-like riverweeds. It evolved remarkable innovations to adapt to such an extreme environment, one of which is reduced shoots borne on roots adhering to rock surface. Recent observations revealed that the basal subfamily Tristichoideae, like most other angiosperms, has typical shoot apical meristems (SAMs). In species of the subfamily Podostemoideae, however, shoot apical meristems (SAMs) are not formed during development and new leaves arise from the meristematic basal region of preexisting leaves. The genetic basis of this shoot organogenesis process, e.g., the expression patterns of genes homologous to transcription factors regulating shoot development, is essential to better understand the evolution of Podostemaceae. A gene expression analysis found that the SAM-less Podostemoideae leaf has mixed identity of SAM and leaf, and provided insight into the evolution of the shoot in Podostemaceae.

Insights into the origin and evolution of the plant hormone signaling machinery.

PubMed

Wang, Chunyang; Liu, Yang; Li, Si-Shen; Han, Guan-Zhu

2015-03-01

Plant hormones modulate plant growth, development, and defense. However, many aspects of the origin and evolution of plant hormone signaling pathways remain obscure. Here, we use a comparative genomic and phylogenetic approach to investigate the origin and evolution of nine major plant hormone (abscisic acid, auxin, brassinosteroid, cytokinin, ethylene, gibberellin, jasmonate, salicylic acid, and strigolactone) signaling pathways. Our multispecies genome-wide analysis reveals that: (1) auxin, cytokinin, and strigolactone signaling pathways originated in charophyte lineages; (2) abscisic acid, jasmonate, and salicylic acid signaling pathways arose in the last common ancestor of land plants; (3) gibberellin signaling evolved after the divergence of bryophytes from land plants; (4) the canonical brassinosteroid signaling originated before the emergence of angiosperms but likely after the split of gymnosperms and angiosperms; and (5) the origin of the canonical ethylene signaling pathway postdates shortly the emergence of angiosperms. Our findings might have important implications in understanding the molecular mechanisms underlying the emergence of land plants. © 2015 American Society of Plant Biologists. All Rights Reserved.

Evolution of allosteric regulation in chorismate mutases from early plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroll, Kourtney; Holland, Cynthia K.; Starks, Courtney M.

Plants, fungi, and bacteria synthesize the aromatic amino acids: l-phenylalanine, l-tyrosine, and l-tryptophan. Chorismate mutase catalyzes the branch point reaction of phenylalanine and tyrosine biosynthesis to generate prephenate. In Arabidopsis thaliana, there are two plastid-localized chorismate mutases that are allosterically regulated (AtCM1 and AtCM3) and one cytosolic isoform (AtCM2) that is unregulated. Previous analysis of plant chorismate mutases suggested that the enzymes from early plants (i.e. bryophytes/moss, lycophytes, and basal angiosperms) formed a clade distinct from the isoforms found in flowering plants; however, no biochemical information on these enzymes is available. To understand the evolution of allosteric regulation in plantmore » chorismate mutases, we analyzed a basal lineage of plant enzymes homologous to AtCM1 based on sequence similarity. The chorismate mutases from the moss/bryophyte Physcomitrella patens (PpCM1 and PpCM2), the lycophyte Selaginella moellendorffii (SmCM), and the basal angiosperm Amborella trichopoda (AmtCM1 and AmtCM2) were characterized biochemically. Tryptophan was a positive effector for each of the five enzymes examined. Histidine was a weak positive effector for PpCM1 and AmtCM1. Neither tyrosine nor phenylalanine altered the activity of SmCM; however, tyrosine was a negative regulator of the other four enzymes. Phenylalanine down-regulates both moss enzymes and AmtCM2. The 2.0 Å X-ray crystal structure of PpCM1 in complex with the tryptophan identified the allosteric effector site and reveals structural differences between the R- (more active) and T-state (less active) forms of plant chorismate mutases. Molecular insight into the basal plant chorismate mutases guides our understanding of the evolution of allosteric regulation in these enzymes.« less

To B or Not to B a flower: the role of DEFICIENS and GLOBOSA orthologs in the evolution of the angiosperms.

PubMed

Zahn, L M; Leebens-Mack, J; DePamphilis, C W; Ma, H; Theissen, G

2005-01-01

DEFICIENS (DEF) and GLOBOSA (GLO) function in petal and stamen organ identity in Antirrhinum and are orthologs of APETALA3 and PISTILLATA in Arabidopsis. These genes are known as B-function genes for their role in the ABC genetic model of floral organ identity. Phylogenetic analyses show that DEF and GLO are closely related paralogs, having originated from a gene duplication event after the separation of the lineages leading to the extant gymnosperms and the extant angiosperms. Several additional gene duplications followed, providing multiple potential opportunities for functional divergence. In most angiosperms studied to date, genes in the DEF/GLO MADS-box subfamily are expressed in the petals and stamens during flower development. However, in some angiosperms, the expression of DEF and GLO orthologs are occasionally observed in the first and fourth whorls of flowers or in nonfloral organs, where their function is unknown. In this article we review what is known about function, phylogeny, and expression in the DEF/GLO subfamily to examine their evolution in the angiosperms. Our analyses demonstrate that although the primary role of the DEF/GLO subfamily appears to be in specifying the stamens and inner perianth, several examples of potential sub- and neofunctionalization are observed.

Convergent Evolution and the Diverse Ontogenetic Origins of Tendrils in Angiosperms.

PubMed

Sousa-Baena, Mariane S; Sinha, Neelima R; Hernandes-Lopes, José; Lohmann, Lúcia G

2018-01-01

Climbers are abundant in tropical forests, where they constitute a major functional plant type. The acquisition of the climbing habit in angiosperms constitutes a key innovation. Successful speciation in climbers is correlated with the development of specialized climbing strategies such as tendrils, i.e., filiform organs with the ability to twine around other structures through helical growth. Tendrils are derived from a variety of morphological structures, e.g., stems, leaves, and inflorescences, and are found in various plant families. In fact, tendrils are distributed throughout the angiosperm phylogeny, from magnoliids to asterids II, making these structures a great model to study convergent evolution. In this study, we performed a thorough survey of tendrils within angiosperms, focusing on their origin and development. We identified 17 tendril types and analyzed their distribution through the angiosperm phylogeny. Some interesting patterns emerged. For instance, tendrils derived from reproductive structures are exclusively found in the Core Eudicots, except from one monocot species. Fabales and Asterales are the orders with the highest numbers of tendrilling strategies. Tendrils derived from modified leaflets are particularly common among asterids, occurring in Polemoniaceae, Bignoniaceae, and Asteraceae. Although angiosperms have a large number of tendrilled representatives, little is known about their origin and development. This work points out research gaps that should help guide future research on the biology of tendrilled species. Additional research on climbers is particularly important given their increasing abundance resulting from environmental disturbance in the tropics.

Convergent Evolution and the Diverse Ontogenetic Origins of Tendrils in Angiosperms

PubMed Central

Sousa-Baena, Mariane S.; Sinha, Neelima R.; Hernandes-Lopes, José; Lohmann, Lúcia G.

2018-01-01

Climbers are abundant in tropical forests, where they constitute a major functional plant type. The acquisition of the climbing habit in angiosperms constitutes a key innovation. Successful speciation in climbers is correlated with the development of specialized climbing strategies such as tendrils, i.e., filiform organs with the ability to twine around other structures through helical growth. Tendrils are derived from a variety of morphological structures, e.g., stems, leaves, and inflorescences, and are found in various plant families. In fact, tendrils are distributed throughout the angiosperm phylogeny, from magnoliids to asterids II, making these structures a great model to study convergent evolution. In this study, we performed a thorough survey of tendrils within angiosperms, focusing on their origin and development. We identified 17 tendril types and analyzed their distribution through the angiosperm phylogeny. Some interesting patterns emerged. For instance, tendrils derived from reproductive structures are exclusively found in the Core Eudicots, except from one monocot species. Fabales and Asterales are the orders with the highest numbers of tendrilling strategies. Tendrils derived from modified leaflets are particularly common among asterids, occurring in Polemoniaceae, Bignoniaceae, and Asteraceae. Although angiosperms have a large number of tendrilled representatives, little is known about their origin and development. This work points out research gaps that should help guide future research on the biology of tendrilled species. Additional research on climbers is particularly important given their increasing abundance resulting from environmental disturbance in the tropics. PMID:29666627

The evolution of desiccation-tolerance in angiosperm plants, a rare yet common phenomenon!

USDA-ARS?s Scientific Manuscript database

In a minute proportion of angiosperm species, rehydrating foliage can revive from airdryness or even from equilibration with air of ~0% relative humidity. Such desiccation tolerance is known from vegetative cells of some species of algae and of major groups close to the evolutionary path of the angi...

Co-option of the polarity gene network shapes filament morphology in angiosperms

PubMed Central

de Almeida, Ana Maria Rocha; Yockteng, Roxana; Schnable, James; Alvarez-Buylla, Elena R.; Freeling, Michael; Specht, Chelsea D.

2014-01-01

The molecular genetic mechanisms underlying abaxial-adaxial polarity in plants have been studied as a property of lateral and flattened organs, such as leaves. In leaves, laminar expansion occurs as a result of balanced abaxial-adaxial gene expression. Over- or under- expression of either abaxializing or adaxializing genes inhibits laminar growth, resulting in a mutant radialized phenotype. Here, we show that co-option of the abaxial-adaxial polarity gene network plays a role in the evolution of stamen filament morphology in angiosperms. RNA-Seq data from species bearing laminar (flattened) or radial (cylindrical) filaments demonstrates that species with laminar filaments exhibit balanced expression of abaxial-adaxial (ab-ad) genes, while overexpression of a YABBY gene is found in species with radial filaments. This result suggests that unbalanced expression of ab-ad genes results in inhibition of laminar outgrowth, leading to a radially symmetric structure as found in many angiosperm filaments. We anticipate that co-option of the polarity gene network is a fundamental mechanism shaping many aspects of plant morphology during angiosperm evolution. PMID:25168962

Co-option of the polarity gene network shapes filament morphology in angiosperms.

PubMed

de Almeida, Ana Maria Rocha; Yockteng, Roxana; Schnable, James; Alvarez-Buylla, Elena R; Freeling, Michael; Specht, Chelsea D

2014-08-29

The molecular genetic mechanisms underlying abaxial-adaxial polarity in plants have been studied as a property of lateral and flattened organs, such as leaves. In leaves, laminar expansion occurs as a result of balanced abaxial-adaxial gene expression. Over- or under- expression of either abaxializing or adaxializing genes inhibits laminar growth, resulting in a mutant radialized phenotype. Here, we show that co-option of the abaxial-adaxial polarity gene network plays a role in the evolution of stamen filament morphology in angiosperms. RNA-Seq data from species bearing laminar (flattened) or radial (cylindrical) filaments demonstrates that species with laminar filaments exhibit balanced expression of abaxial-adaxial (ab-ad) genes, while overexpression of a YABBY gene is found in species with radial filaments. This result suggests that unbalanced expression of ab-ad genes results in inhibition of laminar outgrowth, leading to a radially symmetric structure as found in many angiosperm filaments. We anticipate that co-option of the polarity gene network is a fundamental mechanism shaping many aspects of plant morphology during angiosperm evolution.

Evidence of cretaceous to recent West African intertropical vegetation from continental sediment spore-pollen analysis

NASA Astrophysics Data System (ADS)

Salard-Cheboldaeff, M.; Dejax, J.

The succession of spore-pollen assemblages during the Cretaceous and Tertiary, as defined in each of the basin from Senegal to Angola, gives the possibility to consider the intertropical African flora evolution for the past 120 M.a. During the Early Cretaceous, xeric-adapted gymnosperms and various ferns were predominant the flora which nevertheless comprises previously unknown early angiosperm pollen. During the Middle Cretaceous, gymnospers were gradually replaced by angiosperms; these became more and more abundant, along with the diversification of new genera and species. During the Paleocene, the radiation of the monocotyledons (mainly that of the palm-trees) as well as a greater diversification among the dicotyledons and ferms are noteworthy. Since gymnosperms had almost disappeared by the Eocene, the diversification of the dicotyledons went on until the neogene, when all extinct pollen types are already present. These important modifications of the vegetation reflect evolutionary trends as well as climatic changes during the Cretaceous: the climate, firstly hot, dry and perhaps arid, did probably induced salt deposition, and later became gradually more humid under oceanic influences which arose in connection with the Gondwana break-up.

Diversity patterns amongst herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/angiosperm co-evolution.

PubMed

Butler, R J; Barrett, P M; Kenrick, P; Penn, M G

2009-03-01

Palaeobiologists frequently attempt to identify examples of co-evolutionary interactions over extended geological timescales. These hypotheses are often intuitively appealing, as co-evolution is so prevalent in extant ecosystems, and are easy to formulate; however, they are much more difficult to test than their modern analogues. Among the more intriguing deep time co-evolutionary scenarios are those that relate changes in Cretaceous dinosaur faunas to the primary radiation of flowering plants. Demonstration of temporal congruence between the diversifications of co-evolving groups is necessary to establish whether co-evolution could have occurred in such cases, but is insufficient to prove whether it actually did take place. Diversity patterns do, however, provide a means for falsifying such hypotheses. We have compiled a new database of Cretaceous dinosaur and plant distributions from information in the primary literature. This is used as the basis for plotting taxonomic diversity and occurrence curves for herbivorous dinosaurs (Sauropodomorpha, Stegosauria, Ankylosauria, Ornithopoda, Ceratopsia, Pachycephalosauria and herbivorous theropods) and major groups of plants (angiosperms, Bennettitales, cycads, cycadophytes, conifers, Filicales and Ginkgoales) that co-occur in dinosaur-bearing formations. Pairwise statistical comparisons were made between various floral and faunal groups to test for any significant similarities in the shapes of their diversity curves through time. We show that, with one possible exception, diversity patterns for major groups of herbivorous dinosaurs are not positively correlated with angiosperm diversity. In other words, at the level of major clades, there is no support for any diffuse co-evolutionary relationship between herbivorous dinosaurs and flowering plants. The diversification of Late Cretaceous pachycephalosaurs (excluding the problematic taxon Stenopelix) shows a positive correlation, but this might be spuriously related to poor sampling in the Turonian-Santonian interval. Stegosauria shows a significant negative correlation with flowering plants and a significant positive correlation with the nonflowering cycadophytes (cycads, Bennettitales). This interesting pattern is worthy of further investigation, and it reflects the decline of both stegosaurs and cycadophytes during the Early Cretaceous.

Environmental control of sepalness and petalness in perianth organs of waterlilies: a new Mosaic Theory for the evolutionary origin of a differentiated perianth

PubMed Central

Warner, Kate A.; Rudall, Paula J.; Frohlich, Michael W.

2009-01-01

The conventional concept of an ‘undifferentiated perianth’, implying that all perianth organs of a flower are alike, obscures the fact that individual perianth organs are sometimes differentiated into sepaloid and petaloid regions, as in the early-divergent angiosperms Nuphar, Nymphaea, and Schisandra. In the waterlilies Nuphar and Nymphaea, sepaloid regions closely coincide with regions of the perianth that were exposed when the flower was in bud, whereas petaloid regions occur in covered regions, suggesting that their development is at least partly controlled by the environment of the developing tepal. Green and colourful areas differ from each other in trichome density and presence of papillae, features that often distinguish sepals and petals. Field experiments to test whether artificial exposure can induce sepalness in the inner tepals showed that development of sepaloid patches is initiated by exposure, at least in the waterlily species examined. Although light is an important environmental cue, other important factors include an absence of surface contact. Our interpretation contradicts the unspoken rule that ‘sepal’ and ‘petal’ must refer to whole organs. We propose a novel theory (the Mosaic theory), in which the distinction between sepalness and petalness evolved early in angiosperm history, but these features were not fixed to particular organs and were primarily environmentally controlled. At a later stage in angiosperm evolution, sepaloid and petaloid characteristics became fixed to whole organs in specific whorls, thus reducing or removing the need for environmental control in favour of fixed developmental control. PMID:19574253

After a dozen years of progress the origin of angiosperms is still a great mystery.

PubMed

Frohlich, Michael W; Chase, Mark W

2007-12-20

Here we discuss recent advances surrounding the origin of angiosperms. Putatively primitive characters are now much better understood because of a vastly improved understanding of angiosperm phylogenetics, and recent discoveries of fossil flowers have provided an increasingly detailed picture of early diversity in the angiosperms. The 'anthophyte theory', the dominant concept of the 1980s and 1990s, has been eclipsed; Gnetales, previously thought to be closest to the angiosperms, are related instead to other extant gymnosperms, probably most closely to conifers. Finally, new theories of flower origins have been proposed based on gene function, duplication and loss, as well as on morphology. Further studies of genetic mechanisms that control reproductive development in seed plants provide a most promising avenue for further research, including tests of these recent theories. Identification of fossils with morphologies that convincingly place them close to angiosperms could still revolutionize understanding of angiosperm origins.

Why does biparental plastid inheritance revive in angiosperms?

PubMed

Zhang, Quan; Sodmergen

2010-03-01

It is widely believed that plastid and mitochondrial genomes are inherited through the maternal parent. In plants, however, paternal transmission of these genomes is frequently observed, especially for the plastid genome. A male gametic trait, called potential biparental plastid inheritance (PBPI), occurs in up to 20% of angiosperm genera, implying a strong tendency for plastid transmission from the male lineage. Why do plants receive organelles from the male parents? Are there clues in plastids that will help to elucidate the evolution of plants? Reconstruction of the ancestral state of plastid inheritance patterns in a phylogenetic context provides insights into these questions. In particular, a recent report demonstrated the unilateral occurrence of PBPI in angiosperms. This result implies that nuclear cytoplasmic conflicts, a basic driving force for altering the mode of organelle inheritance, might have arisen specifically in angiosperms. Based on existing evidence, it is likely that biparental inheritance may have occurred to rescue angiosperm species with defective plastids.

Evolution of a complex behavior: the origin and initial diversification of foliar galling by Permian insects

NASA Astrophysics Data System (ADS)

Schachat, Sandra R.; Labandeira, Conrad C.

2015-04-01

A central notion of the early evolution of insect galling is that this unique behavior was uncommon to rare before the diversification of angiosperms 135 to 125 m.yr. ago. However, evidence accumulated during recent years shows that foliar galls were diverse and locally abundant as early as the Permian Period, 299 to 252 m.yr. ago. In particular, a diversity of leaf galling during the Early Permian has recently been documented by the plant-damage record of foliar galls and, now, our interpretation of the body-fossil record of culprit insect gallers. Small size is a prerequisite for gallers. Wing-length measurements of Permian insects indicate that several small-bodied hemipteroid lineages originated early during the Permian, some descendant lineages of which gall the leaves of seed plants to the present day. The earliest foliar gallers likely were Protopsyllidiidae (Hemiptera) and Lophioneuridae (Thripida). Much of the Early Permian was a xeric interval, and modern galls are most common in dry, extra-tropical habitats such as scrubland and deserts. Plant-damage, insect body fossils, and the paleoclimate record collectively support the ecological expansion of foliar galling during the Early Permian and its continued expansion through the Late Permian.

Morphological and molecular phylogenetic context of the angiosperms: contrasting the 'top-down' and 'bottom-up' approaches used to infer the likely characteristics of the first flowers.

PubMed

Bateman, Richard M; Hilton, Jason; Rudall, Paula J

2006-01-01

Recent attempts to address the long-debated 'origin' of the angiosperms depend on a phylogenetic framework derived from a matrix of taxa versus characters; most assume that empirical rigour is proportional to the size of the matrix. Sequence-based genotypic approaches increase the number of characters (nucleotides and indels) in the matrix but are confined to the highly restricted spectrum of extant species, whereas morphology-based approaches increase the number of phylogenetically informative taxa (including fossils) at the expense of accessing only a restricted spectrum of phenotypic characters. The two approaches are currently delivering strongly contrasting hypotheses of relationship. Most molecular studies indicate that all extant gymnosperms form a natural group, suggesting surprisingly early divergence of the lineage that led to angiosperms, whereas morphology-only phylogenies indicate that a succession of (mostly extinct) gymnosperms preceded a later angiosperm origin. Causes of this conflict include: (i) the vast phenotypic and genotypic lacuna, largely reflecting pre-Cenozoic extinctions, that separates early-divergent living angiosperms from their closest relatives among the living gymnosperms; (ii) profound uncertainty regarding which (a) extant and (b) extinct angiosperms are most closely related to gymnosperms; and (iii) profound uncertainty regarding which (a) extant and (b) extinct gymnosperms are most closely related to angiosperms, and thus best serve as 'outgroups' dictating the perceived evolutionary polarity of character transitions among the early-divergent angiosperms. These factors still permit a remarkable range of contrasting, yet credible, hypotheses regarding the order of acquisition of the many phenotypic characters, reproductive and vegetative, that distinguish 'classic' angiospermy from 'classic' gymnospermy. The flower remains ill-defined and its mode (or modes) of origin remains hotly disputed; some definitions and hypotheses of evolutionary relationships preclude a role for the flower in delimiting the angiosperms. We advocate maintenance of parallel, reciprocally illuminating programmes of morphological and molecular phylogeny reconstruction, respectively supported by homology testing through additional taxa (especially fossils) and evolutionary-developmental genetic studies that explore genes potentially responsible for major phenotypic transitions.

Evidence for a Cenozoic radiation of ferns in an angiosperm-dominated canopy

PubMed Central

Schuettpelz, Eric; Pryer, Kathleen M.

2009-01-01

In today's angiosperm-dominated terrestrial ecosystems, leptosporangiate ferns are truly exceptional—accounting for 80% of the ≈11,000 nonflowering vascular plant species. Recent studies have shown that this remarkable diversity is mostly the result of a major leptosporangiate radiation beginning in the Cretaceous, following the rise of angiosperms. This pattern is suggestive of an ecological opportunistic response, with the proliferation of flowering plants across the landscape resulting in the formation of many new niches—both on forest floors and within forest canopies—into which leptosporangiate ferns could diversify. At present, one-third of leptosporangiate species grow as epiphytes in the canopies of angiosperm-dominated tropical rain forests. However, we know too little about the evolutionary history of epiphytic ferns to assess whether or not their diversification was in fact linked to the establishment of these forests, as would be predicted by the ecological opportunistic response hypothesis. Here we provide new insight into leptosporangiate diversification and the evolution of epiphytism by integrating a 400-taxon molecular dataset with an expanded set of fossil age constraints. We find evidence for a burst of fern diversification in the Cenozoic, apparently driven by the evolution of epiphytism. Whether this explosive radiation was triggered simply by the establishment of modern angiosperm-dominated tropical rain forest canopies, or spurred on by some other large-scale extrinsic factor (e.g., climate change) remains to be determined. In either case, it is clear that in both the Cretaceous and Cenozoic, leptosporangiate ferns were adept at exploiting newly created niches in angiosperm-dominated ecosystems. PMID:19567832

Evidence for a Cenozoic radiation of ferns in an angiosperm-dominated canopy.

PubMed

Schuettpelz, Eric; Pryer, Kathleen M

2009-07-07

In today's angiosperm-dominated terrestrial ecosystems, leptosporangiate ferns are truly exceptional--accounting for 80% of the approximately 11,000 nonflowering vascular plant species. Recent studies have shown that this remarkable diversity is mostly the result of a major leptosporangiate radiation beginning in the Cretaceous, following the rise of angiosperms. This pattern is suggestive of an ecological opportunistic response, with the proliferation of flowering plants across the landscape resulting in the formation of many new niches--both on forest floors and within forest canopies--into which leptosporangiate ferns could diversify. At present, one-third of leptosporangiate species grow as epiphytes in the canopies of angiosperm-dominated tropical rain forests. However, we know too little about the evolutionary history of epiphytic ferns to assess whether or not their diversification was in fact linked to the establishment of these forests, as would be predicted by the ecological opportunistic response hypothesis. Here we provide new insight into leptosporangiate diversification and the evolution of epiphytism by integrating a 400-taxon molecular dataset with an expanded set of fossil age constraints. We find evidence for a burst of fern diversification in the Cenozoic, apparently driven by the evolution of epiphytism. Whether this explosive radiation was triggered simply by the establishment of modern angiosperm-dominated tropical rain forest canopies, or spurred on by some other large-scale extrinsic factor (e.g., climate change) remains to be determined. In either case, it is clear that in both the Cretaceous and Cenozoic, leptosporangiate ferns were adept at exploiting newly created niches in angiosperm-dominated ecosystems.

Three keys to the radiation of angiosperms into freezing environments.

PubMed

Zanne, Amy E; Tank, David C; Cornwell, William K; Eastman, Jonathan M; Smith, Stephen A; FitzJohn, Richard G; McGlinn, Daniel J; O'Meara, Brian C; Moles, Angela T; Reich, Peter B; Royer, Dana L; Soltis, Douglas E; Stevens, Peter F; Westoby, Mark; Wright, Ian J; Aarssen, Lonnie; Bertin, Robert I; Calaminus, Andre; Govaerts, Rafaël; Hemmings, Frank; Leishman, Michelle R; Oleksyn, Jacek; Soltis, Pamela S; Swenson, Nathan G; Warman, Laura; Beaulieu, Jeremy M

2014-02-06

Early flowering plants are thought to have been woody species restricted to warm habitats. This lineage has since radiated into almost every climate, with manifold growth forms. As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species' traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully moved into freezing-prone environments by either possessing transport networks of small safe conduits and/or shutting down hydraulic function by dropping leaves during freezing. Herbaceous species largely avoided freezing periods by senescing cheaply constructed aboveground tissue. Growth habit has long been considered labile, but we find that growth habit was less labile than climate occupancy. Additionally, freezing environments were largely filled by lineages that had already become herbs or, when remaining woody, already had small conduits (that is, the trait evolved before the climate occupancy). By contrast, most deciduous woody lineages had an evolutionary shift to seasonally shedding their leaves only after exposure to freezing (that is, the climate occupancy evolved before the trait). For angiosperms to inhabit novel cold environments they had to gain new structural and functional trait solutions; our results suggest that many of these solutions were probably acquired before their foray into the cold.

The floral morphospace – a modern comparative approach to study angiosperm evolution

PubMed Central

Chartier, Marion; Jabbour, Florian; Gerber, Sylvain; Mitteroecker, Philipp; Sauquet, Hervé; von Balthazar, Maria; Staedler, Yannick; Crane, Peter R.; Schönenberger, Jürg

2017-01-01

Summary Morphospaces are mathematical representations used for studying the evolution of morphological diversity and for the evaluation of evolved shapes among theoretically possible ones. Although widely used in zoology, they – with few exceptions – have been disregarded in plant science and in particular in the study of broad-scale patterns of floral structure and evolution. Here we provide basic information on the morphospace approach; we review earlier morphospace applications in plant science; and as a practical example, we construct and analyze a floral morphospace. Morphospaces are usually visualized with the help of ordination methods such as principal component analysis (PCA) or nonmetric multidimensional scaling (NMDS). The results of these analyses are then coupled with disparity indices that describe the spread of taxa in the space. We discuss these methods and apply modern statistical tools to the first and only angiosperm-wide floral morphospace published by Stebbins in 1951. Despite the incompleteness of Stebbins’ original dataset, our analyses highlight major, angiosperm-wide trends in the diversity of flower morphology and thereby demonstrate the power of this previously neglected approach in plant science. PMID:25539005

The Sequenced Angiosperm Genomes and Genome Databases.

PubMed

Chen, Fei; Dong, Wei; Zhang, Jiawei; Guo, Xinyue; Chen, Junhao; Wang, Zhengjia; Lin, Zhenguo; Tang, Haibao; Zhang, Liangsheng

2018-01-01

Angiosperms, the flowering plants, provide the essential resources for human life, such as food, energy, oxygen, and materials. They also promoted the evolution of human, animals, and the planet earth. Despite the numerous advances in genome reports or sequencing technologies, no review covers all the released angiosperm genomes and the genome databases for data sharing. Based on the rapid advances and innovations in the database reconstruction in the last few years, here we provide a comprehensive review for three major types of angiosperm genome databases, including databases for a single species, for a specific angiosperm clade, and for multiple angiosperm species. The scope, tools, and data of each type of databases and their features are concisely discussed. The genome databases for a single species or a clade of species are especially popular for specific group of researchers, while a timely-updated comprehensive database is more powerful for address of major scientific mysteries at the genome scale. Considering the low coverage of flowering plants in any available database, we propose construction of a comprehensive database to facilitate large-scale comparative studies of angiosperm genomes and to promote the collaborative studies of important questions in plant biology.

The Sequenced Angiosperm Genomes and Genome Databases

PubMed Central

Chen, Fei; Dong, Wei; Zhang, Jiawei; Guo, Xinyue; Chen, Junhao; Wang, Zhengjia; Lin, Zhenguo; Tang, Haibao; Zhang, Liangsheng

2018-01-01

Angiosperms, the flowering plants, provide the essential resources for human life, such as food, energy, oxygen, and materials. They also promoted the evolution of human, animals, and the planet earth. Despite the numerous advances in genome reports or sequencing technologies, no review covers all the released angiosperm genomes and the genome databases for data sharing. Based on the rapid advances and innovations in the database reconstruction in the last few years, here we provide a comprehensive review for three major types of angiosperm genome databases, including databases for a single species, for a specific angiosperm clade, and for multiple angiosperm species. The scope, tools, and data of each type of databases and their features are concisely discussed. The genome databases for a single species or a clade of species are especially popular for specific group of researchers, while a timely-updated comprehensive database is more powerful for address of major scientific mysteries at the genome scale. Considering the low coverage of flowering plants in any available database, we propose construction of a comprehensive database to facilitate large-scale comparative studies of angiosperm genomes and to promote the collaborative studies of important questions in plant biology. PMID:29706973

Unique stigmatic hairs and pollen-tube growth within the stigmatic cell wall in the early-divergent angiosperm family Hydatellaceae

PubMed Central

Prychid, Christina J.; Sokoloff, Dmitry D.; Remizowa, Margarita V.; Tuckett, Renee E.; Yadav, Shrirang R.; Rudall, Paula J.

2011-01-01

Background and Aims The ultrastructure of the pollen tubes and the unusual multicellular stigmatic hairs of Trithuria, the sole genus of Hydatellaceae, are described in the context of comparative studies of stigmatic and transmitting tissue in other early-divergent angiosperms. Methods Scanning and transmission electron microscopy and immunocytochemistry are used to study the structure and composition of both mature and immature stigmatic hair cells and pollen-tube growth in Trithuria. Key Results Trithuria possesses a dry-type stigma. Pollen tubes grow within the cell walls of the long multicellular stigmatic hairs. Immunocytochemistry results suggest that arabinogalactan proteins are involved in attracting the pollen tubes through the stigmatic cuticle. Most tubes grow along the hair axis towards its base, but some grow towards the hair apex, suggesting that pollen tubes are guided by both physical constraints such as microfibril orientation and the presence of binding factors such as unesterified pectins and adhesive proteins. Conclusions The presence of a dry-type stigma in Trithuria supports the hypothesis that this condition is ancestral in angiosperms. Each multicellular stigmatic hair of Hydatellaceae is morphologically homologous with a stigmatic papilla of other angiosperms, but functions as an independent stigma and style. This unusual combination of factors makes Hydatellaceae a useful model for comparative studies of pollen-tube growth in early angiosperms. PMID:21320877

A high-resolution angiosperm pollen reference record covering Albian mid-latitude coastal deposits (Lusitanian Basin, Portugal)

NASA Astrophysics Data System (ADS)

Horikx, Maurits; Dinis, Jorge L.; Heimhofer, Ulrich

2013-04-01

The Lusitanian Basin in Portugal is one of the most important areas to investigate the rise and radiation of early angiosperms. Here, important micro-, macro- and mesofossil remains including pollen, reproductive organs, fruits and seeds have been found. In this study, a high-resolution Early to Late Albian pollen record from a thick (~160m) coastal succession in the Lusitanian Basin containing mixed carbonate-siliciclastic near-shore deposits is generated. The outcrop is located near the town of Ericeira (São Julião) and exhibits some important new features compared to existing records from the Lusitanian basin. The comparatively proximal depositional setting and high sedimentation rate of the São Julião outcrop is well suited for high-resolution palynological sampling compared to previously studied, more distal outcrops. In addition, the succession covers almost the entire Albian including a thick interval representing Late Albian strata. Dating of the succession was obtained using dinoflagellate cyst biostratigraphy, bulk C-isotope analysis and strontium isotope analysis of low-Mg oysters and rudist shells. The high-resolution pollen record shows a distinct radiation pattern of early angiosperm pollen as well as significant changes in the accompanying palynoflora. During most of the section gymnosperm pollen types such as Classopollis spp., Inaperturopollenites spp. and Exesipollenites spp. are dominant. Angiosperm pollen abundances do not exceed 20%, although angiosperms increase slightly from the Early Albian onwards. Monoaperturate grains of magnoliid or monocot affinity remain the most dominant angiosperm pollen type, both in abundances and diversity. Tricolpate and zonoaperturate pollen grains are also present. In addition, the occurrence of several odd-shaped Dichastopollenites-type pollen types is intriguing. The palynological results indicate a warm and dry climate during most of the Albian, although a rise in the spores over pollen ratio in the second half of the section may suggest more humid conditions. In summary, the combined approach of Sr- and C-isotope stratigraphy together with marine biostratigraphy gives an accurate age assessment, which enables precise dating of the angiosperm pollen pattern emerging during the Albian.

Anatomical aspects of angiosperm root evolution

PubMed Central

Seago, James L.; Fernando, Danilo D.

2013-01-01

Background and Aims Anatomy had been one of the foundations in our understanding of plant evolutionary trends and, although recent evo-devo concepts are mostly based on molecular genetics, classical structural information remains useful as ever. Of the various plant organs, the roots have been the least studied, primarily because of the difficulty in obtaining materials, particularly from large woody species. Therefore, this review aims to provide an overview of the information that has accumulated on the anatomy of angiosperm roots and to present possible evolutionary trends between representatives of the major angiosperm clades. Scope This review covers an overview of the various aspects of the evolutionary origin of the root. The results and discussion focus on angiosperm root anatomy and evolution covering representatives from basal angiosperms, magnoliids, monocots and eudicots. We use information from the literature as well as new data from our own research. Key Findings The organization of the root apical meristem (RAM) of Nymphaeales allows for the ground meristem and protoderm to be derived from the same group of initials, similar to those of the monocots, whereas in Amborellales, magnoliids and eudicots, it is their protoderm and lateral rootcap which are derived from the same group of initials. Most members of Nymphaeales are similar to monocots in having ephemeral primary roots and so adventitious roots predominate, whereas Amborellales, Austrobaileyales, magnoliids and eudicots are generally characterized by having primary roots that give rise to a taproot system. Nymphaeales and monocots often have polyarch (heptarch or more) steles, whereas the rest of the basal angiosperms, magnoliids and eudicots usually have diarch to hexarch steles. Conclusions Angiosperms exhibit highly varied structural patterns in RAM organization; cortex, epidermis and rootcap origins; and stele patterns. Generally, however, Amborellales, magnoliids and, possibly, Austrobaileyales are more similar to eudicots, and the Nymphaeales are strongly structurally associated with the monocots, especially the Acorales. PMID:23299993

Evolutionary Dynamics of Microsatellite Distribution in Plants: Insight from the Comparison of Sequenced Brassica, Arabidopsis and Other Angiosperm Species

PubMed Central

Shi, Jiaqin; Huang, Shunmou; Fu, Donghui; Yu, Jinyin; Wang, Xinfa; Hua, Wei; Liu, Shengyi; Liu, Guihua; Wang, Hanzhong

2013-01-01

Despite their ubiquity and functional importance, microsatellites have been largely ignored in comparative genomics, mostly due to the lack of genomic information. In the current study, microsatellite distribution was characterized and compared in the whole genomes and both the coding and non-coding DNA sequences of the sequenced Brassica, Arabidopsis and other angiosperm species to investigate their evolutionary dynamics in plants. The variation in the microsatellite frequencies of these angiosperm species was much smaller than those for their microsatellite numbers and genome sizes, suggesting that microsatellite frequency may be relatively stable in plants. The microsatellite frequencies of these angiosperm species were significantly negatively correlated with both their genome sizes and transposable elements contents. The pattern of microsatellite distribution may differ according to the different genomic regions (such as coding and non-coding sequences). The observed differences in many important microsatellite characteristics (especially the distribution with respect to motif length, type and repeat number) of these angiosperm species were generally accordant with their phylogenetic distance, which suggested that the evolutionary dynamics of microsatellite distribution may be generally consistent with plant divergence/evolution. Importantly, by comparing these microsatellite characteristics (especially the distribution with respect to motif type) the angiosperm species (aside from a few species) all clustered into two obviously different groups that were largely represented by monocots and dicots, suggesting a complex and generally dichotomous evolutionary pattern of microsatellite distribution in angiosperms. Polyploidy may lead to a slight increase in microsatellite frequency in the coding sequences and a significant decrease in microsatellite frequency in the whole genome/non-coding sequences, but have little effect on the microsatellite distribution with respect to motif length, type and repeat number. Interestingly, several microsatellite characteristics seemed to be constant in plant evolution, which can be well explained by the general biological rules. PMID:23555856

Leaf evolution in early-diverging ferns: insights from a new fern-like plant from the Late Devonian of China

PubMed Central

Wang, De-Ming; Xu, Hong-He; Xue, Jin-Zhuang; Wang, Qi; Liu, Le

2015-01-01

Background and Aims With the exception of angiosperms, the main euphyllophyte lineages (i.e. ferns sensu lato, progymnosperms and gymnosperms) had evolved laminate leaves by the Late Devonian. The evolution of laminate leaves, however, remains unclear for early-diverging ferns, largely represented by fern-like plants. This study presents a novel fern-like taxon with pinnules, which provides new insights into the early evolution of laminate leaves in early-diverging ferns. Methods Macrofossil specimens were collected from the Upper Devonian (Famennian) Wutong Formation of Anhui and Jiangsu Provinces, South China. A standard degagement technique was employed to uncover compressed plant portions within the rock matrix. Key Results A new fern-like taxon, Shougangia bella gen. et sp. nov., is described and represents an early-diverging fern with highly derived features. It has a partially creeping stem with adventitious roots only on one side, upright primary and secondary branches arranged in helices, tertiary branches borne alternately or (sub)oppositely, laminate and usually lobed leaves with divergent veins, and complex fertile organs terminating tertiary branches and possessing multiple divisions and numerous terminal sporangia. Conclusions Shougangia bella provides unequivocal fossil evidence for laminate leaves in early-diverging ferns. It suggests that fern-like plants, along with other euphyllophyte lineages, had independently evolved megaphylls by the Late Devonian, possibly in response to a significant decline in atmospheric CO2 concentration. Among fern-like plants, planate ultimate appendages are homologous with laminate pinnules, and in the evolution of megaphylls, fertile organs tend to become complex. PMID:25979918

Evolution of Xylan Substitution Patterns in Gymnosperms and Angiosperms: Implications for Xylan Interaction with Cellulose1[CC-BY

PubMed Central

Li, An; Gomes, Thiago C.F.

2016-01-01

The interaction between cellulose and xylan is important for the load-bearing secondary cell wall of flowering plants. Based on the precise, evenly spaced pattern of acetyl and glucuronosyl (MeGlcA) xylan substitutions in eudicots, we recently proposed that an unsubstituted face of xylan in a 2-fold helical screw can hydrogen bond to the hydrophilic surfaces of cellulose microfibrils. In gymnosperm cell walls, any role for xylan is unclear, and glucomannan is thought to be the important cellulose-binding polysaccharide. Here, we analyzed xylan from the secondary cell walls of the four gymnosperm lineages (Conifer, Gingko, Cycad, and Gnetophyta). Conifer, Gingko, and Cycad xylan lacks acetylation but is modified by arabinose and MeGlcA. Interestingly, the arabinosyl substitutions are located two xylosyl residues from MeGlcA, which is itself placed precisely on every sixth xylosyl residue. Notably, the Gnetophyta xylan is more akin to early-branching angiosperms and eudicot xylan, lacking arabinose but possessing acetylation on alternate xylosyl residues. All these precise substitution patterns are compatible with gymnosperm xylan binding to hydrophilic surfaces of cellulose. Molecular dynamics simulations support the stable binding of 2-fold screw conifer xylan to the hydrophilic face of cellulose microfibrils. Moreover, the binding of multiple xylan chains to adjacent planes of the cellulose fibril stabilizes the interaction further. Our results show that the type of xylan substitution varies, but an even pattern of xylan substitution is maintained among vascular plants. This suggests that 2-fold screw xylan binds hydrophilic faces of cellulose in eudicots, early-branching angiosperm, and gymnosperm cell walls. PMID:27325663

Hummingbird pollination and the diversification of angiosperms: an old and successful association in Gesneriaceae

PubMed Central

Rolland, Jonathan; Clark, John L.; Salamin, Nicolas

2017-01-01

The effects of specific functional groups of pollinators in the diversification of angiosperms are still to be elucidated. We investigated whether the pollination shifts or the specific association with hummingbirds affected the diversification of a highly diverse angiosperm lineage in the Neotropics. We reconstructed a phylogeny of 583 species from the Gesneriaceae family and detected diversification shifts through time, inferred the timing and amount of transitions among pollinator functional groups, and tested the association between hummingbird pollination and speciation and extinction rates. We identified a high frequency of pollinator transitions, including reversals to insect pollination. Diversification rates of the group increased through time since 25 Ma, coinciding with the evolution of hummingbird-adapted flowers and the arrival of hummingbirds in South America. We showed that plants pollinated by hummingbirds have a twofold higher speciation rate compared with plants pollinated by insects, and that transitions among functional groups of pollinators had little impact on the diversification process. We demonstrated that floral specialization on hummingbirds for pollination has triggered rapid diversification in the Gesneriaceae family since the Early Miocene, and that it represents one of the oldest identified plant–hummingbird associations. Biotic drivers of plant diversification in the Neotropics could be more related to this specific type of pollinator (hummingbirds) than to shifts among different functional groups of pollinators. PMID:28381621

Hummingbird pollination and the diversification of angiosperms: an old and successful association in Gesneriaceae.

PubMed

Serrano-Serrano, Martha Liliana; Rolland, Jonathan; Clark, John L; Salamin, Nicolas; Perret, Mathieu

2017-04-12

The effects of specific functional groups of pollinators in the diversification of angiosperms are still to be elucidated. We investigated whether the pollination shifts or the specific association with hummingbirds affected the diversification of a highly diverse angiosperm lineage in the Neotropics. We reconstructed a phylogeny of 583 species from the Gesneriaceae family and detected diversification shifts through time, inferred the timing and amount of transitions among pollinator functional groups, and tested the association between hummingbird pollination and speciation and extinction rates. We identified a high frequency of pollinator transitions, including reversals to insect pollination. Diversification rates of the group increased through time since 25 Ma, coinciding with the evolution of hummingbird-adapted flowers and the arrival of hummingbirds in South America. We showed that plants pollinated by hummingbirds have a twofold higher speciation rate compared with plants pollinated by insects, and that transitions among functional groups of pollinators had little impact on the diversification process. We demonstrated that floral specialization on hummingbirds for pollination has triggered rapid diversification in the Gesneriaceae family since the Early Miocene, and that it represents one of the oldest identified plant-hummingbird associations. Biotic drivers of plant diversification in the Neotropics could be more related to this specific type of pollinator (hummingbirds) than to shifts among different functional groups of pollinators. © 2017 The Author(s).

The relationship of angiosperms and oleanane in petroleum through geologic time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moldowan, J.M.; Dahl, J.E.; Huizinga, B.J.

1993-02-01

The biological marker oleanane has been suggested as an indicator of angiosperm (flowering plant) input into source rocks and their derived oils. Parallels should therefore be evident between the angiosperm fossil record and oleanane occurrence and abundance. A global selection of more than 50 core samples from marine rocks of different ages and from different locations was quantitatively analyzed for oleanane to determine its abundance over geologic time relative to the bacterial marker hopane. Oleanane was recognized using Metastable Reaction Monitoring (MRM) GC-MS. A parallel was observed between the oleanane/hopane ratio and angiosperm diversity in the fossil record through time.more » The first fossil evidence of angiosperms is during the Early Cretaceous with radiation during the Late Cretaceous and Tertiary. Occurrences of oleanane are confirmed throughout the Cretaceous system. Early-to-middle Cretaceous (Berriasian-Cenomanian) occurrences are sporadic and oleanan/hopane ratios are less than 0.07. Late Cretaceous (Turonian-Maastrichtian) oleanane/hopane ratios range up to 0.15 with higher ratios in many Tertiary samples. It appears that oleanane/hopane ratios of oils can restrict the age of their unavailable or unknown source rocks. High ratios indicate Tertiary age and lower ratios can indicate Cretaceous or Tertiary age, depending on depositional environment. While these data do not rule out pre-Cretaceous oleanane, preliminary data show that oleanane/hopane ratios for Jurassic and older rock extracts are typically below our detection limits (<0.03). While oleanane precursors are abundant in angiosperms, they also occur, rarely, in other modern plant groups. We identified oleanane in low abundances in three Early Cretaceous fossil benettitialeans, an extinct plant group (Late Triassic to Late Cretaceous) thought to be related to angiosperms. These findings suggest that oleanane could be present in low abundance in some pre-Cretaceous rocks and oils.« less

Torus-margo pits help conifers compete with angiosperms.

PubMed

Pittermann, Jarmila; Sperry, John S; Hacke, Uwe G; Wheeler, James K; Sikkema, Elzard H

2005-12-23

The unicellular conifer tracheid should have greater flow resistance per length (resistivity) than the multicellular angiosperm vessel, because its high-resistance end-walls are closer together. However, tracheids and vessels had comparable resistivities for the same diameter, despite tracheids being over 10 times shorter. End-wall pits of tracheids averaged 59 times lower flow resistance on an area basis than vessel pits, owing to the unique torus-margo structure of the conifer pit membrane. The evolution of this membrane was as hydraulically important as that of vessels. Without their specialized pits, conifers would have 38 times the flow resistance, making conifer-dominated ecosystems improbable in an angiosperm world.

Evolution of a complex behavior: the origin and initial diversification of foliar galling by Permian insects.

PubMed

Schachat, Sandra R; Labandeira, Conrad C

2015-04-01

A central notion of the early evolution of insect galling is that this unique behavior was uncommon to rare before the diversification of angiosperms 135 to 125 m.yr. ago. However, evidence accumulated during recent years shows that foliar galls were diverse and locally abundant as early as the Permian Period, 299 to 252 m.yr. ago. In particular, a diversity of leaf galling during the Early Permian has recently been documented by the plant-damage record of foliar galls and, now, our interpretation of the body-fossil record of culprit insect gallers. Small size is a prerequisite for gallers. Wing-length measurements of Permian insects indicate that several small-bodied hemipteroid lineages originated early during the Permian, some descendant lineages of which gall the leaves of seed plants to the present day. The earliest foliar gallers likely were Protopsyllidiidae (Hemiptera) and Lophioneuridae (Thripida). Much of the Early Permian was a xeric interval, and modern galls are most common in dry, extra-tropical habitats such as scrubland and deserts. Plant-damage, insect body fossils, and the paleoclimate record collectively support the ecological expansion of foliar galling during the Early Permian and its continued expansion through the Late Permian.

An Evolutionarily Conserved DOF-CONSTANS Module Controls Plant Photoperiodic Signaling1[OPEN

PubMed Central

2015-01-01

The response to daylength is a crucial process that evolved very early in plant evolution, entitling the early green eukaryote to predict seasonal variability and attune its physiological responses to the environment. The photoperiod responses evolved into the complex signaling pathways that govern the angiosperm floral transition today. The Chlamydomonas reinhardtii DNA-Binding with One Finger (CrDOF) gene controls transcription in a photoperiod-dependent manner, and its misexpression influences algal growth and viability. In short days, CrDOF enhances CrCO expression, a homolog of plant CONSTANS (CO), by direct binding to its promoter, while it reduces the expression of cell division genes in long days independently of CrCO. In Arabidopsis (Arabidopsis thaliana), transgenic plants overexpressing CrDOF show floral delay and reduced expression of the photoperiodic genes CO and FLOWERING LOCUS T. The conservation of the DOF-CO module during plant evolution could be an important clue to understanding diversification by the inheritance of conserved gene toolkits in key developmental programs. PMID:25897001

Schmeissneria: a missing link to angiosperms?

PubMed

Wang, Xin; Duan, Shuying; Geng, Baoyin; Cui, Jinzhong; Yang, Yong

2007-02-07

The origin of angiosperms has been under debate since the time of Darwin. While there has been much speculation in past decades about pre-Cretaceous angiosperms, including Archaefructus, these reports are controversial. The earliest reliable fossil record of angiosperms remains restricted to the Cretaceous, even though recent molecular phylogenetic studies suggest an origin for angiosperms much earlier than the current fossil record. In this paper, after careful SEM and light microscopic work, we report fossils with angiospermous traits of the Jurassic age. The fossils were collected from the Haifanggou Formation (middle Jurassic) in western Liaoning, northeast China. They include two female structures and an associated leaf on the same slab. One of the female structures is physically connected to the apex of a short shoot. The female organs are borne in pairs on short peduncles that are arranged along the axis of the female structure. Each of the female organs has a central unit that is surrounded by an envelope with characteristic longitudinal ribs. Each central unit has two locules completely separated by a vertical septum. The apex of the central unit is completely closed. The general morphology places these fossils into the scope of Schmeissneria, an early Jurassic genus that was previously attributed to Ginkgoales. Because the closed carpel is a character only found in angiosperms, the closed apex of the central unit suggests the presence of angiospermy in Schmeissneria. This angiospermous trait implies either a Jurassic angiosperm or a new seed plant group parallel to angiosperms and other known seed plants. As an angiosperm, the Liassic age (earliest Jurassic) of Schmeissneria microstachys would suggest an origin of angiosperms during the Triassic. Although still uncertain, this could have a great impact on our perspective of the history, diversity and systematics of seed plants and angiosperms.

Seed coat thickness in the evolution of angiosperms.

PubMed

Coen, Olivier; Magnani, Enrico

2018-05-05

The seed habit represents a remarkable evolutionary advance in plant sexual reproduction. Since the Paleozoic, seeds carry a seed coat that protects, nourishes and facilitates the dispersal of the fertilization product(s). The seed coat architecture evolved to adapt to different environments and reproductive strategies in part by modifying its thickness. Here, we review the great natural diversity observed in seed coat thickness among angiosperms and its molecular regulation in Arabidopsis.

The evolution of CHROMOMETHYLASES and gene body DNA methylation in plants.

PubMed

Bewick, Adam J; Niederhuth, Chad E; Ji, Lexiang; Rohr, Nicholas A; Griffin, Patrick T; Leebens-Mack, Jim; Schmitz, Robert J

2017-05-01

The evolution of gene body methylation (gbM), its origins, and its functional consequences are poorly understood. By pairing the largest collection of transcriptomes (>1000) and methylomes (77) across Viridiplantae, we provide novel insights into the evolution of gbM and its relationship to CHROMOMETHYLASE (CMT) proteins. CMTs are evolutionary conserved DNA methyltransferases in Viridiplantae. Duplication events gave rise to what are now referred to as CMT1, 2 and 3. Independent losses of CMT1, 2, and 3 in eudicots, CMT2 and ZMET in monocots and monocots/commelinids, variation in copy number, and non-neutral evolution suggests overlapping or fluid functional evolution of this gene family. DNA methylation within genes is widespread and is found in all major taxonomic groups of Viridiplantae investigated. Genes enriched with methylated CGs (mCG) were also identified in species sister to angiosperms. The proportion of genes and DNA methylation patterns associated with gbM are restricted to angiosperms with a functional CMT3 or ortholog. However, mCG-enriched genes in the gymnosperm Pinus taeda shared some similarities with gbM genes in Amborella trichopoda. Additionally, gymnosperms and ferns share a CMT homolog closely related to CMT2 and 3. Hence, the dependency of gbM on a CMT most likely extends to all angiosperms and possibly gymnosperms and ferns. The resulting gene family phylogeny of CMT transcripts from the most diverse sampling of plants to date redefines our understanding of CMT evolution and its evolutionary consequences on DNA methylation. Future, functional tests of homologous and paralogous CMTs will uncover novel roles and consequences to the epigenome.

A single evolutionary innovation drives the deep evolution of symbiotic N2-fixation in angiosperms

PubMed Central

Werner, Gijsbert D. A.; Cornwell, William K.; Sprent, Janet I.; Kattge, Jens; Kiers, E. Toby

2014-01-01

Symbiotic associations occur in every habitat on earth, but we know very little about their evolutionary histories. Current models of trait evolution cannot adequately reconstruct the deep history of symbiotic innovation, because they assume homogenous evolutionary processes across millions of years. Here we use a recently developed, heterogeneous and quantitative phylogenetic framework to study the origin of the symbiosis between angiosperms and nitrogen-fixing (N2) bacterial symbionts housed in nodules. We compile the largest database of global nodulating plant species and reconstruct the symbiosis’ evolution. We identify a single, cryptic evolutionary innovation driving symbiotic N2-fixation evolution, followed by multiple gains and losses of the symbiosis, and the subsequent emergence of ‘stable fixers’ (clades extremely unlikely to lose the symbiosis). Originating over 100 MYA, this innovation suggests deep homology in symbiotic N2-fixation. Identifying cryptic innovations on the tree of life is key to understanding the evolution of complex traits, including symbiotic partnerships. PMID:24912610

Molecular evolution and functional characterisation of an ancient phenylalanine ammonia-lyase gene (NnPAL1) from Nelumbo nucifera: novel insight into the evolution of the PAL family in angiosperms

PubMed Central

2014-01-01

Background Phenylalanine ammonia-lyase (PAL; E.C.4.3.1.5) is a key enzyme of the phenylpropanoid pathway in plant development, and it catalyses the deamination of phenylalanine to trans-cinnamic acid, leading to the production of secondary metabolites. This enzyme has been identified in many organisms, ranging from prokaryotes to higher plants. Because Nelumbo nucifera is a basal dicot rich in many secondary metabolites, it is a suitable candidate for research on the phenylpropanoid pathway. Results Three PAL members, NnPAL1, NnPAL2 and NnPAL3, have been identified in N. nucifera using genome-wide analysis. NnPAL1 contains two introns; however, both NnPAL2 and NnPAL3 have only one intron. Molecular and evolutionary analysis of NnPAL1 confirms that it is an ancient PAL member of the angiosperms and may have a different origin. However, PAL clusters, except NnPAL1, are monophyletic after the split between dicots and monocots. These observations suggest that duplication events remain an important occurrence in the evolution of the PAL gene family. Molecular assays demonstrate that the mRNA of the NnPAL1 gene is 2343 bp in size and encodes a 717 amino acid polypeptide. The optimal pH and temperature of the recombinant NnPAL1 protein are 9.0 and 55°C, respectively. The NnPAL1 protein retains both PAL and weak TAL catalytic activities with Km values of 1.07 mM for L-phenylalanine and 3.43 mM for L-tyrosine, respectively. Cis-elements response to environmental stress are identified and confirmed using real-time PCR for treatments with abscisic acid (ABA), indoleacetic acid (IAA), ultraviolet light, Neurospora crassa (fungi) and drought. Conclusions We conclude that the angiosperm PAL genes are not derived from a single gene in an ancestral angiosperm genome; therefore, there may be another ancestral duplication and vertical inheritance from the gymnosperms. The different evolutionary histories for PAL genes in angiosperms suggest different mechanisms of functional regulation. The expression patterns of NnPAL1 in response to stress may be necessary for the survival of N. nucifera since the Cretaceous Period. The discovery and characterisation of the ancient NnPAL1 help to elucidate PAL evolution in angiosperms. PMID:24884360

Multiple Polyploidization Events across Asteraceae with Two Nested Events in the Early History Revealed by Nuclear Phylogenomics.

PubMed

Huang, Chien-Hsun; Zhang, Caifei; Liu, Mian; Hu, Yi; Gao, Tiangang; Qi, Ji; Ma, Hong

2016-11-01

Biodiversity results from multiple evolutionary mechanisms, including genetic variation and natural selection. Whole-genome duplications (WGDs), or polyploidizations, provide opportunities for large-scale genetic modifications. Many evolutionarily successful lineages, including angiosperms and vertebrates, are ancient polyploids, suggesting that WGDs are a driving force in evolution. However, this hypothesis is challenged by the observed lower speciation and higher extinction rates of recently formed polyploids than diploids. Asteraceae includes about 10% of angiosperm species, is thus undoubtedly one of the most successful lineages and paleopolyploidization was suggested early in this family using a small number of datasets. Here, we used genes from 64 new transcriptome datasets and others to reconstruct a robust Asteraceae phylogeny, covering 73 species from 18 tribes in six subfamilies. We estimated their divergence times and further identified multiple potential ancient WGDs within several tribes and shared by the Heliantheae alliance, core Asteraceae (Asteroideae-Mutisioideae), and also with the sister family Calyceraceae. For two of the WGD events, there were subsequent great increases in biodiversity; the older one proceeded the divergence of at least 10 subfamilies within 10 My, with great variation in morphology and physiology, whereas the other was followed by extremely high species richness in the Heliantheae alliance clade. Our results provide different evidence for several WGDs in Asteraceae and reveal distinct association among WGD events, dramatic changes in environment and species radiations, providing a possible scenario for polyploids to overcome the disadvantages of WGDs and to evolve into lineages with high biodiversity. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

The structure and evolution of angiosperm nuclear genomes.

PubMed

Bennetzen, J L

1998-04-01

Despite several decades of investigation, the organization of angiosperm genomes remained largely unknown until very recently. Data describing the sequence composition of large segments of genomes, covering hundreds of kilobases of contiguous sequence, have only become available in the past two years. Recent results indicate commonalities in the characteristics of many plant genomes, including in the structure of chromosomal components like telomeres and centromeres, and in the order and content of genes. Major differences between angiosperms have been associated mainly with repetitive DNAs, both gene families and mobile elements. Intriguing new studies have begun to characterize the dynamic three-dimensional structures of chromosomes and chromatin, and the relationship between genome structure and co-ordinated gene function.

Programmed cell death in seeds of angiosperms.

PubMed

López-Fernández, María Paula; Maldonado, Sara

2015-12-01

During the diversification of angiosperms, seeds have evolved structural, chemical, molecular and physiologically developing changes that specially affect the nucellus and endosperm. All through seed evolution, programmed cell death (PCD) has played a fundamental role. However, examples of PCD during seed development are limited. The present review examines PCD in integuments, nucellus, suspensor and endosperm in those representative examples of seeds studied to date. © 2015 Institute of Botany, Chinese Academy of Sciences.

More than sixty origins of pantoporate pollen in angiosperms.

PubMed

Prieu, Charlotte; Sauquet, Hervé; Gouyon, Pierre-Henri; Albert, Béatrice

2017-12-01

Apertures in pollen grains are key structures of the wall, involved in pollen tube germination and exchanges with the environment. Aperture types in angiosperms are diverse, but pollen with one and three apertures (including monosulcate and tricolpate, respectively) are the two most common types. Here, we investigate the phylogenetic distribution in angiosperms of pollen with many round, scattered apertures called pantoporate pollen. We constructed a morphological data set with species producing pantoporate pollen and representative angiosperm species with other pollen types, sampled from every angiosperm order, with a total of 1260 species distributed in 330 families. This data set was analyzed with parsimony to characterize the phylogenetic distribution of pantoporate pollen in angiosperms. We show that pantoporate pollen is distributed throughout most of the angiosperm tree, including early diverging angiosperms, monocots, and eudicots. However, this pollen type is usually restricted to a few species in a given group, and is seldom fixed at large taxonomical scales, with a few notable exceptions. Pantoporate pollen evolved many times during angiosperm history, but the persistence of this morphology in the long term is infrequent. This distribution pattern could indicate conflicting short-term and long-term selective pressures, pantoporate pollen being selected in the short run, but eliminated in the long run. Biological hypotheses supporting this scenario are discussed, in the context of both theoretical and empirical data on pollen biology. © 2017 Botanical Society of America.

Leaf evolution in early-diverging ferns: insights from a new fern-like plant from the Late Devonian of China.

PubMed

Wang, De-Ming; Xu, Hong-He; Xue, Jin-Zhuang; Wang, Qi; Liu, Le

2015-06-01

With the exception of angiosperms, the main euphyllophyte lineages (i.e. ferns sensu lato, progymnosperms and gymnosperms) had evolved laminate leaves by the Late Devonian. The evolution of laminate leaves, however, remains unclear for early-diverging ferns, largely represented by fern-like plants. This study presents a novel fern-like taxon with pinnules, which provides new insights into the early evolution of laminate leaves in early-diverging ferns. Macrofossil specimens were collected from the Upper Devonian (Famennian) Wutong Formation of Anhui and Jiangsu Provinces, South China. A standard degagement technique was employed to uncover compressed plant portions within the rock matrix. A new fern-like taxon, SHOUGANGIA BELLA GEN ET SP NOV: , is described and represents an early-diverging fern with highly derived features. It has a partially creeping stem with adventitious roots only on one side, upright primary and secondary branches arranged in helices, tertiary branches borne alternately or (sub)oppositely, laminate and usually lobed leaves with divergent veins, and complex fertile organs terminating tertiary branches and possessing multiple divisions and numerous terminal sporangia. Shougangia bella provides unequivocal fossil evidence for laminate leaves in early-diverging ferns. It suggests that fern-like plants, along with other euphyllophyte lineages, had independently evolved megaphylls by the Late Devonian, possibly in response to a significant decline in atmospheric CO2 concentration. Among fern-like plants, planate ultimate appendages are homologous with laminate pinnules, and in the evolution of megaphylls, fertile organs tend to become complex. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Teaching the Evolution of the Angiosperm Carpel.

ERIC Educational Resources Information Center

Laferriere, Joseph E.

1992-01-01

The carpel is a highly modified leaf enclosing the ovules. This article describes methods for teaching about the evolution of the carpel and the nature of carpel fusion. Presents an illustration of the evolution of the most common types of compound pistil arrangement from the ancestral single-carpel marginal type of placentation. (PR)

Exploring Early Angiosperm Fire Feedbacks using Coupled Experiments and Modelling Approaches to Estimate Cretaceous Palaeofire Behaviour

NASA Astrophysics Data System (ADS)

Belcher, Claire; Hudpsith, Victoria

2016-04-01

Using the fossil record we are typically limited to exploring linkages between palaeoecological changes and palaeofire activity by assessing the abundance of charcoals preserved in sediments. However, it is the behaviour of fires that primarily governs their ecological effects. Therefore, the ability to estimate variations in aspects of palaeofire behaviour such as palaeofire intensity and rate of spread would be of key benefit toward understanding the coupled evolutionary history of ecosystems and fire. The Cretaceous Period saw major diversification in land plants. Previously, conifers (gymnosperms) and ferns (pteridophytes) dominated Earth's ecosystems until flowering plants (angiosperms) appear in the fossil record of the Early Cretaceous (~135Ma). We have created surface fire behaviour estimates for a variety of angiosperm invasion scenarios and explored the influence of Cretaceous superambient atmospheric oxygen levels on the fire behaviour occurring in these new Cretaceous ecosystems. These estimates are then used to explore the hypothesis that the early spread of the angiosperms was promoted by the novel fire regimes that they created. In order to achieve this we tested the flammability of Mesozoic analogue fuel types in controlled laboratory experiments using an iCone calorimeter, which measured the ignitability as well as the effective heat of combustion of the fuels. We then used the BehavePlus fire behaviour modelling system to scale up our laboratory results to the ecosystem scale. Our results suggest that fire-angiosperm feedbacks may have occurred in two phases: The first phase being a result of weedy angiosperms providing an additional easily ignitable fuel that enhanced both the seasonality and frequency of surface fires. In the second phase, the addition of shrubby understory fuels likely expanded the number of ecosystems experiencing more intense surface fires, resulting in enhanced mortality and suppressed post-fire recruitment of gymnosperms trees. Both of these were assisted by rising levels of atmospheric oxygen that increased ignitability, surface fire spread rates and fire intensity. Therefore, the expansion and ecological success of the angiosperms appears to have been tied to the coupled influences of the prevailing superambient oxygen levels in the atmosphere and to fuel driven changes in palaeofire behaviour.

Plant genetics. Early allopolyploid evolution in the post-Neolithic Brassica napus oilseed genome.

PubMed

Chalhoub, Boulos; Denoeud, France; Liu, Shengyi; Parkin, Isobel A P; Tang, Haibao; Wang, Xiyin; Chiquet, Julien; Belcram, Harry; Tong, Chaobo; Samans, Birgit; Corréa, Margot; Da Silva, Corinne; Just, Jérémy; Falentin, Cyril; Koh, Chu Shin; Le Clainche, Isabelle; Bernard, Maria; Bento, Pascal; Noel, Benjamin; Labadie, Karine; Alberti, Adriana; Charles, Mathieu; Arnaud, Dominique; Guo, Hui; Daviaud, Christian; Alamery, Salman; Jabbari, Kamel; Zhao, Meixia; Edger, Patrick P; Chelaifa, Houda; Tack, David; Lassalle, Gilles; Mestiri, Imen; Schnel, Nicolas; Le Paslier, Marie-Christine; Fan, Guangyi; Renault, Victor; Bayer, Philippe E; Golicz, Agnieszka A; Manoli, Sahana; Lee, Tae-Ho; Thi, Vinh Ha Dinh; Chalabi, Smahane; Hu, Qiong; Fan, Chuchuan; Tollenaere, Reece; Lu, Yunhai; Battail, Christophe; Shen, Jinxiong; Sidebottom, Christine H D; Wang, Xinfa; Canaguier, Aurélie; Chauveau, Aurélie; Bérard, Aurélie; Deniot, Gwenaëlle; Guan, Mei; Liu, Zhongsong; Sun, Fengming; Lim, Yong Pyo; Lyons, Eric; Town, Christopher D; Bancroft, Ian; Wang, Xiaowu; Meng, Jinling; Ma, Jianxin; Pires, J Chris; King, Graham J; Brunel, Dominique; Delourme, Régine; Renard, Michel; Aury, Jean-Marc; Adams, Keith L; Batley, Jacqueline; Snowdon, Rod J; Tost, Jorg; Edwards, David; Zhou, Yongming; Hua, Wei; Sharpe, Andrew G; Paterson, Andrew H; Guan, Chunyun; Wincker, Patrick

2014-08-22

Oilseed rape (Brassica napus L.) was formed ~7500 years ago by hybridization between B. rapa and B. oleracea, followed by chromosome doubling, a process known as allopolyploidy. Together with more ancient polyploidizations, this conferred an aggregate 72× genome multiplication since the origin of angiosperms and high gene content. We examined the B. napus genome and the consequences of its recent duplication. The constituent An and Cn subgenomes are engaged in subtle structural, functional, and epigenetic cross-talk, with abundant homeologous exchanges. Incipient gene loss and expression divergence have begun. Selection in B. napus oilseed types has accelerated the loss of glucosinolate genes, while preserving expansion of oil biosynthesis genes. These processes provide insights into allopolyploid evolution and its relationship with crop domestication and improvement. Copyright © 2014, American Association for the Advancement of Science.

Implications of the plastid genome sequence of typha (typhaceae, poales) for understanding genome evolution in poaceae.

PubMed

Guisinger, Mary M; Chumley, Timothy W; Kuehl, Jennifer V; Boore, Jeffrey L; Jansen, Robert K

2010-02-01

Plastid genomes of the grasses (Poaceae) are unusual in their organization and rates of sequence evolution. There has been a recent surge in the availability of grass plastid genome sequences, but a comprehensive comparative analysis of genome evolution has not been performed that includes any related families in the Poales. We report on the plastid genome of Typha latifolia, the first non-grass Poales sequenced to date, and we present comparisons of genome organization and sequence evolution within Poales. Our results confirm that grass plastid genomes exhibit acceleration in both genomic rearrangements and nucleotide substitutions. Poaceae have multiple structural rearrangements, including three inversions, three genes losses (accD, ycf1, ycf2), intron losses in two genes (clpP, rpoC1), and expansion of the inverted repeat (IR) into both large and small single-copy regions. These rearrangements are restricted to the Poaceae, and IR expansion into the small single-copy region correlates with the phylogeny of the family. Comparisons of 73 protein-coding genes for 47 angiosperms including nine Poaceae genera confirm that the branch leading to Poaceae has significantly accelerated rates of change relative to other monocots and angiosperms. Furthermore, rates of sequence evolution within grasses are lower, indicating a deceleration during diversification of the family. Overall there is a strong correlation between accelerated rates of genomic rearrangements and nucleotide substitutions in Poaceae, a phenomenon that has been noted recently throughout angiosperms. The cause of the correlation is unknown, but faulty DNA repair has been suggested in other systems including bacterial and animal mitochondrial genomes.

Phylogenetic and Genomic Analyses Resolve the Origin of Important Plant Genes Derived from Transposable Elements.

PubMed

Joly-Lopez, Zoé; Hoen, Douglas R; Blanchette, Mathieu; Bureau, Thomas E

2016-08-01

Once perceived as merely selfish, transposable elements (TEs) are now recognized as potent agents of adaptation. One way TEs contribute to evolution is through TE exaptation, a process whereby TEs, which persist by replicating in the genome, transform into novel host genes, which persist by conferring phenotypic benefits. Known exapted TEs (ETEs) contribute diverse and vital functions, and may facilitate punctuated equilibrium, yet little is known about this process. To better understand TE exaptation, we designed an approach to resolve the phylogenetic context and timing of exaptation events and subsequent patterns of ETE diversification. Starting with known ETEs, we search in diverse genomes for basal ETEs and closely related TEs, carefully curate the numerous candidate sequences, and infer detailed phylogenies. To distinguish TEs from ETEs, we also weigh several key genomic characteristics including repetitiveness, terminal repeats, pseudogenic features, and conserved domains. Applying this approach to the well-characterized plant ETEs MUG and FHY3, we show that each group is paraphyletic and we argue that this pattern demonstrates that each originated in not one but multiple exaptation events. These exaptations and subsequent ETE diversification occurred throughout angiosperm evolution including the crown group expansion, the angiosperm radiation, and the primitive evolution of angiosperms. In addition, we detect evidence of several putative novel ETE families. Our findings support the hypothesis that TE exaptation generates novel genes more frequently than is currently thought, often coinciding with key periods of evolution. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Evolution of the PEBP gene family in plants: functional diversification in seed plant evolution.

PubMed

Karlgren, Anna; Gyllenstrand, Niclas; Källman, Thomas; Sundström, Jens F; Moore, David; Lascoux, Martin; Lagercrantz, Ulf

2011-08-01

The phosphatidyl ethanolamine-binding protein (PEBP) gene family is present in all eukaryote kingdoms, with three subfamilies identified in angiosperms (FLOWERING LOCUS T [FT], MOTHER OF FT AND TFL1 [MFT], and TERMINAL FLOWER1 [TFL1] like). In angiosperms, PEBP genes have been shown to function both as promoters and suppressors of flowering and to control plant architecture. In this study, we focus on previously uncharacterized PEBP genes from gymnosperms. Extensive database searches suggest that gymnosperms possess only two types of PEBP genes, MFT-like and a group that occupies an intermediate phylogenetic position between the FT-like and TFL1-like (FT/TFL1-like). Overexpression of Picea abies PEBP genes in Arabidopsis (Arabidopsis thaliana) suggests that the FT/TFL1-like genes (PaFTL1 and PaFTL2) code for proteins with a TFL1-like function. However, PaFTL1 and PaFTL2 also show highly divergent expression patterns. While the expression of PaFTL2 is correlated with annual growth rhythm and mainly confined to needles and vegetative and reproductive buds, the expression of PaFTL1 is largely restricted to microsporophylls of male cones. The P. abies MFT-like genes (PaMFT1 and PaMFT2) show a predominant expression during embryo development, a pattern that is also found for many MFT-like genes from angiosperms. P. abies PEBP gene expression is primarily detected in tissues undergoing physiological changes related to growth arrest and dormancy. A first duplication event resulting in two families of plant PEBP genes (MFT-like and FT/TFL1-like) seems to coincide with the evolution of seed plants, in which independent control of bud and seed dormancy was required, and the second duplication resulting in the FT-like and TFL1-like clades probably coincided with the evolution of angiosperms.

Conservation of class C function of floral organ development during 300 million years of evolution from gymnosperms to angiosperms.

PubMed

Zhang, Pingyu; Tan, Hugh T W; Pwee, Keng-Hock; Kumar, Prakash P

2004-02-01

Flower development in angiosperms is regulated by the family of MADS-box transcription factors. MADS-box genes have also been reported from gymnosperms, another major group of seed plants. AGAMOUS (AG) is the class C MADS-box floral organ identity gene controlling the stamen and carpel development in Arabidopsis. We report the characterization of an ortholog of the AG gene, named Cycas AGAMOUS (CyAG), from the primitive gymnosperm Cycas edentata. The expression pattern of CyAG in Cycas parallels that of AG in Arabidopsis. Additionally, the gene structure, including the number and location of the introns, is conserved in CyAG and other AG orthologs known. Most importantly, functional analysis shows that CyAG driven by the AG promoter can rescue the loss-of-function ag mutant of Arabidopsis. However, the ectopic expression of CyAG in ag mutant Arabidopsis cannot produce the carpeloid and stamenoid organs in the first and second whorls, although the stamen and carpel are rescued in the third and fourth whorls of the transformants. These observations show that the molecular mechanism of class C function controlling reproductive organ identity (stamen and carpel of angiosperms or microsporophyll and megasporophyll of gymnosperms) arose before the divergence of angiosperms and gymnosperms, and has been conserved during 300 million years of evolution thereafter.

Fire-adapted Gondwanan Angiosperm floras evolved in the Cretaceous

PubMed Central

2012-01-01

Background Fires have been widespread over the last 250 million years, peaking 60−125 million years ago (Ma), and might therefore have played a key role in the evolution of Angiosperms. Yet it is commonly believed that fireprone communities existed only after the global climate became more arid and seasonal 15 Ma. Recent molecular-based studies point to much earlier origins of fireprone Angiosperm floras in Australia and South Africa (to 60 Ma, Paleocene) but even these were constrained by the ages of the clades examined. Results Using a molecular-dated phylogeny for the great Gondwanan family Proteaceae, with a 113-million-year evolutionary history, we show that the ancestors of many of its characteristic sclerophyll genera, such as Protea, Conospermum, Leucadendron, Petrophile, Adenanthos and Leucospermum (all subfamily Proteoideae), occurred in fireprone habitats from 88 Ma (83−94, 95% HPD, Mid-Upper Cretaceous). This coincided with the highest atmospheric oxygen (combustibility) levels experienced over the past 150 million years. Migration from non-fireprone (essentially rainforest-climate-type) environments was accompanied by the evolution of highly speciose clades with a range of seed storage traits and fire-cued seed release or germination mechanisms that was diagnostic for each clade by 71 Ma, though the ant-dispersed lineage (as a soil seed-storage subclade) was delayed until 45 Ma. Conclusions Focusing on the widespread 113-million-year-old family Proteaceae, fireproneness among Gondwanan Angiosperm floras can now be traced back almost 90 million years into the fiery Cretaceous. The associated evolution of on-plant (serotiny) and soil seed storage, and later ant dispersal, affirms them as ancient adaptations to fire among flowering plants. PMID:23171161

A novel MADS-box gene subfamily with a sister-group relationship to class B floral homeotic genes.

PubMed

Becker, A; Kaufmann, K; Freialdenhoven, A; Vincent, C; Li, M-A; Saedler, H; Theissen, G

2002-02-01

Class B floral homeotic genes specify the identity of petals and stamens during the development of angiosperm flowers. Recently, putative orthologs of these genes have been identified in different gymnosperms. Together, these genes constitute a clade, termed B genes. Here we report that diverse seed plants also contain members of a hitherto unknown sister clade of the B genes, termed B(sister) (B(s)) genes. We have isolated members of the B(s) clade from the gymnosperm Gnetum gnemon, the monocotyledonous angiosperm Zea mays and the eudicots Arabidopsis thaliana and Antirrhinum majus. In addition, MADS-box genes from the basal angiosperm Asarum europaeum and the eudicot Petunia hybrida were identified as B(s) genes. Comprehensive expression studies revealed that B(s) genes are mainly transcribed in female reproductive organs (ovules and carpel walls). This is in clear contrast to the B genes, which are predominantly expressed in male reproductive organs (and in angiosperm petals). Our data suggest that the B(s) genes played an important role during the evolution of the reproductive structures in seed plants. The establishment of distinct B and B(s) gene lineages after duplication of an ancestral gene may have accompanied the evolution of male microsporophylls and female megasporophylls 400-300 million years ago. During flower evolution, expression of B(s) genes diversified, but the focus of expression remained in female reproductive organs. Our findings imply that a clade of highly conserved close relatives of class B floral homeotic genes has been completely overlooked until recently and awaits further evaluation of its developmental and evolutionary importance. Electronic supplementary material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00438-001-0615-8.

Isolation and expression profiles of gibberellin metabolism genes in developing male and female cones of Pinus tabuliformis.

PubMed

Niu, Shihui; Yuan, Lu; Zhang, Yuncheng; Chen, Xiaoyang; Li, Wei

2014-12-01

Gibberellins (GAs) are important in the floral regulatory networks of angiosperm plants. Several lines of evidence suggest that GAs also play a pivotal role in conifer male and female cone development. To gain new insights into the GA metabolism pathway in conifer trees and the role of GA metabolism in male and female cone development, we identified GA metabolism genes in Pinus tabuliformis. These included one PtCPS gene, one PtKS gene, one PtKO gene, TWO PtKAO genes, one PtGA20ox gene, two PtGA3ox genes and 12 PtGA2ox genes. According to phylogenetic analysis, the GA biosynthesis pathway evolved after the divergence of mosses from ferns, but the GA-deactivating gene family underwent divided expansion after divergence of the angiosperms from gymnosperms. However, the active sites of all GA metabolism enzymes were conserved during the evolution of land plants. During male and female cone development of P. tabuliformis, the expression of most of the PtGA2ox genes, especially PtGA2ox10, was higher than GA biosynthesis genes. However, the expression of PtKAO1 in cones peaked at a very early developmental stage. The expression pattern of GA metabolism genes indicated that GAs play different roles at the early and late stages of cone development.

Evolution and genetics of root hair stripes in the root epidermis.

PubMed

Dolan, L; Costa, S

2001-03-01

Root hair pattern develops in a number of different ways in angiosperm. Cells in the epidermis of some species undergo asymmetric cell divisions to form a smaller daughter cell from which a hair grows, and a larger cell that forms a non-hair epidermal cell. In other species any cell in the epidermis can form a root hair. Hair cells are arranged in files along the Arabidopsis root, located in the gaps between underlying cortical cell files. Epidermal cells overlying a single cortical cell file develop as non-hair epidermal cells. Genetic analysis has identified a transcription factor cascade required for the formation of this pattern. WEREWOLF (WER) and GLABRA2 (GL2) are required for the formation of non-hair epidermal cells while CAPRICE (CPC) is required for hair cell development. Recent analyses of the pattern of epidermal cells among the angiosperms indicate that this striped pattern of cell organization evolved from non-striped ancestors independently in a number of diverse evolutionary lineages. The genetic basis for the evolution of epidermal pattern in angiosperms may now be examined.

Gravitropisms and reaction woods of forest trees - evolution, functions and mechanisms.

PubMed

Groover, Andrew

2016-08-01

Contents 790 I. 790 II. 792 III. 795 IV. 797 V. 798 VI. 800 VII. 800 800 References 800 SUMMARY: The woody stems of trees perceive gravity to determine their orientation, and can produce reaction woods to reinforce or change their position. Together, graviperception and reaction woods play fundamental roles in tree architecture, posture control, and reorientation of stems displaced by wind or other environmental forces. Angiosperms and gymnosperms have evolved strikingly different types of reaction wood. Tension wood of angiosperms creates strong tensile force to pull stems upward, while compression wood of gymnosperms creates compressive force to push stems upward. In this review, the general features and evolution of tension wood and compression wood are presented, along with descriptions of how gravitropisms and reaction woods contribute to the survival and morphology of trees. An overview is presented of the molecular and genetic mechanisms underlying graviperception, initial graviresponse and the regulation of tension wood development in the model angiosperm, Populus. Critical research questions and new approaches are discussed. No claim to US Government works New Phytologist © 2016 New Phytologist Trust.

Ontogenetic shifts in plant-plant interactions in a rare cycad within angiosperm communities.

PubMed

Álvarez-Yépiz, Juan C; Búrquez, Alberto; Dovčiak, Martin

2014-06-01

Gymnosperms and angiosperms can co-occur within the same habitats but key plant traits are thought to give angiosperms an evolutionary competitive advantage in many ecological settings. We studied ontogenetic changes in competitive and facilitative interactions between a rare gymnosperm (Dioon sonorense, our target species) and different plant and abiotic neighbours (conspecific-cycads, heterospecific-angiosperms, or abiotic-rocks) from 2007 to 2010 in an arid environment of northwestern Mexico. We monitored survival and growth of seedlings, juveniles, and adults of the cycad Dioon sonorense to evaluate how cycad survival and relative height growth rate (RHGR) responded to intra- and interspecific competition, canopy openness, and nearest neighbour. We tested spatial associations among D. sonorense life stages and angiosperm species and measured ontogenetic shifts in cycad shade tolerance. Canopy openness decreased cycad survival while intraspecific competition decreased survival and RHGR during early ontogeny. Seedling survival was higher in association with rocks and heterospecific neighbours where intraspecific competition was lower. Shade tolerance decreased with cycad ontogeny reflecting the spatial association of advanced stages with more open canopies. Interspecific facilitation during early ontogeny of our target species may promote its persistence in spite of increasing interspecific competition in later stages. We provide empirical support to the long-standing assumption that marginal rocky habitats serve as refugia from angiosperm competition for slow-growing gymnosperms such as cycads. The lack of knowledge of plant-plant interactions in rare or endangered species may hinder developing efficient conservation strategies (e.g. managing for sustained canopy cover), especially under the ongoing land use and climatic changes.

Angiosperm phylogeny inferred from multiple genes as a tool for comparative biology.

PubMed

Soltis, P S; Soltis, D E; Chase, M W

1999-11-25

Comparative biology requires a firm phylogenetic foundation to uncover and understand patterns of diversification and evaluate hypotheses of the processes responsible for these patterns. In the angiosperms, studies of diversification in floral form, stamen organization, reproductive biology, photosynthetic pathway, nitrogen-fixing symbioses and life histories have relied on either explicit or implied phylogenetic trees. Furthermore, to understand the evolution of specific genes and gene families, evaluate the extent of conservation of plant genomes and make proper sense of the huge volume of molecular genetic data available for model organisms such as Arabidopsis, Antirrhinum, maize, rice and wheat, a phylogenetic perspective is necessary. Here we report the results of parsimony analyses of DNA sequences of the plastid genes rbcL and atpB and the nuclear 18S rDNA for 560 species of angiosperms and seven non-flowering seed plants and show a well-resolved and well-supported phylogenetic tree for the angiosperms for use in comparative biology.

Developmental Morphology of the Shoot in Weddellina squamulosa and Implications for Shoot Evolution in the Podostemaceae

PubMed Central

Koi, Satoshi; Kato, Masahiro

2007-01-01

Background and Aims In angiosperms, the shoot apical meristem produces a shoot system composed of stems, leaves and axillary buds. Podostemoideae, one of three subfamilies of the river-weed family Podostemaceae, have a unique ‘shoot’ that lacks a shoot apical meristem and is composed only of leaves. Tristichoideae have been interpreted to have a shoot apical meristem, although its branching pattern is uncertain. The shoot developmental pattern in Weddellinoideae has not been investigated with a focus on the meristem. Weddellinoideae are in a phylogenetically key position to reveal the process of shoot evolution in Podostemaceae. Methods The shoot development of Weddellina squamulosa, the sole species of Weddellinoideae, was investigated using scanning electron microscopy and semi-thin serial sections. Key Results The shoot of W. squamulosa has a tunica–corpus-organized apical meristem. It is determinate and successively initiates a new branch extra-axillarily at the base of an immediately older branch, resulting in a sympodial, approximately plane branching pattern. Large scaly leaves initiate acropetally on the flanks of the apical meristem, as is usual in angiosperms, whereas small scaly leaves scattered on the stem initiate basipetally in association with the elongation of internodes. Conclusions Weddellinoideae, like Tristichoideae, have a shoot apical meristem, leading to the hypothesis that the meristem was lost in Podostemoideae. The patterns of leaf formation in Podostemoideae and shoot branching in Weddellinoideae are similar in that these organs arise at the bases of older organs. This similarity leads to another hypothesis that the ‘branch’ in Weddellinoideae (and possibly Tristichoideae) and the ‘leaf’ in Podostemoideae are comparable, and that the shoot apical meristem disappeared in the early evolution of Podostemaceae. PMID:17468112

Conservation and divergence of plant LHP1 protein sequences and expression patterns in angiosperms and gymnosperms.

PubMed

Guan, Hexin; Zheng, Zhengui; Grey, Paris H; Li, Yuhua; Oppenheimer, David G

2011-05-01

Floral transition is a critical and strictly regulated developmental process in plants. Mutations in Arabidopsis LIKE HETEROCHROMATIN PROTEIN 1 (AtLHP1)/TERMINAL FLOWER 2 (TFL2) result in early and terminal flowers. Little is known about the gene expression, function and evolution of plant LHP1 homologs, except for Arabidopsis LHP1. In this study, the conservation and divergence of plant LHP1 protein sequences was analyzed by sequence alignments and phylogeny. LHP1 expression patterns were compared among taxa that occupy pivotal phylogenetic positions. Several relatively conserved new motifs/regions were identified among LHP1 homologs. Phylogeny of plant LHP1 proteins agreed with established angiosperm relationships. In situ hybridization unveiled conserved expression of plant LHP1 in the axillary bud/tiller, vascular bundles, developing stamens, and carpels. Unlike AtLHP1, cucumber CsLHP1-2, sugarcane SoLHP1 and maize ZmLHP1, rice OsLHP1 is not expressed in the shoot apical meristem (SAM) and the OsLHP1 transcript level is consistently low in shoots. "Unequal crossover" might have contributed to the divergence in the N-terminal and hinge region lengths of LHP1 homologs. We propose an "insertion-deletion" model for soybean (Glycine max L.) GmLHP1s evolution. Plant LHP1 homologs are more conserved than previously expected, and may favor vegetative meristem identity and primordia formation. OsLHP1 may not function in rice SAM during floral induction.

An Evolutionarily Conserved DOF-CONSTANS Module Controls Plant Photoperiodic Signaling.

PubMed

Lucas-Reina, Eva; Romero-Campero, Francisco J; Romero, José M; Valverde, Federico

2015-06-01

The response to daylength is a crucial process that evolved very early in plant evolution, entitling the early green eukaryote to predict seasonal variability and attune its physiological responses to the environment. The photoperiod responses evolved into the complex signaling pathways that govern the angiosperm floral transition today. The Chlamydomonas reinhardtii DNA-Binding with One Finger (CrDOF) gene controls transcription in a photoperiod-dependent manner, and its misexpression influences algal growth and viability. In short days, CrDOF enhances CrCO expression, a homolog of plant CONSTANS (CO), by direct binding to its promoter, while it reduces the expression of cell division genes in long days independently of CrCO. In Arabidopsis (Arabidopsis thaliana), transgenic plants overexpressing CrDOF show floral delay and reduced expression of the photoperiodic genes CO and FLOWERING LOCUS T. The conservation of the DOF-CO module during plant evolution could be an important clue to understanding diversification by the inheritance of conserved gene toolkits in key developmental programs. © 2015 American Society of Plant Biologists. All Rights Reserved.

Highly effective sequencing whole chloroplast genomes of angiosperms by nine novel universal primer pairs.

PubMed

Yang, Jun-Bo; Li, De-Zhu; Li, Hong-Tao

2014-09-01

Chloroplast genomes supply indispensable information that helps improve the phylogenetic resolution and even as organelle-scale barcodes. Next-generation sequencing technologies have helped promote sequencing of complete chloroplast genomes, but compared with the number of angiosperms, relatively few chloroplast genomes have been sequenced. There are two major reasons for the paucity of completely sequenced chloroplast genomes: (i) massive amounts of fresh leaves are needed for chloroplast sequencing and (ii) there are considerable gaps in the sequenced chloroplast genomes of many plants because of the difficulty of isolating high-quality chloroplast DNA, preventing complete chloroplast genomes from being assembled. To overcome these obstacles, all known angiosperm chloroplast genomes available to date were analysed, and then we designed nine universal primer pairs corresponding to the highly conserved regions. Using these primers, angiosperm whole chloroplast genomes can be amplified using long-range PCR and sequenced using next-generation sequencing methods. The primers showed high universality, which was tested using 24 species representing major clades of angiosperms. To validate the functionality of the primers, eight species representing major groups of angiosperms, that is, early-diverging angiosperms, magnoliids, monocots, Saxifragales, fabids, malvids and asterids, were sequenced and assembled their complete chloroplast genomes. In our trials, only 100 mg of fresh leaves was used. The results show that the universal primer set provided an easy, effective and feasible approach for sequencing whole chloroplast genomes in angiosperms. The designed universal primer pairs provide a possibility to accelerate genome-scale data acquisition and will therefore magnify the phylogenetic resolution and species identification in angiosperms. © 2014 John Wiley & Sons Ltd.

Conservative and compensatory evolution in oxidative phosphorylation complexes of angiosperms with highly divergent rates of mitochondrial genome evolution.

PubMed

Havird, Justin C; Whitehill, Nicholas S; Snow, Christopher D; Sloan, Daniel B

2015-12-01

Interactions between nuclear and mitochondrial gene products are critical for eukaryotic cell function. Nuclear genes encoding mitochondrial-targeted proteins (N-mt genes) experience elevated rates of evolution, which has often been interpreted as evidence of nuclear compensation in response to elevated mitochondrial mutation rates. However, N-mt genes may be under relaxed functional constraints, which could also explain observed increases in their evolutionary rate. To disentangle these hypotheses, we examined patterns of sequence and structural evolution in nuclear- and mitochondrial-encoded oxidative phosphorylation proteins from species in the angiosperm genus Silene with vastly different mitochondrial mutation rates. We found correlated increases in N-mt gene evolution in species with fast-evolving mitochondrial DNA. Structural modeling revealed an overrepresentation of N-mt substitutions at positions that directly contact mutated residues in mitochondrial-encoded proteins, despite overall patterns of conservative structural evolution. These findings support the hypothesis that selection for compensatory changes in response to mitochondrial mutations contributes to the elevated rate of evolution in N-mt genes. We discuss these results in light of theories implicating mitochondrial mutation rates and mitonuclear coevolution as drivers of speciation and suggest comparative and experimental approaches that could take advantage of heterogeneity in rates of mtDNA evolution across eukaryotes to evaluate such theories. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica.

PubMed

Barreda, Viviana D; Palazzesi, Luis; Tellería, Maria C; Olivero, Eduardo B; Raine, J Ian; Forest, Félix

2015-09-01

The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76-66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60-50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general.

Hydraulic conductance and the maintenance of water balance in flowers.

PubMed

Roddy, Adam B; Brodersen, Craig R; Dawson, Todd E

2016-10-01

Flowers face desiccating conditions, yet little is known about their ability to transport water. We quantified variability in floral hydraulic conductance (Kflower ) for 20 species from 10 families and related it to traits hypothesized to be associated with liquid and vapour phase water transport. Basal angiosperm flowers had trait values associated with higher water and carbon costs than monocot and eudicot flowers. Kflower was coordinated with water supply (vein length per area, VLA) and loss (minimum epidermal conductance, gmin ) traits among the magnoliids, but was insensitive to variation in these traits among the monocots and eudicots. Phylogenetic independent contrast (PIC) correlations revealed that few traits had undergone coordinated evolution. However, VLA and the desiccation time (Tdes ), the quotient of water content and gmin , had significant trait and PIC correlations. The near absence of stomata from monocot and eudicot flowers may have been critical in minimizing water loss rates among these clades. Early divergent, basal angiosperm flowers maintain higher Kflower because of traits associated with high rates water loss and water supply, while monocot and eudicot flowers employ a more conservative strategy of limiting water loss and may rely on stored water to maintain turgor and delay desiccation. © 2016 John Wiley & Sons Ltd.

An ancestral stomatal patterning module revealed in the non-vascular land plant Physcomitrella patens

PubMed Central

Chater, Caspar C.; Kamisugi, Yasuko

2016-01-01

The patterning of stomata plays a vital role in plant development and has emerged as a paradigm for the role of peptide signals in the spatial control of cellular differentiation. Research in Arabidopsis has identified a series of epidermal patterning factors (EPFs), which interact with an array of membrane-localised receptors and associated proteins (encoded by ERECTA and TMM genes) to control stomatal density and distribution. However, although it is well-established that stomata arose very early in the evolution of land plants, until now it has been unclear whether the established angiosperm stomatal patterning system represented by the EPF/TMM/ERECTA module reflects a conserved, universal mechanism in the plant kingdom. Here, we use molecular genetics to show that the moss Physcomitrella patens has conserved homologues of angiosperm EPF, TMM and at least one ERECTA gene that function together to permit the correct patterning of stomata and that, moreover, elements of the module retain function when transferred to Arabidopsis. Our data characterise the stomatal patterning system in an evolutionarily distinct branch of plants and support the hypothesis that the EPF/TMM/ERECTA module represents an ancient patterning system. PMID:27407102

Evolutionary Analysis of MIKCc-Type MADS-Box Genes in Gymnosperms and Angiosperms

PubMed Central

Chen, Fei; Zhang, Xingtan; Liu, Xing; Zhang, Liangsheng

2017-01-01

MIKCc-type MADS-box genes encode transcription factors that control floral organ morphogenesis and flowering time in flowering plants. Here, in order to determine when the subfamilies of MIKCc originated and their early evolutionary trajectory, we sampled and analyzed the genomes and large-scale transcriptomes representing all the orders of gymnosperms and basal angiosperms. Through phylogenetic inference, the MIKCc-type MADS-box genes were subdivided into 14 monophyletic clades. Among them, the gymnosperm orthologs of AGL6, SEP, AP1, GMADS, SOC1, AGL32, AP3/PI, SVP, AGL15, ANR1, and AG were identified. We identified and characterized the origin of a novel subfamily GMADS within gymnosperms but lost orthologs in monocots and Brassicaceae. ABCE model prototype genes were relatively conserved in terms of gene number in gymnosperms, but expanded in angiosperms, whereas SVP, SOC1, and GMADS had dramatic expansions in gymnosperms but conserved in angiosperms. Our results provided the most detailed evolutionary history of all MIKCc gene clades in gymnosperms and angiosperms. We proposed that although the near complete set of MIKCc genes had evolved in gymnosperms, the duplication and expressional transition of ABCE model MIKCc genes in the ancestor of angiosperms triggered the first flower. PMID:28611810

A brief history of fruits and frugivores

NASA Astrophysics Data System (ADS)

Fleming, Theodore H.; John Kress, W.

2011-11-01

In this paper we briefly review the evolutionary history of the mutualistic interaction between angiosperms that produce fleshy fruits and their major consumers: frugivorous birds and mammals. Fleshy fruits eaten by these vertebrates are widely distributed throughout angiosperm phylogeny. Similarly, a frugivorous diet has evolved independently many times in birds and mammals. Bird dispersal is more common than mammal-dispersal in all lineages of angiosperms, and we suggest that the evolution of bird fruits may have facilitated the evolution of frugivory in primates. The diets of fruit-eating bats overlap less with those of other kinds of frugivorous vertebrates. With a few exceptions, most families producing vertebrate-dispersed fruit appeared substantially earlier in earth history than families of their vertebrate consumers. It is likely that major radiations of these plants and animals have occurred in the past 30 Ma, in part driven by geological changes and also by the foraging behavior of frugivores in topographically complex landscapes. Overall, this mutualistic interaction has had many evolutionary and ecological consequences for tropical plants and animals for most of the Cenozoic Era. Loss of frugivores and their dispersal services will have a strong negative impact on the ecological and evolutionary dynamics of tropical and subtropical communities.

The naked and the dead: the ABCs of gymnosperm reproduction and the origin of the angiosperm flower.

PubMed

Melzer, Rainer; Wang, Yong-Qiang; Theissen, Günter

2010-02-01

20 years after establishment of the ABC model many of the molecular mechanisms underlying development of the angiosperm flower are relatively well understood. Central players in the gene regulatory network controlling flower development are SQUA-like, DEF/GLO-like, AG-like and AGL6/SEP1-like MIKC-type MADS-domain transcription factors. These provide class A, class B, class C and the more recently defined class E floral homeotic functions, respectively. There is evidence that the floral homeotic proteins recognize the DNA of target genes in an organ-specific way as multimeric protein complexes, thus constituting 'floral quartets'. In contrast to the detailed insights into flower development, how the flower originated during evolution has remained enigmatic. However, while orthologues of all classes of floral homeotic genes appear to be absent from all non-seed plants, DEF/GLO-like, AG-like, and AGL6-like genes have been found in diverse extant gymnosperms, the closest relatives of the angiosperms. While SQUA-like and SEP1-like MADS-box genes appear to be absent from extant gymnosperms, reconstruction of MADS-box gene phylogeny surprisingly suggests that the most recent common ancestor of gymnosperms and angiosperms possessed representatives of both genes, but that these have been lost in the lineage that led to extant gymnosperms. Expression studies and genetic complementation experiments indicate that both angiosperm and gymnosperm AG-like and DEF/GLO-like genes have conserved functions in the specification of reproductive organs and in distinguishing male from female organs, respectively. Based on these findings novel models about the molecular basis of flower origin, involving changes in the expression patterns of DEF/GLO-like or AGL6/SEP1/SQUA-like genes in reproductive structures, were developed. While in angiosperms SEP1-like proteins play an important role in floral quartet formation, preliminary evidence suggests that gymnosperm DEF/GLO-like and AG-like proteins alone can already form floral quartet-like complexes, further corroborating the view that the formation of floral quartet-like complexes predated flower origin during evolution. Copyright 2009 Elsevier Ltd. All rights reserved.

Contextualising primate origins--an ecomorphological framework.

PubMed

Soligo, Christophe; Smaers, Jeroen B

2016-04-01

Ecomorphology - the characterisation of the adaptive relationship between an organism's morphology and its ecological role - has long been central to theories of the origin and early evolution of the primate order. This is exemplified by two of the most influential theories of primate origins: Matt Cartmill's Visual Predation Hypothesis, and Bob Sussman's Angiosperm Co-Evolution Hypothesis. However, the study of primate origins is constrained by the absence of data directly documenting the events under investigation, and has to rely instead on a fragmentary fossil record and the methodological assumptions inherent in phylogenetic comparative analyses of extant species. These constraints introduce particular challenges for inferring the ecomorphology of primate origins, as morphology and environmental context must first be inferred before the relationship between the two can be considered. Fossils can be integrated in comparative analyses and observations of extant model species and laboratory experiments of form-function relationships are critical for the functional interpretation of the morphology of extinct species. Recent developments have led to important advancements, including phylogenetic comparative methods based on more realistic models of evolution, and improved methods for the inference of clade divergence times, as well as an improved fossil record. This contribution will review current perspectives on the origin and early evolution of primates, paying particular attention to their phylogenetic (including cladistic relationships and character evolution) and environmental (including chronology, geography, and physical environments) contextualisation, before attempting an up-to-date ecomorphological synthesis of primate origins. © 2016 Anatomical Society.

The emergence of modern type rain forests and mangroves and their traces in the palaeobotanical record during the Late Cretaceous and early Tertiary

NASA Astrophysics Data System (ADS)

Mohr, Barbara; Coiffard, Clément

2014-05-01

The origin of modern rain forests is still very poorly known. This ecosystem could have potentially fully evolved only after the development of relatively high numbers of flowering plant families adapted to rain forest conditions. During the early phase of angiosperm evolution in the early Cretaceous the palaeo-equatorial region was located in a seasonally dry climatic belt, so that during this phase, flowering plants often show adaptations to drought, rather than to continuously wet climate conditions. Therefore it is not surprising that except for the Nymphaeales, the most basal members of extant angiosperm families have members that do not necessarily occur in the continuously wet tropics today. However, during the late Early Cretaceous several clades emerged that later would give rise to families that are typically found today mostly in (shady) moist places in warmer regions. This is especially seen among the monocotyledons, a group of the mesangiosperms, that developed in many cases large leaves often with very specific venation patterns that make these leaves very unique and well recognizable. Especially members of three groups are here of interest: the arum family (Araceae), the palms (Arecaceae) and the Ginger and allies (Zingiberales). The earliest fossil of Araceae are restricted to low latitudes during the lower Cretaceous. Arecaceae and Zingiberales do not appear in the fossil record before the early late Cretaceous and occur at mid latitudes. During the Late Cretaceous, Araceae are represented at mid latitudes by non-tropical early diverging members and at low latitudes by derived rainforest members. Palms became widespread during the Late Cretataceous and also Nypa, a typical element of tropical to subtropical mangrove environments evolved during this time period. During the Paleocene Arecaceae appear to be restricted to lower latitudes as well as Zingiberales. All three groups are again widespread during the Eocene, reaching higher latitudes and probably diversifying at mid latitudes. Later on, they slowly became restricted to lower latitudes as seen today. This fluctuation appears to be linked to climate change and are still reflected by the regional diversity of these groups, which reflect rather well rain forest evolution. When tracing the fossil record of rain forest plants we clearly see a pattern that suggests the onset of this type of environment during the late Late Cretaceous and spread during the early Tertiary with phases of retreat during the Oligocene and from the mid-Miocene onwards.

Complete sequences of organelle genomes from the medicinal plant Rhazya stricta (Apocynaceae) and contrasting patterns of mitochondrial genome evolution across asterids.

PubMed

Park, Seongjun; Ruhlman, Tracey A; Sabir, Jamal S M; Mutwakil, Mohammed H Z; Baeshen, Mohammed N; Sabir, Meshaal J; Baeshen, Nabih A; Jansen, Robert K

2014-05-28

Rhazya stricta is native to arid regions in South Asia and the Middle East and is used extensively in folk medicine to treat a wide range of diseases. In addition to generating genomic resources for this medicinally important plant, analyses of the complete plastid and mitochondrial genomes and a nuclear transcriptome from Rhazya provide insights into inter-compartmental transfers between genomes and the patterns of evolution among eight asterid mitochondrial genomes. The 154,841 bp plastid genome is highly conserved with gene content and order identical to the ancestral organization of angiosperms. The 548,608 bp mitochondrial genome exhibits a number of phenomena including the presence of recombinogenic repeats that generate a multipartite organization, transferred DNA from the plastid and nuclear genomes, and bidirectional DNA transfers between the mitochondrion and the nucleus. The mitochondrial genes sdh3 and rps14 have been transferred to the nucleus and have acquired targeting presequences. In the case of rps14, two copies are present in the nucleus; only one has a mitochondrial targeting presequence and may be functional. Phylogenetic analyses of both nuclear and mitochondrial copies of rps14 across angiosperms suggests Rhazya has experienced a single transfer of this gene to the nucleus, followed by a duplication event. Furthermore, the phylogenetic distribution of gene losses and the high level of sequence divergence in targeting presequences suggest multiple, independent transfers of both sdh3 and rps14 across asterids. Comparative analyses of mitochondrial genomes of eight sequenced asterids indicates a complicated evolutionary history in this large angiosperm clade with considerable diversity in genome organization and size, repeat, gene and intron content, and amount of foreign DNA from the plastid and nuclear genomes. Organelle genomes of Rhazya stricta provide valuable information for improving the understanding of mitochondrial genome evolution among angiosperms. The genomic data have enabled a rigorous examination of the gene transfer events. Rhazya is unique among the eight sequenced asterids in the types of events that have shaped the evolution of its mitochondrial genome. Furthermore, the organelle genomes of R. stricta provide valuable genomic resources for utilizing this important medicinal plant in biotechnology applications.

Experimental insights into angiosperm origins.

NASA Astrophysics Data System (ADS)

Lomax, Barry; Lee, Alex; Smilie, Ian; Knight, Charles; Upchurch, Garland

2017-04-01

The angiosperms occupy almost every habitat type on Earth and comprise nearly 90% of extant plant species. Yet this ascendency is a relatively recent (geological) phenomenon. Palaeobotanical evidence indicates a likely first occurrence in the Early Cretaceous followed by a relatively rapid increase in diversity with their rise to dominance marking the onset of modern world. Understanding this diversification event has been a key research question since Darwin commented on this "abominable mystery", and it remains one of the most significant unanswered questions in plant biology. Sequencing work shows that the diversification and radiation was accompanied by successive whole genome duplication (WGD) events. Furthermore proxy data and predictions from long-term carbon cycle models indicate that the angiosperm diversification was accompanied by a decline in atmospheric CO2. These observation raise the intriguing possibility that declining atmospheric CO2 concentration and capacity to undergo polyploidy could have given angiosperms a competitive advantage when compared to other plant groups. Using comparative ecophysiology we set out to test the effects of declining atmospheric CO2 by growing a six species (Ranunculus acris and Polypodium vulgare, chosen to represent Cretaceous understorey angiosperms and pteridophytes respectively. Liquidambar styraciflua and Laurus nobilis represented canopy angiosperms and Ginkgo biloba and Metasequoia glyptostroboides canopy gymnosperms) in controlled conditions across a CO2 gradient (2000, 1200, 800 and 400 ppm) to simulate Cretaceous CO2decline. To test for WGDs we use the relationship between guard cell size and genome size to reconstruct angiosperm genome size as they radiated. Analysis of our fossil dataset shows that earliest angiosperms had a small genome size. Our experimental work shows that angiosperms have a greater capacity for acclimation suggesting that declining CO2 could have acted as a trigger for the angiosperm rise to dominance. When viewed collectively our data indicate that within angiosperms there is a close coupling of genome size to physiological and reproductive processes that is absent in other plant groups. Consequently the ability of angiosperms to alter key processes as genome size changes might explain a proportion of Darwin's "abominable mystery". More broadly, these data highlight the benefits of developing approaches that allow the integration of palaeobotanical observation with experimental data.

Seed size and its rate of evolution correlate with species diversification across angiosperms

PubMed Central

Miller, Eleanor F.; Papadopulos, Alexander S. T.; Tanentzap, Andrew J.

2017-01-01

Species diversity varies greatly across the different taxonomic groups that comprise the Tree of Life (ToL). This imbalance is particularly conspicuous within angiosperms, but is largely unexplained. Seed mass is one trait that may help clarify why some lineages diversify more than others because it confers adaptation to different environments, which can subsequently influence speciation and extinction. The rate at which seed mass changes across the angiosperm phylogeny may also be linked to diversification by increasing reproductive isolation and allowing access to novel ecological niches. However, the magnitude and direction of the association between seed mass and diversification has not been assessed across the angiosperm phylogeny. Here, we show that absolute seed size and the rate of change in seed size are both associated with variation in diversification rates. Based on the largest available angiosperm phylogenetic tree, we found that smaller-seeded plants had higher rates of diversification, possibly due to improved colonisation potential. The rate of phenotypic change in seed size was also strongly positively correlated with speciation rates, providing rare, large-scale evidence that rapid morphological change is associated with species divergence. Our study now reveals that variation in morphological traits and, importantly, the rate at which they evolve can contribute to explaining the extremely uneven distribution of diversity across the ToL. PMID:28723902

A spruce gene map infers ancient plant genome reshuffling and subsequent slow evolution in the gymnosperm lineage leading to extant conifers

PubMed Central

2012-01-01

Background Seed plants are composed of angiosperms and gymnosperms, which diverged from each other around 300 million years ago. While much light has been shed on the mechanisms and rate of genome evolution in flowering plants, such knowledge remains conspicuously meagre for the gymnosperms. Conifers are key representatives of gymnosperms and the sheer size of their genomes represents a significant challenge for characterization, sequencing and assembling. Results To gain insight into the macro-organisation and long-term evolution of the conifer genome, we developed a genetic map involving 1,801 spruce genes. We designed a statistical approach based on kernel density estimation to analyse gene density and identified seven gene-rich isochors. Groups of co-localizing genes were also found that were transcriptionally co-regulated, indicative of functional clusters. Phylogenetic analyses of 157 gene families for which at least two duplicates were mapped on the spruce genome indicated that ancient gene duplicates shared by angiosperms and gymnosperms outnumbered conifer-specific duplicates by a ratio of eight to one. Ancient duplicates were much more translocated within and among spruce chromosomes than conifer-specific duplicates, which were mostly organised in tandem arrays. Both high synteny and collinearity were also observed between the genomes of spruce and pine, two conifers that diverged more than 100 million years ago. Conclusions Taken together, these results indicate that much genomic evolution has occurred in the seed plant lineage before the split between gymnosperms and angiosperms, and that the pace of evolution of the genome macro-structure has been much slower in the gymnosperm lineage leading to extent conifers than that seen for the same period of time in flowering plants. This trend is largely congruent with the contrasted rates of diversification and morphological evolution observed between these two groups of seed plants. PMID:23102090

A spruce gene map infers ancient plant genome reshuffling and subsequent slow evolution in the gymnosperm lineage leading to extant conifers.

PubMed

Pavy, Nathalie; Pelgas, Betty; Laroche, Jérôme; Rigault, Philippe; Isabel, Nathalie; Bousquet, Jean

2012-10-26

Seed plants are composed of angiosperms and gymnosperms, which diverged from each other around 300 million years ago. While much light has been shed on the mechanisms and rate of genome evolution in flowering plants, such knowledge remains conspicuously meagre for the gymnosperms. Conifers are key representatives of gymnosperms and the sheer size of their genomes represents a significant challenge for characterization, sequencing and assembling. To gain insight into the macro-organisation and long-term evolution of the conifer genome, we developed a genetic map involving 1,801 spruce genes. We designed a statistical approach based on kernel density estimation to analyse gene density and identified seven gene-rich isochors. Groups of co-localizing genes were also found that were transcriptionally co-regulated, indicative of functional clusters. Phylogenetic analyses of 157 gene families for which at least two duplicates were mapped on the spruce genome indicated that ancient gene duplicates shared by angiosperms and gymnosperms outnumbered conifer-specific duplicates by a ratio of eight to one. Ancient duplicates were much more translocated within and among spruce chromosomes than conifer-specific duplicates, which were mostly organised in tandem arrays. Both high synteny and collinearity were also observed between the genomes of spruce and pine, two conifers that diverged more than 100 million years ago. Taken together, these results indicate that much genomic evolution has occurred in the seed plant lineage before the split between gymnosperms and angiosperms, and that the pace of evolution of the genome macro-structure has been much slower in the gymnosperm lineage leading to extent conifers than that seen for the same period of time in flowering plants. This trend is largely congruent with the contrasted rates of diversification and morphological evolution observed between these two groups of seed plants.

Evolution of the bHLH Genes Involved in Stomatal Development: Implications for the Expansion of Developmental Complexity of Stomata in Land Plants

PubMed Central

Ran, Jin-Hua; Shen, Ting-Ting; Liu, Wen-Juan; Wang, Xiao-Quan

2013-01-01

Stomata play significant roles in plant evolution. A trio of closely related basic Helix-Loop-Helix (bHLH) subgroup Ia genes, SPCH, MUTE and FAMA, mediate sequential steps of stomatal development, and their functions may be conserved in land plants. However, the evolutionary history of the putative SPCH/MUTE/FAMA genes is still greatly controversial, especially the phylogenetic positions of the bHLH Ia members from basal land plants. To better understand the evolutionary pattern and functional diversity of the bHLH genes involved in stomatal development, we made a comprehensive evolutionary analysis of the homologous genes from 54 species representing the major lineages of green plants. The phylogenetic analysis indicated: (1) All bHLH Ia genes from the two basal land plants Physcomitrella and Selaginella were closely related to the FAMA genes of seed plants; and (2) the gymnosperm ‘SPCH’ genes were sister to a clade comprising the angiosperm SPCH and MUTE genes, while the FAMA genes of gymnosperms and angiosperms had a sister relationship. The revealed phylogenetic relationships are also supported by the distribution of gene structures and previous functional studies. Therefore, we deduce that the function of FAMA might be ancestral in the bHLH Ia subgroup. In addition, the gymnosperm “SPCH” genes may represent an ancestral state and have a dual function of SPCH and MUTE, two genes that could have originated from a duplication event in the common ancestor of angiosperms. Moreover, in angiosperms, SPCHs have experienced more duplications and harbor more copies than MUTEs and FAMAs, which, together with variation of the stomatal development in the entry division, implies that SPCH might have contributed greatly to the diversity of stomatal development. Based on the above, we proposed a model for the correlation between the evolution of stomatal development and the genes involved in this developmental process in land plants. PMID:24244399

Conservation of the abscission signaling peptide IDA during Angiosperm evolution: withstanding genome duplications and gain and loss of the receptors HAE/HSL2

PubMed Central

Stø, Ida M.; Orr, Russell J. S.; Fooyontphanich, Kim; Jin, Xu; Knutsen, Jonfinn M. B.; Fischer, Urs; Tranbarger, Timothy J.; Nordal, Inger; Aalen, Reidunn B.

2015-01-01

The peptide INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), which signals through the leucine-rich repeat receptor-like kinases HAESA (HAE) and HAESA-LIKE2 (HSL2), controls different cell separation events in Arabidopsis thaliana. We hypothesize the involvement of this signaling module in abscission processes in other plant species even though they may shed other organs than A. thaliana. As the first step toward testing this hypothesis from an evolutionarily perspective we have identified genes encoding putative orthologs of IDA and its receptors by BLAST searches of publically available protein, nucleotide and genome databases for angiosperms. Genes encoding IDA or IDA-LIKE (IDL) peptides and HSL proteins were found in all investigated species, which were selected as to represent each angiosperm order with available genomic sequences. The 12 amino acids representing the bioactive peptide in A. thaliana have virtually been unchanged throughout the evolution of the angiosperms; however, the number of IDL and HSL genes varies between different orders and species. The phylogenetic analyses suggest that IDA, HSL2, and the related HSL1 gene, were present in the species that gave rise to the angiosperms. HAE has arisen from HSL1 after a genome duplication that took place after the monocot—eudicots split. HSL1 has also independently been duplicated in the monocots, while HSL2 has been lost in gingers (Zingiberales) and grasses (Poales). IDA has been duplicated in eudicots to give rise to functionally divergent IDL peptides. We postulate that the high number of IDL homologs present in the core eudicots is a result of multiple whole genome duplications (WGD). We substantiate the involvement of IDA and HAE/HSL2 homologs in abscission by providing gene expression data of different organ separation events from various species. PMID:26579174

Evolution of tonoplast P-ATPase transporters involved in vacuolar acidification.

PubMed

Li, Yanbang; Provenzano, Sofia; Bliek, Mattijs; Spelt, Cornelis; Appelhagen, Ingo; Machado de Faria, Laura; Verweij, Walter; Schubert, Andrea; Sagasser, Martin; Seidel, Thorsten; Weisshaar, Bernd; Koes, Ronald; Quattrocchio, Francesca

2016-08-01

Petunia mutants (Petunia hybrida) with blue flowers defined a novel vacuolar proton pump consisting of two interacting P-ATPases, PH1 and PH5, that hyper-acidify the vacuoles of petal cells. PH5 is similar to plasma membrane H(+) P3A -ATPase, whereas PH1 is the only known eukaryoticP3B -ATPase. As there were no indications that this tonoplast pump is widespread in plants, we investigated the distribution and evolution of PH1 and PH5. We combined database mining and phylogenetic and synteny analyses of PH1- and PH5-like proteins from all kingdoms with functional analyses (mutant complementation and intracellular localization) of homologs from diverse angiosperms. We identified functional PH1 and PH5 homologs in divergent angiosperms. PH5 homologs evolved from plasma membrane P3A -ATPases, acquiring an N-terminal tonoplast-sorting sequence and new cellular function before angiosperms appeared. PH1 is widespread among seed plants and related proteins are found in some groups of bacteria and fungi and in one moss, but is absent in most algae, suggesting that its evolution involved several cases of gene loss and possibly horizontal transfer events. The distribution of PH1 and PH5 in the plant kingdom suggests that vacuolar acidification by P-ATPases appeared in gymnosperms before flowers. This implies that, next to flower color determination, vacuolar hyper-acidification is required for yet unknown processes. © 2016 European Union. New Phytologist © 2016 New Phytologist Trust.

Plants, Weathering, and the Evolution of Atmospheric Carbon Dioxide and Oxygen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berner, Robert A

Over the past six years we have published 24 papers that can be divided into three sections: (1) Study of plants and weathering, (2) modeling the evolution of atmospheric CO2 over Phanerozoic time (past 550 million years). (3) Modeling of atmospheric O2 over Phanerozoic time. References to papers published acknowledging this grant can be found at the end of this report and almost all are supplied in pdf form. (1) In the temperate forests of the Cascade Mountains, USA, calcium and magnesium meet vastly different fates beneath angiosperms vs gymnosperms. Calcium is leached beneath both groves of trees, but leachedmore » 20-40% more beneath the angiosperms. Magnesium is retained in the forest system beneath the angiosperms and leached from beneath the gymnosperms. (2) We have shown that climate and CO2, based on both carbon cycle modeling and hundreds of independent proxies for paleo-CO2, correlate very well over the past 550 million year. In a recent paper we use this correlation to deduce the sensitivity of global mean temperature to a doubling of atmospheric CO2, and results are in excellent agreement with the results of climatologists based on the historical record and on theoretical climate models (GCM’s).(3) We have shown that concentrations of atmospheric oxygen, calculated by a combined carbon-sulfur cycle model, over the past 550 million years have varied with and influenced biological evolution.« less

Evolutionary Analysis of MIKCc-Type MADS-Box Genes in Gymnosperms and Angiosperms.

PubMed

Chen, Fei; Zhang, Xingtan; Liu, Xing; Zhang, Liangsheng

2017-01-01

MIKC c -type MADS-box genes encode transcription factors that control floral organ morphogenesis and flowering time in flowering plants. Here, in order to determine when the subfamilies of MIKC c originated and their early evolutionary trajectory, we sampled and analyzed the genomes and large-scale transcriptomes representing all the orders of gymnosperms and basal angiosperms. Through phylogenetic inference, the MIKC c -type MADS-box genes were subdivided into 14 monophyletic clades. Among them, the gymnosperm orthologs of AGL6, SEP , AP1 , GMADS , SOC1 , AGL32 , AP3 / PI , SVP , AGL15 , ANR1 , and AG were identified. We identified and characterized the origin of a novel subfamily GMADS within gymnosperms but lost orthologs in monocots and Brassicaceae. ABCE model prototype genes were relatively conserved in terms of gene number in gymnosperms, but expanded in angiosperms, whereas SVP , SOC1 , and GMADS had dramatic expansions in gymnosperms but conserved in angiosperms. Our results provided the most detailed evolutionary history of all MIKC c gene clades in gymnosperms and angiosperms. We proposed that although the near complete set of MIKC c genes had evolved in gymnosperms, the duplication and expressional transition of ABCE model MIKC c genes in the ancestor of angiosperms triggered the first flower.

Pollination biology of basal angiosperms (ANITA Grade)

Treesearch

Leonard B. Thien; Peter Bernhardt; Margaret S. Devall; Zhi-Duan Chen; Yi-bo Luo; Jian-Hua Fan; Liang-Chen Yuan; Joseph H. Williams

2009-01-01

The fi rst three branches of the angiosperm phylogenetic tree consist of eight families with ~201 species of plants (the ANITA grade). The oldest fl ower fossil for the group is dated to the Early Cretaceous (115 – 125 Mya) and identifi ed to the Nymphaeales. The fl owers of extant plants in the ANITA grade are small, and pollen is the edible reward (rarely nectar or...

Identification and Functional Characterization of Monofunctional ent-Copalyl Diphosphate and ent-Kaurene Synthases in White Spruce Reveal Different Patterns for Diterpene Synthase Evolution for Primary and Secondary Metabolism in Gymnosperms1[W][OA

PubMed Central

Keeling, Christopher I.; Dullat, Harpreet K.; Yuen, Mack; Ralph, Steven G.; Jancsik, Sharon; Bohlmann, Jörg

2010-01-01

The biosynthesis of the tetracyclic diterpene ent-kaurene is a critical step in the general (primary) metabolism of gibberellin hormones. ent-Kaurene is formed by a two-step cyclization of geranylgeranyl diphosphate via the intermediate ent-copalyl diphosphate. In a lower land plant, the moss Physcomitrella patens, a single bifunctional diterpene synthase (diTPS) catalyzes both steps. In contrast, in angiosperms, the two consecutive cyclizations are catalyzed by two distinct monofunctional enzymes, ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase (KS). The enzyme, or enzymes, responsible for ent-kaurene biosynthesis in gymnosperms has been elusive. However, several bifunctional diTPS of specialized (secondary) metabolism have previously been characterized in gymnosperms, and all known diTPSs for resin acid biosynthesis in conifers are bifunctional. To further understand the evolution of ent-kaurene biosynthesis as well as the evolution of general and specialized diterpenoid metabolisms in gymnosperms, we set out to determine whether conifers use a single bifunctional diTPS or two monofunctional diTPSs in the ent-kaurene pathway. Using a combination of expressed sequence tag, full-length cDNA, genomic DNA, and targeted bacterial artificial chromosome sequencing, we identified two candidate CPS and KS genes from white spruce (Picea glauca) and their orthologs in Sitka spruce (Picea sitchensis). Functional characterization of the recombinant enzymes established that ent-kaurene biosynthesis in white spruce is catalyzed by two monofunctional diTPSs, PgCPS and PgKS. Comparative analysis of gene structures and enzyme functions highlights the molecular evolution of these diTPSs as conserved between gymnosperms and angiosperms. In contrast, diTPSs for specialized metabolism have evolved differently in angiosperms and gymnosperms. PMID:20044448

RAPID EVOLUTION CAUSED BY POLLINATOR LOSS IN MIMULUS GUTTATUS

PubMed Central

Bodbyl Roels, Sarah A.; Kelly, John K.

2018-01-01

Anthropogenic perturbations including habitat loss and emerging disease are changing pollinator communities and generating novel selection pressures on plant populations. Disruption of plant–pollinator relationships is predicted to cause plant mating system evolution, although this process has not been directly observed. This study demonstrates the immediate evolutionary effects of pollinator loss within experimental populations of a predominately outcrossing wildflower. Initially equivalent populations evolved for five generations within two pollination treatments: abundant bumblebee pollinators versus no pollinators. The populations without pollinators suffered greatly reduced fitness in early generations but rebounded as they evolved an improved ability to self-fertilize. All populations diverged in floral, developmental, and life-history traits, but only a subset of characters showed clear association with pollination treatment. Pronounced treatment effects were noted for anther–stigma separation and autogamous seed set. Dramatic allele frequency changes at two chromosomal polymorphisms occurred in the no pollinator populations, explaining a large fraction of divergence in pollen viability. The pattern of phenotypic and genetic changes in this experiment favors a sequential model for the evolution of the multitrait “selfing syndrome” observed throughout angiosperms. PMID:21884055

Rapid evolution caused by pollinator loss in Mimulus guttatus.

PubMed

Roels, Sarah A Bodbyl; Kelly, John K

2011-09-01

Anthropogenic perturbations including habitat loss and emerging disease are changing pollinator communities and generating novel selection pressures on plant populations. Disruption of plant-pollinator relationships is predicted to cause plant mating system evolution, although this process has not been directly observed. This study demonstrates the immediate evolutionary effects of pollinator loss within experimental populations of a predominately outcrossing wildflower. Initially equivalent populations evolved for five generations within two pollination treatments: abundant bumblebee pollinators versus no pollinators. The populations without pollinators suffered greatly reduced fitness in early generations but rebounded as they evolved an improved ability to self-fertilize. All populations diverged in floral, developmental, and life-history traits, but only a subset of characters showed clear association with pollination treatment. Pronounced treatment effects were noted for anther-stigma separation and autogamous seed set. Dramatic allele frequency changes at two chromosomal polymorphisms occurred in the no pollinator populations, explaining a large fraction of divergence in pollen viability. The pattern of phenotypic and genetic changes in this experiment favors a sequential model for the evolution of the multitrait "selfing syndrome" observed throughout angiosperms. © 2011 The Author(s).

High-precision 40Ar/39Ar age for the Jehol Biota

NASA Astrophysics Data System (ADS)

Chang, S.; Zhang, H.; Renne, P. R.; Fang, Y.

2008-12-01

Abundant fossils of the terrestrial Jehol Biota, including plants, insects, dinosaurs, birds, mammals and freshwater invertebrates, were discovered from the Yixian Formation and the overlying Jiufotang Formation in Inner Mongolia, Hebei Province and Liaoning Province, northeastern China. Because of the exceptional preservation of fossils, the Jehol Biota is one of the most important Mesozoic fossil outcrops and referred to as a "Mesozoic Pompeii". The Jehol Biota has provided a rare opportunity to address questions about the origin of birds, the evolution of feathers and flight, the early diversification of angiosperms and the timing of the radiation of placental mammals. The Tuchengzi Formation, which lies unconformably just below the Yixian Formation and consists mainly of variegated sandstones, is less fossiliferous than the two overlying formations. However, dinosaur tracks, silicified wood and compressed plants are found in this formation. A systematic 40Ar/39Ar dating of the Yixian and the Jiufotang formations was undertaken to provide a framework for understanding the timing and duration of the Jehol Biota and evolutionary events represented within it. Furthermore, determining the absolute age of the Tuchengzi Formation provides information to interpret abundant dinosaur tracks within and provide better age constrains for the beginning of the Jehol Biota. Here we present robust high-precision 40Ar/39Ar data for six tuff samples and two basalt samples collected from the Tuchengzi, the Yixian and the Jiufotang formations near the classic outcrops in western Liaoning, NE China. We obtain an age of 139.5 ± 1.0 Ma for the uppermost Tuchengzi Formation, an age of 129.7 ± 0.5 Ma for a basaltic lava from the bottom of the Yixian Formation and an age of 122.1 ± 0.3 Ma for a tuff from the base of the overlying Jiufotang Formation. Our data indicate that the Yixian Formation was deposited during the Early Cretaceous, the Barremian to early Aptian, within a time span of 7 Ma. Because of the systematic sampling and the high quality of our data, these results contribute the most accurate age calibration yet of the Jehol Biota within the Yixian Formation and the overlying Jiufotang Formation, providing significant calibration for the evolution of early angiosperms, primitive birds and feathered dinosaurs.

Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica

PubMed Central

Barreda, Viviana D.; Palazzesi, Luis; Tellería, Maria C.; Olivero, Eduardo B.; Raine, J. Ian; Forest, Félix

2015-01-01

The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76–66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60–50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general. PMID:26261324

A Transcriptome Atlas of Physcomitrella patens Provides Insights into the Evolution and Development of Land Plants.

PubMed

Ortiz-Ramírez, Carlos; Hernandez-Coronado, Marcela; Thamm, Anna; Catarino, Bruno; Wang, Mingyi; Dolan, Liam; Feijó, José A; Becker, Jörg D

2016-02-01

Identifying the genetic mechanisms that underpin the evolution of new organ and tissue systems is an aim of evolutionary developmental biology. Comparative functional genetic studies between angiosperms and bryophytes can define those genetic changes that were responsible for developmental innovations. Here, we report the generation of a transcriptome atlas covering most phases in the life cycle of the model bryophyte Physcomitrella patens, including detailed sporophyte developmental progression. We identified a comprehensive set of sporophyte-specific transcription factors, and found that many of these genes have homologs in angiosperms that function in developmental processes such as flowering and shoot branching. Deletion of the PpTCP5 transcription factor results in development of supernumerary sporangia attached to a single seta, suggesting that it negatively regulates branching in the moss sporophyte. Given that TCP genes repress branching in angiosperms, we suggest that this activity is ancient. Finally, comparison of P. patens and Arabidopsis thaliana transcriptomes led us to the identification of a conserved core of transcription factors expressed in tip-growing cells. We identified modifications in the expression patterns of these genes that could account for developmental differences between P. patens tip-growing cells and A. thaliana pollen tubes and root hairs. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

The evolution of floral scent and insect chemical communication.

PubMed

Schiestl, Florian P

2010-05-01

Plants have evolved a range of strategies to manipulate the behaviour of their insect partners. One powerful strategy is to produce signals that already have a role in the animals' own communication systems. To investigate to what extent the evolution of floral scents is correlated with chemical communication in insects, I analyse the occurrence, commonness, and evolutionary patterns of the 71 most common 'floral' volatile organic compounds (VOCs) in 96 plant families and 87 insect families. I found an overlap of 87% in VOCs produced by plants and insects. 'Floral' monoterpenes showed strong positive correlation in commonness between plants (both gymnosperms and angiosperms) and herbivores, whereas the commonness of 'floral' aromatics was positively correlated between angiosperms and both pollinators and herbivores. According to a multivariate regression analysis the commonness of 'floral' aromatics was best explained by their commonness in pollinators, whereas monoterpenes were best explained by herbivores. Among pollinator orders, aromatics were significantly more common in Lepidoptera than in Hymenoptera, whereas monoterpenes showed no difference among the two orders. Collectively, these patterns suggest that plants and insects converge in overall patterns of volatile production, both for attraction and defence. Monoterpenes seem to have evolved primarily for defence under selection by herbivores, whereas aromatics evolved signalling functions in angiosperms, primarily for pollinator attraction.

Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering.

PubMed

Quirk, Joe; Beerling, David J; Banwart, Steve A; Kakonyi, Gabriella; Romero-Gonzalez, Maria E; Leake, Jonathan R

2012-12-23

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to 'trenching' of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO(2) and climate history.

Comparative genomics reveals conservative evolution of the xylem transcriptome in vascular plants.

PubMed

Li, Xinguo; Wu, Harry X; Southerton, Simon G

2010-06-21

Wood is a valuable natural resource and a major carbon sink. Wood formation is an important developmental process in vascular plants which played a crucial role in plant evolution. Although genes involved in xylem formation have been investigated, the molecular mechanisms of xylem evolution are not well understood. We use comparative genomics to examine evolution of the xylem transcriptome to gain insights into xylem evolution. The xylem transcriptome is highly conserved in conifers, but considerably divergent in angiosperms. The functional domains of genes in the xylem transcriptome are moderately to highly conserved in vascular plants, suggesting the existence of a common ancestral xylem transcriptome. Compared to the total transcriptome derived from a range of tissues, the xylem transcriptome is relatively conserved in vascular plants. Of the xylem transcriptome, cell wall genes, ancestral xylem genes, known proteins and transcription factors are relatively more conserved in vascular plants. A total of 527 putative xylem orthologs were identified, which are unevenly distributed across the Arabidopsis chromosomes with eight hot spots observed. Phylogenetic analysis revealed that evolution of the xylem transcriptome has paralleled plant evolution. We also identified 274 conifer-specific xylem unigenes, all of which are of unknown function. These xylem orthologs and conifer-specific unigenes are likely to have played a crucial role in xylem evolution. Conifers have highly conserved xylem transcriptomes, while angiosperm xylem transcriptomes are relatively diversified. Vascular plants share a common ancestral xylem transcriptome. The xylem transcriptomes of vascular plants are more conserved than the total transcriptomes. Evolution of the xylem transcriptome has largely followed the trend of plant evolution.

Comparative genomics reveals conservative evolution of the xylem transcriptome in vascular plants

PubMed Central

2010-01-01

Background Wood is a valuable natural resource and a major carbon sink. Wood formation is an important developmental process in vascular plants which played a crucial role in plant evolution. Although genes involved in xylem formation have been investigated, the molecular mechanisms of xylem evolution are not well understood. We use comparative genomics to examine evolution of the xylem transcriptome to gain insights into xylem evolution. Results The xylem transcriptome is highly conserved in conifers, but considerably divergent in angiosperms. The functional domains of genes in the xylem transcriptome are moderately to highly conserved in vascular plants, suggesting the existence of a common ancestral xylem transcriptome. Compared to the total transcriptome derived from a range of tissues, the xylem transcriptome is relatively conserved in vascular plants. Of the xylem transcriptome, cell wall genes, ancestral xylem genes, known proteins and transcription factors are relatively more conserved in vascular plants. A total of 527 putative xylem orthologs were identified, which are unevenly distributed across the Arabidopsis chromosomes with eight hot spots observed. Phylogenetic analysis revealed that evolution of the xylem transcriptome has paralleled plant evolution. We also identified 274 conifer-specific xylem unigenes, all of which are of unknown function. These xylem orthologs and conifer-specific unigenes are likely to have played a crucial role in xylem evolution. Conclusions Conifers have highly conserved xylem transcriptomes, while angiosperm xylem transcriptomes are relatively diversified. Vascular plants share a common ancestral xylem transcriptome. The xylem transcriptomes of vascular plants are more conserved than the total transcriptomes. Evolution of the xylem transcriptome has largely followed the trend of plant evolution. PMID:20565927

Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups

PubMed Central

Shtein, Ilana; Shelef, Yaniv; Marom, Ziv; Zelinger, Einat; Schwartz, Amnon; Popper, Zoë A.; Bar-On, Benny

2017-01-01

Background and Aims Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns (Asplenium nidus and Platycerium bifurcatum) and angiosperms (Arabidopsis thaliana and Commelina erecta) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata (Sorghum bicolor and Triticum aestivum). Key Results Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution. PMID:28158449

Development and evolution of extreme synorganization in angiosperm flowers and diversity: a comparison of Apocynaceae and Orchidaceae.

PubMed

Endress, Peter K

2016-04-01

Apocynaceae and Orchidaceae are two angiosperm families with extreme flower synorganization. They are unrelated, the former in eudicots, the latter in monocots, but they converge in the formation of pollinia and pollinaria, which do not occur in any other angiosperm family, and for which extreme synorganization of floral organs is a precondition. In each family extensive studies on flower development and evolution have been performed; however, newer comparative studies focusing on flower synorganization and involving both families together are lacking. For this study an extensive search through the morphological literature has been conducted. Based on this and my own studies on flowers in various Apocynaceae and Orchidaceae and complex flowers in other angiosperms with scanning electron microscopy and with microtome section series, a review on convergent floral traits in flower development and architecture in the two families is presented. There is a tendency of protracted development of synorganized parts in Apocynaceae and Orchidaceae (development of synorganization of two or more organs begins earlier the more accentuated it is at anthesis). Synorganization (or complexity) also paves the way for novel structures. One of the most conspicuous such novel structures in Apocynaceae is the corona, which is not the product of synorganization of existing organs; however, it is probably enhanced by synorganization of other, existing, floral parts. In contrast to synorganized parts, the corona appears developmentally late. Synorganization of floral organs may lead to a large number of convergences in clades that are only very distantly related. The convergences that have been highlighted in this comparative study should be developmentally investigated directly in parallel in future studies. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Slow but not low: genomic comparisons reveal slower evolutionary rate and higher dN/dS in conifers compared to angiosperms.

PubMed

Buschiazzo, Emmanuel; Ritland, Carol; Bohlmann, Jörg; Ritland, Kermit

2012-01-20

Comparative genomics can inform us about the processes of mutation and selection across diverse taxa. Among seed plants, gymnosperms have been lacking in genomic comparisons. Recent EST and full-length cDNA collections for two conifers, Sitka spruce (Picea sitchensis) and loblolly pine (Pinus taeda), together with full genome sequences for two angiosperms, Arabidopsis thaliana and poplar (Populus trichocarpa), offer an opportunity to infer the evolutionary processes underlying thousands of orthologous protein-coding genes in gymnosperms compared with an angiosperm orthologue set. Based upon pairwise comparisons of 3,723 spruce and pine orthologues, we found an average synonymous genetic distance (dS) of 0.191, and an average dN/dS ratio of 0.314. Using a fossil-established divergence time of 140 million years between spruce and pine, we extrapolated a nucleotide substitution rate of 0.68 × 10(-9) synonymous substitutions per site per year. When compared to angiosperms, this indicates a dramatically slower rate of nucleotide substitution rates in conifers: on average 15-fold. Coincidentally, we found a three-fold higher dN/dS for the spruce-pine lineage compared to the poplar-Arabidopsis lineage. This joint occurrence of a slower evolutionary rate in conifers with higher dN/dS, and possibly positive selection, showcases the uniqueness of conifer genome evolution. Our results are in line with documented reduced nucleotide diversity, conservative genome evolution and low rates of diversification in conifers on the one hand and numerous examples of local adaptation in conifers on the other hand. We propose that reduced levels of nucleotide mutation in large and long-lived conifer trees, coupled with large effective population size, were the main factors leading to slow substitution rates but retention of beneficial mutations.

Development and evolution of extreme synorganization in angiosperm flowers and diversity: a comparison of Apocynaceae and Orchidaceae

PubMed Central

Endress, Peter K.

2016-01-01

Background and Aims Apocynaceae and Orchidaceae are two angiosperm families with extreme flower synorganization. They are unrelated, the former in eudicots, the latter in monocots, but they converge in the formation of pollinia and pollinaria, which do not occur in any other angiosperm family, and for which extreme synorganization of floral organs is a precondition. In each family extensive studies on flower development and evolution have been performed; however, newer comparative studies focusing on flower synorganization and involving both families together are lacking. Scope For this study an extensive search through the morphological literature has been conducted. Based on this and my own studies on flowers in various Apocynaceae and Orchidaceae and complex flowers in other angiosperms with scanning electron microscopy and with microtome section series, a review on convergent floral traits in flower development and architecture in the two families is presented. Key Findings There is a tendency of protracted development of synorganized parts in Apocynaceae and Orchidaceae (development of synorganization of two or more organs begins earlier the more accentuated it is at anthesis). Synorganization (or complexity) also paves the way for novel structures. One of the most conspicuous such novel structures in Apocynaceae is the corona, which is not the product of synorganization of existing organs; however, it is probably enhanced by synorganization of other, existing, floral parts. In contrast to synorganized parts, the corona appears developmentally late. Conclusions Synorganization of floral organs may lead to a large number of convergences in clades that are only very distantly related. The convergences that have been highlighted in this comparative study should be developmentally investigated directly in parallel in future studies. PMID:26292994

The rise of angiosperm-dominated herbaceous floras: Insights from Ranunculaceae.

PubMed

Wang, Wei; Lin, Li; Xiang, Xiao-Guo; Ortiz, Rosa Del C; Liu, Yang; Xiang, Kun-Li; Yu, Sheng-Xiang; Xing, Yao-Wu; Chen, Zhi-Duan

2016-06-02

The rise of angiosperms has been regarded as a trigger for the Cretaceous revolution of terrestrial ecosystems. However, the timeframe of the rise angiosperm-dominated herbaceous floras (ADHFs) is lacking. Here, we used the buttercup family (Ranunculaceae) as a proxy to provide insights into the rise of ADHFs. An integration of phylogenetic, molecular dating, ancestral state inferring, and diversification analytical methods was used to infer the early evolutionary history of Ranunculaceae. We found that Ranunculaceae became differentiated in forests between about 108-90 Ma. Diversification rates markedly elevated during the Campanian, mainly resulted from the rapid divergence of the non-forest lineages, but did not change across the Cretaceous-Paleogene boundary. Our data for Ranunculaceae indicate that forest-dwelling ADHFs may have appeared almost simultaneously with angiosperm-dominated forests during the mid-Cretaceous, whereas non-forest ADHFs arose later, by the end of the Cretaceous terrestrial revolution. Furthermore, ADHFs were relatively unaffected by the Cretaceous-Paleogene mass extinction.

The rise of angiosperm-dominated herbaceous floras: Insights from Ranunculaceae

PubMed Central

Wang, Wei; Lin, Li; Xiang, Xiao-Guo; Ortiz, Rosa del C.; Liu, Yang; Xiang, Kun-Li; Yu, Sheng-Xiang; Xing, Yao-Wu; Chen, Zhi-Duan

2016-01-01

The rise of angiosperms has been regarded as a trigger for the Cretaceous revolution of terrestrial ecosystems. However, the timeframe of the rise angiosperm-dominated herbaceous floras (ADHFs) is lacking. Here, we used the buttercup family (Ranunculaceae) as a proxy to provide insights into the rise of ADHFs. An integration of phylogenetic, molecular dating, ancestral state inferring, and diversification analytical methods was used to infer the early evolutionary history of Ranunculaceae. We found that Ranunculaceae became differentiated in forests between about 108–90 Ma. Diversification rates markedly elevated during the Campanian, mainly resulted from the rapid divergence of the non-forest lineages, but did not change across the Cretaceous-Paleogene boundary. Our data for Ranunculaceae indicate that forest-dwelling ADHFs may have appeared almost simultaneously with angiosperm-dominated forests during the mid-Cretaceous, whereas non-forest ADHFs arose later, by the end of the Cretaceous terrestrial revolution. Furthermore, ADHFs were relatively unaffected by the Cretaceous-Paleogene mass extinction. PMID:27251635

Multiple Polyploidization Events across Asteraceae with Two Nested Events in the Early History Revealed by Nuclear Phylogenomics

PubMed Central

Huang, Chien-Hsun; Zhang, Caifei; Liu, Mian; Hu, Yi; Gao, Tiangang; Qi, Ji; Ma, Hong

2016-01-01

Biodiversity results from multiple evolutionary mechanisms, including genetic variation and natural selection. Whole-genome duplications (WGDs), or polyploidizations, provide opportunities for large-scale genetic modifications. Many evolutionarily successful lineages, including angiosperms and vertebrates, are ancient polyploids, suggesting that WGDs are a driving force in evolution. However, this hypothesis is challenged by the observed lower speciation and higher extinction rates of recently formed polyploids than diploids. Asteraceae includes about 10% of angiosperm species, is thus undoubtedly one of the most successful lineages and paleopolyploidization was suggested early in this family using a small number of datasets. Here, we used genes from 64 new transcriptome datasets and others to reconstruct a robust Asteraceae phylogeny, covering 73 species from 18 tribes in six subfamilies. We estimated their divergence times and further identified multiple potential ancient WGDs within several tribes and shared by the Heliantheae alliance, core Asteraceae (Asteroideae–Mutisioideae), and also with the sister family Calyceraceae. For two of the WGD events, there were subsequent great increases in biodiversity; the older one proceeded the divergence of at least 10 subfamilies within 10 My, with great variation in morphology and physiology, whereas the other was followed by extremely high species richness in the Heliantheae alliance clade. Our results provide different evidence for several WGDs in Asteraceae and reveal distinct association among WGD events, dramatic changes in environment and species radiations, providing a possible scenario for polyploids to overcome the disadvantages of WGDs and to evolve into lineages with high biodiversity. PMID:27604225

Palynological composition of a Lower Cretaceous South American tropical sequence: climatic implications and diversity comparisons with other latitudes.

PubMed

Mejia-Velasquez, Paula J; Dilcher, David L; Jaramillo, Carlos A; Fortini, Lucas B; Manchester, Steven R

2012-11-01

Reconstruction of floristic patterns during the early diversification of angiosperms is impeded by the scarce fossil record, especially in tropical latitudes. Here we collected quantitative palynological data from a stratigraphic sequence in tropical South America to provide floristic and climatic insights into such tropical environments during the Early Cretaceous. We reconstructed the floristic composition of an Aptian-Albian tropical sequence from central Colombia using quantitative palynology (rarefied species richness and abundance) and used it to infer its predominant climatic conditions. Additionally, we compared our results with available quantitative data from three other sequences encompassing 70 floristic assemblages to determine latitudinal diversity patterns. Abundance of humidity indicators was higher than that of aridity indicators (61% vs. 10%). Additionally, we found an angiosperm latitudinal diversity gradient (LDG) for the Aptian, but not for the Albian, and an inverted LDG of the overall diversity for the Albian. Angiosperm species turnover during the Albian, however, was higher in humid tropics. There were humid climates in northwestern South America during the Aptian-Albian interval contrary to the widespread aridity expected for the tropical belt. The Albian inverted overall LDG is produced by a faster increase in per-sample angiosperm and pteridophyte diversity in temperate latitudes. However, humid tropical sequences had higher rates of floristic turnover suggesting a higher degree of morphological variation than in temperate regions.

Palynological composition of a Lower Cretaceous South American tropical sequence: Climatic implications and diversity comparisons with other latitudes.

USGS Publications Warehouse

Mejia-Velasquez, Paula J.; Dilcher, David L.; Jaramillo, Carlos A.; Fortini, Lucas B.; Manchester, Steven R.

2012-01-01

Premise of the study: Reconstruction of floristic patterns during the early diversification of angiosperms is impeded by the scarce fossil record, especially in tropical latitudes. Here we collected quantitative palynological data from a stratigraphic sequence in tropical South America to provide floristic and climatic insights into such tropical environments during the Early Cretaceous. Methods: We reconstructed the floristic composition of an Aptian-Albian tropical sequence from central Colombia using quantitative palynology (rarefied species richness and abundance) and used it to infer its predominant climatic conditions. Additionally, we compared our results with available quantitative data from three other sequences encompassing 70 floristic assemblages to determine latitudinal diversity patterns. Key results: Abundance of humidity indicators was higher than that of aridity indicators (61% vs. 10%). Additionally, we found an angiosperm latitudinal diversity gradient (LDG) for the Aptian, but not for the Albian, and an inverted LDG of the overall diversity for the Albian. Angiosperm species turnover during the Albian, however, was higher in humid tropics. Conclusions: There were humid climates in northwestern South America during the Aptian-Albian interval contrary to the widespread aridity expected for the tropical belt. The Albian inverted overall LDG is produced by a faster increase in per-sample angiosperm and pteridophyte diversity in temperate latitudes. However, humid tropical sequences had higher rates of floristic turnover suggesting a higher degree of morphological variation than in temperate regions.

Reinvestigation of the Miocene palynoflora from the Daotaiqiao Formation of north-eastern China using SEM

NASA Astrophysics Data System (ADS)

Akyurt, Elvan; Grímsson, Friðgeir; Zetter, Reinhard; Leng, Qin; Bouchal, Johannes Martin

2016-04-01

Here we report the first results of an ongoing study on the Miocene palynoflora from the Daotaiqiao Formation of north-eastern China. Using the single grain technique, we examined individual pollen and spores using both light and scanning electron microscopy. A previous study by Grímsson et al. (2012) on Onagraceae pollen grains from this locality, using the same technique identified five different species. Such a variety of Onagraceae from a single palynoflora is unknown elsewhere. The ongoing study suggests a remarkably rich pollen and spore flora with at least 15 different types of spores, one Ginkgo and one Ephedra type pollen, 11 conifer pollen types and approximately 145 angiosperm pollen types. Spores are very rare in the samples (≤1%). Conifer pollen grains are regularly observed but are not a dominant component (ca. 16 %). The samples yield a high quantity and diversity of angiosperm pollen (ca. 80%). The conifers include representatives of Cupressaceae (2 spp.), Pinaceae (Larix, Picea, Pinus, Tsuga) and Sciadopityaceae. The angiosperm pollen cover at least 40 families. Prominent elements are pollen of the Betulaceae (Alnus, Betula, Carpinus, Corylus), Cercidiphyllaceae (Cercidiphyllum), Ericaceae (8 spp.), Eucommiaceae (Eucommia), Fagaceae (Fagus, Quercus spp., Castaneoideae), Juglandaceae (Carya, Cyclocarya, Juglans, Pterocarya), Rosaceae (11 spp.), Sapindaceae (Acer, Aesculus) and Ulmaceae (Hemiptelia, Ulmus, Zelkova). The high angiosperm pollen diversity indicates a varying landscape with a relatively high variety of niches including riparian, dry and mesic forests. Most of the potential modern analogues of the fossil taxa are currently thriving under humid temperate (Cfa- and Cwa)-climates, pointing to paleoclimate conditions not unlike those found today in the lowlands and adjacent mountain regions of the (south-) eastern United States, the humid-meridional region of western Eurasia, and central and southern China, and Honshu (Japan). References: Grímsson F, Zetter R, Leng Q. 2012. Diverse fossil Onagraceae pollen from a Miocene palynoflora of north-east China: early steps in resolving the phytogeographic history of the family. Plant Systematics and Evolution 298: 671-687.

Early Cretaceous Archaeamphora is not a carnivorous angiosperm

PubMed Central

Wong, William Oki; Dilcher, David Leonard; Labandeira, Conrad C.; Sun, Ge; Fleischmann, Andreas

2015-01-01

Archaeamphora longicervia H. Q. Li was described as an herbaceous, Sarraceniaceae-like pitcher plant from the mid Early Cretaceous Yixian Formation of Liaoning Province, northeastern China. Here, a re-investigation of A. longicervia specimens from the Yixian Formation provides new insights into its identity and the morphology of pitcher plants claimed by Li. We demonstrate that putative pitchers of Archaeamphora are insect-induced leaf galls that consist of three components: (1) an innermost larval chamber; (2) an intermediate zone of nutritive tissue; and (3) an outermost wall of sclerenchyma. Archaeamphora is not a carnivorous, Sarraceniaceae-like angiosperm, but represents insect-galled leaves of the previously reported gymnosperm Liaoningocladus boii G. Sun et al. from the Yixian Formation. PMID:25999978

Floral heterochrony promotes flexibility of reproductive strategies in the morphologically homogeneous genus Eugenia (Myrtaceae).

PubMed

Vasconcelos, Thais N C; Lucas, Eve J; Faria, Jair E Q; Prenner, Gerhard

2018-01-25

Comparative floral ontogeny represents a valuable tool to understand angiosperm evolution. Such an approach may elucidate subtle changes in development that discretely modify floral architecture and underlie reproductive lability in groups with superficial homogeneous morphology. This study presents a comparative survey of floral development in Eugenia (Myrtaceae), one of the largest genera of angiosperms, and shows how previously undocumented ontogenetic trends help to explain the evolution of its megadiversity in contrast to its apparent flower uniformity. Using scanning electron microscopy, selected steps of the floral ontogeny of a model species (Eugenia punicifolia) are described and compared with 20 further species representing all ten major clades in the Eugenia phylogenetic tree. Additional floral trait data are contrasted for correlation analysis and character reconstructions performed against the Myrtaceae phylogenetic tree. Eugenia flowers show similar organ arrangement patterns: radially symmetrical, (most commonly) tetramerous flowers with variable numbers of stamens and ovules. Despite a similar general organization, heterochrony is evident from size differences between tissues and structures at similar developmental stages. These differences underlie variable levels of investment in protection, subtle modifications to symmetry, herkogamic effects and independent androecium and gynoecium variation, producing a wide spectrum of floral display and contributing to fluctuations in fitness. During Eugenia's bud development, the hypanthium (as defined here) is completely covered by stamen primordia, unusual in other Myrtaceae. This is the likely plesiomorphic state for Myrteae and may have represented a key evolutionary novelty in the tribe. Floral evolution in Eugenia depends on heterochronic patterns rather than changes in complexity to promote flexibility in floral strategies. The successful early establishment of Myrteae, previously mainly linked to the key innovation of fleshy fruit, may also have benefitted from changes in flower structure. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Plastid Phylogenomic Analyses Resolve Tofieldiaceae as the Root of the Early Diverging Monocot Order Alismatales.

PubMed

Luo, Yang; Ma, Peng-Fei; Li, Hong-Tao; Yang, Jun-Bo; Wang, Hong; Li, De-Zhu

2016-04-06

The predominantly aquatic order Alismatales, which includes approximately 4,500 species within Araceae, Tofieldiaceae, and the core alismatid families, is a key group in investigating the origin and early diversification of monocots. Despite their importance, phylogenetic ambiguity regarding the root of the Alismatales tree precludes answering questions about the early evolution of the order. Here, we sequenced the first complete plastid genomes from three key families in this order:Potamogeton perfoliatus(Potamogetonaceae),Sagittaria lichuanensis(Alismataceae), andTofieldia thibetica(Tofieldiaceae). Each family possesses the typical quadripartite structure, with plastid genome sizes of 156,226, 179,007, and 155,512 bp, respectively. Among them, the plastid genome ofS. lichuanensisis the largest in monocots and the second largest in angiosperms. Like other sequenced Alismatales plastid genomes, all three families generally encode the same 113 genes with similar structure and arrangement. However, we detected 2.4 and 6 kb inversions in the plastid genomes ofSagittariaandPotamogeton, respectively. Further, we assembled a 79 plastid protein-coding gene sequence data matrix of 22 taxa that included the three newly generated plastid genomes plus 19 previously reported ones, which together represent all primary lineages of monocots and outgroups. In plastid phylogenomic analyses using maximum likelihood and Bayesian inference, we show both strong support for Acorales as sister to the remaining monocots and monophyly of Alismatales. More importantly, Tofieldiaceae was resolved as the most basal lineage within Alismatales. These results provide new insights into the evolution of Alismatales as well as the early-diverging monocots as a whole. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Mitochondrial Retroprocessing Promoted Functional Transfers of rpl5 to the Nucleus in Grasses.

PubMed

Wu, Zhiqiang; Sloan, Daniel B; Brown, Colin W; Rosenblueth, Mónica; Palmer, Jeffrey D; Ong, Han Chuan

2017-09-01

Functional gene transfers from the mitochondrion to the nucleus are ongoing in angiosperms and have occurred repeatedly for all 15 ribosomal protein genes, but it is not clear why some of these genes are transferred more often than others nor what the balance is between DNA- and RNA-mediated transfers. Although direct insertion of mitochondrial DNA into the nucleus occurs frequently in angiosperms, case studies of functional mitochondrial gene transfer have implicated an RNA-mediated mechanism that eliminates introns and RNA editing sites, which would otherwise impede proper expression of mitochondrial genes in the nucleus. To elucidate the mechanisms that facilitate functional gene transfers and the evolutionary dynamics of the coexisting nuclear and mitochondrial gene copies that are established during these transfers, we have analyzed rpl5 genes from 90 grasses (Poaceae) and related monocots. Multiple lines of evidence indicate that rpl5 has been functionally transferred to the nucleus at least three separate times in the grass family and that at least seven species have intact and transcribed (but not necessarily functional) copies in both the mitochondrion and nucleus. In two grasses, likely functional nuclear copies of rpl5 have been subject to recent gene conversion events via secondarily transferred mitochondrial copies in what we believe are the first described cases of mitochondrial-to-nuclear gene conversion. We show that rpl5 underwent a retroprocessing event within the mitochondrial genome early in the evolution of the grass family, which we argue predisposed the gene towards successful, DNA-mediated functional transfer by generating a "pre-edited" sequence. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Expressed sequence tags (ESTs) and phylogenetic analysis of floral genes from a paleoherb species, Asarum caudigerum.

PubMed

Zhao, Yinhe; Wang, Guoying; Zhang, Jinpeng; Yang, Junbo; Peng, Shang; Gao, Lianming; Li, Chengyun; Hu, Jinyong; Li, Dezhu; Gao, Lizhi

2006-07-01

Asarum caudigerum (Aristolochiaceae) is an important species of paleoherb in relation to understanding the origin and evolution of angiosperm flowers, due to its basal position in the angiosperms. The aim of this study was to isolate floral-related genes from A. caudigerum, and to infer evolutionary relationships among florally expression-related genes, to further illustrate the origin and diversification of flowers in angiosperms. A subtracted floral cDNA library was constructed from floral buds using suppression subtractive hybridization (SSH). The cDNA of floral buds and leaves at the seedling stage were used as a tester and a driver, respectively. To further identify the function of putative MADS-box transcription factors, phylogenetic trees were reconstructed in order to infer evolutionary relationships within the MADS-box gene family. In the forward-subtracted floral cDNA library, 1920 clones were randomly sequenced, from which 567 unique expressed sequence tags (ESTs) were obtained. Among them, 127 genes failed to show significant similarity to any published sequences in GenBank and thus are putatively novel genes. Phylogenetic analysis indicated that a total of 29 MADS-box transcription factors were members of the APETALA3(AP3) subfamily, while nine others were putative MADS-box transcription factors that formed a cluster with MADS-box genes isolated from Amborella, the basal-most angiosperm, and those from the gymnosperms. This suggests that the origin of A. caudigerum is intermediate between the angiosperms and gymnosperms.

MADS-Box gene diversity in seed plants 300 million years ago.

PubMed

Becker, A; Winter, K U; Meyer, B; Saedler, H; Theissen, G

2000-10-01

MADS-box genes encode a family of transcription factors which control diverse developmental processes in flowering plants ranging from root development to flower and fruit development. Through phylogeny reconstructions, most of these genes can be subdivided into defined monophyletic gene clades whose members share similar expression patterns and functions. Therefore, the establishment of the diversity of gene clades was probably an important event in land plant evolution. In order to determine when these clades originated, we isolated cDNAs of 19 different MADS-box genes from Gnetum gnemon, a gymnosperm model species and thus a representative of the sister group of the angiosperms. Phylogeny reconstructions involving all published MADS-box genes were then used to identify gene clades containing putative orthologs from both angiosperm and gymnosperm lineages. Thus, the minimal number of MADS-box genes that were already present in the last common ancestor of extant gymnosperms and angiosperms was determined. Comparative expression studies involving pairs of putatively orthologous genes revealed a diversity of patterns that has been largely conserved since the time when the angiosperm and gymnosperm lineages separated. Taken together, our data suggest that there were already at least seven different MADS-box genes present at the base of extant seed plants about 300 MYA. These genes were probably already quite diverse in terms of both sequence and function. In addition, our data demonstrate that the MADS-box gene families of extant gymnosperms and angiosperms are of similar complexities.

Potential Functional Replacement of the Plastidic Acetyl-CoA Carboxylase Subunit (accD) Gene by Recent Transfers to the Nucleus in Some Angiosperm Lineages1[W][OA

PubMed Central

Rousseau-Gueutin, Mathieu; Huang, Xun; Higginson, Emily; Ayliffe, Michael; Day, Anil; Timmis, Jeremy N.

2013-01-01

Eukaryotic cells originated when an ancestor of the nucleated cell engulfed bacterial endosymbionts that gradually evolved into the mitochondrion and the chloroplast. Soon after these endosymbiotic events, thousands of ancestral prokaryotic genes were functionally transferred from the endosymbionts to the nucleus. This process of functional gene relocation, now rare in eukaryotes, continues in angiosperms. In this article, we show that the chloroplastic acetyl-CoA carboxylase subunit (accD) gene that is present in the plastome of most angiosperms has been functionally relocated to the nucleus in the Campanulaceae. Surprisingly, the nucleus-encoded accD transcript is considerably smaller than the plastidic version, consisting of little more than the carboxylase domain of the plastidic accD gene fused to a coding region encoding a plastid targeting peptide. We verified experimentally the presence of a chloroplastic transit peptide by showing that the product of the nuclear accD fused to green fluorescent protein was imported in the chloroplasts. The nuclear gene regulatory elements that enabled the erstwhile plastidic gene to become functional in the nuclear genome were identified, and the evolution of the intronic and exonic sequences in the nucleus is described. Relocation and truncation of the accD gene is a remarkable example of the processes underpinning endosymbiotic evolution. PMID:23435694

Floral specialization and angiosperm diversity: phenotypic divergence, fitness trade-offs and realized pollination accuracy

PubMed Central

Armbruster, W. Scott

2014-01-01

Plant reproduction by means of flowers has long been thought to promote the success and diversification of angiosperms. It remains unclear, however, how this success has come about. Do flowers, and their capacity to have specialized functions, increase speciation rates or decrease extinction rates? Is floral specialization fundamental or incidental to the diversification? Some studies suggest that the conclusions we draw about the role of flowers in the diversification and increased phenotypic disparity (phenotypic diversity) of angiosperms depends on the system. For orchids, for example, specialized pollination may have increased speciation rates, in part because in most orchids pollen is packed in discrete units so that pollination is precise enough to contribute to reproductive isolation. In most plants, however, granular pollen results in low realized pollination precision, and thus key innovations involving flowers more likely reflect reduced extinction rates combined with opportunities for evolution of greater phenotypic disparity (phenotypic diversity) and occupation of new niches. Understanding the causes and consequences of the evolution of specialized flowers requires knowledge of both the selective regimes and the potential fitness trade-offs in using more than one pollinator functional group. The study of floral function and flowering-plant diversification remains a vibrant evolutionary field. Application of new methods, from measuring natural selection to estimating speciation rates, holds much promise for improving our understanding of the relationship between floral specialization and evolutionary success. PMID:24790124

Molecular evolutionary rates predict both extinction and speciation in temperate angiosperm lineages

PubMed Central

2010-01-01

Background A positive relationship between diversification (i.e., speciation) and nucleotide substitution rates is commonly reported for angiosperm clades. However, the underlying cause of this relationship is often unknown because multiple intrinsic and extrinsic factors can affect the relationship, and these have confounded previous attempts infer causation. Determining which factor drives this oft-reported correlation can lend insight into the macroevolutionary process. Results Using a new database of 13 time-calibrated angiosperm phylogenies based on internal transcribed spacer (ITS) sequences, and controlling for extrinsic variables of life history and habitat, I evaluated several potential intrinsic causes of this correlation. Speciation rates (λ) and relative extinction rates (ε) were positively correlated with mean substitution rates, but were uncorrelated with substitution rate heterogeneity. It is unlikely that the positive diversification-substitution correlation is due to accelerated molecular evolution during speciation (e.g., via enhanced selection or drift), because punctuated increases in ITS rate (i.e., greater mean and variation in ITS rate for rapidly speciating clades) were not observed. Instead, fast molecular evolution likely increases speciation rate (via increased mutational variation as a substrate for selection and reproductive isolation) but also increases extinction (via mutational genetic load). Conclusions In general, these results predict that clades with higher background substitution rates may undergo successful diversification under new conditions while clades with lower substitution rates may experience decreased extinction during environmental stasis. PMID:20515493

Evolution of Electrogenic Ammonium Transporters (AMTs)

DOE PAGES

McDonald, Tami R.; Ward, John M.

2016-03-31

The ammonium transporter gene family consists of three main clades, AMT, MEP, and Rh. The evolutionary history of the AMT/MEP/Rh gene family is characterized by multiple horizontal gene transfer events, gene family expansion and contraction, and gene loss; thus the gene tree for this family of transporters is unlike the organismal tree. The genomes of angiosperms contain genes for both electrogenic and electroneutral ammonium transporters, but it is not clear how far back in the land plant lineage electrogenic ammonium transporters occur. Here, we place Marchantia polymorpha ammonium transporters in the AMT/MEP/Rh phylogeny and we show that AMTs from themore » liverwort M. polymorpha are electrogenic. This information suggests that electrogenic ammonium transport evolved at least as early as the divergence of bryophytes in the land plant lineage.« less

Evolution of Electrogenic Ammonium Transporters (AMTs)

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDonald, Tami R.; Ward, John M.

The ammonium transporter gene family consists of three main clades, AMT, MEP, and Rh. The evolutionary history of the AMT/MEP/Rh gene family is characterized by multiple horizontal gene transfer events, gene family expansion and contraction, and gene loss; thus the gene tree for this family of transporters is unlike the organismal tree. The genomes of angiosperms contain genes for both electrogenic and electroneutral ammonium transporters, but it is not clear how far back in the land plant lineage electrogenic ammonium transporters occur. Here, we place Marchantia polymorpha ammonium transporters in the AMT/MEP/Rh phylogeny and we show that AMTs from themore » liverwort M. polymorpha are electrogenic. This information suggests that electrogenic ammonium transport evolved at least as early as the divergence of bryophytes in the land plant lineage.« less

A new paradigma on the plant evolution: from a natural evolution to an artificial evolution?

PubMed

Bennici, Andrea

2005-01-01

After evidencing the great importance of plants for animals and humans in consequence of the photosynthesis, several considerations on plant evolution are made. One of the peculiar characteristics of the plant is the sessile property, due especially to the cell wall. This factor, principally, strengthened by the photosynthetic process, determined the particular developmental pattern of the plant, which is characterized by the continuous formation of new organs. The plant immobility, although negative for its survival, has been, in great part, overcome by the acquisition of the capacity of adaptation (plasticity) to the environmental stresses and changes, and the establishment of more adapted genotypes. This capacity to react to the external signals induced Trewavas to speak of "plant intelligence". The plant movement incapacity and the evolution of the sexual reproduction system were strongly correlated. In this context, the evolution of the flower in the Angiosperms has been particularly important to allow the male gamete to fertilize the immobile female gamete. Moreover, the formation of fruit and seed greatly improved the dispersal and conservation of the progeny in the environment. With the flower, mechanisms to favour the outcrossing among different individuals appeared, which are essential to increase the genetic variability and, then, the plant evolution itself. Although the Angiosperms seem highly evolved, the plant evolution is not surely finished, because many reported morpho-physiological processes may be still considered susceptible of further improvement. In the last years the relationships among humans, plants and environment are becoming closer and closer. This is due to the use of the DNA recombinant techniques with the aim to modify artificially plant characters. Therefore, the risk of a plant evolution strongly directed towards practical or commercial objectives, or "an artificial evolution", may be hypothesized.

Water lilies as emerging models for Darwin’s abominable mystery

PubMed Central

Chen, Fei; Liu, Xing; Yu, Cuiwei; Chen, Yuchu; Tang, Haibao; Zhang, Liangsheng

2017-01-01

Water lilies are not only highly favored aquatic ornamental plants with cultural and economic importance but they also occupy a critical evolutionary space that is crucial for understanding the origin and early evolutionary trajectory of flowering plants. The birth and rapid radiation of flowering plants has interested many scientists and was considered ‘an abominable mystery’ by Charles Darwin. In searching for the angiosperm evolutionary origin and its underlying mechanisms, the genome of Amborella has shed some light on the molecular features of one of the basal angiosperm lineages; however, little is known regarding the genetics and genomics of another basal angiosperm lineage, namely, the water lily. In this study, we reviewed current molecular research and note that water lily research has entered the genomic era. We propose that the genome of the water lily is critical for studying the contentious relationship of basal angiosperms and Darwin’s ‘abominable mystery’. Four pantropical water lilies, especially the recently sequenced Nymphaea colorata, have characteristics such as small size, rapid growth rate and numerous seeds and can act as the best model for understanding the origin of angiosperms. The water lily genome is also valuable for revealing the genetics of ornamental traits and will largely accelerate the molecular breeding of water lilies. PMID:28979789

Fruit evolution and diversification in campanulid angiosperms.

PubMed

Beaulieu, Jeremy M; Donoghue, Michael J

2013-11-01

With increases in both the size and scope of phylogenetic trees, we are afforded a renewed opportunity to address long-standing comparative questions, such as whether particular fruit characters account for much of the variation in diversity among flowering plant clades. Studies to date have reported conflicting results, largely as a consequence of taxonomic scale and a reliance on potentially conservative statistical measures. Here we examine a larger and older angiosperm clade, the Campanulidae, and infer the rates of character transitions among the major fruit types, emphasizing the evolution of the achene fruits that are most frequently observed within the group. Our analyses imply that campanulids likely originated bearing capsules, and that all subsequent fruit diversity was derived from various modifications of this dry fruit type. We also found that the preponderance of lineages bearing achenes is a consequence of not only being a fruit type that is somewhat irreversible once it evolves, but one that also seems to have a positive association with diversification rates. Although these results imply the achene fruit type is a significant correlate of diversity patterns observed across campanulids, we conclude that it remains difficult to confidently and directly view this character state as the actual cause of increased diversification rates. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Fire feedbacks over geological time and the evolution of atmospheric oxygen concentration

NASA Astrophysics Data System (ADS)

Mills, B.; Belcher, C.; Lenton, T. M.

2017-12-01

During the 4.5 billion year history of the Earth, the concentration of oxygen in the atmosphere has risen from trace levels to today's 21%. Yet over the last 400 million years, O2 concentration appears to have remained within a relatively narrow range (around 15% - 30%), despite dramatic changes in the nature of global biogeochemical cycling. This stability has been crucial for continued animal evolution, and is thought to have arisen through feedbacks between oxygen, wildfire and plant productivity: the strong oxygen- dependence of fire initiation and spread means that global photosynthetic primary productivity is suppressed when oxygen levels are high, and enhanced when levels are low. We present biogeochemical modelling of the long term carbon and oxygen cycles, which aims to capture the operation of the wildfire feedback alongside other key processes. We find that wildfire can effectively stabilize long term oxygen concentrations, but that the nature of this feedback has changed as plant evolution has provided different fuels. Specifically, the evolution of early angiosperms during the Cretaceous period provided new understory fuels that more easily facilitated crown and canopy fires. Adding these dynamics to our model produces a more stable system over long timescales, and the model predicts that oxygen concentration has declined towards the present day - a prediction that is supported by other independent estimates.

Rapid sequencing of the bamboo mitochondrial genome using Illumina technology and parallel episodic evolution of organelle genomes in grasses.

PubMed

Ma, Peng-Fei; Guo, Zhen-Hua; Li, De-Zhu

2012-01-01

Compared to their counterparts in animals, the mitochondrial (mt) genomes of angiosperms exhibit a number of unique features. However, unravelling their evolution is hindered by the few completed genomes, of which are essentially Sanger sequenced. While next-generation sequencing technologies have revolutionized chloroplast genome sequencing, they are just beginning to be applied to angiosperm mt genomes. Chloroplast genomes of grasses (Poaceae) have undergone episodic evolution and the evolutionary rate was suggested to be correlated between chloroplast and mt genomes in Poaceae. It is interesting to investigate whether correlated rate change also occurred in grass mt genomes as expected under lineage effects. A time-calibrated phylogenetic tree is needed to examine rate change. We determined a largely completed mt genome from a bamboo, Ferrocalamus rimosivaginus (Poaceae), through Illumina sequencing of total DNA. With combination of de novo and reference-guided assembly, 39.5-fold coverage Illumina reads were finally assembled into scaffolds totalling 432,839 bp. The assembled genome contains nearly the same genes as the completed mt genomes in Poaceae. For examining evolutionary rate in grass mt genomes, we reconstructed a phylogenetic tree including 22 taxa based on 31 mt genes. The topology of the well-resolved tree was almost identical to that inferred from chloroplast genome with only minor difference. The inconsistency possibly derived from long branch attraction in mtDNA tree. By calculating absolute substitution rates, we found significant rate change (∼4-fold) in mt genome before and after the diversification of Poaceae both in synonymous and nonsynonymous terms. Furthermore, the rate change was correlated with that of chloroplast genomes in grasses. Our result demonstrates that it is a rapid and efficient approach to obtain angiosperm mt genome sequences using Illumina sequencing technology. The parallel episodic evolution of mt and chloroplast genomes in grasses is consistent with lineage effects.

Rapid Sequencing of the Bamboo Mitochondrial Genome Using Illumina Technology and Parallel Episodic Evolution of Organelle Genomes in Grasses

PubMed Central

Ma, Peng-Fei; Guo, Zhen-Hua; Li, De-Zhu

2012-01-01

Background Compared to their counterparts in animals, the mitochondrial (mt) genomes of angiosperms exhibit a number of unique features. However, unravelling their evolution is hindered by the few completed genomes, of which are essentially Sanger sequenced. While next-generation sequencing technologies have revolutionized chloroplast genome sequencing, they are just beginning to be applied to angiosperm mt genomes. Chloroplast genomes of grasses (Poaceae) have undergone episodic evolution and the evolutionary rate was suggested to be correlated between chloroplast and mt genomes in Poaceae. It is interesting to investigate whether correlated rate change also occurred in grass mt genomes as expected under lineage effects. A time-calibrated phylogenetic tree is needed to examine rate change. Methodology/Principal Findings We determined a largely completed mt genome from a bamboo, Ferrocalamus rimosivaginus (Poaceae), through Illumina sequencing of total DNA. With combination of de novo and reference-guided assembly, 39.5-fold coverage Illumina reads were finally assembled into scaffolds totalling 432,839 bp. The assembled genome contains nearly the same genes as the completed mt genomes in Poaceae. For examining evolutionary rate in grass mt genomes, we reconstructed a phylogenetic tree including 22 taxa based on 31 mt genes. The topology of the well-resolved tree was almost identical to that inferred from chloroplast genome with only minor difference. The inconsistency possibly derived from long branch attraction in mtDNA tree. By calculating absolute substitution rates, we found significant rate change (∼4-fold) in mt genome before and after the diversification of Poaceae both in synonymous and nonsynonymous terms. Furthermore, the rate change was correlated with that of chloroplast genomes in grasses. Conclusions/Significance Our result demonstrates that it is a rapid and efficient approach to obtain angiosperm mt genome sequences using Illumina sequencing technology. The parallel episodic evolution of mt and chloroplast genomes in grasses is consistent with lineage effects. PMID:22272330

Genome size diversity in orchids: consequences and evolution

PubMed Central

Leitch, I. J.; Kahandawala, I.; Suda, J.; Hanson, L.; Ingrouille, M. J.; Chase, M. W.; Fay, M. F.

2009-01-01

Background The amount of DNA comprising the genome of an organism (its genome size) varies a remarkable 40 000-fold across eukaryotes, yet most groups are characterized by much narrower ranges (e.g. 14-fold in gymnosperms, 3- to 4-fold in mammals). Angiosperms stand out as one of the most variable groups with genome sizes varying nearly 2000-fold. Nevertheless within angiosperms the majority of families are characterized by genomes which are small and vary little. Species with large genomes are mostly restricted to a few monocots families including Orchidaceae. Scope A survey of the literature revealed that genome size data for Orchidaceae are comparatively rare representing just 327 species. Nevertheless they reveal that Orchidaceae are currently the most variable angiosperm family with genome sizes ranging 168-fold (1C = 0·33–55·4 pg). Analysing the data provided insights into the distribution, evolution and possible consequences to the plant of this genome size diversity. Conclusions Superimposing the data onto the increasingly robust phylogenetic tree of Orchidaceae revealed how different subfamilies were characterized by distinct genome size profiles. Epidendroideae possessed the greatest range of genome sizes, although the majority of species had small genomes. In contrast, the largest genomes were found in subfamilies Cypripedioideae and Vanilloideae. Genome size evolution within this subfamily was analysed as this is the only one with reasonable representation of data. This approach highlighted striking differences in genome size and karyotype evolution between the closely related Cypripedium, Paphiopedilum and Phragmipedium. As to the consequences of genome size diversity, various studies revealed that this has both practical (e.g. application of genetic fingerprinting techniques) and biological consequences (e.g. affecting where and when an orchid may grow) and emphasizes the importance of obtaining further genome size data given the considerable phylogenetic gaps which have been highlighted by the current study. PMID:19168860

Contrasting Patterns of Nucleotide Substitution Rates Provide Insight into Dynamic Evolution of Plastid and Mitochondrial Genomes of Geranium.

PubMed

Park, Seongjun; Ruhlman, Tracey A; Weng, Mao-Lun; Hajrah, Nahid H; Sabir, Jamal S M; Jansen, Robert K

2017-06-01

Geraniaceae have emerged as a model system for investigating the causes and consequences of variation in plastid and mitochondrial genomes. Incredible structural variation in plastid genomes (plastomes) and highly accelerated evolutionary rates have been reported in selected lineages and functional groups of genes in both plastomes and mitochondrial genomes (mitogenomes), and these phenomena have been implicated in cytonuclear incompatibility. Previous organelle genome studies have included limited sampling of Geranium, the largest genus in the family with over 400 species. This study reports on rates and patterns of nucleotide substitutions in plastomes and mitogenomes of 17 species of Geranium and representatives of other Geraniaceae. As detected across other angiosperms, substitution rates in the plastome are 3.5 times higher than the mitogenome in most Geranium. However, in the branch leading to Geranium brycei/Geranium incanum mitochondrial genes experienced significantly higher dN and dS than plastid genes, a pattern that has only been detected in one other angiosperm. Furthermore, rate accelerations differ in the two organelle genomes with plastomes having increased dN and mitogenomes with increased dS. In the Geranium phaeum/Geranium reflexum clade, duplicate copies of clpP and rpoA genes that experienced asymmetric rate divergence were detected in the single copy region of the plastome. In the case of rpoA, the branch leading to G. phaeum/G. reflexum experienced positive selection or relaxation of purifying selection. Finally, the evolution of acetyl-CoA carboxylase is unusual in Geraniaceae because it is only the second angiosperm family where both prokaryotic and eukaryotic ACCases functionally coexist in the plastid. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Kin selection and the evolution of plant reproductive traits.

PubMed

Bawa, Kamaljit S

2016-11-16

Competition among developing seeds and sibling rivalry within multiovulated ovaries can be deleterious for both the maternal parent and the siblings. Increased genetic relatedness of seeds within the ovary may foster kin selection and reduce the deleterious consequences of sibling competition. The pollen parent may also be selected for siring all progeny within a fruit. I propose a series of hypotheses to explain the evolution of a number of reproductive traits in angiosperms in the context of kin selection and sibling rivalry within the ovaries of angiosperms. I present evidence to show that a single-pollen parent, indeed, often sires seeds within multiovulated ovaries. Various types of pollen aggregations and transfer of such pollen masses to the stigmas of flowers by specialized pollinators make this increased genetic relatedness possible. An alternative mode to reduce sibling rivalry may be the reduction of ovule number to one, an evolutionary trend that has independently occurred many times in flowering plants. Finally, I build on previously established correlations to predict two sets of correlations among reproductive traits. In the first case, large showy flowers, transfer of pollen en masse by specialized pollinators, and multiovulated ovaries and multisided fruits seem to be correlated. In the second case, the previously established correlations among small and inconspicuous flowers, pollination by wind, water or generalist insects, flowers and fruits with few or single ovules and seeds, respectively, may also include monoecy or dioecy. Although correlations among many of these traits have been established in the past, I invoke kin selection and sibling competition to explain the evolution of correlated traits as two distinct evolutionary pathways in angiosperms. © 2016 The Authors.

Kin selection and the evolution of plant reproductive traits

PubMed Central

Bawa, Kamaljit S.

2016-01-01

Competition among developing seeds and sibling rivalry within multiovulated ovaries can be deleterious for both the maternal parent and the siblings. Increased genetic relatedness of seeds within the ovary may foster kin selection and reduce the deleterious consequences of sibling competition. The pollen parent may also be selected for siring all progeny within a fruit. I propose a series of hypotheses to explain the evolution of a number of reproductive traits in angiosperms in the context of kin selection and sibling rivalry within the ovaries of angiosperms. I present evidence to show that a single-pollen parent, indeed, often sires seeds within multiovulated ovaries. Various types of pollen aggregations and transfer of such pollen masses to the stigmas of flowers by specialized pollinators make this increased genetic relatedness possible. An alternative mode to reduce sibling rivalry may be the reduction of ovule number to one, an evolutionary trend that has independently occurred many times in flowering plants. Finally, I build on previously established correlations to predict two sets of correlations among reproductive traits. In the first case, large showy flowers, transfer of pollen en masse by specialized pollinators, and multiovulated ovaries and multisided fruits seem to be correlated. In the second case, the previously established correlations among small and inconspicuous flowers, pollination by wind, water or generalist insects, flowers and fruits with few or single ovules and seeds, respectively, may also include monoecy or dioecy. Although correlations among many of these traits have been established in the past, I invoke kin selection and sibling competition to explain the evolution of correlated traits as two distinct evolutionary pathways in angiosperms. PMID:27852800

Whole genome duplication events in plant evolution reconstructed and predicted using myosin motor proteins

PubMed Central

2013-01-01

Background The evolution of land plants is characterized by whole genome duplications (WGD), which drove species diversification and evolutionary novelties. Detecting these events is especially difficult if they date back to the origin of the plant kingdom. Established methods for reconstructing WGDs include intra- and inter-genome comparisons, KS age distribution analyses, and phylogenetic tree constructions. Results By analysing 67 completely sequenced plant genomes 775 myosins were identified and manually assembled. Phylogenetic trees of the myosin motor domains revealed orthologous and paralogous relationships and were consistent with recent species trees. Based on the myosin inventories and the phylogenetic trees, we have identified duplications of the entire myosin motor protein family at timings consistent with 23 WGDs, that had been reported before. We also predict 6 WGDs based on further protein family duplications. Notably, the myosin data support the two recently reported WGDs in the common ancestor of all extant angiosperms. We predict single WGDs in the Manihot esculenta and Nicotiana benthamiana lineages, two WGDs for Linum usitatissimum and Phoenix dactylifera, and a triplication or two WGDs for Gossypium raimondii. Our data show another myosin duplication in the ancestor of the angiosperms that could be either the result of a single gene duplication or a remnant of a WGD. Conclusions We have shown that the myosin inventories in angiosperms retain evidence of numerous WGDs that happened throughout plant evolution. In contrast to other protein families, many myosins are still present in extant species. They are closely related and have similar domain architectures, and their phylogenetic grouping follows the genome duplications. Because of its broad taxonomic sampling the dataset provides the basis for reliable future identification of further whole genome duplications. PMID:24053117

Whole genome duplication events in plant evolution reconstructed and predicted using myosin motor proteins.

PubMed

Mühlhausen, Stefanie; Kollmar, Martin

2013-09-22

The evolution of land plants is characterized by whole genome duplications (WGD), which drove species diversification and evolutionary novelties. Detecting these events is especially difficult if they date back to the origin of the plant kingdom. Established methods for reconstructing WGDs include intra- and inter-genome comparisons, KS age distribution analyses, and phylogenetic tree constructions. By analysing 67 completely sequenced plant genomes 775 myosins were identified and manually assembled. Phylogenetic trees of the myosin motor domains revealed orthologous and paralogous relationships and were consistent with recent species trees. Based on the myosin inventories and the phylogenetic trees, we have identified duplications of the entire myosin motor protein family at timings consistent with 23 WGDs, that had been reported before. We also predict 6 WGDs based on further protein family duplications. Notably, the myosin data support the two recently reported WGDs in the common ancestor of all extant angiosperms. We predict single WGDs in the Manihot esculenta and Nicotiana benthamiana lineages, two WGDs for Linum usitatissimum and Phoenix dactylifera, and a triplication or two WGDs for Gossypium raimondii. Our data show another myosin duplication in the ancestor of the angiosperms that could be either the result of a single gene duplication or a remnant of a WGD. We have shown that the myosin inventories in angiosperms retain evidence of numerous WGDs that happened throughout plant evolution. In contrast to other protein families, many myosins are still present in extant species. They are closely related and have similar domain architectures, and their phylogenetic grouping follows the genome duplications. Because of its broad taxonomic sampling the dataset provides the basis for reliable future identification of further whole genome duplications.

Evolution of green plants as deduced from 5S rRNA sequences.

PubMed

Hori, H; Lim, B L; Osawa, S

1985-02-01

We have constructed a phylogenic tree for green plants by comparing 5S rRNA sequences. The tree suggests that the emergence of most of the uni- and multicellular green algae such as Chlamydomonas, Spirogyra, Ulva, and Chlorella occurred in the early stage of green plant evolution. The branching point of Nitella is a little earlier than that of land plants and much later than that of the above green algae, supporting the view that Nitella-like green algae may be the direct precursor to land plants. The Bryophyta and the Pteridophyta separated from each other after emergence of the Spermatophyta. The result is consistent with the view that the Bryophyta evolved from ferns by degeneration. In the Pteridophyta, Psilotum (whisk fern) separated first, and a little later Lycopodium (club moss) separated from the ancestor common to Equisetum (horsetail) and Dryopteris (fern). This order is in accordance with the classical view. During the Spermatophyta evolution, the gymnosperms (Cycas, Ginkgo, and Metasequoia have been studied here) and the angiosperms (flowering plants) separated, and this was followed by the separation of Metasequoia and Cycas (cycad)/Ginkgo (maidenhair tree) on one branch and various flowering plants on the other.

Evolution of green plants as deduced from 5S rRNA sequences

PubMed Central

Hori, Hiroshi; Lim, Byung-Lak; Osawa, Syozo

1985-01-01

We have constructed a phylogenic tree for green plants by comparing 5S rRNA sequences. The tree suggests that the emergence of most of the uni- and multicellular green algae such as Chlamydomonas, Spirogyra, Ulva, and Chlorella occurred in the early stage of green plant evolution. The branching point of Nitella is a little earlier than that of land plants and much later than that of the above green algae, supporting the view that Nitella-like green algae may be the direct precursor to land plants. The Bryophyta and the Pteridophyta separated from each other after emergence of the Spermatophyta. The result is consistent with the view that the Bryophyta evolved from ferns by degeneration. In the Pteridophyta, Psilotum (whisk fern) separated first, and a little later Lycopodium (club moss) separated from the ancestor common to Equisetum (horsetail) and Dryopteris (fern). This order is in accordance with the classical view. During the Spermatophyta evolution, the gymnosperms (Cycas, Ginkgo, and Metasequoia have been studied here) and the angiosperms (flowering plants) separated, and this was followed by the separation of Metasequoia and Cycas (cycad)/Ginkgo (maidenhair tree) on one branch and various flowering plants on the other. PMID:16593540

The evolution of scarab beetles tracks the sequential rise of angiosperms and mammals

PubMed Central

Ahrens, Dirk; Schwarzer, Julia; Vogler, Alfried P.

2014-01-01

Extant terrestrial biodiversity arguably is driven by the evolutionary success of angiosperm plants, but the evolutionary mechanisms and timescales of angiosperm-dependent radiations remain poorly understood. The Scarabaeoidea is a diverse lineage of predominantly plant- and dung-feeding beetles. Here, we present a phylogenetic analysis of Scarabaeoidea based on four DNA markers for a taxonomically comprehensive set of specimens and link it to recently described fossil evidence. The phylogeny strongly supports multiple origins of coprophagy, phytophagy and anthophagy. The ingroup-based fossil calibration of the tree widely confirmed a Jurassic origin of the Scarabaeoidea crown group. The crown groups of phytophagous lineages began to radiate first (Pleurostict scarabs: 108 Ma; Glaphyridae between 101 Ma), followed by the later diversification of coprophagous lineages (crown-group age Scarabaeinae: 76 Ma; Aphodiinae: 50 Ma). Pollen feeding arose even later, at maximally 62 Ma in the oldest anthophagous lineage. The clear time lag between the origins of herbivores and coprophages suggests an evolutionary path driven by the angiosperms that first favoured the herbivore fauna (mammals and insects) followed by the secondary radiation of the dung feeders. This finding makes it less likely that extant dung beetle lineages initially fed on dinosaur excrements, as often hypothesized. PMID:25100705

Functional bisporangiate cones in Pinus johannis (Pinaceae): Implications for the evolution of bisexuality in seed plants.

PubMed

Flores-Rentería, Lluvia; Vázquez-Lobo, Alejandra; Whipple, Amy V; Piñero, Daniel; Márquez-Guzmán, Judith; Domínguez, C A

2011-01-01

Bisexuality (male and female function in one structure) has been reported as a key innovation of angiosperms. Although there are several reports of "teratological" bisporangiate (bisexual) cones in gymnosperms, there have been none on the viability of their ovules and pollen. Analyses of the development and arrangement of female and male structures on bisporangiate cones of Pinus johannis enables us to gain insight on the origin of bisexuality in seed plants, for both angiosperms and gymnosperms. Viability of bisporangiate cones was assayed by performing manual crosses and using anatomical and histological methods. We determined that bisporangiate cones of P. johannis produce functional pollen and ovules. Male and female organs occupy basal and apical positions, respectively, the same positions found in almost all bisporangiate strobili in gymnosperms and bisexual flowers in angiosperms. The viability and spatial distribution of female and male organs of bisporangiate cones and their frequent occurrence in gymnosperms suggest a common mechanism in all seed plants for the production of bisporangiate structures. This idea is further supported by the presence of homologous genes for sexual organ identity in gymnosperms and angiosperms as reported by other authors. The lack of bisporangiate structure in gymnosperms may be primarily due to selection to avoid inbreeding rather than to genetic constraint.

Evolution of the Class IV HD-Zip Gene Family in Streptophytes

PubMed Central

Zalewski, Christopher S.; Floyd, Sandra K.; Furumizu, Chihiro; Sakakibara, Keiko; Stevenson, Dennis W.; Bowman, John L.

2013-01-01

Class IV homeodomain leucine zipper (C4HDZ) genes are plant-specific transcription factors that, based on phenotypes in Arabidopsis thaliana, play an important role in epidermal development. In this study, we sampled all major extant lineages and their closest algal relatives for C4HDZ homologs and phylogenetic analyses result in a gene tree that mirrors land plant evolution with evidence for gene duplications in many lineages, but minimal evidence for gene losses. Our analysis suggests an ancestral C4HDZ gene originated in an algal ancestor of land plants and a single ancestral gene was present in the last common ancestor of land plants. Independent gene duplications are evident within several lineages including mosses, lycophytes, euphyllophytes, seed plants, and, most notably, angiosperms. In recently evolved angiosperm paralogs, we find evidence of pseudogenization via mutations in both coding and regulatory sequences. The increasing complexity of the C4HDZ gene family through the diversification of land plants correlates to increasing complexity in epidermal characters. PMID:23894141

Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering

PubMed Central

Quirk, Joe; Beerling, David J.; Banwart, Steve A.; Kakonyi, Gabriella; Romero-Gonzalez, Maria E.; Leake, Jonathan R.

2012-01-01

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to ‘trenching’ of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO2 and climate history. PMID:22859556

Ferns: the missing link in shoot evolution and development.

PubMed

Plackett, Andrew R G; Di Stilio, Verónica S; Langdale, Jane A

2015-01-01

Shoot development in land plants is a remarkably complex process that gives rise to an extreme diversity of forms. Our current understanding of shoot developmental mechanisms comes almost entirely from studies of angiosperms (flowering plants), the most recently diverged plant lineage. Shoot development in angiosperms is based around a layered multicellular apical meristem that produces lateral organs and/or secondary meristems from populations of founder cells at its periphery. In contrast, non-seed plant shoots develop from either single apical initials or from a small population of morphologically distinct apical cells. Although developmental and molecular information is becoming available for non-flowering plants, such as the model moss Physcomitrella patens, making valid comparisons between highly divergent lineages is extremely challenging. As sister group to the seed plants, the monilophytes (ferns and relatives) represent an excellent phylogenetic midpoint of comparison for unlocking the evolution of shoot developmental mechanisms, and recent technical advances have finally made transgenic analysis possible in the emerging model fern Ceratopteris richardii. This review compares and contrasts our current understanding of shoot development in different land plant lineages with the aim of highlighting the potential role that the fern C. richardii could play in shedding light on the evolution of underlying genetic regulatory mechanisms.

Scalariform-to-simple transition in vessel perforation plates triggered by differences in climate during the evolution of Adoxaceae

PubMed Central

Lens, Frederic; Vos, Rutger A.; Charrier, Guillaume; van der Niet, Timo; Merckx, Vincent; Baas, Pieter; Aguirre Gutierrez, Jesus; Jacobs, Bart; Chacon Dória, Larissa; Smets, Erik; Delzon, Sylvain; Janssens, Steven B.

2016-01-01

Background and Aims Angiosperms with simple vessel perforations have evolved many times independently of species having scalariform perforations, but detailed studies to understand why these transitions in wood evolution have happened are lacking. We focus on the striking difference in wood anatomy between two closely related genera of Adoxaceae, Viburnum and Sambucus, and link the anatomical divergence with climatic and physiological insights. Methods After performing wood anatomical observations, we used a molecular phylogenetic framework to estimate divergence times for 127 Adoxaceae species. The conditions under which the genera diversified were estimated using ancestral area reconstruction and optimization of ancestral climates, and xylem-specific conductivity measurements were performed. Key Results Viburnum, characterized by scalariform vessel perforations (ancestral), diversified earlier than Sambucus, having simple perforations (derived). Ancestral climate reconstruction analyses point to cold temperate preference for Viburnum and warm temperate for Sambucus. This is reflected in the xylem-specific conductivity rates of the co-occurring species investigated, showing that Viburnum lantana has rates much lower than Sambucus nigra. Conclusions The lack of selective pressure for high conductive efficiency during early diversification of Viburnum and the potentially adaptive value of scalariform perforations in frost-prone cold temperate climates have led to retention of the ancestral vessel perforation type, while higher temperatures during early diversification of Sambucus have triggered the evolution of simple vessel perforations, allowing more efficient long-distance water transport. PMID:27498812

Evolution of Rosaceae Fruit Types Based on Nuclear Phylogeny in the Context of Geological Times and Genome Duplication.

PubMed

Xiang, Yezi; Huang, Chien-Hsun; Hu, Yi; Wen, Jun; Li, Shisheng; Yi, Tingshuang; Chen, Hongyi; Xiang, Jun; Ma, Hong

2017-02-01

Fruits are the defining feature of angiosperms, likely have contributed to angiosperm successes by protecting and dispersing seeds, and provide foods to humans and other animals, with many morphological types and important ecological and agricultural implications. Rosaceae is a family with ∼3000 species and an extraordinary spectrum of distinct fruits, including fleshy peach, apple, and strawberry prized by their consumers, as well as dry achenetum and follicetum with features facilitating seed dispersal, excellent for studying fruit evolution. To address Rosaceae fruit evolution and other questions, we generated 125 new transcriptomic and genomic datasets and identified hundreds of nuclear genes to reconstruct a well-resolved Rosaceae phylogeny with highly supported monophyly of all subfamilies and tribes. Molecular clock analysis revealed an estimated age of ∼101.6 Ma for crown Rosaceae and divergence times of tribes and genera, providing a geological and climate context for fruit evolution. Phylogenomic analysis yielded strong evidence for numerous whole genome duplications (WGDs), supporting the hypothesis that the apple tribe had a WGD and revealing another one shared by fleshy fruit-bearing members of this tribe, with moderate support for WGDs in the peach tribe and other groups. Ancestral character reconstruction for fruit types supports independent origins of fleshy fruits from dry-fruit ancestors, including the evolution of drupes (e.g., peach) and pomes (e.g., apple) from follicetum, and drupetum (raspberry and blackberry) from achenetum. We propose that WGDs and environmental factors, including animals, contributed to the evolution of the many fruits in Rosaceae, which provide a foundation for understanding fruit evolution. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Evolution of Epiphytism and Fruit Traits Act Unevenly on the Diversification of the Species-Rich Genus Peperomia (Piperaceae).

PubMed

Frenzke, Lena; Goetghebeur, Paul; Neinhuis, Christoph; Samain, Marie-Stéphanie; Wanke, Stefan

2016-01-01

The species-rich genus Peperomia (Black Pepper relatives) is the only genus among early diverging angiosperms where epiphytism evolved. The majority of fruits of Peperomia release sticky secretions or exhibit hook-shaped appendages indicative of epizoochorous dispersal, which is in contrast to other flowering plants, where epiphytes are generally characterized by fruit morphological adaptations for anemochory or endozoochory. We investigate fruit characters using Cryo-SEM. Comparative phylogenetic analyses are applied for the first time to include life form and fruit character information to study diversification in Peperomia. Likelihood ratio tests uncover correlated character evolution. We demonstrate that diversification within Peperomia is not homogenous across its phylogeny, and that net diversification rates increase by twofold within the most species-rich subgenus. In contrast to former land plant studies that provide general evidence for increased diversification in epiphytic lineages, we demonstrate that the evolution of epiphytism within Peperomia predates the diversification shift. An epiphytic-dependent diversification is only observed for the background phylogeny. An elevated frequency of life form transitions between epiphytes and terrestrials and thus evolutionary flexibility of life forms is uncovered to coincide with the diversification shift. The evolution of fruits showing dispersal related structures is key to diversification in the foreground region of the phylogeny and postdates the evolution of epiphytism. We conclude that the success of Peperomia, measured in species numbers, is likely the result of enhanced vertical and horizontal dispersal ability and life form flexibility but not the evolution of epiphytism itself.

Novelties of the flowering plant pollen tube underlie diversification of a key life history stage.

PubMed

Williams, Joseph H

2008-08-12

The origin and rapid diversification of flowering plants has puzzled evolutionary biologists, dating back to Charles Darwin. Since that time a number of key life history and morphological traits have been proposed as developmental correlates of the extraordinary diversity and ecological success of angiosperms. Here, I identify several innovations that were fundamental to the evolutionary lability of angiosperm reproduction, and hence to their diversification. In gymnosperms pollen reception must be near the egg largely because sperm swim or are transported by pollen tubes that grow at very slow rates (< approximately 20 microm/h). In contrast, pollen tube growth rates of taxa in ancient angiosperm lineages (Amborella, Nuphar, and Austrobaileya) range from approximately 80 to 600 microm/h. Comparative analyses point to accelerated pollen tube growth rate as a critical innovation that preceded the origin of the true closed carpel, long styles, multiseeded ovaries, and, in monocots and eudicots, much faster pollen tube growth rates. Ancient angiosperm pollen tubes all have callosic walls and callose plugs (in contrast, no gymnosperms have these features). The early association of the callose-walled growth pattern with accelerated pollen tube growth rate underlies a striking repeated pattern of faster and longer-distance pollen tube growth often within solid pathways in phylogenetically derived angiosperms. Pollen tube innovations are a key component of the spectacular diversification of carpel (flower and fruit) form and reproductive cycles in flowering plants.

Repeated polyploidization of Gossypium genomes and the evolution of spinnable cotton fibres.

PubMed

Paterson, Andrew H; Wendel, Jonathan F; Gundlach, Heidrun; Guo, Hui; Jenkins, Jerry; Jin, Dianchuan; Llewellyn, Danny; Showmaker, Kurtis C; Shu, Shengqiang; Udall, Joshua; Yoo, Mi-jeong; Byers, Robert; Chen, Wei; Doron-Faigenboim, Adi; Duke, Mary V; Gong, Lei; Grimwood, Jane; Grover, Corrinne; Grupp, Kara; Hu, Guanjing; Lee, Tae-ho; Li, Jingping; Lin, Lifeng; Liu, Tao; Marler, Barry S; Page, Justin T; Roberts, Alison W; Romanel, Elisson; Sanders, William S; Szadkowski, Emmanuel; Tan, Xu; Tang, Haibao; Xu, Chunming; Wang, Jinpeng; Wang, Zining; Zhang, Dong; Zhang, Lan; Ashrafi, Hamid; Bedon, Frank; Bowers, John E; Brubaker, Curt L; Chee, Peng W; Das, Sayan; Gingle, Alan R; Haigler, Candace H; Harker, David; Hoffmann, Lucia V; Hovav, Ran; Jones, Donald C; Lemke, Cornelia; Mansoor, Shahid; ur Rahman, Mehboob; Rainville, Lisa N; Rambani, Aditi; Reddy, Umesh K; Rong, Jun-kang; Saranga, Yehoshua; Scheffler, Brian E; Scheffler, Jodi A; Stelly, David M; Triplett, Barbara A; Van Deynze, Allen; Vaslin, Maite F S; Waghmare, Vijay N; Walford, Sally A; Wright, Robert J; Zaki, Essam A; Zhang, Tianzhen; Dennis, Elizabeth S; Mayer, Klaus F X; Peterson, Daniel G; Rokhsar, Daniel S; Wang, Xiyin; Schmutz, Jeremy

2012-12-20

Polyploidy often confers emergent properties, such as the higher fibre productivity and quality of tetraploid cottons than diploid cottons bred for the same environments. Here we show that an abrupt five- to sixfold ploidy increase approximately 60 million years (Myr) ago, and allopolyploidy reuniting divergent Gossypium genomes approximately 1-2 Myr ago, conferred about 30-36-fold duplication of ancestral angiosperm (flowering plant) genes in elite cottons (Gossypium hirsutum and Gossypium barbadense), genetic complexity equalled only by Brassica among sequenced angiosperms. Nascent fibre evolution, before allopolyploidy, is elucidated by comparison of spinnable-fibred Gossypium herbaceum A and non-spinnable Gossypium longicalyx F genomes to one another and the outgroup D genome of non-spinnable Gossypium raimondii. The sequence of a G. hirsutum A(t)D(t) (in which 't' indicates tetraploid) cultivar reveals many non-reciprocal DNA exchanges between subgenomes that may have contributed to phenotypic innovation and/or other emergent properties such as ecological adaptation by polyploids. Most DNA-level novelty in G. hirsutum recombines alleles from the D-genome progenitor native to its New World habitat and the Old World A-genome progenitor in which spinnable fibre evolved. Coordinated expression changes in proximal groups of functionally distinct genes, including a nuclear mitochondrial DNA block, may account for clusters of cotton-fibre quantitative trait loci affecting diverse traits. Opportunities abound for dissecting emergent properties of other polyploids, particularly angiosperms, by comparison to diploid progenitors and outgroups.

Slow but not low: genomic comparisons reveal slower evolutionary rate and higher dN/dS in conifers compared to angiosperms

PubMed Central

2012-01-01

Background Comparative genomics can inform us about the processes of mutation and selection across diverse taxa. Among seed plants, gymnosperms have been lacking in genomic comparisons. Recent EST and full-length cDNA collections for two conifers, Sitka spruce (Picea sitchensis) and loblolly pine (Pinus taeda), together with full genome sequences for two angiosperms, Arabidopsis thaliana and poplar (Populus trichocarpa), offer an opportunity to infer the evolutionary processes underlying thousands of orthologous protein-coding genes in gymnosperms compared with an angiosperm orthologue set. Results Based upon pairwise comparisons of 3,723 spruce and pine orthologues, we found an average synonymous genetic distance (dS) of 0.191, and an average dN/dS ratio of 0.314. Using a fossil-established divergence time of 140 million years between spruce and pine, we extrapolated a nucleotide substitution rate of 0.68 × 10-9 synonymous substitutions per site per year. When compared to angiosperms, this indicates a dramatically slower rate of nucleotide substitution rates in conifers: on average 15-fold. Coincidentally, we found a three-fold higher dN/dS for the spruce-pine lineage compared to the poplar-Arabidopsis lineage. This joint occurrence of a slower evolutionary rate in conifers with higher dN/dS, and possibly positive selection, showcases the uniqueness of conifer genome evolution. Conclusions Our results are in line with documented reduced nucleotide diversity, conservative genome evolution and low rates of diversification in conifers on the one hand and numerous examples of local adaptation in conifers on the other hand. We propose that reduced levels of nucleotide mutation in large and long-lived conifer trees, coupled with large effective population size, were the main factors leading to slow substitution rates but retention of beneficial mutations. PMID:22264329

Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups.

PubMed

Shtein, Ilana; Shelef, Yaniv; Marom, Ziv; Zelinger, Einat; Schwartz, Amnon; Popper, Zoë A; Bar-On, Benny; Harpaz-Saad, Smadar

2017-04-01

Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns ( Asplenium nidus and Platycerium bifurcatum ) and angiosperms ( Arabidopsis thaliana and Commelina erecta ) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata ( Sorghum bicolor and Triticum aestivum ). Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company.

Floral gene resources from basal angiosperms for comparative genomics research

PubMed Central

Albert, Victor A; Soltis, Douglas E; Carlson, John E; Farmerie, William G; Wall, P Kerr; Ilut, Daniel C; Solow, Teri M; Mueller, Lukas A; Landherr, Lena L; Hu, Yi; Buzgo, Matyas; Kim, Sangtae; Yoo, Mi-Jeong; Frohlich, Michael W; Perl-Treves, Rafael; Schlarbaum, Scott E; Bliss, Barbara J; Zhang, Xiaohong; Tanksley, Steven D; Oppenheimer, David G; Soltis, Pamela S; Ma, Hong; dePamphilis, Claude W; Leebens-Mack, James H

2005-01-01

Background The Floral Genome Project was initiated to bridge the genomic gap between the most broadly studied plant model systems. Arabidopsis and rice, although now completely sequenced and under intensive comparative genomic investigation, are separated by at least 125 million years of evolutionary time, and cannot in isolation provide a comprehensive perspective on structural and functional aspects of flowering plant genome dynamics. Here we discuss new genomic resources available to the scientific community, comprising cDNA libraries and Expressed Sequence Tag (EST) sequences for a suite of phylogenetically basal angiosperms specifically selected to bridge the evolutionary gaps between model plants and provide insights into gene content and genome structure in the earliest flowering plants. Results Random sequencing of cDNAs from representatives of phylogenetically important eudicot, non-grass monocot, and gymnosperm lineages has so far (as of 12/1/04) generated 70,514 ESTs and 48,170 assembled unigenes. Efficient sorting of EST sequences into putative gene families based on whole Arabidopsis/rice proteome comparison has permitted ready identification of cDNA clones for finished sequencing. Preliminarily, (i) proportions of functional categories among sequenced floral genes seem representative of the entire Arabidopsis transcriptome, (ii) many known floral gene homologues have been captured, and (iii) phylogenetic analyses of ESTs are providing new insights into the process of gene family evolution in relation to the origin and diversification of the angiosperms. Conclusion Initial comparisons illustrate the utility of the EST data sets toward discovery of the basic floral transcriptome. These first findings also afford the opportunity to address a number of conspicuous evolutionary genomic questions, including reproductive organ transcriptome overlap between angiosperms and gymnosperms, genome-wide duplication history, lineage-specific gene duplication and functional divergence, and analyses of adaptive molecular evolution. Since not all genes in the floral transcriptome will be associated with flowering, these EST resources will also be of interest to plant scientists working on other functions, such as photosynthesis, signal transduction, and metabolic pathways. PMID:15799777

Plastid Phylogenomic Analyses Resolve Tofieldiaceae as the Root of the Early Diverging Monocot Order Alismatales

PubMed Central

Luo, Yang; Ma, Peng-Fei; Li, Hong-Tao; Yang, Jun-Bo; Wang, Hong; Li, De-Zhu

2016-01-01

The predominantly aquatic order Alismatales, which includes approximately 4,500 species within Araceae, Tofieldiaceae, and the core alismatid families, is a key group in investigating the origin and early diversification of monocots. Despite their importance, phylogenetic ambiguity regarding the root of the Alismatales tree precludes answering questions about the early evolution of the order. Here, we sequenced the first complete plastid genomes from three key families in this order: Potamogeton perfoliatus (Potamogetonaceae), Sagittaria lichuanensis (Alismataceae), and Tofieldia thibetica (Tofieldiaceae). Each family possesses the typical quadripartite structure, with plastid genome sizes of 156,226, 179,007, and 155,512 bp, respectively. Among them, the plastid genome of S. lichuanensis is the largest in monocots and the second largest in angiosperms. Like other sequenced Alismatales plastid genomes, all three families generally encode the same 113 genes with similar structure and arrangement. However, we detected 2.4 and 6 kb inversions in the plastid genomes of Sagittaria and Potamogeton, respectively. Further, we assembled a 79 plastid protein-coding gene sequence data matrix of 22 taxa that included the three newly generated plastid genomes plus 19 previously reported ones, which together represent all primary lineages of monocots and outgroups. In plastid phylogenomic analyses using maximum likelihood and Bayesian inference, we show both strong support for Acorales as sister to the remaining monocots and monophyly of Alismatales. More importantly, Tofieldiaceae was resolved as the most basal lineage within Alismatales. These results provide new insights into the evolution of Alismatales as well as the early-diverging monocots as a whole. PMID:26957030

Angiosperms Are Unique among Land Plant Lineages in the Occurrence of Key Genes in the RNA-Directed DNA Methylation (RdDM) Pathway.

PubMed

Ma, Lu; Hatlen, Andrea; Kelly, Laura J; Becher, Hannes; Wang, Wencai; Kovarik, Ales; Leitch, Ilia J; Leitch, Andrew R

2015-09-02

The RNA-directed DNA methylation (RdDM) pathway can be divided into three phases: 1) small interfering RNA biogenesis, 2) de novo methylation, and 3) chromatin modification. To determine the degree of conservation of this pathway we searched for key genes among land plants. We used OrthoMCL and the OrthoMCL Viridiplantae database to analyze proteomes of species in bryophytes, lycophytes, monilophytes, gymnosperms, and angiosperms. We also analyzed small RNA size categories and, in two gymnosperms, cytosine methylation in ribosomal DNA. Six proteins were restricted to angiosperms, these being NRPD4/NRPE4, RDM1, DMS3 (defective in meristem silencing 3), SHH1 (SAWADEE homeodomain homolog 1), KTF1, and SUVR2, although we failed to find the latter three proteins in Fritillaria persica, a species with a giant genome. Small RNAs of 24 nt in length were abundant only in angiosperms. Phylogenetic analyses of Dicer-like (DCL) proteins showed that DCL2 was restricted to seed plants, although it was absent in Gnetum gnemon and Welwitschia mirabilis. The data suggest that phases (1) and (2) of the RdDM pathway, described for model angiosperms, evolved with angiosperms. The absence of some features of RdDM in F. persica may be associated with its large genome. Phase (3) is probably the most conserved part of the pathway across land plants. DCL2, involved in virus defense and interaction with the canonical RdDM pathway to facilitate methylation of CHH, is absent outside seed plants. Its absence in G. gnemon, and W. mirabilis coupled with distinctive patterns of CHH methylation, suggest a secondary loss of DCL2 following the divergence of Gnetales. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

The effect of polyploidy and hybridization on the evolution of floral colour in Nicotiana (Solanaceae)

PubMed Central

McCarthy, Elizabeth W.; Arnold, Sarah E. J.; Chittka, Lars; Le Comber, Steven C.; Verity, Robert; Dodsworth, Steven; Knapp, Sandra; Kelly, Laura J.; Chase, Mark W.; Baldwin, Ian T.; Kovařík, Aleš; Mhiri, Corinne; Taylor, Lin; Leitch, Andrew R.

2015-01-01

Background and Aims Speciation in angiosperms can be accompanied by changes in floral colour that may influence pollinator preference and reproductive isolation. This study investigates whether changes in floral colour can accompany polyploid and homoploid hybridization, important processes in angiosperm evolution. Methods Spectral reflectance of corolla tissue was examined for 60 Nicotiana (Solanaceae) accessions (41 taxa) based on spectral shape (corresponding to pigmentation) as well as bee and hummingbird colour perception in order to assess patterns of floral colour evolution. Polyploid and homoploid hybrid spectra were compared with those of their progenitors to evaluate whether hybridization has resulted in floral colour shifts. Key Results Floral colour categories in Nicotiana seem to have arisen multiple times independently during the evolution of the genus. Most younger polyploids displayed an unexpected floral colour, considering those of their progenitors, in the colour perception of at least one pollinator type, whereas older polyploids tended to resemble one or both of their progenitors. Conclusions Floral colour evolution in Nicotiana is weakly constrained by phylogeny, and colour shifts do occur in association with both polyploid and homoploid hybrid divergence. Transgressive floral colour in N. tabacum has arisen by inheritance of anthocyanin pigmentation from its paternal progenitor while having a plastid phenotype like its maternal progenitor. Potentially, floral colour evolution has been driven by, or resulted in, pollinator shifts. However, those polyploids that are not sympatric (on a regional scale) with their progenitor lineages are typically not divergent in floral colour from them, perhaps because of a lack of competition for pollinators. PMID:25979919

Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway.

PubMed

Horn, James W; Xi, Zhenxiang; Riina, Ricarda; Peirson, Jess A; Yang, Ya; Dorsey, Brian L; Berry, Paul E; Davis, Charles C; Wurdack, Kenneth J

2014-12-01

The mid-Cenozoic decline of atmospheric CO2 levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO2 -concentrating mechanisms (CCMs)-crassulacean acid metabolism (CAM) and C4 -evolved from the C3 photosynthetic pathway, enabling more efficient whole-plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates (r) remain to be further understood. Euphorbia (∼2000 species) includes a diversity of CAM-using stem succulents, plus a single species-rich C4 subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17-22 times in Euphorbia, principally from the Miocene onwards. Analyses assessing among-lineage variation in r identified eight Euphorbia subclades with significantly increased r, six of which have a close temporal relationship with a lineage-corresponding CCM origin. Our trait-dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C3 lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

The Apostasia genome and the evolution of orchids.

PubMed

Zhang, Guo-Qiang; Liu, Ke-Wei; Li, Zhen; Lohaus, Rolf; Hsiao, Yu-Yun; Niu, Shan-Ce; Wang, Jie-Yu; Lin, Yao-Cheng; Xu, Qing; Chen, Li-Jun; Yoshida, Kouki; Fujiwara, Sumire; Wang, Zhi-Wen; Zhang, Yong-Qiang; Mitsuda, Nobutaka; Wang, Meina; Liu, Guo-Hui; Pecoraro, Lorenzo; Huang, Hui-Xia; Xiao, Xin-Ju; Lin, Min; Wu, Xin-Yi; Wu, Wan-Lin; Chen, You-Yi; Chang, Song-Bin; Sakamoto, Shingo; Ohme-Takagi, Masaru; Yagi, Masafumi; Zeng, Si-Jin; Shen, Ching-Yu; Yeh, Chuan-Ming; Luo, Yi-Bo; Tsai, Wen-Chieh; Van de Peer, Yves; Liu, Zhong-Jian

2017-09-21

Constituting approximately 10% of flowering plant species, orchids (Orchidaceae) display unique flower morphologies, possess an extraordinary diversity in lifestyle, and have successfully colonized almost every habitat on Earth. Here we report the draft genome sequence of Apostasia shenzhenica, a representative of one of two genera that form a sister lineage to the rest of the Orchidaceae, providing a reference for inferring the genome content and structure of the most recent common ancestor of all extant orchids and improving our understanding of their origins and evolution. In addition, we present transcriptome data for representatives of Vanilloideae, Cypripedioideae and Orchidoideae, and novel third-generation genome data for two species of Epidendroideae, covering all five orchid subfamilies. A. shenzhenica shows clear evidence of a whole-genome duplication, which is shared by all orchids and occurred shortly before their divergence. Comparisons between A. shenzhenica and other orchids and angiosperms also permitted the reconstruction of an ancestral orchid gene toolkit. We identify new gene families, gene family expansions and contractions, and changes within MADS-box gene classes, which control a diverse suite of developmental processes, during orchid evolution. This study sheds new light on the genetic mechanisms underpinning key orchid innovations, including the development of the labellum and gynostemium, pollinia, and seeds without endosperm, as well as the evolution of epiphytism; reveals relationships between the Orchidaceae subfamilies; and helps clarify the evolutionary history of orchids within the angiosperms.

Cretaceous flowers of Nymphaeaceae and implications for complex insect entrapment pollination mechanisms in early angiosperms.

PubMed

Gandolfo, M A; Nixon, K C; Crepet, W L

2004-05-25

Based on recent molecular systematics studies, the water lily lineage (Nymphaeales) provides an important key to understanding ancestral angiosperm morphology and is of considerable interest in the context of angiosperm origins. Therefore, the fossil record of Nymphaeales potentially provides evidence on both the timing and nature of diversification of one of the earliest clades of flowering plants. Recent fossil evidence of Turonian age (approximately 90 million years B.P.) includes fossil flowers with characters that, upon rigorous analysis, firmly place them within Nymphaeaceae. Unequivocally the oldest floral record of the Nymphaeales, these fossils are closely related to the modern Nymphaealean genera Victoria (the giant Amazon water lily) and Euryale. Although the fossils are much smaller than their modern relatives, the precise and dramatic correspondence between the fossil floral morphology and that of modern Victoria flowers suggests that beetle entrapment pollination was present in the earliest part of the Late Cretaceous.

Transcriptional signatures of ancient floral developmental genetics in avocado (Persea americana; Lauraceae).

PubMed

Chanderbali, André S; Albert, Victor A; Leebens-Mack, Jim; Altman, Naomi S; Soltis, Douglas E; Soltis, Pamela S

2009-06-02

The debate on the origin and evolution of flowers has recently entered the field of developmental genetics, with focus on the design of the ancestral floral regulatory program. Flowers can differ dramatically among angiosperm lineages, but in general, male and female reproductive organs surrounded by a sterile perianth of sepals and petals constitute the basic floral structure. However, the basal angiosperm lineages exhibit spectacular diversity in the number, arrangement, and structure of floral organs, whereas the evolutionarily derived monocot and eudicot lineages share a far more uniform floral ground plan. Here we show that broadly overlapping transcriptional programs characterize the floral transcriptome of the basal angiosperm Persea americana (avocado), whereas floral gene expression domains are considerably more organ specific in the model eudicot Arabidopsis thaliana. Our findings therefore support the "fading borders" model for organ identity determination in basal angiosperm flowers and extend it from the action of regulatory genes to downstream transcriptional programs. Furthermore, the declining expression of components of the staminal transcriptome in central and peripheral regions of Persea flowers concurs with elements of a previous hypothesis for developmental regulation in a gymnosperm "floral progenitor." Accordingly, in contrast to the canalized organ-specific regulatory apparatus of Arabidopsis, floral development may have been originally regulated by overlapping transcriptional cascades with fading gradients of influence from focal to bordering organs.

The Rise of Flowering Plants and Land Surface Physics: The Cretaceous and Eocene Were Different

NASA Astrophysics Data System (ADS)

Upchurch, G. R.; Feild, T.

2010-12-01

The Cretaceous and Eocene have served as the poster children of past greenhouse climates. One difference between the two time periods is that angiosperms (flowering plants) underwent a major diversification and rise to dominance during the mid-Cretaceous to Paleocene. Flowering plants differ from all other living and fossil plants in having significantly higher rates of transpiration and photosynthesis, which in modern leaves correlate with the density of venation (Dv), a feature that can be measured directly from fossils. This increase in Dv, coupled with an increase in the abundance of angiosperms, is thought to have had major impact on the climate system. This is, in part, because transpiration plays an important role in determining the ratio of sensible to latent heat flux from the land surface and in determining precipitation rate in regions such as the equatorial rainforest. Analysis of Dv in fossil leaves indicates two phases of increase in transpiration rate for angiosperms during the Cretaceous-Paleocene. The oldest known angiosperms (Aptian-early Albian) have a low Dv characteristic of extant and fossil ferns and gymnosperms. At this time angiosperms are low-stature plants of minor importance in terms of relative abundance and diversity (<5%). The first phase of Dv increase occurs during the Late Albian to Cenomanian, where average Dv is 40% greater than that of conifers and ferns, and maximum Dv reaches levels characteristic of many trees from the temperate zone. This first phase coincides with the first local dominance of angiosperms, the first occurrence of moderate to large angiosperm trees (up to 1 m in diameter) , and the first common occurrence of angiosperms in the Arctic. The second phase of Dv increase occurs during the Maastrichtian to Paleocene, where average Dv reaches levels characteristic of modern tropical forests and maximum Dv reaches the level found in highly productive modern vegetation. This second phase coincides with the rise to dominance of angiosperms in regional vegetation, a corresponding decline of conifers and ferns, and the modernization of hydraulic architecture in angiosperm wood. The full implications of these changes in land cover have yet to be explored with Earth System models, especially outside the tropics. However, under similar LAI and pCO2, Cretaceous vegetation would have made a greater contribution to global warming than Eocene vegetation through greater sensible heating of the land surface and possibly reduced liquid clouds due to decreased transpiration.

LTR Retrotransposons Show Low Levels of Unequal Recombination and High Rates of Intraelement Gene Conversion in Large Plant Genomes

PubMed Central

Cossu, Rosa Maria; Casola, Claudio; Giacomello, Stefania; Vidalis, Amaryllis

2017-01-01

Abstract The accumulation and removal of transposable elements (TEs) is a major driver of genome size evolution in eukaryotes. In plants, long terminal repeat (LTR) retrotransposons (LTR-RTs) represent the majority of TEs and form most of the nuclear DNA in large genomes. Unequal recombination (UR) between LTRs leads to removal of intervening sequence and formation of solo-LTRs. UR is a major mechanism of LTR-RT removal in many angiosperms, but our understanding of LTR-RT-associated recombination within the large, LTR-RT-rich genomes of conifers is quite limited. We employ a novel read-based methodology to estimate the relative rates of LTR-RT-associated UR within the genomes of four conifer and seven angiosperm species. We found the lowest rates of UR in the largest genomes studied, conifers and the angiosperm maize. Recombination may also resolve as gene conversion, which does not remove sequence, so we analyzed LTR-RT-associated gene conversion events (GCEs) in Norway spruce and six angiosperms. Opposite the trend for UR, we found the highest rates of GCEs in Norway spruce and maize. Unlike previous work in angiosperms, we found no evidence that rates of UR correlate with retroelement structural features in the conifers, suggesting that another process is suppressing UR in these species. Recent results from diverse eukaryotes indicate that heterochromatin affects the resolution of recombination, by favoring gene conversion over crossing-over, similar to our observation of opposed rates of UR and GCEs. Control of LTR-RT proliferation via formation of heterochromatin would be a likely step toward large genomes in eukaryotes carrying high LTR-RT content. PMID:29228262

Missing links: the genetic architecture of flowers [correction of flower] and floral diversification.

PubMed

Soltis, Douglas E; Soltis, Pamela S; Albert, Victor A; Oppenheimer, David G; dePamphilis, Claude W; Ma, Hong; Frohlich, Michael W; Theissen, Günter

2002-01-01

To understand the genetic architecture of floral development, including the origin and subsequent diversification of the flower, data are needed not only for a few model organisms but also for gymnosperms, basal angiosperm lineages and early-diverging eudicots. We must link what is known about derived model plants such as Arabidopsis, snapdragon and maize with other angiosperms. To this end, we suggest a massive evolutionary genomics effort focused on the identification and expression patterns of floral genes and elucidation of their expression patterns in 'missing-link' taxa differing in the arrangement, number and organization of floral parts.

Crown Group Lejeuneaceae and Pleurocarpous Mosses in Early Eocene (Ypresian) Indian Amber.

PubMed

Heinrichs, Jochen; Scheben, Armin; Bechteler, Julia; Lee, Gaik Ee; Schäfer-Verwimp, Alfons; Hedenäs, Lars; Singh, Hukam; Pócs, Tamás; Nascimbene, Paul C; Peralta, Denilson F; Renner, Matt; Schmidt, Alexander R

2016-01-01

Cambay amber originates from the warmest period of the Eocene, which is also well known for the appearance of early angiosperm-dominated megathermal forests. The humid climate of these forests may have triggered the evolution of epiphytic lineages of bryophytes; however, early Eocene fossils of bryophytes are rare. Here, we present evidence for lejeuneoid liverworts and pleurocarpous mosses in Cambay amber. The preserved morphology of the moss fossil is inconclusive for a detailed taxonomic treatment. The liverwort fossil is, however, distinctive; its zig-zagged stems, suberect complicate-bilobed leaves, large leaf lobules, and small, deeply bifid underleaves suggest a member of Lejeuneaceae subtribe Lejeuneinae (Harpalejeunea, Lejeunea, Microlejeunea). We tested alternative classification possibilities by conducting divergence time estimates based on DNA sequence variation of Lejeuneinae using the age of the fossil for corresponding age constraints. Consideration of the fossil as a stem group member of Microlejeunea or Lejeunea resulted in an Eocene to Late Cretaceous age of the Lejeuneinae crown group. This reconstruction is in good accordance with published divergence time estimates generated without the newly presented fossil evidence. Balancing available evidence, we describe the liverwort fossil as the extinct species Microlejeunea nyiahae, representing the oldest crown group fossil of Lejeuneaceae.

Long-Proboscid Flies as Pollinators of Cretaceous Gymnosperms.

PubMed

Peñalver, Enrique; Arillo, Antonio; Pérez-de la Fuente, Ricardo; Riccio, Mark L; Delclòs, Xavier; Barrón, Eduardo; Grimaldi, David A

2015-07-20

The great evolutionary success of angiosperms has traditionally been explained, in part, by the partnership of these plants with insect pollinators. The main approach to understanding the origins of this pervasive relationship has been study of the pollinators of living cycads, gnetaleans, and basal angiosperms. Among the most morphologically specialized living pollinators are diverse, long-proboscid flies. Early such flies include the brachyceran family Zhangsolvidae, previously known only as compression fossils from the Early Cretaceous of China and Brazil. It belongs to the infraorder Stratiomyomorpha, a group that includes the flower-visiting families Xylomyidae and Stratiomyidae. New zhangsolvid specimens in amber from Spain (ca. 105 mega-annum [Ma]) and Myanmar (100 Ma) reveal a detailed proboscis structure adapted to nectivory. Pollen clumped on a specimen from Spain is Exesipollenites, attributed to a Mesozoic gymnosperm, most likely the Bennettitales. Late Mesozoic scorpionflies with a long proboscis have been proposed as specialized pollinators of various extinct gymnosperms, but pollen has never been observed on or in their bodies. The new discovery is a very rare co-occurrence of pollen with its insect vector and provides substantiating evidence that other long-proboscid Mesozoic insects were gymnosperm pollinators. Evidence is thus now gathering that visitors and probable pollinators of early anthophytes, or seed plants, involved some insects with highly specialized morphological adaptations, which has consequences for interpreting the reproductive modes of Mesozoic gymnosperms and the significance of insect pollination in angiosperm success. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evolution of AGL6-like MADS Box Genes in Grasses (Poaceae): Ovule Expression Is Ancient and Palea Expression Is New[W][OA

PubMed Central

Reinheimer, Renata; Kellogg, Elizabeth A.

2009-01-01

AGAMOUS-like6 (AGL6) genes encode MIKC-type MADS box transcription factors and are closely related to SEPALLATA and AP1/FUL-like genes. Here, we focus on the molecular evolution and expression of the AGL6-like genes in grasses. We have found that AGL6-like genes are expressed in ovules, lodicules (second whorl floral organs), paleas (putative first whorl floral organs), and floral meristems. Each of these expression domains was acquired at a different time in evolution, indicating that each represents a distinct function of the gene product and that the AGL6-like genes are pleiotropic. Expression in the inner integument of the ovule appears to be an ancient expression pattern corresponding to the expression of the gene in the megasporangium and integument in gymnosperms. Expression in floral meristems appears to have been acquired in the angiosperms and expression in second whorl organs in monocots. Early in grass evolution, AGL6-like orthologs acquired a new expression domain in the palea. Stamen expression is variable. Most grasses have a single AGL6-like gene (orthologous to the rice [Oryza sativa] gene MADS6). However, rice and other species of Oryza have a second copy (orthologous to rice MADS17) that appears to be the result of an ancient duplication. PMID:19749151

Studies of angiospermous wood in Australian brown coal by nuclear magnetic resonance and analytical pyrolysis: new insights into the early coalification process

USGS Publications Warehouse

Hatcher, P.G.; Wilson, M.A.; Vassallo, A.M.; Lerch, H. E.

1989-01-01

Many Tertiary coals contain abundant fossilized remains of angiosperms, which commonly dominated the ancient peat-swamp environments; modern analogs of such swamps can be found in tropical and subtropical regions of the world. Comparisons of angiospermous wood from Australian brown coal with similar wood buried in modern peat swamps of Indonesia have provided some new insights into coalification reactions. These comparisons were made by using solid-state 13C nuclear magnetic resonance (NMR) techniques and pyrolsis-gas chromatography-mass spectrometry (py-gc-ms). These two modern techniques are especially suited for detailed structural evaluation of the complex macromolecules in coal. The earliest transformation (peatification) of organic matter in angiospermous wood is the degradation and removal of cellulosic components and the concomitant selective preservation of lignin-derived components. The angiospermous lignin that becomes enriched in wood as a result of cellulose degradation also is modified by coalification reactions; this modification, however, does not involve degradation and removal of the lignin. Rather, the early coalification process transforms the lignin phenols (guiacyl and syringyl) to eventually yield the aromatic structures typically found in brown coal. One such transformation, which is determined from NMR data, involves the cleavage of aryl-ether bonds that link guaiacyl and syringyl units in lignin, and this transformation leads to the formation of free lignin phenols. Another transformation, which is also determined from the NMR data, involves the loss of methoxyl groups, probably via demethylation, to produce catechol-like structures. Coincident with ether-cleavage and demethylation, the aromatic rings derived from lignin phenols become more carbon-substituted and cross linked, as determined by dipolar-dephasing NMR studies. This cross linking is probably responsible for preventing the lignin phenols, which are freed from the lignin macromolecule by ether cleavage, from being removed from the coal by dissolution. Pyrolysis data suggest that the syringyl units are altered more readily than are guaiacyl units, and this difference in resistance leads to an enrichment of the guaiacyl units in fossil angiospermous woods. Many of the coalification reactions noted above occur to some degree in all angiospermous fossil wood examined; however, some significant differences are observed in the degree of coalification of the fossil wood samples from the same burial depth in the brown coal. These differences indicate that the depth and duration of burial are probably not entirely responsible for the variations in degree of coalification. Different rates of degradation in peat may have contributed to the variations in the apparent degree of coalification; some woods may have been altered more rapidly at the peat stage than others. Although preliminary, this systematic study of botanically related wood in peat and coal results in a more detailed differentiation of coalification reactions than have previous investigations. The combined use of solid-state 13C NMR and py-gc-ms has facilitated this detailed insight into the coalification of angiospermous wood. ?? 1989.

Ferns: the missing link in shoot evolution and development

PubMed Central

Plackett, Andrew R. G.; Di Stilio, Verónica S.; Langdale, Jane A.

2015-01-01

Shoot development in land plants is a remarkably complex process that gives rise to an extreme diversity of forms. Our current understanding of shoot developmental mechanisms comes almost entirely from studies of angiosperms (flowering plants), the most recently diverged plant lineage. Shoot development in angiosperms is based around a layered multicellular apical meristem that produces lateral organs and/or secondary meristems from populations of founder cells at its periphery. In contrast, non-seed plant shoots develop from either single apical initials or from a small population of morphologically distinct apical cells. Although developmental and molecular information is becoming available for non-flowering plants, such as the model moss Physcomitrella patens, making valid comparisons between highly divergent lineages is extremely challenging. As sister group to the seed plants, the monilophytes (ferns and relatives) represent an excellent phylogenetic midpoint of comparison for unlocking the evolution of shoot developmental mechanisms, and recent technical advances have finally made transgenic analysis possible in the emerging model fern Ceratopteris richardii. This review compares and contrasts our current understanding of shoot development in different land plant lineages with the aim of highlighting the potential role that the fern C. richardii could play in shedding light on the evolution of underlying genetic regulatory mechanisms. PMID:26594222

Evolution of Genome Size and Complexity in Pinus

PubMed Central

Morse, Alison M.; Peterson, Daniel G.; Islam-Faridi, M. Nurul; Smith, Katherine E.; Magbanua, Zenaida; Garcia, Saul A.; Kubisiak, Thomas L.; Amerson, Henry V.; Carlson, John E.; Nelson, C. Dana; Davis, John M.

2009-01-01

Background Genome evolution in the gymnosperm lineage of seed plants has given rise to many of the most complex and largest plant genomes, however the elements involved are poorly understood. Methodology/Principal Findings Gymny is a previously undescribed retrotransposon family in Pinus that is related to Athila elements in Arabidopsis. Gymny elements are dispersed throughout the modern Pinus genome and occupy a physical space at least the size of the Arabidopsis thaliana genome. In contrast to previously described retroelements in Pinus, the Gymny family was amplified or introduced after the divergence of pine and spruce (Picea). If retrotransposon expansions are responsible for genome size differences within the Pinaceae, as they are in angiosperms, then they have yet to be identified. In contrast, molecular divergence of Gymny retrotransposons together with other families of retrotransposons can account for the large genome complexity of pines along with protein-coding genic DNA, as revealed by massively parallel DNA sequence analysis of Cot fractionated genomic DNA. Conclusions/Significance Most of the enormous genome complexity of pines can be explained by divergence of retrotransposons, however the elements responsible for genome size variation are yet to be identified. Genomic resources for Pinus including those reported here should assist in further defining whether and how the roles of retrotransposons differ in the evolution of angiosperm and gymnosperm genomes. PMID:19194510

Novelties of the flowering plant pollen tube underlie diversification of a key life history stage

PubMed Central

Williams, Joseph H.

2008-01-01

The origin and rapid diversification of flowering plants has puzzled evolutionary biologists, dating back to Charles Darwin. Since that time a number of key life history and morphological traits have been proposed as developmental correlates of the extraordinary diversity and ecological success of angiosperms. Here, I identify several innovations that were fundamental to the evolutionary lability of angiosperm reproduction, and hence to their diversification. In gymnosperms pollen reception must be near the egg largely because sperm swim or are transported by pollen tubes that grow at very slow rates (< ≈20 μm/h). In contrast, pollen tube growth rates of taxa in ancient angiosperm lineages (Amborella, Nuphar, and Austrobaileya) range from ≈80 to 600 μm/h. Comparative analyses point to accelerated pollen tube growth rate as a critical innovation that preceded the origin of the true closed carpel, long styles, multiseeded ovaries, and, in monocots and eudicots, much faster pollen tube growth rates. Ancient angiosperm pollen tubes all have callosic walls and callose plugs (in contrast, no gymnosperms have these features). The early association of the callose-walled growth pattern with accelerated pollen tube growth rate underlies a striking repeated pattern of faster and longer-distance pollen tube growth often within solid pathways in phylogenetically derived angiosperms. Pollen tube innovations are a key component of the spectacular diversification of carpel (flower and fruit) form and reproductive cycles in flowering plants. PMID:18678915

Gravitropisms and reaction woods of forest trees - evolution, functions and mechanisms

Treesearch

Andrew Groover

2016-01-01

The woody stems of trees perceive gravity to determine their orientation, and can produce reaction woods to reinforce or change their position. Together, graviperception and reaction woods play fundamental roles in tree architecture, posture control, and reorientation of stems displaced by wind or other environmental forces. Angiosperms and gymnosperms have...

The within-tree distribution of caterpillar mines

Treesearch

Michail V. Kozlov; Yulia G. Koricheva

1991-01-01

Lepidoptera is a relatively young order and one of the largest and most diverse in the Insecta. The first paleontological vestiges of moths were found among lower Jurassic deposits, but the most intensive lepidopterous evolution (mainly in suborder Ditrysia = Papilionina) took place in the mid-Cretaceous Period, coterminous with the expansion of angiosperm plants. The...

Analysis of the WUSCHEL-RELATED HOMEOBOX gene family in Pinus pinaster: New insights into the gene family evolution.

PubMed

Alvarez, José M; Bueno, Natalia; Cañas, Rafael A; Avila, Concepción; Cánovas, Francisco M; Ordás, Ricardo J

2018-02-01

WUSCHEL-RELATED HOMEOBOX (WOX) genes are key players controlling stem cells in plants and can be divided into three clades according to the time of their appearance during plant evolution. Our knowledge of stem cell function in vascular plants other than angiosperms is limited, they separated from gymnosperms ca 300 million years ago and their patterning during embryogenesis differs significantly. For this reason, we have used the model gymnosperm Pinus pinaster to identify WOX genes and perform a thorough analysis of their gene expression patterns. Using transcriptomic data from a comprehensive range of tissues and stages of development we have shown three major outcomes: that the P. pinaster genome encodes at least fourteen members of the WOX family spanning all the major clades, that the genome of gymnosperms contains a WOX gene with no homologues in angiosperms representing a transitional stage between intermediate- and WUS-clade proteins, and that we can detect discrete WUS and WOX5 transcripts for the first time in a gymnosperm. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

The Origin of Floral Organ Identity Quartets

PubMed Central

van Mourik, Hilda; Kaufmann, Kerstin

2017-01-01

The origin of flowers has puzzled plant biologists ever since Darwin referred to their sudden appearance in the fossil record as an abominable mystery. Flowers are considered to be an assembly of protective, attractive, and reproductive male and female leaf-like organs. Their origin cannot be understood by a morphological comparison to gymnosperms, their closest relatives, which develop separate male or female cones. Despite these morphological differences, gymnosperms and angiosperms possess a similar genetic toolbox consisting of phylogenetically related MADS domain proteins. Using ancestral MADS domain protein reconstruction, we trace the evolution of organ identity quartets along the stem lineage of crown angiosperms. We provide evidence that current floral quartets specifying male organ identity, which consist of four types of subunits, evolved from ancestral complexes of two types of subunits through gene duplication and integration of SEPALLATA proteins just before the origin of flowering plants. Our results suggest that protein interaction changes underlying this compositional shift were the result of a gradual and reversible evolutionary trajectory. Modeling shows that such compositional changes may have facilitated the evolution of the perfect, bisexual flower. PMID:28100708

The Origin of Floral Organ Identity Quartets.

PubMed

Ruelens, Philip; Zhang, Zhicheng; van Mourik, Hilda; Maere, Steven; Kaufmann, Kerstin; Geuten, Koen

2017-02-01

The origin of flowers has puzzled plant biologists ever since Darwin referred to their sudden appearance in the fossil record as an abominable mystery. Flowers are considered to be an assembly of protective, attractive, and reproductive male and female leaf-like organs. Their origin cannot be understood by a morphological comparison to gymnosperms, their closest relatives, which develop separate male or female cones. Despite these morphological differences, gymnosperms and angiosperms possess a similar genetic toolbox consisting of phylogenetically related MADS domain proteins. Using ancestral MADS domain protein reconstruction, we trace the evolution of organ identity quartets along the stem lineage of crown angiosperms. We provide evidence that current floral quartets specifying male organ identity, which consist of four types of subunits, evolved from ancestral complexes of two types of subunits through gene duplication and integration of SEPALLATA proteins just before the origin of flowering plants. Our results suggest that protein interaction changes underlying this compositional shift were the result of a gradual and reversible evolutionary trajectory. Modeling shows that such compositional changes may have facilitated the evolution of the perfect, bisexual flower. © 2017 American Society of Plant Biologists. All rights reserved.

New fossil insect order Permopsocida elucidates major radiation and evolution of suction feeding in hemimetabolous insects (Hexapoda: Acercaria)

PubMed Central

Huang, Di-Ying; Bechly, Günter; Nel, Patricia; Engel, Michael S.; Prokop, Jakub; Azar, Dany; Cai, Chen-Yang; van de Kamp, Thomas; Staniczek, Arnold H.; Garrouste, Romain; Krogmann, Lars; dos Santos Rolo, Tomy; Baumbach, Tilo; Ohlhoff, Rainer; Shmakov, Alexey S.; Bourgoin, Thierry; Nel, André

2016-01-01

With nearly 100,000 species, the Acercaria (lice, plant lices, thrips, bugs) including number of economically important species is one of the most successful insect lineages. However, its phylogeny and evolution of mouthparts among other issues remain debatable. Here new methods of preparation permitted the comprehensive anatomical description of insect inclusions from mid-Cretaceous Burmese amber in astonishing detail. These “missing links” fossils, attributed to a new order Permopsocida, provide crucial evidence for reconstructing the phylogenetic relationships in the Acercaria, supporting its monophyly, and questioning the position of Psocodea as sister group of holometabolans in the most recent phylogenomic study. Permopsocida resolves as sister group of Thripida + Hemiptera and represents an evolutionary link documenting the transition from chewing to piercing mouthparts in relation to suction feeding. Identification of gut contents as angiosperm pollen documents an ecological role of Permopsocida as early pollen feeders with relatively unspecialized mouthparts. This group existed for 185 million years, but has never been diverse and was superseded by new pollenivorous pollinators during the Cretaceous co-evolution of insects and flowers. The key innovation of suction feeding with piercing mouthparts is identified as main event that triggered the huge post-Carboniferous radiation of hemipterans, and facilitated the spreading of pathogenic vectors. PMID:26961785

New fossil insect order Permopsocida elucidates major radiation and evolution of suction feeding in hemimetabolous insects (Hexapoda: Acercaria)

NASA Astrophysics Data System (ADS)

Huang, Di-Ying; Bechly, Günter; Nel, Patricia; Engel, Michael S.; Prokop, Jakub; Azar, Dany; Cai, Chen-Yang; van de Kamp, Thomas; Staniczek, Arnold H.; Garrouste, Romain; Krogmann, Lars; Dos Santos Rolo, Tomy; Baumbach, Tilo; Ohlhoff, Rainer; Shmakov, Alexey S.; Bourgoin, Thierry; Nel, André

2016-03-01

With nearly 100,000 species, the Acercaria (lice, plant lices, thrips, bugs) including number of economically important species is one of the most successful insect lineages. However, its phylogeny and evolution of mouthparts among other issues remain debatable. Here new methods of preparation permitted the comprehensive anatomical description of insect inclusions from mid-Cretaceous Burmese amber in astonishing detail. These “missing links” fossils, attributed to a new order Permopsocida, provide crucial evidence for reconstructing the phylogenetic relationships in the Acercaria, supporting its monophyly, and questioning the position of Psocodea as sister group of holometabolans in the most recent phylogenomic study. Permopsocida resolves as sister group of Thripida + Hemiptera and represents an evolutionary link documenting the transition from chewing to piercing mouthparts in relation to suction feeding. Identification of gut contents as angiosperm pollen documents an ecological role of Permopsocida as early pollen feeders with relatively unspecialized mouthparts. This group existed for 185 million years, but has never been diverse and was superseded by new pollenivorous pollinators during the Cretaceous co-evolution of insects and flowers. The key innovation of suction feeding with piercing mouthparts is identified as main event that triggered the huge post-Carboniferous radiation of hemipterans, and facilitated the spreading of pathogenic vectors.

New fossil insect order Permopsocida elucidates major radiation and evolution of suction feeding in hemimetabolous insects (Hexapoda: Acercaria).

PubMed

Huang, Di-Ying; Bechly, Günter; Nel, Patricia; Engel, Michael S; Prokop, Jakub; Azar, Dany; Cai, Chen-Yang; van de Kamp, Thomas; Staniczek, Arnold H; Garrouste, Romain; Krogmann, Lars; Dos Santos Rolo, Tomy; Baumbach, Tilo; Ohlhoff, Rainer; Shmakov, Alexey S; Bourgoin, Thierry; Nel, André

2016-03-10

With nearly 100,000 species, the Acercaria (lice, plant lices, thrips, bugs) including number of economically important species is one of the most successful insect lineages. However, its phylogeny and evolution of mouthparts among other issues remain debatable. Here new methods of preparation permitted the comprehensive anatomical description of insect inclusions from mid-Cretaceous Burmese amber in astonishing detail. These "missing links" fossils, attributed to a new order Permopsocida, provide crucial evidence for reconstructing the phylogenetic relationships in the Acercaria, supporting its monophyly, and questioning the position of Psocodea as sister group of holometabolans in the most recent phylogenomic study. Permopsocida resolves as sister group of Thripida + Hemiptera and represents an evolutionary link documenting the transition from chewing to piercing mouthparts in relation to suction feeding. Identification of gut contents as angiosperm pollen documents an ecological role of Permopsocida as early pollen feeders with relatively unspecialized mouthparts. This group existed for 185 million years, but has never been diverse and was superseded by new pollenivorous pollinators during the Cretaceous co-evolution of insects and flowers. The key innovation of suction feeding with piercing mouthparts is identified as main event that triggered the huge post-Carboniferous radiation of hemipterans, and facilitated the spreading of pathogenic vectors.

Gravity and land plant evolution: experimental induction of lignification by simulated hypergravity and water stress.

PubMed

Chen, N; Siegel, S M; Siegel, B Z

1980-01-01

The ability to lignify cell walls has long been associated with the upright condition and sometimes massive body of the land plant, and gravitational regulation of lignification has been demonstrated by clinostat/centrifuge techniques. Previous centrifuge experiments were conducted using plants in the early stages of growth, hence already programmed for immediate lignification. Elodea, an aquatic Angiosperm long believed to be incapable of lignification synthesizes lignin or lignin-like phenolics during 6 days incubation at 80 g . Yields in some cases exceeded stationary controls by as much as 300%. Supporting data were obtained using bean cotyledons. Exposure to 80 g induced lignification in extra-vascular tissue along with vascular lignin deposits. The loss of a buoyant medium also deprived early land plants of unlimited water: the lignin content in cucumber seedlings grown in water is reduced 50% or more relative to pot grown plants but water stress elevates lignin content as much as 100%. This suggests that the water status of the land environment may have provided a "backup" or "reinforcement" signal for an adaptive axial support system.

Floral associations of cyclocephaline scarab beetles.

PubMed

Moore, Matthew Robert; Jameson, Mary Liz

2013-01-01

The scarab beetle tribe Cyclocephalini (Coleoptera: Scarabaeidae: Dynastinae) is the second largest tribe of rhinoceros beetles, with nearly 500 described species. This diverse group is most closely associated with early diverging angiosperm groups (the family Nymphaeaceae, magnoliid clade, and monocots), where they feed, mate, and receive the benefit of thermal rewards from the host plant. Cyclocephaline floral association data have never been synthesized, and a comprehensive review of this ecological interaction was necessary to promote research by updating nomenclature, identifying inconsistencies in the data, and reporting previously unpublished data. Based on the most specific data, at least 97 cyclocephaline beetle species have been reported from the flowers of 58 plant genera representing 17 families and 15 orders. Thirteen new cyclocephaline floral associations are reported herein. Six cyclocephaline and 25 plant synonyms were reported in the literature and on beetle voucher specimen labels, and these were updated to reflect current nomenclature. The valid names of three unavailable plant host names were identified. We review the cyclocephaline floral associations with respect to inferred relationships of angiosperm orders. Ten genera of cyclocephaline beetles have been recorded from flowers of early diverging angiosperm groups. In contrast, only one genus, Cyclocephala, has been recorded from dicot flowers. Cyclocephaline visitation of dicot flowers is limited to the New World, and it is unknown whether this is evolutionary meaningful or the result of sampling bias and incomplete data. The most important areas for future research include: (1) elucidating the factors that attract cyclocephalines to flowers including floral scent chemistry and thermogenesis, (2) determining whether cyclocephaline dicot visitation is truly limited to the New World, and (3) inferring evolutionary relationships within the Cyclocephalini to rigorously test vicarance hypotheses, host plant shifts, and mutualisms with angiosperms.

Floral Associations of Cyclocephaline Scarab Beetles

PubMed Central

Moore, Matthew Robert; Jameson, Mary Liz

2013-01-01

The scarab beetle tribe Cyclocephalini (Coleoptera: Scarabaeidae: Dynastinae) is the second largest tribe of rhinoceros beetles, with nearly 500 described species. This diverse group is most closely associated with early diverging angiosperm groups (the family Nymphaeaceae, magnoliid clade, and monocots), where they feed, mate, and receive the benefit of thermal rewards from the host plant. Cyclocephaline floral association data have never been synthesized, and a comprehensive review of this ecological interaction was necessary to promote research by updating nomenclature, identifying inconsistencies in the data, and reporting previously unpublished data. Based on the most specific data, at least 97 cyclocephaline beetle species have been reported from the flowers of 58 plant genera representing 17 families and 15 orders. Thirteen new cyclocephaline floral associations are reported herein. Six cyclocephaline and 25 plant synonyms were reported in the literature and on beetle voucher specimen labels, and these were updated to reflect current nomenclature. The valid names of three unavailable plant host names were identified. We review the cyclocephaline floral associations with respect to inferred relationships of angiosperm orders. Ten genera of cyclocephaline beetles have been recorded from flowers of early diverging angiosperm groups. In contrast, only one genus, Cyclocephala, has been recorded from dicot flowers. Cyclocephaline visitation of dicot flowers is limited to the New World, and it is unknown whether this is evolutionary meaningful or the result of sampling bias and incomplete data. The most important areas for future research include: 1) elucidating the factors that attract cyclocephalines to flowers including floral scent chemistry and thermogenesis, 2) determining whether cyclocephaline dicot visitation is truly limited to the New World, and 3) inferring evolutionary relationships within the Cyclocephalini to rigorously test vicarance hypotheses, host plant shifts, and mutualisms with angiosperms. PMID:24738782

Diversification of C(4) grasses (Poaceae) does not coincide with their ecological dominance.

PubMed

Bouchenak-Khelladi, Yanis; Slingsby, Jasper A; Verboom, G Anthony; Bond, William J

2014-02-01

The radiation of a lineage and its rise to ecological dominance are distinct phenomena and driven by different processes. For example, paleoecological data has been used to show that the Cretaceous angiosperm radiation did not coincide with their rise to dominance. Using a phylogenetic approach, we here explored the evolution of C4 grasses and evaluated whether the diversification of this group and its rise to ecological dominance in the late Miocene were decoupled. We assembled a matrix including 675 grass species of the PACMAD clade and 2784 characters (ITS and ndhF) to run a molecular dating analysis using three fossils as reference calibrations. We coded species as C3 vs. C4 and reconstructed ancestral states under maximum likelihood. We used the program BiSSE to test whether rates of diversification are correlated with photosynthetic pathway and whether the radiation of C4 lineages preceded or coincided with their rise to ecological dominance from ∼10 Ma. C4 grass lineages first originated around 35 Ma at the time of the Eocene-Oligocene transition. Accelerated diversification of C4 lineages did not coincide with their rise to ecological dominance. C4-dominated grasslands have expanded only since the Late Miocene and Pliocene. The initial diversification of their biotic elements can be tracked back as far as the Eocene-Oligocene transition. We suggest that shifts in taxonomic diversification and ecological dominance were stimulated by different factors, as in the case of the early angiosperms in the Cretaceous.

Darwin-Wallace Demons: survival of the fastest in populations of duckweeds and the evolutionary history of an enigmatic group of angiosperms.

PubMed

Kutschera, U; Niklas, K J

2015-01-01

In evolutionary biology, the term 'Darwinian fitness' refers to the lifetime reproductive success of an individual within a population of conspecifics. The idea of a 'Darwinian Demon' emerged from this concept and is defined here as an organism that commences reproduction almost immediately after birth, has a maximum fitness, and lives forever. It has been argued that duckweeds (sub-family Lemnoideae, order Alismatales), a group containing five genera and 34 species of small aquatic monocotyledonous plants with a reduced body plan, can be interpreted as examples of 'Darwinian Demons'. Here we focus on the species Spirodela polyrhiza (Great duckweed) and show that these miniaturised aquatic angiosperms display features that fit the definition of the hypothetical organism that we will call a 'Darwin-Wallace Demon' in recognition of the duel proponents of evolution by natural selection. A quantitative analysis (log-log bivariate plot of annual growth in dry biomass versus standing dry body mass of various green algae and land plants) revealed that duckweeds are thus far the most rapidly growing angiosperms in proportion to their body mass. In light of this finding, we discuss the disposable soma and metabolic optimising theories, summarise evidence for and against the proposition that the Lemnoideae (family Araceae) reflect an example of reductive evolution, and argue that, under real-world conditions (environmental constraints and other limitations), 'Darwin-Wallace Demons' cannot exist, although the concept remains useful in much the same way that the Hardy-Weinberg law does. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Two-Step Functional Innovation of the Stem-Cell Factors WUS/WOX5 during Plant Evolution.

PubMed

Zhang, Yuzhou; Jiao, Yue; Jiao, Hengwu; Zhao, Huabin; Zhu, Yu-Xian

2017-03-01

WUS and WOX5, which are expressed, respectively, in the organizing center (OC) and the quiescent center (QC), are essential for shoot/root apical stem-cell maintenance in flowering plants. However, little is known about how these stem-cell factors evolved their functions in flowering plants. Here, we show that the WUS/WOX5 proteins acquired two distinct capabilities by a two-step functional innovation process in the course of plant evolution. The first-step is the apical stem-cell maintenance activity of WUS/WOX5, which originated in the common ancestor of ferns and seed plants, as evidenced by the interspecies complementation experiments, showing that ectopic expression of fern Ceratopteris richardii WUS-like (CrWUL) surrounding OC/QC, or exclusive OC-/QC-expressed gymnosperms/angiosperms WUS/WOX5 in Arabidopsis wus-1 and wox5-1 mutants, could rescue their phenotypes. The second-step is the intercellular mobility that emerged in the common ancestor of seed plants after divergence from the ferns. Evidence for this includes confocal imaging of GFP fusion proteins, showing that WUS/WOX5 from seed plants, rather than from the fern CrWUL, can migrate into cells adjacent to the OC/QC. Evolutionary analysis showed that the WUS-like gene was duplicated into two copies prior to the divergence of gymnosperms/angiosperms. Then the two gene copies (WUS and WOX5) have undergone similar levels of purifying selection, which is consistent with their conserved functions in angiosperm shoot/root stem-cell maintenance and floral organ formation. Our results highlight the critical roles and the essential prerequisites that the two-step functional innovation of these genes performs and represents in the origin of flowering plants. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Stem hydraulic traits and leaf water-stress tolerance are co-ordinated with the leaf phenology of angiosperm trees in an Asian tropical dry karst forest

PubMed Central

Fu, Pei-Li; Jiang, Yan-Juan; Wang, Ai-Ying; Brodribb, Tim J.; Zhang, Jiao-Lin; Zhu, Shi-Dan; Cao, Kun-Fang

2012-01-01

Background and Aims The co-occurring of evergreen and deciduous angiosperm trees in Asian tropical dry forests on karst substrates suggests the existence of different water-use strategies among species. In this study it is hypothesized that the co-occurring evergreen and deciduous trees differ in stem hydraulic traits and leaf water relationships, and there will be correlated evolution in drought tolerance between leaves and stems. Methods A comparison was made of stem hydraulic conductivity, vulnerability curves, wood anatomy, leaf life span, leaf pressure–volume characteristics and photosynthetic capacity of six evergreen and six deciduous tree species co-occurring in a tropical dry karst forest in south-west China. The correlated evolution of leaf and stem traits was examined using both traditional and phylogenetic independent contrasts correlations. Key Results It was found that the deciduous trees had higher stem hydraulic efficiency, greater hydraulically weighted vessel diameter (Dh) and higher mass-based photosynthetic rate (Am); while the evergreen species had greater xylem-cavitation resistance, lower leaf turgor-loss point water potential (π0) and higher bulk modulus of elasticity. There were evolutionary correlations between leaf life span and stem hydraulic efficiency, Am, and dry season π0. Xylem-cavitation resistance was evolutionarily correlated with stem hydraulic efficiency, Dh, as well as dry season π0. Both wood density and leaf density were closely correlated with leaf water-stress tolerance and Am. Conclusions The results reveal the clear distinctions in stem hydraulic traits and leaf water-stress tolerance between the co-occurring evergreen and deciduous angiosperm trees in an Asian dry karst forest. A novel pattern was demonstrated linking leaf longevity with stem hydraulic efficiency and leaf water-stress tolerance. The results show the correlated evolution in drought tolerance between stems and leaves. PMID:22585930

Sex chromosomes in land plants.

PubMed

Ming, Ray; Bendahmane, Abdelhafid; Renner, Susanne S

2011-01-01

Sex chromosomes in land plants can evolve as a consequence of close linkage between the two sex determination genes with complementary dominance required to establish stable dioecious populations, and they are found in at least 48 species across 20 families. The sex chromosomes in hepatics, mosses, and gymnosperms are morphologically heteromorphic. In angiosperms, heteromorphic sex chromosomes are found in at least 19 species from 4 families, while homomorphic sex chromosomes occur in 20 species from 13 families. The prevalence of the XY system found in 44 out of 48 species may reflect the predominance of the evolutionary pathway from gynodioecy towards dioecy. All dioecious species have the potential to evolve sex chromosomes, and reversions back from dioecy to various forms of monoecy, gynodioecy, or androdioecy have also occurred. Such reversals may occur especially during the early stages of sex chromosome evolution before the lethality of the YY (or WW) genotype is established.

A phenol-enriched cuticle is ancestral to lignin evolution in land plants.

PubMed

Renault, Hugues; Alber, Annette; Horst, Nelly A; Basilio Lopes, Alexandra; Fich, Eric A; Kriegshauser, Lucie; Wiedemann, Gertrud; Ullmann, Pascaline; Herrgott, Laurence; Erhardt, Mathieu; Pineau, Emmanuelle; Ehlting, Jürgen; Schmitt, Martine; Rose, Jocelyn K C; Reski, Ralf; Werck-Reichhart, Danièle

2017-03-08

Lignin, one of the most abundant biopolymers on Earth, derives from the plant phenolic metabolism. It appeared upon terrestrialization and is thought critical for plant colonization of land. Early diverging land plants do not form lignin, but already have elements of its biosynthetic machinery. Here we delete in a moss the P450 oxygenase that defines the entry point in angiosperm lignin metabolism, and find that its pre-lignin pathway is essential for development. This pathway does not involve biochemical regulation via shikimate coupling, but instead is coupled with ascorbate catabolism, and controls the synthesis of the moss cuticle, which prevents desiccation and organ fusion. These cuticles share common features with lignin, cutin and suberin, and may represent the extant representative of a common ancestor. Our results demonstrate a critical role for the ancestral phenolic metabolism in moss erect growth and cuticle permeability, consistent with importance in plant adaptation to terrestrial conditions.

A phenol-enriched cuticle is ancestral to lignin evolution in land plants

PubMed Central

Renault, Hugues; Alber, Annette; Horst, Nelly A.; Basilio Lopes, Alexandra; Fich, Eric A.; Kriegshauser, Lucie; Wiedemann, Gertrud; Ullmann, Pascaline; Herrgott, Laurence; Erhardt, Mathieu; Pineau, Emmanuelle; Ehlting, Jürgen; Schmitt, Martine; Rose, Jocelyn K. C.; Reski, Ralf; Werck-Reichhart, Danièle

2017-01-01

Lignin, one of the most abundant biopolymers on Earth, derives from the plant phenolic metabolism. It appeared upon terrestrialization and is thought critical for plant colonization of land. Early diverging land plants do not form lignin, but already have elements of its biosynthetic machinery. Here we delete in a moss the P450 oxygenase that defines the entry point in angiosperm lignin metabolism, and find that its pre-lignin pathway is essential for development. This pathway does not involve biochemical regulation via shikimate coupling, but instead is coupled with ascorbate catabolism, and controls the synthesis of the moss cuticle, which prevents desiccation and organ fusion. These cuticles share common features with lignin, cutin and suberin, and may represent the extant representative of a common ancestor. Our results demonstrate a critical role for the ancestral phenolic metabolism in moss erect growth and cuticle permeability, consistent with importance in plant adaptation to terrestrial conditions. PMID:28270693

The effect of polyploidy and hybridization on the evolution of floral colour in Nicotiana (Solanaceae).

PubMed

McCarthy, Elizabeth W; Arnold, Sarah E J; Chittka, Lars; Le Comber, Steven C; Verity, Robert; Dodsworth, Steven; Knapp, Sandra; Kelly, Laura J; Chase, Mark W; Baldwin, Ian T; Kovařík, Aleš; Mhiri, Corinne; Taylor, Lin; Leitch, Andrew R

2015-06-01

Speciation in angiosperms can be accompanied by changes in floral colour that may influence pollinator preference and reproductive isolation. This study investigates whether changes in floral colour can accompany polyploid and homoploid hybridization, important processes in angiosperm evolution. Spectral reflectance of corolla tissue was examined for 60 Nicotiana (Solanaceae) accessions (41 taxa) based on spectral shape (corresponding to pigmentation) as well as bee and hummingbird colour perception in order to assess patterns of floral colour evolution. Polyploid and homoploid hybrid spectra were compared with those of their progenitors to evaluate whether hybridization has resulted in floral colour shifts. Floral colour categories in Nicotiana seem to have arisen multiple times independently during the evolution of the genus. Most younger polyploids displayed an unexpected floral colour, considering those of their progenitors, in the colour perception of at least one pollinator type, whereas older polyploids tended to resemble one or both of their progenitors. Floral colour evolution in Nicotiana is weakly constrained by phylogeny, and colour shifts do occur in association with both polyploid and homoploid hybrid divergence. Transgressive floral colour in N. tabacum has arisen by inheritance of anthocyanin pigmentation from its paternal progenitor while having a plastid phenotype like its maternal progenitor. Potentially, floral colour evolution has been driven by, or resulted in, pollinator shifts. However, those polyploids that are not sympatric (on a regional scale) with their progenitor lineages are typically not divergent in floral colour from them, perhaps because of a lack of competition for pollinators. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Evolution of Epiphytism and Fruit Traits Act Unevenly on the Diversification of the Species-Rich Genus Peperomia (Piperaceae)

PubMed Central

Frenzke, Lena; Goetghebeur, Paul; Neinhuis, Christoph; Samain, Marie-Stéphanie; Wanke, Stefan

2016-01-01

The species-rich genus Peperomia (Black Pepper relatives) is the only genus among early diverging angiosperms where epiphytism evolved. The majority of fruits of Peperomia release sticky secretions or exhibit hook-shaped appendages indicative of epizoochorous dispersal, which is in contrast to other flowering plants, where epiphytes are generally characterized by fruit morphological adaptations for anemochory or endozoochory. We investigate fruit characters using Cryo-SEM. Comparative phylogenetic analyses are applied for the first time to include life form and fruit character information to study diversification in Peperomia. Likelihood ratio tests uncover correlated character evolution. We demonstrate that diversification within Peperomia is not homogenous across its phylogeny, and that net diversification rates increase by twofold within the most species-rich subgenus. In contrast to former land plant studies that provide general evidence for increased diversification in epiphytic lineages, we demonstrate that the evolution of epiphytism within Peperomia predates the diversification shift. An epiphytic-dependent diversification is only observed for the background phylogeny. An elevated frequency of life form transitions between epiphytes and terrestrials and thus evolutionary flexibility of life forms is uncovered to coincide with the diversification shift. The evolution of fruits showing dispersal related structures is key to diversification in the foreground region of the phylogeny and postdates the evolution of epiphytism. We conclude that the success of Peperomia, measured in species numbers, is likely the result of enhanced vertical and horizontal dispersal ability and life form flexibility but not the evolution of epiphytism itself. PMID:27555851

If Dung Beetles (Scarabaeidae: Scarabaeinae) Arose in Association with Dinosaurs, Did They Also Suffer a Mass Co-Extinction at the K-Pg Boundary?

PubMed

Gunter, Nicole L; Weir, Tom A; Slipinksi, Adam; Bocak, Ladislav; Cameron, Stephen L

2016-01-01

The evolutionary success of beetles and numerous other terrestrial insects is generally attributed to co-radiation with flowering plants but most studies have focused on herbivorous or pollinating insects. Non-herbivores represent a significant proportion of beetle diversity yet potential factors that influence their diversification have been largely unexamined. In the present study, we examine the factors driving diversification within the Scarabaeidae, a speciose beetle family with a range of both herbivorous and non-herbivorous ecologies. In particular, it has been long debated whether the key event in the evolution of dung beetles (Scarabaeidae: Scarabaeinae) was an adaptation to feeding on dinosaur or mammalian dung. Here we present molecular evidence to show that the origin of dung beetles occurred in the middle of the Cretaceous, likely in association with dinosaur dung, but more surprisingly the timing is consistent with the rise of the angiosperms. We hypothesize that the switch in dinosaur diet to incorporate more nutritious and less fibrous angiosperm foliage provided a palatable dung source that ultimately created a new niche for diversification. Given the well-accepted mass extinction of non-avian dinosaurs at the Cretaceous-Paleogene boundary, we examine a potential co-extinction of dung beetles due to the loss of an important evolutionary resource, i.e., dinosaur dung. The biogeography of dung beetles is also examined to explore the previously proposed "out of Africa" hypothesis. Given the inferred age of Scarabaeinae as originating in the Lower Cretaceous, the major radiation of dung feeders prior to the Cenomanian, and the early divergence of both African and Gondwanan lineages, we hypothesise that that faunal exchange between Africa and Gondwanaland occurred during the earliest evolution of the Scarabaeinae. Therefore we propose that both Gondwanan vicariance and dispersal of African lineages is responsible for present day distribution of scarabaeine dung beetles and provide examples.

If Dung Beetles (Scarabaeidae: Scarabaeinae) Arose in Association with Dinosaurs, Did They Also Suffer a Mass Co-Extinction at the K-Pg Boundary?

PubMed Central

Gunter, Nicole L.; Weir, Tom A.; Cameron, Stephen L.

2016-01-01

The evolutionary success of beetles and numerous other terrestrial insects is generally attributed to co-radiation with flowering plants but most studies have focused on herbivorous or pollinating insects. Non-herbivores represent a significant proportion of beetle diversity yet potential factors that influence their diversification have been largely unexamined. In the present study, we examine the factors driving diversification within the Scarabaeidae, a speciose beetle family with a range of both herbivorous and non-herbivorous ecologies. In particular, it has been long debated whether the key event in the evolution of dung beetles (Scarabaeidae: Scarabaeinae) was an adaptation to feeding on dinosaur or mammalian dung. Here we present molecular evidence to show that the origin of dung beetles occurred in the middle of the Cretaceous, likely in association with dinosaur dung, but more surprisingly the timing is consistent with the rise of the angiosperms. We hypothesize that the switch in dinosaur diet to incorporate more nutritious and less fibrous angiosperm foliage provided a palatable dung source that ultimately created a new niche for diversification. Given the well-accepted mass extinction of non-avian dinosaurs at the Cretaceous-Paleogene boundary, we examine a potential co-extinction of dung beetles due to the loss of an important evolutionary resource, i.e., dinosaur dung. The biogeography of dung beetles is also examined to explore the previously proposed “out of Africa” hypothesis. Given the inferred age of Scarabaeinae as originating in the Lower Cretaceous, the major radiation of dung feeders prior to the Cenomanian, and the early divergence of both African and Gondwanan lineages, we hypothesise that that faunal exchange between Africa and Gondwanaland occurred during the earliest evolution of the Scarabaeinae. Therefore we propose that both Gondwanan vicariance and dispersal of African lineages is responsible for present day distribution of scarabaeine dung beetles and provide examples. PMID:27145126

A Combination of Histological, Physiological, and Proteomic Approaches Shed Light on Seed Desiccation Tolerance of the Basal Angiosperm Amborella trichopoda.

PubMed

Villegente, Matthieu; Marmey, Philippe; Job, Claudette; Galland, Marc; Cueff, Gwendal; Godin, Béatrice; Rajjou, Loïc; Balliau, Thierry; Zivy, Michel; Fogliani, Bruno; Sarramegna-Burtet, Valérie; Job, Dominique

2017-07-28

Desiccation tolerance allows plant seeds to remain viable in a dry state for years and even centuries. To reveal potential evolutionary processes of this trait, we have conducted a shotgun proteomic analysis of isolated embryo and endosperm from mature seeds of Amborella trichopoda , an understory shrub endemic to New Caledonia that is considered to be the basal extant angiosperm. The present analysis led to the characterization of 415 and 69 proteins from the isolated embryo and endosperm tissues, respectively. The role of these proteins is discussed in terms of protein evolution and physiological properties of the rudimentary, underdeveloped, Amborella embryos, notably considering that the acquisition of desiccation tolerance corresponds to the final developmental stage of mature seeds possessing large embryos.

A Combination of Histological, Physiological, and Proteomic Approaches Shed Light on Seed Desiccation Tolerance of the Basal Angiosperm Amborella trichopoda

PubMed Central

Villegente, Matthieu; Marmey, Philippe; Job, Claudette; Galland, Marc; Cueff, Gwendal; Godin, Béatrice; Rajjou, Loïc; Balliau, Thierry; Zivy, Michel; Sarramegna-Burtet, Valérie; Job, Dominique

2017-01-01

Desiccation tolerance allows plant seeds to remain viable in a dry state for years and even centuries. To reveal potential evolutionary processes of this trait, we have conducted a shotgun proteomic analysis of isolated embryo and endosperm from mature seeds of Amborella trichopoda, an understory shrub endemic to New Caledonia that is considered to be the basal extant angiosperm. The present analysis led to the characterization of 415 and 69 proteins from the isolated embryo and endosperm tissues, respectively. The role of these proteins is discussed in terms of protein evolution and physiological properties of the rudimentary, underdeveloped, Amborella embryos, notably considering that the acquisition of desiccation tolerance corresponds to the final developmental stage of mature seeds possessing large embryos. PMID:28788068

Phosphorylation of GENOMES UNCOUPLED 4 Alters Stimulation of Mg Chelatase Activity in Angiosperms1[OPEN

PubMed Central

Hochheuser, Caroline; Fufezan, Christian; Heinze, Laura

2016-01-01

GENOMES UNCOUPLED 4 (GUN4) is a positive regulator of light-dependent chlorophyll biosynthesis. GUN4 activates Mg chelatase (MgCh) that catalyzes the insertion of an Mg2+ ion into protoporphyrin IX. We show that Arabidopsis (Arabidopsis thaliana) GUN4 is phosphorylated at Ser 264 (S264), the penultimate amino acid residue at the C terminus. While GUN4 is preferentially phosphorylated in darkness, phosphorylation is reduced upon accumulation of Mg porphyrins. Expression of a phosphomimicking GUN4(S264D) results in an incomplete complementation of the white gun4-2 null mutant and a chlorotic phenotype comparable to gun4 knockdown mutants. Phosphorylated GUN4 has a reduced stimulatory effect on MgCh in vitro and in vivo but retains its protein stability and tetrapyrrole binding capacity. Analysis of GUN4 found in oxygenic photosynthetic organisms reveals the evolution of a C-terminal extension, which harbors the phosphorylation site of GUN4 expressed in angiosperms. Homologs of GUN4 from Synechocystis and Chlamydomonas lack the conserved phosphorylation site found in a C-terminal extension of angiosperm GUN4. Biochemical studies proved the importance of the C-terminal extension for MgCh stimulation and inactivation of GUN4 by phosphorylation in angiosperms. An additional mechanism regulating MgCh activity is proposed. In conjunction with the dark repression of 5-aminolevulinic acid synthesis, GUN4 phosphorylation minimizes the flow of intermediates into the Mg branch of the tetrapyrrole metabolic pathway for chlorophyll biosynthesis. PMID:27688621

The Past Sure is Tense: On Interpreting Phylogenetic Divergence Time Estimates.

PubMed

Brown, Joseph W; Smith, Stephen A

2018-03-01

Divergence time estimation-the calibration of a phylogeny to geological time-is an integral first step in modeling the tempo of biological evolution (traits and lineages). However, despite increasingly sophisticated methods to infer divergence times from molecular genetic sequences, the estimated age of many nodes across the tree of life contrast significantly and consistently with timeframes conveyed by the fossil record. This is perhaps best exemplified by crown angiosperms, where molecular clock (Triassic) estimates predate the oldest (Early Cretaceous) undisputed angiosperm fossils by tens of millions of years or more. While the incompleteness of the fossil record is a common concern, issues of data limitation and model inadequacy are viable (if underexplored) alternative explanations. In this vein, Beaulieu et al. (2015) convincingly demonstrated how methods of divergence time inference can be misled by both (i) extreme state-dependent molecular substitution rate heterogeneity and (ii) biased sampling of representative major lineages. These results demonstrate the impact of (potentially common) model violations. Here, we suggest another potential challenge: that the configuration of the statistical inference problem (i.e., the parameters, their relationships, and associated priors) alone may preclude the reconstruction of the paleontological timeframe for the crown age of angiosperms. We demonstrate, through sampling from the joint prior (formed by combining the tree (diversification) prior with the calibration densities specified for fossil-calibrated nodes) that with no data present at all, that an Early Cretaceous crown angiosperms is rejected (i.e., has essentially zero probability). More worrisome, however, is that for the 24 nodes calibrated by fossils, almost all have indistinguishable marginal prior and posterior age distributions when employing routine lognormal fossil calibration priors. These results indicate that there is inadequate information in the data to over-rule the joint prior. Given that these calibrated nodes are strategically placed in disparate regions of the tree, they act to anchor the tree scaffold, and so the posterior inference for the tree as a whole is largely determined by the pseudodata present in the (often arbitrary) calibration densities. We recommend, as for any Bayesian analysis, that marginal prior and posterior distributions be carefully compared to determine whether signal is coming from the data or prior belief, especially for parameters of direct interest. This recommendation is not novel. However, given how rarely such checks are carried out in evolutionary biology, it bears repeating. Our results demonstrate the fundamental importance of prior/posterior comparisons in any Bayesian analysis, and we hope that they further encourage both researchers and journals to consistently adopt this crucial step as standard practice. Finally, we note that the results presented here do not refute the biological modeling concerns identified by Beaulieu et al. (2015). Both sets of issues remain apposite to the goals of accurate divergence time estimation, and only by considering them in tandem can we move forward more confidently.

Independent and combined analyses of sequences from all three genomic compartments converge on the root of flowering plant phylogeny

PubMed Central

Barkman, Todd J.; Chenery, Gordon; McNeal, Joel R.; Lyons-Weiler, James; Ellisens, Wayne J.; Moore, Gerry; Wolfe, Andrea D.; dePamphilis, Claude W.

2000-01-01

Plant phylogenetic estimates are most likely to be reliable when congruent evidence is obtained independently from the mitochondrial, plastid, and nuclear genomes with all methods of analysis. Here, results are presented from separate and combined genomic analyses of new and previously published data, including six and nine genes (8,911 bp and 12,010 bp, respectively) for different subsets of taxa that suggest Amborella + Nymphaeales (water lilies) are the first-branching angiosperm lineage. Before and after tree-independent noise reduction, most individual genomic compartments and methods of analysis estimated the Amborella + Nymphaeales basal topology with high support. Previous phylogenetic estimates placing Amborella alone as the first extant angiosperm branch may have been misled because of a series of specific problems with paralogy, suboptimal outgroups, long-branch taxa, and method dependence. Ancestral character state reconstructions differ between the two topologies and affect inferences about the features of early angiosperms. PMID:11069280

Floral adaptation and diversification under pollen limitation

PubMed Central

Harder, Lawrence D.; Aizen, Marcelo A.

2010-01-01

Pollen limitation (PL) of seed production creates unique conditions for reproductive adaptation by angiosperms, in part because, unlike under ovule or resource limitation, floral interactions with pollen vectors can contribute to variation in female success. Although the ecological and conservation consequences of PL have received considerable attention in recent times, its evolutionary implications are poorly appreciated. To identify general influences of PL on reproductive adaptation compared with those under other seed-production limits and their implications for evolution in altered environments, we derive a model that incorporates pollination and post-pollination aspects of PL. Because PL always favours increased ovule fertilization, even when population dynamics are not seed limited, it should pervasively influence selection on reproductive traits. Significantly, under PL the intensity of inbreeding does not determine whether outcrossing or autonomous selfing can evolve, although it can affect which response is most likely. Because the causes of PL are multifaceted in both natural and anthropogenically altered environments, the possible outcrossing solutions are diverse and context dependent, which may contribute to the extensive variety of angiosperm reproductive characteristics. Finally, the increased adaptive options available under PL may be responsible for positive global associations between it and angiosperm diversity. PMID:20047878

Studies of angiospermous woods in Australian brown coal by nuclear magnetic resonance and analytical pyrolysis: new insight into early coalification

USGS Publications Warehouse

Hatcher, P.G.; Wilson, M.A.; Vassalo, M.; Lerch, H. E.

1990-01-01

Many Tertiary coals contain abundant fossilized remains of angiosperms that often dominated some ancient peat-swamp environments; modern analogs of which can be found in tropical and subtropical regions of the world. Comparisons of angiospermous woods from Australian brown coal with similar woods buried in modern peat swamps of Indonesia have provided some new insights into coalification reactions. These comparisons were made by using solid-state 13C nuclear magnetic resonance (NMR) techniques and pyrolysis-gas chromatography-mass spectrometry (py-gc-ms), two modern techniques especially suited for detailed structural evaluation of the complex macromolecules in coal. From these studies, we conclude that the earliest transformation (peatification) of organic matter in angiospermous wood is the degradation of cellulosic components. The efficiency of removal of cellulosic components in the wood varies considerably in peat, which results in variable levels of cellulose in peatified wood. However, the net trend is towards eventual removal of the cellulose. The angiospermous lignin that becomes enriched in wood as a result of cellulose degradation also is modified by coalifications reactions; this modification, however, does not involve degradation and removal. Rather, the early coalification process transforms the lignin phenols (guaiacyl and syringyl) to eventually yield the aromatic structures typically found in brown coal. One such transformation, which is determined from the NMR data, involves the cleavage of aryl ether bonds that link guaiacyl and syringyl units in lignin and leads to the formation of free lignin phenols. Another transformation, which is also determined from the NMR data, involves the loss of methoxyl groups, probably via demethylation, to produce catechol-like structures. Coincident with ether-cleavage and demethylation, the aromatic rings derived from lignin phenols become more carbon-substituted and cross-linked, as determined by dipolar-dephasing NMR studies. This cross-linking is probably responsible for preventing the lignin phenols, which are freed from the lignin macromolecule by ether cleavage and from being removed from the coal by dissolution. Pyrolysis data suggest that the syringyl units are altered more readily than are guaiacyl units, which leads to an enrichment of the guaiacyl units in fossil angiospermous woods. Although many of the coalification reactions noted above occur to some degree in all angiospermous fossil woods examined, some significant differences are observed in the degree of coalification of the fossil woods from the same burial depth in the brown coal. This indicates that the depth and the duration of burial are probably not entirely responsible for the variations in degree of coalification. It is likely that different rates of degradation in peat may have contributed to the variations in the apparent degree of coalification, considering the fact that some woods may have been altered more rapidly at the peat stage than others. Although preliminary, it is clear that a systematic study of botanically related woods in peat and coal leads to a more detailed differentiation of coalification reactions than have previous investigations. The combined use of solid-state 13C NMR and py-gc-ms has facilitated this detailed new insight into coalification of angiospermous wood. ?? 1990.

Complete chloroplast genome sequences of Drimys, Liriodendron, andPiper: Implications for the phylogeny of magnoliids and the evolution ofGC content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhengqiu, C.; Penaflor, C.; Kuehl, J.V.

2006-06-01

The magnoliids represent the largest basal angiosperm clade with four orders, 19 families and 8,500 species. Although several recent angiosperm molecular phylogenies have supported the monophyly of magnoliids and suggested relationships among the orders, the limited number of genes examined resulted in only weak support, and these issues remain controversial. Furthermore, considerable incongruence has resulted in phylogenies supporting three different sets of relationships among magnoliids and the two large angiosperm clades, monocots and eudicots. This is one of the most important remaining issues concerning relationships among basal angiosperms. We sequenced the chloroplast genomes of three magnoliids, Drimys (Canellales), Liriodendron (Magnoliales),more » and Piper (Piperales), and used these data in combination with 32 other completed angiosperm chloroplast genomes to assess phylogenetic relationships among magnoliids. The Drimys and Piper chloroplast genomes are nearly identical in size at 160,606 and 160,624 bp, respectively. The genomes include a pair of inverted repeats of 26,649 bp (Drimys) and 27,039 (Piper), separated by a small single copy region of 18,621 (Drimys) and 18,878 (Piper) and a large single copy region of 88,685 bp (Drimys) and 87,666 bp (Piper). The gene order of both taxa is nearly identical to many other unrearranged angiosperm chloroplast genomes, including Calycanthus, the other published magnoliid genome. Comparisons of angiosperm chloroplast genomes indicate that GC content is not uniformly distributed across the genome. Overall GC content ranges from 34-39%, and coding regions have a substantially higher GC content than non-coding regions (both intergenic spacers and introns). Among protein-coding genes, GC content varies by codon position with 1st codon > 2nd codon > 3rd codon, and it varies by functional group with photosynthetic genes having the highest percentage and NADH genes the lowest. Across the genome, GC content is highest in the inverted repeat due to the presence of rRNA genes and lowest in the small single copy region where most NADH genes are located. Phylogenetic analyses using maximum parsimony and maximum likelihood methods were performed on DNA sequences of 61 protein-coding genes. Trees from both analyses provided strong support for the monophyly of magnoliids and two strongly supported groups were identified, the Canellales/Piperales and the Laurales/Magnoliales. The phylogenies also provided moderate to strong support for the basal position of Amborella, and a sister relationship of magnoliids to a clade that includes monocots and eudicots. The complete sequences of three magnoliid chloroplast genomes provide new data from the largest basal angiosperm clade. Evolutionary comparisons of these new genome sequences, combined with other published angiosperm genome, confirm that GC content is unevenly distributed across the genome by location, codon position, and functional group. Furthermore, phylogenetic analyses provide the strongest support so far for the hypothesis that the magnoliids are sister to a large clade that includes both monocots and eudicots.« less

The evolution of floral sonication, a pollen foraging behavior used by bees (Anthophila).

PubMed

Cardinal, Sophie; Buchmann, Stephen L; Russell, Avery L

2018-03-01

Over 22,000 species of biotically pollinated flowering plants, including some major agricultural crops, depend primarily on bees capable of floral sonication for pollination services. The ability to sonicate ("buzz") flowers is widespread in bees but not ubiquitous. Despite the prevalence of this pollinator behavior and its importance to natural and agricultural systems, the evolutionary history of floral sonication in bees has not been previously studied. Here, we reconstruct the evolutionary history of floral sonication in bees by generating a time-calibrated phylogeny and reconstructing ancestral states for this pollen extraction behavior. We also test the hypothesis that the ability to sonicate flowers and thereby efficiently access pollen from a diverse assemblage of plant species, led to increased diversification among sonicating bee taxa. We find that floral sonication evolved on average 45 times within bees, possibly first during the Early Cretaceous (100-145 million years ago) in the common ancestor of bees. We find that sonicating lineages are significantly more species rich than nonsonicating sister lineages when comparing sister clades, but a probabilistic structured rate permutation on phylogenies approach failed to support the hypothesis that floral sonication is a key driver of bee diversification. This study provides the evolutionary framework needed to further study how floral sonication by bees may have facilitated the spread and common evolution of angiosperm species with poricidal floral morphology. © 2018 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Two-Step Functional Innovation of the Stem-Cell Factors WUS/WOX5 during Plant Evolution

PubMed Central

Zhang, Yuzhou; Jiao, Yue; Jiao, Hengwu

2017-01-01

WUS and WOX5, which are expressed, respectively, in the organizing center (OC) and the quiescent center (QC), are essential for shoot/root apical stem-cell maintenance in flowering plants. However, little is known about how these stem-cell factors evolved their functions in flowering plants. Here, we show that the WUS/WOX5 proteins acquired two distinct capabilities by a two-step functional innovation process in the course of plant evolution. The first-step is the apical stem-cell maintenance activity of WUS/WOX5, which originated in the common ancestor of ferns and seed plants, as evidenced by the interspecies complementation experiments, showing that ectopic expression of fern Ceratopteris richardii WUS-like (CrWUL) surrounding OC/QC, or exclusive OC-/QC-expressed gymnosperms/angiosperms WUS/WOX5 in Arabidopsis wus-1 and wox5-1 mutants, could rescue their phenotypes. The second-step is the intercellular mobility that emerged in the common ancestor of seed plants after divergence from the ferns. Evidence for this includes confocal imaging of GFP fusion proteins, showing that WUS/WOX5 from seed plants, rather than from the fern CrWUL, can migrate into cells adjacent to the OC/QC. Evolutionary analysis showed that the WUS-like gene was duplicated into two copies prior to the divergence of gymnosperms/angiosperms. Then the two gene copies (WUS and WOX5) have undergone similar levels of purifying selection, which is consistent with their conserved functions in angiosperm shoot/root stem-cell maintenance and floral organ formation. Our results highlight the critical roles and the essential prerequisites that the two-step functional innovation of these genes performs and represents in the origin of flowering plants. PMID:28053005

Adaptive evolution of seed oil content in angiosperms: accounting for the global patterns of seed oils.

PubMed

Sanyal, Anushree; Decocq, Guillaume

2016-09-09

Studies of the biogeographic distribution of seed oil content in plants are fundamental to understanding the mechanisms of adaptive evolution in plants as seed oil is the primary energy source needed for germination and establishment of plants. However, seed oil content as an adaptive trait in plants is poorly understood. Here, we examine the adaptive nature of seed oil content in 168 angiosperm families occurring in different biomes across the world. We also explore the role of multiple seed traits like seed oil content and composition in plant adaptation in a phylogenetic and nonphylogenetic context. It was observed that the seed oil content in tropical plants (28.4 %) was significantly higher than the temperate plants (24.6 %). A significant relationship between oil content and latitude was observed in three families Papaveraceae, Sapindaceae and Sapotaceae indicating that selective forces correlated with latitude influence seed oil content. Evaluation of the response of seed oil content and composition to latitude and the correlation between seed oil content and composition showed that multiple seed traits, seed oil content and composition contribute towards plant adaptation. Investigation of the presence or absence of phylogenetic signals across 168 angiosperm families in 62 clades revealed that members of seven clades evolved to have high or low seed oil content independently as they did not share a common evolutionary path. The study provides us an insight into the biogeographical distribution and the adaptive role of seed oil content in plants. The study indicates that multiple seed traits like seed oil content and the fatty acid composition of the seed oils determine the fitness of the plants and validate the adaptive hypothesis that seed oil quantity and quality are crucial to plant adaptation.

Contrasting Patterns of Nucleotide Substitution Rates Provide Insight into Dynamic Evolution of Plastid and Mitochondrial Genomes of Geranium

PubMed Central

Park, Seongjun; Ruhlman, Tracey A.; Weng, Mao-Lun; Hajrah, Nahid H.; Sabir, Jamal S.M.

2017-01-01

Abstract Geraniaceae have emerged as a model system for investigating the causes and consequences of variation in plastid and mitochondrial genomes. Incredible structural variation in plastid genomes (plastomes) and highly accelerated evolutionary rates have been reported in selected lineages and functional groups of genes in both plastomes and mitochondrial genomes (mitogenomes), and these phenomena have been implicated in cytonuclear incompatibility. Previous organelle genome studies have included limited sampling of Geranium, the largest genus in the family with over 400 species. This study reports on rates and patterns of nucleotide substitutions in plastomes and mitogenomes of 17 species of Geranium and representatives of other Geraniaceae. As detected across other angiosperms, substitution rates in the plastome are 3.5 times higher than the mitogenome in most Geranium. However, in the branch leading to Geranium brycei/Geranium incanum mitochondrial genes experienced significantly higher dN and dS than plastid genes, a pattern that has only been detected in one other angiosperm. Furthermore, rate accelerations differ in the two organelle genomes with plastomes having increased dN and mitogenomes with increased dS. In the Geranium phaeum/Geranium reflexum clade, duplicate copies of clpP and rpoA genes that experienced asymmetric rate divergence were detected in the single copy region of the plastome. In the case of rpoA, the branch leading to G. phaeum/G. reflexum experienced positive selection or relaxation of purifying selection. Finally, the evolution of acetyl-CoA carboxylase is unusual in Geraniaceae because it is only the second angiosperm family where both prokaryotic and eukaryotic ACCases functionally coexist in the plastid. PMID:28854633

Gymnosperm B-sister genes may be involved in ovule/seed development and, in some species, in the growth of fleshy fruit-like structures.

PubMed

Lovisetto, Alessandro; Guzzo, Flavia; Busatto, Nicola; Casadoro, Giorgio

2013-08-01

The evolution of seeds together with the mechanisms related to their dispersal into the environment represented a turning point in the evolution of plants. Seeds are produced by gymnosperms and angiosperms but only the latter have an ovary to be transformed into a fruit. Yet some gymnosperms produce fleshy structures attractive to animals, thus behaving like fruits from a functional point of view. The aim of this work is to increase our knowledge of possible mechanisms common to the development of both gymnosperm and angiosperm fruits. B-sister genes from two gymnosperms (Ginkgo biloba and Taxus baccata) were isolated and studied. The Ginkgo gene was also functionally characterized by ectopically expressing it in tobacco. In Ginkgo the fleshy structure derives from the outer seed integument and the B-sister gene is involved in its growth. In Taxus the fleshy structure is formed de novo as an outgrowth of the ovule peduncle, and the B-sister gene is not involved in this growth. In transgenic tobacco the Ginkgo gene has a positive role in tissue growth and confirms its importance in ovule/seed development. This study suggests that B-sister genes have a main function in ovule/seed development and a subsidiary role in the formation of fleshy fruit-like structures when the latter have an ovular origin, as occurs in Ginkgo. Thus, the 'fruit function' of B-sister genes is quite old, already being present in Gymnosperms as ancient as Ginkgoales, and is also present in Angiosperms where a B-sister gene has been shown to be involved in the formation of the Arabidopsis fruit.

Trees and Weathering: Using Soil Petrographic and Chemical Analyses to Compare the Relative Weathering Effects of Gymnosperms and Angiosperms in the Cascade Mountains of Washington State, USA

NASA Astrophysics Data System (ADS)

Andrews, M. Y.; Ague, J. J.; Berner, R. A.

2006-12-01

Knowledge of the long-term carbon cycle and its control on atmospheric carbon dioxide levels over the Phanerozoic is crucial to understanding the impending dynamics of contemporary anthropogenic carbon contributions to the atmosphere. One aspect of the long-term carbon cycle that is poorly understood is the role of large vascular plants (trees) in contributing to the chemical weathering of silicate minerals. In particular, little is known about the differences in weathering rates between gymnosperms and angiosperms and how these dissimilarities may have impacted the carbon cycle subsequent to the evolution of angiosperm trees in the Mesozoic. One approach to evaluating these potential differences in weathering is to examine and quantitatively compare the chemistry and petrology of the soil mineral constituents from beneath modern groves of each broad tree type, where the groves have been subject to nearly identical environmental and geological conditions. This particular study focuses on field samples collected along transects through adjacent groves of angiosperms and gymnosperms in the Cascade Mountains of Washington State. Preliminary data demonstrate a significant difference in the soil texture and composition beneath the two types of trees. While soil at each field site has been generated from a homogeneous parent material, and subjected to similar inorganic environmental phenomena, soil density, particle size, and organic content vary across the transects. Soils beneath the angiosperms are denser and have a more clay-like texture, while soils beneath the gymnosperms are more organic-rich and have a sandy texture. Additional macroscopic and microscopic differences in the chemistry and petrology of these soils will illuminate the varied impacts these trees have on the silicate minerals in their immediate environment, and therefore lend insight into the potential impact these groups of organisms have had on the long-term carbon cycle over the past five hundred million years.

Parallel evolution of angiosperm colour signals: common evolutionary pressures linked to hymenopteran vision

PubMed Central

Dyer, Adrian G.; Boyd-Gerny, Skye; McLoughlin, Stephen; Rosa, Marcello G. P.; Simonov, Vera; Wong, Bob B. M.

2012-01-01

Flowering plants in Australia have been geographically isolated for more than 34 million years. In the Northern Hemisphere, previous work has revealed a close fit between the optimal discrimination capabilities of hymenopteran pollinators and the flower colours that have most frequently evolved. We collected spectral data from 111 Australian native flowers and tested signal appearance considering the colour discrimination capabilities of potentially important pollinators. The highest frequency of flower reflectance curves is consistent with data reported for the Northern Hemisphere. The subsequent mapping of Australian flower reflectances into a bee colour space reveals a very similar distribution of flower colour evolution to the Northern Hemisphere. Thus, flowering plants in Australia are likely to have independently evolved spectral signals that maximize colour discrimination by hymenoptera. Moreover, we found that the degree of variability in flower coloration for particular angiosperm species matched the range of reflectance colours that can only be discriminated by bees that have experienced differential conditioning. This observation suggests a requirement for plasticity in the nervous systems of pollinators to allow generalization of flowers of the same species while overcoming the possible presence of non-rewarding flower mimics. PMID:22673351

The evolutionary diversification of seed size: using the past to understand the present.

PubMed

Sims, Hallie J

2012-05-01

The Devonian origin of seed plants and subsequent morphological diversification of seeds during the late Paleozoic represents an adaptive radiation into unoccupied ecological niche space. A plant's seed size is correlated with its life-history strategy, growth form, and seed dispersal syndrome. The fossil record indicates that the oldest seed plants had relatively small seeds, but the Mississippian seed size envelope increased significantly with the diversification of larger seeded lineages. Fossil seeds equivalent to the largest extant gymnosperm seeds appeared by the Pennsylvanian, concurrent with morphological diversification of growth forms and dispersal syndromes as well as the clade's radiation into new environments. Wang's Analysis of Skewness indicates that the evolutionary trend of increasing seed size resulted from primarily passive processes in Pennsylvanian seed plants. The distributions of modern angiosperms indicate a more diverse system of active and some passive processes, unbounded by Paleozoic limits; multiple angiosperm lineages independently evolved though the upper and lower bounds. Quantitative measures of preservation suggest that, although our knowledge of Paleozoic seeds is far from complete, the evolutionary trend in seed size is unlikely to be an artifact of taphonomy. © 2012 The Author. Evolution© 2012 The Society for the Study of Evolution.

Early Cretaceous Umkomasia from Mongolia: implications for homology of corystosperm cupules.

PubMed

Shi, Gongle; Leslie, Andrew B; Herendeen, Patrick S; Herrera, Fabiany; Ichinnorov, Niiden; Takahashi, Masamichi; Knopf, Patrick; Crane, Peter R

2016-06-01

Corystosperms, a key extinct group of Late Permian to Early Cretaceous plants, are important for understanding seed plant phylogeny, including the evolution of the angiosperm carpel and anatropous bitegmic ovule. Here, we describe a new species of corystosperm seed-bearing organ, Umkomasia mongolica sp. nov., based on hundreds of three-dimensionally preserved mesofossils from the Early Cretaceous of Mongolia. Individual seed-bearing units of U. mongolica consist of a bract subtending an axis that bifurcates, with each fork (cupule stalk) bearing a cupule near the tip. Each cupule is formed by the strongly reflexed cupule stalk and two lateral flaps that partially enclose an erect seed. The seed is borne at, or close to, the tip of the reflexed cupule stalk, with the micropyle oriented towards the stalk base. The corystosperm cupule is generally interpreted as a modified leaf that bears a seed on its abaxial surface. However, U. mongolica suggests that an earlier interpretation, in which the seed is borne directly on an axis (shoot), is equally likely. The 'axial' interpretation suggests a possible relationship of corystosperms to Ginkgo. It also suggests that the cupules of corystosperms may be less distinct from those of Caytonia than has previously been supposed. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Pulses of middle Eocene to earliest Oligocene climatic deterioration in southern California and the Gulf Coast

USGS Publications Warehouse

Frederiksen, N.O.

1991-01-01

A general deterioration of terrestrial climate took place during middle Eocene to earliest Oligocene time in southern California and in the Gulf Coast. Pollen data, calibrated by calcareous nannofossil ages, indicate four events of rapid floral and/or vegetational change among angiosperms during this time interval. The events can be correlated between the two regions even though these regions lay within different floristic provinces, and each event of angiosperm change is interpreted to indicate a pulse of rapid climatic shift. The most distinct of these events is the Middle Eocene Diversity Decline, which resulted from a peak in last appearances (extinctions, emigrations) centered in the early Bartonian. -from Author

Molecular interactions of orthologues of floral homeotic proteins from the gymnosperm Gnetum gnemon provide a clue to the evolutionary origin of 'floral quartets'.

PubMed

Wang, Yong-Qiang; Melzer, Rainer; Theissen, Günter

2010-10-01

Several lines of evidence suggest that the identity of floral organs in angiosperms is specified by multimeric transcription factor complexes composed of MADS-domain proteins. These bind to specific cis-regulatory elements ('CArG-boxes') of their target genes involving DNA-loop formation, thus constituting 'floral quartets'. Gymnosperms, angiosperms' closest relatives, contain orthologues of floral homeotic genes, but when and how the interactions constituting floral quartets were established during evolution has remained unknown. We have comprehensively studied the dimerization and DNA-binding of several classes of MADS-domain proteins from the gymnosperm Gnetum gnemon. Determination of protein-protein and protein-DNA interactions by yeast two-hybrid, in vitro pull-down and electrophoretic mobility shift assays revealed complex patterns of homo- and heterodimerization among orthologues of floral homeotic class B, class C and class E proteins and B(sister) proteins. Using DNase I footprint assays we demonstrate that both orthologues of class B with C proteins, and orthologues of class C proteins alone, but not orthologues of class B proteins alone can loop DNA in floral quartet-like complexes. This is in contrast to class B and class C proteins from angiosperms, which require other factors such as class E floral homeotic proteins to 'glue' them together in multimeric complexes. Our findings suggest that the evolutionary origin of floral quartet formation is based on the interaction of different DNA-bound homodimers, does not depend on class E proteins, and predates the origin of angiosperms. © 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd.

Early to mid Cretaceous vegetation of northern Gondwana - the onset of angiosperm radiation and climatic implications

NASA Astrophysics Data System (ADS)

Coiffard, Clément; Mohr, Barbara

2014-05-01

Early Cretaceous Northern Gondwana seems to be the cradle of many early flowering plants, especially mesangiosperms that include magnoliids and monocots and basal eudicots. So far our knowledge was based mostly on dispersed pollen and small flowering structures. New fossil finds from Brazil include more complete plants with attached roots, leaves and flowers. Taxonomic studies show that these fossils belonged to clades which are, based on macroscopic characters and molecular data, also considered to be rather basal, such as several members of Nymphaeales, Piperales, Laurales, Magnoliales, monocots (Araliaceae) and Ranunculales. Various parameters can be used in order to understand the physiology and habitat of these plants. Adaptations to climate and habitat are partly mirrored in their root anatomy (evidence of tap roots), leaf size and shape, leaf anatomy including presence of glands, and distribution of stomata. An important ecophysiolocical parameter is vein density as an indicator for the plants' cabability to pump water, and the stomatal pore index, representing the proportion of stomatal pore area on the leaf surface, which is related to the water vapor resistance of the leaf epidermis. During the mid-Cretaceous leaf vein density started to surpass that of gymnosperms, one factor that made angiosperms very successful in conquering many kinds of new environments. Using data on these parameters we deduce that during the late Early to mid Cretaceous angiosperms were already diverse, being represented as both herbs, with aquatic members, such as Nymphaeles, helophytes (e.g. some monocots) and plants that may have grown in shady locations. Other life forms included shrubs and perhaps already small trees (e.g. Magnoliales). These flowering plants occupied various habitats, ranging from xeric (e.g. some Magnoliales) to mesic and shady (e.g. Piperales) or aquatic (e.g. Araceae, Nymphaeales). Overall, it seems that several of these plants clearly exhibited some mechanisms to withstand drought, which in turn let us assume that the climate was characterized by dry and wet seasons.

Transition from two to one integument in Prunus species: expression pattern of INNER NO OUTER (INO), ABERRANT TESTA SHAPE (ATS) and ETTIN (ETT).

PubMed

Lora, Jorge; Hormaza, José I; Herrero, Maria

2015-10-01

While gymnosperm ovules have one integument, in most angiosperms two integuments surround the ovules. Unitegmic ovules have arisen independently several times during the evolution of angiosperms, but the ultimate genetic cause of the presence of a single integument remains elusive. We compared species of the genus Prunus that have different numbers of integuments: bitegmic species, such as Prunus armeniaca (apricot) and Prunus persica (peach), and unitegmic species, such as Prunus incisa, analyzing the expression pattern of genes that are involved in integument development in Arabidopsis thaliana: INNER NO OUTER (INO), ABERRANT TESTA SHAPE (ATS) and ETTIN (ETT). Bitegmic and unitegmic species showed similar INO expression patterns, indicative of the conservation of an outer integument. However, expression of ETT, which occurs in the boundary of the outer and inner integuments, was altered in unitegmic ovules, which showed lack of ETT expression. These results strongly suggest that the presence of a single integument could be attributable to the amalgamation of two integuments and support the role of ETT in the fusion of the outer and inner integuments in unitegmic ovules, a situation that could be widespread in other unitegmic species of angiosperms. © 2015 Consejo Superior de Investigaciones Cientificas. New Phytologist © 2015 New Phytologist Trust.

Evolution of the Plant Reproduction Master Regulators LFY and the MADS Transcription Factors: The Role of Protein Structure in the Evolutionary Development of the Flower.

PubMed

Silva, Catarina S; Puranik, Sriharsha; Round, Adam; Brennich, Martha; Jourdain, Agnès; Parcy, François; Hugouvieux, Veronique; Zubieta, Chloe

2015-01-01

Understanding the evolutionary leap from non-flowering (gymnosperms) to flowering (angiosperms) plants and the origin and vast diversification of the floral form has been one of the focuses of plant evolutionary developmental biology. The evolving diversity and increasing complexity of organisms is often due to relatively small changes in genes that direct development. These "developmental control genes" and the transcription factors (TFs) they encode, are at the origin of most morphological changes. TFs such as LEAFY (LFY) and the MADS-domain TFs act as central regulators in key developmental processes of plant reproduction including the floral transition in angiosperms and the specification of the male and female organs in both gymnosperms and angiosperms. In addition to advances in genome wide profiling and forward and reverse genetic screening, structural techniques are becoming important tools in unraveling TF function by providing atomic and molecular level information that was lacking in purely genetic approaches. Here, we summarize previous structural work and present additional biophysical and biochemical studies of the key master regulators of plant reproduction - LEAFY and the MADS-domain TFs SEPALLATA3 and AGAMOUS. We discuss the impact of structural biology on our understanding of the complex evolutionary process leading to the development of the bisexual flower.

First steps in studying the origins of secondary woodiness in Begonia (Begoniaceae): combining anatomy, phylogenetics, and stem transcriptomics

Treesearch

Catherine Kidner; Andrew Groover; Daniel C. Thomas; Katie Emelianova; Claudia Soliz-Gamboa; Frederic Lens

2015-01-01

Since Darwin's observation that secondary woodiness is common on islands, the evolution of woody plants from herbaceous ancestors has been documented in numerous angiosperm groups. However, the evolutionary processes that give rise to this phenomenon are poorly understood. To begin addressing this we have used a range of approaches to study the anatomical and...

Multiple Geographical Origins of Environmental Sex Determination enhanced the diversification of Darwin's Favourite Orchids.

PubMed

Pérez-Escobar, Oscar Alejandro; Chomicki, Guillaume; Condamine, Fabien L; de Vos, Jurriaan M; Martins, Aline C; Smidt, Eric C; Klitgård, Bente; Gerlach, Günter; Heinrichs, Jochen

2017-10-10

Environmental sex determination (ESD) - a change in sexual function during an individual life span driven by environmental cues - is an exceedingly rare sexual system among angiosperms. Because ESD can directly affect reproduction success, it could influence diversification rate as compared with lineages that have alternative reproductive systems. Here we test this hypothesis using a solid phylogenetic framework of Neotropical Catasetinae, the angiosperm lineage richest in taxa with ESD. We assess whether gains of ESD are associated with higher diversification rates compared to lineages with alternative systems while considering additional traits known to positively affect diversification rates in orchids. We found that ESD has evolved asynchronously three times during the last ~5 Myr. Lineages with ESD have consistently higher diversification rates than related lineages with other sexual systems. Habitat fragmentation due to mega-wetlands extinction, and climate instability are suggested as the driving forces for ESD evolution.

Coevolution between Nuclear-Encoded DNA Replication, Recombination, and Repair Genes and Plastid Genome Complexity.

PubMed

Zhang, Jin; Ruhlman, Tracey A; Sabir, Jamal S M; Blazier, John Chris; Weng, Mao-Lun; Park, Seongjun; Jansen, Robert K

2016-02-17

Disruption of DNA replication, recombination, and repair (DNA-RRR) systems has been hypothesized to cause highly elevated nucleotide substitution rates and genome rearrangements in the plastids of angiosperms, but this theory remains untested. To investigate nuclear-plastid genome (plastome) coevolution in Geraniaceae, four different measures of plastome complexity (rearrangements, repeats, nucleotide insertions/deletions, and substitution rates) were evaluated along with substitution rates of 12 nuclear-encoded, plastid-targeted DNA-RRR genes from 27 Geraniales species. Significant correlations were detected for nonsynonymous (dN) but not synonymous (dS) substitution rates for three DNA-RRR genes (uvrB/C, why1, and gyrA) supporting a role for these genes in accelerated plastid genome evolution in Geraniaceae. Furthermore, correlation between dN of uvrB/C and plastome complexity suggests the presence of nucleotide excision repair system in plastids. Significant correlations were also detected between plastome complexity and 13 of the 90 nuclear-encoded organelle-targeted genes investigated. Comparisons revealed significant acceleration of dN in plastid-targeted genes of Geraniales relative to Brassicales suggesting this correlation may be an artifact of elevated rates in this gene set in Geraniaceae. Correlation between dN of plastid-targeted DNA-RRR genes and plastome complexity supports the hypothesis that the aberrant patterns in angiosperm plastome evolution could be caused by dysfunction in DNA-RRR systems. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Genomics of sex determination.

PubMed

Zhang, Jisen; Boualem, Adnane; Bendahmane, Abdelhafid; Ming, Ray

2014-04-01

Sex determination is a major switch in the evolutionary history of angiosperm, resulting 11% monoecious and dioecious species. The genomic sequences of papaya sex chromosomes unveiled the molecular basis of recombination suppression in the sex determination region, and candidate genes for sex determination. Identification and analyses of sex determination genes in cucurbits and maize demonstrated conservation of sex determination mechanism in one lineage and divergence between the two systems. Epigenetic control and hormonal influence of sex determination were elucidated in both plants and animals. Intensive investigation of potential sex determination genes in model species will improve our understanding of sex determination gene network. Such network will in turn accelerate the identification of sex determination genes in dioecious species with sex chromosomes, which are burdensome due to no recombination in sex determining regions. The sex determination genes in dioecious species are crucial for understanding the origin of dioecy and sex chromosomes, particularly in their early stage of evolution. Copyright © 2014 Elsevier Ltd. All rights reserved.

Parasitic plants have increased rates of molecular evolution across all three genomes

PubMed Central

2013-01-01

Background Theoretical models and experimental evidence suggest that rates of molecular evolution could be raised in parasitic organisms compared to non-parasitic taxa. Parasitic plants provide an ideal test for these predictions, as there are at least a dozen independent origins of the parasitic lifestyle in angiosperms. Studies of a number of parasitic plant lineages have suggested faster rates of molecular evolution, but the results of some studies have been mixed. Comparative analysis of all parasitic plant lineages, including sequences from all three genomes, is needed to examine the generality of the relationship between rates of molecular evolution and parasitism in plants. Results We analysed DNA sequence data from the mitochondrial, nuclear and chloroplast genomes for 12 independent evolutionary origins of parasitism in angiosperms. We demonstrated that parasitic lineages have a faster rate of molecular evolution than their non-parasitic relatives in sequences for all three genomes, for both synonymous and nonsynonymous substitutions. Conclusions Our results prove that raised rates of molecular evolution are a general feature of parasitic plants, not confined to a few taxa or specific genes. We discuss possible causes for this relationship, including increased positive selection associated with host-parasite arms races, relaxed selection, reduced population size or repeated bottlenecks, increased mutation rates, and indirect causal links with generation time and body size. We find no evidence that faster rates are due to smaller effective populations sizes or changes in selection pressure. Instead, our results suggest that parasitic plants have a higher mutation rate than their close non-parasitic relatives. This may be due to a direct connection, where some aspect of the parasitic lifestyle drives the evolution of raised mutation rates. Alternatively, this pattern may be driven by an indirect connection between rates and parasitism: for example, parasitic plants tend to be smaller than their non-parasitic relatives, which may result in more cell generations per year, thus a higher rate of mutations arising from DNA copy errors per unit time. Demonstration that adoption of a parasitic lifestyle influences the rate of genomic evolution is relevant to attempts to infer molecular phylogenies of parasitic plants and to estimate their evolutionary divergence times using sequence data. PMID:23782527

Parasitic plants have increased rates of molecular evolution across all three genomes.

PubMed

Bromham, Lindell; Cowman, Peter F; Lanfear, Robert

2013-06-19

Theoretical models and experimental evidence suggest that rates of molecular evolution could be raised in parasitic organisms compared to non-parasitic taxa. Parasitic plants provide an ideal test for these predictions, as there are at least a dozen independent origins of the parasitic lifestyle in angiosperms. Studies of a number of parasitic plant lineages have suggested faster rates of molecular evolution, but the results of some studies have been mixed. Comparative analysis of all parasitic plant lineages, including sequences from all three genomes, is needed to examine the generality of the relationship between rates of molecular evolution and parasitism in plants. We analysed DNA sequence data from the mitochondrial, nuclear and chloroplast genomes for 12 independent evolutionary origins of parasitism in angiosperms. We demonstrated that parasitic lineages have a faster rate of molecular evolution than their non-parasitic relatives in sequences for all three genomes, for both synonymous and nonsynonymous substitutions. Our results prove that raised rates of molecular evolution are a general feature of parasitic plants, not confined to a few taxa or specific genes. We discuss possible causes for this relationship, including increased positive selection associated with host-parasite arms races, relaxed selection, reduced population size or repeated bottlenecks, increased mutation rates, and indirect causal links with generation time and body size. We find no evidence that faster rates are due to smaller effective populations sizes or changes in selection pressure. Instead, our results suggest that parasitic plants have a higher mutation rate than their close non-parasitic relatives. This may be due to a direct connection, where some aspect of the parasitic lifestyle drives the evolution of raised mutation rates. Alternatively, this pattern may be driven by an indirect connection between rates and parasitism: for example, parasitic plants tend to be smaller than their non-parasitic relatives, which may result in more cell generations per year, thus a higher rate of mutations arising from DNA copy errors per unit time. Demonstration that adoption of a parasitic lifestyle influences the rate of genomic evolution is relevant to attempts to infer molecular phylogenies of parasitic plants and to estimate their evolutionary divergence times using sequence data.

The mitochondrial genome of the gymnosperm Cycas taitungensis contains a novel family of short interspersed elements, Bpu sequences, and abundant RNA editing sites.

PubMed

Chaw, Shu-Miaw; Shih, Arthur Chun-Chieh; Wang, Daryi; Wu, Yu-Wei; Liu, Shu-Mei; Chou, The-Yuan

2008-03-01

The mtDNA of Cycas taitungensis is a circular molecule of 414,903 bp, making it 2- to 6-fold larger than the known mtDNAs of charophytes and bryophytes, but similar to the average of 7 elucidated angiosperm mtDNAs. It is characterized by abundant RNA editing sites (1,084), more than twice the number found in the angiosperm mtDNAs. The A + T content of Cycas mtDNA is 53.1%, the lowest among known land plants. About 5% of the Cycas mtDNA is composed of a novel family of mobile elements, which we designated as "Bpu sequences." They share a consensus sequence of 36 bp with 2 terminal direct repeats (AAGG) and a recognition site for the Bpu 10I restriction endonuclease (CCTGAAGC). Comparison of the Cycas mtDNA with other plant mtDNAs revealed many new insights into the biology and evolution of land plant mtDNAs. For example, the noncoding sequences in mtDNAs have drastically expanded as land plants have evolved, with abrupt increases appearing in the bryophytes, and then in the seed plants. As a result, the genomic organizations of seed plant mtDNAs are much less compact than in other plants. Also, the Cycas mtDNA appears to have been exempted from the frequent gene loss observed in angiosperm mtDNAs. Similar to the angiosperms, the 3 Cycas genes nad1, nad2, and nad5 are disrupted by 5 group II intron squences, which have brought the genes into trans-splicing arrangements. The evolutionary origin and invasion/duplication mechanism of the Bpu sequences in Cycas mtDNA are hypothesized and discussed.

Regulation of stem cell maintenance by the Polycomb protein FIE has been conserved during land plant evolution.

PubMed

Mosquna, Assaf; Katz, Aviva; Decker, Eva L; Rensing, Stefan A; Reski, Ralf; Ohad, Nir

2009-07-01

The Polycomb group (PcG) complex is involved in the epigenetic control of gene expression profiles. In flowering plants, PcG proteins regulate vegetative and reproductive programs. Epigenetically inherited states established in the gametophyte generation are maintained after fertilization in the sporophyte generation, having a profound influence on seed development. The gametophyte size and phase dominance were dramatically reduced during angiosperm evolution, and have specialized in flowering plants to support the reproductive process. The moss Physcomitrella patens is an ideal organism in which to study epigenetic processes during the gametophyte stage, as it possesses a dominant photosynthetic gametophytic haploid phase and efficient homologous recombination, allowing targeted gene replacement. We show that P. patens PcG protein FIE (PpFIE) accumulates in haploid meristematic cells and in cells that undergo fate transition during dedifferentiation programs in the gametophyte. In the absence of PpFIE, meristems overproliferate and are unable to develop leafy gametophytes or reach the reproductive phase. This aberrant phenotype might result from failure of the PcG complex to repress proliferation and differentiation of three-faced apical stem cells, which are designated to become lateral shoots. The PpFIE phenotype can be partially rescued by FIE of Arabidopsis thaliana, a flowering plant that diverged >450 million years ago from bryophytes. PpFIE can partially complement the A. thaliana fie mutant, illustrating functional conservation of the protein during evolution in regulating the differentiation of meristematic cells in gametophyte development, both in bryophytes and angiosperms. This mechanism was harnessed at the onset of the evolution of alternating generations, facilitating the establishment of sporophytic developmental programs.

Mediterranean, invasive, woody species grow larger than their less-invasive counterparts under potential global environmental change.

PubMed

Erskine-Ogden, Jennifer; Grotkopp, Eva; Rejmánek, Marcel

2016-04-01

Revealing biological differences between invasive and noninvasive species is essential for predicting species' distribution changes with global environmental change. While most research has focused on differences between invasive and noninvasive species under favorable conditions using herbaceous species, invasive woody angiosperms are also of great ecological concern. Our study focused on how growth and allocation may change for invasive and noninvasive, mediterranean, woody angiosperms under future conditions caused by global change, specifically increased nitrogen deposition and drought. We tested how seedling functional traits differed between invasive and noninvasive woody angiosperms under different experimental conditions in a greenhouse setting. We compared growth rates and allocation patterns using two levels of soil nitrogen and three levels of watering. We also examined trait log response ratios to increases in nitrogen and increases in water. Our study sampled angiosperm trees and shrubs, incorporating congeneric/confamilial relationships through 13 phylogenetically controlled contrasts. Three functional traits were highly and positively associated with plant invasiveness for most conditions studied: seedling plant mass, leaf area, and height. Invasive species also had significantly higher root mass ratios at low water regardless of nitrogen input. Invasive and noninvasive species had similar log response ratios to increases in nitrogen and watering for studied traits. Mediterranean, woody, invasive species' larger mass, leaf area, and early height advantage under elevated nitrogen input and increased root production in drought conditions may lead to increased invasion of these species with expected global climate change. © 2016 Botanical Society of America.

Pollen development in Annona cherimola Mill. (Annonaceae). Implications for the evolution of aggregated pollen

PubMed Central

Lora, Jorge; Testillano, Pilar S; Risueño, Maria C; Hormaza, Jose I; Herrero, Maria

2009-01-01

Background In most flowering plants, pollen is dispersed as monads. However, aggregated pollen shedding in groups of four or more pollen grains has arisen independently several times during angiosperm evolution. The reasons behind this phenomenon are largely unknown. In this study, we followed pollen development in Annona cherimola, a basal angiosperm species that releases pollen in groups of four, to investigate how pollen ontogeny may explain the rise and establishment of this character. We followed pollen development using immunolocalization and cytochemical characterization of changes occurring from anther differentiation to pollen dehiscence. Results Our results show that, following tetrad formation, a delay in the dissolution of the pollen mother cell wall and tapetal chamber is a key event that holds the four microspores together in a confined tapetal chamber, allowing them to rotate and then bind through the aperture sites through small pectin bridges, followed by joint sporopollenin deposition. Conclusion Pollen grouping could be the result of relatively minor ontogenetic changes beneficial for pollen transfer or/and protection from desiccation. Comparison of these events with those recorded in the recent pollen developmental mutants in Arabidopsis indicates that several failures during tetrad dissolution may convert to a common recurring phenotype that has evolved independently several times, whenever this grouping conferred advantages for pollen transfer. PMID:19874617

How (much) do flowers vary? Unbalanced disparity among flower functional modules and a mosaic pattern of morphospace occupation in the order Ericales.

PubMed

Chartier, Marion; Löfstrand, Stefan; von Balthazar, Maria; Gerber, Sylvain; Jabbour, Florian; Sauquet, Hervé; Schönenberger, Jürg

2017-04-12

The staggering diversity of angiosperms and their flowers has fascinated scientists for centuries. However, the quantitative distribution of floral morphological diversity (disparity) among lineages and the relative contribution of functional modules (perianth, androecium and gynoecium) to total floral disparity have rarely been addressed. Focusing on a major angiosperm order (Ericales), we compiled a dataset of 37 floral traits scored for 381 extant species and nine fossils. We conducted morphospace analyses to explore phylogenetic, temporal and functional patterns of disparity. We found that the floral morphospace is organized as a continuous cloud in which most clades occupy distinct regions in a mosaic pattern, that disparity increases with clade size rather than age, and that fossils fall in a narrow portion of the space. Surprisingly, our study also revealed that among functional modules, it is the androecium that contributes most to total floral disparity in Ericales. We discuss our findings in the light of clade history, selective regimes as well as developmental and functional constraints acting on the evolution of the flower and thereby demonstrate that quantitative analyses such as the ones used here are a powerful tool to gain novel insights into the evolution and diversity of flowers. © 2017 The Authors.

The genetic basis of a plant–insect coevolutionary key innovation

PubMed Central

Wheat, Christopher W.; Vogel, Heiko; Wittstock, Ute; Braby, Michael F.; Underwood, Dessie; Mitchell-Olds, Thomas

2007-01-01

Ehrlich and Raven formally introduced the concept of stepwise coevolution using butterfly and angiosperm interactions in an attempt to account for the impressive biological diversity of these groups. However, many biologists currently envision butterflies evolving 50 to 30 million years (Myr) after the major angiosperm radiation and thus reject coevolutionary origins of butterfly biodiversity. The unresolved central tenet of Ehrlich and Raven's theory is that evolution of plant chemical defenses is followed closely by biochemical adaptation in insect herbivores, and that newly evolved detoxification mechanisms result in adaptive radiation of herbivore lineages. Using one of their original butterfly-host plant systems, the Pieridae, we identify a pierid glucosinolate detoxification mechanism, nitrile-specifier protein (NSP), as a key innovation. Larval NSP activity matches the distribution of glucosinolate in their host plants. Moreover, by using five different temporal estimates, NSP seems to have evolved shortly after the evolution of the host plant group (Brassicales) (≈10 Myr). An adaptive radiation of these glucosinolate-feeding Pierinae followed, resulting in significantly elevated species numbers compared with related clades. Mechanistic understanding in its proper historical context documents more ancient and dynamic plant–insect interactions than previously envisioned. Moreover, these mechanistic insights provide the tools for detailed molecular studies of coevolution from both the plant and insect perspectives. PMID:18077380

Pollen development in Annona cherimola Mill. (Annonaceae). Implications for the evolution of aggregated pollen.

PubMed

Lora, Jorge; Testillano, Pilar S; Risueño, Maria C; Hormaza, Jose I; Herrero, Maria

2009-10-29

In most flowering plants, pollen is dispersed as monads. However, aggregated pollen shedding in groups of four or more pollen grains has arisen independently several times during angiosperm evolution. The reasons behind this phenomenon are largely unknown. In this study, we followed pollen development in Annona cherimola, a basal angiosperm species that releases pollen in groups of four, to investigate how pollen ontogeny may explain the rise and establishment of this character. We followed pollen development using immunolocalization and cytochemical characterization of changes occurring from anther differentiation to pollen dehiscence. Our results show that, following tetrad formation, a delay in the dissolution of the pollen mother cell wall and tapetal chamber is a key event that holds the four microspores together in a confined tapetal chamber, allowing them to rotate and then bind through the aperture sites through small pectin bridges, followed by joint sporopollenin deposition. Pollen grouping could be the result of relatively minor ontogenetic changes beneficial for pollen transfer or/and protection from desiccation. Comparison of these events with those recorded in the recent pollen developmental mutants in Arabidopsis indicates that several failures during tetrad dissolution may convert to a common recurring phenotype that has evolved independently several times, whenever this grouping conferred advantages for pollen transfer.

Microspore development in Annona (Annonaceae): differences between monad and tetrad pollen.

PubMed

Lora, Jorge; Herrero, Maria; Hormaza, Jose I

2014-09-01

• Permanent tetrads are the most common form of pollen aggregation in flowering plants. The production of pollen in monads is plesiomorphic in angiosperms, but the aggregation into tetrads has arisen independently different times during the evolution of flowering plants. The causes behind the recurrent evolution of pollen aggregation from monads remain elusive. Permanent tetrad pollen is quite common in the Annonaceae, the largest family in the early-divergent order Magnoliales. In some genera, such as Annona, both tetrad- and monad-producing species can be found.• In this comparative study of pollen development, we use immunolocalization, cytological characterization, and enzymatic assays of four species in the genus Annona and one species in its closely related genus Asimina that release pollen in tetrads and two species in the genus Annona that release pollen in monads.• The main difference between species with tetrad and monad pollen is a delayed digestion of callose and cellulose at the pollen aperture sites that resulted in nonlayering of the exine in these areas, followed by a rotation and binding of the young microspores at the aperture sites.• Small changes in development resulted in clear morphological changes on pollen dispersal time and open a window on the possible selective advantage of the production of aggregated pollen. © 2014 Botanical Society of America, Inc.

EST analysis in Ginkgo biloba: an assessment of conserved developmental regulators and gymnosperm specific genes

PubMed Central

Brenner, Eric D; Katari, Manpreet S; Stevenson, Dennis W; Rudd, Stephen A; Douglas, Andrew W; Moss, Walter N; Twigg, Richard W; Runko, Suzan J; Stellari, Giulia M; McCombie, WR; Coruzzi, Gloria M

2005-01-01

Background Ginkgo biloba L. is the only surviving member of one of the oldest living seed plant groups with medicinal, spiritual and horticultural importance worldwide. As an evolutionary relic, it displays many characters found in the early, extinct seed plants and extant cycads. To establish a molecular base to understand the evolution of seeds and pollen, we created a cDNA library and EST dataset from the reproductive structures of male (microsporangiate), female (megasporangiate), and vegetative organs (leaves) of Ginkgo biloba. Results RNA from newly emerged male and female reproductive organs and immature leaves was used to create three distinct cDNA libraries from which 6,434 ESTs were generated. These 6,434 ESTs from Ginkgo biloba were clustered into 3,830 unigenes. A comparison of our Ginkgo unigene set against the fully annotated genomes of rice and Arabidopsis, and all available ESTs in Genbank revealed that 256 Ginkgo unigenes match only genes among the gymnosperms and non-seed plants – many with multiple matches to genes in non-angiosperm plants. Conversely, another group of unigenes in Gingko had highly significant homology to transcription factors in angiosperms involved in development, including MADS box genes as well as post-transcriptional regulators. Several of the conserved developmental genes found in Ginkgo had top BLAST homology to cycad genes. We also note here the presence of ESTs in G. biloba similar to genes that to date have only been found in gymnosperms and an additional 22 Ginkgo genes common only to genes from cycads. Conclusion Our analysis of an EST dataset from G. biloba revealed genes potentially unique to gymnosperms. Many of these genes showed homology to fully sequenced clones from our cycad EST dataset found in common only with gymnosperms. Other Ginkgo ESTs are similar to developmental regulators in higher plants. This work sets the stage for future studies on Ginkgo to better understand seed and pollen evolution, and to resolve the ambiguous phylogenetic relationship of G. biloba among the gymnosperms. PMID:16225698

Paleoecology and Paleoenvironmental Interpretations of the Late Cretaceous Lower Cantwell Formation, Denali National Park, Alaska

NASA Astrophysics Data System (ADS)

Tomsich, C. S.; Salazar Jaramillo, S.; Jacobus, R. T.; McCarthy, P. J.; Fowell, S. J.; Fiorillo, A. R.

2010-12-01

The level of diversity of an ancient high-latitude fauna or flora is of interest not just for the study of species evolution and paleogeographic migration patterns, but also for the imminent response to an amplified climate change rate. Climate modelers thus focus increasingly on proxies of Polar Regions. A rich floral and faunal record indicative of a warm high-latitude paleoclimate is presently emerging from the late Campanian-Maastrichtian lower Cantwell Formation in Denali National Park, south-central Alaska. This thick (up to 4000m) alluvial fan succession was deposited during the latest accretionary phase of the Wrangellia terrane to the former southern margin of Alaska. Facies descriptions from outcrops near Sable Mountain and Polychrome Mountain record heterogeneous and laterally discontinuous lithologies characteristic of alluvial and marginal alluvial fan environments: braided channel, sandy channel, crevasse splay, sheetflood, floodplain, and lacustrine. Trace and plant fossils occur predominantly at lithological boundaries. The vertebrate fossil record encompasses tracks that can be attributed to fishes, pterosaurs, large and small non-avian theropods, birds, hadrosaurs, and ceratopsians. Hadrosaur footprints are abundant and record populations with multiple generations present. The pterosaur tracks constitute the northernmost fossil occurrence for these flying reptiles. Bird traces range from small, shore-wading bird tracks to those of a large crane-like bird. Diverse invertebrate tracks include freshwater bivalve, ostracode and gastropod trails, crayfish burrows, beetle and mole cricket tracks, wood borings and feeding traces on angiosperm leaves. Plant impression fossils represent dicotyledonous angiosperm leaves referable to nymphaealean, menispermoid, platanoid, trochodendroid and higher hamamelid groups; magnoliid seeds; diverse broad-leaved and blade-like monocot leaf fragments; the leafy shoots, leaves, cones, seeds and wood of cupressaceous and pinaceous conifers; fern fronds; and segments of Equisetites. A climate analysis (CLAMP) on 19 angiosperm morphotypes yields a mean annual temperature of 7.4°C, a warmest monthly mean of 17.1°C and a coldest monthly mean of -2.3°C. Growing season is estimated at 4.8 months. Results indicate a temperate, highly seasonal climate. Closely spaced tree rings in fossil conifer wood and minimal late wood growth suggest a short, rather abrupt ending growing season. The Cantwell flora bears a close resemblance to the late Maastrichtian Koryak flora in northeastern Russia and is characteristic of the Polar Broad-leaved Deciduous Forest that was widespread across the Arctic in the Late Cretaceous and early Tertiary. The late summer sunlight reduction likely limited growth. Rare root casts, a cast of an angiosperm tree stem, trunk impressions and lithified trunk wood provide a glimpse at the sub-boreal forest structure that has been considered one of the causes of amplified polar warming.

Early Cretaceous greenhouse pumped higher taxa diversification in spiders.

PubMed

Shao, Lili; Li, Shuqiang

2018-05-24

The Cretaceous experienced one of the most remarkable greenhouse periods in geological history. During this time, ecosystem reorganizations significantly impacted the diversification of many groups of organisms. The rise of angiosperms marked a major biome turnover. Notwithstanding, relatively little remains known about how the Cretaceous global ecosystem impacted the evolution of spiders, which constitute one of the most abundant groups of predators. Herein, we evaluate the transcriptomes of 91 taxa representing more than half of the spider families. We add 23 newly sequenced taxa to the existing database to obtain a robust phylogenomic assessment. Phylogenetic reconstructions using different datasets and methods obtain novel placements of some groups, especially in the Synspermiata and the group having a retrolateral tibial apophysis (RTA). Molecular analyses indicate an expansion of the RTA clade at the Early Cretaceous with a hunting predatory strategy shift. Fossil analyses show a 7-fold increase of diversification rate at the same period, but this likely owes to the first occurrences spider in amber deposits. Additional analyses of fossil abundance show an accumulation of spider lineages in the Early Cretaceous. We speculate that the establishment of a warm greenhouse climate pumped the diversification of spiders, in particular among webless forms tracking the abundance of insect prey. Our study offers a new pathway for future investigations of spider phylogeny and diversification. Copyright © 2018. Published by Elsevier Inc.

Genome size evolution in relation to leaf strategy and metabolic rates revisited.

PubMed

Beaulieu, Jeremy M; Leitch, Ilia J; Knight, Charles A

2007-03-01

It has been proposed that having too much DNA may carry physiological consequences for plants. The strong correlation between DNA content, cell size and cell division rate could lead to predictable morphological variation in plants, including a negative relationship with leaf mass per unit area (LMA). In addition, the possible increased demand for resources in species with high DNA content may have downstream effects on maximal metabolic efficiency, including decreased metabolic rates. Tests were made for genome size-dependent variation in LMA and metabolic rates (mass-based photosynthetic rate and dark respiration rate) using our own measurements and data from a plant functional trait database (Glopnet). These associations were tested using two metrics of genome size: bulk DNA amount (2C DNA) and monoploid genome size (1Cx DNA). The data were analysed using an evolutionary framework that included a regression analysis and independent contrasts using a phylogenetic tree with estimates of molecular diversification times. A contribution index for the LMA data set was also calculated to determine which divergences have the greatest influence on the relationship between genome size and LMA. A significant negative association was found between bulk DNA amount and LMA in angiosperms. This was primarily a result of influential divergences that may represent early shifts in growth form. However, divergences in bulk DNA amount were positively associated with divergences in LMA, suggesting that the relationship may be indirect and mediated through other traits directly related to genome size. There was a significant negative association between genome size and metabolic rates that was driven by a basal divergence between angiosperms and gymnosperms; no significant independent contrast results were found. Therefore, it is concluded that genome size-dependent constraints acting on metabolic efficiency may not exist within seed plants.

A comparative ultrastructural study of pit membranes with plasmodesmata associated thickenings in four angiosperm species.

PubMed

Rabaey, David; Lens, Frederic; Huysmans, Suzy; Smets, Erik; Jansen, Steven

2008-11-01

Recent micromorphological observations of angiosperm pit membranes have extended the number and range of taxa with pseudo-tori in tracheary elements. This study investigates at ultrastructural level (TEM) the development of pseudo-tori in the unrelated Malus yunnanensis, Ligustrum vulgare, Pittosporum tenuifolium, and Vaccinium myrtillus in order to determine whether these plasmodesmata associated thickenings have a similar developmental pattern across flowering plants. At early ontogenetic stages, the formation of a primary thickening was observed, resulting from swelling of the pit membrane in fibre-tracheids and vessel elements. Since plasmodesmata appear to be frequently, but not always, associated with these primary pit membrane thickenings, it remains unclear which ultrastructural characteristics control the formation of pseudo-tori. At a very late stage during xylem differentiation, a secondary thickening is deposited on the primary pit membrane thickening. Plasmodesmata are always associated with pseudo-tori at these final developmental stages. After autolysis, the secondary thickening becomes electron-dense and persistent, while the primary thickening turns transparent and partially or entirely dissolves. The developmental patterns observed in the species studied are similar and agree with former ontogenetic studies in Rosaceae, suggesting that pseudo-tori might be homologous features across angiosperms.

Early evidence of xeromorphy in angiosperms: stomatal encryption in a new eocene species of Banksia (Proteaceae) from Western Australia.

PubMed

Carpenter, Raymond J; McLoughlin, Stephen; Hill, Robert S; McNamara, Kenneth J; Jordan, Gregory John

2014-09-01

• Globally, the origins of xeromorphic traits in modern angiosperm lineages are obscure but are thought to be linked to the early Neogene onset of seasonally arid climates. Stomatal encryption is a xeromorphic trait that is prominent in Banksia, an archetypal genus centered in one of the world's most diverse ecosystems, the ancient infertile landscape of Mediterranean-climate southwestern Australia.• We describe Banksia paleocrypta, a sclerophyllous species with encrypted stomata from silcretes of the Walebing and Kojonup regions of southwestern Australia dated as Late Eocene.• Banksia paleocrypta shows evidence of foliar xeromorphy ∼20 Ma before the widely accepted timing for the onset of aridity in Australia. Species of Banksia subgenus Banksia with very similar leaves are extant in southwestern Australia. The conditions required for silcrete formation infer fluctuating water tables and climatic seasonality in southwestern Australia in the Eocene, and seasonality is supported by the paucity of angiosperm closed-forest elements among the fossil taxa preserved with B. paleocrypta. However, climates in the region during the Eocene are unlikely to have experienced seasons as hot and dry as present-day summers.• The presence of B. paleocrypta within the center of diversity of subgenus Banksia in edaphically ancient southwestern Australia is consistent with the continuous presence of this lineage in the region for ≥40 Ma, a testament to the success of increasingly xeromorphic traits in Banksia over an interval in which numerous other lineages became extinct. © 2014 Botanical Society of America, Inc.

Functional pleiotropy and mating system evolution in plants: frequency-independent mating.

PubMed

Jordan, Crispin Y; Otto, Sarah P

2012-04-01

Mutations that alter the morphology of floral displays (e.g., flower size) or plant development can change multiple functions simultaneously, such as pollen export and selfing rate. Given the effect of these various traits on fitness, pleiotropy may alter the evolution of both mating systems and floral displays, two characters with high diversity among angiosperms. The influence of viability selection on mating system evolution has not been studied theoretically. We model plant mating system evolution when a single locus simultaneously affects the selfing rate, pollen export, and viability. We assume frequency-independent mating, so our model characterizes prior selfing. Pleiotropy between increased viability and selfing rate reduces opportunities for the evolution of pure outcrossing, can favor complete selfing despite high inbreeding depression, and notably, can cause the evolution of mixed mating despite very high inbreeding depression. These results highlight the importance of pleiotropy for mating system evolution and suggest that selection by nonpollinating agents may help explain mixed mating, particularly in species with very high inbreeding depression. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Global DNA cytosine methylation as an evolving trait: phylogenetic signal and correlated evolution with genome size in angiosperms

PubMed Central

Alonso, Conchita; Pérez, Ricardo; Bazaga, Pilar; Herrera, Carlos M.

2015-01-01

DNA cytosine methylation is a widespread epigenetic mechanism in eukaryotes, and plant genomes commonly are densely methylated. Genomic methylation can be associated with functional consequences such as mutational events, genomic instability or altered gene expression, but little is known on interspecific variation in global cytosine methylation in plants. In this paper, we compare global cytosine methylation estimates obtained by HPLC and use a phylogenetically-informed analytical approach to test for significance of evolutionary signatures of this trait across 54 angiosperm species in 25 families. We evaluate whether interspecific variation in global cytosine methylation is statistically related to phylogenetic distance and also whether it is evolutionarily correlated with genome size (C-value). Global cytosine methylation varied widely between species, ranging between 5.3% (Arabidopsis) and 39.2% (Narcissus). Differences between species were related to their evolutionary trajectories, as denoted by the strong phylogenetic signal underlying interspecific variation. Global cytosine methylation and genome size were evolutionarily correlated, as revealed by the significant relationship between the corresponding phylogenetically independent contrasts. On average, a ten-fold increase in genome size entailed an increase of about 10% in global cytosine methylation. Results show that global cytosine methylation is an evolving trait in angiosperms whose evolutionary trajectory is significantly linked to changes in genome size, and suggest that the evolutionary implications of epigenetic mechanisms are likely to vary between plant lineages. PMID:25688257

A functional phylogenomic view of the seed plants.

PubMed

Lee, Ernest K; Cibrian-Jaramillo, Angelica; Kolokotronis, Sergios-Orestis; Katari, Manpreet S; Stamatakis, Alexandros; Ott, Michael; Chiu, Joanna C; Little, Damon P; Stevenson, Dennis Wm; McCombie, W Richard; Martienssen, Robert A; Coruzzi, Gloria; Desalle, Rob

2011-12-01

A novel result of the current research is the development and implementation of a unique functional phylogenomic approach that explores the genomic origins of seed plant diversification. We first use 22,833 sets of orthologs from the nuclear genomes of 101 genera across land plants to reconstruct their phylogenetic relationships. One of the more salient results is the resolution of some enigmatic relationships in seed plant phylogeny, such as the placement of Gnetales as sister to the rest of the gymnosperms. In using this novel phylogenomic approach, we were also able to identify overrepresented functional gene ontology categories in genes that provide positive branch support for major nodes prompting new hypotheses for genes associated with the diversification of angiosperms. For example, RNA interference (RNAi) has played a significant role in the divergence of monocots from other angiosperms, which has experimental support in Arabidopsis and rice. This analysis also implied that the second largest subunit of RNA polymerase IV and V (NRPD2) played a prominent role in the divergence of gymnosperms. This hypothesis is supported by the lack of 24nt siRNA in conifers, the maternal control of small RNA in the seeds of flowering plants, and the emergence of double fertilization in angiosperms. Our approach takes advantage of genomic data to define orthologs, reconstruct relationships, and narrow down candidate genes involved in plant evolution within a phylogenomic view of species' diversification.

Evolution of the Plant Reproduction Master Regulators LFY and the MADS Transcription Factors: The Role of Protein Structure in the Evolutionary Development of the Flower

PubMed Central

Silva, Catarina S.; Puranik, Sriharsha; Round, Adam; Brennich, Martha; Jourdain, Agnès; Parcy, François; Hugouvieux, Veronique; Zubieta, Chloe

2016-01-01

Understanding the evolutionary leap from non-flowering (gymnosperms) to flowering (angiosperms) plants and the origin and vast diversification of the floral form has been one of the focuses of plant evolutionary developmental biology. The evolving diversity and increasing complexity of organisms is often due to relatively small changes in genes that direct development. These “developmental control genes” and the transcription factors (TFs) they encode, are at the origin of most morphological changes. TFs such as LEAFY (LFY) and the MADS-domain TFs act as central regulators in key developmental processes of plant reproduction including the floral transition in angiosperms and the specification of the male and female organs in both gymnosperms and angiosperms. In addition to advances in genome wide profiling and forward and reverse genetic screening, structural techniques are becoming important tools in unraveling TF function by providing atomic and molecular level information that was lacking in purely genetic approaches. Here, we summarize previous structural work and present additional biophysical and biochemical studies of the key master regulators of plant reproduction – LEAFY and the MADS-domain TFs SEPALLATA3 and AGAMOUS. We discuss the impact of structural biology on our understanding of the complex evolutionary process leading to the development of the bisexual flower. PMID:26779227

A Functional Phylogenomic View of the Seed Plants

PubMed Central

Katari, Manpreet S.; Stamatakis, Alexandros; Ott, Michael; Chiu, Joanna C.; Little, Damon P.; Stevenson, Dennis Wm.; McCombie, W. Richard; Martienssen, Robert A.; Coruzzi, Gloria; DeSalle, Rob

2011-01-01

A novel result of the current research is the development and implementation of a unique functional phylogenomic approach that explores the genomic origins of seed plant diversification. We first use 22,833 sets of orthologs from the nuclear genomes of 101 genera across land plants to reconstruct their phylogenetic relationships. One of the more salient results is the resolution of some enigmatic relationships in seed plant phylogeny, such as the placement of Gnetales as sister to the rest of the gymnosperms. In using this novel phylogenomic approach, we were also able to identify overrepresented functional gene ontology categories in genes that provide positive branch support for major nodes prompting new hypotheses for genes associated with the diversification of angiosperms. For example, RNA interference (RNAi) has played a significant role in the divergence of monocots from other angiosperms, which has experimental support in Arabidopsis and rice. This analysis also implied that the second largest subunit of RNA polymerase IV and V (NRPD2) played a prominent role in the divergence of gymnosperms. This hypothesis is supported by the lack of 24nt siRNA in conifers, the maternal control of small RNA in the seeds of flowering plants, and the emergence of double fertilization in angiosperms. Our approach takes advantage of genomic data to define orthologs, reconstruct relationships, and narrow down candidate genes involved in plant evolution within a phylogenomic view of species' diversification. PMID:22194700

Analysis of the APETALA3- and PISTILLATA-like genes in Hedyosmum orientale (Chloranthaceae) provides insight into the evolution of the floral homeotic B-function in angiosperms

PubMed Central

Liu, Shujun; Sun, Yonghua; Du, Xiaoqiu; Xu, Qijiang; Wu, Feng; Meng, Zheng

2013-01-01

Background and Aims According to the floral ABC model, B-function genes appear to play a key role in the origin and diversification of the perianth during the evolution of angiosperms. The basal angiosperm Hedyosmum orientale (Chloranthaceae) has unisexual inflorescences associated with a seemingly primitive reproductive morphology and a reduced perianth structure in female flowers. The aim of this study was to investigate the nature of the perianth and the evolutionary state of the B-function programme in this species. Methods A series of experiments were conducted to characterize B-gene homologues isolated from H. orientale, including scanning electron microscopy to observe the development of floral organs, phylogenetic analysis to reconstruct gene evolutionary history, reverse transcription–PCR, quantitative real-time PCR and in situ hybridization to identify gene expression patterns, the yeast two-hybrid assay to explore protein dimerization affinities, and transgenic analyses in Arabidopsis thaliana to determine activities of the encoded proteins. Key Results The expression of HoAP3 genes was restricted to stamens, whereas HoPI genes were broadly expressed in all floral organs. HoAP3 was able to partially restore the stamen but not petal identity in Arabidopsis ap3-3 mutants. In contrast, HoPI could rescue aspects of both stamen and petal development in Arabidopsis pi-1 mutants. When the complete C-terminal sequence of HoPI was deleted, however, no or weak transgenic phenotypes were observed and homodimerization capability was completely abolished. Conclusions The results suggest that Hedyosmum AP3-like genes have an ancestral function in specifying male reproductive organs, and that the activity of the encoded PI-like proteins is highly conserved between Hedyosmum and Arabidopsis. Moreover, there is evidence that the C-terminal region is important for the function of HoPI. Our findings indicate that the development of the proposed perianth in Hedyosmum does not rely on the B homeotic function. PMID:23956161

Evolutionary history of the angiosperm flora of China.

PubMed

Lu, Li-Min; Mao, Ling-Feng; Yang, Tuo; Ye, Jian-Fei; Liu, Bing; Li, Hong-Lei; Sun, Miao; Miller, Joseph T; Mathews, Sarah; Hu, Hai-Hua; Niu, Yan-Ting; Peng, Dan-Xiao; Chen, You-Hua; Smith, Stephen A; Chen, Min; Xiang, Kun-Li; Le, Chi-Toan; Dang, Viet-Cuong; Lu, An-Ming; Soltis, Pamela S; Soltis, Douglas E; Li, Jian-Hua; Chen, Zhi-Duan

2018-02-08

High species diversity may result from recent rapid speciation in a 'cradle' and/or the gradual accumulation and preservation of species over time in a 'museum'. China harbours nearly 10% of angiosperm species worldwide and has long been considered as both a museum, owing to the presence of many species with hypothesized ancient origins, and a cradle, as many lineages have originated as recent topographic changes and climatic shifts-such as the formation of the Qinghai-Tibetan Plateau and the development of the monsoon-provided new habitats that promoted remarkable radiation. However, no detailed phylogenetic study has addressed when and how the major components of the Chinese angiosperm flora assembled to form the present-day vegetation. Here we investigate the spatio-temporal divergence patterns of the Chinese flora using a dated phylogeny of 92% of the angiosperm genera for the region, a nearly complete species-level tree comprising 26,978 species and detailed spatial distribution data. We found that 66% of the angiosperm genera in China did not originate until early in the Miocene epoch (23 million years ago (Mya)). The flora of eastern China bears a signature of older divergence (mean divergence times of 22.04-25.39 Mya), phylogenetic overdispersion (spatial co-occurrence of distant relatives) and higher phylogenetic diversity. In western China, the flora shows more recent divergence (mean divergence times of 15.29-18.86 Mya), pronounced phylogenetic clustering (co-occurrence of close relatives) and lower phylogenetic diversity. Analyses of species-level phylogenetic diversity using simulated branch lengths yielded results similar to genus-level patterns. Our analyses indicate that eastern China represents a floristic museum, and western China an evolutionary cradle, for herbaceous genera; eastern China has served as both a museum and a cradle for woody genera. These results identify areas of high species richness and phylogenetic diversity, and provide a foundation on which to build conservation efforts in China.

Evolutionary history of the angiosperm flora of China

NASA Astrophysics Data System (ADS)

Lu, Li-Min; Mao, Ling-Feng; Yang, Tuo; Ye, Jian-Fei; Liu, Bing; Li, Hong-Lei; Sun, Miao; Miller, Joseph T.; Mathews, Sarah; Hu, Hai-Hua; Niu, Yan-Ting; Peng, Dan-Xiao; Chen, You-Hua; Smith, Stephen A.; Chen, Min; Xiang, Kun-Li; Le, Chi-Toan; Dang, Viet-Cuong; Lu, An-Ming; Soltis, Pamela S.; Soltis, Douglas E.; Li, Jian-Hua; Chen, Zhi-Duan

2018-02-01

High species diversity may result from recent rapid speciation in a ‘cradle’ and/or the gradual accumulation and preservation of species over time in a ‘museum’. China harbours nearly 10% of angiosperm species worldwide and has long been considered as both a museum, owing to the presence of many species with hypothesized ancient origins, and a cradle, as many lineages have originated as recent topographic changes and climatic shifts—such as the formation of the Qinghai-Tibetan Plateau and the development of the monsoon—provided new habitats that promoted remarkable radiation. However, no detailed phylogenetic study has addressed when and how the major components of the Chinese angiosperm flora assembled to form the present-day vegetation. Here we investigate the spatio-temporal divergence patterns of the Chinese flora using a dated phylogeny of 92% of the angiosperm genera for the region, a nearly complete species-level tree comprising 26,978 species and detailed spatial distribution data. We found that 66% of the angiosperm genera in China did not originate until early in the Miocene epoch (23 million years ago (Mya)). The flora of eastern China bears a signature of older divergence (mean divergence times of 22.04-25.39 Mya), phylogenetic overdispersion (spatial co-occurrence of distant relatives) and higher phylogenetic diversity. In western China, the flora shows more recent divergence (mean divergence times of 15.29-18.86 Mya), pronounced phylogenetic clustering (co-occurrence of close relatives) and lower phylogenetic diversity. Analyses of species-level phylogenetic diversity using simulated branch lengths yielded results similar to genus-level patterns. Our analyses indicate that eastern China represents a floristic museum, and western China an evolutionary cradle, for herbaceous genera; eastern China has served as both a museum and a cradle for woody genera. These results identify areas of high species richness and phylogenetic diversity, and provide a foundation on which to build conservation efforts in China.

High richness of insect herbivory from the early Miocene Hindon Maar crater, Otago, New Zealand

PubMed Central

Lee, Daphne E.; Wappler, Torsten

2017-01-01

Plants and insects are key components of terrestrial ecosystems and insect herbivory is the most important type of interaction in these ecosystems. This study presents the first analysis of associations between plants and insects for the early Miocene Hindon Maar fossil lagerstätte, Otago, New Zealand. A total of 584 fossil angiosperm leaves representing 24 morphotypes were examined to determine the presence or absence of insect damage types. Of these leaves, 73% show signs of insect damage; they comprise 821 occurrences of damage from 87 damage types representing all eight functional feeding groups. In comparison to other fossil localities, the Hindon leaves display a high abundance of insect damage and a high diversity of damage types. Leaves of Nothofagus(southern beech), the dominant angiosperm in the fossil assemblage, exhibit a similar leaf damage pattern to leaves from the nearby mid to late Miocene Dunedin Volcano Group sites but display a more diverse spectrum and much higher percentage of herbivory damage than a comparable dataset of leaves from Palaeocene and Eocene sites in the Antarctic Peninsula. PMID:28224051

Modes of gene duplication contribute differently to genetic novelty and redundancy, but show parallels across divergent angiosperms.

PubMed

Wang, Yupeng; Wang, Xiyin; Tang, Haibao; Tan, Xu; Ficklin, Stephen P; Feltus, F Alex; Paterson, Andrew H

2011-01-01

Both single gene and whole genome duplications (WGD) have recurred in angiosperm evolution. However, the evolutionary effects of different modes of gene duplication, especially regarding their contributions to genetic novelty or redundancy, have been inadequately explored. In Arabidopsis thaliana and Oryza sativa (rice), species that deeply sample botanical diversity and for which expression data are available from a wide range of tissues and physiological conditions, we have compared expression divergence between genes duplicated by six different mechanisms (WGD, tandem, proximal, DNA based transposed, retrotransposed and dispersed), and between positional orthologs. Both neo-functionalization and genetic redundancy appear to contribute to retention of duplicate genes. Genes resulting from WGD and tandem duplications diverge slowest in both coding sequences and gene expression, and contribute most to genetic redundancy, while other duplication modes contribute more to evolutionary novelty. WGD duplicates may more frequently be retained due to dosage amplification, while inferred transposon mediated gene duplications tend to reduce gene expression levels. The extent of expression divergence between duplicates is discernibly related to duplication modes, different WGD events, amino acid divergence, and putatively neutral divergence (time), but the contribution of each factor is heterogeneous among duplication modes. Gene loss may retard inter-species expression divergence. Members of different gene families may have non-random patterns of origin that are similar in Arabidopsis and rice, suggesting the action of pan-taxon principles of molecular evolution. Gene duplication modes differ in contribution to genetic novelty and redundancy, but show some parallels in taxa separated by hundreds of millions of years of evolution.

Modes of Gene Duplication Contribute Differently to Genetic Novelty and Redundancy, but Show Parallels across Divergent Angiosperms

PubMed Central

Wang, Yupeng; Wang, Xiyin; Tang, Haibao; Tan, Xu; Ficklin, Stephen P.; Feltus, F. Alex; Paterson, Andrew H.

2011-01-01

Background Both single gene and whole genome duplications (WGD) have recurred in angiosperm evolution. However, the evolutionary effects of different modes of gene duplication, especially regarding their contributions to genetic novelty or redundancy, have been inadequately explored. Results In Arabidopsis thaliana and Oryza sativa (rice), species that deeply sample botanical diversity and for which expression data are available from a wide range of tissues and physiological conditions, we have compared expression divergence between genes duplicated by six different mechanisms (WGD, tandem, proximal, DNA based transposed, retrotransposed and dispersed), and between positional orthologs. Both neo-functionalization and genetic redundancy appear to contribute to retention of duplicate genes. Genes resulting from WGD and tandem duplications diverge slowest in both coding sequences and gene expression, and contribute most to genetic redundancy, while other duplication modes contribute more to evolutionary novelty. WGD duplicates may more frequently be retained due to dosage amplification, while inferred transposon mediated gene duplications tend to reduce gene expression levels. The extent of expression divergence between duplicates is discernibly related to duplication modes, different WGD events, amino acid divergence, and putatively neutral divergence (time), but the contribution of each factor is heterogeneous among duplication modes. Gene loss may retard inter-species expression divergence. Members of different gene families may have non-random patterns of origin that are similar in Arabidopsis and rice, suggesting the action of pan-taxon principles of molecular evolution. Conclusion Gene duplication modes differ in contribution to genetic novelty and redundancy, but show some parallels in taxa separated by hundreds of millions of years of evolution. PMID:22164235

Repeated evolution of tricellular (and bicellular) pollen.

PubMed

Williams, Joseph H; Taylor, Mackenzie L; O'Meara, Brian C

2014-04-01

Male gametophytes of seed plants are sexually immature at the time they are dispersed as pollen, but approximately 30% of flowering plants have tricellular pollen containing fully formed sperm at anthesis. The classic study of Brewbaker (1967: American Journal of Botany 54: 1069-1083) provided a powerful confirmation of the long-standing hypothesis that tricellular pollen had many parallel and irreversible origins within angiosperms. We readdressed the main questions of that study with modern comparative phylogenetic methods. We used our own and more recent reports to greatly expand the Brewbaker data set. We modeled trait evolution for 2511 species on a time-calibrated angiosperm phylogeny using (1) Binary State Speciation and Extinction (BiSSE), which accounts for the effect of species diversification rates on character transition rates and, (2) the hidden rates model (HRM), which incorporates variation in transition rates across a phylogeny. Seventy percent of species had bicellular pollen. BiSSE found a 1.9-fold higher bicellular to tricellular transition rate than in the reverse direction, and bicellular lineages had a 1.8-fold higher diversification rate than tricellular lineages. HRM found heterogeneity in evolutionary rates, with bidirectional transition rates in three of four rate classes. The tricellular condition is not irreversible. Pollen cell numbers are maintained at intermediate frequencies because lower net diversification rates of tricellular lineages are counterbalanced by slower state shifts to the bicellular condition. That tricellular lineages diversify slowly and give rise to bicellular lineages slowly reflects a linkage between the evolution of sporophyte lifestyles and the developmental lability of male gametophytes.

Leaf fossil record suggests limited influence of atmospheric CO2 on terrestrial productivity prior to angiosperm evolution

PubMed Central

Boyce, C. Kevin; Zwieniecki, Maciej A.

2012-01-01

Declining CO2 over the Cretaceous has been suggested as an evolutionary driver of the high leaf vein densities (7–28 mm mm−2) that are unique to the angiosperms throughout all of Earth history. Photosynthetic modeling indicated the link between high vein density and productivity documented in the modern low-CO2 regime would be lost as CO2 concentrations increased but also implied that plants with very low vein densities (less than 3 mm mm−2) should experience substantial disadvantages with high CO2. Thus, the hypothesized relationship between CO2 and plant evolution can be tested through analysis of the concurrent histories of alternative lineages, because an extrinsic driver like atmospheric CO2 should affect all plants and not just the flowering plants. No such relationship is seen. Regardless of CO2 concentrations, low vein densities are equally common among nonangiosperms throughout history and common enough to include forest canopies and not just obligate shade species that will always be of limited productivity. Modeling results can be reconciled with the fossil record if maximum assimilation rates of nonflowering plants are capped well below those of flowering plants, capturing biochemical and physiological differences that would be consistent with extant plants but previously unrecognized in the fossil record. Although previous photosynthetic modeling suggested that productivity would double or triple with each Phanerozoic transition from low to high CO2, productivity changes are likely to have been limited before a substantial increase accompanying the evolution of flowering plants. PMID:22689947

Genomic Repeat Abundances Contain Phylogenetic Signal

PubMed Central

Dodsworth, Steven; Chase, Mark W.; Kelly, Laura J.; Leitch, Ilia J.; Macas, Jiří; Novák, Petr; Piednoël, Mathieu; Weiss-Schneeweiss, Hanna; Leitch, Andrew R.

2015-01-01

A large proportion of genomic information, particularly repetitive elements, is usually ignored when researchers are using next-generation sequencing. Here we demonstrate the usefulness of this repetitive fraction in phylogenetic analyses, utilizing comparative graph-based clustering of next-generation sequence reads, which results in abundance estimates of different classes of genomic repeats. Phylogenetic trees are then inferred based on the genome-wide abundance of different repeat types treated as continuously varying characters; such repeats are scattered across chromosomes and in angiosperms can constitute a majority of nuclear genomic DNA. In six diverse examples, five angiosperms and one insect, this method provides generally well-supported relationships at interspecific and intergeneric levels that agree with results from more standard phylogenetic analyses of commonly used markers. We propose that this methodology may prove especially useful in groups where there is little genetic differentiation in standard phylogenetic markers. At the same time as providing data for phylogenetic inference, this method additionally yields a wealth of data for comparative studies of genome evolution. PMID:25261464

Reinvestigating an enigmatic Late Cretaceous monocot: morphology, taxonomy, and biogeography of Viracarpon

PubMed Central

Manchester, Steven R.; Ramteke, Deepak; Villarraga-Gómez, Herminso

2018-01-01

Angiosperm-dominated floras of the Late Cretaceous are essential for understanding the evolutionary, ecological, and geographic radiation of flowering plants. The Late Cretaceous–early Paleogene Deccan Intertrappean Beds of India contain angiosperm-dominated plant fossil assemblages known from multiple localities in central India. Numerous monocots have been documented from these assemblages, providing a window into an important but poorly understood time in their diversification. One component of the Deccan monocot diversity is the genus Viracarpon, known from anatomically preserved infructescences. Viracarpon was first collected over a century ago and has been the subject of numerous studies. However, resolution of its three-dimensional (3D) morphology and anatomy, as well as its taxonomic affinities, has remained elusive. In this study we investigated the morphology and taxonomy of genus Viracarpon, combining traditional paleobotanical techniques and X-ray micro-computed tomography (μCT). Re-examination of type and figured specimens, 3D reconstructions of fruits, and characterization of structures in multiple planes of section using μCT data allowed us to resolve conflicting interpretations of fruit morphology and identify additional characters useful in refining potential taxonomic affinities. Among the four Viracarpon species previously recognized, we consider two to be valid (Viracarpon hexaspermum and Viracarpon elongatum), and the other two to be synonyms of these. Furthermore, we found that permineralized infructescences of Coahuilocarpon phytolaccoides from the late Campanian of Mexico correspond closely in morphology to V. hexaspermum. We argue that Viracarpon and Coahuilocarpon are congeneric and provide the new combination, Viracarpon phytolaccoides (Cevallos-Ferriz, Estrada-Ruiz & Perez-Hernandez) Matsunaga, S.Y. Smith, & Manchester comb. nov. The significant geographic disjunction between these two occurrences indicates that the genus Viracarpon was widespread and may be present in other Late Cretaceous assemblages. Viracarpon exhibits character combinations not present in any extant taxa and its affinities remain unresolved, possibly representing an extinct member of Alismatales. The character mosaic observed in Viracarpon and the broad distribution of the genus provide new data relevant to understanding early monocot evolution and suggest that the (thus far) largely invisible Late Cretaceous monocot diversification was characterized by enigmatic and/or stem taxa. PMID:29637023

Functional diversification of B MADS-box homeotic regulators of flower development: Adaptive evolution in protein-protein interaction domains after major gene duplication events.

PubMed

Hernández-Hernández, Tania; Martínez-Castilla, León Patricio; Alvarez-Buylla, Elena R

2007-02-01

B-class MADS-box genes have been shown to be the key regulators of petal and stamen specification in several eudicot model species such as Arabidopsis thaliana, Antirrhinum majus, and Petunia hybrida. Orthologs of these genes have been found across angiosperms and gymnosperms, and it is thought that the basic regulatory function of B proteins is conserved in seed plant lineages. The evolution of B genes is characterized by numerous duplications that might represent key elements fostering the functional diversification of duplicates with a deep impact on their role in the evolution of the floral developmental program. To evaluate this, we performed a rigorous statistical analysis with B gene sequences. Using maximum likelihood and Bayesian methods, we estimated molecular substitution rates and determined the selective regimes operating at each residue of B proteins. We implemented tests that rely on phylogenetic hypotheses and codon substitution models to detect significant differences in substitution rates (DSRs) and sites under positive adaptive selection (PS) in specific lineages before and after duplication events. With these methods, we identified several protein residues fixed by PS shortly after the origin of PISTILLATA-like and APETALA3-like lineages in angiosperms and shortly after the origin of the euAP3-like lineage in core eudicots, the 2 main B gene duplications. The residues inferred to have been fixed by positive selection lie mostly within the K domain of the protein, which is key to promote heterodimerization. Additionally, we used a likelihood method that accommodates DSRs among lineages to estimate duplication dates for AP3-PI and euAP3-TM6, calibrating with data from the fossil record. The dates obtained are consistent with angiosperm origins and diversification of core eudicots. Our results strongly suggest that novel multimer formation with other MADS proteins could have been crucial for the functional divergence of B MADS-box genes. We thus propose a mechanism of functional diversification and persistence of gene duplicates by the appearance of novel multimerization capabilities after duplications. Multimer formation in different combinations of regulatory proteins can be a mechanistic basis for the origin of novel regulatory functions and a gene regulatory mechanism for the appearance of morphological innovations.

Insights into the Evolution of Hydroxyproline-Rich Glycoproteins from 1000 Plant Transcriptomes1[OPEN

PubMed Central

Cassin, Andrew M.; Soltis, Douglas E.; Miles, Nicholas W.; Melkonian, Michael; Melkonian, Barbara; Wu, Shuangxiu; Edger, Patrick P.; Carpenter, Eric J.

2017-01-01

The carbohydrate-rich cell walls of land plants and algae have been the focus of much interest given the value of cell wall-based products to our current and future economies. Hydroxyproline-rich glycoproteins (HRGPs), a major group of wall glycoproteins, play important roles in plant growth and development, yet little is known about how they have evolved in parallel with the polysaccharide components of walls. We investigate the origins and evolution of the HRGP superfamily, which is commonly divided into three major multigene families: the arabinogalactan proteins (AGPs), extensins (EXTs), and proline-rich proteins. Using motif and amino acid bias, a newly developed bioinformatics pipeline, we identified HRGPs in sequences from the 1000 Plants transcriptome project (www.onekp.com). Our analyses provide new insights into the evolution of HRGPs across major evolutionary milestones, including the transition to land and the early radiation of angiosperms. Significantly, data mining reveals the origin of glycosylphosphatidylinositol (GPI)-anchored AGPs in green algae and a 3- to 4-fold increase in GPI-AGPs in liverworts and mosses. The first detection of cross-linking (CL)-EXTs is observed in bryophytes, which suggests that CL-EXTs arose though the juxtaposition of preexisting SPn EXT glycomotifs with refined Y-based motifs. We also detected the loss of CL-EXT in a few lineages, including the grass family (Poaceae), that have a cell wall composition distinct from other monocots and eudicots. A key challenge in HRGP research is tracking individual HRGPs throughout evolution. Using the 1000 Plants output, we were able to find putative orthologs of Arabidopsis pollen-specific GPI-AGPs in basal eudicots. PMID:28446636

Insights into the Evolution of Hydroxyproline-Rich Glycoproteins from 1000 Plant Transcriptomes.

PubMed

Johnson, Kim L; Cassin, Andrew M; Lonsdale, Andrew; Wong, Gane Ka-Shu; Soltis, Douglas E; Miles, Nicholas W; Melkonian, Michael; Melkonian, Barbara; Deyholos, Michael K; Leebens-Mack, James; Rothfels, Carl J; Stevenson, Dennis W; Graham, Sean W; Wang, Xumin; Wu, Shuangxiu; Pires, J Chris; Edger, Patrick P; Carpenter, Eric J; Bacic, Antony; Doblin, Monika S; Schultz, Carolyn J

2017-06-01

The carbohydrate-rich cell walls of land plants and algae have been the focus of much interest given the value of cell wall-based products to our current and future economies. Hydroxyproline-rich glycoproteins (HRGPs), a major group of wall glycoproteins, play important roles in plant growth and development, yet little is known about how they have evolved in parallel with the polysaccharide components of walls. We investigate the origins and evolution of the HRGP superfamily, which is commonly divided into three major multigene families: the arabinogalactan proteins (AGPs), extensins (EXTs), and proline-rich proteins. Using motif and amino acid bias, a newly developed bioinformatics pipeline, we identified HRGPs in sequences from the 1000 Plants transcriptome project (www.onekp.com). Our analyses provide new insights into the evolution of HRGPs across major evolutionary milestones, including the transition to land and the early radiation of angiosperms. Significantly, data mining reveals the origin of glycosylphosphatidylinositol (GPI)-anchored AGPs in green algae and a 3- to 4-fold increase in GPI-AGPs in liverworts and mosses. The first detection of cross-linking (CL)-EXTs is observed in bryophytes, which suggests that CL-EXTs arose though the juxtaposition of preexisting SP n EXT glycomotifs with refined Y-based motifs. We also detected the loss of CL-EXT in a few lineages, including the grass family (Poaceae), that have a cell wall composition distinct from other monocots and eudicots. A key challenge in HRGP research is tracking individual HRGPs throughout evolution. Using the 1000 Plants output, we were able to find putative orthologs of Arabidopsis pollen-specific GPI-AGPs in basal eudicots. © 2017 American Society of Plant Biologists. All Rights Reserved.

Coevolution between Nuclear-Encoded DNA Replication, Recombination, and Repair Genes and Plastid Genome Complexity

PubMed Central

Zhang, Jin; Ruhlman, Tracey A.; Sabir, Jamal S. M.; Blazier, John Chris; Weng, Mao-Lun; Park, Seongjun; Jansen, Robert K.

2016-01-01

Disruption of DNA replication, recombination, and repair (DNA-RRR) systems has been hypothesized to cause highly elevated nucleotide substitution rates and genome rearrangements in the plastids of angiosperms, but this theory remains untested. To investigate nuclear–plastid genome (plastome) coevolution in Geraniaceae, four different measures of plastome complexity (rearrangements, repeats, nucleotide insertions/deletions, and substitution rates) were evaluated along with substitution rates of 12 nuclear-encoded, plastid-targeted DNA-RRR genes from 27 Geraniales species. Significant correlations were detected for nonsynonymous (dN) but not synonymous (dS) substitution rates for three DNA-RRR genes (uvrB/C, why1, and gyrA) supporting a role for these genes in accelerated plastid genome evolution in Geraniaceae. Furthermore, correlation between dN of uvrB/C and plastome complexity suggests the presence of nucleotide excision repair system in plastids. Significant correlations were also detected between plastome complexity and 13 of the 90 nuclear-encoded organelle-targeted genes investigated. Comparisons revealed significant acceleration of dN in plastid-targeted genes of Geraniales relative to Brassicales suggesting this correlation may be an artifact of elevated rates in this gene set in Geraniaceae. Correlation between dN of plastid-targeted DNA-RRR genes and plastome complexity supports the hypothesis that the aberrant patterns in angiosperm plastome evolution could be caused by dysfunction in DNA-RRR systems. PMID:26893456

Back to the sea twice: identifying candidate plant genes for molecular evolution to marine life.

PubMed

Wissler, Lothar; Codoñer, Francisco M; Gu, Jenny; Reusch, Thorsten B H; Olsen, Jeanine L; Procaccini, Gabriele; Bornberg-Bauer, Erich

2011-01-12

Seagrasses are a polyphyletic group of monocotyledonous angiosperms that have adapted to a completely submerged lifestyle in marine waters. Here, we exploit two collections of expressed sequence tags (ESTs) of two wide-spread and ecologically important seagrass species, the Mediterranean seagrass Posidonia oceanica (L.) Delile and the eelgrass Zostera marina L., which have independently evolved from aquatic ancestors. This replicated, yet independent evolutionary history facilitates the identification of traits that may have evolved in parallel and are possible instrumental candidates for adaptation to a marine habitat. In our study, we provide the first quantitative perspective on molecular adaptations in two seagrass species. By constructing orthologous gene clusters shared between two seagrasses (Z. marina and P. oceanica) and eight distantly related terrestrial angiosperm species, 51 genes could be identified with detection of positive selection along the seagrass branches of the phylogenetic tree. Characterization of these positively selected genes using KEGG pathways and the Gene Ontology uncovered that these genes are mostly involved in translation, metabolism, and photosynthesis. These results provide first insights into which seagrass genes have diverged from their terrestrial counterparts via an initial aquatic stage characteristic of the order and to the derived fully-marine stage characteristic of seagrasses. We discuss how adaptive changes in these processes may have contributed to the evolution towards an aquatic and marine existence.

The shoot stem cell niche in angiosperms: expression patterns of WUS orthologues in rice and maize imply major modifications in the course of mono- and dicot evolution.

PubMed

Nardmann, Judith; Werr, Wolfgang

2006-12-01

In Arabidopsis, stem cell homeostasis in the shoot apical meristem (SAM) is controlled by a feedback loop between WUS and CLV functions. We have identified WUS orthologues in maize and rice by a detailed phylogenetic analysis of the WOX gene family and subsequent cloning. A single WUS orthologue is present in the rice genome (OsWUS), whereas the allotetraploid maize genome contains 2 WUS paralogues (ZmWUS1 and ZmWUS2). None of the isolated grass WUS orthologues displays an organizing center-type expression pattern in the vegetative SAM as in Arabidopsis. In contrast, the grass-specific expression patterns relate to the specification of new phytomers consistent with the transcriptional expression patterns of TD1 and FON1 (CLV1 orthologues of maize and rice, respectively). Moreover, the grass WUS and CLV1 orthologues are coexpressed in all reproductive meristems, where fasciation and supernumerary floral organs occur in td1 or fon1 loss-of-function mutants. The expression patterns of WUS orthologues in both grass species compared with those of dicots imply that major changes in WUS function, which are correlated with changes in CLV1 signaling, have occurred during angiosperm evolution and raise doubts about the uniqueness of the WUS/CLV antagonism in the maintenance of the shoot stem cell niche in grasses.

Height-related scaling of phloem anatomy and the evolution of sieve element end wall types in woody plants.

PubMed

Liesche, Johannes; Pace, Marcelo R; Xu, Qiyu; Li, Yongqing; Chen, Shaolin

2017-04-01

In the sieve elements (SEs) of the phloem, carbohydrates are transported throughout the whole plant from their site of production to sites of consumption or storage. SE structure, especially of the pore-rich end walls, has a direct effect on translocation efficiency. Differences in pore size and other features were interpreted as an evolutionary trend towards reduced hydraulic resistance. However, this has never been confirmed. Anatomical data of 447 species of woody angiosperms and gymnosperms were used for a phylogenetic analysis of end wall types, calculation of hydraulic resistance and correlation analysis with morphological and physiological variables. end wall types were defined according to pore arrangement: either grouped into a single area (simple) or into multiple areas along the end wall (compound). Convergent evolution of end wall types was demonstrated in woody angiosperms. In addition, an optimization of end wall resistance with plant height was discovered, but found to be independent of end wall type. While physiological factors also showed no correlation with end wall types, the number of sieve areas per end wall was found to scale with SE length. The results exclude the minimization of hydraulic resistance as evolutionary driver of different end wall types, contradicting this long-standing assumption. Instead, end wall type might depend on SE length. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

A Molecular Phylogeny for Yponomeutoidea (Insecta, Lepidoptera, Ditrysia) and Its Implications for Classification, Biogeography and the Evolution of Host Plant Use

PubMed Central

Sohn, Jae-Cheon; Regier, Jerome C.; Mitter, Charles; Davis, Donald; Landry, Jean-François; Zwick, Andreas; Cummings, Michael P.

2013-01-01

Background Yponomeutoidea, one of the early-diverging lineages of ditrysian Lepidoptera, comprise about 1,800 species worldwide, including notable pests and insect-plant interaction models. Yponomeutoids were one of the earliest lepidopteran clades to evolve external feeding and to extensively colonize herbaceous angiosperms. Despite the group’s economic importance, and its value for tracing early lepidopteran evolution, the biodiversity and phylogeny of Yponomeutoidea have been relatively little studied. Methodology/Principal Findings Eight nuclear genes (8 kb) were initially sequenced for 86 putative yponomeutoid species, spanning all previously recognized suprageneric groups, and 53 outgroups representing 22 families and 12 superfamilies. Eleven to 19 additional genes, yielding a total of 14.8 to 18.9 kb, were then sampled for a subset of taxa, including 28 yponomeutoids and 43 outgroups. Maximum likelihood analyses were conducted on data sets differing in numbers of genes, matrix completeness, inclusion/weighting of synonymous substitutions, and inclusion/exclusion of “rogue” taxa. Monophyly for Yponomeutoidea was supported very strongly when the 18 “rogue” taxa were excluded, and moderately otherwise. Results from different analyses are highly congruent and relationships within Yponomeutoidea are well supported overall. There is strong support overall for monophyly of families previously recognized on morphological grounds, including Yponomeutidae, Ypsolophidae, Plutellidae, Glyphipterigidae, Argyresthiidae, Attevidae, Praydidae, Heliodinidae, and Bedelliidae. We also assign family rank to Scythropiinae (Scythropiidae stat. rev.), which in our trees are strongly grouped with Bedelliidae, in contrast to all previous proposals. We present a working hypothesis of among-family relationships, and an informal higher classification. Host plant family associations of yponomeutoid subfamilies and families are non-random, but show no trends suggesting parallel phylogenesis. Our analyses suggest that previous characterizations of yponomeutoids as predominantly Holarctic were based on insufficient sampling. Conclusions/Significance We provide the first robust molecular phylogeny for Yponomeutoidea, together with a revised classification and new insights into their life history evolution and biogeography. PMID:23383061

Why should we investigate the morphological disparity of plant clades?

PubMed Central

Oyston, Jack W.; Hughes, Martin; Gerber, Sylvain; Wills, Matthew A.

2016-01-01

Background Disparity refers to the morphological variation in a sample of taxa, and is distinct from diversity or taxonomic richness. Diversity and disparity are fundamentally decoupled; many groups attain high levels of disparity early in their evolution, while diversity is still comparatively low. Diversity may subsequently increase even in the face of static or declining disparity by increasingly fine sub-division of morphological ‘design’ space (morphospace). Many animal clades reached high levels of disparity early in their evolution, but there have been few comparable studies of plant clades, despite their profound ecological and evolutionary importance. This study offers a prospective and some preliminary macroevolutionary analyses. Methods Classical morphometric methods are most suitable when there is reasonable conservation of form, but lose traction where morphological differences become greater (e.g. in comparisons across higher taxa). Discrete character matrices offer one means to compare a greater diversity of forms. This study explores morphospaces derived from eight discrete data sets for major plant clades, and discusses their macroevolutionary implications. Key Results Most of the plant clades in this study show initial, high levels of disparity that approach or attain the maximum levels reached subsequently. These plant clades are characterized by an initial phase of evolution during which most regions of their empirical morphospaces are colonized. Angiosperms, palms, pines and ferns show remarkably little variation in disparity through time. Conifers furnish the most marked exception, appearing at relatively low disparity in the latest Carboniferous, before expanding incrementally with the radiation of successive, tightly clustered constituent sub-clades. Conclusions Many cladistic data sets can be repurposed for investigating the morphological disparity of plant clades through time, and offer insights that are complementary to more focused morphometric studies. The unique structural and ecological features of plants make them ideally suited to investigating intrinsic and extrinsic constraints on disparity. PMID:26658292

Why should we investigate the morphological disparity of plant clades?

PubMed

Oyston, Jack W; Hughes, Martin; Gerber, Sylvain; Wills, Matthew A

2016-04-01

Disparity refers to the morphological variation in a sample of taxa, and is distinct from diversity or taxonomic richness. Diversity and disparity are fundamentally decoupled; many groups attain high levels of disparity early in their evolution, while diversity is still comparatively low. Diversity may subsequently increase even in the face of static or declining disparity by increasingly fine sub-division of morphological 'design' space (morphospace). Many animal clades reached high levels of disparity early in their evolution, but there have been few comparable studies of plant clades, despite their profound ecological and evolutionary importance. This study offers a prospective and some preliminary macroevolutionary analyses. Classical morphometric methods are most suitable when there is reasonable conservation of form, but lose traction where morphological differences become greater (e.g. in comparisons across higher taxa). Discrete character matrices offer one means to compare a greater diversity of forms. This study explores morphospaces derived from eight discrete data sets for major plant clades, and discusses their macroevolutionary implications. Most of the plant clades in this study show initial, high levels of disparity that approach or attain the maximum levels reached subsequently. These plant clades are characterized by an initial phase of evolution during which most regions of their empirical morphospaces are colonized. Angiosperms, palms, pines and ferns show remarkably little variation in disparity through time. Conifers furnish the most marked exception, appearing at relatively low disparity in the latest Carboniferous, before expanding incrementally with the radiation of successive, tightly clustered constituent sub-clades. Many cladistic data sets can be repurposed for investigating the morphological disparity of plant clades through time, and offer insights that are complementary to more focused morphometric studies. The unique structural and ecological features of plants make them ideally suited to investigating intrinsic and extrinsic constraints on disparity. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Identifying hidden rate changes in the evolution of a binary morphological character: the evolution of plant habit in campanulid angiosperms.

PubMed

Beaulieu, Jeremy M; O'Meara, Brian C; Donoghue, Michael J

2013-09-01

The growth of phylogenetic trees in scope and in size is promising from the standpoint of understanding a wide variety of evolutionary patterns and processes. With trees comprised of larger, older, and globally distributed clades, it is likely that the lability of a binary character will differ significantly among lineages, which could lead to errors in estimating transition rates and the associated inference of ancestral states. Here we develop and implement a new method for identifying different rates of evolution in a binary character along different branches of a phylogeny. We illustrate this approach by exploring the evolution of growth habit in Campanulidae, a flowering plant clade containing some 35,000 species. The distribution of woody versus herbaceous species calls into question the use of traditional models of binary character evolution. The recognition and accommodation of changes in the rate of growth form evolution in different lineages demonstrates, for the first time, a robust picture of growth form evolution across a very large, very old, and very widespread flowering plant clade.

Seed tissue and nutrient partitioning, a case for the nucellus.

PubMed

Lu, Jing; Magnani, Enrico

2018-06-05

Flowering plants display a large spectrum of seed architectures. The volume ratio of maternal versus zygotic seed tissues changes considerably among species and underlies different nutrient-storing strategies. Such diversity arose through the evolution of cell elimination programs that regulate the relative growth of one tissue over another to become the major storage compartment. The elimination of the nucellus maternal tissue is regulated by developmental programs that marked the origin of angiosperms and outlined the most ancient seed architectures. This review focuses on such a defining mechanism for seed evolution and discusses the role of nucellus development in seed tissues and nutrient partitioning at the light of novel discoveries on its molecular regulation.

Single-Copy Nuclear Genes Place Haustorial Hydnoraceae within Piperales and Reveal a Cretaceous Origin of Multiple Parasitic Angiosperm Lineages

PubMed Central

Naumann, Julia; Salomo, Karsten; Der, Joshua P.; Wafula, Eric K.; Bolin, Jay F.; Maass, Erika; Frenzke, Lena; Samain, Marie-Stéphanie; Neinhuis, Christoph

2013-01-01

Extreme haustorial parasites have long captured the interest of naturalists and scientists with their greatly reduced and highly specialized morphology. Along with the reduction or loss of photosynthesis, the plastid genome often decays as photosynthetic genes are released from selective constraint. This makes it challenging to use traditional plastid genes for parasitic plant phylogenetics, and has driven the search for alternative phylogenetic and molecular evolutionary markers. Thus, evolutionary studies, such as molecular clock-based age estimates, are not yet available for all parasitic lineages. In the present study, we extracted 14 nuclear single copy genes (nSCG) from Illumina transcriptome data from one of the “strangest plants in the world”, Hydnora visseri (Hydnoraceae). A ∼15,000 character molecular dataset, based on all three genomic compartments, shows the utility of nSCG for reconstructing phylogenetic relationships in parasitic lineages. A relaxed molecular clock approach with the same multi-locus dataset, revealed an ancient age of ∼91 MYA for Hydnoraceae. We then estimated the stem ages of all independently originated parasitic angiosperm lineages using a published dataset, which also revealed a Cretaceous origin for Balanophoraceae, Cynomoriaceae and Apodanthaceae. With the exception of Santalales, older parasite lineages tend to be more specialized with respect to trophic level and have lower species diversity. We thus propose the “temporal specialization hypothesis” (TSH) implementing multiple independent specialization processes over time during parasitic angiosperm evolution. PMID:24265760

Reduce, reuse, and recycle: developmental evolution of trait diversification.

PubMed

Preston, Jill C; Hileman, Lena C; Cubas, Pilar

2011-03-01

A major focus of evolutionary developmental (evo-devo) studies is to determine the genetic basis of variation in organismal form and function, both of which are fundamental to biological diversification. Pioneering work on metazoan and flowering plant systems has revealed conserved sets of genes that underlie the bauplan of organisms derived from a common ancestor. However, the extent to which variation in the developmental genetic toolkit mirrors variation at the phenotypic level is an active area of research. Here we explore evidence from the angiosperm evo-devo literature supporting the frugal use of genes and genetic pathways in the evolution of developmental patterning. In particular, these examples highlight the importance of genetic pleiotropy in different developmental modules, thus reducing the number of genes required in growth and development, and the reuse of particular genes in the parallel evolution of ecologically important traits.

The evolution of floral sonication, a pollen foraging behavior used by bees (Anthophila)

PubMed Central

Cardinal, Sophie; Buchmann, Stephen L.; Russell, Avery L.

2018-01-01

Abstract Over 22,000 species of biotically pollinated flowering plants, including some major agricultural crops, depend primarily on bees capable of floral sonication for pollination services. The ability to sonicate (“buzz”) flowers is widespread in bees but not ubiquitous. Despite the prevalence of this pollinator behavior and its importance to natural and agricultural systems, the evolutionary history of floral sonication in bees has not been previously studied. Here, we reconstruct the evolutionary history of floral sonication in bees by generating a time‐calibrated phylogeny and reconstructing ancestral states for this pollen extraction behavior. We also test the hypothesis that the ability to sonicate flowers and thereby efficiently access pollen from a diverse assemblage of plant species, led to increased diversification among sonicating bee taxa. We find that floral sonication evolved on average 45 times within bees, possibly first during the Early Cretaceous (100–145 million years ago) in the common ancestor of bees. We find that sonicating lineages are significantly more species rich than nonsonicating sister lineages when comparing sister clades, but a probabilistic structured rate permutation on phylogenies approach failed to support the hypothesis that floral sonication is a key driver of bee diversification. This study provides the evolutionary framework needed to further study how floral sonication by bees may have facilitated the spread and common evolution of angiosperm species with poricidal floral morphology. PMID:29392714

Speciation genes in the genus Petunia

PubMed Central

Venail, Julien; Dell'Olivo, Alexandre; Kuhlemeier, Cris

2010-01-01

A major innovation in angiosperms is the recruitment of animal pollinators as a means to enhance the efficiency and specificity of pollen transfer. The implementation of this reproductive strategy involved the rapid and presumably coordinated evolution of multiple floral traits. A major question concerns the molecular identity of the genetic polymorphisms that specify the phenotypic differences between distinct pollination syndromes. Here, we report on our work with Petunia, an attractive model system for quantitative plant genetics and genomics. From interspecific crosses, we obtained F2 plants that differed in the length of the floral tube or the size of the limb. We used these plants to study the behaviour of the hawkmoth pollinator, Manduca sexta. Plants with larger limbs were preferentially visited, consistent with the notion that flower size affects visibility under low light conditions. The moths also displayed an innate preference for shorter tubes. However, in those cases that flowers with long tubes were chosen, the animals fed for equal time. Thus, the perception of tube length may help the moths, early on, to avoid those plants that are more difficult to handle. PMID:20047872

The resurrection genome of Boea hygrometrica: A blueprint for survival of dehydration.

PubMed

Xiao, Lihong; Yang, Ge; Zhang, Liechi; Yang, Xinhua; Zhao, Shuang; Ji, Zhongzhong; Zhou, Qing; Hu, Min; Wang, Yu; Chen, Ming; Xu, Yu; Jin, Haijing; Xiao, Xuan; Hu, Guipeng; Bao, Fang; Hu, Yong; Wan, Ping; Li, Legong; Deng, Xin; Kuang, Tingyun; Xiang, Chengbin; Zhu, Jian-Kang; Oliver, Melvin J; He, Yikun

2015-05-05

"Drying without dying" is an essential trait in land plant evolution. Unraveling how a unique group of angiosperms, the Resurrection Plants, survive desiccation of their leaves and roots has been hampered by the lack of a foundational genome perspective. Here we report the ∼1,691-Mb sequenced genome of Boea hygrometrica, an important resurrection plant model. The sequence revealed evidence for two historical genome-wide duplication events, a compliment of 49,374 protein-coding genes, 29.15% of which are unique (orphan) to Boea and 20% of which (9,888) significantly respond to desiccation at the transcript level. Expansion of early light-inducible protein (ELIP) and 5S rRNA genes highlights the importance of the protection of the photosynthetic apparatus during drying and the rapid resumption of protein synthesis in the resurrection capability of Boea. Transcriptome analysis reveals extensive alternative splicing of transcripts and a focus on cellular protection strategies. The lack of desiccation tolerance-specific genome organizational features suggests the resurrection phenotype evolved mainly by an alteration in the control of dehydration response genes.

Resolution of Brassicaceae Phylogeny Using Nuclear Genes Uncovers Nested Radiations and Supports Convergent Morphological Evolution

PubMed Central

Huang, Chien-Hsun; Sun, Renran; Hu, Yi; Zeng, Liping; Zhang, Ning; Cai, Liming; Zhang, Qiang; Koch, Marcus A.; Al-Shehbaz, Ihsan; Edger, Patrick P.; Pires, J. Chris; Tan, Dun-Yan; Zhong, Yang; Ma, Hong

2016-01-01

Brassicaceae is one of the most diverse and economically valuable angiosperm families with widely cultivated vegetable crops and scientifically important model plants, such as Arabidopsis thaliana. The evolutionary history, ecological, morphological, and genetic diversity, and abundant resources and knowledge of Brassicaceae make it an excellent model family for evolutionary studies. Recent phylogenetic analyses of the family revealed three major lineages (I, II, and III), but relationships among and within these lineages remain largely unclear. Here, we present a highly supported phylogeny with six major clades using nuclear markers from newly sequenced transcriptomes of 32 Brassicaceae species and large data sets from additional taxa for a total of 55 species spanning 29 out of 51 tribes. Clade A consisting of Lineage I and Macropodium nivale is sister to combined Clade B (with Lineage II and others) and a new Clade C. The ABC clade is sister to Clade D with species previously weakly associated with Lineage II and Clade E (Lineage III) is sister to the ABCD clade. Clade F (the tribe Aethionemeae) is sister to the remainder of the entire family. Molecular clock estimation reveals an early radiation of major clades near or shortly after the Eocene–Oligocene boundary and subsequent nested divergences of several tribes of the previously polytomous Expanded Lineage II. Reconstruction of ancestral morphological states during the Brassicaceae evolution indicates prevalent parallel (convergent) evolution of several traits over deep times across the entire family. These results form a foundation for future evolutionary analyses of structures and functions across Brassicaceae. PMID:26516094

Valine-glutamine (VQ) motif coding genes are ancient and non-plant-specific with comprehensive expression regulation by various biotic and abiotic stresses.

PubMed

Jiang, Shu-Ye; Sevugan, Mayalagu; Ramachandran, Srinivasan

2018-05-09

Valine-glutamine (VQ) motif containing proteins play important roles in abiotic and biotic stress responses in plants. However, little is known about the origin and evolution as well as comprehensive expression regulation of the VQ gene family. In this study, we systematically surveyed this gene family in 50 plant genomes from algae, moss, gymnosperm and angiosperm and explored their presence in other species from animals, bacteria, fungi and viruses. No VQs were detected in all tested algae genomes and all genomes from moss, gymnosperm and angiosperm encode varying numbers of VQs. Interestingly, some of fungi, lower animals and bacteria also encode single to a few VQs. Thus, they are not plant-specific and should be regarded as an ancient family. Their family expansion was mainly due to segmental duplication followed by tandem duplication and mobile elements. Limited contribution of gene conversion was detected to the family evolution. Generally, VQs were very much conserved in their motif coding region and were under purifying selection. However, positive selection was also observed during species divergence. Many VQs were up- or down-regulated by various abiotic / biotic stresses and phytohormones in rice and Arabidopsis. They were also co-expressed with some of other stress-related genes. All of the expression data suggest a comprehensive expression regulation of the VQ gene family. We provide new insights into gene expansion, divergence, evolution and their expression regulation of this VQ family. VQs were detectable not only in plants but also in some of fungi, lower animals and bacteria, suggesting the evolutionary conservation and the ancient origin. Overall, VQs are non-plant-specific and play roles in abiotic / biotic responses or other biological processes through comprehensive expression regulation.

The Paleocene Eocene carbon isotope excursion in higher plant organic matter: Differential fractionation of angiosperms and conifers in the Arctic

NASA Astrophysics Data System (ADS)

Schouten, Stefan; Woltering, Martijn; Rijpstra, W. Irene C.; Sluijs, Appy; Brinkhuis, Henk; Sinninghe Damsté, Jaap S.

2007-06-01

A study of upper Paleocene-lower Eocene (P-E) sediments deposited on the Lomonosov Ridge in the central Arctic Ocean reveals relatively high abundances of terrestrial biomarkers. These include dehydroabietane and simonellite derived from conifers (gymnosperms) and a tetra-aromatic triterpenoid derived from angiosperms. The relative percentage of the angiosperm biomarker of the summed angiosperm + conifer biomarkers was increased at the end of the Paleocene-Eocene thermal maximum (PETM), different when observed with pollen counts which showed a relative decrease in angiosperm pollen. Stable carbon isotopic analysis of these biomarkers shows that the negative carbon isotope excursion (CIE) during the PETM amounts to 3‰ for both conifer biomarkers, dehydroabietane and simonellite, comparable to the magnitude of the CIE inferred from marine carbonates, but significantly lower than the 4.5‰ of the terrestrial C 29n-alkane [M. Pagani, N. Pedentchouk, M. Huber, A. Sluijs, S. Schouten, H. Brinkhuis, J.S. Sinninghe Damsté, G.R. Dickens, and the IODP Expedition 302 Expedition Scientists (2006), Arctic's hydrology during global warming at the Paleocene-Eocene thermal maximum. Nature, 442, 671-675.], which is a compound sourced by both conifers and angiosperms. Conspicuously, the angiosperm-sourced aromatic triterpane shows a much larger CIE of 6‰ and suggests that angiosperms increased in their carbon isotopic fractionation during the PETM. Our results thus indicate that the 4.5‰ C 29n-alkane CIE reported previously represents the average CIE of conifers and angiosperms at this site and suggest that the large and variable CIE observed in terrestrial records may be partly explained by the variable contributions of conifers and angiosperms. The differential response in isotopic fractionation of angiosperms and conifers points to different physiological responses of these vegetation types to the rise in temperature, humidity, and greenhouse gases during the PETM.

The evolution, morphology, and development of fern leaves

PubMed Central

Vasco, Alejandra; Moran, Robbin C.; Ambrose, Barbara A.

2013-01-01

Leaves are lateral determinate structures formed in a predictable sequence (phyllotaxy) on the flanks of an indeterminate shoot apical meristem. The origin and evolution of leaves in vascular plants has been widely debated. Being the main conspicuous organ of nearly all vascular plants and often easy to recognize as such, it seems surprising that leaves have had multiple origins. For decades, morphologists, anatomists, paleobotanists, and systematists have contributed data to this debate. More recently, molecular genetic studies have provided insight into leaf evolution and development mainly within angiosperms and, to a lesser extent, lycophytes. There has been recent interest in extending leaf evolutionary developmental studies to other species and lineages, particularly in lycophytes and ferns. Therefore, a review of fern leaf morphology, evolution and development is timely. Here we discuss the theories of leaf evolution in ferns, morphology, and diversity of fern leaves, and experimental results of fern leaf development. We summarize what is known about the molecular genetics of fern leaf development and what future studies might tell us about the evolution of fern leaf development. PMID:24027574

The late Cretaceous Arman flora of Magadan oblast, Northeastern Russia

NASA Astrophysics Data System (ADS)

Herman, A. B.; Golovneva, L. B.; Shczepetov, S. V.; Grabovsky, A. A.

2016-12-01

The Arman flora from the volcanogenic-sedimentary beds of the Arman Formation is systematically studied using materials from the Arman River basin and the Nelkandya-Khasyn interfluve (Magadan oblast, Northeastern Russia). Seventy-three species of fossil plants belonging to 49 genera are described. They consist of liverworts, horsetails, ferns, seed ferns, cycadaleans, bennettitaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms of uncertain systematic affinity, and angiosperms. The Arman flora shows a unique combination, with relatively ancient Early Cretaceous ferns and gymnosperms occurring alongside younger Late Cretaceous plants, primarily angiosperms. The similarity of the Arman flora to the Penzhina and Kaivayam floras of northwestern Kamchatka and the Tylpegyrgynai flora of the Pekul'nei Ridge allows the Arman flora to be dated as Turonian and Coniacian (Late Cretaceous), which is corroborated by isotopic (U-Pb and 40Ar/39Ar) age determination for the plant-bearing layers.

Oil biosynthesis in a basal angiosperm: transcriptome analysis of Persea Americana mesocarp.

PubMed

Kilaru, Aruna; Cao, Xia; Dabbs, Parker B; Sung, Ha-Jung; Rahman, Md Mahbubur; Thrower, Nicholas; Zynda, Greg; Podicheti, Ram; Ibarra-Laclette, Enrique; Herrera-Estrella, Luis; Mockaitis, Keithanne; Ohlrogge, John B

2015-08-16

The mechanism by which plants synthesize and store high amounts of triacylglycerols (TAG) in tissues other than seeds is not well understood. The comprehension of controls for carbon partitioning and oil accumulation in nonseed tissues is essential to generate oil-rich biomass in perennial bioenergy crops. Persea americana (avocado), a basal angiosperm with unique features that are ancestral to most flowering plants, stores ~ 70 % TAG per dry weight in its mesocarp, a nonseed tissue. Transcriptome analyses of select pathways, from generation of pyruvate and leading up to TAG accumulation, in mesocarp tissues of avocado was conducted and compared with that of oil-rich monocot (oil palm) and dicot (rapeseed and castor) tissues to identify tissue- and species-specific regulation and biosynthesis of TAG in plants. RNA-Seq analyses of select lipid metabolic pathways of avocado mesocarp revealed patterns similar to that of other oil-rich species. However, only some predominant orthologs of the fatty acid biosynthetic pathway genes in this basal angiosperm were similar to those of monocots and dicots. The accumulation of TAG, rich in oleic acid, was associated with higher transcript levels for a putative stearoyl-ACP desaturase and endoplasmic reticulum (ER)-associated acyl-CoA synthetases, during fruit development. Gene expression levels for enzymes involved in terminal steps to TAG biosynthesis in the ER further indicated that both acyl-CoA-dependent and -independent mechanisms might play a role in TAG assembly, depending on the developmental stage of the fruit. Furthermore, in addition to the expression of an ortholog of WRINKLED1 (WRI1), a regulator of fatty acid biosynthesis, high transcript levels for WRI2-like and WRI3-like suggest a role for additional transcription factors in nonseed oil accumulation. Plastid pyruvate necessary for fatty acid synthesis is likely driven by the upregulation of genes involved in glycolysis and transport of its intermediates. Together, a comparative transcriptome analyses for storage oil biosynthesis in diverse plants and tissues suggested that several distinct and conserved features in this basal angiosperm species might contribute towards its rich TAG content. Our work represents a comprehensive transcriptome resource for a basal angiosperm species and provides insight into their lipid metabolism in mesocarp tissues. Furthermore, comparison of the transcriptome of oil-rich mesocarp of avocado, with oil-rich seed and nonseed tissues of monocot and dicot species, revealed lipid gene orthologs that are highly conserved during evolution. The orthologs that are distinctively expressed in oil-rich mesocarp tissues of this basal angiosperm, such as WRI2, ER-associated acyl-CoA synthetases, and lipid-droplet associated proteins were also identified. This study provides a foundation for future investigations to increase oil-content and has implications for metabolic engineering to enhance storage oil content in nonseed tissues of diverse species.

Embryological Features of Tofieldia glutinosa and Their Bearing on the Early Diversification of Monocotyledonous Plants

PubMed Central

Holloway, Samuel J.; Friedman, William E.

2008-01-01

Background and Aims Although much is known about the vegetative traits associated with early monocot evolution, less is known about the reproductive features of early monocotyledonous lineages. A study was made of the embryology of Tofieldia glutinosa, a member of an early divergent monocot clade (Tofieldiaceae), and aspects of its development were compared with the development of other early divergent monocots in order to gain insight into defining reproductive features of early monocots. Methods Field-collected developing gynoecial tissues of Tofieldia glutinosa were prepared for histological examination. Over 600 ovules were sectioned and studied using brightfield, differential interference contrast, and fluorescence microscopy. High-resolution digital imaging was used to document important stages of megasporogenesis, megagametogenesis and early endosperm development. Key Results Development of the female gametophyte in T. glutinosa is of a modified Polygonum-type. At maturity the female gametophyte is seven-celled and 11-nucleate with a standard three-celled egg apparatus, a binucleate central cell (where ultimately, the two polar nuclei will fuse into a diploid secondary nucleus) and three binucleate antipodal cells. The antipodal nuclei persist past fertilization, and the process of double fertilization appears to yield a diploid zygote and triploid primary endosperm cell, as is characteristic of plants with Polygonum-type female gametophytes. Endosperm development is helobial, and free-nuclear growth initially proceeds at equal rates in both the micropylar and chalazal endosperm chambers. Conclusions The analysis suggests that the shared common ancestor of monocots possessed persistent and proliferating antipodals similar to those found in T. glutinosa and other early-divergent monocots (e.g. Acorus and members of the Araceae). Helobial endosperm among monocots evolved once in the common ancestor of all monocots excluding Acorus. Thus, the analysis further suggests that helobial endosperm in monocots is homoplasious with those helobial endosperms that are present in water lilies and eudicot angiosperms. PMID:18511412

Comparative analysis of expressed sequence tags of conifers and angiosperms reveals sequences specifically conserved in conifers.

PubMed

Ujino-Ihara, Tokuko; Kanamori, Hiroyuki; Yamane, Hiroko; Taguchi, Yuriko; Namiki, Nobukazu; Mukai, Yuzuru; Yoshimura, Kensuke; Tsumura, Yoshihiko

2005-12-01

To identify and characterize lineage-specific genes of conifers, two sets of ESTs (with 12791 and 5902 ESTs, representing 5373 and 3018 gene transcripts, respectively) were generated from the Cupressaceae species Cryptomeria japonica and Chamaecyparis obtusa. These transcripts were compared with non-redundant sets of genes generated from Pinaceae species, other gymnosperms and angiosperms. About 6% of tentative unique genes (Unigenes) of C. japonica and C. obtusa had homologs in other conifers but not angiosperms, and about 70% had apparent homologs in angiosperms. The calculated GC contents of orthologous genes showed that GC contents of coniferous genes are likely to be lower than those of angiosperms. Comparisons of the numbers of homologous genes in each species suggest that copy numbers of genes may be correlated between diverse seed plants. This correlation suggests that the multiplicity of such genes may have arisen before the divergence of gymnosperms and angiosperms.

Evolutionary history of callose synthases in terrestrial plants with emphasis on proteins involved in male gametophyte development

PubMed Central

Honys, David

2017-01-01

Callose is a plant-specific polysaccharide (β-1,3-glucan) playing an important role in angiosperms in many developmental processes and responses to biotic and abiotic stresses. Callose is synthesised at the plasma membrane of plant cells by callose synthase (CalS) and, among others, represents the main polysaccharide in the callose wall surrounding the tetrads of developing microspores and in the growing pollen tube wall. CalS proteins involvement in spore development is a plesiomorphic feature of terrestrial plants, but very little is known about their evolutionary origin and relationships amongst the members of this protein family. We performed thorough comparative analyses of callose synthase family proteins from major plant lineages to determine their evolutionary history across the plant kingdom. A total of 1211 candidate CalS sequences were identified and compared amongst diverse taxonomic groups of plants, from bryophytes to angiosperms. Phylogenetic analyses identified six main clades of CalS proteins and suggested duplications during the evolution of specialised functions. Twelve family members had previously been identified in Arabidopsis thaliana. We focused on five CalS subfamilies directly linked to pollen function and found that proteins expressed in pollen evolved twice. CalS9/10 and CalS11/12 formed well-defined clades, whereas pollen-specific CalS5 was found within subfamilies that mostly did not express in mature pollen vegetative cell, although were found in sperm cells. Expression of five out of seven mature pollen-expressed CalS genes was affected by mutations in bzip transcription factors. Only three subfamilies, CalS5, CalS10, and CalS11, however, formed monophyletic, mostly conserved clades. The pairs CalS9/CalS10, CalS11/CalS12 and CalS3 may have diverged after angiosperms diversified from lycophytes and bryophytes. Our analysis of fully sequenced plant proteins identified new evolutionary lineages of callose synthase subfamilies and has established a basis for understanding their functional evolution in terrestrial plants. PMID:29131847

Phylogenetic reconstruction in the Order Nymphaeales: ITS2 secondary structure analysis and in silico testing of maturase k (matK) as a potential marker for DNA bar coding

PubMed Central

2012-01-01

Background The Nymphaeales (waterlilly and relatives) lineage has diverged as the second branch of basal angiosperms and comprises of two families: Cabombaceae and Nymphaceae. The classification of Nymphaeales and phylogeny within the flowering plants are quite intriguing as several systems (Thorne system, Dahlgren system, Cronquist system, Takhtajan system and APG III system (Angiosperm Phylogeny Group III system) have attempted to redefine the Nymphaeales taxonomy. There have been also fossil records consisting especially of seeds, pollen, stems, leaves and flowers as early as the lower Cretaceous. Here we present an in silico study of the order Nymphaeales taking maturaseK (matK) and internal transcribed spacer (ITS2) as biomarkers for phylogeny reconstruction (using character-based methods and Bayesian approach) and identification of motifs for DNA barcoding. Results The Maximum Likelihood (ML) and Bayesian approach yielded congruent fully resolved and well-supported trees using a concatenated (ITS2+ matK) supermatrix aligned dataset. The taxon sampling corroborates the monophyly of Cabombaceae. Nuphar emerges as a monophyletic clade in the family Nymphaeaceae while there are slight discrepancies in the monophyletic nature of the genera Nymphaea owing to Victoria-Euryale and Ondinea grouping in the same node of Nymphaeaceae. ITS2 secondary structures alignment corroborate the primary sequence analysis. Hydatellaceae emerged as a sister clade to Nymphaeaceae and had a basal lineage amongst the water lilly clades. Species from Cycas and Ginkgo were taken as outgroups and were rooted in the overall tree topology from various methods. Conclusions MatK genes are fast evolving highly variant regions of plant chloroplast DNA that can serve as potential biomarkers for DNA barcoding and also in generating primers for angiosperms with identification of unique motif regions. We have reported unique genus specific motif regions in the Order Nymphaeles from matK dataset which can be further validated for barcoding and designing of PCR primers. Our analysis using a novel approach of sequence-structure alignment and phylogenetic reconstruction using molecular morphometrics congrue with the current placement of Hydatellaceae within the early-divergent angiosperm order Nymphaeales. The results underscore the fact that more diverse genera, if not fully resolved to be monophyletic, should be represented by all major lineages. PMID:23282079

The influence of pleiotropy between viability and pollen fates on mating system evolution.

PubMed

Jordan, Crispin Y

2015-02-01

Floral displays are functionally and genetically integrated structures, so modifications to display will likely affect multiple fitness components (pleiotropy), including pollen export and self-pollination, and therefore selfing rate. Consequently, the great diversities of floral displays and of mating systems found among angiosperms have likely co-evolved. I extend previous models of mating system evolution to determine how pleiotropy that links viability (e.g., probability of survival to reproduction) and the allocation of pollen for export and selfing affects the evolution of selfing, outcrossing, and in particular, mixed mating. I show that the outcome depends on how pollen shifts from being exported, unused, or used for selfing. Furthermore, pleiotropy that affects viability can explain observations not addressed by previous theory, including the evolution of mixed mating despite high inbreeding depression in the absence of pollen-limitation. Therefore, pleiotropy may play a key role in explaining selfing rates for such species that exhibit otherwise enigmatic mating systems. Copyright © 2014 Elsevier Inc. All rights reserved.

Testing the impact of morphological rate heterogeneity on ancestral state reconstruction of five floral traits in angiosperms.

PubMed

Reyes, Elisabeth; Nadot, Sophie; von Balthazar, Maria; Schönenberger, Jürg; Sauquet, Hervé

2018-06-21

Ancestral state reconstruction is an important tool to study morphological evolution and often involves estimating transition rates among character states. However, various factors, including taxonomic scale and sampling density, may impact transition rate estimation and indirectly also the probability of the state at a given node. Here, we test the influence of rate heterogeneity using maximum likelihood methods on five binary perianth characters, optimized on a phylogenetic tree of angiosperms including 1230 species sampled from all families. We compare the states reconstructed by an equal-rate (Mk1) and a two-rate model (Mk2) fitted either with a single set of rates for the whole tree or as a partitioned model, allowing for different rates on five partitions of the tree. We find strong signal for rate heterogeneity among the five subdivisions for all five characters, but little overall impact of the choice of model on reconstructed ancestral states, which indicates that most of our inferred ancestral states are the same whether heterogeneity is accounted for or not.

Quantifying in situ phenotypic variability in the hydraulic properties of four tree species across their distribution range in Europe

PubMed Central

Sterck, F.; Torres-Ruiz, J. M.; Petit, G.; Cochard, H.; von Arx, G.; Lintunen, A.; Caldeira, M. C.; Capdeville, G.; Copini, P.; Gebauer, R.; Grönlund, L.; Hölttä, T.; Lobo-do-Vale, R.; Peltoniemi, M.; Stritih, A.; Urban, J.; Delzon, S.

2018-01-01

Many studies have reported that hydraulic properties vary considerably between tree species, but little is known about their intraspecific variation and, therefore, their capacity to adapt to a warmer and drier climate. Here, we quantify phenotypic divergence and clinal variation for embolism resistance, hydraulic conductivity and branch growth, in four tree species, two angiosperms (Betula pendula, Populus tremula) and two conifers (Picea abies, Pinus sylvestris), across their latitudinal distribution in Europe. Growth and hydraulic efficiency varied widely within species and between populations. The variability of embolism resistance was in general weaker than that of growth and hydraulic efficiency, and very low for all species but Populus tremula. In addition, no and weak support for a safety vs. efficiency trade-off was observed for the angiosperm and conifer species, respectively. The limited variability of embolism resistance observed here for all species except Populus tremula, suggests that forest populations will unlikely be able to adapt hydraulically to drier conditions through the evolution of embolism resistance. PMID:29715289

Geography, environment and organismal traits in the diversification of a major tropical herbaceous angiosperm radiation

PubMed Central

2018-01-01

Abstract The generation of plant diversity involves complex interactions between geography, environment and organismal traits. Many macroevolutionary processes and emergent patterns have been identified in different plant groups through the study of spatial data, but rarely in the context of a large radiation of tropical herbaceous angiosperms. A powerful system for testing interrelated biogeographical hypotheses is provided by the terrestrial bromeliads, a Neotropical group of extensive ecological diversity and importance. In this investigation, distributional data for 564 species of terrestrial bromeliads were used to estimate variation in the position and width of species-level hydrological habitat occupancy and test six core hypotheses linking geography, environment and organismal traits. Taxonomic groups and functional types differed in hydrological habitat occupancy, modulated by convergent and divergent trait evolution, and with contrasting interactions with precipitation abundance and seasonality. Plant traits in the Bromeliaceae are intimately associated with bioclimatic differentiation, which is in turn strongly associated with variation in geographical range size and species richness. These results emphasize the ecological relevance of structural-functional innovation in a major plant radiation. PMID:29479409

The chromosomal distribution of histone methylation marks in gymnosperms differs from that of angiosperms.

PubMed

Fuchs, Jörg; Jovtchev, Gabriele; Schubert, Ingo

2008-01-01

The chromosomal distribution of seven histone methylation marks (H3K4me2, H3K9me1,2,3 and H3K27me1,2,3) was analysed in the gymnosperm species Pinus sylvestris and Picea abies. Similarly to the situation in other investigated eukaryotes, dimethylation of lysine 4 of histone H3 is restricted to euchromatin in gymnosperms. Surprisingly, also H3K9me1-a mark classified as heterochromatin-specific in angiosperms-labels the euchromatin in P. sylvestris and P. abies. The other investigated methylation marks are either equally distributed along the chromosomes, as H3K9me2 and H3K27me1 (in both species) and H3K9me3 (in P. abies), or enriched at specific types of heterochromatin, as H3K9me3 (in P. sylvestris) and H3K27me2 and H3K27me3 in both species. Although the methylation marks themselves are apparently conserved, their functional specificity within the frame of the 'epigenetic code' might have diverged during evolution.

The evolution of bat pollination: a phylogenetic perspective

PubMed Central

Fleming, Theodore H.; Geiselman, Cullen; Kress, W. John

2009-01-01

Background Most tropical and subtropical plants are biotically pollinated, and insects are the major pollinators. A small but ecologically and economically important group of plants classified in 28 orders, 67 families and about 528 species of angiosperms are pollinated by nectar-feeding bats. From a phylogenetic perspective this is a derived pollination mode involving a relatively large and energetically expensive pollinator. Here its ecological and evolutionary consequences are explored. Scope and Conclusions This review summarizes adaptations in bats and plants that facilitate this interaction and discusses the evolution of bat pollination from a plant phylogenetic perspective. Two families of bats contain specialized flower visitors, one in the Old World and one in the New World. Adaptation to pollination by bats has evolved independently many times from a variety of ancestral conditions, including insect-, bird- and non-volant mammal-pollination. Bat pollination predominates in very few families but is relatively common in certain angiosperm subfamilies and tribes. We propose that flower-visiting bats provide two important benefits to plants: they deposit large amounts of pollen and a variety of pollen genotypes on plant stigmas and, compared with many other pollinators, they are long-distance pollen dispersers. Bat pollination tends to occur in plants that occur in low densities and in lineages producing large flowers. In highly fragmented tropical habitats, nectar bats play an important role in maintaining the genetic continuity of plant populations and thus have considerable conservation value. PMID:19789175

Revisiting the phosphatidylethanolamine-binding protein (PEBP) gene family reveals cryptic FLOWERING LOCUS T gene homologs in gymnosperms and sheds new light on functional evolution.

PubMed

Liu, Yan-Yan; Yang, Ke-Zhen; Wei, Xiao-Xin; Wang, Xiao-Quan

2016-11-01

Angiosperms and gymnosperms are two major groups of extant seed plants. It has been suggested that gymnosperms lack FLOWERING LOCUS T (FT), a key integrator at the core of flowering pathways in angiosperms. Taking advantage of newly released gymnosperm genomes, we revisited the evolutionary history of the plant phosphatidylethanolamine-binding protein (PEBP) gene family through phylogenetic reconstruction. Expression patterns in three gymnosperm taxa and heterologous expression in Arabidopsis were studied to investigate the functions of gymnosperm FT-like and TERMINAL FLOWER 1 (TFL1)-like genes. Phylogenetic reconstruction suggests that an ancient gene duplication predating the divergence of seed plants gave rise to the FT and TFL1 genes. Expression patterns indicate that gymnosperm TFL1-like genes play a role in the reproductive development process, while GymFT1 and GymFT2, the FT-like genes resulting from a duplication event in the common ancestor of gymnosperms, function in both growth rhythm and sexual development pathways. When expressed in Arabidopsis, both spruce FT-like and TFL1-like genes repressed flowering. Our study demonstrates that gymnosperms do have FT-like and TFL1-like genes. Frequent gene and genome duplications contributed significantly to the expansion of the plant PEBP gene family. The expression patterns of gymnosperm PEBP genes provide novel insight into the functional evolution of this gene family. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

The Ty1-copia LTR retroelement family PARTC is highly conserved in conifers over 200 MY of evolution.

PubMed

Zuccolo, Andrea; Scofield, Douglas G; De Paoli, Emanuele; Morgante, Michele

2015-08-15

Long Terminal Repeat retroelements (LTR-RTs) are a major component of many plant genomes. Although well studied and described in angiosperms, their features and dynamics are poorly understood in gymnosperms. Representative complete copies of a Ty1-copia element isolate in Picea abies and named PARTC were identified in six other conifer species (Picea glauca, Pinus sylvestris, Pinus taeda, Abies sibirica, Taxus baccata and Juniperus communis) covering more than 200 million years of evolution. Here we characterized the structure of this element, assessed its abundance across conifers, studied the modes and timing of its amplification, and evaluated the degree of conservation of its extant copies at nucleotide level over distant species. We demonstrated that the element is ancient, abundant, widespread and its paralogous copies are present in the genera Picea, Pinus and Abies as an LTR-RT family. The amplification leading to the extant copies of PARTC occurred over long evolutionary times spanning 10s of MY and mostly took place after the speciation of the conifers analyzed. The level of conservation of PARTC is striking and may be explained by low substitution rates and limited removal mechanisms for LTR-RTs. These PARTC features and dynamics are representative of a more general scenario for LTR-RTs in gymnosperms quite different from that characterizing the vast majority of LTR-RT elements in angiosperms. Copyright © 2015 Elsevier B.V. All rights reserved.

[Morphological and molecular data on the origin of angiosperms: on a way to a synthesis].

PubMed

Sokolov, D D; Timonin, A K

2007-01-01

Molecular phylogenetic data have drastically changed the views on the phylogeny of higher plants. All the extant gymnosperms were asserted as a monophyletic group opposed to the highly isolated angiosperms. The 'Anthophyte Theory' was thus rejected. The identification and analysis of gymnosperm orthologues of genes regulating flower development in angiosperms resulted in the formulation of the 'Mostly Male Theory' of the evolutionary origin of flower; this theory does not contradict the concept of monophyly of all the extant gymnosperms. The Mostly Male Theory assumes that the origin of angiosperms was caused by a loss of the Needle family gene that effected ovuliferous (female) organs and the translocation of the ovules onto the adaxial side of some of the (male) leafy microsporangiophores. Having acquired ovules, the former microsporangiophores started evolving into the carpels. The prerequisite bisexual design of the ancestral fructification thus becomes unnecessary. Indeed, this assumption suggests the deriving of Angiosperms from any gymnosperm plant with leafy microsporangiophores. The problem of carpel origin has subsequently changed to some degree into the problem of the origin of the bitegmic anatropous ovule presumably inherent in ancestral Angiosperms. The Mostly Male Theory consideredeither Corystospermataceae (= Umkomasiaceae) or Caytoniaceae to be the forerunners of such an ovule. Yet the capsules of Corystospermataceae distinctly differ from angiosperm ovules in the locations of their adaxial/abaxial sides, while Caytoniaceae had no leafy microsporangiophores. This inconsistency suggests that functions of the Needle family regulatory genes in Gymnosperms should be much better understood to appraise properly both the possibilities and the consequences of their hypothetical loss by the emerging angiosperms. Moreover, the extant gymnosperm groups are actually held as monophyletic and contrasted to Angiosperms on the basis of analysing the unrepresentative scant remnants of these, mostly extinct, taxa. Therefore, traditional botanical and paleobotanical data should not be rejected. In any case, Meyen's idea angiosperms origin from Bennettitales is worth being retained as a hypothesis to be tested with new results of both paleobotany and molecular biology.

Ferns are less dependent on passive dilution by cell expansion to coordinate leaf vein and stomatal spacing than angiosperms

PubMed Central

Jordan, Gregory J.; Brodribb, Timothy J.

2017-01-01

Producing leaves with closely spaced veins is a key innovation linked to high rates of photosynthesis in angiosperms. A close geometric link between veins and stomata in angiosperms ensures that investment in enhanced venous water transport provides the strongest net carbon return to the plant. This link is underpinned by “passive dilution” via expansion of surrounding cells. However, it is not known whether this ‘passive dilution’ mechanism is present in plant lineages other than angiosperms and is another key feature of the angiosperms’ evolutionary success. Consequently, we sought to determine whether the ‘passive dilution’ mechanism is; (i) exclusive to the angiosperms, (ii) a conserved mechanism that evolved in the common ancestor of ferns and angiosperms, or (iii) has evolved continuously over time. To do this we first we assessed the plasticity of vein and stomatal density and epidermal cell size in ferns in response to light environment. We then compared the relationships between these traits found among ferns with modelled relationships that assume vein and stomatal density respond passively to epidermal cell expansion, and with those previously observed in angiosperms. Vein density, stomatal density and epidermal cell size were linked in ferns with remarkably similar relationships to those observed in angiosperms, except that fern leaves had fewer veins per stomata. However, plasticity was limited in ferns and stomatal spacing was dependent on active stomatal differentiation as well as passive cell expansion. Thus, ferns (like angiosperms) appear to coordinate vein and stomatal density with epidermal cell expansion to some extent to maintain a constant ratio between veins and stomata in the leaf. The different general relationships between vein density and stomatal density in ferns and angiosperms suggests the groups have different optimum balances between the production of vein tissue dedicated to water supply and stomatal tissue for gas exchange. PMID:28953931

Characterization and systematic implications of the diversity in timing of programmed cell death of the suspensors in Leguminosae.

PubMed

Endo, Yasuhiko

2012-08-01

In angiosperm seeds, the developing embryo acquires nutrients via a suspensor that typically undergoes programmed cell death (PCD) at the early cotyledon stage. However, in Leguminosae (the third largest angiosperm family), the suspensors can disappear at the heart-shaped stage (i.e., prior to the cotyledon stage) or still persist at the cotyledon stage. Here, in a comprehensive survey of legume suspensors and embryos, the variation and the evolutionary direction of timing of suspensor PCD in Leguminosae were characterized, and systematic implications were evaluated. Suspensor development and morphology for 66 leguminous species from 49 genera, 21 tribes, and 3 subfamilies were comparatively studied using standard paraffin sectioning and light microscopy. Three patterns of suspensor PCD were observed at the early cotyledon stage. (A) The suspensor persisted. (B) The suspensor separated from the wall of the embryo sac and persisted as a vestige at the radicle apex. (C) The suspensor disappeared completely, and the absorption of nutrients by embryo was carried out via a "contact zone" between the embryo and the endosperm. Pattern C of early suspensor PCD was found only in the tribe Fabeae. An ancestral character reconstruction revealed that the long-lived suspensors of pattern A represented a plesiomorphic condition in Leguminosae and that the suspensors of pattern C evolved only once in the common ancestor of Fabeae. In Leguminosae, short-lived suspensors have thus evolved multiple times from long-lived suspensors. It remains largely unknown, however, how the embryo acquires nutrients after the early suspensor PCD.

Arman' Flora of the magadan region and development of floras in the North Pacific during the Albian-Paleocene

NASA Astrophysics Data System (ADS)

Herman, A. B.

2011-02-01

The Arman' Flora from volcanogenic-sedimentary deposits in the Arman' River basin and Naraula Formation in the Nel'kandzha-Khasyn interfluve includes 82 species of fossil plants comprising liverworts, horsetails, ferns, caytonealeans, cycadaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms incertae sedis, and angiosperms. The Arman' Flora appears to be of Turonian-Coniacian age, as it is close to the reliably dated Penzhina and Kaivayam floras from the Northwest Kamchatka and to Tyl'pegyrgynai Flora of the Pekul'nei Ridge. The dating is consistent with isotopic dates (40Ar/39Ar and U-Pb SHRIMP) characterizing the age of plant-bearing sequences. Based on the considered position of the Arman' Flora in the scheme of Cretaceous florogenesis, a leading role in that florogenesis was played by the gradual invasion of floras by new, angiosperm dominated, plant communities. These communities initially populated unstable habitats in the coastal lowlands of Northeast Asia and Alaska, gradually invading with time the Asiatic intracontinental areas. The peculiar combination of Early and Late Cretaceous plants characteristic of the Arman' Flora is strong evidence that Cenophytic plant communities dominated by angiosperms colonized areas still populated in the Late Cretaceous by Mesophytic communities. Absence of Mesophytic and Cenophytic taxa mixing in the Arman' Flora burials suggests a replacement of plant communities as whole rather than of separate plants by more advanced taxa.

Comparative Genomics of NAC Transcriptional Factors in Angiosperms: Implications for the Adaptation and Diversification of Flowering Plants

PubMed Central

Pereira-Santana, Alejandro; Alcaraz, Luis David; Castaño, Enrique; Sanchez-Calderon, Lenin; Sanchez-Teyer, Felipe; Rodriguez-Zapata, Luis

2015-01-01

NAC proteins constitute one of the largest groups of plant-specific transcription factors and are known to play essential roles in various developmental processes. They are also important in plant responses to stresses such as drought, soil salinity, cold, and heat, which adversely affect growth. The current knowledge regarding the distribution of NAC proteins in plant lineages comes from relatively small samplings from the available data. In the present study, we broadened the number of plant species containing the NAC family origin and evolution to shed new light on the evolutionary history of this family in angiosperms. A comparative genome analysis was performed on 24 land plant species, and NAC ortholog groups were identified by means of bidirectional BLAST hits. Large NAC gene families are found in those species that have experienced more whole-genome duplication events, pointing to an expansion of the NAC family with divergent functions in flowering plants. A total of 3,187 NAC transcription factors that clustered into six major groups were used in the phylogenetic analysis. Many orthologous groups were found in the monocot and eudicot lineages, but only five orthologous groups were found between P. patens and each representative taxa of flowering plants. These groups were called basal orthologous groups and likely expanded into more recent taxa to cope with their environmental needs. This analysis on the angiosperm NAC family represents an effort to grasp the evolutionary and functional diversity within this gene family while providing a basis for further functional research on vascular plant gene families. PMID:26569117

Comparative Genomics of NAC Transcriptional Factors in Angiosperms: Implications for the Adaptation and Diversification of Flowering Plants.

PubMed

Pereira-Santana, Alejandro; Alcaraz, Luis David; Castaño, Enrique; Sanchez-Calderon, Lenin; Sanchez-Teyer, Felipe; Rodriguez-Zapata, Luis

2015-01-01

NAC proteins constitute one of the largest groups of plant-specific transcription factors and are known to play essential roles in various developmental processes. They are also important in plant responses to stresses such as drought, soil salinity, cold, and heat, which adversely affect growth. The current knowledge regarding the distribution of NAC proteins in plant lineages comes from relatively small samplings from the available data. In the present study, we broadened the number of plant species containing the NAC family origin and evolution to shed new light on the evolutionary history of this family in angiosperms. A comparative genome analysis was performed on 24 land plant species, and NAC ortholog groups were identified by means of bidirectional BLAST hits. Large NAC gene families are found in those species that have experienced more whole-genome duplication events, pointing to an expansion of the NAC family with divergent functions in flowering plants. A total of 3,187 NAC transcription factors that clustered into six major groups were used in the phylogenetic analysis. Many orthologous groups were found in the monocot and eudicot lineages, but only five orthologous groups were found between P. patens and each representative taxa of flowering plants. These groups were called basal orthologous groups and likely expanded into more recent taxa to cope with their environmental needs. This analysis on the angiosperm NAC family represents an effort to grasp the evolutionary and functional diversity within this gene family while providing a basis for further functional research on vascular plant gene families.

Contrasting trait syndromes in angiosperms and conifers are associated with different responses of tree growth to temperature on a large scale.

PubMed

Carnicer, Jofre; Barbeta, Adrià; Sperlich, Dominik; Coll, Marta; Peñuelas, Josep

2013-01-01

Recent large-scale studies of tree growth in the Iberian Peninsula reported contrasting positive and negative effects of temperature in Mediterranean angiosperms and conifers. Here we review the different hypotheses that may explain these trends and propose that the observed contrasting responses of tree growth to temperature in this region could be associated with a continuum of trait differences between angiosperms and conifers. Angiosperm and conifer trees differ in the effects of phenology in their productivity, in their growth allometry, and in their sensitivity to competition. Moreover, angiosperms and conifers significantly differ in hydraulic safety margins, sensitivity of stomatal conductance to vapor-pressure deficit (VPD), xylem recovery capacity or the rate of carbon transfer. These differences could be explained by key features of the xylem such as non-structural carbohydrate content (NSC), wood parenchymal fraction or wood capacitance. We suggest that the reviewed trait differences define two contrasting ecophysiological strategies that may determine qualitatively different growth responses to increased temperature and drought. Improved reciprocal common garden experiments along altitudinal or latitudinal gradients would be key to quantify the relative importance of the different hypotheses reviewed. Finally, we show that warming impacts in this area occur in an ecological context characterized by the advance of forest succession and increased dominance of angiosperm trees over extensive areas. In this context, we examined the empirical relationships between the responses of tree growth to temperature and hydraulic safety margins in angiosperm and coniferous trees. Our findings suggest a future scenario in Mediterranean forests characterized by contrasting demographic responses in conifer and angiosperm trees to both temperature and forest succession, with increased dominance of angiosperm trees, and particularly negative impacts in pines.

Contrasting trait syndromes in angiosperms and conifers are associated with different responses of tree growth to temperature on a large scale

PubMed Central

Carnicer, Jofre; Barbeta, Adrià; Sperlich, Dominik; Coll, Marta; Peñuelas, Josep

2013-01-01

Recent large-scale studies of tree growth in the Iberian Peninsula reported contrasting positive and negative effects of temperature in Mediterranean angiosperms and conifers. Here we review the different hypotheses that may explain these trends and propose that the observed contrasting responses of tree growth to temperature in this region could be associated with a continuum of trait differences between angiosperms and conifers. Angiosperm and conifer trees differ in the effects of phenology in their productivity, in their growth allometry, and in their sensitivity to competition. Moreover, angiosperms and conifers significantly differ in hydraulic safety margins, sensitivity of stomatal conductance to vapor-pressure deficit (VPD), xylem recovery capacity or the rate of carbon transfer. These differences could be explained by key features of the xylem such as non-structural carbohydrate content (NSC), wood parenchymal fraction or wood capacitance. We suggest that the reviewed trait differences define two contrasting ecophysiological strategies that may determine qualitatively different growth responses to increased temperature and drought. Improved reciprocal common garden experiments along altitudinal or latitudinal gradients would be key to quantify the relative importance of the different hypotheses reviewed. Finally, we show that warming impacts in this area occur in an ecological context characterized by the advance of forest succession and increased dominance of angiosperm trees over extensive areas. In this context, we examined the empirical relationships between the responses of tree growth to temperature and hydraulic safety margins in angiosperm and coniferous trees. Our findings suggest a future scenario in Mediterranean forests characterized by contrasting demographic responses in conifer and angiosperm trees to both temperature and forest succession, with increased dominance of angiosperm trees, and particularly negative impacts in pines. PMID:24146668

Testing the recent theories for the origin of the hermaphrodite flower by comparison of the transcriptomes of gymnosperms and angiosperms.

PubMed

Tavares, Raquel; Cagnon, Mathilde; Negrutiu, Ioan; Mouchiroud, Dominque

2010-08-03

Different theories for the origin of the angiosperm hermaphrodite flower make different predictions concerning the overlap between the genes expressed in the male and female cones of gymnosperms and the genes expressed in the hermaphrodite flower of angiosperms. The Mostly Male (MM) theory predicts that, of genes expressed primarily in male versus female gymnosperm cones, an excess of male orthologs will be expressed in flowers, excluding ovules, while Out Of Male (OOM) and Out Of Female (OOF) theories predict no such excess. In this paper, we tested these predictions by comparing the transcriptomes of three gymnosperms (Ginkgo biloba, Welwitschia mirabilis and Zamia fisheri) and two angiosperms (Arabidopsis thaliana and Oryza sativa), using EST data. We found that the proportion of orthologous genes expressed in the reproductive organs of the gymnosperms and in the angiosperms flower is significantly higher than the proportion of orthologous genes expressed in the reproductive organs of the gymnosperms and in the angiosperms vegetative tissues, which shows that the approach is correct. However, we detected no significant differences between the proportion of gymnosperm orthologous genes expressed in the male cone and in the angiosperms flower and the proportion of gymnosperm orthologous genes expressed in the female cone and in the angiosperms flower. These results do not support the MM theory prediction of an excess of male gymnosperm genes expressed in the hermaphrodite flower of the angiosperms and seem to support the OOM/OOF theories. However, other explanations can be given for the 1:1 ratio that we found. More abundant and more specific (namely carpel and ovule) expression data should be produced in order to further test these theories.

Testing the recent theories for the origin of the hermaphrodite flower by comparison of the transcriptomes of gymnosperms and angiosperms

PubMed Central

2010-01-01

Background Different theories for the origin of the angiosperm hermaphrodite flower make different predictions concerning the overlap between the genes expressed in the male and female cones of gymnosperms and the genes expressed in the hermaphrodite flower of angiosperms. The Mostly Male (MM) theory predicts that, of genes expressed primarily in male versus female gymnosperm cones, an excess of male orthologs will be expressed in flowers, excluding ovules, while Out Of Male (OOM) and Out Of Female (OOF) theories predict no such excess. Results In this paper, we tested these predictions by comparing the transcriptomes of three gymnosperms (Ginkgo biloba, Welwitschia mirabilis and Zamia fisheri) and two angiosperms (Arabidopsis thaliana and Oryza sativa), using EST data. We found that the proportion of orthologous genes expressed in the reproductive organs of the gymnosperms and in the angiosperms flower is significantly higher than the proportion of orthologous genes expressed in the reproductive organs of the gymnosperms and in the angiosperms vegetative tissues, which shows that the approach is correct. However, we detected no significant differences between the proportion of gymnosperm orthologous genes expressed in the male cone and in the angiosperms flower and the proportion of gymnosperm orthologous genes expressed in the female cone and in the angiosperms flower. Conclusions These results do not support the MM theory prediction of an excess of male gymnosperm genes expressed in the hermaphrodite flower of the angiosperms and seem to support the OOM/OOF theories. However, other explanations can be given for the 1:1 ratio that we found. More abundant and more specific (namely carpel and ovule) expression data should be produced in order to further test these theories. PMID:20682074

The phylogenetic distribution of extrafloral nectaries in plants.

PubMed

Weber, Marjorie G; Keeler, Kathleen H

2013-06-01

Understanding the evolutionary patterns of ecologically relevant traits is a central goal in plant biology. However, for most important traits, we lack the comprehensive understanding of their taxonomic distribution needed to evaluate their evolutionary mode and tempo across the tree of life. Here we evaluate the broad phylogenetic patterns of a common plant-defence trait found across vascular plants: extrafloral nectaries (EFNs), plant glands that secrete nectar and are located outside the flower. EFNs typically defend plants indirectly by attracting invertebrate predators who reduce herbivory. Records of EFNs published over the last 135 years were compiled. After accounting for changes in taxonomy, phylogenetic comparative methods were used to evaluate patterns of EFN evolution, using a phylogeny of over 55 000 species of vascular plants. Using comparisons of parametric and non-parametric models, the true number of species with EFNs likely to exist beyond the current list was estimated. To date, EFNs have been reported in 3941 species representing 745 genera in 108 families, about 1-2 % of vascular plant species and approx. 21 % of families. They are found in 33 of 65 angiosperm orders. Foliar nectaries are known in four of 36 fern families. Extrafloral nectaries are unknown in early angiosperms, magnoliids and gymnosperms. They occur throughout monocotyledons, yet most EFNs are found within eudicots, with the bulk of species with EFNs being rosids. Phylogenetic analyses strongly support the repeated gain and loss of EFNs across plant clades, especially in more derived dicot families, and suggest that EFNs are found in a minimum of 457 independent lineages. However, model selection methods estimate that the number of unreported cases of EFNs may be as high as the number of species already reported. EFNs are widespread and evolutionarily labile traits that have repeatedly evolved a remarkable number of times in vascular plants. Our current understanding of the phylogenetic patterns of EFNs makes them powerful candidates for future work exploring the drivers of their evolutionary origins, shifts, and losses.

Hawaiian angiosperm radiations of North American origin

PubMed Central

Baldwin, Bruce G.; Wagner, Warren L.

2010-01-01

Background Putative phytogeographical links between America (especially North America) and the Hawaiian Islands have figured prominently in disagreement and debate about the origin of Pacific floras and the efficacy of long-distance (oversea) plant dispersal, given the obstacles to explaining such major disjunctions by vicariance. Scope Review of past efforts, and of progress over the last 20 years, toward understanding relationships of Hawaiian angiosperms allows for a historically informed re-evaluation of the American (New World) contribution to Hawaiian diversity and evolutionary activity of American lineages in an insular setting. Conclusions Temperate and boreal North America is a much more important source of Hawaiian flora than suggested by most 20th century authorities on Pacific plant life, such as Fosberg and Skottsberg. Early views of evolution as too slow to account for divergence of highly distinctive endemics within the Hawaiian geological time frame evidently impeded biogeographical understanding, as did lack of appreciation for the importance of rare, often biotically mediated dispersal events and ecological opportunity in island ecosystems. Molecular phylogenetic evidence for North American ancestry of Hawaiian plant radiations, such as the silversword alliance, mints, sanicles, violets, schiedeas and spurges, underlines the potential of long-distance dispersal to shape floras, in accordance with hypotheses championed by Carlquist. Characteristics important to colonization of the islands, such as dispersibility by birds and ancestral hybridization or polyploidy, and ecological opportunities associated with ‘sky islands’ of temperate or boreal climate in the tropical Hawaiian archipelago may have been key to extensive diversification of endemic lineages of North American origin that are among the most species-rich clades of Hawaiian plants. Evident youth of flowering-plant lineages from North America is highly consistent with recent geological evidence for lack of high-elevation settings in the Hawaiian chain immediately prior to formation of the oldest, modern high-elevation island, Kaua‘i. PMID:20382966

Accelerated Gene Evolution and Subfunctionalization in thePseudotetraploid Frog Xenopus Laevis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hellsten, Uffe; Khokha, Mustafa K.; Grammar, Timothy C.

2007-03-01

Ancient whole genome duplications have been implicated in the vertebrate and teleost radiations, and in the emergence of diverse angiosperm lineages, but the evolutionary response to such a perturbation is still poorly understood. The African clawed frog Xenopus laevis experienced a relatively recent tetraploidization {approx} 40 million years ago. Analysis of the considerable amount of EST sequence available for this species together with the genome sequence of the related diploid Xenopus tropicalis provides a unique opportunity to study the genomic response to whole genome duplication.

A combinatorial morphospace for angiosperm pollen

NASA Astrophysics Data System (ADS)

Mander, Luke

2016-04-01

The morphology of angiosperm (flowering plant) pollen is extraordinarily diverse. This diversity results from variations in the morphology of discrete anatomical components. These components include the overall shape of a pollen grain, the stratification of the exine, the number and form of any apertures, the type of dispersal unit, and the nature of any surface ornamentation. Different angiosperm pollen morphotypes reflect different combinations of these discrete components. In this talk, I ask the following question: given the anatomical components of angiosperm pollen that are known to exist in the plant kingdom, how many unique biologically plausible combinations of these components are there? I explore this question from the perspective of enumerative combinatorics using an algorithm I have written in the Python programming language. This algorithm (1) calculates the number of combinations of these components; (2) enumerates those combinations; and (3) graphically displays those combinations. The result is a combinatorial morphospace that reflects an underlying notion that the process of morphogenesis in angiosperm pollen can be thought of as an n choose k counting problem. I compare the morphology of extant and fossil angiosperm pollen grains to this morphospace, and suggest that from a combinatorial point of view angiosperm pollen is not as diverse as it could be, which may be a result of developmental constraints.

A Role for MORE AXILLARY GROWTH1 (MAX1) in Evolutionary Diversity in Strigolactone Signaling Upstream of MAX21[C][W][OA

PubMed Central

Challis, Richard J.; Hepworth, Jo; Mouchel, Céline; Waites, Richard; Leyser, Ottoline

2013-01-01

Strigolactones (SLs) are carotenoid-derived phytohormones with diverse roles. They are secreted from roots as attractants for arbuscular mycorrhizal fungi and have a wide range of endogenous functions, such as regulation of root and shoot system architecture. To date, six genes associated with SL synthesis and signaling have been molecularly identified using the shoot-branching mutants more axillary growth (max) of Arabidopsis (Arabidopsis thaliana) and dwarf (d) of rice (Oryza sativa). Here, we present a phylogenetic analysis of the MAX/D genes to clarify the relationships of each gene with its wider family and to allow the correlation of events in the evolution of the genes with the evolution of SL function. Our analysis suggests that the notion of a distinct SL pathway is inappropriate. Instead, there may be a diversity of SL-like compounds, the response to which requires a D14/D14-like protein. This ancestral system could have been refined toward distinct ligand-specific pathways channeled through MAX2, the most downstream known component of SL signaling. MAX2 is tightly conserved among land plants and is more diverged from its nearest sister clade than any other SL-related gene, suggesting a pivotal role in the evolution of SL signaling. By contrast, the evidence suggests much greater flexibility upstream of MAX2. The MAX1 gene is a particularly strong candidate for contributing to diversification of inputs upstream of MAX2. Our functional analysis of the MAX1 family demonstrates the early origin of its catalytic function and both redundancy and functional diversification associated with its duplication in angiosperm lineages. PMID:23424248

The Evolution of Haploid Chromosome Numbers in the Sunflower Family

PubMed Central

Mota, Lucie; Torices, Rubén; Loureiro, João

2016-01-01

Chromosome number changes during the evolution of angiosperms are likely to have played a major role in speciation. Their study is of utmost importance, especially now, as a probabilistic model is available to study chromosome evolution within a phylogenetic framework. In the present study, likelihood models of chromosome number evolution were fitted to the largest family of flowering plants, the Asteraceae. Specifically, a phylogenetic supertree of this family was used to reconstruct the ancestral chromosome number and infer genomic events. Our approach inferred that the ancestral chromosome number of the family is n = 9. Also, according to the model that best explained our data, the evolution of haploid chromosome numbers in Asteraceae was a very dynamic process, with genome duplications and descending dysploidy being the most frequent genomic events in the evolution of this family. This model inferred more than one hundred whole genome duplication events; however, it did not find evidence for a paleopolyploidization at the base of this family, which has previously been hypothesized on the basis of sequence data from a limited number of species. The obtained results and potential causes of these discrepancies are discussed. PMID:27797951

Potential for the evolution of heavy metal tolerance in Bryum argenteum, a moss. II. Generalized tolerances among diverse populations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaw, A.J.; Albright, D.L.

Tolerance of copper, zinc, lead, and nickel were measured in two individuals from each of seven populations of Bryum argenteum. The populations represented a range of habitats including industrial sites subject to atmospheric metal deposition, metal-contaminated mine tailings, serpentine barrens, and urban areas. Nevertheless, there was no evidence of adaptive differentiation in tolerance to any of the metals. Populations did differ significantly in general growth vigor across all experimental treatments. These observations contrast with results from studies of angiosperms, in which the evolution of heavy-metal tolerance almost always involves ecotypic differentiation among populations, but fit an emerging picture of B.more » argenteum as a plastic, broadly tolerant species with surprisingly little genetic differentiation among populations.« less

Pleiotropy, redundancy and the evolution of flowers.

PubMed

Albert, Victor A; Oppenheimer, David G; Lindqvist, Charlotte

2002-07-01

Most angiosperm flowers are tightly integrated, functionally bisexual shoots that have carpels with enclosed ovules. Flowering plants evolved from within the gymnosperms, which lack this combination of innovations. Paradoxically, phylogenetic reconstructions suggest that the flowering plant lineage substantially pre-dates the evolution of flowers themselves. We provide a model based on known gene regulatory networks whereby positive selection on a single, partially redundant gene duplicate 'trapped' the ancestors of flower-bearing plants into the condensed, bisexual state approximately 130 million years ago. The LEAFY (LFY) gene of Arabidopsis encodes a master regulator that functions as the main conduit of environmental signals to the reproductive developmental program. We directly link the elimination of one LFY paralog, pleiotropically maintained in gymnosperms, to the sudden appearance of flowers in the fossil record.

Evolution of plant cell wall: Arabinogalactan-proteins from three moss genera show structural differences compared to seed plants.

PubMed

Bartels, Desirée; Baumann, Alexander; Maeder, Malte; Geske, Thomas; Heise, Esther Marie; von Schwartzenberg, Klaus; Classen, Birgit

2017-05-01

Arabinogalactan-proteins (AGPs) are important proteoglycans of plant cell walls. They seem to be present in most, if not all seed plants, but their occurrence and structure in bryophytes is widely unknown and actually the focus of AGP research. With regard to evolution of plant cell wall, we isolated AGPs from the three mosses Sphagnum sp., Physcomitrella patens and Polytrichastrum formosum. The moss AGPs show structural characteristics common for AGPs of seed plants, but also unique features, especially 3-O-methyl-rhamnose (trivial name acofriose) as terminal monosaccharide not found in arabinogalactan-proteins of angiosperms and 1,2,3-linked galactose as branching point never found in arabinogalactan-proteins before. Copyright © 2017 Elsevier Ltd. All rights reserved.

The role of fire in deep time ecosystems

NASA Astrophysics Data System (ADS)

Scott, Andrew C.; Bond, William J.; Collinson, Margaret E.; Glasspool, Ian J.; Brown, Sarah; Braman, Dennis R.

2010-05-01

Fires are very widespread in the world today and fire has also been common in the deep past. Fire is important in structuring contemporary World vegetation maintaining extensive open vegetation where the climate has the potential to support closed forests. The influence of fire on the structure of vegetation and plant traits present in a community vary depending on the fire regime. The fire regime is the characteristic pattern of fire frequency, severity (amount of biomass removed) and spatial extent. Fire regimes depend on the synergy between external physical factors and the properties of vegetation. Changes in the fire regime can be brought about by changes in external conditions such as climate, but also by changes in vegetation such as changes in flammability or productivity that influence the amount of fuel. For example, invasion of grasses into closed wooded habitats has initiated a ‘grass fire cycle' in many parts of the world triggering cascading changes in vegetation structure and composition from forest to open grassland or savanna woodland. The spread of flammable invasive species, especially grasses, has even altered fire regimes of fire-dependent flammable communities causing catastrophic ecosystem changes. We suggest that the spread of angiosperms in the Cretaceous was promoted by the development of novel fire regimes linked to the evolution of novel, highly productive (and flammable) plants. Within the limits of physical constraints on fire occurrence, Cretaceous angiosperms would have initiated a positive feedback analogous to the grass-fire cycle rapidly accumulating fuel that promoted more frequent fires, which maintained open habitats in which rapid growth-traits of angiosperms would be most favoured promoting rapid fuel accumulation etc. Frequent fires would have altered vegetation structure and composition both by increasing mortality rates of fire-damaged trees and reducing recruitment rates of seedlings and saplings where fires recurred before juveniles had reached "fire-proof" sizes. The effect would be to create more open conditions favouring plants with the angiosperm innovations of high photosynthetic rates, rapid maturation and rapid reproduction relative to gymnosperms. Fire has some analogies to large vertebrate herbivory, particularly in the potential to open forests and create habitat for low-growing sun-loving plants over extensive areas. The role of fire in favouring low-growing ‘ruderal', plants of open habitats is similar to that proposed for dinosaurs. A switch from high-browsing dinosaurs in the Jurassic to low-browsing dinosaurs in the Cretaceous has been noted and it has been argued that the switch in browse height would favour fast-growing angiosperms. The dinosaur hypothesis has recently been tested and found wanting, for example in the timing and coincidence of angiosperm abundance and low vs. high-browsing dinosaurs. Our research of the co-occurrence of dinosaur remains and charcoal assemblages in Dinosaur Provincial Park, Alberta, has suggested that it was a dominance of gymnospermous, woody vegetation that was ravaged by fire. In addition, the co-occurrence of dinosaur remains and charcoal is significant in demonstrating that the some dinosaur bone beds may have formed as a result of extensive post-fire erosion/rapid deposition cycles. In this paper we consider the evidence for and against fire as a major factor promoting vegetation change and angiosperm spread in the Cretaceous.

Re-evaluating the isotopic divide between angiosperms and gymnosperms using n-alkane δ13C values

NASA Astrophysics Data System (ADS)

Bush, R. T.; McInerney, F. A.

2009-12-01

Angiosperm δ13C values are typically 1-3‰ more negative than those of co-occurring gymnosperms. This is known for both bulk leaf and compound-specific values from n-alkanes, which are stable, straight-chain hydrocarbons (C23-C35) found in the epicuticular leaf wax of vascular plants. For n-alkanes, there is a second distinction between the δ13C values of angiosperms and gymnosperms—δ13C values generally decrease with increasing chain-length in angiosperms, while in gymnosperms they increase. These two distinctions have been used to support the ‘plant community change hypothesis’ explaining the difference between the terrestrial and marine carbon isotope excursions during the Paleocene-Eocene Thermal Maximum (PETM.) Preserved n-alkanes from terrestrial paleosols in the Bighorn Basin, Wyoming reveal a negative carbon isotope excursion during the PETM of 4-5‰, which is 1-2‰ greater than the excursion recorded by marine carbonates. The local plant community, known from macrofossils as well as palynoflora, shifted from a deciduous, mixed angiosperm/gymnosperm flora to a suite of evergreen angiosperm species during the PETM. At the end of the PETM, the community returned to a mixed deciduous flora very similar to the original. This change in the plant community could thus magnify the terrestrial negative carbon isotope excursion to the degree necessary to explain its divergence from the marine record. However, the comparison between modern angiosperms and gymnosperms has been made mostly between broadleaf, deciduous angiosperms and evergreen, coniferous gymnosperms. New data analyzing deciduous, coniferous gymnosperms, including Metasequoia glyptostroboides and Taxodium distichum, suggests that the division previously ascribed to taxonomy may actually be based on leaf habit and physiology, specifically broadleaf, deciduous versus needle-leaf, evergreen plants. If differences in n-alkane δ13C values can be described not as angiosperms versus gymnosperms, but as deciduous versus evergreen plants, then a re-examination of the PETM terrestrial carbon isotope excursion and its causes may be necessary.

Expression of a gymnosperm PIN homologous gene correlates with auxin immunolocalization pattern at cotyledon formation and in demarcation of the procambium during Picea abies somatic embryo development and in seedling tissues.

PubMed

Palovaara, Joakim; Hallberg, Henrik; Stasolla, Claudio; Luit, Bert; Hakman, Inger

2010-04-01

In seed plants, the body organization is established during embryogenesis and is uniform across gymnosperms and angiosperms, despite differences during early embryogeny. Evidence from angiosperms implicates the plant hormone auxin and its polar transport, mainly established by the PIN family of auxin efflux transporters, in the patterning of embryos. Here, PaPIN1 from Norway spruce (Picea abies [L.] Karst.), a gene widely expressed in conifer tissues and organs, was characterized and its expression and localization patterns were determined with reverse transcription polymerase chain reaction and in situ hybridization during somatic embryo development and in seedlings. PaPIN1 shares the predicted structure of other PIN proteins, but its central hydrophilic loop is longer than most PINs. In phylogenetic analyses, PaPIN1 clusters with Arabidopsis thaliana (L.) Heynh. PIN3, PIN4 and PIN7, but its expression pattern also suggests similarity to PIN1. The PaPIN1 expression signal was high in the protoderm of pre-cotyledonary embryos, but not if embryos were pre-treated with the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). This, together with a high auxin immunolocalization signal in this cell layer, suggests a role of PaPIN1 during cotyledon formation. At later stages, high PaPIN1 expression was observed in differentiating procambium, running from the tip of incipient cotyledons down through the embryo axis and to the root apical meristem (RAM), although the mode of RAM specification in conifer embryos differs from that of most angiosperms. Also, the PaPIN1 in situ signal was high in seedling root tips including root cap columella cells. The results thus suggest that PaPIN1 provides an ancient function associated with auxin transport and embryo pattern formation prior to the separation of angiosperms and gymnosperms, in spite of some morphological differences.

Temperate radiations and dying embers of a tropical past: the diversification of Viburnum.

PubMed

Spriggs, Elizabeth L; Clement, Wendy L; Sweeney, Patrick W; Madriñán, Santiago; Edwards, Erika J; Donoghue, Michael J

2015-07-01

We used a near-complete phylogeny for the angiosperm clade Viburnum to assess lineage diversification rates, and to examine possible morphological and ecological factors driving radiations. Maximum-likelihood and Bayesian approaches identified shifts in diversification rate and possible links to character evolution. We inferred the ancestral environment for Viburnum and changes in diversification dynamics associated with subsequent biome shifts. Viburnum probably diversified in tropical forests of Southeast Asia in the Eocene, with three subsequent radiations in temperate clades during the Miocene. Four traits (purple fruits, extrafloral nectaries, bud scales and toothed leaves) were statistically associated with higher rates of diversification. However, we argue that these traits are unlikely to be driving diversification directly. Instead, two radiations were associated with the occupation of mountainous regions and a third with repeated shifts between colder and warmer temperate forests. Early-branching depauperate lineages imply that the rare lowland tropical species are 'dying embers' of once more diverse lineages; net diversification rates in Viburnum likely decreased in these tropical environments after the Oligocene. We suggest that 'taxon pulse' dynamics might characterize other temperate plant lineages. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Horizontal Transfer of Non-LTR Retrotransposons from Arthropods to Flowering Plants.

PubMed

Gao, Dongying; Chu, Ye; Xia, Han; Xu, Chunming; Heyduk, Karolina; Abernathy, Brian; Ozias-Akins, Peggy; Leebens-Mack, James H; Jackson, Scott A

2018-02-01

Even though lateral movements of transposons across families and even phyla within multicellular eukaryotic kingdoms have been found, little is known about transposon transfer between the kingdoms Animalia and Plantae. We discovered a novel non-LTR retrotransposon, AdLINE3, in a wild peanut species. Sequence comparisons and phylogenetic analyses indicated that AdLINE3 is a member of the RTE clade, originally identified in a nematode and rarely reported in plants. We identified RTE elements in 82 plants, spanning angiosperms to algae, including recently active elements in some flowering plants. RTE elements in flowering plants were likely derived from a single family we refer to as An-RTE. Interestingly, An-RTEs show significant DNA sequence identity with non-LTR retroelements from 42 animals belonging to four phyla. Moreover, the sequence identity of RTEs between two arthropods and two plants was higher than that of homologous genes. Phylogenetic and evolutionary analyses of RTEs from both animals and plants suggest that the An-RTE family was likely transferred horizontally into angiosperms from an ancient aphid(s) or ancestral arthropod(s). Notably, some An-RTEs were recruited as coding sequences of functional genes participating in metabolic or other biochemical processes in plants. This is the first potential example of horizontal transfer of transposons between animals and flowering plants. Our findings help to understand exchanges of genetic material between the kingdom Animalia and Plantae and suggest arthropods likely impacted on plant genome evolution. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Functional diversification of Arabidopsis SEC1-related SM proteins in cytokinetic and secretory membrane fusion.

PubMed

Karnahl, Matthias; Park, Misoon; Krause, Cornelia; Hiller, Ulrike; Mayer, Ulrike; Stierhof, York-Dieter; Jürgens, Gerd

2018-06-12

Sec1/Munc18 (SM) proteins contribute to membrane fusion by interacting with Qa-SNAREs or nascent trans -SNARE complexes. Gymnosperms and the basal angiosperm Amborella have only a single SEC1 gene related to the KEULE gene in Arabidopsis However, the genomes of most angiosperms including Arabidopsis encode three SEC1-related SM proteins of which only KEULE has been functionally characterized as interacting with the cytokinesis-specific Qa-SNARE KNOLLE during cell-plate formation. Here we analyze the closest paralog of KEULE named SEC1B. In contrast to the cytokinesis defects of keule mutants, sec1b mutants are homozygous viable. However, the keule sec1b double mutant was nearly gametophytically lethal, displaying collapsed pollen grains, which suggests substantial overlap between SEC1B and KEULE functions in secretion-dependent growth. SEC1B had a strong preference for interaction with the evolutionarily ancient Qa-SNARE SYP132 involved in secretion and cytokinesis, whereas KEULE interacted with both KNOLLE and SYP132. This differential interaction with Qa-SNAREs is likely conferred by domains 1 and 2a of the two SM proteins. Comparative analysis of all four possible combinations of the relevant SEC1 Qa-SNARE double mutants revealed that in cytokinesis, the interaction of SEC1B with KNOLLE plays no role, whereas the interaction of KEULE with KNOLLE is prevalent and functionally as important as the interactions of both SEC1B and KEU with SYP132 together. Our results suggest that functional diversification of the two SEC1-related SM proteins during angiosperm evolution resulted in enhanced interaction of SEC1B with Qa-SNARE SYP132, and thus a predominant role of SEC1B in secretion.

Subgroup 4 R2R3-MYBs in conifer trees: gene family expansion and contribution to the isoprenoid- and flavonoid-oriented responses

PubMed Central

Bedon, Frank; Bomal, Claude; Caron, Sébastien; Levasseur, Caroline; Boyle, Brian; Mansfield, Shawn D.; Schmidt, Axel; Gershenzon, Jonathan; Grima-Pettenati, Jacqueline; Séguin, Armand; MacKay, John

2010-01-01

Transcription factors play a fundamental role in plants by orchestrating temporal and spatial gene expression in response to environmental stimuli. Several R2R3-MYB genes of the Arabidopsis subgroup 4 (Sg4) share a C-terminal EAR motif signature recently linked to stress response in angiosperm plants. It is reported here that nearly all Sg4 MYB genes in the conifer trees Picea glauca (white spruce) and Pinus taeda (loblolly pine) form a monophyletic clade (Sg4C) that expanded following the split of gymnosperm and angiosperm lineages. Deeper sequencing in P. glauca identified 10 distinct Sg4C sequences, indicating over-represention of Sg4 sequences compared with angiosperms such as Arabidopsis, Oryza, Vitis, and Populus. The Sg4C MYBs share the EAR motif core. Many of them had stress-responsive transcript profiles after wounding, jasmonic acid (JA) treatment, or exposure to cold in P. glauca and P. taeda, with MYB14 transcripts accumulating most strongly and rapidly. Functional characterization was initiated by expressing the P. taeda MYB14 (PtMYB14) gene in transgenic P. glauca plantlets with a tissue-preferential promoter (cinnamyl alcohol dehydrogenase) and a ubiquitous gene promoter (ubiquitin). Histological, metabolite, and transcript (microarray and targeted quantitiative real-time PCR) analyses of PtMYB14 transgenics, coupled with mechanical wounding and JA application experiments on wild-type plantlets, allowed identification of PtMYB14 as a putative regulator of an isoprenoid-oriented response that leads to the accumulation of sesquiterpene in conifers. Data further suggested that PtMYB14 may contribute to a broad defence response implicating flavonoids. This study also addresses the potential involvement of closely related Sg4C sequences in stress responses and plant evolution. PMID:20732878

Comparative analysis of the small RNA transcriptomes of Pinus contorta and Oryza sativa

PubMed Central

Morin, Ryan D.; Aksay, Gozde; Dolgosheina, Elena; Ebhardt, H. Alexander; Magrini, Vincent; Mardis, Elaine R.; Sahinalp, S. Cenk; Unrau, Peter J.

2008-01-01

The diversity of microRNAs and small-interfering RNAs has been extensively explored within angiosperms by focusing on a few key organisms such as Oryza sativa and Arabidopsis thaliana. A deeper division of the plants is defined by the radiation of the angiosperms and gymnosperms, with the latter comprising the commercially important conifers. The conifers are expected to provide important information regarding the evolution of highly conserved small regulatory RNAs. Deep sequencing provides the means to characterize and quantitatively profile small RNAs in understudied organisms such as these. Pyrosequencing of small RNAs from O. sativa revealed, as expected, ∼21- and ∼24-nt RNAs. The former contained known microRNAs, and the latter largely comprised intergenic-derived sequences likely representing heterochromatin siRNAs. In contrast, sequences from Pinus contorta were dominated by 21-nt small RNAs. Using a novel sequence-based clustering algorithm, we identified sequences belonging to 18 highly conserved microRNA families in P. contorta as well as numerous clusters of conserved small RNAs of unknown function. Using multiple methods, including expressed sequence folding and machine learning algorithms, we found a further 53 candidate novel microRNA families, 51 appearing specific to the P. contorta library. In addition, alignment of small RNA sequences to the O. sativa genome revealed six perfectly conserved classes of small RNA that included chloroplast transcripts and specific types of genomic repeats. The conservation of microRNAs and other small RNAs between the conifers and the angiosperms indicates that important RNA silencing processes were highly developed in the earliest spermatophytes. Genomic mapping of all sequences to the O. sativa genome can be viewed at http://microrna.bcgsc.ca/cgi-bin/gbrowse/rice_build_3/. PMID:18323537

The interplay between inflorescence development and function as the crucible of architectural diversity

PubMed Central

Harder, Lawrence D.; Prusinkiewicz, Przemyslaw

2013-01-01

Background Most angiosperms present flowers in inflorescences, which play roles in reproduction, primarily related to pollination, beyond those served by individual flowers alone. An inflorescence's overall reproductive contribution depends primarily on the three-dimensional arrangement of the floral canopy and its dynamics during its flowering period. These features depend in turn on characteristics of the underlying branching structure (scaffold) that supports and supplies water and nutrients to the floral canopy. This scaffold is produced by developmental algorithms that are genetically specified and hormonally mediated. Thus, the extensive inflorescence diversity evident among angiosperms evolves through changes in the developmental programmes that specify scaffold characteristics, which in turn modify canopy features that promote reproductive performance in a particular pollination and mating environment. Nevertheless, developmental and ecological aspects of inflorescences have typically been studied independently, limiting comprehensive understanding of the relations between inflorescence form, reproductive function, and evolution. Scope This review fosters an integrated perspective on inflorescences by summarizing aspects of their development and pollination function that enable and guide inflorescence evolution and diversification. Conclusions The architecture of flowering inflorescences comprises three related components: topology (branching patterns, flower number), geometry (phyllotaxis, internode and pedicel lengths, three-dimensional flower arrangement) and phenology (flower opening rate and longevity, dichogamy). Genetic and developmental evidence reveals that these components are largely subject to quantitative control. Consequently, inflorescence evolution proceeds along a multidimensional continuum. Nevertheless, some combinations of topology, geometry and phenology are represented more commonly than others, because they serve reproductive function particularly effectively. For wind-pollinated species, these combinations often represent compromise solutions to the conflicting physical influences on pollen removal, transport and deposition. For animal-pollinated species, dominant selective influences include the conflicting benefits of large displays for attracting pollinators and of small displays for limiting among-flower self-pollination. The variety of architectural components that comprise inflorescences enable diverse resolutions of these conflicts. PMID:23243190

The Evolution of Land Plants and the Silicate Weathering Feedback

NASA Astrophysics Data System (ADS)

Ibarra, D. E.; Caves Rugenstein, J. K.; Bachan, A.; Baresch, A.; Lau, K. V.; Thomas, D.; Lee, J. E.; Boyce, C. K.; Chamberlain, C. P.

2017-12-01

It has long been recognized that the advent of vascular plants in the Paleozoic must have changed silicate weathering and fundamentally altered the long-term carbon cycle. Efforts to quantify these effects have been formulated in carbon cycle models that are, in part, calibrated by weathering studies of modern plant communities. In models of the long-term carbon cycle, plants play a key role in controlling atmospheric CO2, particularly in the late Paleozoic. We test the impact of some established and recent theories regarding plant-enhanced weathering by coupling a one-dimensional vapor transport model to a reactive transport model of silicate weathering. In this coupled model, we evaluate consequences of plant evolutionary innovation that have not been mechanistically incorporated into most existing models: 1) the role of evolutionary shifts in plant transpiration in enhancing silicate weathering by increasing downwind transport and recycling of water vapor to continental interiors; 2) the importance of deeply-rooted plants and their associated microbial communities in increasing soil CO2 and weathering zone length scales; and, 3) the cumulative effect of these processes. Our modeling approach is framed by energy/supply constraints calibrated for minimally vegetated-, vascular plant forested-, and angiosperm-worlds. We find that the emergence of widespread transpiration and associated inland vapor recycling approximately doubles weathering solute concentrations when deep-rooted vascular plants (Devonian-Carboniferous) fully replace a minimally vegetated (pre-Devonian) world. The later evolution of angiosperms (Cretaceous and Cenozoic) and subsequent increase in transpiration fluxes increase weathering solute concentrations by approximately an additional 20%. Our estimates of the changes in weatherability caused by land plant evolution are of a similar magnitude, but explained with new process-based mechanisms, than those used in existing carbon cycle models. We suggest a feedback where the increase in solute concentrations is compensated by a decrease in runoff and temperature, permitting lower steady-state atmospheric pCO2. Consequently, plants have increased the strength of the climatic feedback on silicate weathering since the late Paleozoic.

The draft genome of the transgenic tropical fruit tree papaya (Carica papaya Linnaeus)

PubMed Central

Ming, Ray; Hou, Shaobin; Feng, Yun; Yu, Qingyi; Dionne-Laporte, Alexandre; Saw, Jimmy H.; Senin, Pavel; Wang, Wei; Ly, Benjamin V.; Lewis, Kanako L. T.; Salzberg, Steven L.; Feng, Lu; Jones, Meghan R.; Skelton, Rachel L.; Murray, Jan E.; Chen, Cuixia; Qian, Wubin; Shen, Junguo; Du, Peng; Eustice, Moriah; Tong, Eric; Tang, Haibao; Lyons, Eric; Paull, Robert E.; Michael, Todd P.; Wall, Kerr; Rice, Danny W.; Albert, Henrik; Wang, Ming-Li; Zhu, Yun J.; Schatz, Michael; Nagarajan, Niranjan; Acob, Ricelle A.; Guan, Peizhu; Blas, Andrea; Wai, Ching Man; Ackerman, Christine M.; Ren, Yan; Liu, Chao; Wang, Jianmei; Wang, Jianping; Na, Jong-Kuk; Shakirov, Eugene V.; Haas, Brian; Thimmapuram, Jyothi; Nelson, David; Wang, Xiyin; Bowers, John E.; Gschwend, Andrea R.; Delcher, Arthur L.; Singh, Ratnesh; Suzuki, Jon Y.; Tripathi, Savarni; Neupane, Kabi; Wei, Hairong; Irikura, Beth; Paidi, Maya; Jiang, Ning; Zhang, Wenli; Presting, Gernot; Windsor, Aaron; Navajas-Pérez, Rafael; Torres, Manuel J.; Feltus, F. Alex; Porter, Brad; Li, Yingjun; Burroughs, A. Max; Luo, Ming-Cheng; Liu, Lei; Christopher, David A.; Mount, Stephen M.; Moore, Paul H.; Sugimura, Tak; Jiang, Jiming; Schuler, Mary A.; Friedman, Vikki; Mitchell-Olds, Thomas; Shippen, Dorothy E.; dePamphilis, Claude W.; Palmer, Jeffrey D.; Freeling, Michael; Paterson, Andrew H.; Gonsalves, Dennis; Wang, Lei; Alam, Maqsudul

2010-01-01

Papaya, a fruit crop cultivated in tropical and subtropical regions, is known for its nutritional benefits and medicinal applications. Here we report a 3× draft genome sequence of ‘SunUp’ papaya, the first commercial virus-resistant transgenic fruit tree1 to be sequenced. The papaya genome is three times the size of the Arabidopsis genome, but contains fewer genes, including significantly fewer disease-resistance gene analogues. Comparison of the five sequenced genomes suggests a minimal angiosperm gene set of 13,311. A lack of recent genome duplication, atypical of other angiosperm genomes sequenced so far2–5, may account for the smaller papaya gene number in most functional groups. Nonetheless, striking amplifications in gene number within particular functional groups suggest roles in the evolution of tree-like habit, deposition and remobilization of starch reserves, attraction of seed dispersal agents, and adaptation to tropical daylengths. Transgenesis at three locations is closely associated with chloroplast insertions into the nuclear genome, and with topoisomerase I recognition sites. Papaya offers numerous advantages as a system for fruit-tree functional genomics, and this draft genome sequence provides the foundation for revealing the basis of Carica's distinguishing morpho-physiological, medicinal and nutritional properties. PMID:18432245

The draft genome of the transgenic tropical fruit tree papaya (Carica papaya Linnaeus).

PubMed

Ming, Ray; Hou, Shaobin; Feng, Yun; Yu, Qingyi; Dionne-Laporte, Alexandre; Saw, Jimmy H; Senin, Pavel; Wang, Wei; Ly, Benjamin V; Lewis, Kanako L T; Salzberg, Steven L; Feng, Lu; Jones, Meghan R; Skelton, Rachel L; Murray, Jan E; Chen, Cuixia; Qian, Wubin; Shen, Junguo; Du, Peng; Eustice, Moriah; Tong, Eric; Tang, Haibao; Lyons, Eric; Paull, Robert E; Michael, Todd P; Wall, Kerr; Rice, Danny W; Albert, Henrik; Wang, Ming-Li; Zhu, Yun J; Schatz, Michael; Nagarajan, Niranjan; Acob, Ricelle A; Guan, Peizhu; Blas, Andrea; Wai, Ching Man; Ackerman, Christine M; Ren, Yan; Liu, Chao; Wang, Jianmei; Wang, Jianping; Na, Jong-Kuk; Shakirov, Eugene V; Haas, Brian; Thimmapuram, Jyothi; Nelson, David; Wang, Xiyin; Bowers, John E; Gschwend, Andrea R; Delcher, Arthur L; Singh, Ratnesh; Suzuki, Jon Y; Tripathi, Savarni; Neupane, Kabi; Wei, Hairong; Irikura, Beth; Paidi, Maya; Jiang, Ning; Zhang, Wenli; Presting, Gernot; Windsor, Aaron; Navajas-Pérez, Rafael; Torres, Manuel J; Feltus, F Alex; Porter, Brad; Li, Yingjun; Burroughs, A Max; Luo, Ming-Cheng; Liu, Lei; Christopher, David A; Mount, Stephen M; Moore, Paul H; Sugimura, Tak; Jiang, Jiming; Schuler, Mary A; Friedman, Vikki; Mitchell-Olds, Thomas; Shippen, Dorothy E; dePamphilis, Claude W; Palmer, Jeffrey D; Freeling, Michael; Paterson, Andrew H; Gonsalves, Dennis; Wang, Lei; Alam, Maqsudul

2008-04-24

Papaya, a fruit crop cultivated in tropical and subtropical regions, is known for its nutritional benefits and medicinal applications. Here we report a 3x draft genome sequence of 'SunUp' papaya, the first commercial virus-resistant transgenic fruit tree to be sequenced. The papaya genome is three times the size of the Arabidopsis genome, but contains fewer genes, including significantly fewer disease-resistance gene analogues. Comparison of the five sequenced genomes suggests a minimal angiosperm gene set of 13,311. A lack of recent genome duplication, atypical of other angiosperm genomes sequenced so far, may account for the smaller papaya gene number in most functional groups. Nonetheless, striking amplifications in gene number within particular functional groups suggest roles in the evolution of tree-like habit, deposition and remobilization of starch reserves, attraction of seed dispersal agents, and adaptation to tropical daylengths. Transgenesis at three locations is closely associated with chloroplast insertions into the nuclear genome, and with topoisomerase I recognition sites. Papaya offers numerous advantages as a system for fruit-tree functional genomics, and this draft genome sequence provides the foundation for revealing the basis of Carica's distinguishing morpho-physiological, medicinal and nutritional properties.

Heterostyly accelerates diversification via reduced extinction in primroses.

PubMed

de Vos, Jurriaan M; Hughes, Colin E; Schneeweiss, Gerald M; Moore, Brian R; Conti, Elena

2014-06-07

The exceptional species diversity of flowering plants, exceeding that of their sister group more than 250-fold, is especially evident in floral innovations, interactions with pollinators and sexual systems. Multiple theories, emphasizing flower-pollinator interactions, genetic effects of mating systems or high evolvability, predict that floral evolution profoundly affects angiosperm diversification. However, consequences for speciation and extinction dynamics remain poorly understood. Here, we investigate trajectories of species diversification focusing on heterostyly, a remarkable floral syndrome where outcrossing is enforced via cross-compatible floral morphs differing in placement of their respective sexual organs. Heterostyly evolved at least 20 times independently in angiosperms. Using Darwin's model for heterostyly, the primrose family, we show that heterostyly accelerates species diversification via decreasing extinction rates rather than increasing speciation rates, probably owing to avoidance of the negative genetic effects of selfing. However, impact of heterostyly appears to differ over short and long evolutionary time-scales: the accelerating effect of heterostyly on lineage diversification is manifest only over long evolutionary time-scales, whereas recent losses of heterostyly may prompt ephemeral bursts of speciation. Our results suggest that temporal or clade-specific conditions may ultimately determine the net effects of specific traits on patterns of species diversification.

Comparative evolution of flower and fruit morphology

PubMed Central

Whitney, Kenneth D.

2009-01-01

Angiosperm diversification has resulted in a vast array of plant morphologies. Only recently has it been appreciated that diversification might have proceeded quite differently for the two key diagnostic structures of this clade, flowers and fruits. These structures are hypothesized to have experienced different selective pressures via their interactions with animals in dispersal mutualisms, resulting in a greater amount of morphological diversification in animal-pollinated flowers than in animal-dispersed fruits. I tested this idea using size and colour traits for the flowers and fruits of 472 species occurring in three floras (St John, Hawaii and the Great Plains). Phylogenetically controlled analyses of nearest-neighbour distances in multidimensional trait space matched the predicted pattern: in each of the three floras, flowers were more divergent from one another than were fruits. In addition, the spacing of species clusters differed for flowers versus fruits in the flora of St John, with clusters in flower space more divergent than those in fruit space. The results are consistent with the idea that a major driver of angiosperm diversification has been stronger selection for divergent floral morphology than for divergent fruit morphology, although genetic, physiological and ecological constraints may also play a role. PMID:19474045

Heterostyly accelerates diversification via reduced extinction in primroses

PubMed Central

de Vos, Jurriaan M.; Hughes, Colin E.; Schneeweiss, Gerald M.; Moore, Brian R.; Conti, Elena

2014-01-01

The exceptional species diversity of flowering plants, exceeding that of their sister group more than 250-fold, is especially evident in floral innovations, interactions with pollinators and sexual systems. Multiple theories, emphasizing flower–pollinator interactions, genetic effects of mating systems or high evolvability, predict that floral evolution profoundly affects angiosperm diversification. However, consequences for speciation and extinction dynamics remain poorly understood. Here, we investigate trajectories of species diversification focusing on heterostyly, a remarkable floral syndrome where outcrossing is enforced via cross-compatible floral morphs differing in placement of their respective sexual organs. Heterostyly evolved at least 20 times independently in angiosperms. Using Darwin's model for heterostyly, the primrose family, we show that heterostyly accelerates species diversification via decreasing extinction rates rather than increasing speciation rates, probably owing to avoidance of the negative genetic effects of selfing. However, impact of heterostyly appears to differ over short and long evolutionary time-scales: the accelerating effect of heterostyly on lineage diversification is manifest only over long evolutionary time-scales, whereas recent losses of heterostyly may prompt ephemeral bursts of speciation. Our results suggest that temporal or clade-specific conditions may ultimately determine the net effects of specific traits on patterns of species diversification. PMID:24759859

Evolutionary heritage influences Amazon tree ecology.

PubMed

Coelho de Souza, Fernanda; Dexter, Kyle G; Phillips, Oliver L; Brienen, Roel J W; Chave, Jerome; Galbraith, David R; Lopez Gonzalez, Gabriela; Monteagudo Mendoza, Abel; Pennington, R Toby; Poorter, Lourens; Alexiades, Miguel; Álvarez-Dávila, Esteban; Andrade, Ana; Aragão, Luis E O C; Araujo-Murakami, Alejandro; Arets, Eric J M M; Aymard C, Gerardo A; Baraloto, Christopher; Barroso, Jorcely G; Bonal, Damien; Boot, Rene G A; Camargo, José L C; Comiskey, James A; Valverde, Fernando Cornejo; de Camargo, Plínio B; Di Fiore, Anthony; Elias, Fernando; Erwin, Terry L; Feldpausch, Ted R; Ferreira, Leandro; Fyllas, Nikolaos M; Gloor, Emanuel; Herault, Bruno; Herrera, Rafael; Higuchi, Niro; Honorio Coronado, Eurídice N; Killeen, Timothy J; Laurance, William F; Laurance, Susan; Lloyd, Jon; Lovejoy, Thomas E; Malhi, Yadvinder; Maracahipes, Leandro; Marimon, Beatriz S; Marimon-Junior, Ben H; Mendoza, Casimiro; Morandi, Paulo; Neill, David A; Vargas, Percy Núñez; Oliveira, Edmar A; Lenza, Eddie; Palacios, Walter A; Peñuela-Mora, Maria C; Pipoly, John J; Pitman, Nigel C A; Prieto, Adriana; Quesada, Carlos A; Ramirez-Angulo, Hirma; Rudas, Agustin; Ruokolainen, Kalle; Salomão, Rafael P; Silveira, Marcos; Stropp, Juliana; Ter Steege, Hans; Thomas-Caesar, Raquel; van der Hout, Peter; van der Heijden, Geertje M F; van der Meer, Peter J; Vasquez, Rodolfo V; Vieira, Simone A; Vilanova, Emilio; Vos, Vincent A; Wang, Ophelia; Young, Kenneth R; Zagt, Roderick J; Baker, Timothy R

2016-12-14

Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary diversity, ecosystem function and the response of tropical forests to global change. © 2016 The Authors.

Evolutionary heritage influences Amazon tree ecology

PubMed Central

Coelho de Souza, Fernanda; Dexter, Kyle G.; Phillips, Oliver L.; Brienen, Roel J. W.; Chave, Jerome; Galbraith, David R.; Lopez Gonzalez, Gabriela; Monteagudo Mendoza, Abel; Pennington, R. Toby; Poorter, Lourens; Alexiades, Miguel; Álvarez-Dávila, Esteban; Andrade, Ana; Aragão, Luis E. O. C.; Araujo-Murakami, Alejandro; Arets, Eric J. M. M.; Aymard C, Gerardo A.; Baraloto, Christopher; Barroso, Jorcely G.; Bonal, Damien; Boot, Rene G. A.; Camargo, José L. C.; Comiskey, James A.; Valverde, Fernando Cornejo; de Camargo, Plínio B.; Di Fiore, Anthony; Erwin, Terry L.; Feldpausch, Ted R.; Ferreira, Leandro; Fyllas, Nikolaos M.; Gloor, Emanuel; Herault, Bruno; Herrera, Rafael; Higuchi, Niro; Honorio Coronado, Eurídice N.; Killeen, Timothy J.; Laurance, William F.; Laurance, Susan; Lloyd, Jon; Lovejoy, Thomas E.; Malhi, Yadvinder; Maracahipes, Leandro; Marimon, Beatriz S.; Marimon-Junior, Ben H.; Mendoza, Casimiro; Morandi, Paulo; Neill, David A.; Vargas, Percy Núñez; Oliveira, Edmar A.; Lenza, Eddie; Palacios, Walter A.; Peñuela-Mora, Maria C.; Pipoly, John J.; Pitman, Nigel C. A.; Prieto, Adriana; Quesada, Carlos A.; Ramirez-Angulo, Hirma; Rudas, Agustin; Ruokolainen, Kalle; Salomão, Rafael P.; Silveira, Marcos; ter Steege, Hans; Thomas-Caesar, Raquel; van der Hout, Peter; van der Heijden, Geertje M. F.; van der Meer, Peter J.; Vasquez, Rodolfo V.; Vieira, Simone A.; Vilanova, Emilio; Vos, Vincent A.; Wang, Ophelia; Young, Kenneth R.; Zagt, Roderick J.; Baker, Timothy R.

2016-01-01

Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary diversity, ecosystem function and the response of tropical forests to global change. PMID:27974517

Appraising the roles of nutrient availability, global change, and functional traits during the angiosperm rise to dominance.

PubMed

Mueller, Kevin E; Diefendorf, Aaron F; Freeman, Katherine H; Eissenstat, David M

2010-05-01

To explain the rise of angiosperms during the Cretaceous, Berendse & Scheffer (Ecol. Lett., 12, 2009, 865) invoke feedbacks between leaf litter, soil nutrients, and growth, overlooking other factors affecting resource acquisition by Cretaceous plants. We evaluate their hypothesis, highlight alternative explanations, and emphasize use of a broader framework for understanding the angiosperm radiation.

A combinatorial approach to angiosperm pollen morphology.

PubMed

Mander, Luke

2016-11-30

Angiosperms (flowering plants) are strikingly diverse. This is clearly expressed in the morphology of their pollen grains, which are characterized by enormous variety in their shape and patterning. In this paper, I approach angiosperm pollen morphology from the perspective of enumerative combinatorics. This involves generating angiosperm pollen morphotypes by algorithmically combining character states and enumerating the results of these combinations. I use this approach to generate 3 643 200 pollen morphotypes, which I visualize using a parallel-coordinates plot. This represents a raw morphospace. To compare real-world and theoretical morphologies, I map the pollen of 1008 species of Neotropical angiosperms growing on Barro Colorado Island (BCI), Panama, onto this raw morphospace. This highlights that, in addition to their well-documented taxonomic diversity, Neotropical rainforests also represent an enormous reservoir of morphological diversity. Angiosperm pollen morphospace at BCI has been filled mostly by pollen morphotypes that are unique to single plant species. Repetition of pollen morphotypes among higher taxa at BCI reflects both constraint and convergence. This combinatorial approach to morphology addresses the complexity that results from large numbers of discrete character combinations and could be employed in any situation where organismal form can be captured by discrete morphological characters. © 2016 The Author(s).

A combinatorial approach to angiosperm pollen morphology

PubMed Central

2016-01-01

Angiosperms (flowering plants) are strikingly diverse. This is clearly expressed in the morphology of their pollen grains, which are characterized by enormous variety in their shape and patterning. In this paper, I approach angiosperm pollen morphology from the perspective of enumerative combinatorics. This involves generating angiosperm pollen morphotypes by algorithmically combining character states and enumerating the results of these combinations. I use this approach to generate 3 643 200 pollen morphotypes, which I visualize using a parallel-coordinates plot. This represents a raw morphospace. To compare real-world and theoretical morphologies, I map the pollen of 1008 species of Neotropical angiosperms growing on Barro Colorado Island (BCI), Panama, onto this raw morphospace. This highlights that, in addition to their well-documented taxonomic diversity, Neotropical rainforests also represent an enormous reservoir of morphological diversity. Angiosperm pollen morphospace at BCI has been filled mostly by pollen morphotypes that are unique to single plant species. Repetition of pollen morphotypes among higher taxa at BCI reflects both constraint and convergence. This combinatorial approach to morphology addresses the complexity that results from large numbers of discrete character combinations and could be employed in any situation where organismal form can be captured by discrete morphological characters. PMID:27881756

Tectonic-driven climate change and the diversification of angiosperms.

PubMed

Chaboureau, Anne-Claire; Sepulchre, Pierre; Donnadieu, Yannick; Franc, Alain

2014-09-30

In 1879, Charles Darwin characterized the sudden and unexplained rise of angiosperms during the Cretaceous as an "abominable mystery." The diversification of this clade marked the beginning of a rapid transition among Mesozoic ecosystems and floras formerly dominated by ferns, conifers, and cycads. Although the role of environmental factors has been suggested [Coiffard C, Gómez B (2012) Geol Acta 10(2):181-188], Cretaceous global climate change has barely been considered as a contributor to angiosperm radiation, and focus was put on biotic factors to explain this transition. Here we use a fully coupled climate model driven by Mesozoic paleogeographic maps to quantify and discuss the impact of continental drift on angiosperm expansion and diversification. We show that the decrease of desertic belts between the Triassic and the Cretaceous and the subsequent onset of long-lasting humid conditions during the Late Cretaceous were driven by the breakup of Pangea and were contemporaneous with the first rise of angiosperm diversification. Positioning angiosperm-bearing fossil sites on our paleobioclimatic maps shows a strong match between the location of fossil-rich outcrops and temperate humid zones, indicating that climate change from arid to temperate dominance may have set the stage for the ecological expansion of flowering plants.

PLANT EVOLUTION. Convergent evolution of strigolactone perception enabled host detection in parasitic plants.

PubMed

Conn, Caitlin E; Bythell-Douglas, Rohan; Neumann, Drexel; Yoshida, Satoko; Whittington, Bryan; Westwood, James H; Shirasu, Ken; Bond, Charles S; Dyer, Kelly A; Nelson, David C

2015-07-31

Obligate parasitic plants in the Orobanchaceae germinate after sensing plant hormones, strigolactones, exuded from host roots. In Arabidopsis thaliana, the α/β-hydrolase D14 acts as a strigolactone receptor that controls shoot branching, whereas its ancestral paralog, KAI2, mediates karrikin-specific germination responses. We observed that KAI2, but not D14, is present at higher copy numbers in parasitic species than in nonparasitic relatives. KAI2 paralogs in parasites are distributed into three phylogenetic clades. The fastest-evolving clade, KAI2d, contains the majority of KAI2 paralogs. Homology models predict that the ligand-binding pockets of KAI2d resemble D14. KAI2d transgenes confer strigolactone-specific germination responses to Arabidopsis thaliana. Thus, the KAI2 paralogs D14 and KAI2d underwent convergent evolution of strigolactone recognition, respectively enabling developmental responses to strigolactones in angiosperms and host detection in parasites. Copyright © 2015, American Association for the Advancement of Science.

Non-concerted ITS evolution in Mammillaria (Cactaceae).

PubMed

Harpke, Doerte; Peterson, Angela

2006-12-01

Molecular studies of 21 species of the large Cactaceae genus Mammillaria representing a variety of intrageneric taxonomic levels revealed a high degree of intra-individual polymorphism of the internal transcribed spacer region (ITS1, 5.8S rDNA, ITS2). Only a few of these ITS copies belong to apparently functional genes, whereas most are probably non-functional (pseudogenes). As a multiple gene family, the ITS region is subjected to concerted evolution. However, the high degree of intra-individual polymorphism of up to 36% in ITS1 and up to 35% in ITS2 suggests a non-concerted evolution of these loci in Mammillaria. Conserved angiosperm motifs of ITS1 and ITS2 were compared between genomic and cDNA ITS clones of Mammillaria. Some of these motifs (e.g., ITS1 motif 1, 'TGGT' within ITS2) in combination with the determination of GC-content, length comparisons of the spacers and ITS2 secondary structure (helices II and III) are helpful in the identification of pseudogene rDNA regions.

Extraordinarily High Leaf Selenium to Sulfur Ratios Define ‘Se-accumulator’ Plants

PubMed Central

White, Philip J.; Bowen, Helen C.; Marshall, Bruce; Broadley, Martin R.

2007-01-01

Background and Aims Selenium (Se) and sulfur (S) exhibit similar chemical properties. In flowering plants (angiosperms) selenate and sulfate are acquired and assimilated by common transport and metabolic pathways. It is hypothesized that most angiosperm species show little or no discrimination in the accumulation of Se and S in leaves when their roots are supplied a mixture of selenate and sulfate, but some, termed Se-accumulator plants, selectively accumulate Se in preference to S under these conditions. Methods This paper surveys Se and S accumulation in leaves of 39 angiosperm species, chosen to represent the range of plant Se accumulation phenotypes, grown hydroponically under identical conditions. Results The data show that, when supplied a mixture of selenate and sulfate: (1) plant species differ in both their leaf Se ([Se]leaf) and leaf S ([S]leaf) concentrations; (2) most angiosperms show little discrimination for the accumulation of Se and S in their leaves and, in non-accumulator plants, [Se]leaf and [S]leaf are highly correlated; (3) [Se]leaf in Se-accumulator plants is significantly greater than in other angiosperms, but [S]leaf, although high, is within the range expected for angiosperms in general; and (4) the Se/S quotient in leaves of Se-accumulator plants is significantly higher than in leaves of other angiosperms. Conclusion The traits of extraordinarily high [Se]leaf and leaf Se/S quotients define the distinct elemental composition of Se-accumulator plants. PMID:17525099

The first fossil leaf insect: 47 million years of specialized cryptic morphology and behavior

PubMed Central

Wedmann, Sonja; Bradler, Sven; Rust, Jes

2007-01-01

Stick and leaf insects (insect order Phasmatodea) are represented primarily by twig-imitating slender forms. Only a small percentage (≈1%) of extant phasmids belong to the leaf insects (Phylliinae), which exhibit an extreme form of morphological and behavioral leaf mimicry. Fossils of phasmid insects are extremely rare worldwide. Here we report the first fossil leaf insect, Eophyllium messelensis gen. et sp. nov., from 47-million-year-old deposits at Messel in Germany. The new specimen, a male, is exquisitely preserved and displays the same foliaceous appearance as extant male leaf insects. Clearly, an advanced form of extant angiosperm leaf mimicry had already evolved early in the Eocene. We infer that this trait was combined with a special behavior, catalepsy or “adaptive stillness,” enabling Eophyllium to deceive visually oriented predators. Potential predators reported from the Eocene are birds, early primates, and bats. The combination of primitive and derived characters revealed by Eophyllium allows the determination of its exact phylogenetic position and illuminates the evolution of leaf mimicry for this insect group. It provides direct evidence that Phylliinae originated at least 47 Mya. Eophyllium enlarges the known geographical range of Phylliinae, currently restricted to southeast Asia, which is apparently a relict distribution. This fossil leaf insect bears considerable resemblance to extant individuals in size and cryptic morphology, indicating minimal change in 47 million years. This absence of evolutionary change is an outstanding example of morphological and, probably, behavioral stasis. PMID:17197423

Conserved Organisation of 45S rDNA Sites and rDNA Gene Copy Number among Major Clades of Early Land Plants

PubMed Central

Rosato, Marcela; Kovařík, Aleš; Garilleti, Ricardo; Rosselló, Josep A.

2016-01-01

Genes encoding ribosomal RNA (rDNA) are universal key constituents of eukaryotic genomes, and the nuclear genome harbours hundreds to several thousand copies of each species. Knowledge about the number of rDNA loci and gene copy number provides information for comparative studies of organismal and molecular evolution at various phylogenetic levels. With the exception of seed plants, the range of 45S rDNA locus (encoding 18S, 5.8S and 26S rRNA) and gene copy number variation within key evolutionary plant groups is largely unknown. This is especially true for the three earliest land plant lineages Marchantiophyta (liverworts), Bryophyta (mosses), and Anthocerotophyta (hornworts). In this work, we report the extent of rDNA variation in early land plants, assessing the number of 45S rDNA loci and gene copy number in 106 species and 25 species, respectively, of mosses, liverworts and hornworts. Unexpectedly, the results show a narrow range of ribosomal locus variation (one or two 45S rDNA loci) and gene copies not present in vascular plant lineages, where a wide spectrum is recorded. Mutation analysis of whole genomic reads showed higher (3-fold) intragenomic heterogeneity of Marchantia polymorpha (Marchantiophyta) rDNA compared to Physcomitrella patens (Bryophyta) and two angiosperms (Arabidopsis thaliana and Nicotiana tomentosifomis) suggesting the presence of rDNA pseudogenes in its genome. No association between phylogenetic position, taxonomic adscription and the number of rDNA loci and gene copy number was found. Our results suggest a likely evolutionary rDNA stasis during land colonisation and diversification across 480 myr of bryophyte evolution. We hypothesise that strong selection forces may be acting against ribosomal gene locus amplification. Despite showing a predominant haploid phase and infrequent meiosis, overall rDNA homogeneity is not severely compromised in bryophytes. PMID:27622766

Convergent and correlated evolution of major life-history traits in the angiosperm genus Leucadendron (Proteaceae).

PubMed

Tonnabel, Jeanne; Mignot, Agnès; Douzery, Emmanuel J P; Rebelo, Anthony G; Schurr, Frank M; Midgley, Jeremy; Illing, Nicola; Justy, Fabienne; Orcel, Denis; Olivieri, Isabelle

2014-10-01

Natural selection is expected to cause convergence of life histories among taxa as well as correlated evolution of different life-history traits. Here, we quantify the extent of convergence of five key life-history traits (adult fire survival, seed storage, degree of sexual dimorphism, pollination mode, and seed-dispersal mode) and test hypotheses about their correlated evolution in the genus Leucadendron (Proteaceae) from the fire-prone South African fynbos. We reconstructed a new molecular phylogeny of this highly diverse genus that involves more taxa and molecular markers than previously. This reconstruction identifies new clades that were not detected by previous molecular study and morphological classifications. Using this new phylogeny and robust methods that account for phylogenetic uncertainty, we show that the five life-history traits studied were labile during the evolutionary history of the genus. This diversity allowed us to tackle major questions about the correlated evolution of life-history strategies. We found that species with longer seed-dispersal distances tended to evolve lower pollen-dispersal distance, that insect-pollinated species evolved decreased sexual dimorphism, and that species with a persistent soil seed-bank evolved toward reduced fire-survival ability of adults. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Ecological determinants of mean family age of angiosperm trees in forest communities in China

NASA Astrophysics Data System (ADS)

Qian, Hong; Chen, Shengbin

2016-06-01

Species assemblage in a local community is determined by the interplay of evolutionary and ecological processes. The Tropical Niche Conservatism hypothesis proposes mechanisms underlying patterns of biodiversity in biological communities along environmental gradients. This hypothesis predicts that, among other things, clades in areas with warm or wet environments are, on average, older than those in areas with cold or dry environments. Focusing on angiosperm trees in forests, this study tested the age-related prediction of the Tropical Niche Conservatism hypothesis. We related the mean family age of angiosperm trees in 57 local forests from across China with 23 current and paleo-environmental variables, which included all major temperature- and precipitation-related variables. Our study shows that the mean family age of angiosperm trees in local forests was positively correlated with temperature and precipitation. This finding is consistent with the age-related prediction of the Tropical Niche Conservatism hypothesis. Approximately 85% of the variance in the mean family age of angiosperm trees was explained by temperature-related variables, and 81% of the variance in the mean family age of angiosperm trees was explained by precipitation-related variables. Climatic conditions at the Last Glacial Maximum did not explain additional variation in mean family age after accounting for current environmental conditions.

Tectonic-driven climate change and the diversification of angiosperms

PubMed Central

Chaboureau, Anne-Claire; Sepulchre, Pierre; Donnadieu, Yannick; Franc, Alain

2014-01-01

In 1879, Charles Darwin characterized the sudden and unexplained rise of angiosperms during the Cretaceous as an “abominable mystery.” The diversification of this clade marked the beginning of a rapid transition among Mesozoic ecosystems and floras formerly dominated by ferns, conifers, and cycads. Although the role of environmental factors has been suggested [Coiffard C, Gómez B (2012) Geol Acta 10(2):181–188], Cretaceous global climate change has barely been considered as a contributor to angiosperm radiation, and focus was put on biotic factors to explain this transition. Here we use a fully coupled climate model driven by Mesozoic paleogeographic maps to quantify and discuss the impact of continental drift on angiosperm expansion and diversification. We show that the decrease of desertic belts between the Triassic and the Cretaceous and the subsequent onset of long-lasting humid conditions during the Late Cretaceous were driven by the breakup of Pangea and were contemporaneous with the first rise of angiosperm diversification. Positioning angiosperm-bearing fossil sites on our paleobioclimatic maps shows a strong match between the location of fossil-rich outcrops and temperate humid zones, indicating that climate change from arid to temperate dominance may have set the stage for the ecological expansion of flowering plants. PMID:25225405

Recurrent Loss of Specific Introns during Angiosperm Evolution

PubMed Central

Wang, Hao; Devos, Katrien M.; Bennetzen, Jeffrey L.

2014-01-01

Numerous instances of presence/absence variations for introns have been documented in eukaryotes, and some cases of recurrent loss of the same intron have been suggested. However, there has been no comprehensive or phylogenetically deep analysis of recurrent intron loss. Of 883 cases of intron presence/absence variation that we detected in five sequenced grass genomes, 93 were confirmed as recurrent losses and the rest could be explained by single losses (652) or single gains (118). No case of recurrent intron gain was observed. Deep phylogenetic analysis often indicated that apparent intron gains were actually numerous independent losses of the same intron. Recurrent loss exhibited extreme non-randomness, in that some introns were removed independently in many lineages. The two larger genomes, maize and sorghum, were found to have a higher rate of both recurrent loss and overall loss and/or gain than foxtail millet, rice or Brachypodium. Adjacent introns and small introns were found to be preferentially lost. Intron loss genes exhibited a high frequency of germ line or early embryogenesis expression. In addition, flanking exon A+T-richness and intron TG/CG ratios were higher in retained introns. This last result suggests that epigenetic status, as evidenced by a loss of methylated CG dinucleotides, may play a role in the process of intron loss. This study provides the first comprehensive analysis of recurrent intron loss, makes a series of novel findings on the patterns of recurrent intron loss during the evolution of the grass family, and provides insight into the molecular mechanism(s) underlying intron loss. PMID:25474210

Does polyploidy facilitate long-distance dispersal?

PubMed Central

Linder, H. Peter; Barker, Nigel P.

2014-01-01

Background and Aims The ability of plant lineages to reach all continents contributes substantially to their evolutionary success. This is exemplified by the Poaceae, one of the most successful angiosperm families, in which most higher taxa (tribes, subfamilies) have global distributions. Due to the old age of the ocean basins relative to the major angiosperm radiations, this is only possible by means of long-distance dispersal (LDD), yet the attributes of lineages with successful LDD remain obscure. Polyploid species are over-represented in invasive floras and in the previously glaciated Arctic regions, and often have wider ecological tolerances than diploids; thus polyploidy is a candidate attribute of successful LDD. Methods The link between polyploidy and LDD was explored in the globally distributed grass subfamily Danthonioideae. An almost completely sampled and well-resolved species-level phylogeny of the danthonioids was used, and the available cytological information was assembled. The cytological evolution in the clade was inferred using maximum likelihood (ML) as implemented in ChromEvol. The biogeographical evolution in the clade was reconstructed using ML and Bayesian approaches. Key Results Numerous increases in ploidy level are demonstrated. A Late Miocene–Pliocene cycle of polyploidy is associated with LDD, and in two cases (the Australian Rytidosperma and the American Danthonia) led to secondary polyploidy. While it is demonstrated that successful LDD is more likely in polyploid than in diploid lineages, a link between polyploidization events and LDD is not demonstrated. Conclusions The results suggest that polyploids are more successful at LDD than diploids, and that the frequent polyploidy in the grasses might have facilitated the extensive dispersal among continents in the family, thus contributing to their evolutionary success. PMID:24694830

Phylogenomics reveals an extensive history of genome duplication in diatoms (Bacillariophyta).

PubMed

Parks, Matthew B; Nakov, Teofil; Ruck, Elizabeth C; Wickett, Norman J; Alverson, Andrew J

2018-03-01

Diatoms are one of the most species-rich lineages of microbial eukaryotes. Similarities in clade age, species richness, and primary productivity motivate comparisons to angiosperms, whose genomes have been inordinately shaped by whole-genome duplication (WGD). WGDs have been linked to speciation, increased rates of lineage diversification, and identified as a principal driver of angiosperm evolution. We synthesized a large but scattered body of evidence that suggests polyploidy may be common in diatoms as well. We used gene counts, gene trees, and distributions of synonymous divergence to carry out a phylogenomic analysis of WGD across a diverse set of 37 diatom species. Several methods identified WGDs of varying age across diatoms. Determining the occurrence, exact number, and placement of events was greatly impacted by uncertainty in gene trees. WGDs inferred from synonymous divergence of paralogs varied depending on how redundancy in transcriptomes was assessed, gene families were assembled, and synonymous distances (Ks) were calculated. Our results highlighted a need for systematic evaluation of key methodological aspects of Ks-based approaches to WGD inference. Gene tree reconciliations supported allopolyploidy as the predominant mode of polyploid formation, with strong evidence for ancient allopolyploid events in the thalassiosiroid and pennate diatom clades. Our results suggest that WGD has played a major role in the evolution of diatom genomes. We outline challenges in reconstructing paleopolyploid events in diatoms that, together with these results, offer a framework for understanding the impact of genome duplication in a group that likely harbors substantial genomic diversity. © 2018 The Authors. American Journal of Botany is published by Wiley Periodicals, Inc. on behalf of the Botanical Society of America.

Community phylogenetics at the biogeographical scale: cold tolerance, niche conservatism and the structure of North American forests.

PubMed

Hawkins, Bradford A; Rueda, Marta; Rangel, Thiago F; Field, Richard; Diniz-Filho, José Alexandre F; Linder, Peter

2014-01-01

Aim The fossil record has led to a historical explanation for forest diversity gradients within the cool parts of the Northern Hemisphere, founded on a limited ability of woody angiosperm clades to adapt to mid-Tertiary cooling. We tested four predictions of how this should be manifested in the phylogenetic structure of 91,340 communities: (1) forests to the north should comprise species from younger clades (families) than forests to the south; (2) average cold tolerance at a local site should be associated with the mean family age (MFA) of species; (3) minimum temperature should account for MFA better than alternative environmental variables; and (4) traits associated with survival in cold climates should evolve under a niche conservatism constraint. Location The contiguous United States. Methods We extracted angiosperms from the US Forest Service's Forest Inventory and Analysis database. MFA was calculated by assigning age of the family to which each species belongs and averaging across the species in each community. We developed a phylogeny to identify phylogenetic signal in five traits: realized cold tolerance, seed size, seed dispersal mode, leaf phenology and height. Phylogenetic signal representation curves and phylogenetic generalized least squares were used to compare patterns of trait evolution against Brownian motion. Eleven predictors structured at broad or local scales were generated to explore relationships between environment and MFA using random forest and general linear models. Results Consistent with predictions, (1) southern communities comprise angiosperm species from older families than northern communities, (2) cold tolerance is the trait most strongly associated with local MFA, (3) minimum temperature in the coldest month is the environmental variable that best describes MFA, broad-scale variables being much stronger correlates than local-scale variables, and (4) the phylogenetic structures of cold tolerance and at least one other trait associated with survivorship in cold climates indicate niche conservatism. Main conclusions Tropical niche conservatism in the face of long-term climate change, probably initiated in the Late Cretaceous associated with the rise of the Rocky Mountains, is a strong driver of the phylogenetic structure of the angiosperm component of forest communities across the USA. However, local deterministic and/or stochastic processes account for perhaps a quarter of the variation in the MFA of local communities.

Fossil Leaves and Fossil Leaf n-Alkanes: Reconstructing the First Closed Canopied Rainforests

NASA Astrophysics Data System (ADS)

Graham, H. V.; Freeman, K. H.

2013-12-01

Although the age and location is disputed, the rise of the first closed-canopy forest is likely linked with the expansion of angiosperms in the late Cretacous or early Cenozoic. The carbon isotope 'canopy effect' reflects the extent of canopy closure, and is well documented in δ13C values of the leaves and leaf lipids in modern forests. To test the extent of canopy closure among the oldest documented angiosperm tropical forests, we analyzed isotopic characteristics of leaf fossils and leaf waxes from the Guaduas and Cerrejón Formations. The Guaduas Fm. (Maastrichtian) contains some of the earliest angiosperm fossils in the Neotropics, and both leaf morphology and pollen records at this site suggest an open-canopy structure. The Cerrejón Fm. (Paleocene) contains what are believed to be the first recorded fossil leaves from a closed-canopy forest. We analyzed the bulk carbon isotope content (δ13Cleaf) of 199 fossil leaves, as well as the n-alkane concentration and chain-length distribution, and δ13C of alkanes (δ13Clipid) of 73 fossil leaves and adjacent sediment samples. Fossil leaves are dominated by eudicots and include ten modern plant families (Apocynaceae, Bombaceae, Euphorbaceae, Fabaceae, Lauraceae, Malvaceae, Meliaceae, Menispermaceae, Moraceae, Sapotaceae). We interpreted extent of canopy coverage based on the range of δ13Cleaf values. The narrow range of δ13C values in leaves from the Guaduas Fm (2.7‰) is consistent with an open canopy. A significantly wider range in values (6.3‰) suggests a closed-canopy signature for site 0315 of the Cerrejón Fm,. In contrast, at Site 0318, a lacustrine deposit, leaves had a narrow range (3.3‰) in δ13C values, and this is not consistent with a closed-canopy, but is consistent with leaf assemblages from a forest edge. Leaves that accumulate in lake sediments tend to be biased toward plants living at the lake edge, which do not experience closed-canopy conditions, and do not express the isotopic characteristics associated with canopy effect. A biomass flux-weighted model of alkane chain-length distribution and δ13Cleaf indicate n-alkanes extracted from bulk rock are consistent with inputs integrated over time from plants represented by fossil leaves. In a modern rainforest, we found leaf lipid amounts markedly higher in the shaded and moist understory, consistent with studies that show alkanes proffer fungal protection. Shade tolerance is associated with higher plant orders and, consistent with this, literature data for modern plants from 30 plant orders shows alkane production in asterids and rosids is 2 to 3 times greater than in basal angiosperms or gymnosperms. The lower clades tend to contain greater amounts of terpenoids and novel benzylisoquinoline alkaloids, rather than alkanes. For our three fossil floras, alkane abundance is strongly influenced by depositional setting, with preservation best in the lacustrine setting. Within each site, abundance patterns are potentially influenced by both taxonomic affiliation and by canopy structure as measured by δ13Cleaf values, and such relationships shed light on the combined influences of plant evolution, canopy structure and the function of biochemical resources on the geochemical record of the first rainforests.

Production of n-alkyl lipids in living plants and implications for the geologic past

NASA Astrophysics Data System (ADS)

Diefendorf, Aaron F.; Freeman, Katherine H.; Wing, Scott L.; Graham, Heather V.

2011-12-01

Leaf waxes (i.e., n-alkyl lipids or n-alkanes) are land-plant biomarkers widely used to reconstruct changes in climate and the carbon isotopic composition of the atmosphere. There is little information available, however, on how the production of leaf waxes by different kinds of plants might influence the abundance and isotopic composition of n-alkanes in sedimentary archives. This lack of information increases uncertainty in interpreting n-alkyl lipid abundance and δ 13C signals in ancient settings. We provide here n-alkyl abundance distributions and carbon isotope fractionation data for deciduous and evergreen angiosperm and gymnosperm leaves from 46 tree species, representing 24 families. n-Alkane abundances are significantly higher in angiosperms than gymnosperms; many of the gymnosperm species investigated did not produce any n-alkanes. On average, deciduous angiosperms produce 200 times more n-alkanes than deciduous gymnosperms. Although differences between angiosperms and gymnosperms dominate the variance in n-alkane abundance, leaf life-span is also important, with higher n-alkane abundances in longer-lived leaves. n-Alkanol abundances covary with n-alkanes, but n-alkanoic acids have similar abundances across all plant groups. Isotopic fractionation between leaf tissue and individual alkanes ( ɛlipid) varies by as much as 10‰ among different chain lengths. Overall, ɛlipid values are slightly lower (-4.5‰) for angiosperm than for gymnosperm (-2.5‰) n-alkanes. Angiosperms commonly express slightly higher Δleaf (photosynthetic discrimination) relative to gymnosperms under similar growth conditions. As a result, angiosperm n-alkanes are expected to be generally 3-5‰ more depleted in 13C relative to gymnosperm alkanes for the same locality. Differences in n-alkane production indicate the biomarker record will largely (but not exclusively) reflect angiosperms if both groups were present, and also that evergreen plants will likely be overrepresented compared with deciduous ones. We apply our modern lipid abundance patterns and ɛlipid results to constrain the magnitude of the carbon isotope excursion (CIE) at the onset of the Paleocene-Eocene Thermal Maximum (55.8 Ma). When Bighorn Basin (WY) sediment n-alkanes are interpreted in context of floral changes and modern n-alkane production estimates for angiosperms and gymnosperms, the CIE is greater in magnitude (-5.6‰) by ˜1‰ compared to previous estimates that do not take into account n-alkane production.

Mitochondrial DNA suggests at least 11 origins of parasitism in angiosperms and reveals genomic chimerism in parasitic plants

PubMed Central

Barkman, Todd J; McNeal, Joel R; Lim, Seok-Hong; Coat, Gwen; Croom, Henrietta B; Young, Nelson D; dePamphilis, Claude W

2007-01-01

Background Some of the most difficult phylogenetic questions in evolutionary biology involve identification of the free-living relatives of parasitic organisms, particularly those of parasitic flowering plants. Consequently, the number of origins of parasitism and the phylogenetic distribution of the heterotrophic lifestyle among angiosperm lineages is unclear. Results Here we report the results of a phylogenetic analysis of 102 species of seed plants designed to infer the position of all haustorial parasitic angiosperm lineages using three mitochondrial genes: atp1, coxI, and matR. Overall, the mtDNA phylogeny agrees with independent studies in terms of non-parasitic plant relationships and reveals at least 11 independent origins of parasitism in angiosperms, eight of which consist entirely of holoparasitic species that lack photosynthetic ability. From these results, it can be inferred that modern-day parasites have disproportionately evolved in certain lineages and that the endoparasitic habit has arisen by convergence in four clades. In addition, reduced taxon, single gene analyses revealed multiple horizontal transfers of atp1 from host to parasite lineage, suggesting that parasites may be important vectors of horizontal gene transfer in angiosperms. Furthermore, in Pilostyles we show evidence for a recent host-to-parasite atp1 transfer based on a chimeric gene sequence that indicates multiple historical xenologous gene acquisitions have occurred in this endoparasite. Finally, the phylogenetic relationships inferred for parasites indicate that the origins of parasitism in angiosperms are strongly correlated with horizontal acquisitions of the invasive coxI group I intron. Conclusion Collectively, these results indicate that the parasitic lifestyle has arisen repeatedly in angiosperm evolutionary history and results in increasing parasite genomic chimerism over time. PMID:18154671

Physiological mechanisms drive differing foliar calcium content in ferns and angiosperms.

PubMed

Funk, Jennifer L; Amatangelo, Kathryn L

2013-09-01

Recent evidence points to ferns containing significantly lower contents of foliar calcium and other cations than angiosperms. This is especially true of more ancient 'non-polypod' fern lineages, which predate the diversification of angiosperms. Calcium is an important plant nutrient, the lack of which can potentially slow plant growth and litter decomposition, and alter soil invertebrate communities. The physiological mechanisms limiting foliar calcium (Ca) content in ferns are unknown. While there is a lot we do not know about Ca uptake and transport in plants, three physiological processes are likely to be important. We measured transpiration rate, cation exchange capacity, and leaching loss to determine which process most strongly regulates foliar Ca content in a range of fern and co-occurring understory angiosperm species from a montane Hawaiian rainforest. We found higher instantaneous and lifetime (corrected for leaf lifespan) transpiration rates in angiosperms relative to ferns. Ferns preferentially incorporated Ca into leaves relative to strontium, which suggests that root or stem cation exchange capacity differs between ferns and angiosperms, potentially affecting calcium transport in plants. There were no differences in foliar Ca leaching loss between groups. Among the physiological mechanisms measured, foliar Ca was most strongly correlated with leaf-level transpiration rate and leaf lifespan. This suggests that inter-specific differences in a leaf's lifetime transpiration may play a significant role in determining plant nutrition.

Mirolydidae, a new family of Jurassic pamphilioid sawfly (Hymenoptera) highlighting mosaic evolution of lower Hymenoptera.

PubMed

Wang, Mei; Rasnitsyn, Alexandr P; Yang, Zhongqi; Shih, Chungkun; Wang, Hongbin; Ren, Dong

2017-03-07

We describe Pamphilioidea: Mirolydidae Wang, Rasnitsyn et Ren, fam. n., containing Mirolyda hirta Wang, Rasnitsyn et Ren, gen. et sp. n., from the late Middle Jurassic Jiulongshan Formation of Daohugou, Inner Mongolia, China. The new taxon is characterized by unique forewing venation with the presence of forewing SC, 1-RS almost as long as 1-M, M + Cu straight, 2r-rs strongly reclival, and antenna with homonomous flagellum, revealing new and important details in antennal evolutionary transformations. Thus, M. hirta with a combination of primitive and more derived characters highlights its transitional state in the Pamphilioidea and complex mosaic evolution within Pamphilioidea in the late Middle Jurassic. The body of this species is densely covered with thin and long setae, suggesting its possible habit of visiting gymnosperm reproductive organs for pollen feeding and/or pollination during the late Middle Jurassic, much earlier than the appearance of angiosperm flowers.

Phylogeny and Expression Analyses Reveal Important Roles for Plant PKS III Family during the Conquest of Land by Plants and Angiosperm Diversification

PubMed Central

Xie, Lulu; Liu, Pingli; Zhu, Zhixin; Zhang, Shifan; Zhang, Shujiang; Li, Fei; Zhang, Hui; Li, Guoliang; Wei, Yunxiao; Sun, Rifei

2016-01-01

Polyketide synthases (PKSs) utilize the products of primary metabolism to synthesize a wide array of secondary metabolites in both prokaryotic and eukaryotic organisms. PKSs can be grouped into three distinct classes, types I, II, and III, based on enzyme structure, substrate specificity, and catalytic mechanisms. The type III PKS enzymes function as homodimers, and are the only class of PKS that do not require acyl carrier protein. Plant type III PKS enzymes, also known as chalcone synthase (CHS)-like enzymes, are of particular interest due to their functional diversity. In this study, we mined type III PKS gene sequences from the genomes of six aquatic algae and 25 land plants (1 bryophyte, 1 lycophyte, 2 basal angiosperms, 16 core eudicots, and 5 monocots). PKS III sequences were found relatively conserved in all embryophytes, but not exist in algae. We also examined gene expression patterns by analyzing available transcriptome data, and identified potential cis-regulatory elements in upstream sequences. Phylogenetic trees of dicots angiosperms showed that plant type III PKS proteins fall into three clades. Clade A contains CHS/STS-type enzymes coding genes with diverse transcriptional expression patterns and enzymatic functions, while clade B is further divided into subclades b1 and b2, which consist of anther-specific CHS-like enzymes. Differentiation regions, such as amino acids 196-207 between clades A and B, and predicted positive selected sites within α-helixes in late appeared branches of clade A, account for the major diversification in substrate choice and catalytic reaction. The integrity and location of conserved cis-elements containing MYB and bHLH binding sites can affect transcription levels. Potential binding sites for transcription factors such as WRKY, SPL, or AP2/EREBP may contribute to tissue- or taxon-specific differences in gene expression. Our data shows that gene duplications and functional diversification of plant type III PKS enzymes played a critical role in the ancient conquest of the land by early plants and angiosperm diversification. PMID:27625671

Buffering of crucial functions by paleologous duplicated genes may contribute cyclicality to angiosperm genome duplication.

PubMed

Chapman, Brad A; Bowers, John E; Feltus, Frank A; Paterson, Andrew H

2006-02-21

Genome duplication followed by massive gene loss has permanently shaped the genomes of many higher eukaryotes, particularly angiosperms. It has long been believed that a primary advantage of genome duplication is the opportunity for the evolution of genes with new functions by modification of duplicated genes. If so, then patterns of genetic diversity among strains within taxa might reveal footprints of selection that are consistent with this advantage. Contrary to classical predictions that duplicated genes may be relatively free to acquire unique functionality, we find among both Arabidopsis ecotypes and Oryza subspecies that SNPs encode less radical amino acid changes in genes for which there exists a duplicated copy at a "paleologous" locus than in "singleton" genes. Preferential retention of duplicated genes encoding long complex proteins and their unexpectedly slow divergence (perhaps because of homogenization) suggest that a primary advantage of retaining duplicated paleologs may be the buffering of crucial functions. Functional buffering and functional divergence may represent extremes in the spectrum of duplicated gene fates. Functional buffering may be especially important during "genomic turmoil" immediately after genome duplication but continues to act approximately 60 million years later, and its gradual deterioration may contribute cyclicality to genome duplication in some lineages.

Buffering of crucial functions by paleologous duplicated genes may contribute cyclicality to angiosperm genome duplication

PubMed Central

Chapman, Brad A.; Bowers, John E.; Feltus, Frank A.; Paterson, Andrew H.

2006-01-01

Genome duplication followed by massive gene loss has permanently shaped the genomes of many higher eukaryotes, particularly angiosperms. It has long been believed that a primary advantage of genome duplication is the opportunity for the evolution of genes with new functions by modification of duplicated genes. If so, then patterns of genetic diversity among strains within taxa might reveal footprints of selection that are consistent with this advantage. Contrary to classical predictions that duplicated genes may be relatively free to acquire unique functionality, we find among both Arabidopsis ecotypes and Oryza subspecies that SNPs encode less radical amino acid changes in genes for which there exists a duplicated copy at a “paleologous” locus than in “singleton” genes. Preferential retention of duplicated genes encoding long complex proteins and their unexpectedly slow divergence (perhaps because of homogenization) suggest that a primary advantage of retaining duplicated paleologs may be the buffering of crucial functions. Functional buffering and functional divergence may represent extremes in the spectrum of duplicated gene fates. Functional buffering may be especially important during “genomic turmoil” immediately after genome duplication but continues to act ≈60 million years later, and its gradual deterioration may contribute cyclicality to genome duplication in some lineages. PMID:16467140

New evidence for mammaliaform ear evolution and feeding adaptation in a Jurassic ecosystem

NASA Astrophysics Data System (ADS)

Luo, Zhe-Xi; Meng, Qing-Jin; Grossnickle, David M.; Liu, Di; Neander, April I.; Zhang, Yu-Guang; Ji, Qiang

2017-08-01

Stem mammaliaforms are forerunners to modern mammals, and they achieved considerable ecomorphological diversity in their own right. Recent discoveries suggest that eleutherodontids, a subclade of Haramiyida, were more species-rich during the Jurassic period in Asia than previously recognized. Here we report a new Jurassic eleutherodontid mammaliaform with an unusual mosaic of highly specialized characteristics, and the results of phylogenetic analyses that support the hypothesis that haramiyidans are stem mammaliaforms. The new fossil shows fossilized skin membranes that are interpreted to be for gliding and a mandibular middle ear with a unique character combination previously unknown in mammaliaforms. Incisor replacement is prolonged until well after molars are fully erupted, a timing pattern unique to most other mammaliaforms. In situ molar occlusion and a functional analysis reveal a new mode of dental occlusion: dual mortar-pestle occlusion of opposing upper and lower molars, probably for dual crushing and grinding. This suggests that eleutherodontids are herbivorous, and probably specialized for granivory or feeding on soft plant tissues. The inferred dietary adaptation of eleutherodontid gliders represents a remarkable evolutionary convergence with herbivorous gliders in Theria. These Jurassic fossils represent volant, herbivorous stem mammaliaforms associated with pre-angiosperm plants that appear long before the later, iterative associations between angiosperm plants and volant herbivores in various therian clades.

New evidence for mammaliaform ear evolution and feeding adaptation in a Jurassic ecosystem.

PubMed

Luo, Zhe-Xi; Meng, Qing-Jin; Grossnickle, David M; Liu, Di; Neander, April I; Zhang, Yu-Guang; Ji, Qiang

2017-08-17

Stem mammaliaforms are forerunners to modern mammals, and they achieved considerable ecomorphological diversity in their own right. Recent discoveries suggest that eleutherodontids, a subclade of Haramiyida, were more species-rich during the Jurassic period in Asia than previously recognized. Here we report a new Jurassic eleutherodontid mammaliaform with an unusual mosaic of highly specialized characteristics, and the results of phylogenetic analyses that support the hypothesis that haramiyidans are stem mammaliaforms. The new fossil shows fossilized skin membranes that are interpreted to be for gliding and a mandibular middle ear with a unique character combination previously unknown in mammaliaforms. Incisor replacement is prolonged until well after molars are fully erupted, a timing pattern unique to most other mammaliaforms. In situ molar occlusion and a functional analysis reveal a new mode of dental occlusion: dual mortar-pestle occlusion of opposing upper and lower molars, probably for dual crushing and grinding. This suggests that eleutherodontids are herbivorous, and probably specialized for granivory or feeding on soft plant tissues. The inferred dietary adaptation of eleutherodontid gliders represents a remarkable evolutionary convergence with herbivorous gliders in Theria. These Jurassic fossils represent volant, herbivorous stem mammaliaforms associated with pre-angiosperm plants that appear long before the later, iterative associations between angiosperm plants and volant herbivores in various therian clades.

Chloroplast and nuclear gene sequences indicate late Pennsylvanian time for the last common ancestor of extant seed plants.

PubMed Central

Savard, L; Li, P; Strauss, S H; Chase, M W; Michaud, M; Bousquet, J

1994-01-01

We have estimated the time for the last common ancestor of extant seed plants by using molecular clocks constructed from the sequences of the chloroplastic gene coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) and the nuclear gene coding for the small subunit of rRNA (Rrn18). Phylogenetic analyses of nucleotide sequences indicated that the earliest divergence of extant seed plants is likely represented by a split between conifer-cycad and angiosperm lineages. Relative-rate tests were used to assess homogeneity of substitution rates among lineages, and annual angiosperms were found to evolve at a faster rate than other taxa for rbcL and, thus, these sequences were excluded from construction of molecular clocks. Five distinct molecular clocks were calibrated using substitution rates for the two genes and four divergence times based on fossil and published molecular clock estimates. The five estimated times for the last common ancestor of extant seed plants were in agreement with one another, with an average of 285 million years and a range of 275-290 million years. This implies a substantially more recent ancestor of all extant seed plants than suggested by some theories of plant evolution. PMID:8197201

Endosperm and Nucellus Develop Antagonistically in Arabidopsis Seeds

PubMed Central

Xu, Wenjia; Coen, Olivier; Pechoux, Christine; Magnani, Enrico

2016-01-01

In angiosperms, seed architecture is shaped by the coordinated development of three genetically different components: embryo, endosperm, and maternal tissues. The relative contribution of these tissues to seed mass and nutrient storage varies considerably among species. The development of embryo, endosperm, or nucellus maternal tissue as primary storage compartments defines three main typologies of seed architecture. It is still debated whether the ancestral angiosperm seed accumulated nutrients in the endosperm or the nucellus. During evolution, plants shifted repeatedly between these two storage strategies through molecular mechanisms that are largely unknown. Here, we characterize the regulatory pathway underlying nucellus and endosperm tissue partitioning in Arabidopsis thaliana. We show that Polycomb-group proteins repress nucellus degeneration before fertilization. A signal initiated in the endosperm by the AGAMOUS-LIKE62 MADS box transcription factor relieves this Polycomb-mediated repression and therefore allows nucellus degeneration. Further downstream in the pathway, the TRANSPARENT TESTA16 (TT16) and GORDITA MADS box transcription factors promote nucellus degeneration. Moreover, we demonstrate that TT16 mediates the crosstalk between nucellus and seed coat maternal tissues. Finally, we characterize the nucellus cell death program and its feedback role in timing endosperm development. Altogether, our data reveal the antagonistic development of nucellus and endosperm, in coordination with seed coat differentiation. PMID:27233529

The betrayed thief – the extraordinary strategy of Aristolochia rotunda to deceive its pollinators

PubMed Central

Oelschlägel, Birgit; Nuss, Matthias; von Tschirnhaus, Michael; Pätzold, Claudia; Neinhuis, Christoph; Dötterl, Stefan; Wanke, Stefan

2015-01-01

Pollination of several angiosperms is based on deceit. In such systems, the flowers advertise a reward that ultimately is not provided. We report on a previously unknown pollination/mimicry system discovered in deceptive Aristolochia rotunda (Aristolochiaceae). Pollinators were collected in the natural habitat and identified. Flower scent and the volatiles of insects (models) potentially mimicked were analyzed by chemical analytical techniques. Electrophysiological and behavioral tests on the pollinators identified the components that mediate the plant–pollinator interaction and revealed the model of the mimicry system. The main pollinators of A. rotunda were female Chloropidae. They are food thieves that feed on secretions of true bugs (Miridae) while these are eaten by arthropod predators. Freshly killed mirids and Aristolochia flowers released the same scent components that chloropids use to find their food sources. Aristolochia exploits these components to deceive their chloropid pollinators. Aristolochia and other trap flowers were believed to lure saprophilous flies and mimic brood sites of pollinators. We demonstrate for A. rotunda, and hypothesize for other deceptive angiosperms, the evolution of a different, kleptomyiophilous pollination strategy. It involves scent mimicry and the exploitation of kleptoparasitic flies as pollinators. Our findings suggest a reconsideration of plants assumed to show sapromyiophilous pollination. PMID:25488155

Comparative analysis of cation/proton antiporter superfamily in plants.

PubMed

Ye, Chu-Yu; Yang, Xiaohan; Xia, Xinli; Yin, Weilun

2013-06-01

The cation/proton antiporter superfamily is associated with the transport of monovalent cations across membranes. This superfamily was annotated in the Arabidopsis genome and some members were functionally characterized. In the present study, a systematic analysis of the cation/proton antiporter genes in diverse plant species was reported. We identified 240 cation/proton antiporters in alga, moss, and angiosperm. A phylogenetic tree was constructed showing these 240 members are separated into three families, i.e., Na(+)/H(+) exchangers, K(+) efflux antiporters, and cation/H(+) exchangers. Our analysis revealed that tandem and/or segmental duplications contribute to the expansion of cation/H(+) exchangers in the examined angiosperm species. Sliding window analysis of the nonsynonymous/synonymous substitution ratios showed some differences in the evolutionary fate of cation/proton antiporter paralogs. Furthermore, we identified over-represented motifs among these 240 proteins and found most motifs are family specific, demonstrating diverse evolution of the cation/proton antiporters among three families. In addition, we investigated the co-expressed genes of the cation/proton antiporters in Arabidopsis thaliana. The results showed some biological processes are enriched in the co-expressed genes, suggesting the cation/proton antiporters may be involved in these biological processes. Taken together, this study furthers our knowledge on cation/proton antiporters in plants. Copyright © 2013 Elsevier B.V. All rights reserved.

The betrayed thief - the extraordinary strategy of Aristolochia rotunda to deceive its pollinators.

PubMed

Oelschlägel, Birgit; Nuss, Matthias; von Tschirnhaus, Michael; Pätzold, Claudia; Neinhuis, Christoph; Dötterl, Stefan; Wanke, Stefan

2015-04-01

Pollination of several angiosperms is based on deceit. In such systems, the flowers advertise a reward that ultimately is not provided. We report on a previously unknown pollination/mimicry system discovered in deceptive Aristolochia rotunda (Aristolochiaceae). Pollinators were collected in the natural habitat and identified. Flower scent and the volatiles of insects (models) potentially mimicked were analyzed by chemical analytical techniques. Electrophysiological and behavioral tests on the pollinators identified the components that mediate the plant-pollinator interaction and revealed the model of the mimicry system. The main pollinators of A. rotunda were female Chloropidae. They are food thieves that feed on secretions of true bugs (Miridae) while these are eaten by arthropod predators. Freshly killed mirids and Aristolochia flowers released the same scent components that chloropids use to find their food sources. Aristolochia exploits these components to deceive their chloropid pollinators. Aristolochia and other trap flowers were believed to lure saprophilous flies and mimic brood sites of pollinators. We demonstrate for A. rotunda, and hypothesize for other deceptive angiosperms, the evolution of a different, kleptomyiophilous pollination strategy. It involves scent mimicry and the exploitation of kleptoparasitic flies as pollinators. Our findings suggest a reconsideration of plants assumed to show sapromyiophilous pollination. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

The phylogenetic distribution of extrafloral nectaries in plants

PubMed Central

Weber, Marjorie G.; Keeler, Kathleen H.

2013-01-01

Background and Aims Understanding the evolutionary patterns of ecologically relevant traits is a central goal in plant biology. However, for most important traits, we lack the comprehensive understanding of their taxonomic distribution needed to evaluate their evolutionary mode and tempo across the tree of life. Here we evaluate the broad phylogenetic patterns of a common plant-defence trait found across vascular plants: extrafloral nectaries (EFNs), plant glands that secrete nectar and are located outside the flower. EFNs typically defend plants indirectly by attracting invertebrate predators who reduce herbivory. Methods Records of EFNs published over the last 135 years were compiled. After accounting for changes in taxonomy, phylogenetic comparative methods were used to evaluate patterns of EFN evolution, using a phylogeny of over 55 000 species of vascular plants. Using comparisons of parametric and non-parametric models, the true number of species with EFNs likely to exist beyond the current list was estimated. Key Results To date, EFNs have been reported in 3941 species representing 745 genera in 108 families, about 1–2 % of vascular plant species and approx. 21 % of families. They are found in 33 of 65 angiosperm orders. Foliar nectaries are known in four of 36 fern families. Extrafloral nectaries are unknown in early angiosperms, magnoliids and gymnosperms. They occur throughout monocotyledons, yet most EFNs are found within eudicots, with the bulk of species with EFNs being rosids. Phylogenetic analyses strongly support the repeated gain and loss of EFNs across plant clades, especially in more derived dicot families, and suggest that EFNs are found in a minimum of 457 independent lineages. However, model selection methods estimate that the number of unreported cases of EFNs may be as high as the number of species already reported. Conclusions EFNs are widespread and evolutionarily labile traits that have repeatedly evolved a remarkable number of times in vascular plants. Our current understanding of the phylogenetic patterns of EFNs makes them powerful candidates for future work exploring the drivers of their evolutionary origins, shifts, and losses. PMID:23087129

Evidence for the involvement of Globosa-like gene duplications and expression divergence in the evolution of floral morphology in the Zingiberales.

PubMed

Bartlett, Madelaine E; Specht, Chelsea D

2010-07-01

*The MADS box transcription factor family has long been identified as an important contributor to the control of floral development. It is often hypothesized that the evolution of floral development across angiosperms and within specific lineages may occur as a result of duplication, functional diversification, and changes in regulation of MADS box genes. Here we examine the role of Globosa (GLO)-like genes, members of the B-class MADS box gene lineage, in the evolution of floral development within the monocot order Zingiberales. *We assessed changes in perianth and stamen whorl morphology in a phylogenetic framework. We identified GLO homologs (ZinGLO1-4) from 50 Zingiberales species and investigated the evolution of this gene lineage. Expression of two GLO homologs was assessed in Costus spicatus and Musa basjoo. *Based on the phylogenetic data and expression results, we propose several family-specific losses and gains of GLO homologs that appear to be associated with key morphological changes. The GLO-like gene lineage has diversified concomitant with the evolution of the dimorphic perianth and the staminodial labellum. *Duplications and expression divergence within the GLO-like gene lineage may have played a role in floral diversification in the Zingiberales.

Floral development at multiple spatial scales in Polygonum jucundum (Polygonaceae), a distylous species with broadly open flowers.

PubMed

Huang, Lan-Jie; Fu, Wen-Long; Wang, Xiao-Fan

2014-01-01

Distyly, a special polymorph, has evolved in many groups of angiosperms and has attracted attention since Darwin's time. Development studies on distylous taxa have helped us to understand the evolutionary process of this polymorph, but most of these studies focus on species with narrowly tubular corolla. Here, we studied the floral development of Polygonum jucundum, a distylous species with broadly open flowers, at multiple spatial scales. Results showed that the difference in stigma height between flowers of the two morphs was caused by differences in style growth throughout the entire floral development process. The observed difference in anther heights between the two morphs was because the filaments grew faster in short-styled (SS) than in long-styled (LS) flowers in the later stages of floral development. In addition, the longer styles in LS flowers than in SS flowers was because of faster cell division in the early stages of floral development. However, SS flowers had longer filaments than LS flowers primarily because of greater cell elongation. These results indicate that floral development in P. jucundum differs from that of distylous taxa with floral tubes shown in previous studies. Further, we conclude that the presence of distyly in species with open flowers is a result of convergent evolution.

Multiple Origins and Nested Cycles of Hybridization Result in High Tetraploid Diversity in the Monocot Prospero.

PubMed

Jang, Tae-Soo; Parker, John S; Emadzade, Khatere; Temsch, Eva M; Leitch, Andrew R; Weiss-Schneeweiss, Hanna

2018-01-01

Polyploidy is a major driving force in angiosperm evolution, but our understanding of establishment and early diversification processes following allo- vs. auto-polyploidy is limited. An excellent system to address such questions is the monocot plant Prospero autumnale , as it comprises several genomically and chromosomally distinct diploid cytotypes and their auto- and allotetraploid derivatives. To infer origins and evolutionary trajectories of the tetraploids, we use genome size data, in situ hybridization with parental genomic DNAs and specific probes (satDNA, rDNAs), as well as molecular-phylogenetic analyses. Thus, we demonstrate that an astounding range of allotetraploid lineages has been formed recurrently by chromosomal re-patterning, interactions of chromosomally variable parental genomes and nested cycles of extensive hybridization, whereas autotetraploids have originated at least twice and are cytologically stable. During the recurrent formation and establishment across wide geographic areas hybridization in some populations could have inhibited lineage diversification and nascent speciation of such a hybrid swarm. However, cytotypes that became fixed in populations enhanced the potential for species diversification, possibly exploiting the extended allelic base, and fixed heterozygosity that polyploidy confers. The time required for polyploid cytotype fixation may in part reflect the lag phase reported for polyploids between their formation and species diversification.

Selection of sporophytic and gametophytic self-incompatibility in the absence of a superlocus.

PubMed

Schoen, Daniel J; Roda, Megan J

2016-06-01

Self-incompatibility (SI) is a complex trait that enforces outcrossing in plant populations. SI generally involves tight linkage of genes coding for the proteins that underlie self-pollen detection and pollen identity specification. Here, we develop two-locus genetic models to address the question of whether sporophytic SI (SSI) and gametophytic SI (GSI) can invade populations of self-compatible plants when there is no linkage or weak linkage of the underlying pollen detection and identity genes (i.e., no S-locus supergene). The models assume that SI evolves as a result of exaptation of genes formerly involved in functions other than SI. Model analysis reveals that SSI and GSI can invade populations even when the underlying genes are loosely linked, provided that inbreeding depression and selfing rate are sufficiently high. Reducing recombination between these genes makes conditions for invasion more lenient. These results can help account for multiple, independent evolution of SI systems as seems to have occurred in the angiosperms. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Ants sow the seeds of global diversification in flowering plants.

PubMed

Lengyel, Szabolcs; Gove, Aaron D; Latimer, Andrew M; Majer, Jonathan D; Dunn, Robert R

2009-01-01

The extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000-300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory) may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances. Using the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions. Myrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on large-scale diversification.

Phylogenetic assemblage structure of North American trees is more strongly shaped by glacial-interglacial climate variability in gymnosperms than in angiosperms.

PubMed

Ma, Ziyu; Sandel, Brody; Svenning, Jens-Christian

2016-05-01

How fast does biodiversity respond to climate change? The relationship of past and current climate with phylogenetic assemblage structure helps us to understand this question. Studies of angiosperm tree diversity in North America have already suggested effects of current water-energy balance and tropical niche conservatism. However, the role of glacial-interglacial climate variability remains to be determined, and little is known about any of these relationships for gymnosperms. Moreover, phylogenetic endemism, the concentration of unique lineages in restricted ranges, may also be related to glacial-interglacial climate variability and needs more attention. We used a refined phylogeny of both angiosperms and gymnosperms to map phylogenetic diversity, clustering and endemism of North American trees in 100-km grid cells, and climate change velocity since Last Glacial Maximum together with postglacial accessibility to recolonization to quantify glacial-interglacial climate variability. We found: (1) Current climate is the dominant factor explaining the overall patterns, with more clustered angiosperm assemblages toward lower temperature, consistent with tropical niche conservatism. (2) Long-term climate stability is associated with higher angiosperm endemism, while higher postglacial accessibility is linked to to more phylogenetic clustering and endemism in gymnosperms. (3) Factors linked to glacial-interglacial climate change have stronger effects on gymnosperms than on angiosperms. These results suggest that paleoclimate legacies supplement current climate in shaping phylogenetic patterns in North American trees, and especially so for gymnosperms.

Evolution of RLSB, a nuclear-encoded S1 domain RNA binding protein associated with post-transcriptional regulation of plastid-encoded rbcL mRNA in vascular plants.

PubMed

Yerramsetty, Pradeep; Stata, Matt; Siford, Rebecca; Sage, Tammy L; Sage, Rowan F; Wong, Gane Ka-Shu; Albert, Victor A; Berry, James O

2016-06-29

RLSB, an S-1 domain RNA binding protein of Arabidopsis, selectively binds rbcL mRNA and co-localizes with Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) within chloroplasts of C3 and C4 plants. Previous studies using both Arabidopsis (C3) and maize (C4) suggest RLSB homologs are post-transcriptional regulators of plastid-encoded rbcL mRNA. While RLSB accumulates in all Arabidopsis leaf chlorenchyma cells, in C4 leaves RLSB-like proteins accumulate only within Rubisco-containing bundle sheath chloroplasts of Kranz-type species, and only within central compartment chloroplasts in the single cell C4 plant Bienertia. Our recent evidence implicates this mRNA binding protein as a primary determinant of rbcL expression, cellular localization/compartmentalization, and photosynthetic function in all multicellular green plants. This study addresses the hypothesis that RLSB is a highly conserved Rubisco regulatory factor that occurs in the chloroplasts all higher plants. Phylogenetic analysis has identified RLSB orthologs and paralogs in all major plant groups, from ancient liverworts to recent angiosperms. RLSB homologs were also identified in algae of the division Charophyta, a lineage closely related to land plants. RLSB-like sequences were not identified in any other algae, suggesting that it may be specific to the evolutionary line leading to land plants. The RLSB family occurs in single copy across most angiosperms, although a few species with two copies were identified, seemingly randomly distributed throughout the various taxa, although perhaps correlating in some cases with known ancient whole genome duplications. Monocots of the order Poales (Poaceae and Cyperaceae) were found to contain two copies, designated here as RLSB-a and RLSB-b, with only RLSB-a implicated in the regulation of rbcL across the maize developmental gradient. Analysis of microsynteny in angiosperms revealed high levels of conservation across eudicot species and for both paralogs in grasses, highlighting the possible importance of maintaining this gene and its surrounding genomic regions. Findings presented here indicate that the RLSB family originated as a unique gene in land plant evolution, perhaps in the common ancestor of charophytes and higher plants. Purifying selection has maintained this as a highly conserved single- or two-copy gene across most extant species, with several conserved gene duplications. Together with previous findings, this study suggests that RLSB has been sustained as an important regulatory protein throughout the course of land plant evolution. While only RLSB-a has been directly implicated in rbcL regulation in maize, RLSB-b could have an overlapping function in the co-regulation of rbcL, or may have diverged as a regulator of one or more other plastid-encoded mRNAs. This analysis confirms that RLSB is an important and unique photosynthetic regulatory protein that has been continuously expressed in land plants as they emerged and diversified from their ancient common ancestor.

A survey of nuclear ribosomal internal transcribed spacer substitution rates across angiosperms: an approximate molecular clock with life history effects

PubMed Central

Kay, Kathleen M; Whittall, Justen B; Hodges, Scott A

2006-01-01

Background A full understanding of the patterns and processes of biological diversification requires the dating of evolutionary events, yet the fossil record is inadequate for most lineages under study. Alternatively, a molecular clock approach, in which DNA or amino acid substitution rates are calibrated with fossils or geological/climatic events, can provide indirect estimates of clade ages and diversification rates. The utility of this approach depends on the rate constancy of molecular evolution at a genetic locus across time and across lineages. Although the nuclear ribosomal internal transcribed spacer region (nrITS) is increasingly being used to infer clade ages in plants, little is known about the sources or magnitude of variation in its substitution rate. Here, we systematically review the literature to assess substitution rate variation in nrITS among angiosperms, and we evaluate possible correlates of the variation. Results We summarize 28 independently calibrated nrITS substitution rates ranging from 0.38 × 10-9 to 8.34 × 10-9 substitutions/site/yr. We find that herbaceous lineages have substitution rates almost twice as high as woody plants, on average. We do not find any among-lineage phylogenetic constraint to the rates, or any effect of the type of calibration used. Within life history categories, both the magnitude of the rates and the variance among rates tend to decrease with calibration age. Conclusion Angiosperm nrITS substitution rates vary by approximately an order of magnitude, and some of this variation can be attributed to life history categories. We make cautious recommendations for the use of nrITS as an approximate plant molecular clock, including an outline of more appropriate phylogenetic methodology and caveats against over interpretation of results. We also suggest that for lineages with independent calibrations, much of the variation in nrITS substitution rates may come from uncertainty in calibration date estimates, highlighting the importance of accurate and/or multiple calibration dates. PMID:16638138

Bilabiate Flowers: The Ultimate Response to Bees?

PubMed Central

Westerkamp, Christian; Claßen-Bockhoff, Regine

2007-01-01

Background and Aims Bilabiate flowers have evolved in many lineages of the angiosperms, thus representing a convincing example of parallel evolution. Similar to keel blossoms, they have obviously evolved in order to protect pollen against pollen-collecting bees. Although many examples are known, a comprehensive survey on floral diversity and functional constraints of bilabiate flowers is lacking. Here, the concept is widened and described as a general pattern. Methods The present paper is a conceptional review including personal observations of the authors. To form a survey on the diversity of bilabiate blossoms, a search was made for examples across the angiosperms and these were combined with personal observations collected during the last 25 years, coupled with knowledge from the literature. New functional terms are introduced that are independent of morphological and taxonomic associations. Key Results Bilabiate constructions occur in at least 38 angiosperm families. They are characterized by dorsiventral organization and dorsal pollen transfer. They are most often realised on the level of a single flower, but may also be present in an inflorescence or as part of a so-called ‘walk-around flower’. Interestingly, in functional terms all nototribic blossoms represent bilabiate constructions. The great majority of specialized bee-flowers can thus be included under bilabiate and keel blossoms. The syndrome introduced here, however, also paves the way for the inclusion of larger animals such as birds and bats. The most important evolutionary trends appear to be in the saving of pollen and the precision of its transfer. With special reference to the Lamiales, selected examples of bilabiate flowers are presented and their functional significance is discussed. Conclusions Bilabiate blossoms protect their pollen against pollen-collecting bees and at the same time render their pollination more precisely. The huge diversity of realised forms indicate the high selection pressure towards the bilabiate syndrome. As bees are very inventive, however, bilabiate constructions will not represent the ultimate response to bees. PMID:17652341

Nested radiations and the pulse of angiosperm diversification: increased diversification rates often follow whole genome duplications.

PubMed

Tank, David C; Eastman, Jonathan M; Pennell, Matthew W; Soltis, Pamela S; Soltis, Douglas E; Hinchliff, Cody E; Brown, Joseph W; Sessa, Emily B; Harmon, Luke J

2015-07-01

Our growing understanding of the plant tree of life provides a novel opportunity to uncover the major drivers of angiosperm diversity. Using a time-calibrated phylogeny, we characterized hot and cold spots of lineage diversification across the angiosperm tree of life by modeling evolutionary diversification using stepwise AIC (MEDUSA). We also tested the whole-genome duplication (WGD) radiation lag-time model, which postulates that increases in diversification tend to lag behind established WGD events. Diversification rates have been incredibly heterogeneous throughout the evolutionary history of angiosperms and reveal a pattern of 'nested radiations' - increases in net diversification nested within other radiations. This pattern in turn generates a negative relationship between clade age and diversity across both families and orders. We suggest that stochastically changing diversification rates across the phylogeny explain these patterns. Finally, we demonstrate significant statistical support for the WGD radiation lag-time model. Across angiosperms, nested shifts in diversification led to an overall increasing rate of net diversification and declining relative extinction rates through time. These diversification shifts are only rarely perfectly associated with WGD events, but commonly follow them after a lag period. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Pollinator-driven ecological speciation in plants: new evidence and future perspectives

PubMed Central

Van der Niet, Timotheüs; Peakall, Rod; Johnson, Steven D.

2014-01-01

Background The hypothesis that pollinators have been important drivers of angiosperm diversity dates back to Darwin, and remains an important research topic today. Mounting evidence indicates that pollinators have the potential to drive diversification at several different stages of the evolutionary process. Microevolutionary studies have provided evidence for pollinator-mediated floral adaptation, while macroevolutionary evidence supports a general pattern of pollinator-driven diversification of angiosperms. However, the overarching issue of whether, and how, shifts in pollination system drive plant speciation represents a critical gap in knowledge. Bridging this gap is crucial to fully understand whether pollinator-driven microevolution accounts for the observed macroevolutionary patterns. Testable predictions about pollinator-driven speciation can be derived from the theory of ecological speciation, according to which adaptation (microevolution) and speciation (macroevolution) are directly linked. This theory is a particularly suitable framework for evaluating evidence for the processes underlying shifts in pollination systems and their potential consequences for the evolution of reproductive isolation and speciation. Scope This Viewpoint paper focuses on evidence for the four components of ecological speciation in the context of plant-pollinator interactions, namely (1) the role of pollinators as selective agents, (2) floral trait divergence, including the evolution of ‘pollination ecotypes‘, (3) the geographical context of selection on floral traits, and (4) the role of pollinators in the evolution of reproductive isolation. This Viewpoint also serves as the introduction to a Special Issue on Pollinator-Driven Speciation in Plants. The 13 papers in this Special Issue range from microevolutionary studies of ecotypes to macroevolutionary studies of historical ecological shifts, and span a wide range of geographical areas and plant families. These studies further illustrate innovative experimental approaches, and they employ modern tools in genetics and floral trait quantification. Future advances to the field require better quantification of selection through male fitness and pollinator isolation, for instance by exploiting next-generation sequencing technologies. By combining these new tools with strategically chosen study systems, and smart experimental design, we predict that examples of pollinator-driven speciation will be among the most widespread and compelling of all cases of ecological speciation. PMID:24418954

Molecular evolution of psbA gene in ferns: unraveling selective pressure and co-evolutionary pattern

PubMed Central

2012-01-01

Background The photosynthetic oxygen-evolving photo system II (PS II) produces almost the entire oxygen in the atmosphere. This unique biochemical system comprises a functional core complex that is encoded by psbA and other genes. Unraveling the evolutionary dynamics of this gene is of particular interest owing to its direct role in oxygen production. psbA underwent gene duplication in leptosporangiates, in which both copies have been preserved since. Because gene duplication is often followed by the non-fictionalization of one of the copies and its subsequent erosion, preservation of both psbA copies pinpoint functional or regulatory specialization events. The aim of this study was to investigate the molecular evolution of psbA among fern lineages. Results We sequenced psbA , which encodes D1 protein in the core complex of PSII, in 20 species representing 8 orders of extant ferns; then we searched for selection and convolution signatures in psbA across the 11 fern orders. Collectively, our results indicate that: (1) selective constraints among D1 protein relaxed after the duplication in 4 leptosporangiate orders; (2) a handful positively selected codons were detected within species of single copy psbA, but none in duplicated ones; (3) a few sites among D1 protein were involved in co-evolution process which may intimate significant functional/structural communications between them. Conclusions The strong competition between ferns and angiosperms for light may have been the main cause for a continuous fixation of adaptive amino acid changes in psbA , in particular after its duplication. Alternatively, a single psbA copy may have undergone bursts of adaptive changes at the molecular level to overcome angiosperms competition. The strong signature of positive Darwinian selection in a major part of D1 protein is testament to this. At the same time, species own two psbA copies hardly have positive selection signals among the D1 protein coding sequences. In this study, eleven co-evolving sites have been detected via different molecules, which may be more important than others. PMID:22899792

Divergent scaling of respiration rates to nitrogen and phosphorus across four woody seedlings between different growing seasons.

PubMed

Fan, Ruirui; Sun, Jun; Yang, Fuchun; Li, Man; Zheng, Yuan; Zhong, Quanlin; Cheng, Dongliang

2017-11-01

Empirical studies indicate that the exponents governing the scaling of plant respiration rates ( R ) with respect to biomass ( M ) numerically vary between three-fourth for adult plants and 1.0 for seedlings and saplings and are affected by nitrogen (N) and phosphorus (P) content. However, whether the scaling of R with respect to M (or N and P) varies among different phylogenetic groups (e.g., gymnosperms vs. angiosperms) or during the growing and dormant seasons remains unclear. We measured the whole-plant R and M , and N and P content of the seedlings of four woody species during the growing season (early October) and the dormant season (January). The data show that (i) the scaling exponents of R versus M , R versus N, and R versus P differed significantly among the four species, but (ii), not between the growing and dormant seasons for each of the four species, although (iii) the normalization constants governing the scaling relationships were numerically greater for the growing season compared to the dormant season. In addition, (iv) the scaling exponents of R versus M , R versus N, and R versus P were numerically larger for the two angiosperm species compared to those of the two gymnosperm species, (v) the interspecific scaling exponents for the four species were greater during the growing season than in the dormant season, and (vi), interspecifically, P scaled nearly isometric with N content. Those findings indicate that the metabolic scaling relationships among R , M , N, and P manifest seasonal variation and differ between angiosperm and gymnosperm species, that is, there is no single, canonical scaling exponent for the seedlings of woody species.

TIR-NBS-LRR genes are rare in monocots: evidence from diverse monocot orders

PubMed Central

Tarr, D Ellen K; Alexander, Helen M

2009-01-01

Background Plant resistance (R) gene products recognize pathogen effector molecules. Many R genes code for proteins containing nucleotide binding site (NBS) and C-terminal leucine-rich repeat (LRR) domains. NBS-LRR proteins can be divided into two groups, TIR-NBS-LRR and non-TIR-NBS-LRR, based on the structure of the N-terminal domain. Although both classes are clearly present in gymnosperms and eudicots, only non-TIR sequences have been found consistently in monocots. Since most studies in monocots have been limited to agriculturally important grasses, it is difficult to draw conclusions. The purpose of our study was to look for evidence of these sequences in additional monocot orders. Findings Using degenerate PCR, we amplified NBS sequences from four monocot species (C. blanda, D. marginata, S. trifasciata, and Spathiphyllum sp.), a gymnosperm (C. revoluta) and a eudicot (C. canephora). We successfully amplified TIR-NBS-LRR sequences from dicot and gymnosperm DNA, but not from monocot DNA. Using databases, we obtained NBS sequences from additional monocots, magnoliids and basal angiosperms. TIR-type sequences were not present in monocot or magnoliid sequences, but were present in the basal angiosperms. Phylogenetic analysis supported a single TIR clade and multiple non-TIR clades. Conclusion We were unable to find monocot TIR-NBS-LRR sequences by PCR amplification or database searches. In contrast to previous studies, our results represent five monocot orders (Poales, Zingiberales, Arecales, Asparagales, and Alismatales). Our results establish the presence of TIR-NBS-LRR sequences in basal angiosperms and suggest that although these sequences were present in early land plants, they have been reduced significantly in monocots and magnoliids. PMID:19785756

The Phylogeny and Biogeographic History of Ashes (Fraxinus, Oleaceae) Highlight the Roles of Migration and Vicariance in the Diversification of Temperate Trees

PubMed Central

Hinsinger, Damien Daniel; Basak, Jolly; Gaudeul, Myriam; Cruaud, Corinne; Bertolino, Paola; Frascaria-Lacoste, Nathalie; Bousquet, Jean

2013-01-01

The cosmopolitan genus Fraxinus, which comprises about 40 species of temperate trees and shrubs occupying various habitats in the Northern Hemisphere, represents a useful model to study speciation in long-lived angiosperms. We used nuclear external transcribed spacers (nETS), phantastica gene sequences, and two chloroplast loci (trnH-psbA and rpl32-trnL) in combination with previously published and newly obtained nITS sequences to produce a time-calibrated multi-locus phylogeny of the genus. We then inferred the biogeographic history and evolution of floral morphology. An early dispersal event could be inferred from North America to Asia during the Oligocene, leading to the diversification of the section Melioides sensus lato. Another intercontinental dispersal originating from the Eurasian section of Fraxinus could be dated from the Miocene and resulted in the speciation of F. nigra in North America. In addition, vicariance was inferred to account for the distribution of the other Old World species (sections Sciadanthus, Fraxinus and Ornus). Geographic speciation likely involving dispersal and vicariance could also be inferred from the phylogenetic grouping of geographically close taxa. Molecular dating suggested that the initial divergence of the taxonomical sections occurred during the middle and late Eocene and Oligocene periods, whereas diversification within sections occurred mostly during the late Oligocene and Miocene, which is consistent with the climate warming and accompanying large distributional changes observed during these periods. These various results underline the importance of dispersal and vicariance in promoting geographic speciation and diversification in Fraxinus. Similarities in life history, reproductive and demographic attributes as well as geographical distribution patterns suggest that many other temperate trees should exhibit similar speciation patterns. On the other hand, the observed parallel evolution and reversions in floral morphology would imply a major influence of environmental pressure. The phylogeny obtained and its biogeographical implications should facilitate future studies on the evolution of complex adaptive characters, such as habitat preference, and their possible roles in promoting divergent evolution in trees. PMID:24278282

The phylogeny and biogeographic history of ashes (fraxinus, oleaceae) highlight the roles of migration and vicariance in the diversification of temperate trees.

PubMed

Hinsinger, Damien Daniel; Basak, Jolly; Gaudeul, Myriam; Cruaud, Corinne; Bertolino, Paola; Frascaria-Lacoste, Nathalie; Bousquet, Jean

2013-01-01

The cosmopolitan genus Fraxinus, which comprises about 40 species of temperate trees and shrubs occupying various habitats in the Northern Hemisphere, represents a useful model to study speciation in long-lived angiosperms. We used nuclear external transcribed spacers (nETS), phantastica gene sequences, and two chloroplast loci (trnH-psbA and rpl32-trnL) in combination with previously published and newly obtained nITS sequences to produce a time-calibrated multi-locus phylogeny of the genus. We then inferred the biogeographic history and evolution of floral morphology. An early dispersal event could be inferred from North America to Asia during the Oligocene, leading to the diversification of the section Melioides sensus lato. Another intercontinental dispersal originating from the Eurasian section of Fraxinus could be dated from the Miocene and resulted in the speciation of F. nigra in North America. In addition, vicariance was inferred to account for the distribution of the other Old World species (sections Sciadanthus, Fraxinus and Ornus). Geographic speciation likely involving dispersal and vicariance could also be inferred from the phylogenetic grouping of geographically close taxa. Molecular dating suggested that the initial divergence of the taxonomical sections occurred during the middle and late Eocene and Oligocene periods, whereas diversification within sections occurred mostly during the late Oligocene and Miocene, which is consistent with the climate warming and accompanying large distributional changes observed during these periods. These various results underline the importance of dispersal and vicariance in promoting geographic speciation and diversification in Fraxinus. Similarities in life history, reproductive and demographic attributes as well as geographical distribution patterns suggest that many other temperate trees should exhibit similar speciation patterns. On the other hand, the observed parallel evolution and reversions in floral morphology would imply a major influence of environmental pressure. The phylogeny obtained and its biogeographical implications should facilitate future studies on the evolution of complex adaptive characters, such as habitat preference, and their possible roles in promoting divergent evolution in trees.

Cell size, genome size and the dominance of Angiosperms

NASA Astrophysics Data System (ADS)

Simonin, K. A.; Roddy, A. B.

2016-12-01

Angiosperms are capable of maintaining the highest rates of photosynthetic gas exchange of all land plants. High rates of photosynthesis depends mechanistically both on efficiently transporting water to the sites of evaporation in the leaf and on regulating the loss of that water to the atmosphere as CO2 diffuses into the leaf. Angiosperm leaves are unique in their ability to sustain high fluxes of liquid and vapor phase water transport due to high vein densities and numerous, small stomata. Despite the ubiquity of studies characterizing the anatomical and physiological adaptations that enable angiosperms to maintain high rates of photosynthesis, the underlying mechanism explaining why they have been able to develop such high leaf vein densities, and such small and abundant stomata, is still incomplete. Here we ask whether the scaling of genome size and cell size places a fundamental constraint on the photosynthetic metabolism of land plants, and whether genome downsizing among the angiosperms directly contributed to their greater potential and realized primary productivity relative to the other major groups of terrestrial plants. Using previously published data we show that a single relationship can predict guard cell size from genome size across the major groups of terrestrial land plants (e.g. angiosperms, conifers, cycads and ferns). Similarly, a strong positive correlation exists between genome size and both stomatal density and vein density that together ultimately constrains maximum potential (gs, max) and operational stomatal conductance (gs, op). Further the difference in the slopes describing the covariation between genome size and both gs, max and gs, op suggests that genome downsizing brings gs, op closer to gs, max. Taken together the data presented here suggests that the smaller genomes of angiosperms allow their final cell sizes to vary more widely and respond more directly to environmental conditions and in doing so bring operational photosynthetic metabolism closer to maximum potential photosynthesis.EndFragment

Linear relationships between shoot magnesium and calcium concentrations among angiosperm species are associated with cell wall chemistry.

PubMed

White, Philip J; Broadley, Martin R; El-Serehy, Hamed A; George, Timothy S; Neugebauer, Konrad

2018-05-02

Linear relationships are commonly observed between shoot magnesium ([Mg]shoot) and shoot calcium ([Ca]shoot) concentrations among angiosperm species growing in the same environment. This article argues that, in plants that do not exhibit 'luxury' accumulation of Mg or Ca, (1) distinct stoichiometric relationships between [Mg]shoot and [Ca]shoot are exhibited by at least three groups of angiosperm species, namely commelinid monocots, eudicots excluding Caryophyllales, and Caryophyllales species; (2) these relationships are determined by cell wall chemistry and the Mg/Ca mass quotients in their cell walls; (3) differences between species in [Mg]shoot and [Ca]shoot within each group are associated with differences in the cation exchange capacity (CEC) of the cell walls of different species; and (4) Caryophyllales constitutively accumulate more Mg in their vacuoles than other angiosperm species when grown without a supra-sufficient Mg supply.

Nuclear dna amounts in angiosperms.

PubMed

Bennett, M D; Smith, J B

1976-05-27

The number of angiosperm species for which nuclear DNA amount estimates have been made has nearly trebled since the last collected lists of such values were published, and therefore, publication of a more comprehensive list is over due. This paper lists absolute nuclear DNA amounts for 753 angiosperm species. The dats were assembled primarily for reference purposes, and so the species are listed in alphabetical order, as this was felt to be more helpful to cyto- and biochemists whom, it is anticipated, will be among its major users. The paper also reviews aspects of the history, nomenclature, methods, accuracy and problems of nuclear DNA estimation in angiosperms. No attempt is made to reconsider those aspects of nuclear DNA estimation which have been fully revised previously, although the bibliography of such aspects is given. Instead, the paper is intended as a source of basic information regarding the terminology, practice and limitations of nuclear DNA estimation, especially by Feulgen microdensitometry, as currently practiced.

Ants Sow the Seeds of Global Diversification in Flowering Plants

PubMed Central

Lengyel, Szabolcs; Gove, Aaron D.; Latimer, Andrew M.; Majer, Jonathan D.; Dunn, Robert R.

2009-01-01

Background The extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000–300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory) may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances. Methodology/Principal Findings Using the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions. Conclusions/Significance Myrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on large-scale diversification. PMID:19436714

Hydraulic safety margins and embolism reversal in stems and leaves: why are conifers and angiosperms so different?

PubMed

Johnson, Daniel M; McCulloh, Katherine A; Woodruff, David R; Meinzer, Frederick C

2012-10-01

Angiosperm and coniferous tree species utilize a continuum of hydraulic strategies. Hydraulic safety margins (defined as differences between naturally occurring xylem pressures and pressures that would cause hydraulic dysfunction, or differences between pressures resulting in loss of hydraulic function in adjacent organs (e.g., stems vs. leaves) tend to be much greater in conifers than angiosperms and serve to prevent stem embolism. However, conifers tend to experience embolism more frequently in leaves and roots than angiosperms. Embolism repair is thought to occur by active transport of sugars into empty conduits followed by passive water movement. The most likely source of sugar for refilling is from nonstructural carbohydrate depolymerization in nearby parenchyma cells. Compared to angiosperms, conifers tend to have little parenchyma or nonstructural carbohydrates in their wood. The ability to rapidly repair embolisms may rely on having nearby parenchyma cells, which could explain the need for greater safety margins in conifer wood as compared to angiosperms. The frequent embolisms that occur in the distal portions of conifers are readily repaired, perhaps due to the abundant parenchyma in leaves and roots, and these distal tissues may act as hydraulic circuit breakers that prevent tension-induced embolisms in the attached stems. Frequent embolisms in conifer leaves may also be due to weaker stomatal response to changes in ambient humidity. Although there is a continuum of hydraulic strategies among woody plants, there appear to be two distinct 'behaviors' at the extremes: (1) embolism prevention and (2) embolism occurrence and subsequent repair. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Novel phytochrome sequences in Arabidopsis thaliana: Structure, evolution, and differential expression of a plant regulatory photoreceptor family

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharrock, R.A.; Quail, P.H.

1989-01-01

Phytochrome is a plant regulatory photoreceptor that mediates red light effects on a wide variety of physiological and molecular responses. DNA blot analysis indicates that the Arabidopsis thaliana genome contains four to five phytochrome-related gene sequences. The authors have isolated and sequenced cDNA clones corresponding to three of these genes and have deduced the amino acid sequence of the full-length polypeptide encoded in each case. One of these proteins (phyA) shows 65-80% amino acid sequence identity with the major, etiolated-tissue phytochrome apoproteins described previously in other plant species. The other two polypeptides (phyB and phyC) are unique in that theymore » have low sequence identity with each other, with phyA, and with all previously described phytochromes. The phyA, phyB, and phyC proteins are of similar molecular mass, have related hydropathic profiles, and contain a conserved chromophore attachment region. However, the sequence comparison data indicate that the three phy genes diverged early in plant evolution, well before the divergence of the two major groups of angiosperms, the monocots and dicots. The steady-state level of the phyA transcript is high in dark-grown A. thaliana seedlings and is down-regulated by light. In contrast, the phyB and phyC transcripts are present at lower levels and are not strongly light-regulated. These findings indicate that the red/far red light-responsive phytochrome photoreceptor system in A. thaliana, and perhaps in all higher plants, consists of a family of chromoproteins that are heterogeneous in structure and regulation.« less

Evolution and Expression Patterns of TCP Genes in Asparagales

PubMed Central

Madrigal, Yesenia; Alzate, Juan F.; Pabón-Mora, Natalia

2017-01-01

CYCLOIDEA-like genes are involved in the symmetry gene network, limiting cell proliferation in the dorsal regions of bilateral flowers in core eudicots. CYC-like and closely related TCP genes (acronym for TEOSINTE BRANCHED1, CYCLOIDEA, and PROLIFERATION CELL FACTOR) have been poorly studied in Asparagales, the largest order of monocots that includes both bilateral flowers in Orchidaceae (ca. 25.000 spp) and radially symmetrical flowers in Hypoxidaceae (ca. 200 spp). With the aim of assessing TCP gene evolution in the Asparagales, we isolated TCP-like genes from publicly available databases and our own transcriptomes of Cattleya trianae (Orchidaceae) and Hypoxis decumbens (Hypoxidaceae). Our matrix contains 452 sequences representing the three major clades of TCP genes. Besides the previously identified CYC specific core eudicot duplications, our ML phylogenetic analyses recovered an early CIN-like duplication predating all angiosperms, two CIN-like Asparagales-specific duplications and a duplication prior to the diversification of Orchidoideae and Epidendroideae. In addition, we provide evidence of at least three duplications of PCF-like genes in Asparagales. While CIN-like and PCF-like genes have multiplied in Asparagales, likely enhancing the genetic network for cell proliferation, CYC-like genes remain as single, shorter copies with low expression. Homogeneous expression of CYC-like genes in the labellum as well as the lateral petals suggests little contribution to the bilateral perianth in C. trianae. CIN-like and PCF-like gene expression suggests conserved roles in cell proliferation in leaves, sepals and petals, carpels, ovules and fruits in Asparagales by comparison with previously reported functions in core eudicots and monocots. This is the first large scale analysis of TCP-like genes in Asparagales that will serve as a platform for in-depth functional studies in emerging model monocots. PMID:28144250

Carpeloidy in flower evolution and diversification: a comparative study in Carica papaya and Arabidopsis thaliana

PubMed Central

Ronse De Craene, Louis; Tréhin, Christophe; Morel, Patrice; Negrutiu, Ioan

2011-01-01

Background and Aims Bisexual flowers of Carica papaya range from highly regular flowers to morphs with various fusions of stamens to the ovary. Arabidopsis thaliana sup1 mutants have carpels replaced by chimeric carpel–stamen structures. Comparative analysis of stamen to carpel conversions in the two different plant systems was used to understand the stage and origin of carpeloidy when derived from stamen tissues, and consequently to understand how carpeloidy contributes to innovations in flower evolution. Methods Floral development of bisexual flowers of Carica was studied by scanning electron microscopy and was compared with teratological sup mutants of A. thaliana. Key Results In Carica development of bisexual flowers was similar to wild (unisexual) forms up to locule initiation. Feminization ranges from fusion of stamen tissue to the gynoecium to complete carpeloidy of antepetalous stamens. In A. thaliana, partial stamen feminization occurs exclusively at the flower apex, with normal stamens forming at the periphery. Such transformations take place relatively late in development, indicating strong developmental plasticity of most stamen tissues. These results are compared with evo-devo theories on flower bisexuality, as derived from unisexual ancestors. The Arabidopsis data highlight possible early evolutionary events in the acquisition of bisexuality by a patchy transformation of stamen parts into female parts linked to a flower axis-position effect. The Carica results highlight tissue-fusion mechanisms in angiosperms leading to carpeloidy once bisexual flowers have evolved. Conclusions We show two different developmental routes leading to stamen to carpel conversions by late re-specification. The process may be a fundamental aspect of flower development that is hidden in most instances by developmental homeostasis. PMID:21504912

The plastid genomes of flowering plants.

PubMed

Ruhlman, Tracey A; Jansen, Robert K

2014-01-01

The plastid genome (plastome) has proved a valuable source of data for evaluating evolutionary relationships among angiosperms. Through basic and applied approaches, plastid transformation technology offers the potential to understand and improve plant productivity, providing food, fiber, energy and medicines to meet the needs of a burgeoning global population. The growing genomic resources available to both phylogenetic and biotechnological investigations are allowing novel insights and expanding the scope of plastome research to encompass new species. In this chapter we present an overview of some of the seminal and contemporary research that has contributed to our current understanding of plastome evolution and attempt to highlight the relationship between evolutionary mechanisms and tools of plastid genetic engineering.

New insights into the phylogeny of the TMBIM superfamily across the three of life: Comparative genomics and synteny networks reveal independent evolution of the BI and LFG families in plants.

PubMed

Gamboa-Tuz, Samuel D; Pereira-Santana, Alejandro; Zhao, Tao; Schranz, M Eric; Castano, Enrique; Rodriguez-Zapata, Luis C

2018-04-25

The Transmembrane BAX Inhibitor Motif containing (TMBIM) superfamily, divided into BAX Inhibitor (BI) and Lifeguard (LFG) families, comprises a group of cytoprotective cell death regulators conserved in prokaryotes and eukaryotes. However, no research has focused on the evolution of this superfamily in plants. We identified 685 TMBIM proteins in 171 organisms from Archaea, Bacteria, and Eukarya, and provided a phylogenetic overview of the whole TMBIM superfamily. Then, we used orthology and synteny network analyses to further investigate the evolution and expansion of the BI and LFG families in 48 plants from diverse taxa. Plant BI family forms a single monophyletic group; however, monocot BI sequences transposed to another genomic context during evolution. Plant LFG family, which expanded trough whole genome and tandem duplications, is subdivided in LFG I, LFG IIA, and LFG IIB major phylogenetic groups, and retains synteny in angiosperms. Moreover, two orthologous groups (OGs) are shared between bryophytes and seed plants. Other several lineage-specific OGs are present in plants. This work clarifies the phylogenetic classification of the TMBIM superfamily across the three domains of life. Furthermore, it sheds new light on the evolution of the BI and LFG families in plants providing a benchmark for future research. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Repeated evolution of vertebrate pollination syndromes in a recently diverged Andean plant clade.

PubMed

Lagomarsino, Laura P; Forrestel, Elisabeth J; Muchhala, Nathan; Davis, Charles C

2017-08-01

Although specialized interactions, including those involving plants and their pollinators, are often invoked to explain high species diversity, they are rarely explored at macroevolutionary scales. We investigate the dynamic evolution of hummingbird and bat pollination syndromes in the centropogonid clade (Lobelioideae: Campanulaceae), an Andean-centered group of ∼550 angiosperm species. We demonstrate that flowers hypothesized to be adapted to different pollinators based on flower color fall into distinct regions of morphospace, and this is validated by morphology of species with known pollinators. This supports the existence of pollination syndromes in the centropogonids, an idea corroborated by ecological studies. We further demonstrate that hummingbird pollination is ancestral, and that bat pollination has evolved ∼13 times independently, with ∼11 reversals. This convergence is associated with correlated evolution of floral traits within selective regimes corresponding to pollination syndrome. Collectively, our results suggest that floral morphological diversity is extremely labile, likely resulting from selection imposed by pollinators. Finally, even though this clade's rapid diversification is partially attributed to their association with vertebrate pollinators, we detect no difference in diversification rates between hummingbird- and bat-pollinated lineages. Our study demonstrates the utility of pollination syndromes as a proxy for ecological relationships in macroevolutionary studies of certain species-rich clades. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Gradual disintegration of the floral symmetry gene network is implicated in the evolution of a wind-pollination syndrome

PubMed Central

Preston, Jill C.; Martinez, Ciera C.; Hileman, Lena C.

2011-01-01

Angiosperms exhibit staggering diversity in floral form, and evolution of floral morphology is often correlated with changes in pollination syndrome. The showy, bilaterally symmetrical flowers of the model species Antirrhinum majus (Plantaginaceae) are highly specialized for bee pollination. In A. majus, CYCLOIDEA (CYC), DICHOTOMA (DICH), RADIALIS (RAD), and DIVARICATA (DIV) specify the development of floral bilateral symmetry. However, it is unclear to what extent evolution of these genes has resulted in flower morphological divergence among closely related members of Plantaginaceae differing in pollination syndrome. We compared floral symmetry genes from insect-pollinated Digitalis purpurea, which has bilaterally symmetrical flowers, with those from closely related Aragoa abietina and wind-pollinated Plantago major, both of which have radially symmetrical flowers. We demonstrate that Plantago, but not Aragoa, species have lost a dorsally expressed CYC-like gene and downstream targets RAD and DIV. Furthermore, the single P. major CYC-like gene is expressed across all regions of the flower, similar to expression of its ortholog in closely related Veronica serpyllifolia. We propose that changes in the expression of duplicated CYC-like genes led to the evolution of radial flower symmetry in Aragoa/Plantago, and that further disintegration of the symmetry gene pathway resulted in the wind-pollination syndrome of Plantago. This model underscores the potential importance of gene loss in the evolution of ecologically important traits. PMID:21282634

A universe of dwarfs and giants: genome size and chromosome evolution in the monocot family Melanthiaceae.

PubMed

Pellicer, Jaume; Kelly, Laura J; Leitch, Ilia J; Zomlefer, Wendy B; Fay, Michael F

2014-03-01

• Since the occurrence of giant genomes in angiosperms is restricted to just a few lineages, identifying where shifts towards genome obesity have occurred is essential for understanding the evolutionary mechanisms triggering this process. • Genome sizes were assessed using flow cytometry in 79 species and new chromosome numbers were obtained. Phylogenetically based statistical methods were applied to infer ancestral character reconstructions of chromosome numbers and nuclear DNA contents. • Melanthiaceae are the most diverse family in terms of genome size, with C-values ranging more than 230-fold. Our data confirmed that giant genomes are restricted to tribe Parideae, with most extant species in the family characterized by small genomes. Ancestral genome size reconstruction revealed that the most recent common ancestor (MRCA) for the family had a relatively small genome (1C = 5.37 pg). Chromosome losses and polyploidy are recovered as the main evolutionary mechanisms generating chromosome number change. • Genome evolution in Melanthiaceae has been characterized by a trend towards genome size reduction, with just one episode of dramatic DNA accumulation in Parideae. Such extreme contrasting profiles of genome size evolution illustrate the key role of transposable elements and chromosome rearrangements in driving the evolution of plant genomes. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Use of DNA barcodes to identify flowering plants.

PubMed

Kress, W John; Wurdack, Kenneth J; Zimmer, Elizabeth A; Weigt, Lee A; Janzen, Daniel H

2005-06-07

Methods for identifying species by using short orthologous DNA sequences, known as "DNA barcodes," have been proposed and initiated to facilitate biodiversity studies, identify juveniles, associate sexes, and enhance forensic analyses. The cytochrome c oxidase 1 sequence, which has been found to be widely applicable in animal barcoding, is not appropriate for most species of plants because of a much slower rate of cytochrome c oxidase 1 gene evolution in higher plants than in animals. We therefore propose the nuclear internal transcribed spacer region and the plastid trnH-psbA intergenic spacer as potentially usable DNA regions for applying barcoding to flowering plants. The internal transcribed spacer is the most commonly sequenced locus used in plant phylogenetic investigations at the species level and shows high levels of interspecific divergence. The trnH-psbA spacer, although short ( approximately 450-bp), is the most variable plastid region in angiosperms and is easily amplified across a broad range of land plants. Comparison of the total plastid genomes of tobacco and deadly nightshade enhanced with trials on widely divergent angiosperm taxa, including closely related species in seven plant families and a group of species sampled from a local flora encompassing 50 plant families (for a total of 99 species, 80 genera, and 53 families), suggest that the sequences in this pair of loci have the potential to discriminate among the largest number of plant species for barcoding purposes.

Evolution of fruit development genes in flowering plants

PubMed Central

Pabón-Mora, Natalia; Wong, Gane Ka-Shu; Ambrose, Barbara A.

2014-01-01

The genetic mechanisms regulating dry fruit development and opercular dehiscence have been identified in Arabidopsis thaliana. In the bicarpellate silique, valve elongation and differentiation is controlled by FRUITFULL (FUL) that antagonizes SHATTERPROOF1-2 (SHP1/SHP2) and INDEHISCENT (IND) at the dehiscence zone where they control normal lignification. SHP1/2 are also repressed by REPLUMLESS (RPL), responsible for replum formation. Similarly, FUL indirectly controls two other factors ALCATRAZ (ALC) and SPATULA (SPT) that function in the proper formation of the separation layer. FUL and SHP1/2 belong to the MADS-box family, IND and ALC belong to the bHLH family and RPL belongs to the homeodomain family, all of which are large transcription factor families. These families have undergone numerous duplications and losses in plants, likely accompanied by functional changes. Functional analyses of homologous genes suggest that this network is fairly conserved in Brassicaceae and less conserved in other core eudicots. Only the MADS box genes have been functionally characterized in basal eudicots and suggest partial conservation of the functions recorded for Brassicaceae. Here we do a comprehensive search of SHP, IND, ALC, SPT, and RPL homologs across core-eudicots, basal eudicots, monocots and basal angiosperms. Based on gene-tree analyses we hypothesize what parts of the network for fruit development in Brassicaceae, in particular regarding direct and indirect targets of FUL, might be conserved across angiosperms. PMID:25018763

Native fauna on exotic trees: phylogenetic conservatism and geographic contingency in two lineages of phytophages on two lineages of trees.

PubMed

Gossner, Martin M; Chao, Anne; Bailey, Richard I; Prinzing, Andreas

2009-05-01

The relative roles of evolutionary history and geographical and ecological contingency for community assembly remain unknown. Plant species, for instance, share more phytophages with closer relatives (phylogenetic conservatism), but for exotic plants introduced to another continent, this may be overlaid by geographically contingent evolution or immigration from locally abundant plant species (mass effects). We assessed within local forests to what extent exotic trees (Douglas-fir, red oak) recruit phytophages (Coleoptera, Heteroptera) from more closely or more distantly related native plants. We found that exotics shared more phytophages with natives from the same major plant lineage (angiosperms vs. gymnosperms) than with natives from the other lineage. This was particularly true for Heteroptera, and it emphasizes the role of host specialization in phylogenetic conservatism of host use. However, for Coleoptera on Douglas-fir, mass effects were important: immigration from beech increased with increasing beech abundance. Within a plant phylum, phylogenetic proximity of exotics and natives increased phytophage similarity, primarily in younger Coleoptera clades on angiosperms, emphasizing a role of past codiversification of hosts and phytophages. Overall, phylogenetic conservatism can shape the assembly of local phytophage communities on exotic trees. Whether it outweighs geographic contingency and mass effects depends on the interplay of phylogenetic scale, local abundance of native tree species, and the biology and evolutionary history of the phytophage taxon.

Evolutionary dynamism in bryophytes: Phylogenomic inferences confirm rapid radiation in the moss family Funariaceae.

PubMed

Medina, Rafael; Johnson, Matthew; Liu, Yang; Wilding, Nicholas; Hedderson, Terry A; Wickett, Norman; Goffinet, Bernard

2018-03-01

Rapid diversifications of plants are primarily documented and studied in angiosperms, which are perceived as evolutionarily dynamic. Recent studies have, however, revealed that bryophytes have also undergone periods of rapid radiation. The speciose family Funariaceae, including the model taxon Physcomitrella patens, is one such lineage. Here, we infer relationships among major lineages within the Entosthodon-Physcomitrium complex from virtually complete organellar exomes (i.e., 123 genes) obtained through high throughput sequencing of genomic libraries enriched in these loci via targeted locus capture. Based on these extensive exonic data we (1) reconstructed a robust backbone topology of the Funariaceae, (2) confirmed the monophyly of Funaria and the polyphyly of Entosthodon, Physcomitrella, and Physcomitrium, and (3) argue for the occurrence of a rapid radiation within the Entosthodon-Physcomitrium complex that began 28 mya and gave rise more than half of the species diversity of the family. This diversification may have been triggered by a whole genome duplication and coincides with global Eocene cooling that continued through the Oligocene and Miocene. The Funariaceae join a growing list of bryophyte lineages whose history is marked by at least one burst of diversification, and our study thereby strengthens the view that bryophytes are evolutionarily dynamic lineages and that patterns and processes characterizing the evolution of angiosperms may be universal among land plants. Copyright © 2017 Elsevier Inc. All rights reserved.

Phylogenetic analysis of the “ECE” (CYC/TB1) clade reveals duplications predating the core eudicots

PubMed Central

Howarth, Dianella G.; Donoghue, Michael J.

2006-01-01

Flower symmetry is of special interest in understanding angiosperm evolution and ecology. Evidence from the Antirrhineae (snapdragon and relatives) indicates that several TCP gene-family transcription factors, especially CYCLOIDEA (CYC) and DICHOTOMA (DICH), play a role in specifying dorsal identity in the corolla and androecium of monosymmetric (bilateral) flowers. Studies of rosid and asterid angiosperms suggest that orthologous TCP genes may be important in dorsal identity, but there has been no broad phylogenetic context to determine copy number or orthology. Here, we compare published data from rosids and asterids with newly collected data from ranunculids, caryophyllids, Saxifragales, and Asterales to ascertain the phylogenetic placement of major duplications in the “ECE” (CYC/TB1) clade of TCP transcription factors. Bayesian analyses indicate that there are three major copies of “CYC” in the ECE clade, and that duplications leading to these copies predate the core eudicots. CYC1 contains no subsequent duplications and may not be expressed in floral tissue. CYC3 exhibits similar patterns of duplication to CYC2 in several groups. Using RT-PCR, we show that, in flowers of Lonicera morrowii (Caprifoliaceae), DipsCYC2B is expressed in the four dorsal petals and not in the ventral petal. DipsCYC3B is expressed in flower and petal primordia, possibly most strongly in the ventral petal. PMID:16754863

Phylogeny of seed plants based on all three genomic compartments: extant gymnosperms are monophyletic and Gnetales' closest relatives are conifers.

PubMed

Bowe, L M; Coat, G; dePamphilis, C W

2000-04-11

Efforts to resolve Darwin's "abominable mystery"-the origin of angiosperms-have led to the conclusion that Gnetales and various fossil groups are sister to angiosperms, forming the "anthophytes." Morphological homologies, however, are difficult to interpret, and molecular data have not provided clear resolution of relationships among major groups of seed plants. We introduce two sequence data sets from slowly evolving mitochondrial genes, cox1 and atpA, which unambiguously reject the anthophyte hypothesis, favoring instead a close relationship between Gnetales and conifers. Parsimony- and likelihood-based analyses of plastid rbcL and nuclear 18S rDNA alone and with cox1 and atpA also strongly support a gnetophyte-conifer grouping. Surprisingly, three of four genes (all but nuclear rDNA) and combined three-genome analyses also suggest or strongly support Gnetales as derived conifers, sister to Pinaceae. Analyses with outgroups screened to avoid long branches consistently identify all gymnosperms as a monophyletic sister group to angiosperms. Combined three- and four-gene rooted analyses resolve the branching order for the remaining major groups-cycads separate from other gymnosperms first, followed by Ginkgo and then (Gnetales + Pinaceae) sister to a monophyletic group with all other conifer families. The molecular phylogeny strongly conflicts with current interpretations of seed plant morphology, and implies that many similarities between gnetophytes and angiosperms, such as "flower-like" reproductive structures and double fertilization, were independently derived, whereas other characters could emerge as synapomorphies for an expanded conifer group including Gnetales. An initial angiosperm-gymnosperm split implies a long stem lineage preceding the explosive Mesozoic radiation of flowering plants and suggests that angiosperm origins and homologies should be sought among extinct seed plant groups.

Evaluating the Impact of Genomic Data and Priors on Bayesian Estimates of the Angiosperm Evolutionary Timescale.

PubMed

Foster, Charles S P; Sauquet, Hervê; van der Merwe, Marlien; McPherson, Hannah; Rossetto, Maurizio; Ho, Simon Y W

2017-05-01

The evolutionary timescale of angiosperms has long been a key question in biology. Molecular estimates of this timescale have shown considerable variation, being influenced by differences in taxon sampling, gene sampling, fossil calibrations, evolutionary models, and choices of priors. Here, we analyze a data set comprising 76 protein-coding genes from the chloroplast genomes of 195 taxa spanning 86 families, including novel genome sequences for 11 taxa, to evaluate the impact of models, priors, and gene sampling on Bayesian estimates of the angiosperm evolutionary timescale. Using a Bayesian relaxed molecular-clock method, with a core set of 35 minimum and two maximum fossil constraints, we estimated that crown angiosperms arose 221 (251-192) Ma during the Triassic. Based on a range of additional sensitivity and subsampling analyses, we found that our date estimates were generally robust to large changes in the parameters of the birth-death tree prior and of the model of rate variation across branches. We found an exception to this when we implemented fossil calibrations in the form of highly informative gamma priors rather than as uniform priors on node ages. Under all other calibration schemes, including trials of seven maximum age constraints, we consistently found that the earliest divergences of angiosperm clades substantially predate the oldest fossils that can be assigned unequivocally to their crown group. Overall, our results and experiments with genome-scale data suggest that reliable estimates of the angiosperm crown age will require increased taxon sampling, significant methodological changes, and new information from the fossil record. [Angiospermae, chloroplast, genome, molecular dating, Triassic.]. © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Angiosperms Are Unique among Land Plant Lineages in the Occurrence of Key Genes in the RNA-Directed DNA Methylation (RdDM) Pathway

PubMed Central

Ma, Lu; Hatlen, Andrea; Kelly, Laura J.; Becher, Hannes; Wang, Wencai; Kovarik, Ales; Leitch, Ilia J.; Leitch, Andrew R.

2015-01-01

The RNA-directed DNA methylation (RdDM) pathway can be divided into three phases: 1) small interfering RNA biogenesis, 2) de novo methylation, and 3) chromatin modification. To determine the degree of conservation of this pathway we searched for key genes among land plants. We used OrthoMCL and the OrthoMCL Viridiplantae database to analyze proteomes of species in bryophytes, lycophytes, monilophytes, gymnosperms, and angiosperms. We also analyzed small RNA size categories and, in two gymnosperms, cytosine methylation in ribosomal DNA. Six proteins were restricted to angiosperms, these being NRPD4/NRPE4, RDM1, DMS3 (defective in meristem silencing 3), SHH1 (SAWADEE homeodomain homolog 1), KTF1, and SUVR2, although we failed to find the latter three proteins in Fritillaria persica, a species with a giant genome. Small RNAs of 24 nt in length were abundant only in angiosperms. Phylogenetic analyses of Dicer-like (DCL) proteins showed that DCL2 was restricted to seed plants, although it was absent in Gnetum gnemon and Welwitschia mirabilis. The data suggest that phases (1) and (2) of the RdDM pathway, described for model angiosperms, evolved with angiosperms. The absence of some features of RdDM in F. persica may be associated with its large genome. Phase (3) is probably the most conserved part of the pathway across land plants. DCL2, involved in virus defense and interaction with the canonical RdDM pathway to facilitate methylation of CHH, is absent outside seed plants. Its absence in G. gnemon, and W. mirabilis coupled with distinctive patterns of CHH methylation, suggest a secondary loss of DCL2 following the divergence of Gnetales. PMID:26338185

Chemical mimicry of insect oviposition sites: a global analysis of convergence in angiosperms.

PubMed

Jürgens, Andreas; Wee, Suk-Ling; Shuttleworth, Adam; Johnson, Steven D

2013-09-01

Floral mimicry of decaying plant or animal material has evolved in many plant lineages and exploits, for the purpose of pollination, insects seeking oviposition sites. Existing studies suggest that volatile signals play a particularly important role in these mimicry systems. Here, we present the first large-scale phylogenetically informed study of patterns of evolution in the volatile emissions of plants that mimic insect oviposition sites. Multivariate analyses showed strong convergent evolution, represented by distinct clusters in chemical phenotype space of plants that mimic animal carrion, decaying plant material, herbivore dung and omnivore/carnivore faeces respectively. These plants deploy universal infochemicals that serve as indicators for the main nutrients utilised by saprophagous, coprophagous and necrophagous insects. The emission of oligosulphide-dominated volatile blends very similar to those emitted by carrion has evolved independently in at least five plant families (Annonaceae, Apocynaceae, Araceae, Orchidaceae and Rafflesiaceae) and characterises plants associated mainly with pollination by necrophagous flies and beetles. © 2013 John Wiley & Sons Ltd/CNRS.

Phytoplasma-conserved phyllogen proteins induce phyllody across the Plantae by degrading floral MADS domain proteins.

PubMed

Kitazawa, Yugo; Iwabuchi, Nozomu; Himeno, Misako; Sasano, Momoka; Koinuma, Hiroaki; Nijo, Takamichi; Tomomitsu, Tatsuya; Yoshida, Tetsuya; Okano, Yukari; Yoshikawa, Nobuyuki; Maejima, Kensaku; Oshima, Kenro; Namba, Shigetou

2017-05-17

ABCE-class MADS domain transcription factors (MTFs) are key regulators of floral organ development in angiosperms. Aberrant expression of these genes can result in abnormal floral traits such as phyllody. Phyllogen is a virulence factor conserved in phytoplasmas, plant pathogenic bacteria of the class Mollicutes. It triggers phyllody in Arabidopsis thaliana by inducing degradation of A- and E-class MTFs. However, it is still unknown whether phyllogen can induce phyllody in plants other than A. thaliana, although phytoplasma-associated phyllody symptoms are observed in a broad range of angiosperms. In this study, phyllogen was shown to cause phyllody phenotypes in several eudicot species belonging to three different families. Moreover, phyllogen can interact with MTFs of not only angiosperm species including eudicots and monocots but also gymnosperms and a fern, and induce their degradation. These results suggest that phyllogen induces phyllody in angiosperms and inhibits MTF function in diverse plant species. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Evolution of exceptional species richness among lineages of fleshy-fruited Myrtaceae

PubMed Central

Biffin, Ed; Lucas, Eve J.; Craven, Lyn A.; Ribeiro da Costa, Itayguara; Harrington, Mark G.; Crisp, Michael D.

2010-01-01

Background and Aims The angiosperm family Myrtaceae comprises 17 tribes with more than half of the estimated 5500 species being referred to the fleshy-fruited and predominantly rainforest associated Syzygieae and Myrteae. Previous studies suggest that fleshy fruits have evolved separately in these lineages, whereas generally shifts in fruit morphology have been variously implicated in diversification rate shifts among angiosperms. A phylogenetic hypothesis and estimate divergence times for Myrtaceae is developed as a basis to explore the evidence for, and drivers of, elevated diversification rates among the fleshy-fruited tribes of Myrtaceae. Methods Bayesian phylogenetic analyses of plastid and nuclear DNA sequences were used to estimate intertribal relationships and lineage divergence times in Myrtaceae. Focusing on the fleshy-fruited tribes, a variety of statistical approaches were used to assess diversification rates and diversification rate shifts across the family. Key Results Analyses of the sequence data provide a strongly supported phylogenetic hypothesis for Myrtaceae. Relative to previous studies, substantially younger ages for many of the clades are reported, and it is argued that the use of flexible calibrations to incorporate fossil data provides more realistic divergence estimates than the use of errorless point calibrations. It is found that Syzygieae and Myrteae have experienced elevated diversification rates relative to other lineages of Myrtaceae. Positive shifts in diversification rate have occurred separately in each lineage, associated with a shift from dry to fleshy fruit. Conclusions Fleshy fruits have evolved independently in Syzygieae and Myrteae, and this is accompanied by exceptional diversification rate shifts in both instances, suggesting that the evolution of fleshy fruits is a key innovation for rainforest Myrtaceae. Noting the scale dependency of this hypothesis, more complex explanations may be required to explain diversification rate shifts occurring within the fleshy-fruited tribes, and the suggested phylogenetic hypothesis provides an appropriate framework for this undertaking. PMID:20462850

Are relationships between pollen-ovule ratio and pollen and seed size explained by sex allocation?

PubMed

Burd, Martin

2011-10-01

Positive correlations between pollen-ovule ratio and seed size, and negative correlations between pollen-ovule ratio and pollen grain size have been noted frequently in a wide variety of angiosperm taxa. These relationships are commonly explained as a consequence of sex allocation on the basis of a simple model proposed by Charnov. Indeed, the theoretical expectation from the model has been the basis for interest in the empirical pattern. However, the predicted relationship is a necessary consequence of the mathematics of the model, which therefore has little explanatory power, even though its predictions are consistent with empirical results. The evolution of pollen-ovule ratios is likely to depend on selective factors affecting mating system, pollen presentation and dispensing, patterns of pollen receipt, pollen tube competition, female mate choice through embryo abortion, as well as genetic covariances among pollen, ovule, and seed size and other reproductive traits. To the extent the empirical correlations involving pollen-ovule ratios are interesting, they will need explanation in terms of a suite of selective factors. They are not explained simply by sex allocation trade-offs. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

Utility of 17 chloroplast genes for inferring the phylogeny of the basal angiosperms.

PubMed

Graham, S W; Olmstead, R G

2000-11-01

Sequences from 14 slowly evolving chloroplast genes (including three highly conserved introns) were obtained for representative basal angiosperm and seed-plant taxa, using novel primers described here. These data were combined with published sequences from atpB, rbcL, and newly obtained sequences from ndhF. Combined data from these 17 genes permit sturdy, well-resolved inference of major aspects of basal angiosperm relationships, demonstrating that the new primers are valuable tools for sorting out the deepest events in flowering plant phylogeny. Sequences from the inverted repeat (IR) proved to be particularly reliable (low homoplasy, high retention index). Representatives of Cabomba and Illicium were the first two successive branches of the angiosperms in an initial sampling of 19 exemplar taxa. This result was strongly supported by bootstrap analysis and by two small insertion/deletion events in the slowly evolving introns. Several paleoherb groups (representatives of Piperales) formed a strongly supported clade with taxa representing core woody magnoliids (Laurales, Magnoliales, and Winteraceae). The monophyly of the sampled eudicots and monocots was also well supported. Analyses of three major partitions of the data showed many of the same clades and supported the rooting seen with all the data combined. While Amborella trichopoda was supported as the sister group of the remaining angiosperms when we added Amborella and Nymphaea odorata to the analysis, a strongly conflicting rooting was observed when Amborella alone was added.

Low assimilation efficiency of photorespiratory ammonia in conifer leaves.

PubMed

Miyazawa, Shin-Ichi; Nishiguchi, Mitsuru; Futamura, Norihiro; Yukawa, Tomohisa; Miyao, Mitsue; Maruyama, Tsuyoshi Emilio; Kawahara, Takayuki

2018-06-09

Glutamine synthetase (GS) localized in the chloroplasts, GS2, is a key enzyme in the assimilation of ammonia (NH 3 ) produced from the photorespiration pathway in angiosperms, but it is absent from some coniferous species belonging to Pinaceae such as Pinus. We examined whether the absence of GS2 is common in conifers (Pinidae) and also addressed the question of whether assimilation efficiency of photorespiratory NH 3 differs between conifers that may potentially lack GS2 and angiosperms. Search of the expressed sequence tag database of Cryptomeria japonica, a conifer in Cupressaceae, and immunoblotting analyses of leaf GS proteins of 13 species from all family members in Pinidae revealed that all tested conifers exhibited only GS1 isoforms. We compared leaf NH 3 compensation point (γ NH3 ) and the increments in leaf ammonium content per unit photorespiratory activity (NH 3 leakiness), i.e. inverse measures of the assimilation efficiency, between conifers (C. japonica and Pinus densiflora) and angiosperms (Phaseolus vulgaris and two Populus species). Both γ NH3 and NH 3 leakiness were higher in the two conifers than in the three angiosperms tested. Thus, we concluded that the absence of GS2 is common in conifers, and assimilation efficiency of photorespiratory NH 3 is intrinsically lower in conifer leaves than in angiosperm leaves. These results imply that acquisition of GS2 in land plants is an adaptive mechanism for efficient NH 3 assimilation under photorespiratory environments.

Molecular control of normal and acrocona mutant seed cone development in Norway spruce (Picea abies) and the evolution of conifer ovule-bearing organs.

PubMed

Carlsbecker, Annelie; Sundström, Jens F; Englund, Marie; Uddenberg, Daniel; Izquierdo, Liz; Kvarnheden, Anders; Vergara-Silva, Francisco; Engström, Peter

2013-10-01

Reproductive organs in seed plants are morphologically divergent and their evolutionary history is often unclear. The mechanisms controlling their development have been extensively studied in angiosperms but are poorly understood in conifers and other gymnosperms. Here, we address the molecular control of seed cone development in Norway spruce, Picea abies. We present expression analyses of five novel MADS-box genes in comparison with previously identified MADS and LEAFY genes at distinct developmental stages. In addition, we have characterized the homeotic transformation from vegetative shoot to female cone and associated changes in regulatory gene expression patterns occurring in the acrocona mutant. The analyses identified genes active at the onset of ovuliferous and ovule development and identified expression patterns marking distinct domains of the ovuliferous scale. The reproductive transformation in acrocona involves the activation of all tested genes normally active in early cone development, except for an AGAMOUS-LIKE6/SEPALLATA (AGL6/SEP) homologue. This absence may be functionally associated with the nondeterminate development of the acrocona ovule-bearing scales. Our morphological and gene expression analyses give support to the hypothesis that the modern cone is a complex structure, and the ovuliferous scale the result of reductions and compactions of an ovule-bearing axillary short shoot in cones of Paleozoic conifers. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Papilionoid inflorescences revisited (Leguminosae-Papilionoideae).

PubMed

Prenner, Gerhard

2013-11-01

The inflorescence structure determines the spatiotemporal arrangement of the flowers during anthesis and is therefore vital for reproductive success. The Leguminosae are among the largest angiosperm plant families and they include some important crop plants. In papilionoid legumes, the raceme is the most common type of inflorescence. However, a range of other inflorescence types have evolved via various developmental processes. A (re-)investigation of inflorescences in Swainsona formosa, Cicer arietinum, Abrus precatorius, Hardenbergia violacea and Kennedia nigricans leads to new insights into reduction mechanisms and to a new hypothesis on the evolution of the papilionoid pseudoraceme. Inflorescence morphology and ontogeny were studied using scanning electron microscopy (SEM). The inflorescence in S. formosa is an umbel with a rare type of pendulum symmetry which may be triggered by the subtending leaf. Inflorescences in C. arietinum are reduced to a single flower. An early formed adaxial bulge is the sterile apex of the inflorescence (i.e. the inflorescence is open and not terminated by a flower). In partial inflorescences of A. precatorius, the axis is reduced and its meristem is relocated towards the main inflorescence. Flower initiation follows a peculiar pendulum pattern. Partial inflorescences in H. violacea and in K. nigricans show reduction tendencies. In both taxa, initiated but early reduced bracteoles are present. Pendulum symmetry in S. formosa is probably associated with distichous phyllotaxis. In C. arietinum, strong reduction tendencies are revealed. Based on studies of A. precatorius, the papilionoid pseudoraceme is reinterpreted as a compound raceme with condensed lateral axes. From an Abrus-like inflorescence, other types can be derived via reduction of flower number and synchronization of flower development. A plea is made for uniform usage of inflorescence terminology.

Papilionoid inflorescences revisited (Leguminosae-Papilionoideae)

PubMed Central

Prenner, Gerhard

2013-01-01

Background and Aims The inflorescence structure determines the spatiotemporal arrangement of the flowers during anthesis and is therefore vital for reproductive success. The Leguminosae are among the largest angiosperm plant families and they include some important crop plants. In papilionoid legumes, the raceme is the most common type of inflorescence. However, a range of other inflorescence types have evolved via various developmental processes. A (re-)investigation of inflorescences in Swainsona formosa, Cicer arietinum, Abrus precatorius, Hardenbergia violacea and Kennedia nigricans leads to new insights into reduction mechanisms and to a new hypothesis on the evolution of the papilionoid pseudoraceme. Methods Inflorescence morphology and ontogeny were studied using scanning electron microscopy (SEM). Key Results The inflorescence in S. formosa is an umbel with a rare type of pendulum symmetry which may be triggered by the subtending leaf. Inflorescences in C. arietinum are reduced to a single flower. An early formed adaxial bulge is the sterile apex of the inflorescence (i.e. the inflorescence is open and not terminated by a flower). In partial inflorescences of A. precatorius, the axis is reduced and its meristem is relocated towards the main inflorescence. Flower initiation follows a peculiar pendulum pattern. Partial inflorescences in H. violacea and in K. nigricans show reduction tendencies. In both taxa, initiated but early reduced bracteoles are present. Conclusions Pendulum symmetry in S. formosa is probably associated with distichous phyllotaxis. In C. arietinum, strong reduction tendencies are revealed. Based on studies of A. precatorius, the papilionoid pseudoraceme is reinterpreted as a compound raceme with condensed lateral axes. From an Abrus-like inflorescence, other types can be derived via reduction of flower number and synchronization of flower development. A plea is made for uniform usage of inflorescence terminology. PMID:23235698

Floral structure and development in the monoecious palm Gaussia attenuata (Arecaceae; Arecoideae)

PubMed Central

Castaño, Felipe; Stauffer, Fred; Marquinez, Xavier; Crèvecoeur, Michèle; Collin, Myriam; Pintaud, Jean-Christophe; Tregear, James

2014-01-01

Background and Aims Sexual dimorphism, at both the flower and plant level, is widespread in the palm family (Arecaceae), in contrast to the situation in angiosperms as a whole. The tribe Chamaedoreeae is of special interest for studies of the evolution of sexual expression since dioecy appears to have evolved independently twice in this group from a monoecious ancestor. In order to understand the underlying evolutionary pathways, it is important to obtain detailed information on flower structure and development in each of the main clades. Methods Dissection and light and scanning electron microscopy were performed on developing flowers of Gaussia attenuata, a neotropical species belonging to one of the three monoecious genera of the tribe. Key Results Like species of the other monoecious genera of the Chamaedoreeae (namely Hyophorbe and Synechanthus), G. attenuata produces a bisexual flower cluster known as an acervulus, consisting of a row of male flowers with a basal female flower. Whereas the sterile androecium of female flowers terminated its development at an early stage of floral ontogeny, the pistillode of male flowers was large in size but with no recognizable ovule, developing for a longer period of time. Conspicuous nectary differentiation in the pistillode suggested a possible role in pollinator attraction. Conclusions Gaussia attenuata displays a number of floral characters that are likely to be ancestral to the tribe, notably the acervulus flower cluster, which is conserved in the other monoecious genera and also (albeit in a unisexual male form) in the dioecious genera (Wendlandiella and a few species of Chamaedorea). Comparison with earlier data from other genera suggests that large nectariferous pistillodes and early arrest in staminode development might also be regarded as ancestral characters in this tribe. PMID:25006179

Evolution of root endosymbiosis with bacteria: How novel are nodules?

PubMed

Markmann, Katharina; Parniske, Martin

2009-02-01

Plants form diverse symbioses with nitrogen-fixing bacteria to gain access to ammonium, a product of the prokaryote-exclusive enzyme nitrogenase. Improving the symbiotic effectiveness of crop plants like maize, wheat or rice is a highly topical challenge and could help reduce the need for energy-intense nitrogen fertilizer in staple food production. Root nodule symbiosis (RNS) constitutes one of the most productive nitrogen-fixing systems, but it is restricted to a small group of related angiosperms. Here, we review the genetic regulation of RNS and its interconnections with other plant symbiosis or plant developmental programs. Since RNS uses genetic programs that are widely conserved in land plants, we evaluate the prospects for a transfer to plants that are currently non-nodulating.

Thioacidolysis Marker Compound for Ferulic Acid Incorporation into Angiosperm Lignins (and an Indicator for Cinnamoyl-coenzyme-A Reductase Deficiency

USDA-ARS?s Scientific Manuscript database

A molecular marker compound, derived from lignin by the thioacidolysis degradative method, for structures produced when ferulic acid is incorporated into lignification in angiosperms (poplar, Arabidopsis, tobacco) has been structurally identified as 1,2,2-trithioethyl ethylguaiacol [1-(4-hydroxy-3-m...

Response of western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae), to different release rates of nonhost angiosperm volatiles and verbenone

Treesearch

C.J. Fettig; S.R. McKelvey; C.P. Dabney; R.R. Borys; D.P.W. Huber

2009-01-01

A blend of eight nonhost angiosperm volatiles (benzyl alcohol, benzaldehyde, guaiacol, nonanal, salicylaldehyde, (E)-2-hexenal, (E)-2-hexen-1-ol and (Z)-2-hexen-1-ol) without [NAV] and with [NAVV] (–)-verbenone (4,6,6-trimethylbicyclo[3...

Weak coordination among petiole, leaf, vein, and gas-exchange traits across 41 Australian angiosperm species and its possible implications

USDA-ARS?s Scientific Manuscript database

Background and Aims Close coordination between leaf gas exchange and maximal hydraulic supply has been reported across diverse plant life-forms. However, recent reports suggest that this relationship may become weak or break down completely within the angiosperms. Methods To examine this possi...

Contribution of species-specific chemical signatures to soil organic matter in Kohala, HI.

NASA Astrophysics Data System (ADS)

Stewart, C. E.; Amatangelo, K.; Neff, J. C.

2008-12-01

Soil organic matter (SOM) inherits much of its chemical structure from the dominant vegetation, including phenolic (lignin-derived), aromatic, and aliphatic (cutin and wax-derived) compounds. The Hawaiian fern species Dicranopteris decomposes more slowly than the angiosperm, Cheirodendron due to high concentrations of recalcitrant C compounds. These aliphatic fern leaf waxes are well-preserved and may comprise a large portion of the recalcitrant organic matter in these soils. Our objective was to determine the chemical signature of fern and angiosperm vegetation types and trace the preservation or loss of those compounds into the soil. We collected live tissue, litter, roots, and soil (<53 μm) from five dominant vegetation types including two angiosperms Cheirodendron and Metrosideros, two basal ferns Dicranopteris and Cibotium and a polypod fern Diplazium in Kohala, HI. We characterized them via TMAH-pyrolysis-gas chromatography-mass spectrometry. We found distinct chemical differences between angiosperm and fern vegetation; angiosperm contained more G- and S-derived lignin structures and the fern species contained greater relative abundances of P-derived lignin and tannin-derivatives. There was a general decrease of lignin-derived phenolic compounds from live to litter to soils and an increase in more recalcitrant, aromatic and aliphatic C. Recalcitrant fern-derived cutin and leaf waxes (alkene and alkanes structures) were evident in the soils, but clear species differences were not observed. Although ferns contain distinct lipid and wax-derived compounds, soils developed under fern do not appear to accumulate these compounds in SOM.

Interactions between tectonics, climate and vegetation during the Cretaceous. A context for the diversification of Angiosperms.

NASA Astrophysics Data System (ADS)

Sepulchre, Pierre; Chaboureau, Anne-Claire; Donnadieu, Yannick; Franc, Alain; Ladant, Jean-Baptiste

2017-04-01

It has long been thought that the Angiosperms diversification occurred within a context of warmer-than-present and equable climate during the Cretaceous. However, during the last decade, the view of a uniformely warm Cretaceous climate has been challenged both by paleoclimate proxies and numerical simulations. Among the processes likely affecting climate during this time, atmospheric pCO2 and tectonics appear to be pivotal to drive temperature and precipitation changes, while the feedbacks from vegetation cover changes on the hydrological cycles remain to be explored. Here we attempt to provide a review of the main studies exploring climate-vegetation interactions during the Cretaceous. Then we present climate simulations aiming at quantifying the impact of landmasses redistribution on climate and vegetation distribution from 225 Ma to 70 Ma. In our simulations, the Pangea breakup triggers the decrease of arid belts from the Triassic to the Cretaceous and a subsequent onset of humid conditions during the late Cretaceous. Positioning angiosperm-bearing fossil sites on our paleo-bioclimatic maps confirm that the rise of flowering plants occured within a context of changing climate. With additional simulations in which we modified physiological parameterizations of the vegetation, we explore the combined impact of paleogeography and shift to angiosperms-dominated land surfaces on climate at the regional and global scales. This gives us the opportunity to test earlier ideas that the angiosperms takeover could have benefited from a positive feedback induced by their particular transpiration capacities.

A Southern Hemisphere origin for campanulid angiosperms, with traces of the break-up of Gondwana

PubMed Central

2013-01-01

Background New powerful biogeographic methods have focused attention on long-standing hypotheses regarding the influence of the break-up of Gondwana on the biogeography of Southern Hemisphere plant groups. Studies to date have often concluded that these groups are too young to have been influenced by these ancient continental movements. Here we examine a much larger and older angiosperm clade, the Campanulidae, and infer its biogeographic history by combining Bayesian divergence time information with a likelihood-based biogeographic model focused on the Gondwanan landmasses. Results Our analyses imply that campanulids likely originated in the middle Albian (~105 Ma), and that a substantial portion of the early evolutionary history of campanulids took place in the Southern Hemisphere, despite their greater species richness in the Northern Hemisphere today. We also discovered several disjunctions that show biogeographic and temporal correspondence with the break-up of Gondwana. Conclusions While it is possible to discern traces of the break-up of Gondwana in clades that are old enough, it will generally be difficult to be confident in continental movement as the prime cause of geographic disjunctions. This follows from the need for the geographic disjunction, the inferred biogeographic scenario, and the dating of the lineage splitting events to be consistent with the causal hypothesis. PMID:23565668

Diversification of the phaseoloid legumes: effects of climate change, range expansion and habit shift

PubMed Central

Li, Honglei; Wang, Wei; Lin, Li; Zhu, Xiangyun; Li, Jianhua; Zhu, Xinyu; Chen, Zhiduan

2013-01-01

Understanding which factors have driven the evolutionary success of a group is a fundamental question in biology. Angiosperms are the most successful group in plants and have radiated and adapted to various habitats. Among angiosperms, legumes are a good example for such successful radiation and adaptation. We here investigated how the interplay of past climate changes, geographical expansion and habit shifts has promoted diversification of the phaseoloid legumes, one of the largest clades in the Leguminosae. Using a comprehensive genus-level phylogeny from three plastid markers, we estimate divergence times, infer habit shifts, test the phylogenetic and temporal diversification heterogeneity, and reconstruct ancestral biogeographical ranges. We found that the phaseoloid lineages underwent twice dramatic accumulation. During the Late Oligocene, at least six woody clades rapidly diverged, perhaps in response to the Late Oligocene warming and aridity, and a result of rapidly exploiting new ecological opportunities in Asia, Africa and Australia. The most speciose lineage is herbaceous and began to rapidly diversify since the Early Miocene, which was likely ascribed to arid climates, along with the expansion of seasonally dry tropical forests in Africa, Asia, and America. The phaseoloid group provides an excellent case supporting the idea that the interplay of ecological opportunities and key innovations drives the evolutionary success. PMID:24130564

Diversification of the phaseoloid legumes: effects of climate change, range expansion and habit shift.

PubMed

Li, Honglei; Wang, Wei; Lin, Li; Zhu, Xiangyun; Li, Jianhua; Zhu, Xinyu; Chen, Zhiduan

2013-01-01

Understanding which factors have driven the evolutionary success of a group is a fundamental question in biology. Angiosperms are the most successful group in plants and have radiated and adapted to various habitats. Among angiosperms, legumes are a good example for such successful radiation and adaptation. We here investigated how the interplay of past climate changes, geographical expansion and habit shifts has promoted diversification of the phaseoloid legumes, one of the largest clades in the Leguminosae. Using a comprehensive genus-level phylogeny from three plastid markers, we estimate divergence times, infer habit shifts, test the phylogenetic and temporal diversification heterogeneity, and reconstruct ancestral biogeographical ranges. We found that the phaseoloid lineages underwent twice dramatic accumulation. During the Late Oligocene, at least six woody clades rapidly diverged, perhaps in response to the Late Oligocene warming and aridity, and a result of rapidly exploiting new ecological opportunities in Asia, Africa and Australia. The most speciose lineage is herbaceous and began to rapidly diversify since the Early Miocene, which was likely ascribed to arid climates, along with the expansion of seasonally dry tropical forests in Africa, Asia, and America. The phaseoloid group provides an excellent case supporting the idea that the interplay of ecological opportunities and key innovations drives the evolutionary success.

Differential declines in Alaskan boreal forest vitality related to climate and competition.

PubMed

Trugman, Anna T; Medvigy, David; Anderegg, William R L; Pacala, Stephen W

2018-03-01

Rapid warming and changes in water availability at high latitudes alter resource abundance, tree competition, and disturbance regimes. While these changes are expected to disrupt the functioning of boreal forests, their ultimate implications for forest composition are uncertain. In particular, recent site-level studies of the Alaskan boreal forest have reported both increases and decreases in productivity over the past few decades. Here, we test the idea that variations in Alaskan forest growth and mortality rates are contingent on species composition. Using forest inventory measurements and climate data from plots located throughout interior and south-central Alaska, we show significant growth and mortality responses associated with competition, midsummer vapor pressure deficit, and increased growing season length. The governing climate and competition processes differed substantially across species. Surprisingly, the most dramatic climate response occurred in the drought tolerant angiosperm species, trembling aspen, and linked high midsummer vapor pressure deficits to decreased growth and increased insect-related mortality. Given that species composition in the Alaskan and western Canadian boreal forests is projected to shift toward early-successional angiosperm species due to fire regime, these results underscore the potential for a reduction in boreal productivity stemming from increases in midsummer evaporative demand. © 2017 John Wiley & Sons Ltd.

Comparative analysis of mitochondrial genomes between a wheat K-type cytoplasmic male sterility (CMS) line and its maintainer line.

PubMed

Liu, Huitao; Cui, Peng; Zhan, Kehui; Lin, Qiang; Zhuo, Guoyin; Guo, Xiaoli; Ding, Feng; Yang, Wenlong; Liu, Dongcheng; Hu, Songnian; Yu, Jun; Zhang, Aimin

2011-03-29

Plant mitochondria, semiautonomous organelles that function as manufacturers of cellular ATP, have their own genome that has a slow rate of evolution and rapid rearrangement. Cytoplasmic male sterility (CMS), a common phenotype in higher plants, is closely associated with rearrangements in mitochondrial DNA (mtDNA), and is widely used to produce F1 hybrid seeds in a variety of valuable crop species. Novel chimeric genes deduced from mtDNA rearrangements causing CMS have been identified in several plants, such as rice, sunflower, pepper, and rapeseed, but there are very few reports about mtDNA rearrangements in wheat. In the present work, we describe the mitochondrial genome of a wheat K-type CMS line and compare it with its maintainer line. The complete mtDNA sequence of a wheat K-type (with cytoplasm of Aegilops kotschyi) CMS line, Ks3, was assembled into a master circle (MC) molecule of 647,559 bp and found to harbor 34 known protein-coding genes, three rRNAs (18 S, 26 S, and 5 S rRNAs), and 16 different tRNAs. Compared to our previously published sequence of a K-type maintainer line, Km3, we detected Ks3-specific mtDNA (> 100 bp, 11.38%) and repeats (> 100 bp, 29 units) as well as genes that are unique to each line: rpl5 was missing in Ks3 and trnH was absent from Km3. We also defined 32 single nucleotide polymorphisms (SNPs) in 13 protein-coding, albeit functionally irrelevant, genes, and predicted 22 unique ORFs in Ks3, representing potential candidates for K-type CMS. All these sequence variations are candidates for involvement in CMS. A comparative analysis of the mtDNA of several angiosperms, including those from Ks3, Km3, rice, maize, Arabidopsis thaliana, and rapeseed, showed that non-coding sequences of higher plants had mostly divergent multiple reorganizations during the mtDNA evolution of higher plants. The complete mitochondrial genome of the wheat K-type CMS line Ks3 is very different from that of its maintainer line Km3, especially in non-coding sequences. Sequence rearrangement has produced novel chimeric ORFs, which may be candidate genes for CMS. Comparative analysis of several angiosperm mtDNAs indicated that non-coding sequences are the most frequently reorganized during mtDNA evolution in higher plants.

Natural alcohol exposure: is ethanol the main substrate for alcohol dehydrogenases in animals?

PubMed

Hernández-Tobías, Aída; Julián-Sánchez, Adriana; Piña, Enrique; Riveros-Rosas, Héctor

2011-05-30

Alcohol dehydrogenase (ADH) activity is widely distributed in all phyla. In animals, three non-homologous NAD(P)(+)-dependent ADH protein families are reported. These arose independently throughout evolution and possess different structures and mechanisms of reaction: type I (medium-chain) ADHs are zinc-containing enzymes and comprise the most studied group in vertebrates; type II (short-chain) ADHs lack metal cofactor and have been extensively studied in Drosophila; and type III ADHs are iron-dependent/-activated enzymes that were initially identified only in microorganisms. The presence of these different ADHs in animals has been assumed to be a consequence of chronic exposure to ethanol. By far the most common natural source of ethanol is fermentation of fruit sugars by yeast, and available data support that this fruit trait evolved in concert with the characteristics of their frugivorous seed dispersers. Therefore, if the presence of ADHs in animals evolved as an adaptive response to dietary ethanol exposure, then it can be expected that the enzymogenesis of these enzymes began after the appearance of angiosperms with fleshy fruits, because substrate availability must precede enzyme selection. In this work, available evidence supporting this possibility is discussed. Phylogenetic analyses reveal that type II ADHs suffered several duplications, all of these restricted to flies (order Diptera). Induction of type II Adh by ethanol exposure, a positive correlation between ADH activity and ethanol resistance, and the fact that flies and type II Adh diversification occurred in concert with angiosperm diversification, strongly suggest that type II ADHs were recruited to allow larval flies to exploit new restricted niches with high ethanol content. In contrast, phyletic distribution of types I and III ADHs in animals showed that these appeared before angiosperms and land plants, independently of ethanol availability. Because these enzymes are not induced by ethanol exposure and possess a high affinity and/or catalytic efficiency for non-ethanol endogenous substrates, it can be concluded that the participation of types I and III ADHs in ethanol metabolism can be considered as incidental, and not adaptive. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Insights into evolution in Andean Polystichum (Dryopteridaceae) from expanded understanding of the cytosolic phosphoglucose isomerase gene.

PubMed

Lyons, Brendan M; McHenry, Monique A; Barrington, David S

2017-07-01

Cytosolic phosphoglucose isomerase (pgiC) is an enzyme essential to glycolysis found universally in eukaryotes, but broad understanding of variation in the gene coding for pgiC is lacking for ferns. We used a substantially expanded representation of the gene for Andean species of the fern genus Polystichum to characterize pgiC in ferns relative to angiosperms, insects, and an amoebozoan; assess the impact of selection versus neutral evolutionary processes on pgiC; and explore evolutionary relationships of selected Andean species. The dataset of complete sequences comprised nine accessions representing seven species and one hybrid from the Andes and Serra do Mar. The aligned sequences of the full data set comprised 3376 base pairs (70% of the entire gene) including 17 exons and 15 introns from two central areas of the gene. The exons are highly conserved relative to angiosperms and retain substantial homology to insect pgiC, but intron length and structure are unique to the ferns. Average intron size is similar to angiosperms; intron number and location in insects are unlike those of the plants we considered. The introns included an array of indels and, in intron 7, an extensive microsatellite array with potential utility in analyzing population-level histories. Bayesian and maximum-parsimony analysis of 129 variable nucleotides in the Andean polystichums revealed that 59 (1.7% of the 3376 total) were phylogenetically informative; most of these united sister accessions. The phylogenetic trees for the Andean polystichums were incongruent with previously published cpDNA trees for the same taxa, likely the result of rapid evolutionary change in the introns and contrasting stability in the exons. The exons code a total of seven amino-acid substitutions. Comparison of non-synonymous to synonymous substitutions did not suggest that the pgiC gene is under selection in the Andes. Variation in pgiC including two additional accessions represented by incomplete sequences provided new insights into reticulate relationships among Andean taxa. Copyright © 2017 Elsevier Inc. All rights reserved.

Reconstructing the origin and elaboration of insect-trapping inflorescences in the Araceae1

PubMed Central

Bröderbauer, David; Diaz, Anita; Weber, Anton

2016-01-01

Premise of the study Floral traps are among the most sophisticated devices that have evolved in angiosperms in the context of pollination, but the evolution of trap pollination has not yet been studied in a phylogenetic context. We aim to determine the evolutionary history of morphological traits that facilitate trap pollination and to elucidate the impact of pollinators on the evolution of inflorescence traps in the family Araceae. Methods Inflorescence morphology was investigated to determine the presence of trapping devices and to classify functional types of traps. We inferred phylogenetic relationships in the family using maximum likelihood and Bayesian methods. Character evolution of trapping devices, trap types, and pollinator types was then assessed with maximum parsimony and Bayesian methods. We also tested for an association of trap pollination with specific pollinator types. Key results Inflorescence traps have evolved independently at least 10 times within the Araceae. Trapping devices were found in 27 genera. On the basis of different combinations of trapping devices, six functional types of traps were identified. Trap pollination in Araceae is correlated with pollination by flies. Conclusions Trap pollination in the Araceae is more common than was previously thought. Preadaptations such as papillate cells or elongated sterile flowers facilitated the evolution of inflorescence traps. In some clades, imperfect traps served as a precursor for the evolution of more elaborate traps. Traps that evolved in association with fly pollination were most probably derived from mutualistic ancestors, offering a brood-site to their pollinators. PMID:22965851

Nuclear DNA amounts in angiosperms: progress, problems and prospects.

PubMed

Bennett, M D; Leitch, I J

2005-01-01

The nuclear DNA amount in an unreplicated haploid chromosome complement (1C-value) is a key diversity character with many uses. Angiosperm C-values have been listed for reference purposes since 1976, and pooled in an electronic database since 1997 (http://www.kew.org/cval/homepage). Such lists are cited frequently and provide data for many comparative studies. The last compilation was published in 2000, so a further supplementary list is timely to monitor progress against targets set at the first plant genome size workshop in 1997 and to facilitate new goal setting. The present work lists DNA C-values for 804 species including first values for 628 species from 88 original sources, not included in any previous compilation, plus additional values for 176 species included in a previous compilation. 1998-2002 saw striking progress in our knowledge of angiosperm C-values. At least 1700 first values for species were measured (the most in any five-year period) and familial representation rose from 30 % to 50 %. The loss of many densitometers used to measure DNA C-values proved less serious than feared, owing to the development of relatively inexpensive flow cytometers and computer-based image analysis systems. New uses of the term genome (e.g. in 'complete' genome sequencing) can cause confusion. The Arabidopsis Genome Initiative C-value for Arabidopsis thaliana (125 Mb) was a gross underestimate, and an exact C-value based on genome sequencing alone is unlikely to be obtained soon for any angiosperm. Lack of this expected benchmark poses a quandary as to what to use as the basal calibration standard for angiosperms. The next decade offers exciting prospects for angiosperm genome size research. The database (http://www.kew.org/cval/homepage) should become sufficiently representative of the global flora to answer most questions without needing new estimations. DNA amount variation will remain a key interest as an integrated strand of holistic genomics.

Canopy structure of tropical and sub-tropical rain forests in relation to conifer dominance analysed with a portable LIDAR system

PubMed Central

Aiba, Shin-ichiro; Akutsu, Kosuke; Onoda, Yusuke

2013-01-01

Background and Aims Globally, conifer dominance is restricted to nutient-poor habitats in colder, drier or waterlogged environments, probably due to competition with angiosperms. Analysis of canopy structure is important for understanding the mechanism of plant coexistence in relation to competition for light. Most conifers are shade intolerant, and often have narrow, deep, conical crowns. In this study it is predicted that conifer-admixed forests have less distinct upper canopies and more undulating canopy surfaces than angiosperm-dominated forests. Methods By using a ground-based, portable light detection and ranging (LIDAR) system, canopy structure was quantified for old-growth evergreen rainforests with varying dominance of conifers along altitudinal gradients (200–3100 m a.s.l.) on tropical and sub-tropical mountains (Mount Kinabalu, Malaysian Borneo and Yakushima Island, Japan) that have different conifer floras. Key Results Conifers dominated at higher elevations on both mountains (Podocarpaceae and Araucariaceae on Kinabalu and Cupressaceae and Pinaceae on Yakushima), but conifer dominance also varied with soil/substrate conditions on Kinabalu. Conifer dominance was associated with the existence of large-diameter conifers. Forests with higher conifer dominance showed a canopy height profile (CHP) more skewed towards the understorey on both Kinabalu and Yakushima. In contrast, angiosperm-dominated forests had a CHP skewed towards upper canopy, except for lowland dipterocarp forests and a sub-alpine scrub dominated by small-leaved Leptospermum recurvum (Myrtaceae) on Kinabalu. Forests with a less dense upper canopy had more undulating outer canopy surfaces. Mixed conifer–angiosperm forests on Yakushima and dipterocarp forests on Kinabalu showed similar canopy structures. Conclusions The results generally supported the prediction, suggesting that lower growth of angiosperm trees (except L. recurvum on Kinabalu) in cold and nutrient-poor environments results in a sparser upper canopy, which allows shade-intolerant conifers to co-occur with angiosperm trees either as emergents or as codominants in the open canopy. PMID:24197751

Conifers, angiosperm trees, and lianas: growth, whole-plant water and nitrogen use efficiency, and stable isotope composition ({delta}13C and {delta}18O) of seedlings grown in a tropical environment.

PubMed

Cernusak, Lucas A; Winter, Klaus; Aranda, Jorge; Turner, Benjamin L

2008-09-01

Seedlings of several species of gymnosperm trees, angiosperm trees, and angiosperm lianas were grown under tropical field conditions in the Republic of Panama; physiological processes controlling plant C and water fluxes were assessed across this functionally diverse range of species. Relative growth rate, r, was primarily controlled by the ratio of leaf area to plant mass, of which specific leaf area was a key component. Instantaneous photosynthesis, when expressed on a leaf-mass basis, explained 69% of variation in r (P < 0.0001, n = 94). Mean r of angiosperms was significantly higher than that of the gymnosperms; within angiosperms, mean r of lianas was higher than that of trees. Whole-plant nitrogen use efficiency was also significantly higher in angiosperm than in gymnosperm species, and was primarily controlled by the rate of photosynthesis for a given amount of leaf nitrogen. Whole-plant water use efficiency, TE(c), varied significantly among species, and was primarily controlled by c(i)/c(a), the ratio of intercellular to ambient CO(2) partial pressures during photosynthesis. Instantaneous measurements of c(i)/c(a) explained 51% of variation in TE(c) (P < 0.0001, n = 94). Whole-plant (13)C discrimination also varied significantly as a function of c(i)/c(a) (R(2) = 0.57, P < 0.0001, n = 94), and was, accordingly, a good predictor of TE(c). The (18)O enrichment of stem dry matter was primarily controlled by the predicted (18)O enrichment of evaporative sites within leaves (R(2) = 0.61, P < 0.0001, n = 94), with some residual variation explained by mean transpiration rate. Measurements of carbon and oxygen stable isotope ratios could provide a useful means of parameterizing physiological models of tropical forest trees.

Two tropical conifers show strong growth and water-use efficiency responses to altered CO2 concentration

PubMed Central

Dalling, James W.; Cernusak, Lucas A.; Winter, Klaus; Aranda, Jorge; Garcia, Milton; Virgo, Aurelio; Cheesman, Alexander W.; Baresch, Andres; Jaramillo, Carlos; Turner, Benjamin L.

2016-01-01

Background and Aims Conifers dominated wet lowland tropical forests 100 million years ago (MYA). With a few exceptions in the Podocarpaceae and Araucariaceae, conifers are now absent from this biome. This shift to angiosperm dominance also coincided with a large decline in atmospheric CO2 concentration (ca). We compared growth and physiological performance of two lowland tropical angiosperms and conifers at ca levels representing pre-industrial (280 ppm), ambient (400 ppm) and Eocene (800 ppm) conditions to explore how differences in ca affect the growth and water-use efficiency (WUE) of seedlings from these groups. Methods Two conifers (Araucaria heterophylla and Podocarpus guatemalensis) and two angiosperm trees (Tabebuia rosea and Chrysophyllum cainito) were grown in climate-controlled glasshouses in Panama. Growth, photosynthetic rates, nutrient uptake, and nutrient use and water-use efficiencies were measured. Key Results Podocarpus seedlings showed a stronger (66 %) increase in relative growth rate with increasing ca relative to Araucaria (19 %) and the angiosperms (no growth enhancement). The response of Podocarpus is consistent with expectations for species with conservative growth traits and low mesophyll diffusion conductance. While previous work has shown limited stomatal response of conifers to ca, we found that the two conifers had significantly greater increases in leaf and whole-plant WUE than the angiosperms, reflecting increased photosynthetic rate and reduced stomatal conductance. Foliar nitrogen isotope ratios (δ15N) and soil nitrate concentrations indicated a preference in Podocarpus for ammonium over nitrate, which may impact nitrogen uptake relative to nitrate assimilators under high ca. Significance Podocarps colonized tropical forests after angiosperms achieved dominance and are now restricted to infertile soils. Although limited to a single species, our data suggest that higher ca may have been favourable for podocarp colonization of tropical South America 60 MYA, while plasticity in photosynthetic capacity and WUE may help account for their continued persistence under large changes in ca since the Eocene. PMID:27582361

Canopy structure of tropical and sub-tropical rain forests in relation to conifer dominance analysed with a portable LIDAR system.

PubMed

Aiba, Shin-ichiro; Akutsu, Kosuke; Onoda, Yusuke

2013-12-01

Globally, conifer dominance is restricted to nutient-poor habitats in colder, drier or waterlogged environments, probably due to competition with angiosperms. Analysis of canopy structure is important for understanding the mechanism of plant coexistence in relation to competition for light. Most conifers are shade intolerant, and often have narrow, deep, conical crowns. In this study it is predicted that conifer-admixed forests have less distinct upper canopies and more undulating canopy surfaces than angiosperm-dominated forests. By using a ground-based, portable light detection and ranging (LIDAR) system, canopy structure was quantified for old-growth evergreen rainforests with varying dominance of conifers along altitudinal gradients (200-3100 m a.s.l.) on tropical and sub-tropical mountains (Mount Kinabalu, Malaysian Borneo and Yakushima Island, Japan) that have different conifer floras. Conifers dominated at higher elevations on both mountains (Podocarpaceae and Araucariaceae on Kinabalu and Cupressaceae and Pinaceae on Yakushima), but conifer dominance also varied with soil/substrate conditions on Kinabalu. Conifer dominance was associated with the existence of large-diameter conifers. Forests with higher conifer dominance showed a canopy height profile (CHP) more skewed towards the understorey on both Kinabalu and Yakushima. In contrast, angiosperm-dominated forests had a CHP skewed towards upper canopy, except for lowland dipterocarp forests and a sub-alpine scrub dominated by small-leaved Leptospermum recurvum (Myrtaceae) on Kinabalu. Forests with a less dense upper canopy had more undulating outer canopy surfaces. Mixed conifer-angiosperm forests on Yakushima and dipterocarp forests on Kinabalu showed similar canopy structures. The results generally supported the prediction, suggesting that lower growth of angiosperm trees (except L. recurvum on Kinabalu) in cold and nutrient-poor environments results in a sparser upper canopy, which allows shade-intolerant conifers to co-occur with angiosperm trees either as emergents or as codominants in the open canopy.

In Planta Recapitulation of Isoprene Synthase Evolution from Ocimene Synthases

PubMed Central

Li, Mingai; Xu, Jia; Algarra Alarcon, Alberto; Carlin, Silvia; Barbaro, Enrico; Cappellin, Luca; Velikova, Violeta; Vrhovsek, Urska; Loreto, Francesco; Varotto, Claudio

2017-01-01

Abstract Isoprene is the most abundant biogenic volatile hydrocarbon compound naturally emitted by plants and plays a major role in atmospheric chemistry. It has been proposed that isoprene synthases (IspS) may readily evolve from other terpene synthases, but this hypothesis has not been experimentally investigated. We isolated and functionally validated in Arabidopsis the first isoprene synthase gene, AdoIspS, from a monocotyledonous species (Arundo donax L., Poaceae). Phylogenetic reconstruction indicates that AdoIspS and dicots isoprene synthases most likely originated by parallel evolution from TPS-b monoterpene synthases. Site-directed mutagenesis demonstrated invivo the functional and evolutionary relevance of the residues considered diagnostic for IspS function. One of these positions was identified by saturating mutagenesis as a major determinant of substrate specificity in AdoIspS able to cause invivo a dramatic change in total volatile emission from hemi- to monoterpenes and supporting evolution of isoprene synthases from ocimene synthases. The mechanism responsible for IspS neofunctionalization by active site size modulation by a single amino acid mutation demonstrated in this study might be general, as the very same amino acidic position is implicated in the parallel evolution of different short-chain terpene synthases from both angiosperms and gymnosperms. Based on these results, we present a model reconciling in a unified conceptual framework the apparently contrasting patterns previously observed for isoprene synthase evolution in plants. These results indicate that parallel evolution may be driven by relatively simple biophysical constraints, and illustrate the intimate molecular evolutionary links between the structural and functional bases of traits with global relevance. PMID:28637270

Recapitulating the Structural Evolution of Redox Regulation in Adenosine 5'-Phosphosulfate Kinase from Cyanobacteria to Plants.

PubMed

Herrmann, Jonathan; Nathin, David; Lee, Soon Goo; Sun, Tony; Jez, Joseph M

2015-10-09

In plants, adenosine 5'-phosphosulfate (APS) kinase (APSK) is required for reproductive viability and the production of 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as a sulfur donor in specialized metabolism. Previous studies of the APSK from Arabidopsis thaliana (AtAPSK) identified a regulatory disulfide bond formed between the N-terminal domain (NTD) and a cysteine on the core scaffold. This thiol switch is unique to mosses, gymnosperms, and angiosperms. To understand the structural evolution of redox control of APSK, we investigated the redox-insensitive APSK from the cyanobacterium Synechocystis sp. PCC 6803 (SynAPSK). Crystallographic analysis of SynAPSK in complex with either APS and a non-hydrolyzable ATP analog or APS and sulfate revealed the overall structure of the enzyme, which lacks the NTD found in homologs from mosses and plants. A series of engineered SynAPSK variants reconstructed the structural evolution of the plant APSK. Biochemical analyses of SynAPSK, SynAPSK H23C mutant, SynAPSK fused to the AtAPSK NTD, and the fusion protein with the H23C mutation showed that the addition of the NTD and cysteines recapitulated thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox control of APSK in the green lineage from cyanobacteria to plants. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Transcriptome comparisons shed light on the pre-condition and potential barrier for C4 photosynthesis evolution in eudicots.

PubMed

Tao, Yimin; Lyu, Ming-Ju Amy; Zhu, Xin-Guang

2016-05-01

C4 photosynthesis evolved independently from C3 photosynthesis in more than 60 lineages. Most of the C4 lineages are clustered together in the order Poales and the order Caryophyllales while many other angiosperm orders do not have C4 species, suggesting the existence of biological pre-conditions in the ancestral C3 species that facilitate the evolution of C4 photosynthesis in these lineages. To explore pre-adaptations for C4 photosynthesis evolution, we classified C4 lineages into the C4-poor and the C4-rich groups based on the percentage of C4 species in different genera and conducted a comprehensive comparison on the transcriptomic changes between the non-C4 species from the C4-poor and the C4-rich groups. Results show that species in the C4-rich group showed higher expression of genes related to oxidoreductase activity, light reaction components, terpene synthesis, secondary cell synthesis, C4 cycle related genes and genes related to nucleotide metabolism and senescence. In contrast, C4-poor group showed up-regulation of a PEP/Pi translocator, genes related to signaling pathway, stress response, defense response and plant hormone metabolism (ethylene and brassinosteroid). The implications of these transcriptomic differences between the C4-rich and C4-poor groups to C4 evolution are discussed.

First evidence for Wollemi Pine-type pollen (Dilwynites: Araucariaceae) in South America.

PubMed

Macphail, Mike; Carpenter, Raymond J; Iglesias, Ari; Wilf, Peter

2013-01-01

We report the first fossil pollen from South America of the lineage that includes the recently discovered, extremely rare Australian Wollemi Pine, Wollemia nobilis (Araucariaceae). The grains are from the late Paleocene to early middle Eocene Ligorio Márquez Formation of Santa Cruz, Patagonia, Argentina, and are assigned to Dilwynites, the fossil pollen type that closely resembles the pollen of modern Wollemia and some species of its Australasian sister genus, Agathis. Dilwynites was formerly known only from Australia, New Zealand, and East Antarctica. The Patagonian Dilwynites occurs with several taxa of Podocarpaceae and a diverse range of cryptogams and angiosperms, but not Nothofagus. The fossils greatly extend the known geographic range of Dilwynites and provide important new evidence for the Antarctic region as an early Paleogene portal for biotic interchange between Australasia and South America.

First Evidence for Wollemi Pine-type Pollen (Dilwynites: Araucariaceae) in South America

PubMed Central

Macphail, Mike; Carpenter, Raymond J.; Iglesias, Ari; Wilf, Peter

2013-01-01

We report the first fossil pollen from South America of the lineage that includes the recently discovered, extremely rare Australian Wollemi Pine, Wollemia nobilis (Araucariaceae). The grains are from the late Paleocene to early middle Eocene Ligorio Márquez Formation of Santa Cruz, Patagonia, Argentina, and are assigned to Dilwynites, the fossil pollen type that closely resembles the pollen of modern Wollemia and some species of its Australasian sister genus, Agathis. Dilwynites was formerly known only from Australia, New Zealand, and East Antarctica. The Patagonian Dilwynites occurs with several taxa of Podocarpaceae and a diverse range of cryptogams and angiosperms, but not Nothofagus. The fossils greatly extend the known geographic range of Dilwynites and provide important new evidence for the Antarctic region as an early Paleogene portal for biotic interchange between Australasia and South America. PMID:23894439

Alternative electron transport mediated by flavodiiron proteins is operational in organisms from cyanobacteria up to gymnosperms.

PubMed

Ilík, Petr; Pavlovič, Andrej; Kouřil, Roman; Alboresi, Alessandro; Morosinotto, Tomas; Allahverdiyeva, Yagut; Aro, Eva-Mari; Yamamoto, Hiroshi; Shikanai, Toshiharu

2017-05-01

Photo-reduction of O 2 to water mediated by flavodiiron proteins (FDPs) represents a safety valve for the photosynthetic electron transport chain in fluctuating light. So far, the FDP-mediated O 2 photo-reduction has been evidenced only in cyanobacteria and the moss Physcomitrella; however, a recent phylogenetic analysis of transcriptomes of photosynthetic organisms has also revealed the presence of FDP genes in several nonflowering plant groups. What remains to be clarified is whether the FDP-dependent O 2 photo-reduction is actually operational in these organisms. We have established a simple method for the monitoring of FDP-mediated O 2 photo-reduction, based on the measurement of redox kinetics of P700 (the electron donor of photosystem I) upon dark-to-light transition. The O 2 photo-reduction is manifested as a fast re-oxidation of P700. The validity of the method was verified by experiments with transgenic organisms, namely FDP knock-out mutants of Synechocystis and Physcomitrella and transgenic Arabidopsis plants expressing FDPs from Physcomitrella. We observed the fast P700 re-oxidation in representatives of all green plant groups excluding angiosperms. Our results provide strong evidence that the FDP-mediated O 2 photo-reduction is functional in all nonflowering green plant groups. This finding suggests a major change in the strategy of photosynthetic regulation during the evolution of angiosperms. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

A Paleocene lowland macroflora from Patagonia reveals significantly greater richness than North American analogs

NASA Astrophysics Data System (ADS)

Iglesias, Ari; Wilf, Peter; Johnson, Kirk R.; Zamuner, Alba B.; Rubén Cúneo, N.; Matheos, Sergio D.; Singer, Bradley S.

2007-10-01

Few South American macrofloras of Paleocene age are known, and this limits our knowledge of diversity and composition between the end-Cretaceous event and the Eocene appearance of high floral diversity. We report new, unbiased collections of 2516 compression specimens from the Paleocene Salamanca Formation (ca. 61.7 Ma) from two localities in the Palacio de los Loros exposures in southern Chubut, Patagonia, Argentina. Our samples reveal considerably greater richness than was previously known from the Paleocene of Patagonia, including 36 species of angiosperm leaves as well as angiosperm fruits, flowers, and seeds; ferns; and conifer leaves, cones, and seeds. The floras, which are from siltstone and sandstone channel-fills deposited on low-relief floodplain landscapes in a humid, warm temperate climate, are climatically and paleoenvironmentally comparable to many quantitatively collected Paleocene floras from the Western Interior of North America. Adjusted for sample size, there are >50% more species at each Palacio de los Loros quarry than in any comparable U.S. Paleocene sample. These results indicate more vibrant terrestrial ecosystems in Patagonian than in North American floodplain environments ˜4 m.y. after the end-Cretaceous extinction, and they push back the time line 10 m.y. for the evolution of high floral diversity in South America. The cause of the dis parity is unknown but could involve reduced impact effects because of greater distance from the Chicxulub site, higher latest Cretaceous diversity, or faster recovery or immigration rates.

Use of DNA barcodes to identify flowering plants

PubMed Central

Kress, W. John; Wurdack, Kenneth J.; Zimmer, Elizabeth A.; Weigt, Lee A.; Janzen, Daniel H.

2005-01-01

Methods for identifying species by using short orthologous DNA sequences, known as “DNA barcodes,” have been proposed and initiated to facilitate biodiversity studies, identify juveniles, associate sexes, and enhance forensic analyses. The cytochrome c oxidase 1 sequence, which has been found to be widely applicable in animal barcoding, is not appropriate for most species of plants because of a much slower rate of cytochrome c oxidase 1 gene evolution in higher plants than in animals. We therefore propose the nuclear internal transcribed spacer region and the plastid trnH-psbA intergenic spacer as potentially usable DNA regions for applying barcoding to flowering plants. The internal transcribed spacer is the most commonly sequenced locus used in plant phylogenetic investigations at the species level and shows high levels of interspecific divergence. The trnH-psbA spacer, although short (≈450-bp), is the most variable plastid region in angiosperms and is easily amplified across a broad range of land plants. Comparison of the total plastid genomes of tobacco and deadly nightshade enhanced with trials on widely divergent angiosperm taxa, including closely related species in seven plant families and a group of species sampled from a local flora encompassing 50 plant families (for a total of 99 species, 80 genera, and 53 families), suggest that the sequences in this pair of loci have the potential to discriminate among the largest number of plant species for barcoding purposes. PMID:15928076

Comparative development of rare cases of a polycarpellate gynoecium in an otherwise monocarpellate family, Leguminosae.

PubMed

Paulino, Juliana Villela; Prenner, Gerhard; Mansano, Vidal Freitas; Teixeira, Simone Pádua

2014-04-01

Apocarpy (i.e., free carpels) is considered to be the basal condition for ovary development in angiosperms. Yet it only occurs in 10% of angiosperm species, of which another 10% are monocarpellate. Most legume flowers are monocarpellate. Species with polycarpellate gynoecia occur in about 15 genera with most representatives in Mimosoideae. In the present study, we analyze legumes with polycarpellate flowers with the aim of improving our understanding of gynoecium evolution. Flowers of nine legume species from five genera were analyzed using a scanning electron microscope (SEM). In Leguminosae, carpels usually form as individual primordia or protuberances. Inga congesta differs slightly from this pattern in that the central apex bulges outward before the formation of individual carpel primordia. While legumes usually develop entirely plicate carpels, flowers of Acacia celastrifolia and Inga bella show an intermediate type of carpel morphology with a distal plicate zone and a small proximal ascidiate zone. Carpels in Inga congesta and Archidendron glabrum are sometimes slightly fused at the ovary base. The orientation of carpel clefts seems to reflect the floral symmetry. They are directed to the floral center in mimosoids and caesalpinioids, whereas in Swartzia dipetala carpel clefts are oriented to the adaxial side. Polycarpelly arose at least seven times independently in Leguminosae. The polycarpellate condition appears to be correlated with polyandry, and in most instances, it is accompanied by a profound change in floral organization from a closed to an open system.

Mitochondrial genome sequencing helps show the evolutionary mechanism of mitochondrial genome formation in Brassica

PubMed Central

2011-01-01

Background Angiosperm mitochondrial genomes are more complex than those of other organisms. Analyses of the mitochondrial genome sequences of at least 11 angiosperm species have showed several common properties; these cannot easily explain, however, how the diverse mitotypes evolved within each genus or species. We analyzed the evolutionary relationships of Brassica mitotypes by sequencing. Results We sequenced the mitotypes of cam (Brassica rapa), ole (B. oleracea), jun (B. juncea), and car (B. carinata) and analyzed them together with two previously sequenced mitotypes of B. napus (pol and nap). The sizes of whole single circular genomes of cam, jun, ole, and car are 219,747 bp, 219,766 bp, 360,271 bp, and 232,241 bp, respectively. The mitochondrial genome of ole is largest as a resulting of the duplication of a 141.8 kb segment. The jun mitotype is the result of an inherited cam mitotype, and pol is also derived from the cam mitotype with evolutionary modifications. Genes with known functions are conserved in all mitotypes, but clear variation in open reading frames (ORFs) with unknown functions among the six mitotypes was observed. Sequence relationship analysis showed that there has been genome compaction and inheritance in the course of Brassica mitotype evolution. Conclusions We have sequenced four Brassica mitotypes, compared six Brassica mitotypes and suggested a mechanism for mitochondrial genome formation in Brassica, including evolutionary events such as inheritance, duplication, rearrangement, genome compaction, and mutation. PMID:21988783

Orchid phylogenomics and multiple drivers of their extraordinary diversification

PubMed Central

Givnish, Thomas J.; Spalink, Daniel; Ames, Mercedes; Lyon, Stephanie P.; Hunter, Steven J.; Zuluaga, Alejandro; Iles, William J. D.; Clements, Mark A.; Arroyo, Mary T. K.; Leebens-Mack, James; Endara, Lorena; Kriebel, Ricardo; Neubig, Kurt M.; Whitten, W. Mark; Williams, Norris H.; Cameron, Kenneth M.

2015-01-01

Orchids are the most diverse family of angiosperms, with over 25 000 species, more than mammals, birds and reptiles combined. Tests of hypotheses to account for such diversity have been stymied by the lack of a fully resolved broad-scale phylogeny. Here, we provide such a phylogeny, based on 75 chloroplast genes for 39 species representing all orchid subfamilies and 16 of 17 tribes, time-calibrated against 17 angiosperm fossils. A supermatrix analysis places an additional 144 species based on three plastid genes. Orchids appear to have arisen roughly 112 million years ago (Mya); the subfamilies Orchidoideae and Epidendroideae diverged from each other at the end of the Cretaceous; and the eight tribes and three previously unplaced subtribes of the upper epidendroids diverged rapidly from each other between 37.9 and 30.8 Mya. Orchids appear to have undergone one significant acceleration of net species diversification in the orchidoids, and two accelerations and one deceleration in the upper epidendroids. Consistent with theory, such accelerations were correlated with the evolution of pollinia, the epiphytic habit, CAM photosynthesis, tropical distribution (especially in extensive cordilleras), and pollination via Lepidoptera or euglossine bees. Deceit pollination appears to have elevated the number of orchid species by one-half but not via acceleration of the rate of net diversification. The highest rate of net species diversification within the orchids (0.382 sp sp−1 My−1) is 6.8 times that at the Asparagales crown. PMID:26311671

In Planta Recapitulation of Isoprene Synthase Evolution from Ocimene Synthases.

PubMed

Li, Mingai; Xu, Jia; Algarra Alarcon, Alberto; Carlin, Silvia; Barbaro, Enrico; Cappellin, Luca; Velikova, Violeta; Vrhovsek, Urska; Loreto, Francesco; Varotto, Claudio

2017-10-01

Isoprene is the most abundant biogenic volatile hydrocarbon compound naturally emitted by plants and plays a major role in atmospheric chemistry. It has been proposed that isoprene synthases (IspS) may readily evolve from other terpene synthases, but this hypothesis has not been experimentally investigated. We isolated and functionally validated in Arabidopsis the first isoprene synthase gene, AdoIspS, from a monocotyledonous species (Arundo donax L., Poaceae). Phylogenetic reconstruction indicates that AdoIspS and dicots isoprene synthases most likely originated by parallel evolution from TPS-b monoterpene synthases. Site-directed mutagenesis demonstrated invivo the functional and evolutionary relevance of the residues considered diagnostic for IspS function. One of these positions was identified by saturating mutagenesis as a major determinant of substrate specificity in AdoIspS able to cause invivo a dramatic change in total volatile emission from hemi- to monoterpenes and supporting evolution of isoprene synthases from ocimene synthases. The mechanism responsible for IspS neofunctionalization by active site size modulation by a single amino acid mutation demonstrated in this study might be general, as the very same amino acidic position is implicated in the parallel evolution of different short-chain terpene synthases from both angiosperms and gymnosperms. Based on these results, we present a model reconciling in a unified conceptual framework the apparently contrasting patterns previously observed for isoprene synthase evolution in plants. These results indicate that parallel evolution may be driven by relatively simple biophysical constraints, and illustrate the intimate molecular evolutionary links between the structural and functional bases of traits with global relevance. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Evolution of strigolactone receptors by gradual neo-functionalization of KAI2 paralogues.

PubMed

Bythell-Douglas, Rohan; Rothfels, Carl J; Stevenson, Dennis W D; Graham, Sean W; Wong, Gane Ka-Shu; Nelson, David C; Bennett, Tom

2017-06-29

Strigolactones (SLs) are a class of plant hormones that control many aspects of plant growth. The SL signalling mechanism is homologous to that of karrikins (KARs), smoke-derived compounds that stimulate seed germination. In angiosperms, the SL receptor is an α/β-hydrolase known as DWARF14 (D14); its close homologue, KARRIKIN INSENSITIVE2 (KAI2), functions as a KAR receptor and likely recognizes an uncharacterized, endogenous signal ('KL'). Previous phylogenetic analyses have suggested that the KAI2 lineage is ancestral in land plants, and that canonical D14-type SL receptors only arose in seed plants; this is paradoxical, however, as non-vascular plants synthesize and respond to SLs. We have used a combination of phylogenetic and structural approaches to re-assess the evolution of the D14/KAI2 family in land plants. We analysed 339 members of the D14/KAI2 family from land plants and charophyte algae. Our phylogenetic analyses show that the divergence between the eu-KAI2 lineage and the DDK (D14/DLK2/KAI2) lineage that includes D14 occurred very early in land plant evolution. We show that eu-KAI2 proteins are highly conserved, and have unique features not found in DDK proteins. Conversely, we show that DDK proteins show considerable sequence and structural variation to each other, and lack clearly definable characteristics. We use homology modelling to show that the earliest members of the DDK lineage structurally resemble KAI2 and that SL receptors in non-seed plants likely do not have D14-like structure. We also show that certain groups of DDK proteins lack the otherwise conserved MORE AXILLARY GROWTH2 (MAX2) interface, and may thus function independently of MAX2, which we show is highly conserved throughout land plant evolution. Our results suggest that D14-like structure is not required for SL perception, and that SL perception has relatively relaxed structural requirements compared to KAI2-mediated signalling. We suggest that SL perception gradually evolved by neo-functionalization within the DDK lineage, and that the transition from KAI2-like to D14-like protein may have been driven by interactions with protein partners, rather than being required for SL perception per se.

Arctic plant diversity in the Early Eocene greenhouse

PubMed Central

Harrington, Guy J.; Eberle, Jaelyn; Le-Page, Ben A.; Dawson, Mary; Hutchison, J. Howard

2012-01-01

For the majority of the Early Caenozoic, a remarkable expanse of humid, mesothermal to temperate forests spread across Northern Polar regions that now contain specialized plant and animal communities adapted to life in extreme environments. Little is known on the taxonomic diversity of Arctic floras during greenhouse periods of the Caenozoic. We show for the first time that plant richness in the globally warm Early Eocene (approx. 55–52 Myr) in the Canadian High Arctic (76° N) is comparable with that approximately 3500 km further south at mid-latitudes in the US western interior (44–47° N). Arctic Eocene pollen floras are most comparable in richness with today's forests in the southeastern United States, some 5000 km further south of the Arctic. Nearly half of the Eocene, Arctic plant taxa are endemic and the richness of pollen floras implies significant patchiness to the vegetation type and clear regional richness of angiosperms. The reduced latitudinal diversity gradient in Early Eocene North American plant species demonstrates that extreme photoperiod in the Arctic did not limit taxonomic diversity of plants. PMID:22072610

Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Denis, E. H.; Pedentchouk, N.; Schouten, S.; Pagani, M.; Freeman, K. H.

2016-12-01

Fire, an important component of ecosystems at a range of spatial and temporal scales, affects vegetation distribution, the carbon cycle, and climate. In turn, climate influences fuel composition (e.g., amount and type of vegetation), fuel availability (e.g., vegetation that can burn based on precipitation and temperature), and ignition sources (e.g., lightning). Climate studies predict increased wildfire activity in future decades, but mechanisms that control the relationship between climate and fire are complex. Reconstructing environmental conditions during past warming events (e.g., the Paleocene-Eocene Thermal Maximum (PETM)) will help elucidate climate-vegetation-fire relationships that are expressed over long durations (1,000 - 10,000 yrs). The abrupt global warming during the PETM dramatically altered vegetation and hydrologic patterns, and, possibly, fire occurrence. To investigate coincident changes in climate, vegetation, and fire occurrence, we studied biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes from the PETM interval at IODP site 302 (the Lomonosov Ridge) in the Arctic Ocean. Both pollen and biomarker records indicate angiosperms abundance increased during the PETM relative to gymnosperms, reflecting a significant ecological shift to angiosperm-dominated vegetation. PAH abundances increased relative to plant biomarkers throughout the PETM, which suggests PAH production increased relative to plant productivity. Increased PAH production associated with the angiosperm vegetation shift indicates a greater prevalence of more fire-prone species. A time lag between increased moisture transport (based on published δD of n-alkanes data) to the Arctic and increased angiosperms and PAH production suggests wetter conditions, followed by increased air temperatures, favored angiosperms and combined to enhance fire occurrence.

Impact of whole-genome duplication events on diversification rates in angiosperms.

PubMed

Landis, Jacob B; Soltis, Douglas E; Li, Zheng; Marx, Hannah E; Barker, Michael S; Tank, David C; Soltis, Pamela S

2018-03-01

Polyploidy or whole-genome duplication (WGD) pervades the evolutionary history of angiosperms. Despite extensive progress in our understanding of WGD, the role of these events in promoting diversification is still not well understood. We seek to clarify the possible association between WGD and diversification rates in flowering plants. Using a previously published phylogeny spanning all land plants (31,749 tips) and WGD events inferred from analyses of the 1000 Plants (1KP) transcriptome data, we analyzed the association of WGDs and diversification rates following numerous WGD events across the angiosperms. We used a stepwise AIC approach (MEDUSA), a Bayesian mixture model approach (BAMM), and state-dependent diversification analyses (MuSSE) to investigate patterns of diversification. Sister-clade comparisons were used to investigate species richness after WGDs. Based on the density of 1KP taxon sampling, 106 WGDs were unambiguously placed on the angiosperm phylogeny. We identified 334-530 shifts in diversification rates. We found that 61 WGD events were tightly linked to changes in diversification rates, and state-dependent diversification analyses indicated higher speciation rates for subsequent rounds of WGD. Additionally, 70 of 99 WGD events showed an increase in species richness compared to the sister clade. Forty-six of the 106 WGDs analyzed appear to be closely associated with upshifts in the rate of diversification in angiosperms. Shifts in diversification do not appear more likely than random within a four-node lag phase following a WGD; however, younger WGD events are more likely to be followed by an upshift in diversification than older WGD events. © 2018 Botanical Society of America.

Comparative analysis of pistil transcriptomes reveals conserved and novel genes expressed in dry, wet, and semidry stigmas.

PubMed

Allen, Alexandra M; Lexer, Christian; Hiscock, Simon J

2010-11-01

Fertilization in angiosperms depends on a complex cellular "courtship" between haploid pollen and diploid pistil. These pollen-pistil interactions are regulated by a diversity of molecules, many of which remain to be identified and characterized. Thus, it is unclear to what extent these processes are conserved among angiosperms, a fact confounded by limited sampling across taxa. Here, we report the analysis of pistil-expressed genes in Senecio squalidus (Asteraceae), a species from euasterid II, a major clade for which there are currently no data on pistil-expressed genes. Species from the Asteraceae characteristically have a "semidry stigma," intermediate between the "wet" and "dry" stigmas typical of the majority of angiosperms. Construction of pistil-enriched cDNA libraries for S. squalidus allowed us to address two hypotheses: (1) stigmas of S. squalidus will express genes common to wet and dry stigmas and genes specific to the semidry stigma characteristic of the Asteraceae; and (2) genes potentially essential for pistil function will be conserved between diverse angiosperm groups and therefore common to all currently available pistil transcriptome data sets, including S. squalidus. Our data support both these hypotheses. The S. squalidus pistil transcriptome contains novel genes and genes previously identified in pistils of species with dry stigmas and wet stigmas. Comparative analysis of the five pistil transcriptomes currently available (Oryza sativa, Crocus sativus, Arabidopsis thaliana, Nicotiana tabacum, and S. squalidus), representing four major angiosperm clades and the three stigma states, identified novel genes and conserved genes potentially regulating pollen-pistil interaction pathways common to monocots and eudicots.

Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display.

PubMed

Lusk, Christopher H; Pérez-Millaqueo, Manuel M; Saldaña, Alfredo; Burns, Bruce R; Laughlin, Daniel C; Falster, Daniel S

2012-07-01

The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers. This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LAR(d)) was used to indicate plant light interception potential: LAR(d) is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle. Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LAR(d) was about twice that of conifers. Although specific leaf area was the most pervasive influence on LAR(d), differences in self-shading also significantly influenced LAR(d) of large seedlings. The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition.

Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display

PubMed Central

Lusk, Christopher H.; Pérez-Millaqueo, Manuel M.; Saldaña, Alfredo; Burns, Bruce R.; Laughlin, Daniel C.; Falster, Daniel S.

2012-01-01

Background and Aims The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers. Methods This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LARd) was used to indicate plant light interception potential: LARd is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle. Results Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LARd was about twice that of conifers. Although specific leaf area was the most pervasive influence on LARd, differences in self-shading also significantly influenced LARd of large seedlings. Conclusions The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition. PMID:22585929

Hydraulic safety margins and embolism reversal in stems and leaves: Why are conifers and angiosperms so different?

Treesearch

Daniel M. Johnson; Katherine A. McCulloh; David R. Woodruff; Frederick C. Meinzer

2012-01-01

Angiosperm and coniferous tree species utilize a continuum of hydraulic strategies. Hydraulic safety margins (defined as differences between naturally occurring xylem pressures and pressures that would cause hydraulic dysfunction, or differences between pressures resulting in loss of hydraulic function in adjacent organs (e.g., stems vs. leaves) tend to be much greater...

Nonhost angiosperm volatiles and verbenone protect individual ponderosa pines from attack by western pine beetle and red turpentine beetle (Coleoptera: Curculionidae, Scolytinae)

Treesearch

Christopher J. Fettig; Christopher P. Dabney; Stepehen R. McKelvey; Dezene P.W. Huber

2008-01-01

Nonhost angiosperm volatiles (NAV) and verbenone were tested for their ability to protect individual ponderosa pines, Pinus ponderosa Dougl. ex. Laws., from attack by western pine beetle (WPB), Dendroctonus brevicomis LeConte, and red turpentine beetle (RTB), Dendroctonus valens LeConte (Coleoptera: Curculionidae, Scolytinae). A combination of (

IDENTIFICATION OF THE STRUCTURE AND ORIGIN OF A THIOACIDOLYSIS MARKER COMPOUND FOR FERULIC ACID INCORPORATION INTO ANGIOSPERM LIGNINS (AND AN INDICATOR FOR CINNAMOYL-CoA REDUCTASE DEFICIENCY)

USDA-ARS?s Scientific Manuscript database

A molecular marker compound, derived from lignin by the thioacidolysis degradative method, for structures produced when ferulic acid is incorporated into lignification in angiosperms (poplar, Arabidopsis, tobacco), has been structurally identified as 1,2,2-trithioethyl ethylguaiacol [1-(4-hydroxy-3-...

Identification, expression, and taxonomic distribution of alternative oxidases in non-angiosperm plants.

PubMed

Neimanis, Karina; Staples, James F; Hüner, Norman P A; McDonald, Allison E

2013-09-10

Alternative oxidase (AOX) is a terminal ubiquinol oxidase present in the respiratory chain of all angiosperms investigated to date, but AOX distribution in other members of the Viridiplantae is less clear. We assessed the taxonomic distribution of AOX using bioinformatics. Multiple sequence alignments compared AOX proteins and examined amino acid residues involved in AOX catalytic function and post-translational regulation. Novel AOX sequences were found in both Chlorophytes and Streptophytes and we conclude that AOX is widespread in the Viridiplantae. AOX multigene families are common in non-angiosperm plants and the appearance of AOX1 and AOX2 subtypes pre-dates the divergence of the Coniferophyta and Magnoliophyta. Residues involved in AOX catalytic function are highly conserved between Chlorophytes and Streptophytes, while AOX post-translational regulation likely differs in these two lineages. We demonstrate experimentally that an AOX gene is present in the moss Physcomitrella patens and that the gene is transcribed. Our findings suggest that AOX will likely exert an influence on plant respiration and carbon metabolism in non-angiosperms such as green algae, bryophytes, liverworts, lycopods, ferns, gnetophytes, and gymnosperms and that further research in these systems is required. Copyright © 2013 Elsevier B.V. All rights reserved.

Divergence of RNA polymerase α subunits in angiosperm plastid genomes is mediated by genomic rearrangement.

PubMed

Blazier, J Chris; Ruhlman, Tracey A; Weng, Mao-Lun; Rehman, Sumaiyah K; Sabir, Jamal S M; Jansen, Robert K

2016-04-18

Genes for the plastid-encoded RNA polymerase (PEP) persist in the plastid genomes of all photosynthetic angiosperms. However, three unrelated lineages (Annonaceae, Passifloraceae and Geraniaceae) have been identified with unusually divergent open reading frames (ORFs) in the conserved region of rpoA, the gene encoding the PEP α subunit. We used sequence-based approaches to evaluate whether these genes retain function. Both gene sequences and complete plastid genome sequences were assembled and analyzed from each of the three angiosperm families. Multiple lines of evidence indicated that the rpoA sequences are likely functional despite retaining as low as 30% nucleotide sequence identity with rpoA genes from outgroups in the same angiosperm order. The ratio of non-synonymous to synonymous substitutions indicated that these genes are under purifying selection, and bioinformatic prediction of conserved domains indicated that functional domains are preserved. One of the lineages (Pelargonium, Geraniaceae) contains species with multiple rpoA-like ORFs that show evidence of ongoing inter-paralog gene conversion. The plastid genomes containing these divergent rpoA genes have experienced extensive structural rearrangement, including large expansions of the inverted repeat. We propose that illegitimate recombination, not positive selection, has driven the divergence of rpoA.

Changes in floral diversities, floral turnover rates, and climates in Campanian and Maastrichtian time, North Slope of Alaska

USGS Publications Warehouse

Frederiksen, N.O.

1989-01-01

One-hundred-and-ten angiosperm pollen taxa have been found in upper Campanian to Masstrichtian rocks of the Colville River region, North Slope of Alaska. These are the highest paleolatitude Campanian and Maastrichtian floras known from North America. Total angiosperm pollen diversity rose during the Campanian and declined toward the end of the Maastrichtian. However, anemophilous porate pollen of the Betulaceae-Myricaceae-Ulmaceae complex increased gradually in diversity during the late Campanian and Maastrichtian and into the Paleocene. Turnover of angiosperm taxa was active throughout most of late Campanian and Maastrichtian time; rapid turnover affected mainly the taxa of zoophilous herbs, representing an bundant but ecologically subordinate element of the vegetation. Last appearances of pollen taxa during the late Campanian and Maastrichtian probably represented mainly extinctions rather than emigrations; end- Cretaceous angiosperm extinctions in the North American Arctic began well before the Cretaceous-Tertiary boundary event. The last appearances in the late Maastrichtian took place in bursts; they appear to represent stepwise rather than gradual events, which may indicate the existence of pulses of climatic change particularly in late Maastrichtian time. ?? 1989.

First Nuclear DNA C-values for 18 Eudicot Families

PubMed Central

HANSON, LYNDA; BOYD, AMY; JOHNSON, MARGARET A. T.; BENNETT, MICHAEL D.

2005-01-01

• Background and Aims A key target set at the second Plant Genome Size Workshop, held at the Royal Botanic Gardens, Kew in 2003, was to produce first DNA C-value data for an additional 1 % of angiosperm species, and, within this, to achieve 75 % familial coverage overall (up from approx. 50 %) by 2009. The present study targeted eudicot families for which representation in 2003 (42·5 %) was much lower than monocot (72·8 %) and basal angiosperm (69·0 %) families. • Methods Flow cytometry or Feulgen microdensitometry were used to estimate nuclear DNA C-values, and chromosome counts were obtained where possible. • Key Results First nuclear DNA C-values are reported for 20 angiosperm families, including 18 eudicots. This substantially increases familial representation to 55·2 % for angiosperms and 48·5 % for eudicots. • Conclusions The importance of targeting specific plant families to improve familial nuclear DNA C-value representation is reconfirmed. International collaboration will be increasingly essential to locate and obtain material of unsampled plant families, if the target set by the second Plant Genome Size Workshop is to be met. PMID:16239248

Leaf hydraulic capacity in ferns, conifers and angiosperms: impacts on photosynthetic maxima.

PubMed

Brodribb, Tim J; Holbrook, N Michele; Zwieniecki, Maciej A; Palma, Beatriz

2005-03-01

* The hydraulic plumbing of vascular plant leaves varies considerably between major plant groups both in the spatial organization of veins, as well as their anatomical structure. * Five conifers, three ferns and 12 angiosperm trees were selected from tropical and temperate forests to investigate whether the profound differences in foliar morphology of these groups lead to correspondingly profound differences in leaf hydraulic efficiency. * We found that angiosperm leaves spanned a range of leaf hydraulic conductance from 3.9 to 36 mmol m2 s-1 MPa-1, whereas ferns (5.9-11.4 mmol m-2 s-1 MPa-1) and conifers (1.6-9.0 mmol m-2 s-1 MPa-1) were uniformly less conductive to liquid water. Leaf hydraulic conductance (Kleaf) correlated strongly with stomatal conductance indicating an internal leaf-level regulation of liquid and vapour conductances. Photosynthetic capacity also increased with Kleaf, however, it became saturated at values of Kleaf over 20 mmol m-2 s-1 MPa-1. * The data suggest that vessels in the leaves of the angiosperms studied provide them with the flexibility to produce highly conductive leaves with correspondingly high photosynthetic capacities relative to tracheid-bearing species.

Molecular evolution across the Asteraceae: micro- and macroevolutionary processes.

PubMed

Kane, Nolan C; Barker, Michael S; Zhan, Shing H; Rieseberg, Loren H

2011-12-01

The Asteraceae (Compositae) is a large family of over 20,000 wild, weedy, and domesticated species that comprise approximately 10% of all angiosperms, including annual and perennial herbs, shrubs and trees, and species on every continent except Antarctica. As a result, the Asteraceae provide a unique opportunity to understand the evolutionary genomics of lineage radiation and diversification at numerous phylogenetic scales. Using publicly available expressed sequence tags from 22 species representing four of the major Asteraceae lineages, we assessed neutral and nonneutral evolutionary processes across this diverse plant family. We used bioinformatic tools to identify candidate genes under selection in each species. Evolution at silent and coding sites were assessed for different Gene Ontology functional categories to compare rates of evolution over both short and long evolutionary timescales. Our results indicate that patterns of molecular change across the family are surprisingly consistent on a macroevolutionary timescale and much more so more than would be predicted from the analysis of one (or many) examples of microevolution. These analyses also point to particular classes of genes that may be crucial in shaping the radiation of this diverse plant family. Similar analyses of nuclear and chloroplast genes in six other plant families confirm that many of these patterns are common features of the plant kingdom.

Is floral specialization an evolutionary dead-end? Pollination system transitions in Ruellia (Acanthaceae).

PubMed

Tripp, Erin A; Manos, Paul S

2008-07-01

Pollination systems frequently reflect adaptations to particular groups of pollinators. Such systems are indicative of evolutionary specialization and have been important in angiosperm diversification. We studied the evolution of pollination systems in the large genus Ruellia. Phylogenetic analyses, morphological ordinations, ancestral state reconstructions, and a character mapping simulation were conducted to reveal key patterns in the direction and lability of floral characters associated with pollination. We found significant floral morphological differences among species that were generally associated with different groups of floral visitors. Floral evolution has been highly labile and also directional. Some specialized systems such as hawkmoth or bat pollination are likely evolutionary dead-ends. In contrast, specialized pollination by hummingbirds is clearly not a dead-end. We found evidence for multiple reverse transitions from presumed ancestral hummingbird pollination to more derived bee or insect pollination. These repeated origins of insect pollination from hummingbird-pollinated ancestors have not evolved without historical baggage. Flowers of insect-pollinated species derived from hummingbird-pollinated ancestors are morphologically more similar to hummingbird flowers than they are to other more distantly related insect-pollinated flowers. Finally, some pollinator switches were concomitant with changes in floral morphology that are associated with those pollinators. These observations are consistent with the hypothesis that some transitions have been adaptive in the evolution of Ruellia.

Patterns of host-plant choice in bees of the genus Chelostoma: the constraint hypothesis of host-range evolution in bees.

PubMed

Sedivy, Claudio; Praz, Christophe J; Müller, Andreas; Widmer, Alex; Dorn, Silvia

2008-10-01

To trace the evolution of host-plant choice in bees of the genus Chelostoma (Megachilidae), we assessed the host plants of 35 Palearctic, North American and Indomalayan species by microscopically analyzing the pollen loads of 634 females and reconstructed their phylogenetic history based on four genes and a morphological dataset, applying both parsimony and Bayesian methods. All species except two were found to be strict pollen specialists at the level of plant family or genus. These oligolectic species together exploit the flowers of eight different plant orders that are distributed among all major angiosperm lineages. Based on ancestral state reconstruction, we found that oligolecty is the ancestral state in Chelostoma and that the two pollen generalists evolved from oligolectic ancestors. The distinct pattern of host broadening in these two polylectic species, the highly conserved floral specializations within the different clades, the exploitation of unrelated hosts with a striking floral similarity as well as a recent report on larval performance on nonhost pollen in two Chelostoma species clearly suggest that floral host choice is physiologically or neurologically constrained in bees of the genus Chelostoma. Based on this finding, we propose a new hypothesis on the evolution of host range in bees.