Science.gov

Sample records for legume nodule development

  1. Hormonal Control of Lateral Root and Nodule Development in Legumes

    PubMed Central

    Bensmihen, Sandra

    2015-01-01

    Many plants can establish symbioses with nitrogen-fixing bacteria, some of which lead to nodulation, including legumes. Indeed, in the rhizobium/legume symbiosis, new root organs, called nodules, are formed by the plant in order to host the rhizobia in protective conditions, optimized for nitrogen fixation. In this way, these plants can benefit from the reduction of atmospheric dinitrogen into ammonia by the hosted bacteria, and in exchange the plant provides the rhizobia with a carbon source. Since this symbiosis is costly for the plant it is highly regulated. Both legume nodule and lateral root organogenesis involve divisions of the root inner tissues, and both developmental programs are tightly controlled by plant hormones. In fact, most of the major plant hormones, such as auxin, cytokinins, abscisic acid, and strigolactones, control both lateral root formation and nodule organogenesis, but often in an opposite manner. This suggests that the sensitivity of legume plants to some phytohormones could be linked to the antagonism that exists between the processes of nodulation and lateral root formation. Here, we will review the implication of some major phytohormones in lateral root formation in legumes, compare them with their roles in nodulation, and discuss specificities and divergences from non-legume eudicot plants such as Arabidopsis thaliana. PMID:27135340

  2. NODULE ROOT and COCHLEATA maintain nodule development and are legume orthologs of Arabidopsis BLADE-ON-PETIOLE genes.

    PubMed

    Couzigou, Jean-Malo; Zhukov, Vladimir; Mondy, Samuel; Abu el Heba, Ghada; Cosson, Viviane; Ellis, T H Noel; Ambrose, Mike; Wen, Jiangqi; Tadege, Million; Tikhonovich, Igor; Mysore, Kirankumar S; Putterill, Joanna; Hofer, Julie; Borisov, Alexei Y; Ratet, Pascal

    2012-11-01

    During their symbiotic interaction with rhizobia, legume plants develop symbiosis-specific organs on their roots, called nodules, that house nitrogen-fixing bacteria. The molecular mechanisms governing the identity and maintenance of these organs are unknown. Using Medicago truncatula nodule root (noot) mutants and pea (Pisum sativum) cochleata (coch) mutants, which are characterized by the abnormal development of roots from the nodule, we identified the NOOT and COCH genes as being necessary for the robust maintenance of nodule identity throughout the nodule developmental program. NOOT and COCH are Arabidopsis thaliana BLADE-ON-PETIOLE orthologs, and we have shown that their functions in leaf and flower development are conserved in M. truncatula and pea. The identification of these two genes defines a clade in the BTB/POZ-ankyrin domain proteins that shares conserved functions in eudicot organ development and suggests that NOOT and COCH were recruited to repress root identity in the legume symbiotic organ.

  3. Water-tolerant legume nodulation.

    PubMed

    Capoen, Ward; Goormachtig, Sofie; Holsters, Marcelle

    2010-03-01

    Water-tolerant nodulation is an adaptation of legumes that grow in wet or temporarily flooded habitats. This nodulation mode takes place at lateral root bases via intercellular bacterial invasion in cortical infection pockets. The tropical legume Sesbania rostrata has become a model for the study of the molecular basis of crack entry nodulation compared with root hair curl nodulation. For intercellular invasion, Nodulation Factor (NF) signalling recruits an ethylene-dependent, common Sym gene-independent pathway, leading to local cell death. The NF structure requirements are less stringent than for intracellular invasion in root hairs, which is correlated with a very specific NF-induced calcium spiking signature, presumably necessary for correct gene expression to assemble a functional entry complex in the epidermis.

  4. Mechanistic action of gibberellins in legume nodulation.

    PubMed

    Hayashi, Satomi; Gresshoff, Peter M; Ferguson, Brett J

    2014-10-01

    Legume plants are capable of entering into a symbiotic relationship with rhizobia bacteria. This results in the formation of novel organs on their roots, called nodules, in which the bacteria capture atmospheric nitrogen and provide it as ammonium to the host plant. Complex molecular and physiological changes are involved in the formation and establishment of such nodules. Several phytohormones are known to play key roles in this process. Gibberellins (gibberellic acids; GAs), a class of phytohormones known to be involved in a wide range of biological processes (i.e., cell elongation, germination) are reported to be involved in the formation and maturation of legume nodules, highlighted by recent transcriptional analyses of early soybean symbiotic steps. Here, we summarize what is currently known about GAs in legume nodulation and propose a model of GA action during nodule development. Results from a wide range of studies, including GA application, mutant phenotyping, and gene expression studies, indicate that GAs are required at different stages, with an optimum, tightly regulated level being key to achieve successful nodulation. Gibberellic acids appear to be required at two distinct stages of nodulation: (i) early stages of rhizobia infection and nodule primordium establishment; and (ii) later stages of nodule maturation. © 2014 Institute of Botany, Chinese Academy of Sciences.

  5. Nodule development on the tropical legume Sesbania virgata under flooded and non-flooded conditions.

    PubMed

    Bomfeti, C A; Ferreira, P A A; Carvalho, T S; De Rycke, R; Moreira, F M S; Goormachtig, S; Holsters, M

    2013-01-01

    The interaction between the Brazilian pioneer legume Sesbania virgata and its microsymbiont Azorhizobium doebereinerae leads to the formation of nitrogen-fixing nodules on roots that grow either in well-aerated soils or in wetlands. We studied the initiation and development of nodules under these alternative conditions. To this end, light and fluorescence microscopy were used to follow the bacterial colonisation and invasion into the host and, by means of transmission electron microscopy, we could observe the intracellular entry. Under hydroponic conditions, intercellular invasion took place at lateral root bases and mature nodules were round and determinate. However, on roots grown in vermiculite that allows aerated growth, bacteria also entered via root hair invasion and nodules were both of the determinate and indeterminate type. Such versatility in entry and developmental plasticity, as previously described in Sesbania rostrata, enables efficient nodulation in both dry and wet environments and are an important adaptive feature of this group of semi-tropical plants that grow in temporarily flooded habitats.

  6. NODULE ROOT and COCHLEATA Maintain Nodule Development and Are Legume Orthologs of Arabidopsis BLADE-ON-PETIOLE Genes[W][OA

    PubMed Central

    Couzigou, Jean-Malo; Zhukov, Vladimir; Mondy, Samuel; Abu el Heba, Ghada; Cosson, Viviane; Ellis, T.H. Noel; Ambrose, Mike; Wen, Jiangqi; Tadege, Million; Tikhonovich, Igor; Mysore, Kirankumar S.; Putterill, Joanna; Hofer, Julie; Borisov, Alexei Y.; Ratet, Pascal

    2012-01-01

    During their symbiotic interaction with rhizobia, legume plants develop symbiosis-specific organs on their roots, called nodules, that house nitrogen-fixing bacteria. The molecular mechanisms governing the identity and maintenance of these organs are unknown. Using Medicago truncatula nodule root (noot) mutants and pea (Pisum sativum) cochleata (coch) mutants, which are characterized by the abnormal development of roots from the nodule, we identified the NOOT and COCH genes as being necessary for the robust maintenance of nodule identity throughout the nodule developmental program. NOOT and COCH are Arabidopsis thaliana BLADE-ON-PETIOLE orthologs, and we have shown that their functions in leaf and flower development are conserved in M. truncatula and pea. The identification of these two genes defines a clade in the BTB/POZ-ankyrin domain proteins that shares conserved functions in eudicot organ development and suggests that NOOT and COCH were recruited to repress root identity in the legume symbiotic organ. PMID:23136374

  7. Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms

    PubMed Central

    Sulieman, Saad; Tran, Lam-Son Phan

    2014-01-01

    The special issue “Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms” aims to investigate the physiological and biochemical advances in the symbiotic process with an emphasis on nodule establishment, development and functioning. The original research articles included in this issue provide important information regarding novel aspects of nodule metabolism and various regulatory pathways, which could have important future implications. This issue also included one review article that highlights the importance of using legume trees in the production of renewable biofuels. PMID:25347276

  8. Molecular mechanisms controlling legume autoregulation of nodulation

    PubMed Central

    Reid, Dugald E.; Ferguson, Brett J.; Hayashi, Satomi; Lin, Yu-Hsiang; Gresshoff, Peter M.

    2011-01-01

    Background High input costs and environmental pressures to reduce nitrogen use in agriculture have increased the competitive advantage of legume crops. The symbiotic relationship that legumes form with nitrogen-fixing soil bacteria in root nodules is central to this advantage. Scope Understanding how legume plants maintain control of nodulation to balance the nitrogen gains with their energy needs and developmental costs will assist in increasing their productivity and relative advantage. For this reason, the regulation of nodulation has been extensively studied since the first mutants exhibiting increased nodulation were isolated almost three decades ago. Conclusions Nodulation is regulated primarily via a systemic mechanism known as the autoregulation of nodulation (AON), which is controlled by a CLAVATA1-like receptor kinase. Multiple components sharing homology with the CLAVATA signalling pathway that maintains control of the shoot apical meristem in arabidopsis have now been identified in AON. This includes the recent identification of several CLE peptides capable of activating nodule inhibition responses, a low molecular weight shoot signal and a role for CLAVATA2 in AON. Efforts are now being focused on directly identifying the interactions of these components and to identify the form that long-distance transport molecules take. PMID:21856632

  9. Molecular mechanisms controlling legume autoregulation of nodulation.

    PubMed

    Reid, Dugald E; Ferguson, Brett J; Hayashi, Satomi; Lin, Yu-Hsiang; Gresshoff, Peter M

    2011-10-01

    High input costs and environmental pressures to reduce nitrogen use in agriculture have increased the competitive advantage of legume crops. The symbiotic relationship that legumes form with nitrogen-fixing soil bacteria in root nodules is central to this advantage. Understanding how legume plants maintain control of nodulation to balance the nitrogen gains with their energy needs and developmental costs will assist in increasing their productivity and relative advantage. For this reason, the regulation of nodulation has been extensively studied since the first mutants exhibiting increased nodulation were isolated almost three decades ago. Nodulation is regulated primarily via a systemic mechanism known as the autoregulation of nodulation (AON), which is controlled by a CLAVATA1-like receptor kinase. Multiple components sharing homology with the CLAVATA signalling pathway that maintains control of the shoot apical meristem in arabidopsis have now been identified in AON. This includes the recent identification of several CLE peptides capable of activating nodule inhibition responses, a low molecular weight shoot signal and a role for CLAVATA2 in AON. Efforts are now being focused on directly identifying the interactions of these components and to identify the form that long-distance transport molecules take.

  10. Adaptive strategies for nitrogen metabolism in phosphate deficient legume nodules.

    PubMed

    Valentine, Alex J; Kleinert, Aleysia; Benedito, Vagner A

    2017-03-01

    Legumes play a significant role in natural and agricultural ecosystems. They can fix atmospheric N2 and contribute the fixed N to soils and plant N budgets. In legumes, the availability of P does not only affect nodule development, but also N acquisition and metabolism. For legumes as an important source of plant proteins, their capacity to metabolise N during P deficiency is critical for their benefits to agriculture and the natural environment. In particular for farming, rock P is a non-renewable source of which the world has about 60-80 years of sustainable extraction of this P left. The global production of legume crops would be devastated during a scarcity of P fertiliser. Legume nodules have a high requirement for mineral P, which makes them vulnerable to soil P deficiencies. In order to maintain N metabolism, the nodules have evolved several strategies to resist the immediate effects of P limitation and to respond to prolonged P deficiency. In legumes nodules, N metabolism is determined by several processes involving the acquisition, assimilation, export, and recycling of N in various forms. Although these processes are integrated, the current literature lacks a clear synthesis of how legumes respond to P stress regarding its impact on N metabolism. In this review, we synthesise the current state of knowledge on how legumes maintain N metabolism during P deficiency. Moreover, we discuss the potential importance of two additional alterations to N metabolism during P deficiency. Our goals are to place these newly proposed mechanisms in perspective with other known adaptations of N metabolism to P deficiency and to discuss their practical benefits during P deficiency in legumes. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  11. A Legume TOR Protein Kinase Regulates Rhizobium Symbiosis and Is Essential for Infection and Nodule Development.

    PubMed

    Nanjareddy, Kalpana; Blanco, Lourdes; Arthikala, Manoj-Kumar; Alvarado-Affantranger, Xóchitl; Quinto, Carmen; Sánchez, Federico; Lara, Miguel

    2016-11-01

    The target of rapamycin (TOR) protein kinase regulates metabolism, growth, and life span in yeast, animals, and plants in coordination with nutrient status and environmental conditions. The nutrient-dependent nature of TOR functionality makes this kinase a putative regulator of symbiotic associations involving nutrient acquisition. However, TOR's role in these processes remains to be understood. Here, we uncovered the role of TOR during the bean (Phaseolus vulgaris)-Rhizobium tropici (Rhizobium) symbiotic interaction. TOR was expressed in all tested bean tissues, with higher transcript levels in the root meristems and senesced nodules. We showed TOR promoter expression along the progressing infection thread and in the infected cells of mature nodules. Posttranscriptional gene silencing of TOR using RNA interference (RNAi) showed that this gene is involved in lateral root elongation and root cell organization and also alters the density, size, and number of root hairs. The suppression of TOR transcripts also affected infection thread progression and associated cortical cell divisions, resulting in a drastic reduction of nodule numbers. TOR-RNAi resulted in reduced reactive oxygen species accumulation and altered CyclinD1 and CyclinD3 expression, which are crucial factors for infection thread progression and nodule organogenesis. Enhanced expression of TOR-regulated ATG genes in TOR-RNAi roots suggested that TOR plays a role in the recognition of Rhizobium as a symbiont. Together, these data suggest that TOR plays a vital role in the establishment of root nodule symbiosis in the common bean. © 2016 American Society of Plant Biologists. All Rights Reserved.

  12. Nitrogen fixation and carbon metabolism in legume nodules.

    PubMed

    Garg, Neera; Singla, Ranju; Geetanjali

    2004-02-01

    A large amount of energy is utilized by legume nodules for the fixation of nitrogen and assimilation of fixed nitrogen (ammonia) into organic compounds. The source of energy is provided in the form of photosynthates by the host plant. Phosphoenol pyruvate carboxylase (PEPC) enzyme, which is responsible for carbon dioxide fixation in C4 and crassulacean acid metabolism plants, has also been found to play an important role in carbon metabolism in legume root nodule. PEPC-mediated CO2 fixation in nodules results in the synthesis of C4 dicarboxylic acids, viz. aspartate, malate, fumarate etc. which can be transported into bacteroids with the intervention of dicarboxylate transporter (DCT) protein. PEPC has been purified from the root nodules of few legume species. Information on the relationship between nitrogen fixation and carbon metabolism through PEPC in leguminous plants is scanty and incoherent. This review summarizes the various aspects of carbon and nitrogen metabolism in legume root nodules.

  13. Glutathione and Homoglutathione Synthesis in Legume Root Nodules1

    PubMed Central

    Matamoros, Manuel A.; Moran, Jose F.; Iturbe-Ormaetxe, Iñaki; Rubio, Maria C.; Becana, Manuel

    1999-01-01

    High-performance liquid chromatography (HPLC) with fluorescence detection was used to study thiol metabolism in legume nodules. Glutathione (GSH) was the major non-protein thiol in all indeterminate nodules examined, as well as in the determinate nodules of cowpea (Vigna unguiculata), whereas homoglutathione (hGSH) predominated in soybean (Glycine max), bean (Phaseolus vulgaris), and mungbean (Vigna radiata) nodules. All nodules had greater thiol concentrations than the leaves and roots of the same plants because of active thiol synthesis in nodule tissue. The correlation between thiol tripeptides and the activities of glutathione synthetase (GSHS) and homoglutathione synthetase (hGSHS) in the nodules of eight legumes, and the contrasting thiol contents and activities in alfalfa (Medicago sativa) leaves (98% hGSH, 100% hGSHS) and nodules (72% GSH, 80% GSHS) indicated that the distribution of GSH and hGSH is determined by specific synthetases. Thiol contents and synthesis decreased with both natural and induced nodule senescence, and were also reduced in the senescent zone of indeterminate nodules. Thiols and GSHS were especially abundant in the meristematic and infected zones of pea (Pisum sativum) nodules. Thiols and γ-glutamylcysteinyl synthetase were also more abundant in the infected zone of bean nodules, but hGSHS was predominant in the cortex. Isolation of full-length cDNA sequences coding for γ-glutamylcysteinyl synthetase from legume nodules revealed that they are highly homologous to those from other higher plants. PMID:10557236

  14. Recent insights into antioxidant defenses of legume root nodules.

    PubMed

    Becana, Manuel; Matamoros, Manuel A; Udvardi, Michael; Dalton, David A

    2010-12-01

    Legume root nodules are sites of intense biochemical activity and consequently are at high risk of damage as a result of the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). These molecules can potentially give rise to oxidative and nitrosative damage but, when their concentrations are tightly controlled by antioxidant enzymes and metabolites, they also play positive roles as critical components of signal transduction cascades during nodule development and stress. Thus, recent advances in our understanding of ascorbate and (homo)glutathione biosynthesis in plants have opened up the possibility of enhancing N(2) fixation through an increase of their concentrations in nodules. It is now evident that antioxidant proteins other than the ascorbate-glutathione enzymes, such as some isoforms of glutathione peroxidases, thioredoxins, peroxiredoxins, and glutathione S-transferases, are also critical for nodule activity. To avoid cellular damage, nodules are endowed with several mechanisms for sequestration of Fenton-active metals (nicotianamine, phytochelatins, and metallothioneins) and for controlling ROS/RNS bioactivity (hemoglobins). The use of 'omic' technologies has expanded the list of known antioxidants in plants and nodules that participate in ROS/RNS/antioxidant signaling networks, although aspects of developmental variation and subcellular localization of these networks remain to be elucidated. To this end, a critical point will be to define the transcriptional and post-transcriptional regulation of antioxidant proteins.

  15. Standardized mapping of nodulation patterns in legume roots.

    PubMed

    Remmler, Lauren; Clairmont, Lindsey; Rolland-Lagan, Anne-Gaëlle; Guinel, Frédérique Catherine

    2014-05-01

    Optimizing nodulation in legumes is a target for crop improvement, and the spatial control of nodulation is just beginning to be unravelled. However, there is currently no method for standard phenotyping of nodulation patterns. Here we present a method and software for the quantitative analysis of nodulation phenotypes. Roots of nodulated peas (Pisum sativum), wild-type and two mutants, were photographed. Data from the photographs were extracted using custom image and data analysis software. The software makes it possible to extract each nodule's position along primary and lateral roots, and to represent the nodulated root system in a standardized way independent of the way roots are arranged in the soil. A wide variety of nodulation and root variables are calculated, and average spatial nodulation patterns can be computed from multiple samples. Standardized spatial analysis of nodulation patterns opens the way for comparative analyses among genotypes of a single legume species, as here in pea. This approach could also be used to compare nodulation patterns among crops, among plants grown under different environmental conditions, or among plants exposed to different pharmacological treatments. The proposed method should therefore prove useful for studies on nodule organogenesis and nodule physiology and for optimizing nodulation in crops. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  16. Biogenic amines in rhizobia and legume root nodules.

    PubMed

    Fujihara, Shinsuke

    2009-01-01

    Root-nodule bacteria (rhizobia) are of great importance for nitrogen acquisition through symbiotic nitrogen fixation in a wide variety of leguminous plants. These bacteria differ from most other soil microorganisms by taking dual forms, i.e. a free-living form in soils and a symbiotic form inside of host legumes. Therefore, they should have a versatile strategy for survival, whether inhabiting soils or root nodules formed through rhizobia-legume interactions. Rhizobia generally contain large amounts of the biogenic amine homospermidine, an analog of spermidine which is an essential cellular component in most living systems. The external pH, salinity and a rapid change in osmolarity are thought to be significant environmental factors affecting the persistence of rhizobia. The present review describes the regulation of homospermidine biosynthesis in response to environmental stress and its possible functional role in rhizobia. Legume root nodules, an alternative habitat of rhizobia, usually contain a variety of biogenic amines besides homospermidine and the occurrence of some of these amines is closely associated with rhizobial infections. In the second half of this review, novel biogenic amines found in certain legume root nodules and the mechanism of their synthesis involving cooperation between the rhizobia and host legume cells are also described.

  17. Comprehensive Comparative Genomic and Transcriptomic Analyses of the Legume Genes Controlling the Nodulation Process

    PubMed Central

    Qiao, Zhenzhen; Pingault, Lise; Nourbakhsh-Rey, Mehrnoush; Libault, Marc

    2016-01-01

    Nitrogen is one of the most essential plant nutrients and one of the major factors limiting crop productivity. Having the goal to perform a more sustainable agriculture, there is a need to maximize biological nitrogen fixation, a feature of legumes. To enhance our understanding of the molecular mechanisms controlling the interaction between legumes and rhizobia, the symbiotic partner fixing and assimilating the atmospheric nitrogen for the plant, researchers took advantage of genetic and genomic resources developed across different legume models (e.g., Medicago truncatula, Lotus japonicus, Glycine max, and Phaseolus vulgaris) to identify key regulatory protein coding genes of the nodulation process. In this study, we are presenting the results of a comprehensive comparative genomic analysis to highlight orthologous and paralogous relationships between the legume genes controlling nodulation. Mining large transcriptomic datasets, we also identified several orthologous and paralogous genes characterized by the induction of their expression during nodulation across legume plant species. This comprehensive study prompts new insights into the evolution of the nodulation process in legume plant and will benefit the scientific community interested in the transfer of functional genomic information between species. PMID:26858743

  18. Comprehensive Comparative Genomic and Transcriptomic Analyses of the Legume Genes Controlling the Nodulation Process.

    PubMed

    Qiao, Zhenzhen; Pingault, Lise; Nourbakhsh-Rey, Mehrnoush; Libault, Marc

    2016-01-01

    Nitrogen is one of the most essential plant nutrients and one of the major factors limiting crop productivity. Having the goal to perform a more sustainable agriculture, there is a need to maximize biological nitrogen fixation, a feature of legumes. To enhance our understanding of the molecular mechanisms controlling the interaction between legumes and rhizobia, the symbiotic partner fixing and assimilating the atmospheric nitrogen for the plant, researchers took advantage of genetic and genomic resources developed across different legume models (e.g., Medicago truncatula, Lotus japonicus, Glycine max, and Phaseolus vulgaris) to identify key regulatory protein coding genes of the nodulation process. In this study, we are presenting the results of a comprehensive comparative genomic analysis to highlight orthologous and paralogous relationships between the legume genes controlling nodulation. Mining large transcriptomic datasets, we also identified several orthologous and paralogous genes characterized by the induction of their expression during nodulation across legume plant species. This comprehensive study prompts new insights into the evolution of the nodulation process in legume plant and will benefit the scientific community interested in the transfer of functional genomic information between species.

  19. Novel paralogous gene families with potential function in legume nodules and seeds.

    PubMed

    Silverstein, Kevin A T; Graham, Michelle A; VandenBosch, Kathryn A

    2006-04-01

    Within the plant kingdom, legumes are unusual in their ability to form nitrogen-fixing nodules in symbiosis with certain bacteria in the family Rhizobiaceae (rhizhobia). Genes that are required for signaling between plant and symbiont, and for the development and maintenance of the nodule, were either created de novo or adopted from other plant pathways. Only in recent years have genome-scale sequence data from legumes made it possible to identify large, novel families of genes probably evolved to function in nodulation. Members of these novel families are expressed in seeds or nodules, and are homologous to defense-related proteins. Perhaps the most striking example is a large family (of more than 340 members) of cysteine cluster proteins that have homology to plant defensins.

  20. Biogeographical Patterns of Legume-Nodulating Burkholderia spp.: from African Fynbos to Continental Scales

    PubMed Central

    Chimphango, Samson B. M.; Stirton, Charles; Rafudeen, Suhail; Honnay, Olivier; Smets, Erik; Chen, Wen-Ming; Sprent, Janet; James, Euan K.; Muasya, A. Muthama

    2016-01-01

    ABSTRACT Rhizobia of the genus Burkholderia have large-scale distribution ranges and are usually associated with South African papilionoid and South American mimosoid legumes, yet little is known about their genetic structuring at either local or global geographic scales. To understand variation at different spatial scales, from individual legumes in the fynbos (South Africa) to a global context, we analyzed chromosomal (16S rRNA, recA) and symbiosis (nifH, nodA, nodC) gene sequences. We showed that the global diversity of nodulation genes is generally grouped according to the South African papilionoid or South American mimosoid subfamilies, whereas chromosomal sequence data were unrelated to biogeography. While nodulation genes are structured on a continental scale, a geographic or host-specific distribution pattern was not detected in the fynbos region. In host range experiments, symbiotic promiscuity of Burkholderia tuberum STM678T and B. phymatum STM815T was discovered in selected fynbos species. Finally, a greenhouse experiment was undertaken to assess the ability of mimosoid (Mimosa pudica) and papilionoid (Dipogon lignosus, Indigofera filifolia, Macroptilium atropurpureum, and Podalyria calyptrata) species to nodulate in South African (fynbos) and Malawian (savanna) soils. While the Burkholderia-philous fynbos legumes (D. lignosus, I. filifolia, and P. calyptrata) nodulated only in their native soils, the invasive neotropical species M. pudica did not develop nodules in the African soils. The fynbos soil, notably rich in Burkholderia, seems to retain nodulation genes compatible with the local papilionoid legume flora but is incapable of nodulating mimosoid legumes that have their center of diversity in South America. IMPORTANCE This study is the most comprehensive phylogenetic assessment of root-nodulating Burkholderia and investigated biogeographic and host-related patterns of the legume-rhizobial symbiosis in the South African fynbos biome, as well as at

  1. Biosynthesis of Ascorbic Acid in Legume Root Nodules1

    PubMed Central

    Matamoros, Manuel A.; Loscos, Jorge; Coronado, Maria J.; Ramos, Javier; Sato, Shusei; Testillano, Pilar S.; Tabata, Satoshi; Becana, Manuel

    2006-01-01

    Ascorbic acid (vitamin C) is a major antioxidant and redox buffer, but is also involved in other critical processes of plants. Recently, the hypothesis has been proposed that legume nodules are unable to synthesize ascorbate and have to import it from the shoot or root, thus providing a means by which the plant regulates nodule senescence. The last step of ascorbate biosynthesis in plants is catalyzed by l-galactono-1,4-lactone dehydrogenase (GalLDH). The mRNAs encoding GalLDH and three other enzymes involved in ascorbate biosynthesis are clearly detectable in nodules. Furthermore, an active membrane-bound GalLDH enzyme is present in nodule mitochondria. Biochemical assays on dissected nodules reveal that GalLDH activity and ascorbate are correlated in nodule tissues and predominantly localized in the infected zone, with lower levels of both parameters (relative to the infected tissues) in the apex (87%) and senescent region (43%) of indeterminate nodules and in the peripheral tissues (65%) of determinate nodules. In situ RNA hybridization showed that the GalLDH mRNA is particularly abundant in the infected zone of indeterminate and determinate nodules. Thus, our results refute the hypothesis that ascorbate is not synthesized in nodules and lend support to a previous conclusion that ascorbate in the infected zone is primarily involved in the protection of host cells against peroxide damage. Likewise, the high ascorbate and GalLDH activity levels found in the apex of indeterminate nodules strongly suggest a participation of ascorbate in additional functions during symbiosis, possibly related to cell growth and division and to molecular signaling. PMID:16766673

  2. A Legume Genetic Framework Controls Infection of Nodules by Symbiotic and Endophytic Bacteria

    PubMed Central

    Zgadzaj, Rafal; James, Euan K.; Kelly, Simon; Kawaharada, Yasuyuki; de Jonge, Nadieh; Jensen, Dorthe B.; Madsen, Lene H.; Radutoiu, Simona

    2015-01-01

    Legumes have an intrinsic capacity to accommodate both symbiotic and endophytic bacteria within root nodules. For the symbionts, a complex genetic mechanism that allows mutual recognition and plant infection has emerged from genetic studies under axenic conditions. In contrast, little is known about the mechanisms controlling the endophytic infection. Here we investigate the contribution of both the host and the symbiotic microbe to endophyte infection and development of mixed colonised nodules in Lotus japonicus. We found that infection threads initiated by Mesorhizobium loti, the natural symbiont of Lotus, can selectively guide endophytic bacteria towards nodule primordia, where competent strains multiply and colonise the nodule together with the nitrogen-fixing symbiotic partner. Further co-inoculation studies with the competent coloniser, Rhizobium mesosinicum strain KAW12, show that endophytic nodule infection depends on functional and efficient M. loti-driven Nod factor signalling. KAW12 exopolysaccharide (EPS) enabled endophyte nodule infection whilst compatible M. loti EPS restricted it. Analysis of plant mutants that control different stages of the symbiotic infection showed that both symbiont and endophyte accommodation within nodules is under host genetic control. This demonstrates that when legume plants are exposed to complex communities they selectively regulate access and accommodation of bacteria occupying this specialized environmental niche, the root nodule. PMID:26042417

  3. A legume genetic framework controls infection of nodules by symbiotic and endophytic bacteria.

    PubMed

    Zgadzaj, Rafal; James, Euan K; Kelly, Simon; Kawaharada, Yasuyuki; de Jonge, Nadieh; Jensen, Dorthe B; Madsen, Lene H; Radutoiu, Simona

    2015-06-01

    Legumes have an intrinsic capacity to accommodate both symbiotic and endophytic bacteria within root nodules. For the symbionts, a complex genetic mechanism that allows mutual recognition and plant infection has emerged from genetic studies under axenic conditions. In contrast, little is known about the mechanisms controlling the endophytic infection. Here we investigate the contribution of both the host and the symbiotic microbe to endophyte infection and development of mixed colonised nodules in Lotus japonicus. We found that infection threads initiated by Mesorhizobium loti, the natural symbiont of Lotus, can selectively guide endophytic bacteria towards nodule primordia, where competent strains multiply and colonise the nodule together with the nitrogen-fixing symbiotic partner. Further co-inoculation studies with the competent coloniser, Rhizobium mesosinicum strain KAW12, show that endophytic nodule infection depends on functional and efficient M. loti-driven Nod factor signalling. KAW12 exopolysaccharide (EPS) enabled endophyte nodule infection whilst compatible M. loti EPS restricted it. Analysis of plant mutants that control different stages of the symbiotic infection showed that both symbiont and endophyte accommodation within nodules is under host genetic control. This demonstrates that when legume plants are exposed to complex communities they selectively regulate access and accommodation of bacteria occupying this specialized environmental niche, the root nodule.

  4. A Legume TOR Protein Kinase Regulates Rhizobium Symbiosis and Is Essential for Infection and Nodule Development1[OPEN

    PubMed Central

    Blanco, Lourdes; Quinto, Carmen

    2016-01-01

    The target of rapamycin (TOR) protein kinase regulates metabolism, growth, and life span in yeast, animals, and plants in coordination with nutrient status and environmental conditions. The nutrient-dependent nature of TOR functionality makes this kinase a putative regulator of symbiotic associations involving nutrient acquisition. However, TOR’s role in these processes remains to be understood. Here, we uncovered the role of TOR during the bean (Phaseolus vulgaris)-Rhizobium tropici (Rhizobium) symbiotic interaction. TOR was expressed in all tested bean tissues, with higher transcript levels in the root meristems and senesced nodules. We showed TOR promoter expression along the progressing infection thread and in the infected cells of mature nodules. Posttranscriptional gene silencing of TOR using RNA interference (RNAi) showed that this gene is involved in lateral root elongation and root cell organization and also alters the density, size, and number of root hairs. The suppression of TOR transcripts also affected infection thread progression and associated cortical cell divisions, resulting in a drastic reduction of nodule numbers. TOR-RNAi resulted in reduced reactive oxygen species accumulation and altered CyclinD1 and CyclinD3 expression, which are crucial factors for infection thread progression and nodule organogenesis. Enhanced expression of TOR-regulated ATG genes in TOR-RNAi roots suggested that TOR plays a role in the recognition of Rhizobium as a symbiont. Together, these data suggest that TOR plays a vital role in the establishment of root nodule symbiosis in the common bean. PMID:27698253

  5. Legume NADPH Oxidases Have Crucial Roles at Different Stages of Nodulation.

    PubMed

    Montiel, Jesús; Arthikala, Manoj-Kumar; Cárdenas, Luis; Quinto, Carmen

    2016-05-18

    Plant NADPH oxidases, formerly known as respiratory burst oxidase homologues (RBOHs), are plasma membrane enzymes dedicated to reactive oxygen species (ROS) production. These oxidases are implicated in a wide variety of processes, ranging from tissue and organ growth and development to signaling pathways in response to abiotic and biotic stimuli. Research on the roles of RBOHs in the plant's response to biotic stresses has mainly focused on plant-pathogen interactions; nonetheless, recent findings have shown that these oxidases are also involved in the legume-rhizobia symbiosis. The legume-rhizobia symbiosis leads to the formation of the root nodule, where rhizobia reduce atmospheric nitrogen to ammonia. A complex signaling and developmental pathway in the legume root hair and root facilitate rhizobial entrance and nodule organogenesis, respectively. Interestingly, several reports demonstrate that RBOH-mediated ROS production displays versatile roles at different stages of nodulation. The evidence collected to date indicates that ROS act as signaling molecules that regulate rhizobial invasion and also function in nodule senescence. This review summarizes discoveries that support the key and versatile roles of various RBOH members in the legume-rhizobia symbiosis.

  6. Legume NADPH Oxidases Have Crucial Roles at Different Stages of Nodulation

    PubMed Central

    Montiel, Jesús; Arthikala, Manoj-Kumar; Cárdenas, Luis; Quinto, Carmen

    2016-01-01

    Plant NADPH oxidases, formerly known as respiratory burst oxidase homologues (RBOHs), are plasma membrane enzymes dedicated to reactive oxygen species (ROS) production. These oxidases are implicated in a wide variety of processes, ranging from tissue and organ growth and development to signaling pathways in response to abiotic and biotic stimuli. Research on the roles of RBOHs in the plant’s response to biotic stresses has mainly focused on plant-pathogen interactions; nonetheless, recent findings have shown that these oxidases are also involved in the legume-rhizobia symbiosis. The legume-rhizobia symbiosis leads to the formation of the root nodule, where rhizobia reduce atmospheric nitrogen to ammonia. A complex signaling and developmental pathway in the legume root hair and root facilitate rhizobial entrance and nodule organogenesis, respectively. Interestingly, several reports demonstrate that RBOH-mediated ROS production displays versatile roles at different stages of nodulation. The evidence collected to date indicates that ROS act as signaling molecules that regulate rhizobial invasion and also function in nodule senescence. This review summarizes discoveries that support the key and versatile roles of various RBOH members in the legume-rhizobia symbiosis. PMID:27213330

  7. Phenolphthalein false-positive reactions from legume root nodules.

    PubMed

    Petersen, Daniel; Kovacs, Frank

    2014-03-01

    Presumptive tests for blood play a critical role in the examination of physical evidence and in the determination of subsequent analysis. The catalytic power of hemoglobin allows colorimetric reactions employing phenolphthalein (Kastle-Meyer test) to indicate "whether" blood is present. Consequently, DNA profiles extracted from phenolphthalein-positive stains are presumed to be from blood on the evidentiary item and can lead to the identification of "whose" blood is present. Crushed nodules from a variety of legumes yielded phenolphthalein false-positive reactions that were indistinguishable from true bloodstains both in color quality and in developmental time frame. Clothing and other materials stained by nodules also yielded phenolphthalein false-positive reactivity for several years after nodule exposure. Nodules from leguminous plants contain a protein (leghemoglobin) which is structurally and functionally similar to hemoglobin. Testing of purified leghemoglobin confirmed this protein as a source of phenolphthalein reactivity. A scenario is presented showing how the presence of leghemoglobin from nodule staining can mislead investigators. © 2013 American Academy of Forensic Sciences.

  8. Legume-Rhizobium Interactions: Cowpea Root Exudate Elicits Faster Nodulation Response by Rhizobium Species

    PubMed Central

    Bhagwat, Arvind A.; Thomas, Joseph

    1982-01-01

    Preinfection events in legume-Rhizobium symbiosis were analyzed by studying the different nodulation behaviors of two rhizobial strains in cowpeas (Vigna sinensis). Log-phase cultures of Rhizobium sp. strain 1001, an isolate from the plant nodule, initiated host responses leading to infection within 2 h after inoculation, whereas log-phase cultures of Rhizobium sp. strain 32H1 took at least 7 h to trigger a discernible response. The delay observed with strain 32H1 could be eliminated by incubating the rhizobial suspension, before inoculation, for 4.5 h either in the cowpea rhizosphere/rhizoplane condition or in the root exudate of cowpea plants, grown without NH4+ in the rooting medium. The delay could not be eliminated by incubating the rhizobial suspension in the rooting medium of plants grown in the presence of 5 mM NH4+, indicating that there is a regulatory role of combined nitrogen in triggering preinfection events by the legume. The substance(s) in the root exudate which elicited the faster nodulation response by Rhizobium sp. strain 32H1 could be separated into a high-molecular-weight fraction by Sephadex G-100 gel filtration. The data support the notion that legume roots release substances that favor the development of rhizobial features essential for infection and nodulation. PMID:16345989

  9. Function of glutathione peroxidases in legume root nodules

    PubMed Central

    Matamoros, Manuel A.; Saiz, Ana; Peñuelas, Maria; Bustos-Sanmamed, Pilar; Mulet, Jose M.; Barja, Maria V.; Rouhier, Nicolas; Moore, Marten; James, Euan K.; Dietz, Karl-Josef; Becana, Manuel

    2015-01-01

    Glutathione peroxidases (Gpxs) are antioxidant enzymes not studied so far in legume nodules, despite the fact that reactive oxygen species are produced at different steps of the symbiosis. The function of two Gpxs that are highly expressed in nodules of the model legume Lotus japonicus was examined. Gene expression analysis, enzymatic and nitrosylation assays, yeast cell complementation, in situ mRNA hybridization, immunoelectron microscopy, and LjGpx-green fluorescent protein (GFP) fusions were used to characterize the enzymes and to localize each transcript and isoform in nodules. The LjGpx1 and LjGpx3 genes encode thioredoxin-dependent phospholipid hydroperoxidases and are differentially regulated in response to nitric oxide (NO) and hormones. LjGpx1 and LjGpx3 are nitrosylated in vitro or in plants treated with S-nitrosoglutathione (GSNO). Consistent with the modification of the peroxidatic cysteine of LjGpx3, in vitro assays demonstrated that this modification results in enzyme inhibition. The enzymes are highly expressed in the infected zone, but the LjGpx3 mRNA is also detected in the cortex and vascular bundles. LjGpx1 is localized to the plastids and nuclei, and LjGpx3 to the cytosol and endoplasmic reticulum. Based on yeast complementation experiments, both enzymes protect against oxidative stress, salt stress, and membrane damage. It is concluded that both LjGpxs perform major antioxidative functions in nodules, preventing lipid peroxidation and other oxidative processes at different subcellular sites of vascular and infected cells. The enzymes are probably involved in hormone and NO signalling, and may be regulated through nitrosylation of the peroxidatic cysteine essential for catalytic function. PMID:25740929

  10. Function of glutathione peroxidases in legume root nodules.

    PubMed

    Matamoros, Manuel A; Saiz, Ana; Peñuelas, Maria; Bustos-Sanmamed, Pilar; Mulet, Jose M; Barja, Maria V; Rouhier, Nicolas; Moore, Marten; James, Euan K; Dietz, Karl-Josef; Becana, Manuel

    2015-05-01

    Glutathione peroxidases (Gpxs) are antioxidant enzymes not studied so far in legume nodules, despite the fact that reactive oxygen species are produced at different steps of the symbiosis. The function of two Gpxs that are highly expressed in nodules of the model legume Lotus japonicus was examined. Gene expression analysis, enzymatic and nitrosylation assays, yeast cell complementation, in situ mRNA hybridization, immunoelectron microscopy, and LjGpx-green fluorescent protein (GFP) fusions were used to characterize the enzymes and to localize each transcript and isoform in nodules. The LjGpx1 and LjGpx3 genes encode thioredoxin-dependent phospholipid hydroperoxidases and are differentially regulated in response to nitric oxide (NO) and hormones. LjGpx1 and LjGpx3 are nitrosylated in vitro or in plants treated with S-nitrosoglutathione (GSNO). Consistent with the modification of the peroxidatic cysteine of LjGpx3, in vitro assays demonstrated that this modification results in enzyme inhibition. The enzymes are highly expressed in the infected zone, but the LjGpx3 mRNA is also detected in the cortex and vascular bundles. LjGpx1 is localized to the plastids and nuclei, and LjGpx3 to the cytosol and endoplasmic reticulum. Based on yeast complementation experiments, both enzymes protect against oxidative stress, salt stress, and membrane damage. It is concluded that both LjGpxs perform major antioxidative functions in nodules, preventing lipid peroxidation and other oxidative processes at different subcellular sites of vascular and infected cells. The enzymes are probably involved in hormone and NO signalling, and may be regulated through nitrosylation of the peroxidatic cysteine essential for catalytic function.

  11. Assay of Substances Stimulatory to Legume Nodule Formation 1

    PubMed Central

    Schaffer, A. G.; Alexander, M.

    1967-01-01

    Two methods were developed for the assay of substances stimulatory to the nodulation of bean (Phaseolus vulgaris) roots growing from segments of hypocotyl tissue. Coconut water was the chief source of active material, but extracts of cotyledons, hypocotyls and leaves of beans and of horse chestnut fruits were also stimulatory. High concentrations of nitrate improved nodulation both in the presence and absence of coconut water. The ash of coconut water was inactive. Whole alfalfa seedlings formed nodules in the dark when grown in the split medium, but nodulation was not improved by the addition of coconut water. PMID:16656537

  12. Carbon metabolism in legume nodules. Progress report, July 1982-July 1983

    SciTech Connect

    LaRue, T.A.

    1983-01-01

    The goal is to understand how the legume nodule metabolizes carbohydrate to provide energy and reductant for symbiotic fixation. The working hypothesis has been that the plant cytosol is microacrobic and that some carbon metabolism may be via anaerobic pathways similar to those in roots of flood tolerant plants. A method of analyzing redox changes in intact mitochondria, bacteroids or bacteria was adapted; a method of manipulating nitrogenase activity by oxygen inhibition was developed; the production of alcohol by soybean nodules was studied; and enzymes metabolizing alcohol/aldehyde were found in other nitrogen fixing systems. (ACR)

  13. The value of biodiversity in legume symbiotic nitrogen fixation and nodulation for biofuel and food production.

    PubMed

    Gresshoff, Peter M; Hayashi, Satomi; Biswas, Bandana; Mirzaei, Saeid; Indrasumunar, Arief; Reid, Dugald; Samuel, Sharon; Tollenaere, Alina; van Hameren, Bethany; Hastwell, April; Scott, Paul; Ferguson, Brett J

    2015-01-01

    Much of modern agriculture is based on immense populations of genetically identical or near-identical varieties, called cultivars. However, advancement of knowledge, and thus experimental utility, is found through biodiversity, whether naturally-found or induced by the experimenter. Globally we are confronted by ever-growing food and energy challenges. Here we demonstrate how such biodiversity from the food legume crop soybean (Glycine max L. Merr) and the bioenergy legume tree Pongamia (Millettia) pinnata is a great value. Legume plants are diverse and are represented by over 18,000 species on this planet. Some, such as soybean, pea and medics are used as food and animal feed crops. Others serve as ornamental (e.g., wisteria), timber (e.g., acacia/wattle) or biofuel (e.g., Pongamia pinnata) resources. Most legumes develop root organs (nodules) after microsymbiont induction that serve as their habitat for biological nitrogen fixation. Through this, nitrogen fertiliser demand is reduced by the efficient symbiosis between soil Rhizobium-type bacteria and the appropriate legume partner. Mechanistic research into the genetics, biochemistry and physiology of legumes is thus strategically essential for future global agriculture. Here we demonstrate how molecular plant science analysis of the genetics of an established food crop (soybean) and an emerging biofuel P. pinnata feedstock contributes to their utility by sustainable production aided by symbiotic nitrogen fixation.

  14. Legume nodule senescence: roles for redox and hormone signalling in the orchestration of the natural aging process.

    PubMed

    Puppo, Alain; Groten, Karin; Bastian, Fabiola; Carzaniga, Raffaella; Soussi, Mariam; Lucas, M Mercedes; de Felipe, Maria Rosario; Harrison, Judith; Vanacker, Hélène; Foyer, Christine H

    2005-03-01

    Research on legume nodule development has contributed greatly to our current understanding of plant-microbe interactions. However, the factors that orchestrate root nodule senescence have received relatively little attention. Accumulating evidence suggests that redox signals contribute to the establishment of symbiosis and senescence. Although degenerative in nature, nodule senescence is an active process programmed in development in which reactive oxygen species (ROS), antioxidants, hormones and proteinases have key roles. Nodules have high levels of the redox buffers, ascorbate and glutathione, which are important in the nodulation process and in senescence. These metabolites decline with N-fixation as the nodule ages but the resultant decrease in redox buffering capacity does not necessarily lead to enhanced ROS or oxidative stress. We propose models by which ROS and antioxidants interact with hormones such as abscisic acid in the orchestration of nodule senescence.

  15. Rhizobium symbiotic genes required for nodulation of legume and nonlegume hosts

    PubMed Central

    Marvel, Deborah J.; Torrey, John G.; Ausubel, Frederick M.

    1987-01-01

    Parasponia, a woody member of the elm family, is the only nonlegume genus whose members are known to form an effective nitrogen-fixing symbiosis with Bradyrhizobium or Rhizobium species. The Bradyrhizobium strain Rp501, isolated from Parasponia nodules, also nodulates the legumes siratro (Macroptilium atropurpureum) and cowpea (Vigna unguiculata). To test whether some of the same genes are involved in the early stages of legume and nonlegume nodulation, we generated transposon Tn5 insertions in the region of three evolutionarily conserved genes (nodA, nodB, and nodC) required for legume nodulation in several Rhizobium and Bradyrhizobium species. Assays of these mutant Rp501 strains on legume hosts and Parasponia seedlings established that nodABC are required for nodulation of legume and nonlegume hosts, indicating that nonlegumes and legumes can respond to the same bacterial signal(s). In addition, a strain carrying a Tn5 insertion adjacent to the nodABC genes vigorously nodulated Rp501 legume hosts but was incapable of nodulating Parasponia, possibly identifying a nonlegume-specific nodulation function. Images PMID:16593814

  16. Two MicroRNAs Linked to Nodule Infection and Nitrogen-Fixing Ability in the Legume Lotus japonicus1[W

    PubMed Central

    De Luis, Ana; Markmann, Katharina; Cognat, Valérie; Holt, Dennis B.; Charpentier, Myriam; Parniske, Martin; Stougaard, Jens; Voinnet, Olivier

    2012-01-01

    Legumes overcome nitrogen shortage by developing root nodules in which symbiotic bacteria fix atmospheric nitrogen in exchange for host-derived carbohydrates and mineral nutrients. Nodule development involves the distinct processes of nodule organogenesis, bacterial infection, and the onset of nitrogen fixation. These entail profound, dynamic gene expression changes, notably contributed to by microRNAs (miRNAs). Here, we used deep-sequencing, candidate-based expression studies and a selection of Lotus japonicus mutants uncoupling different symbiosis stages to identify miRNAs involved in symbiotic nitrogen fixation. Induction of a noncanonical miR171 isoform, which targets the key nodulation transcription factor Nodulation Signaling Pathway2, correlates with bacterial infection in nodules. A second candidate, miR397, is systemically induced in the presence of active, nitrogen-fixing nodules but not in that of noninfected or inactive nodule organs. It is involved in nitrogen fixation-related copper homeostasis and targets a member of the laccase copper protein family. These findings thus identify two miRNAs specifically responding to symbiotic infection and nodule function in legumes. PMID:23071252

  17. Identification of rhizobial strains nodulating Egyptian grain legumes.

    PubMed

    Zahran, Hamdi H; Chahboune, Rajaa; Moreno, Silvia; Bedmar, Eulogio J; Abdel-Fattah, Medhat; Yasser, Manal M; Mahmoud, Ahmed M

    2013-09-01

    Fifty four bacterial strains were isolated from root nodules of the grain legumes Cicer arietinum, Lens esculentus, Phaseolus vulgaris, Pisum sativum, and Vicia faba grown in cultivated lands of Beni-Suef Governorate (Egypt). Repetitive extragenic palindromic (REP)-polymerase chain reaction (PCR) clustered the strains into 15 REP-PCR groups. The nearly complete sequence of the 16S rRNA gene from a representative strain of each REP-PCR pattern showed that the strains were closely related to members of the family Rhizobiaceae of the Alphaproteobacteria. Pairwise alignments between globally aligned sequences indicated that the strains from V. faba had 99.6% identity with Rhizobium leguminosarum, and those from P. vulgaris 99.76% and 100% with sequences from R. leguminosarum and R. mesosinicum, respectively. Strains from P. sativum had 99.76%, 99.84%, and 99.92% sequence identity with R. leguminosarum, R. etli, and R. pisi, respectively, and those from L. esculentus had 99.61% identity with sequences from R. leguminosarum. Sequences of the strains from C. arietinum had 100% identity with those of Mesorhizobium amorphae and M. robiniae, respectively. Nitrogenase activity, determined as acetylene-dependent ethylene production, was detected in nodules formed after inoculation of the corresponding host plant with the representative rhizobial species.

  18. The temperature-sensitive brush mutant of the legume Lotus japonicus reveals a link between root development and nodule infection by rhizobia.

    PubMed

    Maekawa-Yoshikawa, Makoto; Müller, Judith; Takeda, Naoya; Maekawa, Takaki; Sato, Shusei; Tabata, Satoshi; Perry, Jillian; Wang, Trevor L; Groth, Martin; Brachmann, Andreas; Parniske, Martin

    2009-04-01

    The brush mutant of Lotus japonicus exhibits a temperature-dependent impairment in nodule, root, and shoot development. At 26 degrees C, brush formed fewer nodules, most of which were not colonized by rhizobia bacteria. Primary root growth was retarded and the anatomy of the brush root apical meristem revealed distorted cellular organization and reduced cell expansion. Reciprocal grafting of brush with wild-type plants indicated that this genotype only affected the root and that the shoot phenotype was a secondary effect. The root and nodulation phenotype cosegregated as a single Mendelian trait and the BRUSH gene could be mapped to the short arm of chromosome 2. At 18 degrees C, the brush root anatomy was rescued and similar to the wild type, and primary root length, number of infection threads, and nodule formation were partially rescued. Superficially, the brush root phenotype resembled the ethylene-related thick short root syndrome. However, treatment with ethylene inhibitor did not recover the observed phenotypes, although brush primary roots were slightly longer. The defects of brush in root architecture and infection thread development, together with intact nodule architecture and complete absence of symptoms from shoots, suggest that BRUSH affects cellular differentiation in a tissue-dependent way.

  19. The Temperature-Sensitive brush Mutant of the Legume Lotus japonicus Reveals a Link between Root Development and Nodule Infection by Rhizobia[C][W][OA

    PubMed Central

    Maekawa-Yoshikawa, Makoto; Müller, Judith; Takeda, Naoya; Maekawa, Takaki; Sato, Shusei; Tabata, Satoshi; Perry, Jillian; Wang, Trevor L.; Groth, Martin; Brachmann, Andreas; Parniske, Martin

    2009-01-01

    The brush mutant of Lotus japonicus exhibits a temperature-dependent impairment in nodule, root, and shoot development. At 26°C, brush formed fewer nodules, most of which were not colonized by rhizobia bacteria. Primary root growth was retarded and the anatomy of the brush root apical meristem revealed distorted cellular organization and reduced cell expansion. Reciprocal grafting of brush with wild-type plants indicated that this genotype only affected the root and that the shoot phenotype was a secondary effect. The root and nodulation phenotype cosegregated as a single Mendelian trait and the BRUSH gene could be mapped to the short arm of chromosome 2. At 18°C, the brush root anatomy was rescued and similar to the wild type, and primary root length, number of infection threads, and nodule formation were partially rescued. Superficially, the brush root phenotype resembled the ethylene-related thick short root syndrome. However, treatment with ethylene inhibitor did not recover the observed phenotypes, although brush primary roots were slightly longer. The defects of brush in root architecture and infection thread development, together with intact nodule architecture and complete absence of symptoms from shoots, suggest that BRUSH affects cellular differentiation in a tissue-dependent way. PMID:19176723

  20. Symbiotic relationships of legumes and nodule bacteria on Barro Colorado Island, Panama: a review.

    PubMed

    Parker, Matthew A

    2008-05-01

    Abstract New data on 129 bacterial isolates were analyzed together with prior samples to characterize community-level patterns of legume-rhizobial symbiosis on Barro Colorado Island (BCI), Panama. Nodules have been sampled from 24 BCI legume species in 18 genera, representing about one quarter of the legume species and one half of the genera on the island. Most BCI legumes associated exclusively with nodule symbionts in the genus Bradyrhizobium, which comprised 86.3% of all isolates (315 of 365). Most of the remaining isolates (44 of 365) belonged to the beta-proteobacterial genus Burkholderia; these were restricted to two genera in the legume subfamily Mimosoideae. Multilocus sequence analysis indicated that BCI Bradyrhizobium strains were differentiated into at least eight lineages with deoxyribonucleic acid divergence of the same magnitude as found among currently recognized species in this bacterial genus. Two of these lineages were widely distributed across BCI legumes. One lineage was utilized by 15 host species of diverse life form (herbs, lianas, and trees) in 12 genera spanning two legume subfamilies. A second common lineage closely related to the taxon B. elkanii was associated with at least five legume genera in four separate tribes. Thus, BCI legume species from diverse clades within the family frequently share interaction with a few common lineages of nodule symbionts. However, certain host species were associated with unique symbiont lineages that have not been found on other coexisting BCI legumes. More comprehensive sampling of host taxa will be needed to characterize the overall diversity of nodule bacteria and the patterns of symbiont sharing among legumes in this community.

  1. Competition between rhizobia under different environmental conditions affects the nodulation of a legume.

    PubMed

    Ji, Zhao Jun; Yan, Hui; Cui, Qing Guo; Wang, En Tao; Chen, Wen Feng; Chen, Wen Xin

    2017-03-01

    Mutualistic symbiosis and nitrogen fixation of legume rhizobia play a key role in ecological environments. Although many different rhizobial species can form nodules with a specific legume, there is often a dominant microsymbiont, which has the highest nodule occupancy rates, and they are often known as the "most favorable rhizobia". Shifts in the most favorable rhizobia for a legume in different geographical regions or soil types are not well understood. Therefore, in order to explore the shift model, an experiment was designed using successive inoculations of rhizobia on one legume. The plants were grown in either sterile vermiculite or a sandy soil. Results showed that, depending on the environment, a legume could select its preferential rhizobial partner in order to establish symbiosis. For perennial legumes, nodulation is a continuous and sequential process. In this study, when the most favorable rhizobial strain was available to infect the plant first, it was dominant in the nodules, regardless of the existence of other rhizobial strains in the rhizosphere. Other rhizobial strains had an opportunity to establish symbiosis with the plant when the most favorable rhizobial strain was not present in the rhizosphere. Nodule occupancy rates of the most favorable rhizobial strain depended on the competitiveness of other rhizobial strains in the rhizosphere and the environmental adaptability of the favorable rhizobial strain (in this case, to mild vermiculite or hostile sandy soil). To produce high nodulation and efficient nitrogen fixation, the most favorable rhizobial strain should be selected and inoculated into the rhizosphere of legume plants under optimum environmental conditions. Copyright © 2016 Elsevier GmbH. All rights reserved.

  2. South african papilionoid legumes are nodulated by diverse burkholderia with unique nodulation and nitrogen-fixation Loci.

    PubMed

    Beukes, Chrizelle W; Venter, Stephanus N; Law, Ian J; Phalane, Francina L; Steenkamp, Emma T

    2013-01-01

    The root-nodule bacteria of legumes endemic to the Cape Floristic Region are largely understudied, even though recent reports suggest the occurrence of nodulating Burkholderia species unique to the region. In this study, we considered the diversity and evolution of nodulating Burkholderia associated with the endemic papilionoid tribes Hypocalypteae and Podalyrieae. We identified distinct groups from verified rhizobial isolates by phylogenetic analyses of the 16S rRNA and recA housekeeping gene regions. In order to gain insight into the evolution of the nodulation and diazotrophy of these rhizobia we analysed the genes encoding NifH and NodA. The majority of these 69 isolates appeared to be unique, potentially representing novel species. Evidence of horizontal gene transfer determining the symbiotic ability of these Cape Floristic Region isolates indicate evolutionary origins distinct from those of nodulating Burkholderia from elsewhere in the world. Overall, our findings suggest that Burkholderia species associated with fynbos legumes are highly diverse and their symbiotic abilities have unique ancestries. It is therefore possible that the evolution of these bacteria is closely linked to the diversification and establishment of legumes characteristic of the Cape Floristic Region.

  3. South African Papilionoid Legumes Are Nodulated by Diverse Burkholderia with Unique Nodulation and Nitrogen-Fixation Loci

    PubMed Central

    Beukes, Chrizelle W.; Venter, Stephanus N.; Law, Ian J.; Phalane, Francina L.; Steenkamp, Emma T.

    2013-01-01

    The root-nodule bacteria of legumes endemic to the Cape Floristic Region are largely understudied, even though recent reports suggest the occurrence of nodulating Burkholderia species unique to the region. In this study, we considered the diversity and evolution of nodulating Burkholderia associated with the endemic papilionoid tribes Hypocalypteae and Podalyrieae. We identified distinct groups from verified rhizobial isolates by phylogenetic analyses of the 16S rRNA and recA housekeeping gene regions. In order to gain insight into the evolution of the nodulation and diazotrophy of these rhizobia we analysed the genes encoding NifH and NodA. The majority of these 69 isolates appeared to be unique, potentially representing novel species. Evidence of horizontal gene transfer determining the symbiotic ability of these Cape Floristic Region isolates indicate evolutionary origins distinct from those of nodulating Burkholderia from elsewhere in the world. Overall, our findings suggest that Burkholderia species associated with fynbos legumes are highly diverse and their symbiotic abilities have unique ancestries. It is therefore possible that the evolution of these bacteria is closely linked to the diversification and establishment of legumes characteristic of the Cape Floristic Region. PMID:23874611

  4. Malonate Catabolism Does Not Drive N2 Fixation in Legume Nodules

    PubMed Central

    Karunakaran, Ramakrishnan; East, Alison K.

    2013-01-01

    Malonyl-coenzyme A (CoA) decarboxylase, malonyl-CoA synthetase, and malonate transporter mutants of Rhizobium leguminosarum bv. viciae and trifolii fixed N2 at wild-type rates on pea and clover, respectively. Thus, malonate does not drive N2 fixation in legume nodules. PMID:23666330

  5. Malonate catabolism does not drive N2 fixation in legume nodules.

    PubMed

    Karunakaran, Ramakrishnan; East, Alison K; Poole, Philip S

    2013-07-01

    Malonyl-coenzyme A (CoA) decarboxylase, malonyl-CoA synthetase, and malonate transporter mutants of Rhizobium leguminosarum bv. viciae and trifolii fixed N2 at wild-type rates on pea and clover, respectively. Thus, malonate does not drive N2 fixation in legume nodules.

  6. Rhizobial Diversity and Nodulation Characteristics of the Extremely Promiscuous Legume Sophora flavescens.

    PubMed

    Jiao, Yin Shan; Liu, Yuan Hui; Yan, Hui; Wang, En Tao; Tian, Chang Fu; Chen, Wen Xin; Guo, Bao Lin; Chen, Wen Feng

    2015-12-01

    In present study, we report our extensive survey on the diversity and biogeography of rhizobia associated with Sophora flavescens, a sophocarpidine (matrine)-containing medicinal legume. We additionally investigated the cross nodulation, infection pattern, light and electron microscopies of root nodule sections of S. flavescens infected by various rhizobia. Seventeen genospecies of rhizobia belonging to five genera with seven types of symbiotic nodC genes were found to nodulate S. flavescens in natural soils. In the cross-nodulation tests, most representative rhizobia in class α-Proteobacteria, whose host plants belong to different cross-nodulation groups, form effective indeterminate nodules, while representative rhizobia in class β-Proteobacteria form ineffective nodules on S. flavescens. Highly host-specific biovars of Rhizobium leguminosarum (bv. trifolii and bv. viciae) and Rhizobium etli bv. phaseoli could establish symbioses with S. flavescens, providing further evidence that S. flavescens is an extremely promiscuous legume and it does not have strict selectivity on either the symbiotic genes or the species-determining housekeeping genes of rhizobia. Root-hair infection is found as the pattern that rhizobia have gained entry into the curled root hairs. Electron microscopies of ultra-thin sections of S. flavescens root nodules formed by different rhizobia show that the bacteroids are regular or irregular rod shape and nonswollen types. Some bacteroids contain poly-β-hydroxybutyrate (PHB), while others do not, indicating the synthesis of PHB in bacteroids is rhizobia-dependent. The extremely promiscuous symbiosis between S. flavescens and different rhizobia provide us a basis for future studies aimed at understanding the molecular interactions of rhizobia and legumes.

  7. Antioxidant treatments counteract the non-culturability of bacterial endophytes isolated from legume nodules.

    PubMed

    Muresu, Rosella; Tondello, Alessandra; Polone, Elisa; Sulas, Leonardo; Baldan, Barbara; Squartini, Andrea

    2013-06-01

    In many wild legumes, attempts to cultivate nodule bacteria fail. We hypothesized that the limited culturability could be related to injury from oxidative stress caused by disruption of plant tissues during isolation. To test that, we isolated bacteria from nodules of Hedysarum spinosissimum and Tetragonolobus purpureus using buffers supplemented with scavenging systems to prevent damage from reactive oxygen species (ROS). Treatments included the following: antioxidants (glutathione, ascorbate, EDTA) or enzymes (catalase, peroxidase, superoxide dismutase), tested either as modified squashing buffers or added in plates. Some combinations yielded dramatic increases of culturability. Different endophytes were found, including additional Rhizobiaceae that were not the primary symbiont and were unable to nodulate. Their H2O2 tolerance in broth culture showed differences consistent with the unequal culturability observed. In wild legumes species, ROS generation during extraction appears to be a major factor limiting microbiota isolation, and protocols presented here significantly improve the recovery of culturable bacterial endophytes from plants.

  8. Nodulation gene factors and plant response in the Rhizobium-legume symbiosis. [Nodulation

    SciTech Connect

    Long, S.R.

    1990-01-01

    Our original application aimed to identify genes outside the common nod region involved in nodulation and host range of alfalfa. This has been revised by adding other studies on nodulation gene action and removing molecular studies of gene action. Our restated goals and progress are as follows. An early goal was identification and characterization of additional nodulation genes. By means of transposon mutagenesis, mapping and marker exchange we have established 87 independent mutations in a 20kb area represented by plasmid pRmJT5. We discovered four new genes: nodP, nodD3, syrA and syrM. The sequence, start site and protein product for nodFe, nodG, and nodH were also identified. Regulation of nod FEGH was studied. nod FEGH can be induced by luteolin in the presence of noodle; nodD1; noD3 and syrM, a symbiotic regulator gene also increase transcription of nod FEGH. syrA will interact with syrM; syrM also regulates exopolysaccharide genes and is believed to be a master regulator. As part of these studies, an in vitro transcription/translation system for Rhizobium was developed. Adjacent to nodP we discussed nodQ, nodPQ occurrs in two highly consumed copies. nodQ appears by sequence analysis to be similar to initiation and elongation factors, with the highest homology in the GDP binding domain. We have also investigated the nod strain, WL131. WL131 has an insertion, ISRm3, interrupting nodG, and a nonsase mutation in nodH, nodH is responsible for the lack of nodulation. We are currently investigating supernatant factors, host range effects C by spot inoculation, glucaronidase fusion proteins, and are developing, a single root hair inoculation protocol. 7 refs., 6 figs., 1 tab.

  9. Characterization and diversity of rhizobia nodulating selected tree legumes in Ghana.

    PubMed

    Boakye, Emmanuel Yaw; Lawson, Innocent Yao Dotse; Danso, Seth Kofi Akyea; Offei, Samuel Kwame

    The study was conducted to assess the characteristics and diversity of the rhizobia that nodulate some prominent tree legumes in three soils of Ghana. Five introduced and/or indigenous tree legumes were initially assessed for nodulation in three Ghanaian soils. After 12 weeks of growth in nursery pots the 200 rhizobial strains isolated from their nodules were characterized culturally, metabolically and phenotypically. Sixty of these isolates were selected randomly and their genotypic characteristics determined using PCR-RFLP of 16S rRNA and intergenic spacer (ITS) genes. Each tree legume was nodulated by isolates classified as fast or very fast-growers or by isolates classified as slow- or very slow-growers with 54 % of all the 200 isolates belonging to fast- or very fast-growers. Morphologically, eighty five percent of the colonies formed on yeast extract mannitol agar were wet and gummy while 70 % were acid tolerant, i.e. they were able to grow at a pH of 3.5. Combined restriction of the 16S rRNA genes of the 60 rhizobial isolates with five restriction enzymes clearly distinguished seven different clusters at 80 % similarity level. The majority of A. lebbeck isolates were distinct from those of the Acacias and L. leucocephala. The M. thonningii isolates were related to L. leucocephala isolates. Simple PCR of the ITS DNA provided several distinct band sizes indicating great variation among the isolates and restriction of the ITS with three different enzymes did not yield many further differences. Molecular techniques revealed a great diversity among the rhizobia that nodulate tree legumes in the tropics and this may explain why many introduced and/or indigenous trees are able to form nodules with indigenous rhizobia in this region.

  10. A New Species of Devosia That Forms a Unique Nitrogen-Fixing Root-Nodule Symbiosis with the Aquatic Legume Neptunia natans (L.f.) Druce

    PubMed Central

    Rivas, Raul; Velázquez, Encarna; Willems, Anne; Vizcaíno, Nieves; Subba-Rao, Nanjappa S.; Mateos, Pedro F.; Gillis, Monique; Dazzo, Frank B.; Martínez-Molina, Eustoquio

    2002-01-01

    Rhizobia are the common bacterial symbionts that form nitrogen-fixing root nodules in legumes. However, recently other bacteria have been shown to nodulate and fix nitrogen symbiotically with these plants. Neptunia natans is an aquatic legume indigenous to tropical and subtropical regions and in African soils is nodulated by Allorhizobium undicola. This legume develops an unusual root-nodule symbiosis on floating stems in aquatic environments through a unique infection process. Here, we analyzed the low-molecular-weight RNA and 16S ribosomal DNA (rDNA) sequence of the same fast-growing isolates from India that were previously used to define the developmental morphology of the unique infection process in this symbiosis with N. natans and found that they are phylogenetically located in the genus Devosia, not Allorhizobium or Rhizobium. The 16S rDNA sequences of these two Neptunia-nodulating Devosia strains differ from the only species currently described in that genus, Devosia riboflavina. From the same isolated colonies, we also located their nodD and nifH genes involved in nodulation and nitrogen fixation on a plasmid of approximately 170 kb. Sequence analysis showed that their nodD and nifH genes are most closely related to nodD and nifH of Rhizobium tropici, suggesting that this newly described Neptunia-nodulating Devosia species may have acquired these symbiotic genes by horizontal transfer. PMID:12406707

  11. Search for Nodulation and Nodule Development-Related Cystatin Genes in the Genome of Soybean (Glycine max)

    PubMed Central

    Yuan, Songli; Li, Rong; Wang, Lei; Chen, Haifeng; Zhang, Chanjuan; Chen, Limiao; Hao, Qingnan; Shan, Zhihui; Zhang, Xiaojuan; Chen, Shuilian; Yang, Zhonglu; Qiu, Dezhen; Zhou, Xinan

    2016-01-01

    Nodulation, nodule development and senescence directly affects nitrogen fixation efficiency, and previous studies have shown that inhibition of some cysteine proteases delay nodule senescence, so their nature inhibitors, cystatin genes, are very important in nodulation, nodule development, and senescence. Although several cystatins are actively transcribed in soybean nodules, their exact roles and functional diversities in legume have not been well explored in genome-wide survey studies. In this report, we performed a genome-wide survey of cystatin family genes to explore their relationship to nodulation and nodule development in soybean and identified 20 cystatin genes that encode peptides with 97–245 amino acid residues, different isoelectric points (pI) and structure characteristics, and various putative plant regulatory elements in 3000 bp putative promoter fragments upstream of the 20 soybean cystatins in response to different abiotic/biotic stresses, hormone signals, and symbiosis signals. The expression profiles of these cystatin genes in soybean symbiosis with rhizobium strain Bradyrhizobium japonicum strain 113-2 revealed that 7 cystatin family genes play different roles in nodulation as well as nodule development and senescence. However, these genes were not root nodule symbiosis (RNS)—specific and did not encode special clade cystatin protein with structures related to nodulation and nodule development. Besides, only two of these soybean cystatins were not upregulated in symbiosis after ABA treatment. The functional analysis showed that a candidate gene Glyma.15G227500 (GmCYS16) was likely to play a positive role in soybean nodulation. Besides, evolutionary relationships analysis divided the cystatin genes from Arabidopsis thaliana, Nicotiana tabacum, rice, barley and four legume plants into three groups. Interestingly, Group A cystatins are special in legume plants, but only include one of the above-mentioned 7 cystatin genes related to nodulation

  12. Search for Nodulation and Nodule Development-Related Cystatin Genes in the Genome of Soybean (Glycine max).

    PubMed

    Yuan, Songli; Li, Rong; Wang, Lei; Chen, Haifeng; Zhang, Chanjuan; Chen, Limiao; Hao, Qingnan; Shan, Zhihui; Zhang, Xiaojuan; Chen, Shuilian; Yang, Zhonglu; Qiu, Dezhen; Zhou, Xinan

    2016-01-01

    Nodulation, nodule development and senescence directly affects nitrogen fixation efficiency, and previous studies have shown that inhibition of some cysteine proteases delay nodule senescence, so their nature inhibitors, cystatin genes, are very important in nodulation, nodule development, and senescence. Although several cystatins are actively transcribed in soybean nodules, their exact roles and functional diversities in legume have not been well explored in genome-wide survey studies. In this report, we performed a genome-wide survey of cystatin family genes to explore their relationship to nodulation and nodule development in soybean and identified 20 cystatin genes that encode peptides with 97-245 amino acid residues, different isoelectric points (pI) and structure characteristics, and various putative plant regulatory elements in 3000 bp putative promoter fragments upstream of the 20 soybean cystatins in response to different abiotic/biotic stresses, hormone signals, and symbiosis signals. The expression profiles of these cystatin genes in soybean symbiosis with rhizobium strain Bradyrhizobium japonicum strain 113-2 revealed that 7 cystatin family genes play different roles in nodulation as well as nodule development and senescence. However, these genes were not root nodule symbiosis (RNS)-specific and did not encode special clade cystatin protein with structures related to nodulation and nodule development. Besides, only two of these soybean cystatins were not upregulated in symbiosis after ABA treatment. The functional analysis showed that a candidate gene Glyma.15G227500 (GmCYS16) was likely to play a positive role in soybean nodulation. Besides, evolutionary relationships analysis divided the cystatin genes from Arabidopsis thaliana, Nicotiana tabacum, rice, barley and four legume plants into three groups. Interestingly, Group A cystatins are special in legume plants, but only include one of the above-mentioned 7 cystatin genes related to nodulation and

  13. SCARN a Novel Class of SCAR Protein That Is Required for Root-Hair Infection during Legume Nodulation.

    PubMed

    Qiu, Liping; Lin, Jie-Shun; Xu, Ji; Sato, Shusei; Parniske, Martin; Wang, Trevor L; Downie, J Allan; Xie, Fang

    2015-10-01

    Rhizobial infection of legume root hairs requires a rearrangement of the actin cytoskeleton to enable the establishment of plant-made infection structures called infection threads. In the SCAR/WAVE (Suppressor of cAMP receptor defect/WASP family verpolin homologous protein) actin regulatory complex, the conserved N-terminal domains of SCAR proteins interact with other components of the SCAR/WAVE complex. The conserved C-terminal domains of SCAR proteins bind to and activate the actin-related protein 2/3 (ARP2/3) complex, which can bind to actin filaments catalyzing new actin filament formation by nucleating actin branching. We have identified, SCARN (SCAR-Nodulation), a gene required for root hair infection of Lotus japonicus by Mesorhizobium loti. Although the SCARN protein is related to Arabidopsis thaliana SCAR2 and SCAR4, it belongs to a distinct legume-sub clade. We identified other SCARN-like proteins in legumes and phylogeny analyses suggested that SCARN may have arisen from a gene duplication and acquired specialized functions in root nodule symbiosis. Mutation of SCARN reduced formation of infection-threads and their extension into the root cortex and slightly reduced root-hair length. Surprisingly two of the scarn mutants showed constitutive branching of root hairs in uninoculated plants. However we observed no effect of scarn mutations on trichome development or on the early actin cytoskeletal accumulation that is normally seen in root hair tips shortly after M. loti inoculation, distinguishing them from other symbiosis mutations affecting actin nucleation. The C-terminal domain of SCARN binds to ARPC3 and ectopic expression of the N-terminal SCAR-homology domain (but not the full length protein) inhibited nodulation. In addition, we found that SCARN expression is enhanced by M. loti in epidermal cells and that this is directly regulated by the NODULE INCEPTION (NIN) transcription factor.

  14. SCARN a Novel Class of SCAR Protein That Is Required for Root-Hair Infection during Legume Nodulation

    PubMed Central

    Qiu, Liping; Lin, Jie-shun; Xu, Ji; Sato, Shusei; Parniske, Martin; Wang, Trevor L.; Downie, J. Allan; Xie, Fang

    2015-01-01

    Rhizobial infection of legume root hairs requires a rearrangement of the actin cytoskeleton to enable the establishment of plant-made infection structures called infection threads. In the SCAR/WAVE (Suppressor of cAMP receptor defect/WASP family verpolin homologous protein) actin regulatory complex, the conserved N-terminal domains of SCAR proteins interact with other components of the SCAR/WAVE complex. The conserved C-terminal domains of SCAR proteins bind to and activate the actin-related protein 2/3 (ARP2/3) complex, which can bind to actin filaments catalyzing new actin filament formation by nucleating actin branching. We have identified, SCARN (SCAR-Nodulation), a gene required for root hair infection of Lotus japonicus by Mesorhizobium loti. Although the SCARN protein is related to Arabidopsis thaliana SCAR2 and SCAR4, it belongs to a distinct legume-sub clade. We identified other SCARN-like proteins in legumes and phylogeny analyses suggested that SCARN may have arisen from a gene duplication and acquired specialized functions in root nodule symbiosis. Mutation of SCARN reduced formation of infection-threads and their extension into the root cortex and slightly reduced root-hair length. Surprisingly two of the scarn mutants showed constitutive branching of root hairs in uninoculated plants. However we observed no effect of scarn mutations on trichome development or on the early actin cytoskeletal accumulation that is normally seen in root hair tips shortly after M. loti inoculation, distinguishing them from other symbiosis mutations affecting actin nucleation. The C-terminal domain of SCARN binds to ARPC3 and ectopic expression of the N-terminal SCAR-homology domain (but not the full length protein) inhibited nodulation. In addition, we found that SCARN expression is enhanced by M. loti in epidermal cells and that this is directly regulated by the NODULE INCEPTION (NIN) transcription factor. PMID:26517270

  15. Phylogenetic relationship of Lotus uliginosus symbionts with bradyrhizobia nodulating genistoid legumes.

    PubMed

    Lorite, María J; Videira e Castro, Isabel; Muñoz, Socorro; Sanjuán, Juan

    2012-02-01

    Lotus species are legumes with potential for pastures in soils with low-fertility and environmental constraints. The aim of this work was to characterize bacteria that establish efficient nitrogen-fixing symbiosis with the forage species Lotus uliginosus. A total of 39 isolates were obtained from nodules of L. uliginosus naturally growing in two different locations of Portugal. Molecular identification of the isolates plus the commercial inoculant strain NZP2039 was performed by REP-PCR, 16S rRNA RFLP, and 16S rRNA, glnII and recA sequence analyses. Limited genetic diversity was found among the L. uliginosus symbionts, which showed a close phylogenetic relationship with the species Bradyrhizobium japonicum. The symbiotic nifH, nodA and nodC gene sequences were closely related with the corresponding genes of various Bradyrhizobium strains isolated from Lupinus and other genistoid legumes and therefore were phylogenetically separated from other Lotus spp. rhizobia. The L. uliginosus bradyrhizobia were able to nodulate and fix nitrogen in association with L. uliginosus, could nodulate Lotus corniculatus with generally poor nitrogen-fixing efficiency, formed nonfixing nodules in Lotus tenuis and Lupinus luteus roots and were unable to nodulate Glycine soja or Glycine max. Thus, L. uliginosus rhizobia seem closely related to B. japonicum biovar genistearum strains.

  16. The genetic and biochemical basis for nodulation of legumes by rhizobia

    SciTech Connect

    Pueppke, S.G.

    1996-05-01

    Soil bacteria of the genera Azorhizobium, Bradyrhizobium, and Rhizobium are collectively termed rhizobia. They share the ability to penetrate legume roots and elicit morphological responses that lead to the appearance of nodules. Bacteria within these symbiotic structures fix atmosphere nitrogen and thus are of immense ecological and agricultural significance. Although modern genetic analysis of rhizobia began less than 20 years ago, dozens of nodulation genes have now been identified, some in multiple species of rhizobia. These genetic advances have led to the discovery of a host surveillance system encoded by nodD and to the identification of Nod factor signals. These derivatives of oligochitin are synthesized by the protein products of nodABC, nodFE, NodPQ, and other nodulation genes: they provoke symbiotic responses on the part of the host and have generated immense interest in recent years. The symbiotic functions of other nodulation genes are nonetheless uncertain, and there remain significant gaps in the knowledge of several large groups of rhizobia with interesting biological properties. This review focuses on the nodulation genes of rhizobia, with particular emphasis on the concept of biological specificity of symbiosis with legume host plants. 419 refs.

  17. Construction of a marker system for the evaluation of competitiveness for legume nodulation in Rhizobium strains.

    PubMed

    Sánchez-Cañizares, Carmen; Palacios, Jose

    2013-03-01

    A marker system has been set up for the analysis of competitiveness of Rhizobium leguminosarum strains for legume nodulation. The strains generated incorporate gusA and celB marker genes at identical positions and allow efficient scoring of single and double infections. Based on this system, we have found that strain UPM791 outcompetes 3841 for nodulation in pea. This technique will be useful to determine the effect of different traits on competitiveness. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Multiple polyploidy events in the early radiation of nodulating and nonnodulating legumes.

    PubMed

    Cannon, Steven B; McKain, Michael R; Harkess, Alex; Nelson, Matthew N; Dash, Sudhansu; Deyholos, Michael K; Peng, Yanhui; Joyce, Blake; Stewart, Charles N; Rolf, Megan; Kutchan, Toni; Tan, Xuemei; Chen, Cui; Zhang, Yong; Carpenter, Eric; Wong, Gane Ka-Shu; Doyle, Jeff J; Leebens-Mack, Jim

    2015-01-01

    Unresolved questions about evolution of the large and diverse legume family include the timing of polyploidy (whole-genome duplication; WGDs) relative to the origin of the major lineages within the Fabaceae and to the origin of symbiotic nitrogen fixation. Previous work has established that a WGD affects most lineages in the Papilionoideae and occurred sometime after the divergence of the papilionoid and mimosoid clades, but the exact timing has been unknown. The history of WGD has also not been established for legume lineages outside the Papilionoideae. We investigated the presence and timing of WGDs in the legumes by querying thousands of phylogenetic trees constructed from transcriptome and genome data from 20 diverse legumes and 17 outgroup species. The timing of duplications in the gene trees indicates that the papilionoid WGD occurred in the common ancestor of all papilionoids. The earliest diverging lineages of the Papilionoideae include both nodulating taxa, such as the genistoids (e.g., lupin), dalbergioids (e.g., peanut), phaseoloids (e.g., beans), and galegoids (=Hologalegina, e.g., clovers), and clades with nonnodulating taxa including Xanthocercis and Cladrastis (evaluated in this study). We also found evidence for several independent WGDs near the base of other major legume lineages, including the Mimosoideae-Cassiinae-Caesalpinieae (MCC), Detarieae, and Cercideae clades. Nodulation is found in the MCC and papilionoid clades, both of which experienced ancestral WGDs. However, there are numerous nonnodulating lineages in both clades, making it unclear whether the phylogenetic distribution of nodulation is due to independent gains or a single origin followed by multiple losses.

  19. Multiple Polyploidy Events in the Early Radiation of Nodulating and Nonnodulating Legumes

    PubMed Central

    Cannon, Steven B.; McKain, Michael R.; Harkess, Alex; Nelson, Matthew N.; Dash, Sudhansu; Deyholos, Michael K.; Peng, Yanhui; Joyce, Blake; Stewart, Charles N.; Rolf, Megan; Kutchan, Toni; Tan, Xuemei; Chen, Cui; Zhang, Yong; Carpenter, Eric; Wong, Gane Ka-Shu; Doyle, Jeff J.; Leebens-Mack, Jim

    2015-01-01

    Unresolved questions about evolution of the large and diverse legume family include the timing of polyploidy (whole-genome duplication; WGDs) relative to the origin of the major lineages within the Fabaceae and to the origin of symbiotic nitrogen fixation. Previous work has established that a WGD affects most lineages in the Papilionoideae and occurred sometime after the divergence of the papilionoid and mimosoid clades, but the exact timing has been unknown. The history of WGD has also not been established for legume lineages outside the Papilionoideae. We investigated the presence and timing of WGDs in the legumes by querying thousands of phylogenetic trees constructed from transcriptome and genome data from 20 diverse legumes and 17 outgroup species. The timing of duplications in the gene trees indicates that the papilionoid WGD occurred in the common ancestor of all papilionoids. The earliest diverging lineages of the Papilionoideae include both nodulating taxa, such as the genistoids (e.g., lupin), dalbergioids (e.g., peanut), phaseoloids (e.g., beans), and galegoids (=Hologalegina, e.g., clovers), and clades with nonnodulating taxa including Xanthocercis and Cladrastis (evaluated in this study). We also found evidence for several independent WGDs near the base of other major legume lineages, including the Mimosoideae–Cassiinae–Caesalpinieae (MCC), Detarieae, and Cercideae clades. Nodulation is found in the MCC and papilionoid clades, both of which experienced ancestral WGDs. However, there are numerous nonnodulating lineages in both clades, making it unclear whether the phylogenetic distribution of nodulation is due to independent gains or a single origin followed by multiple losses. PMID:25349287

  20. Carbon metabolism in legume nodules. Progress report, June 1, 1982-January 30, 1983

    SciTech Connect

    LaRue, T.A.

    1983-02-01

    The oxidation and reduction of flavins and pyridine nucleotides in intact bacteria can be monitored by their changes in fluorescence. This technique permits study in nitrogen fixing bacteria of the effect of inhibitors of electron transport, and of the effect of substrates which may provide reductant for nitrogenase or oxidative phosphorylation. The nitrogen fixing ability of intact legume plants or bacteroids isolated from nodules can be manipulated downward by appropriate brief treatment of supra-optimal oxygen concentrations.

  1. Legume genomics: promise versus reality

    USDA-ARS?s Scientific Manuscript database

    Legume root nodules, the specialized organs in which symbiotic nitrogen fixation (SNF) occurs, are structurally and metabolically complex organs. Their development and function depends upon coordinated gene expression between the host plant and rhizobial partner. Depending upon the symbiosis, nodule...

  2. Transition metals in legume root nodules: iron-dependent free radical production increases during nodule senescence.

    PubMed Central

    Becana, M; Klucas, R V

    1992-01-01

    The cytosol from root nodules of soybean, bean, and cowpea contained Fe and Cu capable of catalyzing the formation of highly reactive free radicals. Specific and sensitive assays based on free radical-mediated DNA degradation revealed that most catalytic Fe and Cu were present as small chelates (300-600 Da). The involvement of catalytic Fe in free radical production during nodule senescence, which was induced by exposure of plants to continuous darkness for 2-4 days, was investigated. (i) Free heme remained at a constant and low concentration (1-4% of total nodule heme) during senescence, indicating that it is not an important constituent of the catalytic Fe pool of nodules. (ii) Catalytic Fe of nodule cytosol promoted deoxyribose degradation and linolenic acid peroxidation in reaction mixtures containing physiological concentrations of ascorbate and H2O2. Deoxyribose degradation but not lipid peroxidation required hydroxyl radicals to proceed. (iii) The cytosol from senescent nodules, particularly of bean and cowpea, sustained in vitro higher rates of deoxyribose degradation and lipid peroxidation than the cytosol from unstressed nodules. Both degradative processes were inhibited by the Fe chelator desferrioxamine and were correlated with the content of catalytic Fe in the nodule cytosol. (iv) Although other transition metals (Cu, Mn, Mo, and Ni) were present in significant amounts in the low molecular mass fraction (<3 kDa) of the nodule cytosol, Fe is most likely the only metal involved in free radical generation in vivo. (v) By using dimethyl sulfoxide as a molecular probe, formation of significant amounts of hydroxyl radical was observed in vivo during senescence of bean and cowpea nodules. Images PMID:11607326

  3. Bioproduction of ascorbic acid in root nodule and root of the legume pulse Phaseolus mungo.

    PubMed

    Ghosh, S; Maiti, T K; Basu, P S

    2008-05-01

    The root nodules of Phaseolus mungo (L.), a herbaceous leguminous pulse, contain high amounts of ascorbic acid (AsA). A glucose pool present in the nodule might serve as precursor for AsA production. From root nodule, a Rhizobium sp. was isolated. The symbiont produced a large amount of AsA (290.5 microg/ml) from glucose-supplemented basal medium. The production of AsA by the symbiont was much greater than that of the control when the glucose (0.5%)-supplemented mineral medium was enriched with thiamine hydrochloride (20 microg/100 ml), biotin (20 microg/100 ml), and L-asparagine (0.2%). The possible role of the rhizobial production of AsA on rhizobia-legume symbiosis is discussed.

  4. Distinct Bradyrhizobium [corrected] communities nodulate legumes native to temperate and tropical monsoon Australia.

    PubMed

    Stępkowski, Tomasz; Watkin, Elizabeth; McInnes, Alison; Gurda, Dorota; Gracz, Joanna; Steenkamp, Emma T

    2012-05-01

    Geographic isolation and growing climate aridity played major roles in the evolution of Australian legumes. It is likely that these two factors also impacted on the evolution of their root-nodule bacteria. To investigate this issue, we applied a multilocus sequence analysis (MLSA) approach to examine Bradyrhizobium isolates originating from temperate areas of Western Australia (WA) and the tropical-monsoon area of the Northern Territory (NT). The isolates were mostly collected from the nodules of legumes belonging to tribes, genera and species endemic or native to Australia. Phylogenetic analyses of sequences for the housekeeping atpD, dnaK, glnII, gyrB, recA and 16S rRNA genes and nodulation nodA gene revealed that most isolates belonged to groups that are distinct from non-Australian Bradyrhizobium isolates, which is in line with earlier studies based on 16S rRNA gene sequence analyses. Phylogenetic analysis of the nodA data allowed identification of five major Clades among the WA and NT isolates. All WA isolates grouped in a subgroup I.1 of Clade I with strains originating from temperate eastern Australia. In contrast, the NT isolates formed part of Clades I (subgroup I.2), III (subgroup III.3), IV, V and X. Of these nodA clades, Clade I, Clade IV, Clade X presumably have an Australian origin. Overall, these data demonstrate that the impact of geographic isolation of the Australian landmass is manifested by the presence of numerous unique clusters in housekeeping and nodulation gene trees. In addition, the intrinsic climate characteristics of temperate WA and tropical-monsoon NT were responsible for the formation of distinct legume communities selecting for unrelated Bradyrhizobium groups. Copyright © 2011 Elsevier Inc. All rights reserved.

  5. Multiple polyploidy events in the early radiation of nodulating and non-nodulating legumes

    USDA-ARS?s Scientific Manuscript database

    Unresolved questions about evolution of the large and diverse legume family include the timing of polyploidy (whole-genome duplication; WGDs) relative to the origin of the major lineages within the Fabaceae and to the origin of symbiotic nitrogen fixation. Previous work has established that a WGD af...

  6. Mitochondria are an early target of oxidative modifications in senescing legume nodules.

    PubMed

    Matamoros, Manuel A; Fernández-García, Nieves; Wienkoop, Stefanie; Loscos, Jorge; Saiz, Ana; Becana, Manuel

    2013-02-01

    Legume nodule senescence is a poorly understood process involving a decrease in N(2) fixation and an increase in proteolytic activity. Some physiological changes during nodule aging have been reported, but scarce information is available at the subcellular level. Biochemical, immunological and proteomic approaches were used to provide insight into the effects of aging on the mitochondria and cytosol of nodule host cells. In the mitochondria, the oxidative modification of lipids and proteins was associated with a marked decline in glutathione, a reduced capacity to regenerate ascorbate, and upregulation of alternative oxidase and manganese superoxide dismutase. In the cytosol, there were consistent reductions in the protein concentrations of carbon metabolism enzymes, inhibition of protein synthesis and increase in serine proteinase activity, disorganization of cytoskeleton, and a sharp reduction of cytosolic proteins, but no detectable accumulation of oxidized molecules. We conclude that nodule mitochondria are an early target of oxidative modifications and a likely source of redox signals. Alternative oxidase and manganese superoxide dismutase may play important roles in controlling ROS concentrations and the redox state of mitochondria. The finding that specific methionine residues of a cytosolic glutamine synthetase isoform are sulfoxidized suggests a regulatory role of this enzyme in senescing nodules.

  7. Improving legume nodulation and Cu rhizostabilization using a genetically modified rhizobia.

    PubMed

    Delgadillo, Julián; Lafuente, Alejandro; Doukkali, Bouchra; Redondo-Gómez, Susana; Mateos-Naranjo, Enrique; Caviedes, Miguel A; Pajuelo, Eloísa; Rodríguez-Llorente, Ignacio D

    2015-01-01

    The rhizobia-legume interaction has been proposed as an interesting and appropriate tool for rhizostabilization of soils contaminated with heavy metals. One of the main requirements to use this symbiosis is the availability of tolerant and symbiotically effective rhizobia. The aim of this work was to improve the symbiotic properties of the arsenic-resistant wild-type strain Ensifer medicae MA11 in Cu-contaminated substrates. The copAB genes from a Cu-resistant Pseudomonas fluorescens strain were expressed in E. medicae MA11 under the control of the nifH promoter. The resulting strain E. medicae MA11-copAB was able to alleviate the toxic effect of Cu in Medicago truncatula. At 300 µM Cu, root and shoot dry matter production, nitrogen content, number of nodules and photosynthetic rate were significantly reduced in plants inoculated with the wild-type strain. However, these parameters were not altered in plants inoculated with the genetically modified strain. Moreover, nodules elicited by this strain were able to accumulate twofold the Cu measured in nodules formed by the wild-type strain. In addition, the engineered E. medicae strain increased Cu accumulation in roots and decreased the content in shoots. Thus, E. medicae MA11-copAB increased the capacity of M. truncatula to rhizostabilize Cu, decreasing the translocation factor and avoiding metal entry into the food chain. The plasmid containing the nifH promoter-copAB construct could be a useful biotool for Cu rhizostabilization using legumes, since it can be transferred to different rhizobia microsymbionts of authoctonous legumes growing in Cu-contaminated soils.

  8. Prevalence of Burkholderia sp. nodule symbionts on four mimosoid legumes from Barro Colorado Island, Panama.

    PubMed

    Barrett, Craig F; Parker, Matthew A

    2005-01-01

    Sequences of 16S rRNA and partial 23S rRNA genes and PCR assays with genotype-specific primers indicated that bacteria in the genus Burkholderia were the predominant root nodule symbionts for four mimosoid legumes (Mimosa pigra, M. casta, M. pudica, and Abarema macradenia) on Barro Colorado Island, Panama. Among 51 isolates from these and a fifth mimosoid host (Pithecellobium hymenaeafolium), 44 were Burkholderia strains while the rest were placed in Rhizobium, Mesorhizobium, or Bradyrhizobium. The Burkholderia strains displayed four distinct rRNA sequence types, ranging from 89% to 97% similarity for 23S rRNA and 96.5-98.4% for 16S rRNA. The most common genotype comprised 53% of all isolates sampled and was associated with three legume host species. All Burkholderia genotypes formed nodules on Macroptilium atropurpureum or Mimosa pigra, and sequencing of rRNA genes in strains re-isolated from nodules verified identity with inoculant strains. Sequence analysis of the nitrogenase alpha-subunit gene (nifD) in two of the Burkholderia genotypes indicated that they were most similar to a partial sequence from the nodule-forming strain Burkholderia tuberum STM 678 from South Africa. In addition, a PCR screen with primers specific to Burkholderia nodB genes yielded the expected amplification product in most strains. Comparison of 16S rRNA and partial 23S rRNA phylogenies indicated that tree topologies were significantly incongruent. This implies that relationships across the rRNA region may have been altered by lateral gene transfer events in this Burkholderia population.

  9. Conserved nodulation genes from the non-legume symbiont Bradyrhizobium sp. (Parasponia).

    PubMed Central

    Scott, K F

    1986-01-01

    A nodulation locus from the broad-host-range, non-legume symbiont Bradyrhizobium sp. (Parasponia) strain ANU289, has been identified by hybridisation to cloned Rhizobium trifolii nodulation (nod) genes. Transfer of cloned ANU289 nod genes to R.trifolii nodulation-deficient mutants showed that the locus contains a functional homologue of the R. trifolii nodD gene. DNA sequence analysis revealed the presence of three additional genes nodA, nodB and nodC clustered adjacent to nodD. The four genes from ANU289 share substantial sequence homology with those characterised from narrow-host-range Rhizobium strains. A novel 700-bp sequence inserted between the nodD and nodABC genes encodes an open reading frame designated nodK and is oriented in the same direction as nodABC. nodKABC appear to be organized in a single transcriptional unit and nodD is oriented divergently to nodKABC. A 35-bp sequence containing the ribosome binding site for the nodD gene and an AT-rich core sequence has been identified by comparison with sequences from other Rhizobium strains and is likely to be implicated in the plant-mediated induction of nodulation gene expression. Images PMID:3960737

  10. Relevance of Fucose-Rich Extracellular Polysaccharides Produced by Rhizobium sullae Strains Nodulating Hedysarum coronarium L. Legumes

    PubMed Central

    Carpéné, Marie-Anne; Couderc, François; Benguedouar, Ammar

    2013-01-01

    Specific and complex interactions between soil bacteria, known as rhizobia, and their leguminous host plants result in the development of root nodules. This process implies a complex dialogue between the partners. Rhizobia synthesize different classes of polysaccharides: exopolysaccharides (EPS), Kdo-rich capsular polysaccharides, lipopolysaccharides, and cyclic β-(1,2)-glucans. These polymers are actors of a successful symbiosis with legumes. We focus here on studying the EPS produced by Rhizobium sullae bacteria that nodulate Hedysarum coronarium L., largely distributed in Algeria. We describe the influence of the carbon source on the production and on the composition of EPS produced by R. sullae A6 and RHF strains. High-molecular-weight EPS preserve the bacteria from desiccation. The structural characterization of the EPS produced by R. sullae strains has been performed through sugar analysis by gas chromatography-mass spectrometry. The low-molecular-weight EPS of one strain (RHF) has been totally elucidated using nuclear magnetic resonance and quantitative time-of-flight tandem mass spectrometry analyses. An unusual fucose-rich EPS has been characterized. The presence of this deoxy sugar seems to be related to nodulation capacity. PMID:23183977

  11. Relevance of fucose-rich extracellular polysaccharides produced by Rhizobium sullae strains nodulating Hedysarum coronarium l. legumes.

    PubMed

    Gharzouli, Razika; Carpéné, Marie-Anne; Couderc, François; Benguedouar, Ammar; Poinsot, Véréna

    2013-03-01

    Specific and complex interactions between soil bacteria, known as rhizobia, and their leguminous host plants result in the development of root nodules. This process implies a complex dialogue between the partners. Rhizobia synthesize different classes of polysaccharides: exopolysaccharides (EPS), Kdo-rich capsular polysaccharides, lipopolysaccharides, and cyclic β-(1,2)-glucans. These polymers are actors of a successful symbiosis with legumes. We focus here on studying the EPS produced by Rhizobium sullae bacteria that nodulate Hedysarum coronarium L., largely distributed in Algeria. We describe the influence of the carbon source on the production and on the composition of EPS produced by R. sullae A6 and RHF strains. High-molecular-weight EPS preserve the bacteria from desiccation. The structural characterization of the EPS produced by R. sullae strains has been performed through sugar analysis by gas chromatography-mass spectrometry. The low-molecular-weight EPS of one strain (RHF) has been totally elucidated using nuclear magnetic resonance and quantitative time-of-flight tandem mass spectrometry analyses. An unusual fucose-rich EPS has been characterized. The presence of this deoxy sugar seems to be related to nodulation capacity.

  12. Burkholderia kirstenboschensis sp. nov. nodulates papilionoid legumes indigenous to South Africa.

    PubMed

    Steenkamp, Emma T; van Zyl, Elritha; Beukes, Chrizelle W; Avontuur, Juanita R; Chan, Wai Yin; Palmer, Marike; Mthombeni, Lunghile S; Phalane, Francina L; Sereme, T Karabo; Venter, Stephanus N

    2015-12-01

    Despite the diversity of Burkholderia species known to nodulate legumes in introduced and native regions, relatively few taxa have been formally described. For example, the Cape Floristic Region of South Africa is thought to represent one of the major centres of diversity for the rhizobial members of Burkholderia, yet only five species have been described from legumes occurring in this region and numerous are still awaiting taxonomic treatment. Here, we investigated the taxonomic status of 12 South African root-nodulating Burkholderia isolates from native papilionoid legumes (Hypocalyptus coluteoides, H. oxalidifolius, H. sophoroides and Virgilia oroboides). Analysis of four gene regions (16S rRNA, recA, atpD and rpoB) revealed that the isolates represent a genealogically unique and exclusive assemblage within the genus. Its distinctness was supported by all other aspects of the polyphasic approach utilized, including the genome-based criteria DNA-DNA hybridization (≥70.9%) and average nucleotide identities (≥96%). We accordingly propose the name B. kirstenboschensis sp. nov. for this taxon with isolate Kb15(T) (=LMG 28727(T); =SARC 695(T)) as its type strain. Our data showed that intraspecific genome size differences (≥0.81 Mb) and the occurrence of large DNA regions that are apparently unique to single individuals (16-23% of an isolate's genome) can significantly limit the value of data obtained from DNA-DNA hybridization experiments. Substitution of DNA-DNA hybridization with whole genome sequencing as a prerequisite for the description of Burkholderia species will undoubtedly speed up the pace at which their diversity are documented, especially in hyperdiverse regions such as the Cape Floristic Region.

  13. Purification, properties, and distribution of ascorbate peroxidase in legume root nodules

    SciTech Connect

    Dalton, D.A.; Hanus, F.J.; Russell, S.A.; Evans, H.J. )

    1987-01-01

    All aerobic biological system, including N{sub 2}-fixing root nodules, are subject to O{sub 2} toxicity that results from the formation of reactive intermediates such as H{sub 2}O{sub 2} and free radicals of O{sub 2}. H{sub 2}O{sub 2} may be removed from root nodules in a series of enzymic reactions involving ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. The authors confirm here the presence of these enzymes in root nodules from nine species of legumes and from Alnus rubra. Ascorbate peroxidase from soybean nodules was purified to near homogeneity. This enzyme was found to be a hemeprotein with a molecular weight of 30,000 as determined by sodium dodecyl sulfate gel electrophoresis. KCN, NaN{sub 3}, CO, and C{sub 2}H{sub 2} were potent inhibitors of activity. Nonphysiological reductants such as guaiacol, o-dianisidine, and pyrogallol functioned as substrates for the enzyme. No activity was detected with NAD(P)H, reduced glutathione, or urate. Ascorbate peroxidation did not follow Michaelis-Menten kinetics. The substrate concentration which resulted in a reaction rate of 1/2 V{sub max} was 70 micromolar for ascorbate and 3 micromolar for H{sub 2}O{sub 2}. The high affinity of ascorbate peroxidase for H{sub 2}O{sub 2} indicates that this enzyme, rather than catalase, is responsible for most H{sub 2}O{sub 2} removal outside of peroxisomes in root nodules.

  14. Function of plasma membrane microdomain-associated proteins during legume nodulation.

    PubMed

    Qiao, Zhenzhen; Libault, Marc

    2017-08-17

    Plasma membrane microdomains are plasma membrane sub-compartments enriched in sphingolipids and sterols, and composed by a specific set of proteins. They are involved in recognizing signal molecules, transducing these signals, and controlling endocytosis and exocytosis processes. In a recent study, applying biochemical and microscopic methods, we characterized the soybean GmFWL1 protein, a major regulator of soybean nodulation, as a new membrane microdomain-associated protein. Interestingly, upon rhizobia inoculation of the soybean root system, GmFWL1 and one of its interacting partners, GmFLOT2/4, both translocate to the root hair cell tip, the primary site of interaction and infection between soybean and Rhizobium. The role of GmFWL1 as a plasma membrane microdomain-associated protein is also supported by immunoprecipitation assays performed on soybean nodules, which revealed 178 GmFWL1 protein partners including a large number of microdomain-associated proteins such as GmFLOT2/4. In this addendum, we provide additional information about the identity of the soybean proteins repetitively identified as GmFWL1 protein partners. Their function is discussed especially in regard to plant-microbe interactions and microbial symbiosis. This addendum will provide new insights in the role of plasma membrane microdomains in regulating legume nodulation.

  15. Long-term non-invasive and continuous measurements of legume nodule activity.

    PubMed

    Cabeza, Ricardo A; Liese, Rebecca; Fischinger, Stephanie A; Sulieman, Saad; Avenhaus, Ulrike; Lingner, Annika; Hein, Hans; Koester, Beke; Baumgarten, Vanessa; Dittert, Klaus; Schulze, Joachim

    2015-02-01

    Symbiotic nitrogen fixation is a process of considerable economic, ecological and scientific interest. The central enzyme nitrogenase reduces H(+) alongside N2 , and the evolving H2 allows a continuous and non-invasive in vivo measurement of nitrogenase activity. The objective of this study was to show that an elaborated set-up providing such measurements for periods as long as several weeks will produce specific insight into the nodule activity's dependence on environmental conditions and genotype features. A system was developed that allows the air-proof separation of a root/nodule and a shoot compartment. H2 evolution in the root/nodule compartment can be monitored continuously. Nutrient solution composition, temperature, CO2 concentration and humidity around the shoots can concomitantly be maintained and manipulated. Medicago truncatula plants showed vigorous growth in the system when relying on nitrogen fixation. The set-up was able to provide specific insights into nitrogen fixation. For example, nodule activity depended on the temperature in their surroundings, but not on temperature or light around shoots. Increased temperature around the nodules was able to induce higher nodule activity in darkness versus light around shoots for a period of as long as 8 h. Conditions that affected the N demand of the shoots (ammonium application, Mg or P depletion, super numeric nodules) induced consistent and complex daily rhythms in nodule activity. It was shown that long-term continuous measurements of nodule activity could be useful for revealing special features in mutants and could be of importance when synchronizing nodule harvests for complex analysis of their metabolic status. © 2014 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  16. Monitoring the colonization and infection of legume nodules by Micromonospora in co-inoculation experiments with rhizobia.

    PubMed

    Benito, Patricia; Alonso-Vega, Pablo; Aguado, Carolina; Luján, Rafael; Anzai, Yojiro; Hirsch, Ann M; Trujillo, Martha E

    2017-09-08

    The discovery that the actinobacterium Micromonospora inhabits nitrogen-fixing nodules raised questions as to its potential ecological role. The capacity of two Micromonospora strains to infect legumes other than their original host, Lupinus angustifolius, was investigated using Medicago and Trifolium as test plants. Compatible rhizobial strains were used for coinoculation of the plants because Micromonospora itself does not induce nodulation. Over 50% of nodules from each legume housed Micromonospora, and using 16S rRNA gene sequence identification, we verified that the reisolated strains corresponded to the microorganisms inoculated. Entry of the bacteria and colonization of the plant hosts were monitored using a GFP-tagged Lupac 08 mutant together with rhizobia, and by using immunogold labeling. Strain Lupac 08 was localized in plant tissues, confirming its capacity to enter and colonize all hosts. Based on studying three different plants, our results support a non-specific relationship between Micromonospora and legumes. Micromonospora Lupac 08, originally isolated from Lupinus re-enters root tissue, but only when coinoculated with the corresponding rhizobia. The ability of Micromonospora to infect and colonize different legume species and function as a potential plant-growth promoting bacterium is relevant because this microbe enhances the symbiosis without interfering with the host and its nodulating and nitrogen-fixing microbes.

  17. The potential of oil-utilizing bacterial consortia associated with legume root nodules for cleaning oily soils.

    PubMed

    Dashti, N; Khanafer, M; El-Nemr, I; Sorkhoh, N; Ali, N; Radwan, S

    2009-03-01

    The surfaces of root nodules of Vicia faba and Lupinus albus (legume crops), were colonized with bacterial consortia which utilized oil and fixed nitrogen. Such combined activities apparently make those periphytic consortia efficient contributors to bioremediation of oily nitrogen-poor desert soils. This was confirmed experimentally in this study. Thus, cultivating V. faba, L. albus and, for comparison, Solanum melongena, a nonlegume crop, separately in oily sand samples resulted in more oil attenuation than in an uncultivated sample. This effect was more pronounced with the legume crops than with the nonlegume crop. Furthermore, in flask cultures, V. faba plants with nodulated roots exhibited a higher potential for oil attenuation in the surrounding water than plants with nodule-free roots. Denaturation gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified 16S rRNA coding genes revealed that periphytic bacteria had DGGE bands not matching those of the oil-utilizing rhizospheric bacteria. Legume nodules also contained endophytic bacteria whose 16S rDNA bands did not match those of Rhizobium nor those of all other individual periphytic and rhizospheric strains. It was concluded that legume crops host on their roots bacterial consortia with a satisfactory potential for oil phytoremediation.

  18. Rhizobial acyl carrier proteins and their roles in the formation of bacterial cell-surface components that are required for the development of nitrogen-fixing root nodules on legume hosts.

    PubMed

    Geiger, Otto; López-Lara, Isabel M

    2002-03-05

    Acyl carrier protein (ACP) of Escherichia coli is a small acidic protein which functions as carrier of growing acyl chains during their biosynthesis and as donor of acyl chains during transfer to target molecules. This unique ACP of E. coli is expressed constitutively. In more complex bacteria, multiple ACPs are present, indicating a channeling of pools of multi-carbon units into different biosynthetic routes. In rhizobia, for example, besides the constitutive ACP (AcpP) involved in the biosynthesis and transfer of common fatty acids, three specialized ACPs have been reported: (1) the flavonoid-inducible nodulation protein NodF, (2) AcpXL that transfers 27-hydroxyoctacosanoic acid to a sugar backbone during lipid A biosynthesis, and (3) the RkpF protein which is required for the biosynthesis of rhizobial capsular polysaccharides. All three of those specialized rhizobial ACPs are required for the biosynthesis of cell-surface molecules that play a role in establishing the symbiotic relationship between rhizobia and their legume hosts. Surprisingly, the recently sequenced genomes from Mesorhizobium loti and Sinorhizobium meliloti suggest even more candidates for ACPs in rhizobia.

  19. Sucrose Synthase in Legume Nodules Is Essential for Nitrogen Fixation1

    PubMed Central

    Gordon, Anthony J.; Minchin, Frank R.; James, Caron L.; Komina, Olga

    1999-01-01

    The role of sucrose synthase (SS) in the fixation of N was examined in the rug4 mutant of pea (Pisum sativum L.) plants in which SS activity was severely reduced. When dependent on nodules for their N supply, the mutant plants were not viable and appeared to be incapable of effective N fixation, although nodule formation was essentially normal. In fact, N and C resources invested in nodules were much greater in mutant plants than in the wild-type (WT) plants. Low SS activity in nodules (present at only 10% of WT levels) resulted in lower amounts of total soluble protein and leghemoglobin and lower activities of several enzymes compared with WT nodules. Alkaline invertase activity was not increased to compensate for reduced SS activity. Leghemoglobin was present at less than 20% of WT values, so O2 flux may have been compromised. The two components of nitrogenase were present at normal levels in mutant nodules. However, only a trace of nitrogenase activity was detected in intact plants and none was found in isolated bacteroids. The results are discussed in relation to the role of SS in the provision of C substrates for N fixation and in the development of functional nodules. PMID:10398723

  20. Identification of fast-growing rhizobia nodulating tropical legumes from Puerto Rico as Rhizobium gallicum and Rhizobium tropici.

    PubMed

    Zurdo-Piñeiro, José Luis; Velázquez, Encarna; Lorite, María José; Brelles-Mariño, Graciela; Schröder, Eduardo C; Bedmar, Eulogio J; Mateos, Pedro F; Martínez-Molina, Eustoquio

    2004-08-01

    Fifteen isolates from several nodulated tropical legumes from Puerto Rico (USA) were characterised by their phenotypic, molecular and symbiotic features. The identification of isolates was based on a polyphasic approach, including phenotypic characteristics, 16S rRNA sequencing, Low molecular weight (LMW) RNA profiles, Two Primers-RAPD patterns, and restriction patterns from 16S rDNA molecules. Despite of the variety of hosts included in this study the 15 isolates were separated into only two groups that corresponded to Rhizobium gallicum and Rhizobium tropici. This work shows that R. gallicum and R. tropici nodulate legume plants, such as Sesbania, Caliandra, Poitea, Piptadenia, Neptunia and Mimosa species, that were not previously considered as hosts for these rhizobia. Moreover, some of these host plants can be nodulated by both species. The results confirm the great promiscuity of R. tropici and also support the hypothesis that the species R. gallicum may be native from America or cosmopolitan and worldwide spread.

  1. Novel impacts of functionalized multi-walled carbon nanotubes in plants: promotion of nodulation and nitrogenase activity in the rhizobium-legume system.

    PubMed

    Yuan, Zhaodong; Zhang, Zhongming; Wang, Xiuping; Li, Li; Cai, Kai; Han, Heyou

    2017-07-20

    The rhizobium-legume symbiosis system is critical for nitrogen-cycle balance in agriculture. However, the potential effects of carbon nanomaterials (CNMs) on this system remain largely unknown. Herein, we studied the effects of four carbon-based materials (activated carbon (AC), single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO)) on the rhizobium-legume symbiosis system consisting of Lotus japonicus and Mesorhizobium loti MAFF303099. Under non-symbiotic conditions, the bacterial growth and root development of plants were both clearly inhibited by SWCNTs and GO, while the elongation of plant stems was enhanced by MWCNTs to a certain degree. More importantly, only MWCNTs could increase the number of nodules and enhance the activity of nitrogenase in the rhizobium-plant interaction. Further analyses showed that the average number of nodules in plants treated with 100 μg mL(-1) MWCNTs was significantly increased by 39% at 14 days post inoculation (dpi) and by 41% at 28 dpi. Meanwhile, the biological nitrogen fixation of the nodules was promoted by more than 10% under 100 μg mL(-1) MWCNT treatment, which enhanced the above- and below-ground fresh biomass by 14% and 25% respectively at 28 dpi. Transmission electron microscopy images further indicated that MWCNTs penetrated the cell wall, and pierced through the cell membrane to be transmitted into the cytoplasm. In addition, gene expression analysis showed that the promotion of nodulation by MWCNTs was correlated with the up-regulation of certain genes involved in this signaling pathway. In particular, the expression of NIN, a crucial gene regulating the development of nodules, was significantly elevated 2-fold by MWCNTs at an early stage of nodulation. These findings are expected to facilitate the understanding and future utilization of MWCNTs in agriculture.

  2. NODULE INCEPTION Directly Targets NF-Y Subunit Genes to Regulate Essential Processes of Root Nodule Development in Lotus japonicus

    PubMed Central

    Soyano, Takashi; Kouchi, Hiroshi; Hirota, Atsuko; Hayashi, Makoto

    2013-01-01

    The interactions of legumes with symbiotic nitrogen-fixing bacteria cause the formation of specialized lateral root organs called root nodules. It has been postulated that this root nodule symbiosis system has recruited factors that act in early signaling pathways (common SYM genes) partly from the ancestral mycorrhizal symbiosis. However, the origins of factors needed for root nodule organogenesis are largely unknown. NODULE INCEPTION (NIN) is a nodulation-specific gene that encodes a putative transcription factor and acts downstream of the common SYM genes. Here, we identified two Nuclear Factor-Y (NF-Y) subunit genes, LjNF-YA1 and LjNF-YB1, as transcriptional targets of NIN in Lotus japonicus. These genes are expressed in root nodule primordia and their translational products interact in plant cells, indicating that they form an NF-Y complex in root nodule primordia. The knockdown of LjNF-YA1 inhibited root nodule organogenesis, as did the loss of function of NIN. Furthermore, we found that NIN overexpression induced root nodule primordium-like structures that originated from cortical cells in the absence of bacterial symbionts. Thus, NIN is a crucial factor responsible for initiating nodulation-specific symbiotic processes. In addition, ectopic expression of either NIN or the NF-Y subunit genes caused abnormal cell division during lateral root development. This indicated that the Lotus NF-Y subunits can function to stimulate cell division. Thus, transcriptional regulation by NIN, including the activation of the NF-Y subunit genes, induces cortical cell division, which is an initial step in root nodule organogenesis. Unlike the legume-specific NIN protein, NF-Y is a major CCAAT box binding protein complex that is widespread among eukaryotes. We propose that the evolution of root nodules in legume plants was associated with changes in the function of NIN. NIN has acquired functions that allow it to divert pathways involved in the regulation of cell division to

  3. Bacterial-induced calcium oscillations are common to nitrogen-fixing associations of nodulating legumes and nonlegumes.

    PubMed

    Granqvist, Emma; Sun, Jongho; Op den Camp, Rik; Pujic, Petar; Hill, Lionel; Normand, Philippe; Morris, Richard J; Downie, J Allan; Geurts, Rene; Oldroyd, Giles E D

    2015-08-01

    Plants that form root-nodule symbioses are within a monophyletic 'nitrogen-fixing' clade and associated signalling processes are shared with the arbuscular mycorrhizal symbiosis. Central to symbiotic signalling are nuclear-associated oscillations in calcium ions (Ca(2+) ), occurring in the root hairs of several legume species in response to the rhizobial Nod factor signal. In this study we expanded the species analysed for activation of Ca(2+) oscillations, including nonleguminous species within the nitrogen-fixing clade. We showed that Ca(2+) oscillations are a common feature of legumes in their association with rhizobia, while Cercis, a non-nodulating legume, does not show Ca(2+) oscillations in response to Nod factors from Sinorhizobium fredii NGR234. Parasponia andersonii, a nonlegume that can associate with rhizobia, showed Nod factor-induced calcium oscillations to S. fredii NGR234 Nod factors, but its non-nodulating sister species, Trema tomentosa, did not. Also within the nitrogen-fixing clade are actinorhizal species that associate with Frankia bacteria and we showed that Alnus glutinosa induces Ca(2+) oscillations in root hairs in response to exudates from Frankia alni, but not to S. fredii NGR234 Nod factors. We conclude that the ability to mount Ca(2+) oscillations in response to symbiotic bacteria is a common feature of nodulating species within the nitrogen-fixing clade.

  4. Applying Reversible Mutations of Nodulation and Nitrogen-Fixation Genes to Study Social Cheating in Rhizobium etli-Legume Interaction

    PubMed Central

    Wang, Hui; Zhong, Zengtao; Zhu, Jun

    2013-01-01

    Mutualisms are common in nature, though these symbioses can be quite permeable to cheaters in situations where one individual parasitizes the other by discontinuing cooperation yet still exploits the benefits of the partnership. In the Rhizobium-legume system, there are two separate contexts, namely nodulation and nitrogen fixation processes, by which resident Rhizobium individuals can benefit by cheating. Here, we constructed reversible and irreversible mutations in key nodulation and nitrogen-fixation pathways of Rhizobium etli and compared their interaction with plant hosts Phaseolus vulgaris to that of wild type. We show that R. etli reversible mutants deficient in nodulation factor production are capable of intra-specific cheating, wherein mutants exploit other Rhizobium individuals capable of producing these factors. Similarly, we show that R. etli mutants are also capable of cheating inter-specifically, colonizing the host legume yet contributing nothing to the partnership in terms of nitrogen fixation. Our findings indicate that cheating is possible in both of these frameworks, seemingly without damaging the stability of the mutualism itself. These results may potentially help explain observations suggesting that legume plants are commonly infected by multiple bacterial lineages during the nodulation process. PMID:23922937

  5. Applying reversible mutations of nodulation and nitrogen-fixation genes to study social cheating in Rhizobium etli-legume interaction.

    PubMed

    Ling, Jun; Zheng, Huiming; Katzianer, David S; Wang, Hui; Zhong, Zengtao; Zhu, Jun

    2013-01-01

    Mutualisms are common in nature, though these symbioses can be quite permeable to cheaters in situations where one individual parasitizes the other by discontinuing cooperation yet still exploits the benefits of the partnership. In the Rhizobium-legume system, there are two separate contexts, namely nodulation and nitrogen fixation processes, by which resident Rhizobium individuals can benefit by cheating. Here, we constructed reversible and irreversible mutations in key nodulation and nitrogen-fixation pathways of Rhizobium etli and compared their interaction with plant hosts Phaseolus vulgaris to that of wild type. We show that R. etli reversible mutants deficient in nodulation factor production are capable of intra-specific cheating, wherein mutants exploit other Rhizobium individuals capable of producing these factors. Similarly, we show that R. etli mutants are also capable of cheating inter-specifically, colonizing the host legume yet contributing nothing to the partnership in terms of nitrogen fixation. Our findings indicate that cheating is possible in both of these frameworks, seemingly without damaging the stability of the mutualism itself. These results may potentially help explain observations suggesting that legume plants are commonly infected by multiple bacterial lineages during the nodulation process.

  6. Nitrate inhibition of legume nodule growth and activity. I. Long term studies with a continuous supply of nitrate

    SciTech Connect

    Streeter, J.G.

    1985-02-01

    The synthesis and accumulation of nitrite has been suggested as a causative factor in the inhibition of legume nodules supplied with nitrate. Plants were grown in sand culture with a moderate level of nitrate (2.1 to 6.4 millimolar) supplied continuously from seed germination to 30 to 50 days after planting. In a comparison of nitrate treatments, a highly significant negative correlation between nitrite concentration in soybean (Glycine max (L.) Merr.) nodules and nodule fresh weight per shoot dry weight was found even when bacteroids lacked nitrate reductase (NR). However, in a comparison of two Rhizobium japonicum strains, there was only 12% as much nitrite in nodules formed by NR/sup -/ R. japonicum as in nodules formed by NR/sup +/ R. japonicum, and growth and acetylene reduction activity of both types of nodules was about equally inhibited. The very small concentration of nitrite found in P. vulgaris nodules was probably below that required for the inhibition of nitrogenase based on published in vitro experiments, and yet the specific acetylene reduction activity was inhibited 83% by nitrate. The overall results do not support the idea that nitrite plays a role in the inhibition of nodule growth and nitrogenase activity by nitrate.

  7. Compatibility of rhizobial genotypes within natural populations of Rhizobium leguminosarum biovar viciae for nodulation of host legumes.

    PubMed

    Laguerre, Gisèle; Louvrier, Philippe; Allard, Marie-Reine; Amarger, Noëlle

    2003-04-01

    Populations of Rhizobium leguminosarum biovar viciae were sampled from two bulk soils, rhizosphere, and nodules of host legumes, fava bean (Vicia faba) and pea (Pisum sativum) grown in the same soils. Additional populations nodulating peas, fava beans, and vetches (Vicia sativa) grown in other soils and fava bean-nodulating strains from various geographic sites were also analyzed. The rhizobia were characterized by repetitive extragenomic palindromic-PCR fingerprinting and/or PCR-restriction fragment length polymorphism (RFLP) of 16S-23S ribosomal DNA intergenic spacers as markers of the genomic background and PCR-RFLP of a nodulation gene region, nodD, as a marker of the symbiotic component of the genome. Pairwise comparisons showed differences among the genetic structures of the bulk soil, rhizosphere, and nodule populations and in the degree of host specificity within the Vicieae cross-inoculation group. With fava bean, the symbiotic genotype appeared to be the preponderant determinant of the success in nodule occupancy of rhizobial genotypes independently of the associated genomic background, the plant genotype, and the soil sampled. The interaction between one particular rhizobial symbiotic genotype and fava bean seems to be highly specific for nodulation and linked to the efficiency of nitrogen fixation. By contrast with bulk soil and fava bean-nodulating populations, the analysis of pea-nodulating populations showed preferential associations between genomic backgrounds and symbiotic genotypes. Both components of the rhizobial genome may influence competitiveness for nodulation of pea, and rhizosphere colonization may be a decisive step in competition for nodule occupancy.

  8. Compatibility of Rhizobial Genotypes within Natural Populations of Rhizobium leguminosarum Biovar viciae for Nodulation of Host Legumes

    PubMed Central

    Laguerre, Gisèle; Louvrier, Philippe; Allard, Marie-Reine; Amarger, Noëlle

    2003-01-01

    Populations of Rhizobium leguminosarum biovar viciae were sampled from two bulk soils, rhizosphere, and nodules of host legumes, fava bean (Vicia faba) and pea (Pisum sativum) grown in the same soils. Additional populations nodulating peas, fava beans, and vetches (Vicia sativa) grown in other soils and fava bean-nodulating strains from various geographic sites were also analyzed. The rhizobia were characterized by repetitive extragenomic palindromic-PCR fingerprinting and/or PCR-restriction fragment length polymorphism (RFLP) of 16S-23S ribosomal DNA intergenic spacers as markers of the genomic background and PCR-RFLP of a nodulation gene region, nodD, as a marker of the symbiotic component of the genome. Pairwise comparisons showed differences among the genetic structures of the bulk soil, rhizosphere, and nodule populations and in the degree of host specificity within the Vicieae cross-inoculation group. With fava bean, the symbiotic genotype appeared to be the preponderant determinant of the success in nodule occupancy of rhizobial genotypes independently of the associated genomic background, the plant genotype, and the soil sampled. The interaction between one particular rhizobial symbiotic genotype and fava bean seems to be highly specific for nodulation and linked to the efficiency of nitrogen fixation. By contrast with bulk soil and fava bean-nodulating populations, the analysis of pea-nodulating populations showed preferential associations between genomic backgrounds and symbiotic genotypes. Both components of the rhizobial genome may influence competitiveness for nodulation of pea, and rhizosphere colonization may be a decisive step in competition for nodule occupancy. PMID:12676710

  9. Phylogenetic diversity of Rhizobium strains nodulating diverse legume species growing in Ethiopia.

    PubMed

    Degefu, Tulu; Wolde-meskel, Endalkachew; Frostegård, Åsa

    2013-06-01

    The taxonomic diversity of thirty-seven Rhizobium strains, isolated from nodules of leguminous trees and herbs growing in Ethiopia, was studied using multilocus sequence analyses (MLSA) of six core and two symbiosis-related genes. Phylogenetic analysis based on the 16S rRNA gene grouped them into five clusters related to nine Rhizobium reference species (99-100% sequence similarity). In addition, two test strains occupied their own independent branches on the phylogenetic tree (AC86a2 along with R. tibeticum; 99.1% similarity and AC100b along with R. multihospitium; 99.5% similarity). One strain from Milletia ferruginea was closely related (>99%) to the genus Shinella, further corroborating earlier findings that nitrogen-fixing bacteria are distributed among phylogenetically unrelated taxa. Sequence analyses of five housekeeping genes also separated the strains into five well-supported clusters, three of which grouped with previously studied Ethiopian common bean rhizobia. Three of the five clusters could potentially be described into new species. Based on the nifH genes, most of the test strains from crop legumes were closely related to several strains of Ethiopian common bean rhizobia and other symbionts of bean plants (R. etli and R. gallicum sv. phaseoli). The grouping of the test strains based on the symbiosis-related genes was not in agreement with the housekeeping genes, signifying differences in their evolutionary history. Our earlier studies revealing a large diversity of Mesorhizobium and Ensifer microsymbionts isolated from Ethiopian legumes, together with the results from the present analysis of Rhizobium strains, suggest that this region might be a potential hotspot for rhizobial biodiversity.

  10. Unexpectedly diverse Mesorhizobium strains and Rhizobium leguminosarum nodulate native legume genera of New Zealand, while introduced legume weeds are nodulated by Bradyrhizobium species.

    PubMed

    Weir, Bevan S; Turner, Susan J; Silvester, Warwick B; Park, Duck-Chul; Young, John M

    2004-10-01

    The New Zealand native legume flora are represented by four genera, Sophora, Carmichaelia, Clianthus, and Montigena. The adventive flora of New Zealand contains several legume species introduced in the 19th century and now established as serious invasive weeds. Until now, nothing has been reported on the identification of the associated rhizobia of native or introduced legumes in New Zealand. The success of the introduced species may be due, at least in part, to the nature of their rhizobial symbioses. This study set out to address this issue by identifying rhizobial strains isolated from species of the four native legume genera and from the introduced weeds: Acacia spp. (wattles), Cytisus scoparius (broom), and Ulex europaeus (gorse). The identities of the isolates and their relationship to known rhizobia were established by comparative analysis of 16S ribosomal DNA, atpD, glnII, and recA gene sequences. Maximum-likelihood analysis of the resultant data partitioned the bacteria into three genera. Most isolates from native legumes aligned with the genus Mesorhizobium, either as members of named species or as putative novel species. The widespread distribution of strains from individual native legume genera across Mesorhizobium spp. contrasts with previous reports implying that bacterial species are specific to limited numbers of legume genera. In addition, four isolates were identified as Rhizobium leguminosarum. In contrast, all sequences from isolates from introduced weeds aligned with Bradyrhizobium species but formed clusters distinct from existing named species. These results show that native legume genera and these introduced legume genera do not have the same rhizobial populations.

  11. Genetic divergence and gene flow among Mesorhizobium strains nodulating the shrub legume Caragana.

    PubMed

    Ji, Zhaojun; Yan, Hui; Cui, Qingguo; Wang, Entao; Chen, Wenxin; Chen, Wenfeng

    2015-05-01

    Although the biogeography of rhizobia has been investigated extensively, little is known about the adaptive molecular evolution of rhizobia influenced by soil environments and selected by legumes. In this study, microevolution of Mesorhizobium strains nodulating Caragana in a semi-fixing desert belt in northern China was investigated. Five core genes-atpD, glnII, gyrB, recA, and rpoB, six heat-shock factor genes-clpA, clpB, dnaK, dnaJ, grpE, and hlsU, and five nodulation genes-nodA, nodC, nodD, nodG, and nodP, of 72 representative mesorhizobia were studied in order to determine their genetic variations. A total of 21 genospecies were defined based on the average nucleotide identity (ANI) of concatenated core genes using a threshold of 96% similarity, and by the phylogenetic analyses of the core/heat-shock factor genes. Significant genetic divergence was observed among the genospecies in the semi-fixing desert belt (areas A-E) and Yunnan province (area F), which was closely related to the environmental conditions and geographic distance. Gene flow occurred more frequently among the genospecies in areas A-E, and three sites in area B, than between area F and the other five areas. Recombination occurred among strains more frequently for heat-shock factor genes than the other genes. The results conclusively showed that the Caragana-associated mesorhizobia had divergently evolved according to their geographic distribution, and have been selected not only by the environmental conditions but also by the host plants.

  12. The identification of novel loci required for appropriate nodule development in Medicago truncatula.

    PubMed

    Domonkos, Agota; Horvath, Beatrix; Marsh, John F; Halasz, Gabor; Ayaydin, Ferhan; Oldroyd, Giles E D; Kalo, Peter

    2013-10-11

    The formation of functional symbiotic nodules is the result of a coordinated developmental program between legumes and rhizobial bacteria. Genetic analyses in legumes have been used to dissect the signaling processes required for establishing the legume-rhizobial endosymbiotic association. Compared to the early events of the symbiotic interaction, less attention has been paid to plant loci required for rhizobial colonization and the functioning of the nodule. Here we describe the identification and characterization of a number of new genetic loci in Medicago truncatula that are required for the development of effective nitrogen fixing nodules. Approximately 38,000 EMS and fast neutron mutagenized Medicago truncatula seedlings were screened for defects in symbiotic nitrogen fixation. Mutant plants impaired in nodule development and efficient nitrogen fixation were selected for further genetic and phenotypic analysis. Nine mutants completely lacking in nodule formation (Nod-) represented six complementation groups of which two novel loci have been identified. Eight mutants with ineffective nodules (Fix-) represented seven complementation groups, out of which five were new monogenic loci. The Fix- M. truncatula mutants showed symptoms of nitrogen deficiency and developed small white nodules. Microscopic analysis of Fix- nodules revealed that the mutants have defects in the release of rhizobia from infection threads, differentiation of rhizobia and maintenance of persistence of bacteria in nodule cells. Additionally, we monitored the transcriptional activity of symbiosis specific genes to define what transcriptional stage of the symbiotic process is blocked in each of the Fix- mutants. Based on the phenotypic and gene expression analysis a functional hierarchy of the FIX genes is proposed. The new symbiotic loci of M. truncatula isolated in this study provide the foundation for further characterization of the mechanisms underpinning nodulation, in particular the later

  13. Burkholderia aspalathi sp. nov., isolated from root nodules of the South African legume Aspalathus abietina Thunb.

    PubMed

    Mavengere, Natasha R; Ellis, Allan G; Le Roux, Johannes J

    2014-06-01

    During a study to investigate the diversity of rhizobia associated with native legumes in South Africa's Cape Floristic Region, a Gram-negative bacterium designated VG1C(T) was isolated from the root nodules of Aspalathus abietina Thunb. Based on phylogenetic analyses of the 16S rRNA and recA genes, VG1C(T) belongs to the genus Burkholderia, with the highest degree of sequence similarity to the type strain of Burkholderia sediminicola (98.5% and 98%, respectively). The DNA G+C content of strain VG1C(T) was 60.1 mol%, and DNA-DNA relatedness values to the type strain of closely related species were found to be substantially lower than 70%. As evidenced by results of genotypic, phenotypic and chemotaxonomic tests provided here, we conclude that isolate VG1C(T) represents a novel rhizosphere-associated species in the genus Burkholderia, for which the name Burkholderia aspalathi sp. nov. is proposed, with the type strain VG1C(T) ( = DSM 27239(T) = LMG 27731(T)).

  14. Preparation of Artificial Blood from the Extract of Legume Root Nodules, and the Creation of Artificial Latent Fingermarks in Blood Using Artificial Blood().

    PubMed

    Hong, Sungwook; Kim, Chaewon; Jeon, Soyoung; Lee, Eunhye

    2017-03-07

    Distribution of homogeneous fingermarks in blood is essential for conducting proficiency tests in forensic science. Hence, the artificial blood was prepared using the root nodule extract of Glycine max plants. The reactivity of the artificial blood with widely used human blood detection reagents was tested. Artificial latent fingermarks in blood were printed using an inkjet cartridge case filled with artificial blood solution. The artificial latent fingermarks in blood were developed with amino acid-sensitive reagents and could obtain development as prominent as the image of the master fingermark saved on the computer. Therefore, it has been confirmed that the extract of legume root nodules can be used as artificial blood, and the artificial blood can be used for the preparation of artificial latent fingermarks or footmarks in blood. © 2017 American Academy of Forensic Sciences.

  15. Legume nodules from nutrient-poor soils exhibit high plasticity of cellular phosphorus recycling and conservation during variable phosphorus supply.

    PubMed

    Vardien, Waafeka; Steenkamp, Emma T; Valentine, Alexander J

    2016-02-01

    Nitrogen fixing legumes rely on phosphorus for nodule formation, nodule function and the energy costs of fixation. Phosphorus is however very limited in soils, especially in ancient sandstone-derived soils such as those in the Cape Floristic Region of South Africa. Plants growing in such areas have evolved the ability to tolerate phosphorus stress by eliciting an array of physiological and biochemical responses. In this study we investigated the effects of phosphorus limitation on N2 fixation and phosphorus recycling in the nodules of Virgilia divaricata (Adamson), a legume native to the Cape Floristic Region. In particular, we focused on nutrient acquisition efficiencies, phosphorus fractions and the exudation and accumulation of phosphatases. Our finding indicate that during low phosphorus supply, V. divaricata internally recycles phosphorus and has a lower uptake rate of phosphorus, as well as lower levels adenylates but greater levels of phosphohydrolase exudation suggesting it engages in recycling internal nodule phosphorus pools and making use of alternate bypass routes in order to conserve phosphorus.

  16. New nodulation mutants responsible for infection thread development in Lotus japonicus.

    PubMed

    Yano, Koji; Tansengco, Myra L; Hio, Taihei; Higashi, Kuniko; Murooka, Yoshikatsu; Imaizumi-Anraku, Haruko; Kawaguchi, Masayoshi; Hayashi, Makoto

    2006-07-01

    Legume plants develop specialized root organs, the nodules, through a symbiotic interaction with rhizobia. The developmental process of nodulation is triggered by the bacterial microsymbiont but regulated systemically by the host legume plants. Using ethylmethane sulfonate mutagenesis as a tool to identify plant genes involved in symbiotic nodule development, we have isolated and analyzed five nodulation mutants, Ljsym74-3, Ljsym79-2, Ljsym79-3, Ljsym80, and Ljsym82, from the model legume Lotus japonicus. These mutants are defective in developing functional nodules and exhibit nitrogen starvation symptoms after inoculation with Mesorhizobium loti. Detailed observation revealed that infection thread development was aborted in these mutants and the nodules formed were devoid of infected cells. Mapping and complementation tests showed that Ljsym74-3, and Ljsym79-2 and Ljsym79-3, were allelic with reported mutants of L. japonicus, alb1 and crinkle, respectively. The Ljsym82 mutant is unique among the mutants because the infection thread was aborted early in its development. Ljsym74-3 and Ljsym80 were characterized as mutants with thick infection threads in short root hairs. Map-based cloning and molecular characterization of these genes will help us understand the genetic mechanism of infection thread development in L. japonicus.

  17. Increasing Nitrogen Fixation and Seed Development in Soybean Requires Complex Adjustments of Nodule Nitrogen Metabolism and Partitioning Processes.

    PubMed

    Carter, Amanda M; Tegeder, Mechthild

    2016-08-08

    Legumes are able to access atmospheric di-nitrogen (N2) through a symbiotic relationship with rhizobia that reside within root nodules. In soybean, following N2 fixation by the bacteroids, ammonia is finally reduced in uninfected cells to allantoin and allantoic acid [1]. These ureides present the primary long-distance transport forms of nitrogen (N), and are exported from nodules via the xylem for shoot N supply. Transport of allantoin and allantoic acid out of nodules requires the function of ureide permeases (UPS1) located in cells adjacent to the vasculature [2, 3]. We expressed a common bean UPS1 transporter in cortex and endodermis cells of soybean nodules and found that delivery of N from nodules to shoot, as well as seed set, was significantly increased. In addition, the number of transgenic nodules was increased and symbiotic N2 fixation per nodule was elevated, indicating that transporter function in nodule N export is a limiting step in bacterial N acquisition. Further, the transgenic nodules showed considerable increases in nodule N assimilation, ureide synthesis, and metabolite levels. This suggests complex adjustments of nodule N metabolism and partitioning processes in support of symbiotic N2 fixation. We propose that the transgenic UPS1 plants display metabolic and allocation plasticity to overcome N2 fixation and seed yield limitations. Overall, it is demonstrated that transporter function in N export from nodules is a key step for enhancing atmospheric N2 fixation and nodule function and for improving shoot N nutrition and seed development in legumes.

  18. Reactive oxygen species and ethylene play a positive role in lateral root base nodulation of a semiaquatic legume

    PubMed Central

    D'Haeze, Wim; De Rycke, Riet; Mathis, René; Goormachtig, Sofie; Pagnotta, Sophie; Verplancke, Christa; Capoen, Ward; Holsters, Marcelle

    2003-01-01

    Lateral root base nodulation on the tropical, semiaquatic legume Sesbania rostrata results from two coordinated, Nod factor-dependent processes: formation of intercellular infection pockets and induction of cell division. Infection pocket formation is associated with cell death and production of hydrogen peroxide. Pharmacological experiments showed that ethylene and reactive oxygen species mediate Nod factor responses and are required for nodule initiation, whereby induction of division and infection could not be uncoupled. Application of purified Nod factors triggered cell division, and both Nod factors and ethylene induced cavities and cell death features in the root cortex. Thus, in S. rostrata, ethylene and reactive oxygen species act downstream from the Nod factors in pathways that lead to formation of infection pockets and initiation of nodule primordia. PMID:12975522

  19. Single-plant, sterile microcosms for nodulation and growth of the legume plant Medicago truncatula with the rhizobial symbiont Sinorhizobium meliloti.

    PubMed

    Jones, Kathryn M; Mendis, Hajeewaka C; Queiroux, Clothilde

    2013-10-01

    Rhizobial bacteria form symbiotic, nitrogen-fixing nodules on the roots of compatible host legume plants. One of the most well-developed model systems for studying these interactions is the plant Medicago truncatula cv. Jemalong A17 and the rhizobial bacterium Sinorhizobium meliloti 1021. Repeated imaging of plant roots and scoring of symbiotic phenotypes requires methods that are non-destructive to either plants or bacteria. The symbiotic phenotypes of some plant and bacterial mutants become apparent after relatively short periods of growth, and do not require long-term observation of the host/symbiont interaction. However, subtle differences in symbiotic efficiency and nodule senescence phenotypes that are not apparent in the early stages of the nodulation process require relatively long growth periods before they can be scored. Several methods have been developed for long-term growth and observation of this host/symbiont pair. However, many of these methods require repeated watering, which increases the possibility of contamination by other microbes. Other methods require a relatively large space for growth of large numbers of plants. The method described here, symbiotic growth of M. truncatula/S. meliloti in sterile, single-plant microcosms, has several advantages. Plants in these microcosms have sufficient moisture and nutrients to ensure that watering is not required for up to 9 weeks, preventing cross-contamination during watering. This allows phenotypes to be quantified that might be missed in short-term growth systems, such as subtle delays in nodule development and early nodule senescence. Also, the roots and nodules in the microcosm are easily viewed through the plate lid, so up-rooting of the plants for observation is not required.

  20. KNOTTED1-LIKE HOMEOBOX 3: a new regulator of symbiotic nodule development

    PubMed Central

    Azarakhsh, M.; Kirienko, A. N.; Zhukov, V. A.; Lebedeva, M. A.; Dolgikh, E. A.; Lutova, L. A.

    2015-01-01

    KNOX transcription factors (TFs) regulate different aspects of plant development essentially through their effects on phytohormone metabolism. In particular, KNOX TF SHOOTMERISTEMLESS activates the cytokinin biosynthesis ISOPENTENYL TRANSFERASE (IPT) genes in the shoot apical meristem. However, the role of KNOX TFs in symbiotic nodule development and their possible effects on phytohormone metabolism during nodulation have not been studied to date. Cytokinin is a well-known regulator of nodule development, playing the key role in the regulation of cell division during nodule primordium formation. Recently, the activation of IPT genes was shown to take place during nodulation. Therefore, it was hypothesized that KNOX TFs may regulate nodule development and activate cytokinin biosynthesis upon nodulation. This study analysed the expression of different KNOX genes in Medicago truncatula Gaertn. and Pisum sativum L. Among them, the KNOX3 gene was upregulated in response to rhizobial inoculation in both species. pKNOX3::GUS activity was observed in developing nodule primordium. KNOX3 ectopic expression caused the formation of nodule-like structures on transgenic root without bacterial inoculation, a phenotype similar to one described previously for legumes with constitutive activation of the cytokinin receptor. Furthermore, in transgenic roots with MtKNOX3 knockdown, downregulation of A-type cytokinin response genes was found, as well as the MtIPT3 and LONELYGUY2 (MtLOG2) gene being involved in cytokinin activation. Taken together, these findings suggest that KNOX3 gene is involved in symbiotic nodule development and may regulate cytokinin biosynthesis/activation upon nodule development in legume plants. PMID:26351356

  1. Diversity of sporadic symbionts and nonsymbiotic endophytic bacteria isolated from nodules of woody, shrub, and food legumes in Ethiopia.

    PubMed

    Aserse, Aregu Amsalu; Räsänen, Leena A; Aseffa, Fassil; Hailemariam, Asfaw; Lindström, Kristina

    2013-12-01

    Fifty-five bacterial isolates were obtained from surface-sterilized nodules of woody and shrub legumes growing in Ethiopia: Crotalaria spp., Indigofera spp., and Erythrina brucei, and the food legumes soybean and common bean. Based on partial 16S rRNA gene sequence analysis, the majority of the isolates were identified as Gram-negative bacteria belonging to the genera Achromobacter, Agrobacterium, Burkholderia, Cronobacter, Enterobacter, Mesorhizobium, Novosphingobium, Pantoea, Pseudomonas, Rahnella, Rhizobium, Serratia, and Variovorax. Seven isolates were Gram-positive bacteria belonging to the genera Bacillus, Paenibacillus, Planomicrobium, and Rhodococcus. Amplified fragment length polymorphism (AFLP) fingerprinting showed that each strain was genetically distinct. According to phylogenetic analysis of recA, glnII, rpoB, and 16S rRNA gene sequences, Rhizobium, Mesorhizobium, and Agrobacterium were further classified into six different genospecies: Agrobacterium spp., Agrobacterium radiobacter, Rhizobium sp., Rhizobium phaseoli, Mesorhizobium sp., and putative new Rhizobium species. The strains from R. phaseoli, Rhizobium sp. IAR30, and Mesorhizobium sp. ERR6 induced nodules on their host plants. The other strains did not form nodules on their original host. Nine endophytic bacterial strains representing seven genera, Agrobacterium, Burkholderia, Paenibacillus, Pantoea, Pseudomonas, Rhizobium, and Serratia, were found to colonize nodules of Crotalaria incana and common bean on co-inoculation with symbiotic rhizobia. Four endophytic Rhizobium and two Agrobacterium strains had identical nifH gene sequences with symbiotic Rhizobium strains, suggesting horizontal gene transfer. Most symbiotic and nonsymbiotic endophytic bacteria showed plant growth-promoting properties in vitro, which indicate their potential role in the promotion of plant growth when colonizing plant roots and the rhizosphere.

  2. GmEXPB2, a Cell Wall β-Expansin, Affects Soybean Nodulation through Modifying Root Architecture and Promoting Nodule Formation and Development1[OPEN

    PubMed Central

    Li, Xinxin; Zhao, Jing; Tan, Zhiyuan; Liao, Hong

    2015-01-01

    Nodulation is an essential process for biological nitrogen (N2) fixation in legumes, but its regulation remains poorly understood. Here, a β-expansin gene, GmEXPB2, was found to be critical for soybean (Glycine max) nodulation. GmEXPB2 was preferentially expressed at the early stage of nodule development. β-Glucuronidase staining further showed that GmEXPB2 was mainly localized to the nodule vascular trace and nodule vascular bundles, as well as nodule cortical and parenchyma cells, suggesting that GmEXPB2 might be involved in cell wall modification and extension during nodule formation and development. Overexpression of GmEXPB2 dramatically modified soybean root architecture, increasing the size and number of cortical cells in the root meristematic and elongation zones and expanding root hair density and size of the root hair zone. Confocal microscopy with green fluorescent protein-labeled rhizobium USDA110 cells showed that the infection events were significantly enhanced in the GmEXPB2-overexpressing lines. Moreover, nodule primordium development was earlier in overexpressing lines compared with wild-type plants. Thereby, overexpression of GmEXPB2 in either transgenic soybean hairy roots or whole plants resulted in increased nodule number, nodule mass, and nitrogenase activity and thus elevated plant N and phosphorus content as well as biomass. In contrast, suppression of GmEXPB2 in soybean transgenic composite plants led to smaller infected cells and thus reduced number of big nodules, nodule mass, and nitrogenase activity, thereby inhibiting soybean growth. Taken together, we conclude that GmEXPB2 critically affects soybean nodulation through modifying root architecture and promoting nodule formation and development and subsequently impacts biological N2 fixation and growth of soybean. PMID:26432877

  3. GmEXPB2, a Cell Wall β-Expansin, Affects Soybean Nodulation through Modifying Root Architecture and Promoting Nodule Formation and Development.

    PubMed

    Li, Xinxin; Zhao, Jing; Tan, Zhiyuan; Zeng, Rensen; Liao, Hong

    2015-12-01

    Nodulation is an essential process for biological nitrogen (N2) fixation in legumes, but its regulation remains poorly understood. Here, a β-expansin gene, GmEXPB2, was found to be critical for soybean (Glycine max) nodulation. GmEXPB2 was preferentially expressed at the early stage of nodule development. β-Glucuronidase staining further showed that GmEXPB2 was mainly localized to the nodule vascular trace and nodule vascular bundles, as well as nodule cortical and parenchyma cells, suggesting that GmEXPB2 might be involved in cell wall modification and extension during nodule formation and development. Overexpression of GmEXPB2 dramatically modified soybean root architecture, increasing the size and number of cortical cells in the root meristematic and elongation zones and expanding root hair density and size of the root hair zone. Confocal microscopy with green fluorescent protein-labeled rhizobium USDA110 cells showed that the infection events were significantly enhanced in the GmEXPB2-overexpressing lines. Moreover, nodule primordium development was earlier in overexpressing lines compared with wild-type plants. Thereby, overexpression of GmEXPB2 in either transgenic soybean hairy roots or whole plants resulted in increased nodule number, nodule mass, and nitrogenase activity and thus elevated plant N and phosphorus content as well as biomass. In contrast, suppression of GmEXPB2 in soybean transgenic composite plants led to smaller infected cells and thus reduced number of big nodules, nodule mass, and nitrogenase activity, thereby inhibiting soybean growth. Taken together, we conclude that GmEXPB2 critically affects soybean nodulation through modifying root architecture and promoting nodule formation and development and subsequently impacts biological N2 fixation and growth of soybean.

  4. Interkingdom Responses to Bacterial Quorum Sensing Signals Regulate Frequency and Rate of Nodulation in Legume-Rhizobia Symbiosis.

    PubMed

    Palmer, Andrew G; Mukherjee, Arijit; Stacy, Danielle M; Lazar, Stephen; Ané, Jean-Michel; Blackwell, Helen E

    2016-11-17

    Density-dependent phenotypic switching in bacteria, the phenomenon of quorum sensing (QS), is instrumental in many pathogenic and mutualistic behaviors. In many Gram-negative bacteria, QS is regulated by N-acylated-l-homoserine lactones (AHLs). Synthetic analogues of these AHLs hold significant promise for regulating QS at the host-symbiont interface. Regulation depends on refined temporal and spatial models of quorums under native conditions. Critical to this is an understanding of how the presence of these signals may affect a prospective host. We screened a library of AHL analogues for their ability to regulate the legume-rhizobia mutualistic symbiosis (nodulation) between Medicago truncatula and Sinorhizobium meliloti. Using an established QS-reporter line of S. meliloti and nodulation assays with wild-type bacteria, we identified compounds capable of increasing either the rate of nodule formation or total nodule number. Most importantly, we identified compounds with activity exclusive to either host or pathogen, underscoring the potential to generate QS modulators selective to bacteria with limited effects on a prospective host. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Proof that Burkholderia strains form effective symbioses with legumes: a study of novel Mimosa-nodulating strains from South America.

    PubMed

    Chen, Wen-Ming; de Faria, Sergio M; Straliotto, Rosângela; Pitard, Rosa M; Simões-Araùjo, Jean L; Chou, Jui-Hsing; Chou, Yi-Ju; Barrios, Edmundo; Prescott, Alan R; Elliott, Geoffrey N; Sprent, Janet I; Young, J Peter W; James, Euan K

    2005-11-01

    Twenty Mimosa-nodulating bacterial strains from Brazil and Venezuela, together with eight reference Mimosa-nodulating rhizobial strains and two other beta-rhizobial strains, were examined by amplified rRNA gene restriction analysis. They fell into 16 patterns and formed a single cluster together with the known beta-rhizobia, Burkholderia caribensis, Burkholderia phymatum, and Burkholderia tuberum. The 16S rRNA gene sequences of 15 of the 20 strains were determined, and all were shown to belong to the genus Burkholderia; four distinct clusters could be discerned, with strains isolated from the same host species usually clustering very closely. Five of the strains (MAP3-5, Br3407, Br3454, Br3461, and Br3469) were selected for further studies of the symbiosis-related genes nodA, the NodD-dependent regulatory consensus sequences (nod box), and nifH. The nodA and nifH sequences were very close to each other and to those of B. phymatum STM815, B. caribensis TJ182, and Cupriavidus taiwanensis LMG19424 but were relatively distant from those of B. tuberum STM678. In addition to nodulating their original hosts, all five strains could also nodulate other Mimosa spp., and all produced nodules on Mimosa pudica that had nitrogenase (acetylene reduction) activities and structures typical of effective N2-fixing symbioses. Finally, both wild-type and green fluorescent protein-expressing transconjugant strains of Br3461 and MAP3-5 produced N2-fixing nodules on their original hosts, Mimosa bimucronata (Br3461) and Mimosa pigra (MAP3-5), and hence this confirms strongly that Burkholderia strains can form effective symbioses with legumes.

  6. Proof that Burkholderia Strains Form Effective Symbioses with Legumes: a Study of Novel Mimosa-Nodulating Strains from South America

    PubMed Central

    Chen, Wen-Ming; de Faria, Sergio M.; Straliotto, Rosângela; Pitard, Rosa M.; Simões-Araùjo, Jean L.; Chou, Jui-Hsing; Chou, Yi-Ju; Barrios, Edmundo; Prescott, Alan R.; Elliott, Geoffrey N.; Sprent, Janet I.; Young, J. Peter W.; James, Euan K.

    2005-01-01

    Twenty Mimosa-nodulating bacterial strains from Brazil and Venezuela, together with eight reference Mimosa-nodulating rhizobial strains and two other β-rhizobial strains, were examined by amplified rRNA gene restriction analysis. They fell into 16 patterns and formed a single cluster together with the known β-rhizobia, Burkholderia caribensis, Burkholderia phymatum, and Burkholderia tuberum. The 16S rRNA gene sequences of 15 of the 20 strains were determined, and all were shown to belong to the genus Burkholderia; four distinct clusters could be discerned, with strains isolated from the same host species usually clustering very closely. Five of the strains (MAP3-5, Br3407, Br3454, Br3461, and Br3469) were selected for further studies of the symbiosis-related genes nodA, the NodD-dependent regulatory consensus sequences (nod box), and nifH. The nodA and nifH sequences were very close to each other and to those of B. phymatum STM815, B. caribensis TJ182, and Cupriavidus taiwanensis LMG19424 but were relatively distant from those of B. tuberum STM678. In addition to nodulating their original hosts, all five strains could also nodulate other Mimosa spp., and all produced nodules on Mimosa pudica that had nitrogenase (acetylene reduction) activities and structures typical of effective N2-fixing symbioses. Finally, both wild-type and green fluorescent protein-expressing transconjugant strains of Br3461 and MAP3-5 produced N2-fixing nodules on their original hosts, Mimosa bimucronata (Br3461) and Mimosa pigra (MAP3-5), and hence this confirms strongly that Burkholderia strains can form effective symbioses with legumes. PMID:16269788

  7. Enzymes of the Glyoxylate Cycle in Rhizobia and Nodules of Legumes 1

    PubMed Central

    Johnson, Gordon V.; Evans, Harold J.; Ching, Temay

    1966-01-01

    The relatively high level of fatty acids in soybean nodules and rhizobia from soybean nodules suggested that the glyoxylate cycle might have a role in nodule metabolism. Several species of rhizobia in pure culture were found to have malate synthetase activity when grown on a number of different carbon sources. Significant isocitrate lyase activity was induced when oleate, which presumably may act as an acetyl CoA precursor, was utilized as the principle carbon source. Malate synthetase was active in extracts of rhizobia from nodules of bush bean (Phaseolus vulgaris L.), cowpea (Vigna sinensis L.), lupine (Lupinus angustifolius L.) and soybean (Glycine max L. Merr.). Activity of malate synthetase was, however, barely detectable in rhizobia from alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) and pea (Pisum sativum L.) nodules. Appreciable isocitrate lyase activity was not detected in rhizobia from nodules nor was it induced by depletion of endogenous substrates by incubation of excised bush bean nodules. Although rhizobia has the potential for the formation of the key enzymes of the glyoxylate cycle, the absence of isocitrate lyase activity in bacteria isolated from nodules indicated that the glyoxylate cycle does not operate in the symbiotic growth of rhizobia and that the observed high content of fatty acids in nodules and nodule bacteria probably is related to a structural role. PMID:16656404

  8. RRNA and dnaK relationships of Bradyrhizobium sp. nodule bacteria from four papilionoid legume trees in Costa Rica.

    PubMed

    Parker, Matthew A

    2004-05-01

    Enzyme electrophoresis and sequencing of rRNA and dnaK genes revealed high genetic diversity among root nodule bacteria from the Costa Rican trees Andira inermis, Dalbergia retusa, Platymiscium pinnatum (Papilionoideae tribe Dalbergieae) and Lonchocarpus atropurpureus (Papilionoideae tribe Millettieae). A total of 21 distinct multilocus genotypes [ETs (electrophoretic types)] was found among the 36 isolates analyzed, and no ETs were shared in common by isolates from different legume hosts. However, three of the ETs from D. retusa were identical to Bradyrhizobium sp. isolates detected in prior studies of several other legume genera in both Costa Rica and Panama. Nearly full-length 16S rRNA sequences and partial 23S rRNA sequences confirmed that two isolates from D. retusa were highly similar or identical to Bradyrhizobium strains isolated from the legumes Erythrina and Clitoria (Papilionoideae tribe Phaseoleae) in Panama. rRNA sequences for five isolates from L. atropurpureus, P. pinnatum and A. inermis were not closely related to any currently known strains from Central America or elsewhere, but had affinities to the reference strains Bradyrhizobium japonicum USDA 110 (three isolates) or to B. elkanii USDA 76 (two isolates). A phylogenetic tree for 21 Bradyrhizobium strains based on 603 bp of the dnaK gene showed several significant conflicts with the rRNA tree, suggesting that genealogical relationships may have been altered by lateral gene transfer events.

  9. Vigna unguiculata is nodulated in Spain by endosymbionts of Genisteae legumes and by a new symbiovar (vignae) of the genus Bradyrhizobium.

    PubMed

    Bejarano, Ana; Ramírez-Bahena, Martha-Helena; Velázquez, Encarna; Peix, Alvaro

    2014-10-01

    Vigna unguiculata was introduced into Europe from its distribution centre in Africa, and it is currently being cultivated in Mediterranean regions with adequate edapho-climatic conditions where the slow growing rhizobia nodulating this legume have not yet been studied. Previous studies based on rrs gene and ITS region analyses have shown that Bradyrhizobium yuanmingense and B. elkanii nodulated V. unguiculata in Africa, but these two species were not found in this study. Using the same phylogenetic markers it was shown that V. unguiculata, a legume from the tribe Phaseolae, was nodulated in Spain by two species of group I, B. cytisi and B. canariense, which are common endosymbionts of Genisteae in both Europe and Africa. These species have not been found to date in V. unguiculata nodules in its African distribution centres. All strains from Bradyrhizobium group I isolated in Spain belonged to the symbiovar genistearum, which is found at present only in Genisteae legumes in both Africa and Europe. V. unguiculata was also nodulated in Spain by a strain from Bradyrhizobium group II that belonged to a novel symbiovar (vignae). Some African V. unguiculata-nodulating strains also belonged to this proposed new symbiovar.

  10. Short-Term Molecular Acclimation Processes of Legume Nodules to Increased External Oxygen Concentration

    PubMed Central

    Avenhaus, Ulrike; Cabeza, Ricardo A.; Liese, Rebecca; Lingner, Annika; Dittert, Klaus; Salinas-Riester, Gabriela; Pommerenke, Claudia; Schulze, Joachim

    2016-01-01

    Nitrogenase is an oxygen labile enzyme. Microaerobic conditions within the infected zone of nodules are maintained primarily by an oxygen diffusion barrier (ODB) located in the nodule cortex. Flexibility of the ODB is important for the acclimation processes of nodules in response to changes in external oxygen concentration. The hypothesis of the present study was that there are additional molecular mechanisms involved. Nodule activity of Medicago truncatula plants were continuously monitored during a change from 21 to 25 or 30% oxygen around root nodules by measuring nodule H2 evolution. Within about 2 min of the increase in oxygen concentration, a steep decline in nitrogenase activity occurred. A quick recovery commenced about 8 min later. A qPCR-based analysis of the expression of genes for nitrogenase components showed a tendency toward upregulation during the recovery. The recovery resulted in a new constant activity after about 30 min, corresponding to approximately 90% of the pre-treatment level. An RNAseq-based comparative transcriptome profiling of nodules at that point in time revealed that genes for nodule-specific cysteine-rich (NCR) peptides, defensins, leghaemoglobin and chalcone and stilbene synthase were significantly upregulated when considered as a gene family. A gene for a nicotianamine synthase-like protein (Medtr1g084050) showed a strong increase in count number. The gene appears to be of importance for nodule functioning, as evidenced by its consistently high expression in nodules and a strong reaction to various environmental cues that influence nodule activity. A Tnt1-mutant that carries an insert in the coding sequence (cds) of that gene showed reduced nitrogen fixation and less efficient acclimation to an increased external oxygen concentration. It was concluded that sudden increases in oxygen concentration around nodules destroy nitrogenase, which is quickly counteracted by an increased neoformation of the enzyme. This reaction might be

  11. Short-Term Molecular Acclimation Processes of Legume Nodules to Increased External Oxygen Concentration.

    PubMed

    Avenhaus, Ulrike; Cabeza, Ricardo A; Liese, Rebecca; Lingner, Annika; Dittert, Klaus; Salinas-Riester, Gabriela; Pommerenke, Claudia; Schulze, Joachim

    2015-01-01

    Nitrogenase is an oxygen labile enzyme. Microaerobic conditions within the infected zone of nodules are maintained primarily by an oxygen diffusion barrier (ODB) located in the nodule cortex. Flexibility of the ODB is important for the acclimation processes of nodules in response to changes in external oxygen concentration. The hypothesis of the present study was that there are additional molecular mechanisms involved. Nodule activity of Medicago truncatula plants were continuously monitored during a change from 21 to 25 or 30% oxygen around root nodules by measuring nodule H2 evolution. Within about 2 min of the increase in oxygen concentration, a steep decline in nitrogenase activity occurred. A quick recovery commenced about 8 min later. A qPCR-based analysis of the expression of genes for nitrogenase components showed a tendency toward upregulation during the recovery. The recovery resulted in a new constant activity after about 30 min, corresponding to approximately 90% of the pre-treatment level. An RNAseq-based comparative transcriptome profiling of nodules at that point in time revealed that genes for nodule-specific cysteine-rich (NCR) peptides, defensins, leghaemoglobin and chalcone and stilbene synthase were significantly upregulated when considered as a gene family. A gene for a nicotianamine synthase-like protein (Medtr1g084050) showed a strong increase in count number. The gene appears to be of importance for nodule functioning, as evidenced by its consistently high expression in nodules and a strong reaction to various environmental cues that influence nodule activity. A Tnt1-mutant that carries an insert in the coding sequence (cds) of that gene showed reduced nitrogen fixation and less efficient acclimation to an increased external oxygen concentration. It was concluded that sudden increases in oxygen concentration around nodules destroy nitrogenase, which is quickly counteracted by an increased neoformation of the enzyme. This reaction might be

  12. Determination of the hydrogenase status of individual legume nodules by a methylene blue reduction assay.

    PubMed

    Lambert, G R; Hanus, F J; Russell, S A; Evans, H J

    1985-08-01

    We adapted a method for the rapid screening of colonies of free-living Rhizobium japonicum for hydrogenase activity to determine the hydrogenase status of individual soybean nodules. Crude bacteroid suspensions from nodules containing strains known to be hydrogen uptake positive (Hup) caused a localized decolorization of filter paper disks, whereas suspensions from nodules arising from inoculation with hydrogen uptake-negative (Hup) mutants or strains did not decolorize the disks. The reliability of the method was demonstrated by its successful application to 29 slow-growing rhizobia. The Hup phenotype on methylene blue filters agreed with that determined amperometrically with either methylene blue or oxygen as the electron acceptor.

  13. A Phylogenetically Conserved Group of Nuclear Factor-Y Transcription Factors Interact to Control Nodulation in Legumes1[OPEN

    PubMed Central

    Laloum, Tom; Lepage, Agnès; Ariel, Federico; Frances, Lisa; Gamas, Pascal; de Carvalho-Niebel, Fernanda

    2015-01-01

    The endosymbiotic association between legumes and soil bacteria called rhizobia leads to the formation of a new root-derived organ called the nodule in which differentiated bacteria convert atmospheric nitrogen into a form that can be assimilated by the host plant. Successful root infection by rhizobia and nodule organogenesis require the activation of symbiotic genes that are controlled by a set of transcription factors (TFs). We recently identified Medicago truncatula nuclear factor-YA1 (MtNF-YA1) and MtNF-YA2 as two M. truncatula TFs playing a central role during key steps of the Sinorhizobium meliloti-M. truncatula symbiotic interaction. NF-YA TFs interact with NF-YB and NF-YC subunits to regulate target genes containing the CCAAT box consensus sequence. In this study, using a yeast two-hybrid screen approach, we identified the NF-YB and NF-YC subunits able to interact with MtNF-YA1 and MtNF-YA2. In yeast (Saccharomyces cerevisiae) and in planta, we further demonstrated by both coimmunoprecipitation and bimolecular fluorescence complementation that these NF-YA, -B, and -C subunits interact and form a stable NF-Y heterotrimeric complex. Reverse genetic and chromatin immunoprecipitation-PCR approaches revealed the importance of these newly identified NF-YB and NF-YC subunits for rhizobial symbiosis and binding to the promoter of MtERN1 (for Ethylene Responsive factor required for Nodulation), a direct target gene of MtNF-YA1 and MtNF-YA2. Finally, we verified that a similar trimer is formed in planta by the common bean (Phaseolus vulgaris) NF-Y subunits, revealing the existence of evolutionary conserved NF-Y protein complexes to control nodulation in leguminous plants. This sheds light on the process whereby an ancient heterotrimeric TF mainly controlling cell division in animals has acquired specialized functions in plants. PMID:26432878

  14. A Phylogenetically Conserved Group of Nuclear Factor-Y Transcription Factors Interact to Control Nodulation in Legumes.

    PubMed

    Baudin, Maël; Laloum, Tom; Lepage, Agnès; Rípodas, Carolina; Ariel, Federico; Frances, Lisa; Crespi, Martin; Gamas, Pascal; Blanco, Flavio Antonio; Zanetti, Maria Eugenia; de Carvalho-Niebel, Fernanda; Niebel, Andreas

    2015-12-01

    The endosymbiotic association between legumes and soil bacteria called rhizobia leads to the formation of a new root-derived organ called the nodule in which differentiated bacteria convert atmospheric nitrogen into a form that can be assimilated by the host plant. Successful root infection by rhizobia and nodule organogenesis require the activation of symbiotic genes that are controlled by a set of transcription factors (TFs). We recently identified Medicago truncatula nuclear factor-YA1 (MtNF-YA1) and MtNF-YA2 as two M. truncatula TFs playing a central role during key steps of the Sinorhizobium meliloti-M. truncatula symbiotic interaction. NF-YA TFs interact with NF-YB and NF-YC subunits to regulate target genes containing the CCAAT box consensus sequence. In this study, using a yeast two-hybrid screen approach, we identified the NF-YB and NF-YC subunits able to interact with MtNF-YA1 and MtNF-YA2. In yeast (Saccharomyces cerevisiae) and in planta, we further demonstrated by both coimmunoprecipitation and bimolecular fluorescence complementation that these NF-YA, -B, and -C subunits interact and form a stable NF-Y heterotrimeric complex. Reverse genetic and chromatin immunoprecipitation-PCR approaches revealed the importance of these newly identified NF-YB and NF-YC subunits for rhizobial symbiosis and binding to the promoter of MtERN1 (for Ethylene Responsive factor required for Nodulation), a direct target gene of MtNF-YA1 and MtNF-YA2. Finally, we verified that a similar trimer is formed in planta by the common bean (Phaseolus vulgaris) NF-Y subunits, revealing the existence of evolutionary conserved NF-Y protein complexes to control nodulation in leguminous plants. This sheds light on the process whereby an ancient heterotrimeric TF mainly controlling cell division in animals has acquired specialized functions in plants.

  15. NrcR, a New Transcriptional Regulator of Rhizobium tropici CIAT 899 Involved in the Legume Root-Nodule Symbiosis

    PubMed Central

    del Cerro, Pablo; Rolla-Santos, Amanda A. P.; Valderrama-Fernández, Rocío; Gil-Serrano, Antonio; Bellogín, Ramón A.; Gomes, Douglas Fabiano; Pérez-Montaño, Francisco; Megías, Manuel; Hungría, Mariangela; Ollero, Francisco Javier

    2016-01-01

    The establishment of nitrogen-fixing rhizobium-legume symbioses requires a highly complex cascade of events. In this molecular dialogue the bacterial NodD transcriptional regulators in conjunction with plant inducers, mostly flavonoids, are responsible for the biosynthesis and secretion of Nod factors which are key molecules for successful nodulation. Other transcriptional regulators related to the symbiotic process have been identified in rhizobial genomes, including negative regulators such as NolR. Rhizobium tropici CIAT 899 is an important symbiont of common bean (Phaseolus vulgaris L.), and its genome encompasses intriguing features such as five copies of nodD genes, as well as other possible transcriptional regulators including the NolR protein. Here we describe and characterize a new regulatory gene located in the non-symbiotic plasmid pRtrCIAT899c, that shows homology (46% identity) with the nolR gene located in the chromosome of CIAT 899. The mutation of this gene, named nrcR (nolR-like plasmid c Regulator), enhanced motility and exopolysaccharide production in comparison to the wild-type strain. Interestingly, the number and decoration of Nod Factors produced by this mutant were higher than those detected in the wild-type strain, especially under salinity stress. The nrcR mutant showed delayed nodulation and reduced competitiveness with P. vulgaris, and reduction in nodule number and shoot dry weight in both P. vulgaris and Leucaena leucocephala. Moreover, the mutant exhibited reduced capacity to induce the nodC gene in comparison to the wild-type CIAT 899. The finding of a new nod-gene regulator located in a non-symbiotic plasmid may reveal the existence of even more complex mechanisms of regulation of nodulation genes in R. tropici CIAT 899 that may be applicable to other rhizobial species. PMID:27096734

  16. Nitrogen-fixing nodules from rose wood legume trees (Dalbergia spp.) endemic to Madagascar host seven different genera belonging to alpha- and beta-Proteobacteria.

    PubMed

    Rasolomampianina, R; Bailly, X; Fetiarison, R; Rabevohitra, R; Béna, G; Ramaroson, L; Raherimandimby, M; Moulin, L; De Lajudie, P; Dreyfus, B; Avarre, J-C

    2005-11-01

    Although legume biodiversity is concentrated in tropical regions, the majority of studies on legume nodulating bacteria (LNB) are focused on cultivated leguminous plants from temperate regions. However, recent works on tropical regions tend to indicate that the actual diversity of LNB is largely underestimated. In this study, we report the isolation and characterization of 68 nitrogen-fixing root nodule bacteria collected from eight endemic tree species of Dalbergia in Madagascar. The isolates were characterized by (i) restriction fragment length polymorphism (RFLP) analysis of 16S-IGS rDNA, (ii) 16S rDNA gene sequencing and (iii) nodulation tests. Results revealed a wide diversity of bacteria present in the nodules of Dalbergia. Among the 68 isolated bacteria, 65 belonged to Bradyrhizobium, Mesorhizobium, Rhizobium, Azorhizobium and Phyllobacterium from the alpha-class of Proteobacteria, and three isolates belonged to Burkholderia and Ralstonia from the beta-class of Proteobacteria. Our results also show for the first time that a strain belonging to the Burkholderia cepacia complex is able to induce efficient nodules on a legume plant.

  17. Nitrate inhibition of legume nodule growth and activity. II. Short term studies with high nitrate supply

    SciTech Connect

    Streeter, J.G.

    1985-02-01

    Soybean plants (Glycine max (L.) Merr) were grown in sand culture with 2 millimolar nitrate for 37 days and then supplied with 15 millimolar nitrate for 7 days. Control plants received 2 millimolar nitrate and 13 millimolar chloride and, after the 7-day treatment period, all plants were supplied with nil nitrate. The temporary treatment with high nitrate inhibited nitrogenase (acetylene reduction) activity by 80% whether or not Rhizobium japonicum bacteroids had nitrate reductase (NR) activity. The pattern of nitrite accumulation in nodules formed by NR/sup +/ rhizobia was inversely related to the decrease and recovery of nitrogenase activity. However, nitrite concentration in nodules formed by NR/sup -/ rhizobia appeared to be too low to explain the inhibition of nitrogenase. Nodules on plants treated with 15 millimolar nitrate contained higher concentrations of amino N and, especially, ureide N than control nodules and, after withdrawal of nitrate, reduced N content of treated and control nodules returned to similar levels. The accumulation of N/sub 2/ fixation products in nodules in response to high nitrate treatment was observed with three R. japonicum strains, two NR/sup +/ and one NR/sup -/.

  18. Polyploids did not Predate the Evolution of Nodulation in all Legumes

    USDA-ARS?s Scientific Manuscript database

    Several lines of evidence indicate that polyploidy occurred by around 54 million years ago, early in the history of legume evolution, but it has not been known whether this event was confined to the papilionoid subfamily (Papilionoideae; e.g., beans, medics, lupins) or occurred earlier. Determining...

  19. Knockdown of LjIPT3 influences nodule development in Lotus japonicus.

    PubMed

    Chen, Yaping; Chen, Wei; Li, Xueliu; Jiang, Huawu; Wu, Pingzhi; Xia, Kuaifei; Yang, Yali; Wu, Guojiang

    2014-01-01

    Cytokinins play important roles in legume-rhizobia symbiosis. Here we report isolation of six genes encoding isopentenyl transferase (IPT) from Lotus japonicus, which catalyze the rate-limiting step of cytokinin biosynthesis. The LjIPT3 gene was found to be up-regulated in infected roots and mature nodules. Histochemical analysis demonstrated expression of Pro(LjIPT3):GUS (β-glucuronidase) in vegetative and reproductive organs, and was especially high in the vascular bundles of roots. When inoculated with Mesorhizobium loti MAFF303099, LjIPT3 was undetectable in the nodule primordia and developing nodules, and later it was expressed only in the vascular bundles of mature nodules. In addition, knockdown of LjIPT3 (LjIPT3i) by RNA interference reduced levels of endogenous cytokinins, affected plant development and accelerated Chl degradation during dark-induced leaf senescence. Compared with the wild type, LjIPT3i plants produced fewer infection threads and nodules. In addition, expression of downstream nodulation-related transcription factor genes LjNSP1, LjNSP2 and LjNIN decreased dramatically in LjIPT3i plants. These results suggest that LjIPT3 regulates the CRE1-dependent cytokinin pathway, affecting nodule initiation and thereby influencing the number of infection threads and nodules. Detection of nitrogenase activity and observation of nodule structure showed that endogenous cytokinins are required for full development of the infected cells in mature nodules by preventing early senescence. Therefore, our results indicate that the LjIPT3 gene product is required for nodule initiation and development, and does not appear to be involved in early infection events.

  20. microRNA160 dictates stage-specific auxin and cytokinin sensitivities and directs soybean nodule development.

    PubMed

    Nizampatnam, Narasimha Rao; Schreier, Spencer John; Damodaran, Suresh; Adhikari, Sajag; Subramanian, Senthil

    2015-10-01

    Legume nodules result from coordinated interactions between the plant and nitrogen-fixing rhizobia. The phytohormone cytokinin promotes nodule formation, and recent findings suggest that the phytohormone auxin inhibits nodule formation. Here we show that microRNA160 (miR160) is a key signaling element that determines the auxin/cytokinin balance during nodule development in soybean (Glycine max). miR160 appears to promote auxin activity by suppressing the levels of the ARF10/16/17 family of repressor ARF transcription factors. Using quantitative PCR assays and a fluorescence miRNA sensor, we show that miR160 levels are relatively low early during nodule formation and high in mature nodules. We had previously shown that ectopic expression of miR160 in soybean roots led to a severe reduction in nodule formation, coupled with enhanced sensitivity to auxin and reduced sensitivity to cytokinin. Here we show that exogenous cytokinin restores nodule formation in miR160 over-expressing roots. Therefore, low miR160 levels early during nodule development favor cytokinin activity required for nodule formation. Suppression of miR160 levels using a short tandem target mimic (STTM160) resulted in reduced sensitivity to auxin and enhanced sensitivity to cytokinin. In contrast to miR160 over-expressing roots, STTM160 roots had increased nodule formation, but nodule maturation was significantly delayed. Exogenous auxin partially restored proper nodule formation and maturation in STTM160 roots, suggesting that high miR160 activity later during nodule development favors auxin activity and promotes nodule maturation. Therefore, miR160 dictates developmental stage-specific sensitivities to auxin and cytokinin to direct proper nodule formation and maturation in soybean.

  1. Localization of superoxide dismutases and hydrogen peroxide in legume root nodules.

    PubMed

    Rubio, Maria C; James, Euan K; Clemente, Maria R; Bucciarelli, Bruna; Fedorova, Maria; Vance, Carroll P; Becana, Manuel

    2004-12-01

    Superoxide dismutases (SODs) catalyze the dismutation of superoxide radicals to O2 and H2O2 and thus represent a primary line of antioxidant defense in all aerobic organisms. H2O2 is a signal molecule involved in the plant's response to pathogen attack and other stress conditions as well as in nodulation. In this work, we have tested the hypothesis that SODs are a source of H2O2 in indeterminate alfalfa (Medicago sativa) and pea (Pisum sativum) nodules. The transcripts and proteins of the major SODs of nodules were localized by in situ RNA hybridization and immunogold electron microscopy, respectively, whereas H2O2 was localized cytochemically by electron microscopy of cerium-perfused nodule tissue. The transcript and protein of cytosolic CuZnSOD are most abundant in the meristem (I) and invasion (II) zones, interzone II-III, and distal part of the N2-fixing zone (III), and those of MnSOD in zone III, especially in the infected cells. At the subcellular level, CuZnSOD was found in the infection threads, cytosol adjacent to cell walls, and apoplast, whereas MnSOD was in the bacteroids, bacteria within infection threads, and mitochondria. The distinct expression pattern of CuZnSOD and MnSOD suggests specific roles of the enzymes in nodules. Large amounts of H2O2 were found at the same three nodule sites as CuZnSOD but not in association with MnSOD. This colocalization led us to postulate that cytosolic CuZnSOD is a source of H2O2 in nodules. Furthermore, the absence or large reduction of H2O2 in nodule tissue preincubated with enzyme inhibitors (cyanide, azide, diphenyleneiodonium, diethyldithiocarbamate) provides strong support to the hypothesis that at least some of the H2O2 originates by the sequential operation of an NADPH oxidase-like enzyme and CuZnSOD. Results also show that there is abundant H2O2 associated with degrading bacteroids in the senescent zone (IV), which reflects the oxidative stress ensued during nodule senescence.

  2. Stress-induced legume root nodule senescence. Physiological, biochemical, and structural alterations.

    PubMed

    Matamoros, M A; Baird, L M; Escuredo, P R; Dalton, D A; Minchin, F R; Iturbe-Ormaetxe, I; Rubio, M C; Moran, J F; Gordon, A J; Becana, M

    1999-09-01

    Nitrate-fed and dark-stressed bean (Phaseolus vulgaris) and pea (Pisum sativum) plants were used to study nodule senescence. In bean, 1 d of nitrate treatment caused a partially reversible decline in nitrogenase activity and an increase in O(2) diffusion resistance, but minimal changes in carbon metabolites, antioxidants, and other biochemical parameters, indicating that the initial decrease in nitrogenase activity was due to O(2) limitation. In pea, 1 d of dark treatment led to a 96% decline in nitrogenase activity and sucrose, indicating sugar deprivation as the primary cause of activity loss. In later stages of senescence (4 d of nitrate or 2-4 d of dark treatment), nodules showed accumulation of oxidized proteins and general ultrastructural deterioration. The major thiol tripeptides of untreated nodules were homoglutathione (72%) in bean and glutathione (89%) in pea. These predominant thiols declined by approximately 93% after 4 d of nitrate or dark treatment, but the loss of thiol content can be only ascribed in part to limited synthesis by gamma-glutamylcysteinyl, homoglutathione, and glutathione synthetases. Ascorbate peroxidase was immunolocalized primarily in the infected and parenchyma (inner cortex) nodule cells, with large decreases in senescent tissue. Ferritin was almost undetectable in untreated bean nodules, but accumulated in the plastids and amyloplasts of uninfected interstitial and parenchyma cells following 2 or 4 d of nitrate treatment, probably as a response to oxidative stress.

  3. Stress-Induced Legume Root Nodule Senescence. Physiological, Biochemical, and Structural Alterations1

    PubMed Central

    Matamoros, Manuel A.; Baird, Lisa M.; Escuredo, Pedro R.; Dalton, David A.; Minchin, Frank R.; Iturbe-Ormaetxe, Iñaki; Rubio, Maria C.; Moran, Jose F.; Gordon, Anthony J.; Becana, Manuel

    1999-01-01

    Nitrate-fed and dark-stressed bean (Phaseolus vulgaris) and pea (Pisum sativum) plants were used to study nodule senescence. In bean, 1 d of nitrate treatment caused a partially reversible decline in nitrogenase activity and an increase in O2 diffusion resistance, but minimal changes in carbon metabolites, antioxidants, and other biochemical parameters, indicating that the initial decrease in nitrogenase activity was due to O2 limitation. In pea, 1 d of dark treatment led to a 96% decline in nitrogenase activity and sucrose, indicating sugar deprivation as the primary cause of activity loss. In later stages of senescence (4 d of nitrate or 2–4 d of dark treatment), nodules showed accumulation of oxidized proteins and general ultrastructural deterioration. The major thiol tripeptides of untreated nodules were homoglutathione (72%) in bean and glutathione (89%) in pea. These predominant thiols declined by approximately 93% after 4 d of nitrate or dark treatment, but the loss of thiol content can be only ascribed in part to limited synthesis by γ-glutamylcysteinyl, homoglutathione, and glutathione synthetases. Ascorbate peroxidase was immunolocalized primarily in the infected and parenchyma (inner cortex) nodule cells, with large decreases in senescent tissue. Ferritin was almost undetectable in untreated bean nodules, but accumulated in the plastids and amyloplasts of uninfected interstitial and parenchyma cells following 2 or 4 d of nitrate treatment, probably as a response to oxidative stress. PMID:10482665

  4. Partial Purification of a Legume Nodulation Factor Present in Coconut Water 1

    PubMed Central

    Schaffer, A. G.; Alexander, M.

    1967-01-01

    The nodulation of adventitious roots growing from segments of bean hypocotyl tissue was used as a bioassay for the material present in coconut water which stimulated nodulation. The active material in coconut water is acidic, but it was not possible to extract it from an acid solution with organic solvents. A purification of approximately 70-fold (on a dry wt basis) was obtained using activated charcoal, but at least 10 different compounds were present in the active fractions. A purified fraction of coconut water, which is stimulatory to the growth of carrot root explants, was active in the nodulation assay at a concentration of 2 μg/ml. This represents a 4000-fold purification of the diffusible fraction of coconut water. The charcoal fractionation procedure can be applied to the active material present in extracts of bean leaves. PMID:16656538

  5. The presence of nodules on legume root systems can alter phenotypic plasticity in response to internal nitrogen independent of nitrogen fixation.

    PubMed

    Goh, Chooi-Hua; Nicotra, Adrienne B; Mathesius, Ulrike

    2016-04-01

    All higher plants show developmental plasticity in response to the availability of nitrogen (N) in the soil. In legumes, N starvation causes the formation of root nodules, where symbiotic rhizobacteria fix atmospheric N2 for the host in exchange for fixed carbon (C) from the shoot. Here, we tested whether plastic responses to internal [N] of legumes are altered by their symbionts. Glasshouse experiments compared root phenotypes of three legumes, Medicago truncatula, Medicago sativa and Trifolium subterraneum, inoculated with their compatible symbiont partners and grown under four nitrate levels. In addition, six strains of rhizobia, differing in their ability to fix N2 in M. truncatula, were compared to test if plastic responses to internal [N] were dependent on the rhizobia or N2 -fixing capability of the nodules. We found that the presence of rhizobia affected phenotypic plasticity of the legumes to internal [N], particularly in root length and root mass ratio (RMR), in a plant species-dependent way. While root length responses of M. truncatula to internal [N] were dependent on the ability of rhizobial symbionts to fix N2 , RMR response to internal [N] was dependent only on initiation of nodules, irrespective of N2 -fixing ability of the rhizobia strains.

  6. Transport and partitioning of CO/sub 2/ fixed by root nodules of ureide and amide producing legumes. [Vigna angularis; Glycine max; Medicago sativa

    SciTech Connect

    Vance, C.P.; Boylan, K.L.M.; Maxwell, C.A.; Heichel, G.H.; Hardman, L.L.

    1985-01-01

    Nodulated and denodulated roots of adzuki bean (Vigna angularis), soybean (Glycine max), and alfalfa (Medicago sativa) were exposed to /sup 14/CO/sub 2/ to investigate the contribution of nodule CO/sub 2/ fixation to assimilation and transport of fixed nitrogen. The distribution of radioactivity in xylem sap and partitioning of carbon fixed by nodules to the whole plant were measured. Radioactivity in the xylem sap of nodulated soybean and adzuki bean was located primarily (70 to 87%) in the acid fraction while the basic (amino acid) fraction contained 10 to 22%. In contrast radioactivity in the xylem sap of nodulated alfalfa was primarily in amino acids with about 20% in organic acids. Total ureide concentration was 8.1, 4.7, and 0.0 micromoles per milliliter xylem sap for soybean, adzuki bean, and alfalfa, respectively. While the major nitrogen transport products in soybeans and adzuki beans are ureides, this class of metabolites contained less than 20% of the the total radioactivity. When nodules of plants were removed, radioactivity in xylem sap decreased by 90% or more. Pulse-chase experiments indicated that CO/sub 2/ fixed by nodules was rapidly transported to shoots and incorporated into acid stable constituents. The data are consistent with a role for nodule CO/sub 2/ fixation providing carbon for the assimilation and transport of fixed nitrogen in amide-based legumes. In contrast, CO/sub 2/ fixation by nodules of ureide transporting legumes appears to contribute little to assimilation and transport of fixed nitrogen. 19 references, 2 figures, 5 tables.

  7. Convergent Evolution of Endosymbiont Differentiation in Dalbergioid and Inverted Repeat-Lacking Clade Legumes Mediated by Nodule-Specific Cysteine-Rich Peptides.

    PubMed

    Czernic, Pierre; Gully, Djamel; Cartieaux, Fabienne; Moulin, Lionel; Guefrachi, Ibtissem; Patrel, Delphine; Pierre, Olivier; Fardoux, Joël; Chaintreuil, Clémence; Nguyen, Phuong; Gressent, Frédéric; Da Silva, Corinne; Poulain, Julie; Wincker, Patrick; Rofidal, Valérie; Hem, Sonia; Barrière, Quentin; Arrighi, Jean-François; Mergaert, Peter; Giraud, Eric

    2015-10-01

    Nutritional symbiotic interactions require the housing of large numbers of microbial symbionts, which produce essential compounds for the growth of the host. In the legume-rhizobium nitrogen-fixing symbiosis, thousands of rhizobium microsymbionts, called bacteroids, are confined intracellularly within highly specialized symbiotic host cells. In Inverted Repeat-Lacking Clade (IRLC) legumes such as Medicago spp., the bacteroids are kept under control by an arsenal of nodule-specific cysteine-rich (NCR) peptides, which induce the bacteria in an irreversible, strongly elongated, and polyploid state. Here, we show that in Aeschynomene spp. legumes belonging to the more ancient Dalbergioid lineage, bacteroids are elongated or spherical depending on the Aeschynomene spp. and that these bacteroids are terminally differentiated and polyploid, similar to bacteroids in IRLC legumes. Transcriptome, in situ hybridization, and proteome analyses demonstrated that the symbiotic cells in the Aeschynomene spp. nodules produce a large diversity of NCR-like peptides, which are transported to the bacteroids. Blocking NCR transport by RNA interference-mediated inactivation of the secretory pathway inhibits bacteroid differentiation. Together, our results support the view that bacteroid differentiation in the Dalbergioid clade, which likely evolved independently from the bacteroid differentiation in the IRLC clade, is based on very similar mechanisms used by IRLC legumes.

  8. Convergent Evolution of Endosymbiont Differentiation in Dalbergioid and Inverted Repeat-Lacking Clade Legumes Mediated by Nodule-Specific Cysteine-Rich Peptides1

    PubMed Central

    Czernic, Pierre; Gully, Djamel; Cartieaux, Fabienne; Moulin, Lionel; Guefrachi, Ibtissem; Patrel, Delphine; Pierre, Olivier; Fardoux, Joël; Chaintreuil, Clémence; Nguyen, Phuong; Gressent, Frédéric; Da Silva, Corinne; Poulain, Julie; Wincker, Patrick; Rofidal, Valérie; Hem, Sonia; Barrière, Quentin; Arrighi, Jean-François; Mergaert, Peter; Giraud, Eric

    2015-01-01

    Nutritional symbiotic interactions require the housing of large numbers of microbial symbionts, which produce essential compounds for the growth of the host. In the legume-rhizobium nitrogen-fixing symbiosis, thousands of rhizobium microsymbionts, called bacteroids, are confined intracellularly within highly specialized symbiotic host cells. In Inverted Repeat-Lacking Clade (IRLC) legumes such as Medicago spp., the bacteroids are kept under control by an arsenal of nodule-specific cysteine-rich (NCR) peptides, which induce the bacteria in an irreversible, strongly elongated, and polyploid state. Here, we show that in Aeschynomene spp. legumes belonging to the more ancient Dalbergioid lineage, bacteroids are elongated or spherical depending on the Aeschynomene spp. and that these bacteroids are terminally differentiated and polyploid, similar to bacteroids in IRLC legumes. Transcriptome, in situ hybridization, and proteome analyses demonstrated that the symbiotic cells in the Aeschynomene spp. nodules produce a large diversity of NCR-like peptides, which are transported to the bacteroids. Blocking NCR transport by RNA interference-mediated inactivation of the secretory pathway inhibits bacteroid differentiation. Together, our results support the view that bacteroid differentiation in the Dalbergioid clade, which likely evolved independently from the bacteroid differentiation in the IRLC clade, is based on very similar mechanisms used by IRLC legumes. PMID:26286718

  9. Cicer canariense, an endemic legume to the Canary Islands, is nodulated in mainland Spain by fast-growing strains from symbiovar trifolii phylogenetically related to Rhizobium leguminosarum.

    PubMed

    Martínez-Hidalgo, Pilar; Flores-Félix, José-David; Menéndez, Esther; Rivas, Raúl; Carro, Lorena; Mateos, Pedro F; Martínez-Molina, Eustoquio; León-Barrios, Milagros; Velázquez, Encarna

    2015-07-01

    Cicer canariense is a threatened endemic legume from the Canary Islands where it can be nodulated by mesorhizobial strains from the symbiovar ciceri, which is the common worldwide endosymbiont of Cicer arietinum linked to the genus Mesorhizobium. However, when C. canariense was cultivated in a soil from mainland Spain, where the symbiovar ciceri is present, only fast-growing rhizobial strains were unexpectedly isolated from its nodules. These strains were classified into the genus Rhizobium by analysis of the recA and atpD genes, and they were phylogenetically related to Rhizobium leguminosarum. The analysis of the nodC gene showed that the isolated strains belonged to the symbiovar trifolii that harbored a nodC allele (β allele) different to that harbored by other strains from this symbiovar. Nodulation experiments carried out with the lacZ-labeled strain RCCHU01, representative of the β nodC allele, showed that it induced curling of root hairs, infected them through infection threads, and formed typical indeterminate nodules where nitrogen fixation took place. This represents a case of exceptional performance between the symbiovar trifolii and a legume from the tribe Cicereae that opens up new possibilities and provides new insights into the study of rhizobia-legume symbiosis. Copyright © 2015 Elsevier GmbH. All rights reserved.

  10. Role of cysteine residues and disulfide bonds in the activity of a legume root nodule-specific, cysteine-rich peptide.

    PubMed

    Haag, Andreas F; Kerscher, Bernhard; Dall'Angelo, Sergio; Sani, Monica; Longhi, Renato; Baloban, Mikhail; Wilson, Heather M; Mergaert, Peter; Zanda, Matteo; Ferguson, Gail P

    2012-03-30

    The root nodules of certain legumes including Medicago truncatula produce >300 different nodule-specific cysteine-rich (NCR) peptides. Medicago NCR antimicrobial peptides (AMPs) mediate the differentiation of the bacterium, Sinorhizobium meliloti into a nitrogen-fixing bacteroid within the legume root nodules. In vitro, NCR AMPs such as NCR247 induced bacteroid features and exhibited antimicrobial activity against S. meliloti. The bacterial BacA protein is critical to prevent S. meliloti from being hypersensitive toward NCR AMPs. NCR AMPs are cationic and have conserved cysteine residues, which form disulfide (S-S) bridges. However, the natural configuration of NCR AMP S-S bridges and the role of these in the activity of the peptide are unknown. In this study, we found that either cysteine replacements or S-S bond modifications influenced the activity of NCR247 against S. meliloti. Specifically, either substitution of cysteines for serines, changing the S-S bridges from cysteines 1-2, 3-4 to 1-3, 2-4 or oxidation of NCR247 lowered its activity against S. meliloti. We also determined that BacA specifically protected S. meliloti against oxidized NCR247. Due to the large number of different NCRs synthesized by legume root nodules and the importance of bacterial BacA proteins for prolonged host infections, these findings have important implications for analyzing the function of these novel peptides and the protective role of BacA in the bacterial response toward these peptides.

  11. Phloem Glutamine and the Regulation of O2 Diffusion in Legume Nodules.

    PubMed Central

    Neo, H. H.; Layzell, D. B.

    1997-01-01

    The aim of the present study was to test the hypothesis that the N content or the composition of the phloem sap that supplies nodulated roots may play a role in the feedback regulation of nitrogenase activity by increasing nodule resistance to O2 diffusion. Treating shoots of lupin (Lupinus albus cv Manitoba) or soybean (Glycine max L. Merr. cv Maple Arrow) with 100 [mu]L L-1 NH3 caused a 1.3-fold (lupin) and 2.6-fold (soybean) increase in the total N content of phloem sap without altering its C content. The increase in phloem N was due primarily to a 4.8-fold (lupin) and 10.5-fold (soybean) increase in the concentration of glutamine N. In addition, there was a decline in both the apparent nitrogenase activity and total nitrogenase activity that began within 4 h and reached about 54% of its initial activity within 6 h of the start of the NH3 treatment. However, the potential nitrogenase activity values in the treated plants were not significantly different from those of the control plants. These results provide evidence that changes in the N composition of the phloem sap, particularly the glutamine content, may increase nodule resistance to O2 diffusion and, thereby, down-regulate nodule metabolism and nitrogenase activity by controlling the supply of O2 to the bacteria-infected cells. PMID:12223605

  12. CYTOKININ OXIDASE/DEHYDROGENASE3 Maintains Cytokinin Homeostasis during Root and Nodule Development in Lotus japonicus1[OPEN

    PubMed Central

    Heckmann, Anne B.; Kelly, Simon

    2016-01-01

    Cytokinins are required for symbiotic nodule development in legumes, and cytokinin signaling responses occur locally in nodule primordia and in developing nodules. Here, we show that the Lotus japonicus Ckx3 cytokinin oxidase/dehydrogenase gene is induced by Nod factor during the early phase of nodule initiation. At the cellular level, pCkx3::YFP reporter-gene studies revealed that the Ckx3 promoter is active during the first cortical cell divisions of the nodule primordium and in growing nodules. Cytokinin measurements in ckx3 mutants confirmed that CKX3 activity negatively regulates root cytokinin levels. Particularly, tZ and DHZ type cytokinins in both inoculated and uninoculated roots were elevated in ckx3 mutants, suggesting that these are targets for degradation by the CKX3 cytokinin oxidase/dehydrogenase. The effect of CKX3 on the positive and negative roles of cytokinin in nodule development, infection and regulation was further clarified using ckx3 insertion mutants. Phenotypic analysis indicated that ckx3 mutants have reduced nodulation, infection thread formation and root growth. We also identify a role for cytokinin in regulating nodulation and nitrogen fixation in response to nitrate as ckx3 phenotypes are exaggerated at increased nitrate levels. Together, these findings show that cytokinin accumulation is tightly regulated during nodulation in order to balance the requirement for cell divisions with negative regulatory effects of cytokinin on infection events and root development. PMID:26644503

  13. Recombination and horizontal transfer of nodulation and ACC deaminase (acdS) genes within Alpha- and Betaproteobacteria nodulating legumes of the Cape Fynbos biome.

    PubMed

    Lemaire, Benny; Van Cauwenberghe, Jannick; Chimphango, Samson; Stirton, Charles; Honnay, Olivier; Smets, Erik; Muasya, A Muthama

    2015-11-01

    The goal of this work is to study the evolution and the degree of horizontal gene transfer (HGT) within rhizobial genera of both Alphaproteobacteria (Mesorhizobium, Rhizobium) and Betaproteobacteria (Burkholderia), originating from South African Fynbos legumes. By using a phylogenetic approach and comparing multiple chromosomal and symbiosis genes, we revealed conclusive evidence of high degrees of horizontal transfer of nodulation genes among closely related species of both groups of rhizobia, but also among species with distant genetic backgrounds (Rhizobium and Mesorhizobium), underscoring the importance of lateral transfer of symbiosis traits as an important evolutionary force among rhizobia of the Cape Fynbos biome. The extensive exchange of symbiosis genes in the Fynbos is in contrast with a lack of significant events of HGT among Burkholderia symbionts from the South American Cerrado and Caatinga biome. Furthermore, homologous recombination among selected housekeeping genes had a substantial impact on sequence evolution within Burkholderia and Mesorhizobium. Finally, phylogenetic analyses of the non-symbiosis acdS gene in Mesorhizobium, a gene often located on symbiosis islands, revealed distinct relationships compared to the chromosomal and symbiosis genes, suggesting a different evolutionary history and independent events of gene transfer. The observed events of HGT and incongruence between different genes necessitate caution in interpreting topologies from individual data types.

  14. Positioning the nodule, the hormone dictum

    PubMed Central

    Ding, Yiliang

    2009-01-01

    The formation of a nitrogen-fixing nodule involves two diverse developmental processes in the legume root: infection thread initiation in epidermal cells and nodule primordia formation in the cortex. Several plant hormones have been reported to positively or negatively regulate nodulation. These hormones function at different stages in the nodulation process and may facilitate the coordinated development of the epidermal and cortical developmental programs that are necessary to allow bacterial infection into the developing nodule. In this paper, we review and discuss how the tissue specific nature of hormonal action dictates where, when and how a nodule is formed. PMID:19649179

  15. NopP, a phosphorylated effector of Rhizobium sp. strain NGR234, is a major determinant of nodulation of the tropical legumes Flemingia congesta and Tephrosia vogelii.

    PubMed

    Skorpil, Peter; Saad, Maged M; Boukli, Nawal M; Kobayashi, Hajime; Ares-Orpel, Florencia; Broughton, William J; Deakin, William J

    2005-09-01

    Rhizobium sp. NGR234 nodulates many plants, some of which react to proteins secreted via a type three secretion system (T3SS) in a positive- (Flemingia congesta, Tephrosia vogelii) or negative- (Crotalaria juncea, Pachyrhizus tuberosus) manner. T3SSs are devices that Gram-negative bacteria use to inject effector proteins into the cytoplasm of eukaryotic cells. The only two rhizobial T3SS effector proteins characterized to date are NopL and NopP of NGR234. NopL can be phosphorylated by plant kinases and we show this to be true for NopP as well. Mutation of nopP leads to a dramatic reduction in nodule numbers on F. congesta and T. vogelii. Concomitant mutation of nopL and nopP further diminishes nodulation capacity to levels that, on T. vogelii, are lower than those produced by the T3SS null mutant NGR(Omega)rhcN. We also show that the T3SS of NGR234 secretes at least one additional effector, which remains to be identified. In other words, NGR234 secretes a cocktail of effectors, some of which have positive effects on nodulation of certain plants while others are perceived negatively and block nodulation. NopL and NopP are two components of this mix that extend the ability of NGR234 to nodulate certain legumes.

  16. Ectopic expression of miR160 results in auxin hypersensitivity, cytokinin hyposensitivity, and inhibition of symbiotic nodule development in soybean.

    PubMed

    Turner, Marie; Nizampatnam, Narasimha Rao; Baron, Mathieu; Coppin, Stéphanie; Damodaran, Suresh; Adhikari, Sajag; Arunachalam, Shivaram Poigai; Yu, Oliver; Subramanian, Senthil

    2013-08-01

    Symbiotic root nodules in leguminous plants result from interaction between the plant and nitrogen-fixing rhizobia bacteria. There are two major types of legume nodules, determinate and indeterminate. Determinate nodules do not have a persistent meristem, while indeterminate nodules have a persistent meristem. Auxin is thought to play a role in the development of both these types of nodules. However, inhibition of rootward auxin transport at the site of nodule initiation is crucial for the development of indeterminate nodules but not determinate nodules. Using the synthetic auxin-responsive DR5 promoter in soybean (Glycine max), we show that there is relatively low auxin activity during determinate nodule initiation and that it is restricted to the nodule periphery subsequently during development. To examine if and what role auxin plays in determinate nodule development, we generated soybean composite plants with altered sensitivity to auxin. We overexpressed microRNA393 to silence the auxin receptor gene family, and these roots were hyposensitive to auxin. These roots nodulated normally, suggesting that only minimal/reduced auxin signaling is required for determinate nodule development. We overexpressed microRNA160 to silence a set of repressor auxin response factor transcription factors, and these roots were hypersensitive to auxin. These roots were not impaired in epidermal responses to rhizobia but had significantly reduced nodule primordium formation, suggesting that auxin hypersensitivity inhibits nodule development. These roots were also hyposensitive to cytokinin and had attenuated expression of key nodulation-associated transcription factors known to be regulated by cytokinin. We propose a regulatory feedback loop involving auxin and cytokinin during nodulation.

  17. Rhizobium cauense sp. nov., isolated from root nodules of the herbaceous legume Kummerowia stipulacea grown in campus lawn soil.

    PubMed

    Liu, Tian Yan; Li, Ying; Liu, Xiao Xiao; Sui, Xin Hua; Zhang, Xiao Xia; Wang, En Tao; Chen, Wen Xin; Chen, Wen Feng; Puławska, Joanna

    2012-10-01

    Three bacterial isolates (CCBAU 101002(T), CCBAU 101000 and CCBAU 101001) originating from root nodules of the herbaceous legume Kummerowia stipulacea grown in the campus lawn of China Agricultural University were characterized with a polyphasic taxonomic approach. Comparative 16S rRNA gene sequence analysis showed that the isolates shared 99.85-99.92% sequence similarities and had the highest similarities to the type strains of Rhizobium mesoamericanum (99.31%), R. endophyticum (98.54%), R. tibeticum (98.38%) and R. grahamii (98.23%). Sequence similarity of four concatenated housekeeping genes (atpD, glnII, recA and rpoB) between CCBAU 101002(T) and its closest neighbor (R. grahamii) was 92.05%. DNA-DNA hybridization values between strain CCBAU 101002(T) and the four type strains of the most closely related Rhizobium species were less than 28.4±0.8%. The G+C mol% of the genomic DNA for strain CCBAU 101002(T) was 58.5% (Tm). The major respiratory quinone was ubiquinone (Q-10). Summed feature 8 (18:1ω7cis/18:1ω6cis) and 16:0 were the predominant fatty acids. Strain CCBAU 101002(T) contained phosphatidylcholine and phosphatidylethanolamine as major polar lipids, and phosphatidylglycerol and cardiolipin as minor ones. No glycolipid was detected. Unlike other strains, this novel species could utilize dulcite or sodium pyruvate as sole carbon sources and it was resistant to 2% (w/v) NaCl. On the basis of the polyphasic study, a new species Rhizobium cauense sp. nov. is proposed, with CCBAU 101002(T) (=LMG 26832(T)=HAMBI 3288(T)) as the type strain.

  18. Glutamine synthetase I-deficiency in Mesorhizobium loti differentially affects nodule development and activity in Lotus japonicus.

    PubMed

    Chungopast, Sirinapa; Thapanapongworakul, Pilunthana; Matsuura, Hiroyuki; Van Dao, Tan; Asahi, Toshimasa; Tada, Kuninao; Tajima, Shigeyuki; Nomura, Mika

    2014-03-01

    In this study, we focused on the effect of glutamine synthetase (GSI) activity in Mesorhizobium loti on the symbiosis between the host plant, Lotus japonicus, and the bacteroids. We used a signature-tagged mutant of M. loti (STM30) with a transposon inserted into the GSI (mll0343) gene. The L. japonicus plants inoculated with STM30 had significantly more nodules, and the occurrence of senesced nodules was much higher than in plants inoculated with the wild-type. The acetylene reduction activity (ARA) per nodule inoculated with STM30 was lowered compared to the control. Also, the concentration of chlorophyll, glutamine, and asparagine in leaves of STM30-infected plants was found to be reduced. Taken together, these data demonstrate that a GSI deficiency in M. loti differentially affects legume-rhizobia symbiosis by modifying nodule development and metabolic processes.

  19. Phytohormone regulation of legume-rhizobia interactions.

    PubMed

    Ferguson, Brett J; Mathesius, Ulrike

    2014-07-01

    The symbiosis between legumes and nitrogen fixing bacteria called rhizobia leads to the formation of root nodules. Nodules are highly organized root organs that form in response to Nod factors produced by rhizobia, and they provide rhizobia with a specialized niche to optimize nutrient exchange and nitrogen fixation. Nodule development and invasion by rhizobia is locally controlled by feedback between rhizobia and the plant host. In addition, the total number of nodules on a root system is controlled by a systemic mechanism termed 'autoregulation of nodulation'. Both the local and the systemic control of nodulation are regulated by phytohormones. There are two mechanisms by which phytohormone signalling is altered during nodulation: through direct synthesis by rhizobia and through indirect manipulation of the phytohormone balance in the plant, triggered by bacterial Nod factors. Recent genetic and physiological evidence points to a crucial role of Nod factor-induced changes in the host phytohormone balance as a prerequisite for successful nodule formation. Phytohormones synthesized by rhizobia enhance symbiosis effectiveness but do not appear to be necessary for nodule formation. This review provides an overview of recent advances in our understanding of the roles and interactions of phytohormones and signalling peptides in the regulation of nodule infection, initiation, positioning, development, and autoregulation. Future challenges remain to unify hormone-related findings across different legumes and to test whether hormone perception, response, or transport differences among different legumes could explain the variety of nodules types and the predisposition for nodule formation in this plant family. In addition, the molecular studies carried out under controlled conditions will need to be extended into the field to test whether and how phytohormone contributions by host and rhizobial partners affect the long term fitness of the host and the survival and

  20. Sulphadimethoxine inhibits Phaseolus vulgaris root growth and development of N-fixing nodules.

    PubMed

    Sartorius, Marilena; Riccio, Anna; Cermola, Michele; Casoria, Paolo; Patriarca, Eduardo J; Taté, Rosarita

    2009-07-01

    Sulphonamides contamination of cultivated lands occurs through the recurrent spreading of animal wastes from intensive farming. The aim of this study was to test the effect(s) of sulphadimethoxine on the beneficial N-fixing Rhizobium etli-Phaseolus vulgaris symbiosis under laboratory conditions. The consequence of increasing concentrations of sulphadimethoxine on the growth ability of free-living R. etli bacteria, as well as on seed germination, seedling development and growth of common bean plants was examined. We have established that sulphadimethoxine inhibited the growth of both symbiotic partners in a dose-dependent manner. Bacterial invasion occurring in developing root nodules was visualized by fluorescence microscopy generating EGFP-marked R. etli bacteria. Our results proved that the development of symbiotic N-fixing root nodules is hampered by sulphadimethoxine thus identifying sulphonamides as toxic compounds for the Rhizobium-legume symbiosis: a low-input sustainable agricultural practice.

  1. Strigolactones in the Rhizobium-legume symbiosis: Stimulatory effect on bacterial surface motility and down-regulation of their levels in nodulated plants.

    PubMed

    Peláez-Vico, María A; Bernabéu-Roda, Lydia; Kohlen, Wouter; Soto, María J; López-Ráez, Juan A

    2016-04-01

    Strigolactones (SLs) are multifunctional molecules acting as modulators of plant responses under nutrient deficient conditions. One of the roles of SLs is to promote beneficial association with arbuscular mycorrhizal (AM) fungi belowground under such stress conditions, mainly phosphorus shortage. Recently, a role of SLs in the Rhizobium-legume symbiosis has been also described. While SLs' function in AM symbiosis is well established, their role in the Rhizobium-legume interaction is still emerging. Recently, SLs have been suggested to stimulate surface motility of rhizobia, opening the possibility that they could also act as molecular cues. The possible effect of SLs in the motility in the alfalfa symbiont Sinorhizobium meliloti was investigated, showing that the synthetic SL analogue GR24 stimulates swarming motility in S. meliloti in a dose-dependent manner. On the other hand, it is known that SL production is regulated by nutrient deficient conditions and by AM symbiosis. Using the model alfalfa-S. meliloti, the impact of phosphorus and nitrogen deficiency, as well as of nodulation on SL production was also assessed. The results showed that phosphorus starvation promoted SL biosynthesis, which was abolished by nitrogen deficiency. In addition, a negative effect of nodulation on SL levels was detected, suggesting a conserved mechanism of SL regulation upon symbiosis establishment.

  2. CAROTENOID CLEAVAGE DIOXYGENASE 7 modulates plant growth, reproduction, senescence, and determinate nodulation in the model legume Lotus japonicus

    PubMed Central

    Liu, Junwei; Novero, Mara; Charnikhova, Tatsiana; Ferrandino, Alessandra; Schubert, Andrea; Ruyter-Spira, Carolien; Bonfante, Paola; Lovisolo, Claudio; Bouwmeester, Harro J.; Cardinale, Francesca

    2013-01-01

    Strigolactones (SLs) are newly identified hormones that regulate multiple aspects of plant development, infection by parasitic weeds, and mutualistic symbiosis in the roots. In this study, the role of SLs was studied for the first time in the model plant Lotus japonicus using transgenic lines silenced for CAROTENOID CLEAVAGE DIOXYGENASE 7 (LjCCD7), the orthologue of Arabidopsis More Axillary Growth 3. Transgenic LjCCD7-silenced plants displayed reduced height due to shorter internodes, and more branched shoots and roots than the controls, and an increase in total plant biomass, while their root:shoot ratio remained unchanged. Moreover, these lines had longer primary roots, delayed senescence, and reduced flower/pod numbers from the third round of flower and pod setting onwards. Only a mild reduction in determinate nodule numbers and hardly any impact on the colonization by arbuscular mycorrhizal fungi were observed. The results show that the impairment of CCD7 activity in L. japonicus leads to a phenotype linked to SL functions, but with specific features possibly due to the peculiar developmental pattern of this plant species. It is believed that the data also link determinate nodulation, plant reproduction, and senescence to CCD7 function for the first time. PMID:23567864

  3. Enhanced nodulation and nodule development by nolR mutants of Sinorhizobium medicae on specific Medicago host genotypes.

    PubMed

    Sugawara, Masayuki; Sadowsky, Michael J

    2014-04-01

    The nolR gene encodes a negatively acting, transcriptional regulatory protein of core Nod-factor biosynthetic genes in the sinorhizobia. Although previous reports showed that nolR modulates Nod-factor production and enhances nodulation speed of Sinorhizobium meliloti on alfalfa, there have been no reports for the symbiotic function of this gene in the S. medicae-Medicago truncatula symbiosis. Here, we constructed an nolR mutant of S. medicae WSM419 and evaluated mutant and wild-type strains for their nodulation ability, competitiveness, host specificity, and density-dependent nodulation phenotypes. When the mutant was inoculated at low and medium population densities, it showed enhanced nodule formation during the initial stages of nodulation. Results of quantitative competitive nodulation assays indicated that an nolR mutant had 2.3-fold greater competitiveness for nodulation on M. truncatula 'A17' than did the wild-type strain. Moreover, the nodulation phenotype of the nolR mutant differed among Medicago genotypes and showed significantly enhanced nodule development on M. tricycla. Taken together, these results indicated that mutation of nolR in S. medicae positively influenced nodule initiation, competitive nodulation, and nodule development at later nodulation stages. This may allow nolR mutants of S. medicae to have a selective advantage under field conditions.

  4. LegumeIP: an integrative database for comparative genomics and transcriptomics of model legumes.

    PubMed

    Li, Jun; Dai, Xinbin; Liu, Tingsong; Zhao, Patrick Xuechun

    2012-01-01

    Legumes play a vital role in maintaining the nitrogen cycle of the biosphere. They conduct symbiotic nitrogen fixation through endosymbiotic relationships with bacteria in root nodules. However, this and other characteristics of legumes, including mycorrhization, compound leaf development and profuse secondary metabolism, are absent in the typical model plant Arabidopsis thaliana. We present LegumeIP (http://plantgrn.noble.org/LegumeIP/), an integrative database for comparative genomics and transcriptomics of model legumes, for studying gene function and genome evolution in legumes. LegumeIP compiles gene and gene family information, syntenic and phylogenetic context and tissue-specific transcriptomic profiles. The database holds the genomic sequences of three model legumes, Medicago truncatula, Glycine max and Lotus japonicus plus two reference plant species, A. thaliana and Populus trichocarpa, with annotations based on UniProt, InterProScan, Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes databases. LegumeIP also contains large-scale microarray and RNA-Seq-based gene expression data. Our new database is capable of systematic synteny analysis across M. truncatula, G. max, L. japonicas and A. thaliana, as well as construction and phylogenetic analysis of gene families across the five hosted species. Finally, LegumeIP provides comprehensive search and visualization tools that enable flexible queries based on gene annotation, gene family, synteny and relative gene expression.

  5. Effects of Endogenous Salicylic Acid on Nodulation in the Model Legumes Lotus japonicus and Medicago truncatula1[W

    PubMed Central

    Stacey, Gary; McAlvin, Crystal Bickley; Kim, Sung-Yong; Olivares, José; Soto, María José

    2006-01-01

    The exogenous addition of salicylic acid (SA) was previously shown to inhibit indeterminate but not determinate-type nodulation. We sought to extend these results by modulating endogenous levels of SA through the transgenic expression of salicylate hydroxylase (NahG) in both stably transformed Lotus japonicus and composite Medicago truncatula plants. NahG expression in L. japonicus resulted in a marked reduction of SA levels. This reduction correlated with an increase in the number of infections and mean nodule number when compared to controls. However, a complicating factor was that NahG-expressing plants had greater root growth. Spot inoculations of NahG-expressing L. japonicus plants confirmed increased nodulation in these plants. Consistent with the reported inhibitory effects of exogenous SA on indeterminate-type nodulation, NahG expression in M. truncatula plants led to enhanced nodulation and infection. These data point to an important role for SA-mediated plant defense pathways in controlling nodule formation on both determinate and indeterminate nodule-forming hosts. PMID:16798946

  6. [The Effect of Cadmium on the Efficiency of Development of Legume-Rhizobium Symbiosis].

    PubMed

    Chuhukova, O V; Postrigan, B N; Baimiev, A Kh; Chemeris, A V

    2015-01-01

    Screening of nodule bacteria (rhizobia) forming symbiotic relationships with legumes has been performed in order to isolate strains resistant to cadmium ions in a wide range of concentrations (6-132 mg/kg). The effect ofcadmium salts (6, 12, 24 mg/kg) on the legume-rhizobium symbiosis ofthe pea Pisum sativum L. with Rhizobium leguminosarum and of the fodder galega Galega orientalis Lam. with Rhizobium galegae has been studied under experimental laboratory conditions. No statistically significant differences have been revealed in the growth and biomass of plants with regard to the control in the range of concentrations given above. However, it was found that cadmium inhibited nodulation in P. sativum and stimulated it in G. orientalis.

  7. Transcriptional networks leading to symbiotic nodule organogenesis.

    PubMed

    Soyano, Takashi; Hayashi, Makoto

    2014-08-01

    The symbiosis with nitrogen-fixing bacteria leading to root nodules is a relatively recent evolutionary innovation and limited to a distinct order of land plants. It has long been a mystery how plants have invented this complex trait. However, recent advances in molecular genetics of model legumes has elucidated genes involved in the development of root nodules, providing insights into this process. Here we discuss how the de novo assembly of transcriptional networks may account for the predisposition to nodulate. Transcriptional networks and modes of gene regulation from the arbuscular mycorrhizal symbiosis, nitrate responses and aspects of lateral root development have likely all contributed to the emergence and development of root nodules.

  8. Diversity pattern of nitrogen fixing microbes in nodules of Trifolium arvense (L.) at different initial stages of ecosystem development

    NASA Astrophysics Data System (ADS)

    Schulz, S.; Engel, M.; Fischer, D.; Buegger, F.; Elmer, M.; Welzl, G.; Schloter, M.

    2013-02-01

    Legumes can be considered as pioneer plants during ecosystem development, as they form a symbiosis with different nitrogen fixing rhizobia species, which enable the plants to grow on soils with low available nitrogen content. In this study we compared the abundance and diversity of nitrogen fixing microbes based on the functional marker gene nifH, which codes for a subunit of the Fe-protein of the dinitrogenase reductase, in nodules of different size classes of Trifolium arvense (L.). Additionally, carbon and nitrogen contents of the bulk soil and plant material were measured. Plants were harvested from different sites, reflecting 2 (2a) and 5 (5a) yr of ecosystem development, of an opencast lignite mining area in the south of Cottbus, Lower Lusatia (Germany) where the artificial catchment "Chicken Creek" was constructed to study the development of terrestrial ecosystems. Plants from the 5a site revealed higher amounts of carbon and nitrogen, although nifH gene abundances in the nodules and carbon and nitrogen contents between the two soils did not differ significantly. Analysis of the nifH clone libraries showed a significant effect of the nodule size on the community composition of nitrogen fixing microbes. Medium sized nodules (2-5 mm) contained a uniform community composed of Rhizobium leguminosarum bv. trifolii, whereas the small nodules (<2 mm) consisted of a diverse community including clones with non-Rhizobium nifH gene sequences. Regarding the impact of the soil age on the community composition a clear distinction between the small and the medium nodules can be made. While clone libraries from the medium nodules were pretty similar at both soil ages, soil age had a significant effect on the community compositions of the small nodules, where the proportion of R. leguminosarum bv. trifolii increased with soil age.

  9. Diversity pattern of nitrogen fixing microbes in nodules of Trifolium arvense (L.) at different initial stages of ecosystem development

    NASA Astrophysics Data System (ADS)

    Schulz, S.; Engel, M.; Fischer, D.; Buegger, F.; Elmer, M.; Welzl, G.; Schloter, M.

    2012-09-01

    Legumes can be considered as pioneer plants during ecosystem development, as they form a symbiosis with different nitrogen fixing rhizobia species, which enable the plants to grow on soils with low available nitrogen content. In this study we compared the abundance and diversity of nitrogen fixing microbes based on the functional marker gene nifH, which codes for a subunit of the Fe-protein of the dinitrogenase reductase, in nodules of different size classes of Trifolium arvense (L.). Additionally, carbon and nitrogen contents of the bulk soil and plant material were measured. Plants were harvested from different sites, reflecting 2 (2a) and 5 (5a) yr of ecosystem development, of an opencast lignite mining area in the south of Cottbus, Lower Lusatia (Germany) where the artificial catchment "Chicken Creek" was constructed to study the development of terrestrial ecosystems. Plants from the 5a site revealed higher amounts of carbon and nitrogen, although nifH gene abundances in the nodules and carbon and nitrogen contents between the two soils did not differ significantly. Analysis of the nifH clone libraries showed a significant effect of the nodule size on the community composition of nitrogen fixing microbes. Medium sized nodules (2-5 mm) contained a uniform community composed of Rhizobium leguminosarum bv. trifolii, whereas the small nodules (< 2 mm) consisted of a diverse community including clones with non-Rhizobium nifH gene sequences. Regarding the impact of the soil age on the community composition a clear distinction between the small and the medium nodules can be made. While clone libraries from the medium nodules were pretty similar at both soil ages, soil age had a significant effect on the community compositions of the small nodules, where the proportion of R. leguminosarum bv. trifolii increased with soil age.

  10. Leghemoglobin green derivatives with nitrated hemes evidence production of highly reactive nitrogen species during aging of legume nodules.

    PubMed

    Navascués, Joaquín; Pérez-Rontomé, Carmen; Gay, Marina; Marcos, Manuel; Yang, Fei; Walker, F Ann; Desbois, Alain; Abián, Joaquín; Becana, Manuel

    2012-02-14

    Globins constitute a superfamily of proteins widespread in all kingdoms of life, where they fulfill multiple functions, such as efficient O(2) transport and modulation of nitric oxide bioactivity. In plants, the most abundant Hbs are the symbiotic leghemoglobins (Lbs) that scavenge O(2) and facilitate its diffusion to the N(2)-fixing bacteroids in nodules. The biosynthesis of Lbs during nodule formation has been studied in detail, whereas little is known about the green derivatives of Lbs generated during nodule senescence. Here we characterize modified forms of Lbs, termed Lba(m), Lbc(m), and Lbd(m), of soybean nodules. These green Lbs have identical globins to the parent red Lbs but their hemes are nitrated. By combining UV-visible, MS, NMR, and resonance Raman spectroscopies with reconstitution experiments of the apoprotein with protoheme or mesoheme, we show that the nitro group is on the 4-vinyl. In vitro nitration of Lba with excess nitrite produced several isomers of nitrated heme, one of which is identical to those found in vivo. The use of antioxidants, metal chelators, and heme ligands reveals that nitration is contingent upon the binding of nitrite to heme Fe, and that the reactive nitrogen species involved derives from nitrous acid and is most probably the nitronium cation. The identification of these green Lbs provides conclusive evidence that highly oxidizing and nitrating species are produced in nodules leading to nitrosative stress. These findings are consistent with a previous report showing that the modified Lbs are more abundant in senescing nodules and have aberrant O(2) binding.

  11. Development and Evaluation of LEGUME ID: A ToolBook Multimedia Module.

    ERIC Educational Resources Information Center

    Hannaway, David B.; And Others

    1992-01-01

    Describes the development and advantages of LEGUME ID, a multimedia module for agricultural education. LEGUME ID is an example of how teachers, given the opportunity through accessible computer software programs, can create powerful teaching tools. Summarized is a student response to the use of this teacher-produced software program. (MCO)

  12. Leghemoglobin is nitrated in functional legume nodules in a tyrosine residue within the heme cavity by a nitrite/peroxide-dependent mechanism

    PubMed Central

    Sainz, Martha; Calvo-Begueria, Laura; Pérez-Rontomé, Carmen; Wienkoop, Stefanie; Abián, Joaquín; Staudinger, Christiana; Bartesaghi, Silvina; Radi, Rafael; Becana, Manuel

    2015-01-01

    SUMMARY Protein Tyr nitration is a post-translational modification yielding 3-nitrotyrosine (NO2-Tyr). Formation of NO2-Tyr is generally considered as a marker of nitroxidative stress and is involved in some human pathophysiological disorders, but it has been poorly studied in plants. Leghemoglobin (Lb) is an abundant hemeprotein of legume nodules that plays an essential role as O2 transporter. Liquid chromatography coupled to tandem mass spectrometry was used for a targeted search and quantification of NO2-Tyr in Lbs. For all Lbs examined, Tyr30, located in the distal heme pocket, is the major target of nitration. Lower amounts were found for NO2-Tyr25 and NO2-Tyr133. Nitrated Lb and other as yet unidentified nitrated proteins were also detected in nodules of plants not receiving NO3− and were found to decrease during senescence. This demonstrates formation of nitric oxide (•NO) and NO2− by alternative means to nitrate reductase, probably via a NO synthase-like enzyme, and strongly suggests that nitrated proteins perform biological functions and are not merely metabolic byproducts. In vitro assays with purified Lbs revealed that Tyr nitration requires NO2− + H2O2 and that peroxynitrite is not an efficient inducer of nitration, possibly by isomerizing it to NO3−. Nitrated Lb is formed via oxoferryl Lb, which generates nitrogen dioxide and tyrosyl radicals. This mechanism is distinctly different from that involved in heme nitration. Formation of NO2-Tyr in Lbs is a consequence of active metabolism in functional nodules, where Lbs may act as a sink of toxic peroxynitrite and may play a protective role in the symbiosis. PMID:25603991

  13. Leghemoglobin is nitrated in functional legume nodules in a tyrosine residue within the heme cavity by a nitrite/peroxide-dependent mechanism.

    PubMed

    Sainz, Martha; Calvo-Begueria, Laura; Pérez-Rontomé, Carmen; Wienkoop, Stefanie; Abián, Joaquín; Staudinger, Christiana; Bartesaghi, Silvina; Radi, Rafael; Becana, Manuel

    2015-03-01

    Protein tyrosine (Tyr) nitration is a post-translational modification yielding 3-nitrotyrosine (NO2 -Tyr). Formation of NO2 -Tyr is generally considered as a marker of nitro-oxidative stress and is involved in some human pathophysiological disorders, but has been poorly studied in plants. Leghemoglobin (Lb) is an abundant hemeprotein of legume nodules that plays an essential role as an O2 transporter. Liquid chromatography coupled to tandem mass spectrometry was used for a targeted search and quantification of NO2 -Tyr in Lb. For all Lbs examined, Tyr30, located in the distal heme pocket, is the major target of nitration. Lower amounts were found for NO2 -Tyr25 and NO2 -Tyr133. Nitrated Lb and other as yet unidentified nitrated proteins were also detected in nodules of plants not receiving NO3- and were found to decrease during senescence. This demonstrates formation of nitric oxide (˙NO) and NO2- by alternative means to nitrate reductase, probably via a ˙NO synthase-like enzyme, and strongly suggests that nitrated proteins perform biological functions and are not merely metabolic byproducts. In vitro assays with purified Lb revealed that Tyr nitration requires NO2- + H2 O2 and that peroxynitrite is not an efficient inducer of nitration, probably because Lb isomerizes it to NO3-. Nitrated Lb is formed via oxoferryl Lb, which generates nitrogen dioxide and tyrosyl radicals. This mechanism is distinctly different from that involved in heme nitration. Formation of NO2 -Tyr in Lb is a consequence of active metabolism in functional nodules, where Lb may act as a sink of toxic peroxynitrite and may play a protective role in the symbiosis.

  14. Symbiosis specificity in the legume: rhizobial mutualism.

    PubMed

    Wang, Dong; Yang, Shengming; Tang, Fang; Zhu, Hongyan

    2012-03-01

    Legume plants are able to engage in root nodule symbiosis with nitrogen-fixing soil bacteria, collectively called rhizobia. This mutualistic association is highly specific, such that each rhizobial species/strain interacts with only a specific group of legumes, and vice versa. Symbiosis specificity can occur at multiple phases of the interaction, ranging from initial bacterial attachment and infection to late nodule development associated with nitrogen fixation. Genetic control of symbiosis specificity is complex, involving fine-tuned signal communication between the symbiotic partners. Here we review our current understanding of the mechanisms used by the host and bacteria to choose their symbiotic partners, with a special focus on the role that the host immunity plays in controlling the specificity of the legume - rhizobial symbiosis.

  15. Transcriptome sequencing and marker development for four underutilized legumes.

    PubMed

    Chapman, Mark A

    2015-02-01

    • Combating threats to food and nutrition security in the context of climate change and global population increase is one of the highest priorities of major international organizations. Hundreds of species are grown on a small scale in some of the most drought/flood-prone regions of the world and as such may harbor some of the most environmentally tolerant crops (and alleles). • In this study, transcriptomes were sequenced, assembled, and annotated for four underutilized legume crops. Microsatellite markers were identified in each species, as well as a conserved orthologous set of markers for cross-family phylogenetics and comparative mapping, which were ground-truthed on a panel of diverse legume germplasm. • An understanding of these underutilized legumes will inform crop selection and breeding by allowing the investigation of genetic variation and the genetic basis of adaptive traits to be established.

  16. Transcriptome sequencing and marker development for four underutilized legumes1

    PubMed Central

    Chapman, Mark A.

    2015-01-01

    • Premise of the study: Combating threats to food and nutrition security in the context of climate change and global population increase is one of the highest priorities of major international organizations. Hundreds of species are grown on a small scale in some of the most drought/flood-prone regions of the world and as such may harbor some of the most environmentally tolerant crops (and alleles). • Methods and Results: In this study, transcriptomes were sequenced, assembled, and annotated for four underutilized legume crops. Microsatellite markers were identified in each species, as well as a conserved orthologous set of markers for cross-family phylogenetics and comparative mapping, which were ground-truthed on a panel of diverse legume germplasm. • Conclusions: An understanding of these underutilized legumes will inform crop selection and breeding by allowing the investigation of genetic variation and the genetic basis of adaptive traits to be established. PMID:25699221

  17. Expression of the Bradyrhizobium japonicum type III secretion system in legume nodules and analysis of the associated tts box promoter.

    PubMed

    Zehner, Susanne; Schober, Grit; Wenzel, Mandy; Lang, Kathrin; Göttfert, Michael

    2008-08-01

    In Bradyrhizobium japonicum, as in some other rhizobia, symbiotic efficiency is influenced by a type III secretion system (T3SS). Most genes encoding the transport machinery and secreted proteins are preceded by a conserved 30-bp motif, the type-three secretion (tts) box. In this study, we found that regions downstream of 34 tts boxes are transcribed. For nopB, nopL, and gunA2, the transcriptional start sites were found to be 12, 11, and 10 bp downstream of their tts boxes, respectively. The deletion of this motif or modification of two or more conserved residues strongly reduced expression of nopB. This indicates that the tts box is an essential promoter element. Data obtained with lacZ reporter gene fusions of five genes preceded by a tts box (gunA2, nopB, rhcV, nopL, and blr1806) revealed that they are expressed in 4-week-old nodules of Macroptilium atropurpureum. These data suggest that the T3SS is active in mature nitrogen-fixing nodules. The two-component response regulator TtsI is required for the expression of rhcV, nopL, and blr1806 in bacteroids. Staining of inoculated roots showed that nopB is also expressed in early infection stages.

  18. A gene-based map of the Nod factor-independent Aeschynomene evenia sheds new light on the evolution of nodulation and legume genomes

    PubMed Central

    Chaintreuil, Clémence; Rivallan, Ronan; Bertioli, David J.; Klopp, Christophe; Gouzy, Jérôme; Courtois, Brigitte; Leleux, Philippe; Martin, Guillaume; Rami, Jean-François; Gully, Djamel; Parrinello, Hugues; Séverac, Dany; Patrel, Delphine; Fardoux, Joël; Ribière, William; Boursot, Marc; Cartieaux, Fabienne; Czernic, Pierre; Ratet, Pascal; Mournet, Pierre; Giraud, Eric; Arrighi, Jean-François

    2016-01-01

    Aeschynomene evenia has emerged as a new model legume for the deciphering of the molecular mechanisms of an alternative symbiotic process that is independent of the Nod factors. Whereas most of the research on nitrogen-fixing symbiosis, legume genetics and genomics has so far focused on Galegoid and Phaseolid legumes, A. evenia falls in the more basal and understudied Dalbergioid clade along with peanut (Arachis hypogaea). To provide insights into the symbiotic genes content and the structure of the A. evenia genome, we established a gene-based genetic map for this species. Firstly, an RNAseq analysis was performed on the two parental lines selected to generate a F2 mapping population. The transcriptomic data were used to develop molecular markers and they allowed the identification of most symbiotic genes. The resulting map comprised 364 markers arranged in 10 linkage groups (2n = 20). A comparative analysis with the sequenced genomes of Arachis duranensis and A. ipaensis, the diploid ancestors of peanut, indicated blocks of conserved macrosynteny. Altogether, these results provided important clues regarding the evolution of symbiotic genes in a Nod factor-independent context. They provide a basis for a genome sequencing project and pave the way for forward genetic analysis of symbiosis in A. evenia. PMID:27298380

  19. A gene-based map of the Nod factor-independent Aeschynomene evenia sheds new light on the evolution of nodulation and legume genomes.

    PubMed

    Chaintreuil, Clémence; Rivallan, Ronan; Bertioli, David J; Klopp, Christophe; Gouzy, Jérôme; Courtois, Brigitte; Leleux, Philippe; Martin, Guillaume; Rami, Jean-François; Gully, Djamel; Parrinello, Hugues; Séverac, Dany; Patrel, Delphine; Fardoux, Joël; Ribière, William; Boursot, Marc; Cartieaux, Fabienne; Czernic, Pierre; Ratet, Pascal; Mournet, Pierre; Giraud, Eric; Arrighi, Jean-François

    2016-08-01

    Aeschynomene evenia has emerged as a new model legume for the deciphering of the molecular mechanisms of an alternative symbiotic process that is independent of the Nod factors. Whereas most of the research on nitrogen-fixing symbiosis, legume genetics and genomics has so far focused on Galegoid and Phaseolid legumes, A. evenia falls in the more basal and understudied Dalbergioid clade along with peanut (Arachis hypogaea). To provide insights into the symbiotic genes content and the structure of the A. evenia genome, we established a gene-based genetic map for this species. Firstly, an RNAseq analysis was performed on the two parental lines selected to generate a F2 mapping population. The transcriptomic data were used to develop molecular markers and they allowed the identification of most symbiotic genes. The resulting map comprised 364 markers arranged in 10 linkage groups (2n = 20). A comparative analysis with the sequenced genomes of Arachis duranensis and A. ipaensis, the diploid ancestors of peanut, indicated blocks of conserved macrosynteny. Altogether, these results provided important clues regarding the evolution of symbiotic genes in a Nod factor-independent context. They provide a basis for a genome sequencing project and pave the way for forward genetic analysis of symbiosis in A. evenia.

  20. Genetic considerations in developing germplasm sources of native legumes

    USDA-ARS?s Scientific Manuscript database

    There is a great need for biological diversity in reseeding efforts on western rangelands. Legumes provide a crucial component of reseedings, by allowing for higher forage quality, soil nitrogen fixation, pollinator sustenance, and wildlife and wild-fowl feed. In efforts to collect and produce see...

  1. Regulatory nodD1 and nodD2 genes of Rhizobium tropici strain CIAT 899 and their roles in the early stages of molecular signaling and host-legume nodulation.

    PubMed

    del Cerro, Pablo; Rolla-Santos, Amanda Alves Paiva; Gomes, Douglas Fabiano; Marks, Bettina Berquó; Pérez-Montaño, Francisco; Rodríguez-Carvajal, Miguel Ángel; Nakatani, André Shigueyoshi; Gil-Serrano, Antonio; Megías, Manuel; Ollero, Francisco Javier; Hungria, Mariangela

    2015-03-28

    Nodulation and symbiotic nitrogen fixation are mediated by several genes, both of the host legume and of the bacterium. The rhizobial regulatory nodD gene plays a critical role, orchestrating the transcription of the other nodulation genes. Rhizobium tropici strain CIAT 899 is an effective symbiont of several legumes-with an emphasis on common bean (Phaseolus vulgaris)-and is unusual in carrying multiple copies of nodD, the roles of which remain to be elucidated. Phenotypes, Nod factors and gene expression of nodD1 and nodD2 mutants of CIAT 899 were compared with those of the wild type strain, both in the presence and in the absence of the nod-gene-inducing molecules apigenin and salt (NaCl). Differences between the wild type and mutants were observed in swimming motility and IAA (indole acetic acid) synthesis. In the presence of both apigenin and salt, large numbers of Nod factors were detected in CIAT 899, with fewer detected in the mutants. nodC expression was lower in both mutants; differences in nodD1 and nodD2 expression were observed between the wild type and the mutants, with variation according to the inducing molecule, and with a major role of apigenin with nodD1 and of salt with nodD2. In the nodD1 mutant, nodulation was markedly reduced in common bean and abolished in leucaena (Leucaena leucocephala) and siratro (Macroptilium atropurpureum), whereas a mutation in nodD2 reduced nodulation in common bean, but not in the other two legumes. Our proposed model considers that full nodulation of common bean by R. tropici requires both nodD1 and nodD2, whereas, in other legume species that might represent the original host, nodD1 plays the major role. In general, nodD2 is an activator of nod-gene transcription, but, in specific conditions, it can slightly repress nodD1. nodD1 and nodD2 play other roles beyond nodulation, such as swimming motility and IAA synthesis.

  2. Phenotypic and biochemical characterization of root nodule bacteria naturally associated with woody tree legumes in Saudi Arabia.

    PubMed

    Alshaharani, Thobayet Safar; Shetta, Nader Desouky

    2015-03-01

    Thirty root-nodulating bacteria isolates were obtained from the roots of Acacia ampliceps (Maslin), A. ehrenbergiana (Hayne.), A. saligna (Labill.), A. seyal (Del.), A. tortilis (Forssk.), A. tortilis subsp. raddiana (Savi.), Leucaena leucocephala (Lam.) and Vicia faba (L.) trees growing in the Riyadh region. The isolates' phenotypic and biochemical properties were characterized by assessing colony appearance, growth rate, resistance to antibiotics and heavy metals, and tolerance to salinity, elevated temperature and pH. All isolates had same colony morphology and grew on yeast extract mannitol and tryptone yeast agar, but not MGS media. The results also revealed considerable diversity among the isolates, which exhibited different patterns of resistance to abiotic stresses. Most isolates tolerated temperatures up to 37 degrees C and could grow from pH 5.5-8.5 and at a high NaCl concentration (2% w/v). The majority of isolates could utilize a variety of carbohydrates. Most of the isolates displayed resistance to antibiotics in the 75 microg ml(-1) range, with approximately 100 pg ml(-1) the maximum concentration at which growth was observed. All isolates were sensitive to aluminum and resistant to other heavy metals tested, and they were able to reduce nitrate and hydrolyze urea.

  3. Leguminous plants: inventors of root nodules to accommodate symbiotic bacteria.

    PubMed

    Suzaki, Takuya; Yoro, Emiko; Kawaguchi, Masayoshi

    2015-01-01

    Legumes and a few other plant species can establish a symbiotic relationship with nitrogen-fixing rhizobia, which enables them to survive in a nitrogen-deficient environment. During the course of nodulation, infection with rhizobia induces the dedifferentiation of host cells to form primordia of a symbiotic organ, the nodule, which prepares plants to accommodate rhizobia in host cells. While these nodulation processes are known to be genetically controlled by both plants and rhizobia, recent advances in studies on two model legumes, Lotus japonicus and Medicago truncatula, have provided great insight into the underlying plant-side molecular mechanism. In this chapter, we review such knowledge, with particular emphasis on two key processes of nodulation, nodule development and rhizobial invasion. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Profiling of Differentially Expressed Genes in Roots of Robinia pseudoacacia during Nodule Development Using Suppressive Subtractive Hybridization

    PubMed Central

    Wang, Xinye; Liu, Sisi; Zhang, Feilong; Wei, Gehong

    2013-01-01

    Background Legume-rhizobium symbiosis is a complex process that is regulated in the host plant cell through gene expression network. Many nodulin genes that are upregulated during different stages of nodulation have been identified in leguminous herbs. However, no nodulin genes in woody legume trees, such as black locust (Robinia pseudoacacia), have yet been reported. Methodology/Principal findings To identify the nodulin genes involved in R. pseudoacacia-Mesorhizobium amorphae CCNWGS0123 symbiosis, a suppressive subtractive hybridization approach was applied to reveal profiling of differentially expressed genes and two subtracted cDNA libraries each containing 600 clones were constructed. Then, 114 unigenes were identified from forward SSH library by differential screening and the putative functions of these translational products were classified into 13 categories. With a particular interest in regulatory genes, twenty-one upregulated genes encoding potential regulatory proteins were selected based on the result of reverse transcription-polymerase chain reaction (RT-PCR) analysis. They included nine putative transcription genes, eight putative post-translational regulator genes and four membrane protein genes. The expression patterns of these genes were further analyzed by quantitative RT-PCR at different stages of nodule development. Conclusions The data presented here offer the first insights into the molecular foundation underlying R. pseudoacacia–M. amorphae symbiosis. A number of regulatory genes screened in the present study revealed a high level of regulatory complexity (transcriptional, post-transcriptional, translational and post-translational) that is likely essential to develop symbiosis. In addition, the possible roles of these genes in black locust nodulation are discussed. PMID:23776436

  5. Profiling of differentially expressed genes in roots of Robinia pseudoacacia during nodule development using suppressive subtractive hybridization.

    PubMed

    Chen, Hongyan; Chou, Minxia; Wang, Xinye; Liu, Sisi; Zhang, Feilong; Wei, Gehong

    2013-01-01

    Legume-rhizobium symbiosis is a complex process that is regulated in the host plant cell through gene expression network. Many nodulin genes that are upregulated during different stages of nodulation have been identified in leguminous herbs. However, no nodulin genes in woody legume trees, such as black locust (Robinia pseudoacacia), have yet been reported. To identify the nodulin genes involved in R. pseudoacacia-Mesorhizobium amorphae CCNWGS0123 symbiosis, a suppressive subtractive hybridization approach was applied to reveal profiling of differentially expressed genes and two subtracted cDNA libraries each containing 600 clones were constructed. Then, 114 unigenes were identified from forward SSH library by differential screening and the putative functions of these translational products were classified into 13 categories. With a particular interest in regulatory genes, twenty-one upregulated genes encoding potential regulatory proteins were selected based on the result of reverse transcription-polymerase chain reaction (RT-PCR) analysis. They included nine putative transcription genes, eight putative post-translational regulator genes and four membrane protein genes. The expression patterns of these genes were further analyzed by quantitative RT-PCR at different stages of nodule development. The data presented here offer the first insights into the molecular foundation underlying R. pseudoacacia-M. amorphae symbiosis. A number of regulatory genes screened in the present study revealed a high level of regulatory complexity (transcriptional, post-transcriptional, translational and post-translational) that is likely essential to develop symbiosis. In addition, the possible roles of these genes in black locust nodulation are discussed.

  6. A functional-structural modelling approach to autoregulation of nodulation.

    PubMed

    Han, Liqi; Gresshoff, Peter M; Hanan, Jim

    2011-04-01

    Autoregulation of nodulation is a long-distance shoot-root signalling regulatory system that regulates nodule meristem proliferation in legume plants. However, due to the intricacy and subtleness of the signalling nature in plants, molecular and biochemical details underlying mechanisms of autoregulation of nodulation remain largely unknown. The purpose of this study is to use functional-structural plant modelling to investigate the complexity of this signalling system. There are two major challenges to be met: modelling the 3D architecture of legume roots with nodulation and co-ordinating signalling-developmental processes with various rates. Soybean (Glycine max) was chosen as the target legume. Its root system was observed to capture lateral root branching and nodule distribution patterns. L-studio, a software tool supporting context-sensitive L-system modelling, was used for the construction of the architectural model and integration with the internal signalling. A branching pattern with regular radial angles was found between soybean lateral roots, from which a root mapping method was developed to characterize the laterals. Nodules were mapped based on 'nodulation section' to reveal nodule distribution. A root elongation algorithm was then developed for simulation of root development. Based on the use of standard sub-modules, a synchronization algorithm was developed to co-ordinate multi-rate signalling and developmental processes. The modelling methods developed here not only allow recreation of legume root architecture with lateral branching and nodulation details, but also enable parameterization of internal signalling to produce different regulation results. This provides the basis for using virtual experiments to help in investigating the signalling mechanisms at work.

  7. A nodule-specific gene encoding a subtilisin-like protease is expressed in early stages of actinorhizal nodule development.

    PubMed Central

    Ribeiro, A; Akkermans, A D; van Kammen, A; Bisseling, T; Pawlowski, K

    1995-01-01

    To identify genes specifically expressed during early stages of actinorhizal nodule development, a cDNA library made from poly(A) RNA from root nodules of Alnus glutinosa was screened differentially with nodule and root cDNA, respectively. Seven nodule-enhanced and four nodule-specific cDNA clones were isolated. By using in situ hybridization, two of the nodule-specific cDNAs were shown to be expressed at the highest levels in infected cells before the onset of nitrogen fixation; one of them, ag12 (A. glutinosa), was examined in detail. Sequencing showed that ag12 codes for a serine protease of the subtilisin (EC 3.4.21.14) family. Subtilisins previously appeared to be limited to microorganisms. However, subtilisin-like serine proteases have recently been found in archaebacteria, fungi, and yeasts as well as in mammals; a plant subtilisin has also been sequenced. In yeast and mammals, subtilases are responsible for processing peptide hormones. A homolog of ag12, ara12, was identified in Arabidopsis; it was expressed in all organs, and its expression levels were highest during silique development. Hence, our study shows that subtilases are also involved in both symbiotic and nonsymbiotic processes in plant development. PMID:7647567

  8. A nodule-specific gene encoding a subtilisin-like protease is expressed in early stages of actinorhizal nodule development.

    PubMed

    Ribeiro, A; Akkermans, A D; van Kammen, A; Bisseling, T; Pawlowski, K

    1995-06-01

    To identify genes specifically expressed during early stages of actinorhizal nodule development, a cDNA library made from poly(A) RNA from root nodules of Alnus glutinosa was screened differentially with nodule and root cDNA, respectively. Seven nodule-enhanced and four nodule-specific cDNA clones were isolated. By using in situ hybridization, two of the nodule-specific cDNAs were shown to be expressed at the highest levels in infected cells before the onset of nitrogen fixation; one of them, ag12 (A. glutinosa), was examined in detail. Sequencing showed that ag12 codes for a serine protease of the subtilisin (EC 3.4.21.14) family. Subtilisins previously appeared to be limited to microorganisms. However, subtilisin-like serine proteases have recently been found in archaebacteria, fungi, and yeasts as well as in mammals; a plant subtilisin has also been sequenced. In yeast and mammals, subtilases are responsible for processing peptide hormones. A homolog of ag12, ara12, was identified in Arabidopsis; it was expressed in all organs, and its expression levels were highest during silique development. Hence, our study shows that subtilases are also involved in both symbiotic and nonsymbiotic processes in plant development.

  9. Gibberellins Are Involved in Nodulation of Sesbania rostrata1

    PubMed Central

    Lievens, Sam; Goormachtig, Sofie; Den Herder, Jeroen; Capoen, Ward; Mathis, René; Hedden, Peter; Holsters, Marcelle

    2005-01-01

    Upon submergence, Azorhizobium caulinodans infects the semiaquatic legume Sesbania rostrata via the intercellular crack entry process, resulting in lateral root-based nodules. A gene encoding a gibberellin (GA) 20-oxidase, SrGA20ox1, involved in GA biosynthesis, was transiently up-regulated during lateral root base nodulation. Two SrGA20ox1 expression patterns were identified, one related to intercellular infection and a second observed in nodule meristem descendants. The infection-related expression pattern depended on bacterially produced nodulation (Nod) factors. Pharmacological studies demonstrated that GAs were involved in infection pocket and infection thread formation, two Nod factor-dependent events that initiate lateral root base nodulation, and that they were also needed for nodule primordium development. Moreover, GAs inhibited the root hair curling process. These results show that GAs are Nod factor downstream signals for nodulation in hydroponic growth. PMID:16258018

  10. How legumes recognize rhizobia.

    PubMed

    Via, Virginia Dalla; Zanetti, María Eugenia; Blanco, Flavio

    2016-01-01

    Legume plants have developed the capacity to establish symbiotic interactions with soil bacteria (known as rhizobia) that can convert N2 to molecular forms that are incorporated into the plant metabolism. The first step of this relationship is the recognition of bacteria by the plant, which allows to distinguish potentially harmful species from symbiotic partners. The main molecular determinant of this symbiotic interaction is the Nod Factor, a diffusible lipochitooligosaccharide molecule produced by rhizobia and perceived by LysM receptor kinases; however, other important molecules involved in the specific recognition have emerged over the years. Secreted exopolysaccharides and the lipopolysaccharides present in the bacterial cell wall have been proposed to act as signaling molecules, triggering the expression of specific genes related to the symbiotic process. In this review we will briefly discuss how transcriptomic analysis are helping to understand how multiple signaling pathways, triggered by the perception of different molecules produced by rhizobia, control the genetic programs of root nodule organogenesis and bacterial infection. This knowledge can help to understand how legumes have evolved to recognize and establish complex ecological relationships with particular species and strains of rhizobia, adjusting gene expression in response to identity determinants of bacteria.

  11. Specificity in Legume-Rhizobia Symbioses.

    PubMed

    Andrews, Mitchell; Andrews, Morag E

    2017-03-26

    Most species in the Leguminosae (legume family) can fix atmospheric nitrogen (N₂) via symbiotic bacteria (rhizobia) in root nodules. Here, the literature on legume-rhizobia symbioses in field soils was reviewed and genotypically characterised rhizobia related to the taxonomy of the legumes from which they were isolated. The Leguminosae was divided into three sub-families, the Caesalpinioideae, Mimosoideae and Papilionoideae. Bradyrhizobium spp. were the exclusive rhizobial symbionts of species in the Caesalpinioideae, but data are limited. Generally, a range of rhizobia genera nodulated legume species across the two Mimosoideae tribes Ingeae and Mimoseae, but Mimosa spp. show specificity towards Burkholderia in central and southern Brazil, Rhizobium/Ensifer in central Mexico and Cupriavidus in southern Uruguay. These specific symbioses are likely to be at least in part related to the relative occurrence of the potential symbionts in soils of the different regions. Generally, Papilionoideae species were promiscuous in relation to rhizobial symbionts, but specificity for rhizobial genus appears to hold at the tribe level for the Fabeae (Rhizobium), the genus level for Cytisus (Bradyrhizobium), Lupinus (Bradyrhizobium) and the New Zealand native Sophora spp. (Mesorhizobium) and species level for Cicer arietinum (Mesorhizobium), Listia bainesii (Methylobacterium) and Listia angolensis (Microvirga). Specificity for rhizobial species/symbiovar appears to hold for Galega officinalis (Neorhizobium galegeae sv. officinalis), Galega orientalis (Neorhizobium galegeae sv. orientalis), Hedysarum coronarium (Rhizobium sullae), Medicago laciniata (Ensifer meliloti sv. medicaginis), Medicago rigiduloides (Ensifer meliloti sv. rigiduloides) and Trifolium ambiguum (Rhizobium leguminosarum sv. trifolii). Lateral gene transfer of specific symbiosis genes within rhizobial genera is an important mechanism allowing legumes to form symbioses with rhizobia adapted to particular soils

  12. Specificity in Legume-Rhizobia Symbioses

    PubMed Central

    Andrews, Mitchell; Andrews, Morag E.

    2017-01-01

    Most species in the Leguminosae (legume family) can fix atmospheric nitrogen (N2) via symbiotic bacteria (rhizobia) in root nodules. Here, the literature on legume-rhizobia symbioses in field soils was reviewed and genotypically characterised rhizobia related to the taxonomy of the legumes from which they were isolated. The Leguminosae was divided into three sub-families, the Caesalpinioideae, Mimosoideae and Papilionoideae. Bradyrhizobium spp. were the exclusive rhizobial symbionts of species in the Caesalpinioideae, but data are limited. Generally, a range of rhizobia genera nodulated legume species across the two Mimosoideae tribes Ingeae and Mimoseae, but Mimosa spp. show specificity towards Burkholderia in central and southern Brazil, Rhizobium/Ensifer in central Mexico and Cupriavidus in southern Uruguay. These specific symbioses are likely to be at least in part related to the relative occurrence of the potential symbionts in soils of the different regions. Generally, Papilionoideae species were promiscuous in relation to rhizobial symbionts, but specificity for rhizobial genus appears to hold at the tribe level for the Fabeae (Rhizobium), the genus level for Cytisus (Bradyrhizobium), Lupinus (Bradyrhizobium) and the New Zealand native Sophora spp. (Mesorhizobium) and species level for Cicer arietinum (Mesorhizobium), Listia bainesii (Methylobacterium) and Listia angolensis (Microvirga). Specificity for rhizobial species/symbiovar appears to hold for Galega officinalis (Neorhizobium galegeae sv. officinalis), Galega orientalis (Neorhizobium galegeae sv. orientalis), Hedysarum coronarium (Rhizobium sullae), Medicago laciniata (Ensifer meliloti sv. medicaginis), Medicago rigiduloides (Ensifer meliloti sv. rigiduloides) and Trifolium ambiguum (Rhizobium leguminosarum sv. trifolii). Lateral gene transfer of specific symbiosis genes within rhizobial genera is an important mechanism allowing legumes to form symbioses with rhizobia adapted to particular soils

  13. A JAZ Protein in Astragalus sinicus Interacts with a Leghemoglobin through the TIFY Domain and Is Involved in Nodule Development and Nitrogen Fixation

    PubMed Central

    Li, Yixing; Xu, Meng; Wang, Ning; Li, Youguo

    2015-01-01

    Leghemoglobins (Lbs) play an important role in legumes-rhizobia symbiosis. Lbs bind O2 and protect nitrogenase activity from damage by O2 in nodules, therefore, they are regarded as a marker of active nitrogen fixation in nodules. Additionally, Lbs are involved in the nitric oxide (NO) signaling pathway, acting as a NO scavenger during nodule development and nitrogen fixation. However, regulators responsible for Lb expression and modulation of Lb activity have not been characterized. In our previous work, a Jasmonate-Zim-domain (JAZ) protein interacting with a Lb (AsB2510) in Astragalus sinicus was identified and designated AsJAZ1. In this study, the interaction between AsJAZ1 and AsB2510 was verified using a yeast two-hybrid system and in vitro Glutathione S-transferase (GST) pull-down assays, resulting in identification of the interaction domain as a TIFY (previously known as zinc-finger protein expressed in inflorescence meristem, ZIM) domain. TIFY domain is named after the most conserved amino acids within the domain. Bimolecular fluorescence complementation (BiFC) was used to confirm the interaction between AsJAZ1 and AsB2510 in tobacco cells, demonstrating that AsJAZ1-AsB2510 interaction was localized to the cell membrane and cytoplasm. Furthermore, the expression patterns and the symbiotic phenotypes of AsJAZ1 were investigated. Knockdown of AsJAZ1 expression via RNA interference led to decreased number of nodules, abnormal development of bacteroids, accumulation of poly-x-hydroxybutyrate (PHB) and loss of nitrogenase activity. Taken together, our results suggest that AsJAZ1 interacts with AsB2510 and participates in nodule development and nitrogen fixation. Our results provide novel insights into the functions of Lbs or JAZ proteins during legume-rhizobia symbiosis. PMID:26460857

  14. A JAZ Protein in Astragalus sinicus Interacts with a Leghemoglobin through the TIFY Domain and Is Involved in Nodule Development and Nitrogen Fixation.

    PubMed

    Li, Yixing; Xu, Meng; Wang, Ning; Li, Youguo

    2015-01-01

    Leghemoglobins (Lbs) play an important role in legumes-rhizobia symbiosis. Lbs bind O2 and protect nitrogenase activity from damage by O2 in nodules, therefore, they are regarded as a marker of active nitrogen fixation in nodules. Additionally, Lbs are involved in the nitric oxide (NO) signaling pathway, acting as a NO scavenger during nodule development and nitrogen fixation. However, regulators responsible for Lb expression and modulation of Lb activity have not been characterized. In our previous work, a Jasmonate-Zim-domain (JAZ) protein interacting with a Lb (AsB2510) in Astragalus sinicus was identified and designated AsJAZ1. In this study, the interaction between AsJAZ1 and AsB2510 was verified using a yeast two-hybrid system and in vitro Glutathione S-transferase (GST) pull-down assays, resulting in identification of the interaction domain as a TIFY (previously known as zinc-finger protein expressed in inflorescence meristem, ZIM) domain. TIFY domain is named after the most conserved amino acids within the domain. Bimolecular fluorescence complementation (BiFC) was used to confirm the interaction between AsJAZ1 and AsB2510 in tobacco cells, demonstrating that AsJAZ1-AsB2510 interaction was localized to the cell membrane and cytoplasm. Furthermore, the expression patterns and the symbiotic phenotypes of AsJAZ1 were investigated. Knockdown of AsJAZ1 expression via RNA interference led to decreased number of nodules, abnormal development of bacteroids, accumulation of poly-x-hydroxybutyrate (PHB) and loss of nitrogenase activity. Taken together, our results suggest that AsJAZ1 interacts with AsB2510 and participates in nodule development and nitrogen fixation. Our results provide novel insights into the functions of Lbs or JAZ proteins during legume-rhizobia symbiosis.

  15. High-quality permanent draft genome sequence of Ensifer sp. PC2, isolated from a nitrogen-fixing root nodule of the legume tree (Khejri) native to the Thar Desert of India

    DOE PAGES

    Gehlot, Hukam Singh; Ardley, Julie; Tak, Nisha; ...

    2016-06-23

    Ensifer sp. PC2 is an aerobic, motile, Gram-negative, non-spore-forming rod that was isolated from a nitrogen-fixing nodule of the tree legume P. cineraria (L.) Druce (Khejri), which is a keystone species that grows in arid and semi-arid regions of the Indian Thar desert. Strain PC2 exists as a dominant saprophyte in alkaline soils of Western Rajasthan. It is fast growing, well-adapted to arid conditions and is able to form an effective symbiosis with several annual crop legumes as well as species of mimosoid trees and shrubs. Here we describe the features of Ensifer sp. PC2, together with genome sequence informationmore » and its annotation. The 8,458,965 bp high-quality permanent draft genome is arranged into 171 scaffolds of 171 contigs containing 8,344 protein-coding genes and 139 RNA-only encoding genes, and is one of the rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project proposal.« less

  16. High-quality permanent draft genome sequence of Ensifer sp. PC2, isolated from a nitrogen-fixing root nodule of the legume tree (Khejri) native to the Thar Desert of India

    SciTech Connect

    Gehlot, Hukam Singh; Ardley, Julie; Tak, Nisha; Tian, Rui; Poonar, Neetu; Meghwal, Raju R.; Rathi, Sonam; Tiwari, Ravi; Adnawani, Wan; Seshadri, Rekha; Reddy, T. B. K.; Pati, Amrita; Woyke, Tanja; Pillay, Manoj; Markowitz, Victor; Baeshen, Mohammed N.; Al-Hejin, Ahmed M.; Ivanova, Natalia; Kyrpides, Nikos; Reeve, Wayne

    2016-06-23

    Ensifer sp. PC2 is an aerobic, motile, Gram-negative, non-spore-forming rod that was isolated from a nitrogen-fixing nodule of the tree legume P. cineraria (L.) Druce (Khejri), which is a keystone species that grows in arid and semi-arid regions of the Indian Thar desert. Strain PC2 exists as a dominant saprophyte in alkaline soils of Western Rajasthan. It is fast growing, well-adapted to arid conditions and is able to form an effective symbiosis with several annual crop legumes as well as species of mimosoid trees and shrubs. Here we describe the features of Ensifer sp. PC2, together with genome sequence information and its annotation. The 8,458,965 bp high-quality permanent draft genome is arranged into 171 scaffolds of 171 contigs containing 8,344 protein-coding genes and 139 RNA-only encoding genes, and is one of the rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project proposal.

  17. The integral membrane protein SEN1 is required for symbiotic nitrogen fixation in Lotus japonicus nodules.

    PubMed

    Hakoyama, Tsuneo; Niimi, Kaori; Yamamoto, Takeshi; Isobe, Sawa; Sato, Shusei; Nakamura, Yasukazu; Tabata, Satoshi; Kumagai, Hirotaka; Umehara, Yosuke; Brossuleit, Katja; Petersen, Thomas R; Sandal, Niels; Stougaard, Jens; Udvardi, Michael K; Tamaoki, Masanori; Kawaguchi, Masayoshi; Kouchi, Hiroshi; Suganuma, Norio

    2012-01-01

    Legume plants establish a symbiotic association with bacteria called rhizobia, resulting in the formation of nitrogen-fixing root nodules. A Lotus japonicus symbiotic mutant, sen1, forms nodules that are infected by rhizobia but that do not fix nitrogen. Here, we report molecular identification of the causal gene, SEN1, by map-based cloning. The SEN1 gene encodes an integral membrane protein homologous to Glycine max nodulin-21, and also to CCC1, a vacuolar iron/manganese transporter of Saccharomyces cerevisiae, and VIT1, a vacuolar iron transporter of Arabidopsis thaliana. Expression of the SEN1 gene was detected exclusively in nodule-infected cells and increased during nodule development. Nif gene expression as well as the presence of nitrogenase proteins was detected in rhizobia from sen1 nodules, although the levels of expression were low compared with those from wild-type nodules. Microscopic observations revealed that symbiosome and/or bacteroid differentiation are impaired in the sen1 nodules even at a very early stage of nodule development. Phylogenetic analysis indicated that SEN1 belongs to a protein clade specific to legumes. These results indicate that SEN1 is essential for nitrogen fixation activity and symbiosome/bacteroid differentiation in legume nodules.

  18. The MicroRNA390/TAS3 Pathway Mediates Symbiotic Nodulation and Lateral Root Growth.

    PubMed

    Hobecker, Karen Vanesa; Reynoso, Mauricio Alberto; Bustos-Sanmamed, Pilar; Wen, Jiangqi; Mysore, Kirankumar S; Crespi, Martín; Blanco, Flavio Antonio; Zanetti, María Eugenia

    2017-08-01

    Legume roots form two types of postembryonic organs, lateral roots and symbiotic nodules. Nodule formation is the result of the interaction of legumes with rhizobia and requires the mitotic activation and differentiation of root cells as well as an independent, but coordinated, program that allows infection by rhizobia. MicroRNA390 (miR390) is an evolutionarily conserved microRNA that targets the Trans-Acting Short Interference RNA3 (TAS3) transcript. Cleavage of TAS3 by ARGONAUTE7 results in the production of trans-acting small interference RNAs, which target mRNAs encoding AUXIN RESPONSE FACTOR2 (ARF2), ARF3, and ARF4. Here, we show that activation of the miR390/TAS3 regulatory module by overexpression of miR390 in Medicago truncatula promotes lateral root growth but prevents nodule organogenesis, rhizobial infection, and the induction of two key nodulation genes, Nodulation Signaling Pathway1 (NSP1) and NSP2 Accordingly, inactivation of the miR390/TAS3 module, either by expression of a miR390 target mimicry construct or mutations in ARGONAUTE7, enhances nodulation and rhizobial infection, alters the spatial distribution of the nodules, and increases the percentage of nodules with multiple meristems. Our results revealed a key role of the miR390/TAS3 pathway in legumes as a modulator of lateral root organs, playing opposite roles in lateral root and nodule development. © 2017 American Society of Plant Biologists. All Rights Reserved.

  19. MicroRNA167-Directed Regulation of the Auxin Response Factors GmARF8a and GmARF8b Is Required for Soybean Nodulation and Lateral Root Development.

    PubMed

    Wang, Youning; Li, Kexue; Chen, Liang; Zou, Yanmin; Liu, Haipei; Tian, Yinping; Li, Dongxiao; Wang, Rui; Zhao, Fang; Ferguson, Brett J; Gresshoff, Peter M; Li, Xia

    2015-07-01

    Legume root nodules convert atmospheric nitrogen gas into ammonium through symbiosis with a prokaryotic microsymbiont broadly called rhizobia. Auxin signaling is required for determinant nodule development; however, the molecular mechanism of auxin-mediated nodule formation remains largely unknown. Here, we show in soybean (Glycine max) that the microRNA miR167 acts as a positive regulator of lateral root organs, namely nodules and lateral roots. miR167c expression was up-regulated in the vasculature, pericycle, and cortex of soybean roots following inoculation with Bradyrhizobium japonicum strain USDA110 (the microsymbiont). It was found to positively regulate nodule numbers directly by repressing the target genes GmARF8a and GmARF8b (homologous genes of Arabidopsis [Arabidopsis thaliana] AtARF8 that encode auxin response factors). Moreover, the expression of miR167 and its targets was up- and down-regulated by auxin, respectively. The miR167-GmARF8 module also positively regulated nodulation efficiency under low microsymbiont density, a condition often associated with environmental stress. The regulatory role of miR167 on nodule initiation was dependent on the Nod factor receptor GmNFR1α, and it acts upstream of the nodulation-associated genes nodule inception, nodulation signaling pathway1, early nodulin40-1, NF-YA1 (previously known as HAEM activator protein2-1), and NF-YA2. miR167 also promoted lateral root numbers. Collectively, our findings establish a key role for the miR167-GmARF8 module in auxin-mediated nodule and lateral root formation in soybean. © 2015 American Society of Plant Biologists. All Rights Reserved.

  20. MicroRNA167-Directed Regulation of the Auxin Response Factors GmARF8a and GmARF8b Is Required for Soybean Nodulation and Lateral Root Development1[OPEN

    PubMed Central

    Wang, Youning; Li, Kexue; Chen, Liang; Zou, Yanmin; Tian, Yinping; Li, Dongxiao; Wang, Rui; Zhao, Fang; Ferguson, Brett J.; Gresshoff, Peter M.

    2015-01-01

    Legume root nodules convert atmospheric nitrogen gas into ammonium through symbiosis with a prokaryotic microsymbiont broadly called rhizobia. Auxin signaling is required for determinant nodule development; however, the molecular mechanism of auxin-mediated nodule formation remains largely unknown. Here, we show in soybean (Glycine max) that the microRNA miR167 acts as a positive regulator of lateral root organs, namely nodules and lateral roots. miR167c expression was up-regulated in the vasculature, pericycle, and cortex of soybean roots following inoculation with Bradyrhizobium japonicum strain USDA110 (the microsymbiont). It was found to positively regulate nodule numbers directly by repressing the target genes GmARF8a and GmARF8b (homologous genes of Arabidopsis [Arabidopsis thaliana] AtARF8 that encode auxin response factors). Moreover, the expression of miR167 and its targets was up- and down-regulated by auxin, respectively. The miR167-GmARF8 module also positively regulated nodulation efficiency under low microsymbiont density, a condition often associated with environmental stress. The regulatory role of miR167 on nodule initiation was dependent on the Nod factor receptor GmNFR1α, and it acts upstream of the nodulation-associated genes NODULE INCEPTION, NODULATION SIGNALING PATHWAY1, EARLY NODULIN40-1, NF-YA1 (previously known as HAEM ACTIVATOR PROTEIN2-1), and NF-YA2. miR167 also promoted lateral root numbers. Collectively, our findings establish a key role for the miR167-GmARF8 module in auxin-mediated nodule and lateral root formation in soybean. PMID:25941314

  1. Shoot-derived cytokinins systemically regulate root nodulation.

    PubMed

    Sasaki, Takema; Suzaki, Takuya; Soyano, Takashi; Kojima, Mikiko; Sakakibara, Hitoshi; Kawaguchi, Masayoshi

    2014-09-19

    Legumes establish symbiotic associations with nitrogen-fixing bacteria (rhizobia) in root nodules to obtain nitrogen. Legumes control nodule number through long-distance communication between roots and shoots, maintaining the proper symbiotic balance. Rhizobial infection triggers the production of mobile CLE-RS1/2 peptides in Lotus japonicus roots; the perception of the signal by receptor kinase HAR1 in shoots presumably induces the production of an unidentified shoot-derived inhibitor (SDI) that translocates to roots and blocks further nodule development. Here we show that, CLE-RS1/2-HAR1 signalling activates the production of shoot-derived cytokinins, which have an SDI-like capacity to systemically suppress nodulation. In addition, we show that LjIPT3 is involved in nodulation-related cytokinin production in shoots. The expression of LjIPT3 is activated in an HAR1-dependent manner. We further demonstrate shoot-to-root long-distance transport of cytokinin in L. japonicus seedlings. These findings add essential components to our understanding of how legumes control nodulation to balance nutritional requirements and energy status.

  2. Development and comparison of projection and image space 3D nodule insertion techniques

    NASA Astrophysics Data System (ADS)

    Robins, Marthony; Solomon, Justin; Sahbaee, Pooyan; Samei, Ehsan

    2016-04-01

    This study aimed to develop and compare two methods of inserting computerized virtual lesions into CT datasets. 24 physical (synthetic) nodules of three sizes and four morphologies were inserted into an anthropomorphic chest phantom (LUNGMAN, KYOTO KAGAKU). The phantom was scanned (Somatom Definition Flash, Siemens Healthcare) with and without nodules present, and images were reconstructed with filtered back projection and iterative reconstruction (SAFIRE) at 0.6 mm slice thickness using a standard thoracic CT protocol at multiple dose settings. Virtual 3D CAD models based on the physical nodules were virtually inserted (accounting for the system MTF) into the nodule-free CT data using two techniques. These techniques include projection-based and image-based insertion. Nodule volumes were estimated using a commercial segmentation tool (iNtuition, TeraRecon, Inc.). Differences were tested using paired t-tests and R2 goodness of fit between the virtually and physically inserted nodules. Both insertion techniques resulted in nodule volumes very similar to the real nodules (<3% difference) and in most cases the differences were not statistically significant. Also, R2 values were all <0.97 for both insertion techniques. These data imply that these techniques can confidently be used as a means of inserting virtual nodules in CT datasets. These techniques can be instrumental in building hybrid CT datasets composed of patient images with virtually inserted nodules.

  3. The proteome of seed development in the model legume Lotus japonicus.

    PubMed

    Dam, Svend; Laursen, Brian S; Ornfelt, Jane H; Jochimsen, Bjarne; Staerfeldt, Hans Henrik; Friis, Carsten; Nielsen, Kasper; Goffard, Nicolas; Besenbacher, Søren; Krusell, Lene; Sato, Shusei; Tabata, Satoshi; Thøgersen, Ida B; Enghild, Jan J; Stougaard, Jens

    2009-03-01

    We have characterized the development of seeds in the model legume Lotus japonicus. Like soybean (Glycine max) and pea (Pisum sativum), Lotus develops straight seed pods and each pod contains approximately 20 seeds that reach maturity within 40 days. Histological sections show the characteristic three developmental phases of legume seeds and the presence of embryo, endosperm, and seed coat in desiccated seeds. Furthermore, protein, oil, starch, phytic acid, and ash contents were determined, and this indicates that the composition of mature Lotus seed is more similar to soybean than to pea. In a first attempt to determine the seed proteome, both a two-dimensional polyacrylamide gel electrophoresis approach and a gel-based liquid chromatography-mass spectrometry approach were used. Globulins were analyzed by two-dimensional polyacrylamide gel electrophoresis, and five legumins, LLP1 to LLP5, and two convicilins, LCP1 and LCP2, were identified by matrix-assisted laser desorption ionization quadrupole/time-of-flight mass spectrometry. For two distinct developmental phases, seed filling and desiccation, a gel-based liquid chromatography-mass spectrometry approach was used, and 665 and 181 unique proteins corresponding to gene accession numbers were identified for the two phases, respectively. All of the proteome data, including the experimental data and mass spectrometry spectra peaks, were collected in a database that is available to the scientific community via a Web interface (http://www.cbs.dtu.dk/cgi-bin/lotus/db.cgi). This database establishes the basis for relating physiology, biochemistry, and regulation of seed development in Lotus. Together with a new Web interface (http://bioinfoserver.rsbs.anu.edu.au/utils/PathExpress4legumes/) collecting all protein identifications for Lotus, Medicago, and soybean seed proteomes, this database is a valuable resource for comparative seed proteomics and pathway analysis within and beyond the legume family.

  4. Growth and Survival of Mesorhizobium loti Inside Acanthamoeba Enhanced Its Ability to Develop More Nodules on Lotus corniculatus.

    PubMed

    Karaś, Magdalena A; Turska-Szewczuk, Anna; Trapska, Dominika; Urbanik-Sypniewska, Teresa

    2015-08-01

    The importance of protozoa as environmental reservoirs of pathogens is well recognized, while their impact on survival and symbiotic properties of rhizobia has not been explored. The possible survival of free-living rhizobia inside amoebae could influence bacterial abundance in the rhizosphere of legume plants and the nodulation competitiveness of microsymbionts. Two well-characterized strains of Mesorhizobium: Mesorhizobium loti NZP2213 and Mesorhizobium huakuii symbiovar loti MAFF303099 were assayed for their growth ability within the Neff strain of Acanthamoeba castellanii. Although the association ability and the initial uptake rate of both strains were similar, recovery of viable M. huakuii MAFF303099 after 4 h postinfection decreased markedly and that of M. loti NZP2213 increased. The latter strain was also able to survive prolonged co-incubation within amoebae and to self-release from the amoeba cell. The temperature 28 °C and PBS were established as optimal for the uptake of Mesorhizobium by amoebae. The internalization of mesorhizobia was mediated by the mannose-dependent receptor. M. loti NZP2213 bacteria released from amoebae developed 1.5 times more nodules on Lotus corniculatus than bacteria cultivated in an amoebae-free medium.

  5. Characterisation of the legume SERK-NIK gene superfamily including splice variants: Implications for development and defence

    PubMed Central

    2011-01-01

    Background SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) genes are part of the regulation of diverse signalling events in plants. Current evidence shows SERK proteins function both in developmental and defence signalling pathways, which occur in response to both peptide and steroid ligands. SERKs are generally present as small gene families in plants, with five SERK genes in Arabidopsis. Knowledge gained primarily through work on Arabidopsis SERKs indicates that these proteins probably interact with a wide range of other receptor kinases and form a fundamental part of many essential signalling pathways. The SERK1 gene of the model legume, Medicago truncatula functions in somatic and zygotic embryogenesis, and during many phases of plant development, including nodule and lateral root formation. However, other SERK genes in M. truncatula and other legumes are largely unidentified and their functions unknown. Results To aid the understanding of signalling pathways in M. truncatula, we have identified and annotated the SERK genes in this species. Using degenerate PCR and database mining, eight more SERK-like genes have been identified and these have been shown to be expressed. The amplification and sequencing of several different PCR products from one of these genes is consistent with the presence of splice variants. Four of the eight additional genes identified are upregulated in cultured leaf tissue grown on embryogenic medium. The sequence information obtained from M. truncatula was used to identify SERK family genes in the recently sequenced soybean (Glycine max) genome. Conclusions A total of nine SERK or SERK-like genes have been identified in M. truncatula and potentially 17 in soybean. Five M. truncatula SERK genes arose from duplication events not evident in soybean and Lotus. The presence of splice variants has not been previously reported in a SERK gene. Upregulation of four newly identified SERK genes (in addition to the previously described MtSERK1) in

  6. The role of the testa during development and in establishment of dormancy of the legume seed

    PubMed Central

    Smýkal, Petr; Vernoud, Vanessa; Blair, Matthew W.; Soukup, Aleš; Thompson, Richard D.

    2014-01-01

    Timing of seed germination is one of the key steps in plant life cycles. It determines the beginning of plant growth in natural or agricultural ecosystems. In the wild, many seeds exhibit dormancy and will only germinate after exposure to certain environmental conditions. In contrast, crop seeds germinate as soon as they are imbibed usually at planting time. These domestication-triggered changes represent adaptations to cultivation and human harvesting. Germination is one of the common sets of traits recorded in different crops and termed the “domestication syndrome.” Moreover, legume seed imbibition has a crucial role in cooking properties. Different seed dormancy classes exist among plant species. Physical dormancy (often called hardseededness), as found in legumes, involves the development of a water-impermeable seed coat, caused by the presence of phenolics- and suberin-impregnated layers of palisade cells. The dormancy release mechanism primarily involves seed responses to temperature changes in the habitat, resulting in testa permeability to water. The underlying genetic controls in legumes have not been identified yet. However, positive correlation was shown between phenolics content (e.g., pigmentation), the requirement for oxidation and the activity of catechol oxidase in relation to pea seed dormancy, while epicatechin levels showed a significant positive correlation with soybean hardseededness. myeloblastosis family of transcription factors, WD40 proteins and enzymes of the anthocyanin biosynthesis pathway were involved in seed testa color in soybean, pea and Medicago, but were not tested directly in relation to seed dormancy. These phenolic compounds play important roles in defense against pathogens, as well as affecting the nutritional quality of products, and because of their health benefits, they are of industrial and medicinal interest. In this review, we discuss the role of the testa in mediating legume seed germination, with a focus on

  7. The role of the testa during development and in establishment of dormancy of the legume seed.

    PubMed

    Smýkal, Petr; Vernoud, Vanessa; Blair, Matthew W; Soukup, Aleš; Thompson, Richard D

    2014-01-01

    Timing of seed germination is one of the key steps in plant life cycles. It determines the beginning of plant growth in natural or agricultural ecosystems. In the wild, many seeds exhibit dormancy and will only germinate after exposure to certain environmental conditions. In contrast, crop seeds germinate as soon as they are imbibed usually at planting time. These domestication-triggered changes represent adaptations to cultivation and human harvesting. Germination is one of the common sets of traits recorded in different crops and termed the "domestication syndrome." Moreover, legume seed imbibition has a crucial role in cooking properties. Different seed dormancy classes exist among plant species. Physical dormancy (often called hardseededness), as found in legumes, involves the development of a water-impermeable seed coat, caused by the presence of phenolics- and suberin-impregnated layers of palisade cells. The dormancy release mechanism primarily involves seed responses to temperature changes in the habitat, resulting in testa permeability to water. The underlying genetic controls in legumes have not been identified yet. However, positive correlation was shown between phenolics content (e.g., pigmentation), the requirement for oxidation and the activity of catechol oxidase in relation to pea seed dormancy, while epicatechin levels showed a significant positive correlation with soybean hardseededness. myeloblastosis family of transcription factors, WD40 proteins and enzymes of the anthocyanin biosynthesis pathway were involved in seed testa color in soybean, pea and Medicago, but were not tested directly in relation to seed dormancy. These phenolic compounds play important roles in defense against pathogens, as well as affecting the nutritional quality of products, and because of their health benefits, they are of industrial and medicinal interest. In this review, we discuss the role of the testa in mediating legume seed germination, with a focus on structural

  8. The lipopolysaccharide lipid-a long chain fatty acid is important for rhizobium leguminosarum growth and stress adaptation in free-living and nodule environments

    USDA-ARS?s Scientific Manuscript database

    Rhizobium bacteria live in soil and plant environments, are capable of inducing symbiotic nodules on legumes, invade these nodules, and develop into bacteroids that fix atmospheric nitrogen into ammonium. Lipopolysaccharide (LPS) is anchored in the bacterial outer membrane through a specialized lipi...

  9. Systemic regulation of soybean nodulation by acidic growth conditions.

    PubMed

    Lin, Meng-Han; Gresshoff, Peter M; Ferguson, Brett J

    2012-12-01

    Mechanisms inhibiting legume nodulation by low soil pH, although highly prevalent and economically significant, are poorly understood. We addressed this in soybean (Glycine max) using a combination of physiological and genetic approaches. Split-root and grafting studies using an autoregulation-of-nodulation-deficient mutant line, altered in the autoregulation-of-nodulation receptor kinase GmNARK, determined that a systemic, shoot-controlled, and GmNARK-dependent mechanism was critical for facilitating the inhibitory effect. Acid inhibition was independent of aluminum ion concentration and occurred early in nodule development, between 12 and 96 h post inoculation with Bradyrhizobium japonicum. Biological effects were confirmed by measuring transcript numbers of known early nodulation genes. Transcripts decreased on both sides of split-root systems, where only one side was subjected to low-pH conditions. Our findings enhance the present understanding of the innate mechanisms regulating legume nodulation control under acidic conditions, which could benefit future attempts in agriculture to improve nodule development and biological nitrogen fixation in acid-stressed soils.

  10. Compound Leaf Development and Evolution in the Legumes[W

    PubMed Central

    Champagne, Connie E.M.; Goliber, Thomas E.; Wojciechowski, Martin F.; Mei, Raymond W.; Townsley, Brad T.; Wang, Kan; Paz, Margie M.; Geeta, R.; Sinha, Neelima R.

    2007-01-01

    Across vascular plants, Class 1 KNOTTED1-like (KNOX1) genes appear to play a critical role in the development of compound leaves. An exception to this trend is found in the Fabaceae, where pea (Pisum sativum) uses UNIFOLIATA, an ortholog of the floral regulators FLORICAULA (FLO) and LEAFY (LFY), in place of KNOX1 genes to regulate compound leaf development. To assess the phylogenetic distribution of KNOX1-independent compound leaf development, a survey of KNOX1 protein expression across the Fabaceae was undertaken. The majority of compound-leafed Fabaceae have expression of KNOX1 proteins associated with developing compound leaves. However, in a large subclade of the Fabaceae, the inverted repeat–lacking clade (IRLC), of which pea is a member, KNOX1 expression is not associated with compound leaves. These data suggest that the FLO/LFY gene may function in place of KNOX1 genes in generating compound leaves throughout the IRLC. The contribution of FLO/LFY to leaf complexity in a member of the Fabaceae outside of the IRLC was examined by reducing expression of FLO/LFY orthologs in transgenic soybean (Glycine max). Transgenic plants with reduced FLO/LFY expression showed only slight reductions in leaflet number. Overexpression of a KNOX1 gene in alfalfa (Medicago sativa), a member of the IRLC, resulted in an increase in leaflet number. This implies that KNOX1 targets, which promote compound leaf development, are present in alfalfa and are still sensitive to KNOX1 regulation. These data suggest that KNOX1 genes and the FLO/LFY gene may have played partially overlapping roles in compound leaf development in ancestral Fabaceae but that the FLO/LFY gene took over this role in the IRLC. PMID:17993625

  11. Nodulation of Mimosa spp. by the beta-proteobacterium Ralstonia taiwanensis.

    PubMed

    Chen, Wen-Ming; James, Euan K; Prescott, Alan R; Kierans, Martin; Sprent, Janet I

    2003-12-01

    Several beta-proteobacteria have been isolated from legume root nodules and some of these are thought to be capable of nodulating and fixing N2. However, in no case has there been detailed studies confirming that they are the active symbionts. Here, Ralstonia taiwanensis LMG19424, which was originally isolated from Mimosa pudica nodules, was transformed to carry the green fluorescent protein (gfp) reporter gene before being used to inoculate axenically-grown seedlings of M. pudica and M. diplotricha. Plants were harvested at various intervals for 56 days after inoculation, then examined for evidence of infection and nodule formation. Nodulation of both Mimosa spp. was abundant, and acetylene reduction assays confirmed that nodules had nitrogenase activity. Confocal laser scanning microscopy (CLSM) showed that fresh M. pudica nodules with nitrogenase activity had infected cells containing bacteroids expressing gfp. In parallel, fixed and embedded nodules from both Mimosa spp. were sectioned for light and electron microscopy, followed by immunogold labeling with antibodies raised against gfp and nitrogenase Fe (nifH) protein. Significant immunolabeling with these antibodies confirmed that R. taiwanensis LMG19424 is an effective N2-fixing symbiont of Mimosa spp. Both species were infected via root hairs and, in all respects, the nodule ontogeny and development was similar to that described for other mimosoid legumes. The nodules were indeterminate with a persistent meristem, an invasion zone containing host cells being invaded via prominent infection threads, and an N2-fixing zone with infected cells containing membrane-bound symbiosomes.

  12. The MicroRNA390/TAS3 Pathway Mediates Symbiotic Nodulation and Lateral Root Growth1[OPEN

    PubMed Central

    Bustos-Sanmamed, Pilar; Mysore, Kirankumar S.

    2017-01-01

    Legume roots form two types of postembryonic organs, lateral roots and symbiotic nodules. Nodule formation is the result of the interaction of legumes with rhizobia and requires the mitotic activation and differentiation of root cells as well as an independent, but coordinated, program that allows infection by rhizobia. MicroRNA390 (miR390) is an evolutionarily conserved microRNA that targets the Trans-Acting Short Interference RNA3 (TAS3) transcript. Cleavage of TAS3 by ARGONAUTE7 results in the production of trans-acting small interference RNAs, which target mRNAs encoding AUXIN RESPONSE FACTOR2 (ARF2), ARF3, and ARF4. Here, we show that activation of the miR390/TAS3 regulatory module by overexpression of miR390 in Medicago truncatula promotes lateral root growth but prevents nodule organogenesis, rhizobial infection, and the induction of two key nodulation genes, Nodulation Signaling Pathway1 (NSP1) and NSP2. Accordingly, inactivation of the miR390/TAS3 module, either by expression of a miR390 target mimicry construct or mutations in ARGONAUTE7, enhances nodulation and rhizobial infection, alters the spatial distribution of the nodules, and increases the percentage of nodules with multiple meristems. Our results revealed a key role of the miR390/TAS3 pathway in legumes as a modulator of lateral root organs, playing opposite roles in lateral root and nodule development. PMID:28663332

  13. Differential effectiveness of novel and old legume-rhizobia mutualisms: implications for invasion by exotic legumes.

    PubMed

    Rodríguez-Echeverría, Susana; Fajardo, Susana; Ruiz-Díez, Beatriz; Fernández-Pascual, Mercedes

    2012-09-01

    The degree of specialization in the legume-rhizobium mutualism and the variation in the response to different potential symbionts are crucial factors for understanding the process of invasion by exotic legumes and the consequences for the native resident plants and bacteria. The enhanced novel mutualism hypothesis predicts that exotic invasive legumes would take advantage of native rhizobia present in the invaded soils. However, recent studies have shown that exotic legumes might become invasive by using exotic introduced microsymbionts, and that they could be a source of exotic bacteria for native legumes. To unravel the role of novel and old symbioses in the progress of invasion, nodulation and symbiotic effectiveness were analyzed for exotic invasive plants and native co-occurring legumes in a Mediterranean coastal dune ecosystem. Although most of the studied species nodulated with bacteria from distant origins these novel mutualisms were less effective in terms of nodulation, nitrogenase activity and plant growth than the interactions of plants and bacteria from the same origin. The relative effect of exotic bradyrhizobia was strongly positive for exotic invasive legumes and detrimental for native shrubs. We conclude that (1) the studied invasive legumes do not rely on novel mutualisms but rather need the co-introduction of compatible symbionts, and (2) since exotic rhizobia colonize native legumes in invaded areas, the lack of effectiveness of these novel symbiosis demonstrated here suggests that invasion can disrupt native belowground mutualisms and reduce native legumes fitness.

  14. Polyphenol oxidase affects normal nodule development in red clover (Trifolium pratense L.)

    PubMed Central

    Webb, K. Judith; Cookson, Alan; Allison, Gordon; Sullivan, Michael L.; Winters, Ana L.

    2014-01-01

    Polyphenol oxidase (PPO) may have multiple functions in tissues depending on its cellular or tissue localization. Here we use PPO RNAi transformants of red clover (Trifolium pratense) to determine the role PPO plays in normal development of plants, and especially in N2-fixing nodules. In red clover, PPO was not essential for either growth or nodule production, or for nodule function in plants grown under optimal, N-free conditions. However, absence of PPO resulted in a more reduced environment in all tissues, as measured by redox potential, and caused subtle developmental changes in nodules. Leaves and, to a lesser extent nodules, lacking PPO tended to accumulate phenolic compounds. A comparison of nodules of two representative contrasting clones by microscopy revealed that nodules lacking PPO were morphologically and anatomically subtly altered, and that phenolics accumulated in different cells and tissues. Developing nodules lacking PPO were longer, and there were more cell layers within the squashed cell layer (SCL), but the walls of these cells were less thickened and the cells were less squashed. Within the N2-fixing zone, bacteroids appeared more granular and were less tightly packed together, and were similar to developmentally compromised bacteroids elicited by catalase mutant rhizobia reported elsewhere. PMID:25566275

  15. From embryo sac to oil and protein bodies: embryo development in the model legume Medicago truncatula.

    PubMed

    Wang, Xin-Ding; Song, Youhong; Sheahan, Michael B; Garg, Manohar L; Rose, Ray J

    2012-01-01

    • The cell and developmental biology of zygotic embryogenesis in the model legume Medicago truncatula has received little attention. We studied M. truncatula embryogenesis from embryo sac until cotyledon maturation, including oil and protein body biogenesis. • We characterized embryo development using light and electron microscopy, measurement of protein and lipid fatty acid accumulation and by profiling the expression of key seed storage genes. • Embryo sac development in M. truncatula is of the Polygonum type. A distinctive multicellular hypophysis and suspensor develops before the globular stage and by the early cotyledon stage, the procambium connects the developing apical meristems. In the storage parenchyma of cotyledons, ovoid oil bodies surround protein bodies and the plasma membrane. Four major lipid fatty acids accumulate as cotyledons develop, paralleling the expression of OLEOSIN and the storage protein genes, VICILIN and LEGUMIN. • Zygotic embryogenesis in M. truncatula features the development of a distinctive multicellular hypophysis and an endopolyploid suspensor with basal transfer cell. A clear procambial connection between the apical meristems is evident and there is a characteristic arrangement of oil bodies in the cotyledons and radicle. Our data help link embryogenesis to the genetic regulation of oil and protein body biogenesis in legume seed.

  16. Responses to ultraviolet-B radiation by purely symbiotic and NO3-fed nodulated tree and shrub legumes indigenous to southern Africa.

    PubMed

    Chimphango, Samson B M; Musil, Charles F; Dakora, Felix D

    2004-02-01

    Purely symbiotic and NO3-fed nodulated seedlings of Virgilia oroboides (Bergius) T.M. Salter, Cyclopia maculata (L.) Vent and Podalyria calyptrata Willd. were exposed to biologically effective ultraviolet-B radiation (UV-B) to assess the effects of above- and below-ambient UV-B on growth, symbiotic function and metabolite concentrations. Seedlings were grown outdoors either on tables under ambient or 34 or 66% above-ambient UV-B conditions (UV-B100 control, UV-B134 and UV-B166, respectively), or in chambers providing below-ambient (22% of ambient) UV-B (UV-B22) along with a UV-A control and a photosynthetically active radiation (PAR) control. Exposure of seedlings to UV-B166 radiation reduced (P < or = 0.05) leaf and stem dry mass by 34 and 39%, respectively, in C. maculata, and reduced leaf nitrogen concentration (%N) by 12% in V. oroboides. Nodule %N in C. maculata and stem %N in P. calyptrata also decreased (P < or = 0.05) in response to UV-B22 radiation compared with the UV-A control, but not compared with the PAR control. Concentrations of flavonoids, soluble sugars and starch were unaltered by the UV-B treatments. Application of 1 mM NO3 to UV-B166-treated seedlings increased whole-plant dry mass of V. oroboides and P. calyptrata by 47 and 52%, respectively. Dry mass of organs, nodule %N and total N concentration of these species also increased with NO3 application. However, NO3 supply decreased (P < or = 0.05) nodule dry mass, stem %N and leaf %N as well as root and leaf anthocyanin concentrations in C. maculata. In terms of UV-B x N interactions, dry mass of stems, roots, nodules and total biomass of NO3-fed C. maculata seedlings were reduced, and nodule %N, total N and leaf anthocyanins were depressed by the UV-B134 and UV-B166 treatments relative to UV-B100-treated seedlings. Although we found that above-ambient UV-B had no effects on growth and symbiotic function of V. oroboides and P. calyptrata seedlings, feeding NO3 to these species increased (P < or

  17. [Baked product development based fermented legumes and cereals for schoolchildren snack].

    PubMed

    Granito, Marisela; Valero, Yolmar; Zambrano, Rosaura

    2010-03-01

    The objective of this work was to develop three foodstuffs based on mixes of wheat and fermented and non-fermented legumes, for the purpose of contributing with a healthy alternative for school snacks. To this aim, refined wheat flour was partially substituted with whole legume flours for the preparation of cakes, brownies and cookies, foodstuffs traditionally consumed by school age children. Cakes were formulated substituting 20% of wheat flour with Phaseolus vulgaris flour, brownies with 30% of Cajanus cajan flour and cookies with 30% of Vigna sinensis flour, using fermented and non-fermented legumes in the three products. When these products were subjected to sensorial evaluation through a test of degree of acceptability and using a hedonic scale of 7 points, values higher than 5 in the attributes taste, color and overall appraisal were found for all the products. In addition, the preference was measured with a group of 90 school children, corroborating the results obtained at laboratory level. Chemical characterization showed protein contents between 12 and 13% for the cake, 10 and 11% for the brownies and 10% for the cookies and protein digestibilities in vitro of 91%, 87% and 93%, respectively. The calorie supply, calculated per portion was of 199 kcal, 246 kcal and 237 kcal, for cakes, brownies and cookies, respectively. It was concluded that it is technically possible to incorporate fermented and non-fermented Phaseolus vulgaris, Vigna sinensis and Cajanus cajan, to highly consumed products such as cakes, brownies and cookies with a higher nutritional content and well-accepted by school-age children.

  18. The abundance and diversity of legume-nodulating rhizobia in 28-year-old plantations of tropical, subtropical, and exotic tree species: a case study from the Forest Reserve of Bandia, Senegal.

    PubMed

    Sene, Godar; Thiao, Mansour; Samba-Mbaye, Ramatoulaye; Khasa, Damase; Kane, Aboubacry; Mbaye, Mame Samba; Beaulieu, Marie-Ève; Manga, Anicet; Sylla, Samba Ndao

    2013-01-01

    Several fast-growing and multipurpose tree species have been widely used in West Africa to both reverse the tendency of land degradation and restore soil productivity. Although beneficial effects have been reported on soil stabilization, there still remains a lack of information about their impact on soil microorganisms. Our investigation has been carried out in exotic and native tree plantations of 28 years and aimed to survey and compare the abundance and genetic diversity of natural legume-nodulating rhizobia (LNR). The study of LNR is supported by the phylogenetic analysis which clustered the isolates into three genera: Bradyrhizobium, Mesorhizobium, and Sinorhizobium. The results showed close positive correlations between the sizes of LNR populations estimated both in the dry and rainy seasons and the presence of legume tree hosts. There were significant increases in Rhizobium spp. population densities in response to planting with Acacia spp., and high genetic diversities and richness of genotypes were fittest in these tree plantations. This suggests that enrichment of soil Rhizobium spp. populations is host specific. The results indicated also that species of genera Mesorhizobium and Sinorhizobium were lacking in plantations of non-host species. By contrast, there was a widespread distribution of Bradyrhizobium spp. strains across the tree plantations, with no evident specialization in regard to plantation type. Finally, the study provides information about the LNR communities associated with a range of old tree plantations and some aspects of their relationships to soil factors, which may facilitate the management of man-made forest systems that target ecosystem rehabilitation and preservation of soil biota.

  19. Molecular and phenotypic characterization of strains nodulating Anthyllis vulneraria in mine tailings, and proposal of Aminobacter anthyllidis sp. nov., the first definition of Aminobacter as legume-nodulating bacteria.

    PubMed

    Maynaud, Géraldine; Willems, Anne; Soussou, Souhir; Vidal, Céline; Mauré, Lucette; Moulin, Lionel; Cleyet-Marel, Jean-Claude; Brunel, Brigitte

    2012-03-01

    Bacterial strains from Zn-Pb mine tailings were isolated by trapping with Anthyllis vulneraria, a legume-host suitable for mine substratum phytostabilisation. Sequence analysis of the 16S rRNA gene and three housekeeping genes (atpD, dnaK and recA) showed that they were related to those of the genus Aminobacter. DNA-DNA relatedness of representative isolates supported the placement of novel strains in Aminobacter as a new species. Phenotypic data emphasize their differentiation from the other related species of Aminobacter and Mesorhizobium. Aminobacter isolates exhibited nodA sequences tightly related with M. loti as the closest nodA relative. By contrast, their nodA sequences were highly divergent from those of M. metallidurans, another species associated with A. vulneraria that carries two complete copies of nodA. Therefore, the novel bacterial strains efficient on A. vulneraria represented the first occurrence of legume symbionts in the genus Aminobacter. They represent a new species for which the name Aminobacter anthyllidis sp. nov. is proposed (type strain STM4645(T)=LMG26462(T)=CFBP7437(T)). Copyright © 2011 Elsevier GmbH. All rights reserved.

  20. Immunosuppression during Rhizobium-legume symbiosis.

    PubMed

    Luo, Li; Lu, Dawei

    2014-01-01

    Rhizobium infects host legumes to elicit new plant organs, nodules where dinitrogen is fixed as ammonia that can be directly utilized by plants. The nodulation factor (NF) produced by Rhizobium is one of the determinant signals for rhizobial infection and nodule development. Recently, it was found to suppress the innate immunity on host and nonhost plants as well as its analogs, chitins. Therefore, NF can be recognized as a microbe/pathogen-associated molecular pattern (M/PAMP) like chitin to induce the M/PAMP triggered susceptibility (M/PTS) of host plants to rhizobia. Whether the NF signaling pathway is directly associated with the innate immunity is not clear till now. In fact, other MAMPs such as lipopolysaccharide (LPS), exopolysaccharide (EPS) and cyclic-β-glucan, together with type III secretion system (T3SS) effectors are also required for rhizobial infection or survival in leguminous nodule cells. Interestingly, most of them play similarly negative roles in the innate immunity of host plants, though their signaling is not completely elucidated. Taken together, we believe that the local immunosuppression on host plants induced by Rhizobium is essential for the establishment of their symbiosis.

  1. Phylogenetic perspectives on the origins of nodulation.

    PubMed

    Doyle, Jeff J

    2011-11-01

    Recent refinements to the phylogeny of rosid angiosperms support the conclusion that nodulation has evolved several times in the so-called N(2)-fixing clade (NFC), and provide dates for these origins. The hypothesized predisposition that enabled the evolution of nodulation occurred approximately 100 million years ago (MYA), was retained in the various lineages that radiated rapidly shortly thereafter, and was functional in its non-nodulation role for at least an additional 30 million years in each nodulating lineage. Legumes radiated rapidly shortly after their origin approximately 60 MYA, and nodulation most likely evolved several times during this radiation. The major lineages of papilionoid legumes diverged close to the time of origin of nodulation, accounting for the diversity of nodule biology in the group. Nodulation symbioses exemplify the concept of "deep homology," sharing various homologous components across nonhomologous origins of nodulation, largely due to recruitment from existing functions, notably the older arbuscular mycorrhizal symbiosis. Although polyploidy may have played a role in the origin of papilionoid legume nodules, it did not do so in other legumes, nor did the prerosid whole-genome triplication lead directly to the predisposition of nodulation.

  2. Alfalfa Enod12 genes are differentially regulated during nodule development by Nod factors and Rhizobium invasion.

    PubMed Central

    Bauer, P; Crespi, M D; Szécsi, J; Allison, L A; Schultze, M; Ratet, P; Kondorosi, E; Kondorosi, A

    1994-01-01

    MsEnod12A and MsEnod12B are two early nodulin genes from alfalfa (Medicago sativa). Differential expression of these genes was demonstrated using a reverse transcription-polymerase chain reaction approach. MsEnod12A RNA was detected only in nodules and not in other plant tissues. In contrast, MsEnod12B transcripts were found in nodules and also at low levels in roots, flowers, stems, and leaves. MsEnod12B expression was enhanced in the root early after inoculation with the microsymbiont Rhizobium meliloti and after treatment with purified Nod factors, whereas MsEnod12A induction was detected only when developing nodules were visible. In situ hybridization showed that in nodules, MsEnod12 expression occurred in the infection zone. In empty Fix- nodules the MsEnod12A transcript level was much reduced, and in spontaneous nodules it was not detectable. These data indicate that MsEnod12B expression in roots is related to the action of Nod factors, whereas MsEnod12A expression is associated with the invasion process in nodules. Therefore, alfalfa possesses different mechanisms regulating MsEnod12A and MsEnod12B expression. PMID:8066132

  3. The High-Affinity Phosphate Transporter GmPT5 Regulates Phosphate Transport to Nodules and Nodulation in Soybean1[W][OA

    PubMed Central

    Qin, Lu; Zhao, Jing; Tian, Jiang; Chen, Liyu; Sun, Zhaoan; Guo, Yongxiang; Lu, Xing; Gu, Mian; Xu, Guohua; Liao, Hong

    2012-01-01

    Legume biological nitrogen (N) fixation is the most important N source in agroecosystems, but it is also a process requiring a considerable amount of phosphorus (P). Therefore, developing legume varieties with effective N2 fixation under P-limited conditions could have profound significance for improving agricultural sustainability. We show here that inoculation with effective rhizobial strains enhanced soybean (Glycine max) N2 fixation and P nutrition in the field as well as in hydroponics. Furthermore, we identified and characterized a nodule high-affinity phosphate (Pi) transporter gene, GmPT5, whose expression was elevated in response to low P. Yeast heterologous expression verified that GmPT5 was indeed a high-affinity Pi transporter. Localization of GmPT5 expression based on β-glucuronidase staining in soybean composite plants with transgenic roots and nodules showed that GmPT5 expression occurred principally in the junction area between roots and young nodules and in the nodule vascular bundles for juvenile and mature nodules, implying that GmPT5 might function in transporting Pi from the root vascular system into nodules. Overexpression or knockdown of GmPT5 in transgenic composite soybean plants altered nodulation and plant growth performance, which was partially dependent on P supply. Through both in situ and in vitro 33P uptake assays using transgenic soybean roots and nodules, we demonstrated that GmPT5 mainly functions in transporting Pi from roots to nodules, especially under P-limited conditions. We conclude that the high-affinity Pi transporter, GmPT5, controls Pi entry from roots to nodules, is critical for maintaining Pi homeostasis in nodules, and subsequently regulates soybean nodulation and growth performance. PMID:22740613

  4. Genome Wide Identification and Expression Profiling of Ethylene Receptor Genes during Soybean Nodulation.

    PubMed

    Wang, Youning; Yuan, Jinhong; Yang, Wei; Zhu, Lin; Su, Chao; Wang, Xiaodi; Wu, Haiyan; Sun, Zhengxi; Li, Xia

    2017-01-01

    It has long been known that the gaseous plant hormone ethylene plays a key role in nodulation in legumes. The perception of ethylene by a family of five membrane-localized receptors is necessary to trigger the ethylene signaling pathway, which regulates various biological responses in Arabidopsis. However, a systematic analysis of the ethylene receptors in leguminous plants and their roles in nodule development is lacking. In this study, we performed a characterization of ethylene receptor genes based on the latest Glycine max genome sequence and a public microarray database. Eleven ethylene receptor family genes were identified in soybean through homology searches, and they were divided into two subgroups. Exon-intron analysis showed that the gene structures are highly conserved within each group. Further analysis of their expression patterns showed that these ethylene receptor genes are differentially expressed in various soybean tissues and organs, including functional nodules. Notably, the ethylene receptor genes showed different responses to rhizobial infection and Nod factors, suggesting a possible role for ethylene receptors and ethylene signaling in rhizobia-host cell interactions and nodulation in soybean. Together, these data indicate the functional divergence of ethylene receptor genes in soybean, and that some of these receptors mediate nodulation, including rhizobial infection, nodule development, and nodule functionality. These findings provide a foundation for further elucidation of the molecular mechanism by which the ethylene signaling pathway regulates nodulation in soybean, as well as other legumes.

  5. [Milker's nodules].

    PubMed

    Hansen, S K; Mertz, H; Krogdahl, A S; Veien, N K

    1997-01-20

    Milker's nodule is a parapox virus infection seen mostly on the hands of dairy farmers. We saw 15 cases over a period of two years in the County of North Jutland. Clinically, milker's nodule goes through a papular, a nodular and a crusted stage. Most patients were seen when the infection was in the nodular stage, an often painful condition requiring treatment. Three patients developed an erythema multiformelike secondary eruption. Lesions from nine patients were removed for histological examination. The histology of all lesions was consistent with milker's nodule. In three of seven patients parapox virus was demonstrated by electron microscopy. Treatment was commonly curettage followed by cauterization.

  6. Development of weaning food from sorghum supplemented with legumes and oil seeds.

    PubMed

    Asma, M Ali; El Fadil, E Babiker; El Tinay, Abdullahi H

    2006-03-01

    The development of low-cost, high-protein food supplements for weaning infants from local and readily available raw materials is a constant challenge for developing countries. To formulate, develop, and assess the nutritive value, acceptability, and keeping quality of sorghum-based staple dried flakes as instant weaning foods. Weaning blends composed of 42% sorghum supplemented with 20% legumes, 10% oil seeds, and 28% additives (sugar, oil, skim milk powder, and vanillin) were prepared according to FAO/WHO/UNU recommendations and processed in a twin-roller drum dryer. The effects of fermentation and of the addition of malt on the nutritive value and functional properties of the blends were investigated. The blends were found to contain 16.6% to 19.3% protein, 68.7% to 72.7% carbohydrate, 0.9% to 1.3% fiber, and 405.8 to 413.2 kcal of energy per 100 g. The iron content of the blends ranged from 5.3 to 9.1 mg/100 g, and the calcium content ranged from 150 to 220 mg/100 g. All blends reconstituted well and formed a soft paste when stirred with hot or cold water. The water-holding capacity, wettability, and bulk density were within the ranges of corresponding values of commercial weaning foods. Sensory attributes, viscosity values, and in vitro digestibility varied among the blends, whereas lysing content improved considerably (p < or = .05) for all blends. All blends had similar keeping quality, with no signs of spoilage or development of off-flavors or colors after 10 months of storage. Most blends remained free of aflatoxins. Legumes and oil seeds can be effectively used in sorghum-based weaning foods as an acceptable protein and mineral supplement.

  7. Rhizobial Factors Required for Stem Nodule Maturation and Maintenance in Sesbania rostrata-Azorhizobium caulinodans ORS571 Symbiosis▿ †

    PubMed Central

    Suzuki, Shino; Aono, Toshihiro; Lee, Kyung-Bum; Suzuki, Tadahiro; Liu, Chi-Te; Miwa, Hiroki; Wakao, Seiji; Iki, Taichiro; Oyaizu, Hiroshi

    2007-01-01

    The molecular and physiological mechanisms behind the maturation and maintenance of N2-fixing nodules during development of symbiosis between rhizobia and legumes still remain unclear, although the early events of symbiosis are relatively well understood. Azorhizobium caulinodans ORS571 is a microsymbiont of the tropical legume Sesbania rostrata, forming N2-fixing nodules not only on the roots but also on the stems. In this study, 10,080 transposon-inserted mutants of A. caulinodans ORS571 were individually inoculated onto the stems of S. rostrata, and those mutants that induced ineffective stem nodules, as displayed by halted development at various stages, were selected. From repeated observations on stem nodulation, 108 Tn5 mutants were selected and categorized into seven nodulation types based on size and N2 fixation activity. Tn5 insertions of some mutants were found in the well-known nodulation, nitrogen fixation, and symbiosis-related genes, such as nod, nif, and fix, respectively, lipopolysaccharide synthesis-related genes, C4 metabolism-related genes, and so on. However, other genes have not been reported to have roles in legume-rhizobium symbiosis. The list of newly identified symbiosis-related genes will present clues to aid in understanding the maturation and maintenance mechanisms of nodules. PMID:17720818

  8. The spread of Bradyrhizobium lineages across host legume clades: from Abarema to Zygia.

    PubMed

    Parker, Matthew A

    2015-04-01

    To analyze macroevolutionary patterns in host use by Bradyrhizobium root-nodule bacteria, 420 strains from 75 legume host genera (sampled in 25 countries) were characterized for portions of six housekeeping genes and the nifD locus in the symbiosis island chromosomal region. Most Bradyrhizobium clades utilized very divergent sets of legume hosts. This suggests that Bradyrhizobium spread across the major legume lineages early in its evolution, with only a few derived clades subsequently developing a narrower pattern of host use. Significant modularity existed in the network structure of recent host jumps (inferred from cases where closely related strain pairs were found on different legume taxa). This implies that recent host switching has occurred most often within particular subgroups of legumes. Nevertheless, the observed link structure would allow a bacterial lineage to reach almost any of the 75 legume host genera in a relatively small number of steps. However, permutation tests also showed that symbionts from certain host plant clades were significantly more similar than would be the case if bacteria were distributed at random on the trees. Related legumes thus harbored related sets of symbionts in some cases, indicating some degree of phylogenetic conservatism in partner selection.

  9. Blue light does not inhibit nodulation in Sesbania rostrata.

    PubMed

    Shimomura, Aya; Arima, Susumu; Hayashi, Makoto; Maymon, Maskit; Hirsch, Ann M; Suzuki, Akihiro

    2017-01-02

    Earlier, we reported that root nodulation was inhibited by blue light irradiation of Lotus japonicus. Because some legumes do not establish nodules exclusively on underground roots, we investigated whether nodule formation in Sesbania rostrata, which forms both root and "stem" nodules following inoculation with Azorhizobium caulinodans, is inhibited by blue light as are L. japonicus nodules. We found that neither S. rostrata nodulation nor nitrogen fixation was inhibited by blue light exposure. Moreover, although A. caulinodans proliferation was not affected by blue light irradiation, bacterial survival was decreased. Therefore, blue light appears to impose different responses depending on the legume-rhizobial symbiosis.

  10. A nodule-specific lipid transfer protein AsE246 participates in transport of plant-synthesized lipids to symbiosome membrane and is essential for nodule organogenesis in Chinese milk vetch.

    PubMed

    Lei, Lei; Chen, Ling; Shi, Xiaofeng; Li, Yixing; Wang, Jianyun; Chen, Dasong; Xie, Fuli; Li, Youguo

    2014-02-01

    Rhizobia in legume root nodules fix nitrogen in symbiosomes, organelle-like structures in which a membrane from the host plant surrounds the symbiotic bacteria. However, the components that transport plant-synthesized lipids to the symbiosome membrane remain unknown. This study identified and functionally characterized the Chinese milk vetch (Astragalus sinicus) lipid transfer protein AsE246, which is specifically expressed in nodules. It was found that AsE246 can bind lipids in vitro. More importantly, AsE246 can bind the plant-synthesized membrane lipid digalactosyldiacylglycerol in vivo. Immunofluorescence and immunoelectron microscopy showed that AsE246 and digalactosyldiacylglycerol localize in the symbiosome membrane and are present in infection threads. Overexpression of AsE246 resulted in increased nodule numbers; knockdown of AsE246 resulted in reduced nodule numbers, decreased lipids contents in nodules, diminished nitrogen fixation activity, and abnormal development of symbiosomes. AsE246 knockdown also resulted in fewer infection threads, nodule primordia, and nodules, while AsE246 overexpression resulted in more infection threads and nodule primordia, suggesting that AsE246 affects nodule organogenesis associated with infection thread formation. Taken together, these results indicate that AsE246 contributes to lipids transport to the symbiosome membrane, and this transport is required for effective legume-rhizobium symbiosis.

  11. A Nodule-Specific Lipid Transfer Protein AsE246 Participates in Transport of Plant-Synthesized Lipids to Symbiosome Membrane and Is Essential for Nodule Organogenesis in Chinese Milk Vetch1[C][W][OPEN

    PubMed Central

    Lei, Lei; Chen, Ling; Shi, Xiaofeng; Li, Yixing; Wang, Jianyun; Chen, Dasong; Xie, Fuli; Li, Youguo

    2014-01-01

    Rhizobia in legume root nodules fix nitrogen in symbiosomes, organelle-like structures in which a membrane from the host plant surrounds the symbiotic bacteria. However, the components that transport plant-synthesized lipids to the symbiosome membrane remain unknown. This study identified and functionally characterized the Chinese milk vetch (Astragalus sinicus) lipid transfer protein AsE246, which is specifically expressed in nodules. It was found that AsE246 can bind lipids in vitro. More importantly, AsE246 can bind the plant-synthesized membrane lipid digalactosyldiacylglycerol in vivo. Immunofluorescence and immunoelectron microscopy showed that AsE246 and digalactosyldiacylglycerol localize in the symbiosome membrane and are present in infection threads. Overexpression of AsE246 resulted in increased nodule numbers; knockdown of AsE246 resulted in reduced nodule numbers, decreased lipids contents in nodules, diminished nitrogen fixation activity, and abnormal development of symbiosomes. AsE246 knockdown also resulted in fewer infection threads, nodule primordia, and nodules, while AsE246 overexpression resulted in more infection threads and nodule primordia, suggesting that AsE246 affects nodule organogenesis associated with infection thread formation. Taken together, these results indicate that AsE246 contributes to lipids transport to the symbiosome membrane, and this transport is required for effective legume-rhizobium symbiosis. PMID:24367021

  12. Rhizobium calliandrae sp. nov., Rhizobium mayense sp. nov. and Rhizobium jaguaris sp. nov., rhizobial species nodulating the medicinal legume Calliandra grandiflora.

    PubMed

    Rincón-Rosales, Reiner; Villalobos-Escobedo, José M; Rogel, Marco A; Martinez, Julio; Ormeño-Orrillo, Ernesto; Martínez-Romero, Esperanza

    2013-09-01

    Calliandra grandiflora has been used as a medicinal plant for thousands of years in Mexico. Rhizobial strains were obtained from root nodules of C. grandiflora collected from different geographical regions in Chiapas and characterized by BOX-PCR, amplified rDNA restriction analysis (ARDRA) and 16S rRNA gene sequence analysis. Most isolates corresponded to members of the genus Rhizobium and those not related to species with validly published names were further characterized by recA, atpD, rpoB and nifH gene phylogenies, phenotypic and DNA-DNA hybridization analyses. Three novel related species of the genus Rhizobium within the 'Rhizobium tropici group' share the same symbiovar that may be named sv. calliandrae. The names proposed for the three novel species are Rhizobium calliandrae sp. nov. (type strain, CCGE524(T) =ATCC BAA-2435(T) =CIP 110456(T) =LBP2-1(T)), Rhizobium mayense sp. nov. (type strain, CCGE526(T) =ATCC BAA-2446(T) = CIP 110454(T) =NSJP1-1(T)) and Rhizobium jaguaris sp. nov. (type strain, CCGE525(T) =ATCC BAA-2445(T) =CIP 110453(T) =SJP1-2(T)).

  13. PII Overexpression in Lotus japonicus Affects Nodule Activity in Permissive Low-Nitrogen Conditions and Increases Nodule Numbers in High Nitrogen Treated Plants.

    PubMed

    D'Apuzzo, Enrica; Valkov, Vladimir Totev; Parlati, Aurora; Omrane, Selim; Barbulova, Ani; Sainz, Maria Martha; Lentini, Marco; Esposito, Sergio; Rogato, Alessandra; Chiurazzi, Maurizio

    2015-04-01

    We report here the first characterization of a GLNB1 gene coding for the PII protein in leguminous plants. The main purpose of this work was the investigation of the possible roles played by this multifunctional protein in nodulation pathways. The Lotus japonicus LjGLB1 gene shows a significant transcriptional regulation during the light-dark cycle and different nitrogen availability, conditions that strongly affect nodule formation, development, and functioning. We also report analysis of the spatial profile of expression of LjGLB1 in root and nodule tissues and of the protein's subcellular localization. Transgenic L. japonicus lines overexpressing the PII protein were obtained and tested for the analysis of the symbiotic responses in different conditions. The uncoupling of PII from its native regulation affects nitrogenase activity and nodule polyamine content. Furthermore, our results suggest the involvement of PII in the signaling of the nitrogen nutritional status affecting the legumes' predisposition for nodule formation.

  14. Fate map of Medicago truncatula root nodules.

    PubMed

    Xiao, Ting Ting; Schilderink, Stefan; Moling, Sjef; Deinum, Eva E; Kondorosi, Eva; Franssen, Henk; Kulikova, Olga; Niebel, Andreas; Bisseling, Ton

    2014-09-01

    Legume root nodules are induced by N-fixing rhizobium bacteria that are hosted in an intracellular manner. These nodules are formed by reprogramming differentiated root cells. The model legume Medicago truncatula forms indeterminate nodules with a meristem at their apex. This organ grows by the activity of the meristem that adds cells to the different nodule tissues. In Medicago sativa it has been shown that the nodule meristem is derived from the root middle cortex. During nodule initiation, inner cortical cells and pericycle cells are also mitotically activated. However, whether and how these cells contribute to the mature nodule has not been studied. Here, we produce a nodule fate map that precisely describes the origin of the different nodule tissues based on sequential longitudinal sections and on the use of marker genes that allow the distinction of cells originating from different root tissues. We show that nodule meristem originates from the third cortical layer, while several cell layers of the base of the nodule are directly formed from cells of the inner cortical layers, root endodermis and pericycle. The latter two differentiate into the uninfected tissues that are located at the base of the mature nodule, whereas the cells derived from the inner cortical cell layers form about eight cell layers of infected cells. This nodule fate map has then been used to re-analyse several mutant nodule phenotypes. This showed, among other things, that intracellular release of rhizobia in primordium cells and meristem daughter cells are regulated in a different manner.

  15. Legume growth-promoting rhizobia: an overview on the Mesorhizobium genus.

    PubMed

    Laranjo, Marta; Alexandre, Ana; Oliveira, Solange

    2014-01-20

    The need for sustainable agricultural practices is revitalizing the interest in biological nitrogen fixation and rhizobia-legumes symbioses, particularly those involving economically important legume crops in terms of food and forage. The genus Mesorhizobium includes species with high geographical dispersion and able to nodulate a wide variety of legumes, including important crop species, like chickpea or biserrula. Some cases of legume-mesorhizobia inoculant introduction represent exceptional opportunities to study the rhizobia genomes evolution and the evolutionary relationships among species. Complete genome sequences revealed that mesorhizobia typically harbour chromosomal symbiosis islands. The phylogenies of symbiosis genes, such as nodC, are not congruent with the phylogenies based on core genes, reflecting rhizobial host range, rather than species affiliation. This agrees with studies showing that Mesorhizobium species are able to exchange symbiosis genes through lateral transfer of chromosomal symbiosis islands, thus acquiring the ability to nodulate new hosts. Phylogenetic analyses of the Mesorhizobium genus based on core and accessory genes reveal complex evolutionary relationships and a high genomic plasticity, rendering the Mesorhizobium genus as a good model to investigate rhizobia genome evolution and adaptation to different host plants. Further investigation of symbiosis genes as well as stress response genes will certainly contribute to understand mesorhizobia-legume symbiosis and to develop more effective mesorhizobia inoculants.

  16. The Carbon-Nitrogen Balance of the Nodule and Its Regulation under Elevated Carbon Dioxide Concentration

    PubMed Central

    2014-01-01

    Legumes have developed a unique way to interact with bacteria: in addition to preventing infection from pathogenic bacteria like any other plant, legumes also developed a mutualistic symbiotic relationship with one gender of soil bacteria: rhizobium. This interaction leads to the development of a new root organ, the nodule, where the differentiated bacteria fix for the plant the atmospheric dinitrogen (atmN2). In exchange, the symbiont will benefit from a permanent source of carbon compounds, products of the photosynthesis. The substantial amounts of fixed carbon dioxide dedicated to the symbiont imposed to the plant a tight regulation of the nodulation process to balance carbon and nitrogen incomes and outcomes. Climate change including the increase of the concentration of the atmospheric carbon dioxide is going to modify the rates of plant photosynthesis, the balance between nitrogen and carbon, and, as a consequence, the regulatory mechanisms of the nodulation process. This review focuses on the regulatory mechanisms controlling carbon/nitrogen balances in the context of legume nodulation and discusses how the change in atmospheric carbon dioxide concentration could affect nodulation efficiency. PMID:24987690

  17. The carbon-nitrogen balance of the nodule and its regulation under elevated carbon dioxide concentration.

    PubMed

    Libault, Marc

    2014-01-01

    Legumes have developed a unique way to interact with bacteria: in addition to preventing infection from pathogenic bacteria like any other plant, legumes also developed a mutualistic symbiotic relationship with one gender of soil bacteria: rhizobium. This interaction leads to the development of a new root organ, the nodule, where the differentiated bacteria fix for the plant the atmospheric dinitrogen (atmN2). In exchange, the symbiont will benefit from a permanent source of carbon compounds, products of the photosynthesis. The substantial amounts of fixed carbon dioxide dedicated to the symbiont imposed to the plant a tight regulation of the nodulation process to balance carbon and nitrogen incomes and outcomes. Climate change including the increase of the concentration of the atmospheric carbon dioxide is going to modify the rates of plant photosynthesis, the balance between nitrogen and carbon, and, as a consequence, the regulatory mechanisms of the nodulation process. This review focuses on the regulatory mechanisms controlling carbon/nitrogen balances in the context of legume nodulation and discusses how the change in atmospheric carbon dioxide concentration could affect nodulation efficiency.

  18. [Production of inhibiting plant growth and development hormones by pathogenic for legumes Pseudomonas genus bacteria].

    PubMed

    Dankevich, L A

    2013-01-01

    It has been studied the ability of pathogenic for legumes pathovars of Pseudomonas genus to produce ethylene and abscisic acid in vitro. A direct correlation between the level of ethylene production by agent of bacterial pea burn--Pseudomonas syringae pv. pisi and level of its aggressiveness for plants has been found. It is shown that the amount of abscisic acid synthesized by pathogenic for legumes Pseudomonas genus bacteria correlates with their aggressiveness for plants.

  19. Systemic Regulation of Soybean Nodulation by Acidic Growth Conditions1[OA

    PubMed Central

    Lin, Meng-Han; Gresshoff, Peter M.; Ferguson, Brett J.

    2012-01-01

    Mechanisms inhibiting legume nodulation by low soil pH, although highly prevalent and economically significant, are poorly understood. We addressed this in soybean (Glycine max) using a combination of physiological and genetic approaches. Split-root and grafting studies using an autoregulation-of-nodulation-deficient mutant line, altered in the autoregulation-of-nodulation receptor kinase GmNARK, determined that a systemic, shoot-controlled, and GmNARK-dependent mechanism was critical for facilitating the inhibitory effect. Acid inhibition was independent of aluminum ion concentration and occurred early in nodule development, between 12 and 96 h post inoculation with Bradyrhizobium japonicum. Biological effects were confirmed by measuring transcript numbers of known early nodulation genes. Transcripts decreased on both sides of split-root systems, where only one side was subjected to low-pH conditions. Our findings enhance the present understanding of the innate mechanisms regulating legume nodulation control under acidic conditions, which could benefit future attempts in agriculture to improve nodule development and biological nitrogen fixation in acid-stressed soils. PMID:23054568

  20. Architecture of infection thread networks in developing root nodules induced by the symbiotic bacterium Sinorhizobium meliloti on Medicago truncatula.

    PubMed

    Monahan-Giovanelli, Hannah; Pinedo, Catalina Arango; Gage, Daniel J

    2006-02-01

    During the course of the development of nitrogen-fixing root nodules induced by Sinorhizobium meliloti on the model plant Medicago truncatula, tubules called infection threads are cooperatively constructed to deliver the bacterial symbiont from the root surface to cells in the interior of the root and developing nodule. Three-dimensional reconstructions of infection threads inside M. truncatula nodules showed that the threads formed relatively simple, tree-like networks. Some characteristics of thread networks, such as branch length, branch density, and branch surface-to-volume ratios, were remarkably constant across nodules in different stages of development. The overall direction of growth of the networks changed as nodules developed. In 5-d-old nodules, the overall growth of the network was directed inward toward the root. However, well-defined regions of these young networks displayed an outward growth bias, indicating that they were likely in the process of repolarizing their direction of development in response to the formation of the outward-growing nodule meristem. In 10- and 30-d-old nodules, the branches of the network grew outward toward the meristem and away from the roots on which the nodules developed.

  1. A Conserved Potential Development Framework Applies to Shoots of Legume Species with Contrasting Morphogenetic Strategies

    PubMed Central

    Faverjon, Lucas; Escobar-Gutiérrez, Abraham J.; Litrico, Isabelle; Louarn, Gaëtan

    2017-01-01

    A great variety of legume species are used for forage production and grown in multi-species grasslands. Despite their close phylogenetic relationship, they display a broad range of morphologies that markedly affect their competitive abilities and persistence in mixtures. Little is yet known about the component traits that control the deployment of plant architecture in most of these species. During the present study, we compared the patterns of shoot organogenesis and shoot organ growth in contrasting forage species belonging to the four morphogenetic groups previously identified in herbaceous legumes (i.e., stolon-formers, rhizome-formers, crown-formers tolerant to defoliation and crown-formers intolerant to defoliation). To achieve this, three greenhouse experiments were carried out using plant species from each group (namely alfalfa, birdsfoot trefoil, sainfoin, kura clover, red clover, and white clover) which were grown at low density under non-limiting water and soil nutrient availability. The potential morphogenesis of shoots characterized under these conditions showed that all the species shared a number of common morphogenetic features. All complied with a generalized classification of shoot axes into three types (main axis, primary and secondary axes). A common quantitative framework for vegetative growth and development involved: (i) the regular development of all shoot axes in thermal time and a deterministic branching pattern in the absence of stress; (ii) a temporal coordination of organ growth at the phytomer level that was highly conserved irrespective of phytomer position, and (iii) an identical allometry determining the surface area of all the leaves. The species differed in their architecture as a consequence of the values taken by component traits of morphogenesis. Assessing the relationships between the traits studied showed that these species were distinct from each other along two main PCA axes which explained 68% of total variance: the first

  2. nip, a symbiotic Medicago truncatula mutant that forms root nodules with aberrant infection threads and plant defense-like response.

    PubMed

    Veereshlingam, Harita; Haynes, Janine G; Penmetsa, R Varma; Cook, Douglas R; Sherrier, D Janine; Dickstein, Rebecca

    2004-11-01

    To investigate the legume-Rhizobium symbiosis, we isolated and studied a novel symbiotic mutant of the model legume Medicago truncatula, designated nip (numerous infections and polyphenolics). When grown on nitrogen-free media in the presence of the compatible bacterium Sinorhizobium meliloti, the nip mutant showed nitrogen deficiency symptoms. The mutant failed to form pink nitrogen-fixing nodules that occur in the wild-type symbiosis, but instead developed small bump-like nodules on its roots that were blocked at an early stage of development. Examination of the nip nodules by light microscopy after staining with X-Gal for S. meliloti expressing a constitutive GUS gene, by confocal microscopy following staining with SYTO-13, and by electron microscopy revealed that nip initiated symbiotic interactions and formed nodule primordia and infection threads. The infection threads in nip proliferated abnormally and very rarely deposited rhizobia into plant host cells; rhizobia failed to differentiate further in these cases. nip nodules contained autofluorescent cells and accumulated a brown pigment. Histochemical staining of nip nodules revealed this pigment to be polyphenolic accumulation. RNA blot analyses demonstrated that nip nodules expressed only a subset of genes associated with nodule organogenesis, as well as elevated expression of a host defense-associated phenylalanine ammonia lyase gene. nip plants were observed to have abnormal lateral roots. nip plant root growth and nodulation responded normally to ethylene inhibitors and precursors. Allelism tests showed that nip complements 14 other M. truncatula nodulation mutants but not latd, a mutant with a more severe nodulation phenotype as well as primary and lateral root defects. Thus, the nip mutant defines a new locus, NIP, required for appropriate infection thread development during invasion of the nascent nodule by rhizobia, normal lateral root elongation, and normal regulation of host defense-like responses

  3. The Class II Trehalose 6-phosphate Synthase Gene PvTPS9 Modulates Trehalose Metabolism in Phaseolus vulgaris Nodules

    PubMed Central

    Barraza, Aarón; Contreras-Cubas, Cecilia; Estrada-Navarrete, Georgina; Reyes, José L.; Juárez-Verdayes, Marco A.; Avonce, Nelson; Quinto, Carmen; Díaz-Camino, Claudia; Sanchez, Federico

    2016-01-01

    Legumes form symbioses with rhizobia, producing nitrogen-fixing nodules on the roots of the plant host. The network of plant signaling pathways affecting carbon metabolism may determine the final number of nodules. The trehalose biosynthetic pathway regulates carbon metabolism and plays a fundamental role in plant growth and development, as well as in plant-microbe interactions. The expression of genes for trehalose synthesis during nodule development suggests that this metabolite may play a role in legume-rhizobia symbiosis. In this work, PvTPS9, which encodes a Class II trehalose-6-phosphate synthase (TPS) of common bean (Phaseolus vulgaris), was silenced by RNA interference in transgenic nodules. The silencing of PvTPS9 in root nodules resulted in a reduction of 85% (± 1%) of its transcript, which correlated with a 30% decrease in trehalose contents of transgenic nodules and in untransformed leaves. Composite transgenic plants with PvTPS9 silenced in the roots showed no changes in nodule number and nitrogen fixation, but a severe reduction in plant biomass and altered transcript profiles of all Class II TPS genes. Our data suggest that PvTPS9 plays a key role in modulating trehalose metabolism in the symbiotic nodule and, therefore, in the whole plant. PMID:27847509

  4. The Class II Trehalose 6-phosphate Synthase Gene PvTPS9 Modulates Trehalose Metabolism in Phaseolus vulgaris Nodules.

    PubMed

    Barraza, Aarón; Contreras-Cubas, Cecilia; Estrada-Navarrete, Georgina; Reyes, José L; Juárez-Verdayes, Marco A; Avonce, Nelson; Quinto, Carmen; Díaz-Camino, Claudia; Sanchez, Federico

    2016-01-01

    Legumes form symbioses with rhizobia, producing nitrogen-fixing nodules on the roots of the plant host. The network of plant signaling pathways affecting carbon metabolism may determine the final number of nodules. The trehalose biosynthetic pathway regulates carbon metabolism and plays a fundamental role in plant growth and development, as well as in plant-microbe interactions. The expression of genes for trehalose synthesis during nodule development suggests that this metabolite may play a role in legume-rhizobia symbiosis. In this work, PvTPS9, which encodes a Class II trehalose-6-phosphate synthase (TPS) of common bean (Phaseolus vulgaris), was silenced by RNA interference in transgenic nodules. The silencing of PvTPS9 in root nodules resulted in a reduction of 85% (± 1%) of its transcript, which correlated with a 30% decrease in trehalose contents of transgenic nodules and in untransformed leaves. Composite transgenic plants with PvTPS9 silenced in the roots showed no changes in nodule number and nitrogen fixation, but a severe reduction in plant biomass and altered transcript profiles of all Class II TPS genes. Our data suggest that PvTPS9 plays a key role in modulating trehalose metabolism in the symbiotic nodule and, therefore, in the whole plant.

  5. Changes in RACK1 expression induce defects in nodulation and development in Phaseolus vulgaris

    PubMed Central

    Islas-Flores, Tania; Guillén, Gabriel; Sánchez, Federico; Villanueva, Marco A.

    2012-01-01

    RACK1 is a scaffold protein with the ability to interact in a regulated manner with a diverse number of ligands from distinct signal-transduction pathways. This assessment allowed us to infer that it may be involved in different processes such as nodulation. In a recent study we showed by silencing, that PvRACK1 has a pivotal role in cell expansion and in symbiosome and bacteroid integrity during nodule development in Phaseolus vulgaris. On the other hand, we have also observed that its overexpression provokes a dramatic phenotype in: (a) seedlings that have been exposed to heat, in which systemic necrosis is induced; and (b) in Agrobacterium rhizogenes-transformed roots, where nodulation is strongly inhibited and nodules show early senescent symptoms. These findings indicate that PvRACK1 may be an integrator of diverse signal-transduction pathways in processes as varied as nodulation, cell expansion, heat stress responses, and systemic activation of necrosis. PMID:22301979

  6. Organogenic nodule development in hop (Humulus lupulus L.): Transcript and metabolic responses

    PubMed Central

    Fortes, Ana M; Santos, Filipa; Choi, Young H; Silva, Marta S; Figueiredo, Andreia; Sousa, Lisete; Pessoa, Fernando; Santos, Bartolomeu A; Sebastiana, Mónica; Palme, Klaus; Malhó, Rui; Verpoorte, Rob; Pais, Maria S

    2008-01-01

    Background Hop (Humulus lupulus L.) is an economically important plant forming organogenic nodules which can be used for genetic transformation and micropropagation. We are interested in the mechanisms underlying reprogramming of cells through stress and hormone treatments. Results An integrated molecular and metabolomic approach was used to investigate global gene expression and metabolic responses during development of hop's organogenic nodules. Transcript profiling using a 3,324-cDNA clone array revealed differential regulation of 133 unigenes, classified into 11 functional categories. Several pathways seem to be determinant in organogenic nodule formation, namely defense and stress response, sugar and lipid metabolism, synthesis of secondary metabolites and hormone signaling. Metabolic profiling using 1H NMR spectroscopy associated to two-dimensional techniques showed the importance of metabolites related to oxidative stress response, lipid and sugar metabolism and secondary metabolism in organogenic nodule formation. Conclusion The expression profile of genes pivotal for energy metabolism, together with metabolites profile, suggested that these morphogenic structures gain energy through a heterotrophic, transport-dependent and sugar-degrading anaerobic metabolism. Polyamines and auxins are likely to be involved in the regulation of expression of many genes related to organogenic nodule formation. These results represent substantial progress toward a better understanding of this complex developmental program and reveal novel information regarding morphogenesis in plants. PMID:18823540

  7. EFD Is an ERF transcription factor involved in the control of nodule number and differentiation in Medicago truncatula.

    PubMed

    Vernié, Tatiana; Moreau, Sandra; de Billy, Françoise; Plet, Julie; Combier, Jean-Philippe; Rogers, Christian; Oldroyd, Giles; Frugier, Florian; Niebel, Andreas; Gamas, Pascal

    2008-10-01

    Mechanisms regulating legume root nodule development are still poorly understood, and very few regulatory genes have been cloned and characterized. Here, we describe EFD (for ethylene response factor required for nodule differentiation), a gene that is upregulated during nodulation in Medicago truncatula. The EFD transcription factor belongs to the ethylene response factor (ERF) group V, which contains ERN1, 2, and 3, three ERFs involved in Nod factor signaling. The role of EFD in the regulation of nodulation was examined through the characterization of a null deletion mutant (efd-1), RNA interference, and overexpression studies. These studies revealed that EFD is a negative regulator of root nodulation and infection by Rhizobium and that EFD is required for the formation of functional nitrogen-fixing nodules. EFD appears to be involved in the plant and bacteroid differentiation processes taking place beneath the nodule meristem. We also showed that EFD activated Mt RR4, a cytokinin primary response gene that encodes a type-A response regulator. We propose that EFD induction of Mt RR4 leads to the inhibition of cytokinin signaling, with two consequences: the suppression of new nodule initiation and the activation of differentiation as cells leave the nodule meristem. Our work thus reveals a key regulator linking early and late stages of nodulation and suggests that the regulation of the cytokinin pathway is important both for nodule initiation and development.

  8. A translationally controlled tumor protein gene Rpf41 is required for the nodulation of Robinia pseudoacacia.

    PubMed

    Chou, Minxia; Xia, Congcong; Feng, Zhao; Sun, Yali; Zhang, Dehui; Zhang, Mingzhe; Wang, Li; Wei, Gehong

    2016-03-01

    Translationally controlled tumor protein (TCTP) is fundamental for the regulation of development and general growth in eukaryotes. Its multiple functions have been deduced from its involvement in several cell pathways, but its potential involvement in symbiotic nodulation of legumes cannot be suggested a priori. In the present work, we identified and characterized from the woody leguminous tree Robinia pseudoacacia a homolog of TCTP, Rpf41, which was up-regulated in the infected roots at 15 days post-inoculation but decreased in the matured nodules. Subcellular location assay showed that Rpf41 protein was located in the plasma membrane, cytoplasm, nucleus, and also maybe in cytoskeleton. Knockdown of Rpf41 via RNA interference (RNAi) resulted in the impaired development of both nodule and root hair. Compared with wild plants, the root and stem length, fresh weight and nodule number per plant was decreased dramatically in Rpf41 RNAi plants. The number of ITs or nodule primordia was also significantly reduced in the Rpf41 RNAi roots. The analyses of nodule ultrastructure showed that the infected cell development in Rpf41 RNAi nodules remained in zone II, which had fewer infected cells. Furthermore, the symbiosomes displayed noticeable shrinkage of bacteroid and peribacteroid space enlargement in the infected cells of Rpf41 RNAi nodules. In the deeper cell layers, a more remarkable aberration of the infected cell ultrastructure was observed, and electron-transparent lesions in the bacteroid cytoplasm were detected. These results identify TCTP as an important regulator of symbiotic nodulation in legume for the first time, and it may be involved in symbiotic cell differentiation and preventing premature aging of the young nodules in R. pseudoacacia.

  9. Suppressive effect of the angiogenesis inhibitor TNP-470 on the development of carcinogen-induced hepatic nodules in rats.

    PubMed

    Ikebe, T; Yamamoto, T; Kubo, S; Hirohashi, K; Kinoshita, H; Kaneda, K; Sakurai, M

    1998-02-01

    Tumor metastasis can be prevented by inhibiting angiogenesis. In the present study, we have demonstrated that the angiogenesis inhibitor TNP-470 also suppresses the development of primary hepatic nodules. Hepatocarcinogenesis was performed by the feeding of 2-acetylaminofluorene to hepatectomized rats during 8-14 weeks of age. Predominantly arterial-to-portal circulation and sinusoidal capillarization were determined by the staining of nodules with arterially infused ink and immunostaining for factor VIII-related antigen, respectively. Intraperitoneal administration of 30 mg/kg b.w. of TNP-470 twice a week significantly reduced the number of hepatic nodules. Among the nodules, hyperplastic nodules stained with ink, atypical hyperplastic nodules and hepatocellular carcinoma, all of which possess structurally altered sinusoidal endothelial cells or capillary-type endothelial cells, were dramatically decreased in number. Suppression was observed equally in nodules of all sizes. TNP-470 was more effective when administered during 8-20 weeks than during 14-26 weeks. In contrast, ink-non-stained hyperplastic nodules, which have normal sinusoidal endothelial cells, were not affected at all. The present results indicate that TNP-470 suppresses the development of primary hepatic nodules whose microvessels are capillaries or transitional forms from sinusoids to capillaries.

  10. Dissecting the Root Nodule Transcriptome of Chickpea (Cicer arietinum L.).

    PubMed

    Kant, Chandra; Pradhan, Seema; Bhatia, Sabhyata

    2016-01-01

    A hallmark trait of chickpea (Cicer arietinum L.), like other legumes, is the capability to convert atmospheric nitrogen (N2) into ammonia (NH3) in symbiotic association with Mesorhizobium ciceri. However, the complexity of molecular networks associated with the dynamics of nodule development in chickpea need to be analyzed in depth. Hence, in order to gain insights into the chickpea nodule development, the transcriptomes of nodules at early, middle and late stages of development were sequenced using the Roche 454 platform. This generated 490.84 Mb sequence data comprising 1,360,251 reads which were assembled into 83,405 unigenes. Transcripts were annotated using Gene Ontology (GO), Cluster of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways analysis. Differential expression analysis revealed that a total of 3760 transcripts were differentially expressed in at least one of three stages, whereas 935, 117 and 2707 transcripts were found to be differentially expressed in the early, middle and late stages of nodule development respectively. MapMan analysis revealed enrichment of metabolic pathways such as transport, protein synthesis, signaling and carbohydrate metabolism during root nodulation. Transcription factors were predicted and analyzed for their differential expression during nodule development. Putative nodule specific transcripts were identified and enriched for GO categories using BiNGO which revealed many categories to be enriched during nodule development, including transcription regulators and transporters. Further, the assembled transcriptome was also used to mine for genic SSR markers. In conclusion, this study will help in enriching the transcriptomic resources implicated in understanding of root nodulation events in chickpea.

  11. Dissecting the Root Nodule Transcriptome of Chickpea (Cicer arietinum L.)

    PubMed Central

    Kant, Chandra; Pradhan, Seema; Bhatia, Sabhyata

    2016-01-01

    A hallmark trait of chickpea (Cicer arietinum L.), like other legumes, is the capability to convert atmospheric nitrogen (N2) into ammonia (NH3) in symbiotic association with Mesorhizobium ciceri. However, the complexity of molecular networks associated with the dynamics of nodule development in chickpea need to be analyzed in depth. Hence, in order to gain insights into the chickpea nodule development, the transcriptomes of nodules at early, middle and late stages of development were sequenced using the Roche 454 platform. This generated 490.84 Mb sequence data comprising 1,360,251 reads which were assembled into 83,405 unigenes. Transcripts were annotated using Gene Ontology (GO), Cluster of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways analysis. Differential expression analysis revealed that a total of 3760 transcripts were differentially expressed in at least one of three stages, whereas 935, 117 and 2707 transcripts were found to be differentially expressed in the early, middle and late stages of nodule development respectively. MapMan analysis revealed enrichment of metabolic pathways such as transport, protein synthesis, signaling and carbohydrate metabolism during root nodulation. Transcription factors were predicted and analyzed for their differential expression during nodule development. Putative nodule specific transcripts were identified and enriched for GO categories using BiNGO which revealed many categories to be enriched during nodule development, including transcription regulators and transporters. Further, the assembled transcriptome was also used to mine for genic SSR markers. In conclusion, this study will help in enriching the transcriptomic resources implicated in understanding of root nodulation events in chickpea. PMID:27348121

  12. Proteomics and Metabolomics: Two Emerging Areas for Legume Improvement

    PubMed Central

    Ramalingam, Abirami; Kudapa, Himabindu; Pazhamala, Lekha T.; Weckwerth, Wolfram; Varshney, Rajeev K.

    2015-01-01

    The crop legumes such as chickpea, common bean, cowpea, peanut, pigeonpea, soybean, etc. are important sources of nutrition and contribute to a significant amount of biological nitrogen fixation (>20 million tons of fixed nitrogen) in agriculture. However, the production of legumes is constrained due to abiotic and biotic stresses. It is therefore imperative to understand the molecular mechanisms of plant response to different stresses and identify key candidate genes regulating tolerance which can be deployed in breeding programs. The information obtained from transcriptomics has facilitated the identification of candidate genes for the given trait of interest and utilizing them in crop breeding programs to improve stress tolerance. However, the mechanisms of stress tolerance are complex due to the influence of multi-genes and post-transcriptional regulations. Furthermore, stress conditions greatly affect gene expression which in turn causes modifications in the composition of plant proteomes and metabolomes. Therefore, functional genomics involving various proteomics and metabolomics approaches have been obligatory for understanding plant stress tolerance. These approaches have also been found useful to unravel different pathways related to plant and seed development as well as symbiosis. Proteome and metabolome profiling using high-throughput based systems have been extensively applied in the model legume species, Medicago truncatula and Lotus japonicus, as well as in the model crop legume, soybean, to examine stress signaling pathways, cellular and developmental processes and nodule symbiosis. Moreover, the availability of protein reference maps as well as proteomics and metabolomics databases greatly support research and understanding of various biological processes in legumes. Protein-protein interaction techniques, particularly the yeast two-hybrid system have been advantageous for studying symbiosis and stress signaling in legumes. In this review, several

  13. Proteomics and Metabolomics: Two Emerging Areas for Legume Improvement.

    PubMed

    Ramalingam, Abirami; Kudapa, Himabindu; Pazhamala, Lekha T; Weckwerth, Wolfram; Varshney, Rajeev K

    2015-01-01

    The crop legumes such as chickpea, common bean, cowpea, peanut, pigeonpea, soybean, etc. are important sources of nutrition and contribute to a significant amount of biological nitrogen fixation (>20 million tons of fixed nitrogen) in agriculture. However, the production of legumes is constrained due to abiotic and biotic stresses. It is therefore imperative to understand the molecular mechanisms of plant response to different stresses and identify key candidate genes regulating tolerance which can be deployed in breeding programs. The information obtained from transcriptomics has facilitated the identification of candidate genes for the given trait of interest and utilizing them in crop breeding programs to improve stress tolerance. However, the mechanisms of stress tolerance are complex due to the influence of multi-genes and post-transcriptional regulations. Furthermore, stress conditions greatly affect gene expression which in turn causes modifications in the composition of plant proteomes and metabolomes. Therefore, functional genomics involving various proteomics and metabolomics approaches have been obligatory for understanding plant stress tolerance. These approaches have also been found useful to unravel different pathways related to plant and seed development as well as symbiosis. Proteome and metabolome profiling using high-throughput based systems have been extensively applied in the model legume species, Medicago truncatula and Lotus japonicus, as well as in the model crop legume, soybean, to examine stress signaling pathways, cellular and developmental processes and nodule symbiosis. Moreover, the availability of protein reference maps as well as proteomics and metabolomics databases greatly support research and understanding of various biological processes in legumes. Protein-protein interaction techniques, particularly the yeast two-hybrid system have been advantageous for studying symbiosis and stress signaling in legumes. In this review, several

  14. Different Pathways Act Downstream of the CEP Peptide Receptor CRA2 to Regulate Lateral Root and Nodule Development1[OPEN

    PubMed Central

    Mohd-Radzman, Nadiatul A.; Ivanovici, Ariel; Frugier, Florian; Djordjevic, Michael A.

    2016-01-01

    C-TERMINALLY ENCODED PEPTIDEs (CEPs) control root system architecture in a non-cell-autonomous manner. In Medicago truncatula, MtCEP1 affects root development by increasing nodule formation and inhibiting lateral root emergence by unknown pathways. Here, we show that the MtCEP1 peptide-dependent increase in nodulation requires the symbiotic signaling pathway and ETHYLENE INSENSITIVE2 (EIN2)/SICKLE (SKL), but acts independently of SUPER NUMERIC NODULES. MtCEP1-dependent inhibition of lateral root development acts through an EIN2-independent mechanism. MtCEP1 increases nodulation by promoting rhizobial infections, the developmental competency of roots for nodulation, the formation of fused nodules, and an increase in frequency of nodule development that initiates at proto-phloem poles. These phenotypes are similar to those of the ein2/skl mutant and support that MtCEP1 modulates EIN2-dependent symbiotic responses. Accordingly, MtCEP1 counteracts the reduction in nodulation induced by increasing ethylene precursor concentrations, and an ethylene synthesis inhibitor treatment antagonizes MtCEP1 root phenotypes. MtCEP1 also inhibits the development of EIN2-dependent pseudonodule formation. Finally, mutants affecting the COMPACT ROOT ARCHITECTURE2 (CRA2) receptor, which is closely related to the Arabidopsis CEP Receptor1, are unresponsive to MtCEP1 effects on lateral root and nodule formation, suggesting that CRA2 is a CEP peptide receptor mediating both organogenesis programs. In addition, an ethylene inhibitor treatment counteracts the cra2 nodulation phenotype. These results indicate that MtCEP1 and its likely receptor, CRA2, mediate nodulation and lateral root development through different pathways. PMID:27342310

  15. Characteristics of bacteroids in indeterminate nodules of the leguminous tree Leucaena glauca.

    PubMed

    Ishihara, Hironobu; Koriyama, Hiroki; Osawa, Atsushi; Zehirov, Grigor; Yamaura, Masatoshi; Kucho, Ken-ichi; Abe, Mikiko; Higashi, Shiro; Kondorosi, Eva; Mergaert, Peter; Uchiumi, Toshiki

    2011-01-01

    Rhizobia establish symbiosis with legumes. Bacteroids in indeterminate nodules of Inverted Repeat Lacking Clade (IRLC) legumes undergo terminal differentiation caused by Nodule-specific Cysteine-Rich peptides (NCRs). Microscopic observations of bacteroids and the detection of NCRs in indeterminate nodules of the non-IRLC legume Leucaena glauca were performed. A portion of the bacteroids showed moderate cell elongation, loss of membrane integrity, and multiple nucleoids. The symbiosome contained multiple bacteroids and NCR-like peptides were not detectable. These results indicate that bacteroid differentiation in L. glauca is different from that in IRLC legumes although both hosts form indeterminate nodules.

  16. Polyphenol oxidase affects normal nodule development in red clover (Trifolium pratense L.)

    USDA-ARS?s Scientific Manuscript database

    Polyphenol oxidase (PPO) may have multiple functions in tissues, depending on its cellular or tissue localization. We used PPO RNAi transformants of red clover (Trifolium pratense) to determine the role PPO plays in normal development of plants, and especially in nitrogen-fixing nodules. In red clov...

  17. Comparative transcriptome analysis of nodules of two Mesorhizobium-chickpea associations with differential symbiotic efficiency under phosphate deficiency.

    PubMed

    Nasr Esfahani, Maryam; Inoue, Komaki; Chu, Ha Duc; Nguyen, Kien Huu; Van Ha, Chien; Watanabe, Yasuko; Burritt, David J; Herrera-Estrella, Luis; Mochida, Keiichi; Tran, Lam-Son Phan

    2017-09-01

    Phosphate (Pi) deficiency is known to be a major limitation for symbiotic nitrogen fixation (SNF), and hence legume crop productivity globally. However, very little information is available on the adaptive mechanisms, particularly in the important legume crop chickpea (Cicer arietinum L.), which enable nodules to respond to low-Pi availability. Thus, to elucidate these mechanisms in chickpea nodules at molecular level, we used an RNA sequencing approach to investigate transcriptomes of the nodules in Mesorhizobium mediterraneum SWRI9-(MmSWRI9)-chickpea and M. ciceri CP-31-(McCP-31)-chickpea associations under Pi-sufficient and Pi-deficient conditions, of which the McCP-31-chickpea association has a better SNF capacity than the MmSWRI9-chickpea association during Pi starvation. Our investigation revealed that more genes showed altered expression patterns in MmSWRI9-induced nodules than in McCP-31-induced nodules (540 vs. 225) under Pi deficiency, suggesting that the Pi-starvation-more-sensitive MmSWRI9-induced nodules required expression change in a larger number of genes to cope with low-Pi stress than the Pi-starvation-less-sensitive McCP-31-induced nodules. The functional classification of differentially expressed genes (DEGs) was examined to gain an understanding of how chickpea nodules respond to Pi starvation, caused by soil Pi deficiency. As a result, more DEGs involved in nodulation, detoxification, nutrient/ion transport, transcriptional factors, key metabolic pathways, Pi remobilization and signalling were found in Pi-starved MmSWRI9-induced nodules than in Pi-starved McCP-31-induced nodules. Our findings have enabled the identification of molecular processes that play important roles in the acclimation of nodules to Pi deficiency, ultimately leading to the development of Pi-efficient chickpea symbiotic associations suitable for Pi-deficient soils. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  18. Rhizobial synthesized cytokinins contribute to but are not essential for the symbiotic interaction between photosynthetic Bradyrhizobia and Aeschynomene legumes.

    PubMed

    Podlešáková, Kateřina; Fardoux, Joel; Patrel, Delphine; Bonaldi, Katia; Novák, Ondřej; Strnad, Miroslav; Giraud, Eric; Spíchal, Lukáš; Nouwen, Nico

    2013-10-01

    Cytokinins (CK) play an important role in the formation of nitrogen-fixing root nodules. It has been known for years that rhizobia secrete CK in the extracellular medium but whether they play a role in nodule formation is not known. We have examined this question using the photosynthetic Bradyrhizobium sp. strain ORS285 which is able to nodulate Aeschynomene afraspera and A. indica using a Nod-dependent or Nod-independent symbiotic process, respectively. CK profiling showed that the most abundant CK secreted by Bradyrhizobium sp. strain ORS285 are the 2MeS (2-methylthiol) derivatives of trans-zeatin and isopentenyladenine. In their pure form, these CK can activate legume CK receptors in vitro, and their exogenous addition induced nodule-like structures on host plants. Deletion of the miaA gene showed that transfer RNA degradation is the source of CK production in Bradyrhizobium sp. strain ORS285. In nodulation studies performed with A. indica and A. afraspera, the miaA mutant had a 1-day delay in nodulation and nitrogen fixation. Moreover, A. indica plants formed considerably smaller but more abundant nodules when inoculated with the miaA mutant. These data show that CK produced by Bradyrhizobium sp. strain ORS285 are not the key signal triggering nodule formation during the Nod-independent symbiosis but they contribute positively to nodule development in Aeschynomene plants.

  19. Nodulation outer proteins: double-edged swords of symbiotic rhizobia

    USDA-ARS?s Scientific Manuscript database

    Rhizobia are nitrogen-fixing bacteria that establish a nodule symbiosis with legumes. Nodule formation is the result of a complex bacterial infection process, which depends on signals and surface determinants produced by both symbiotic partners. Among them, rhizobial nodulation outer proteins (Nops)...

  20. Recent developments in video-assisted thoracoscopic surgery for pulmonary nodule management

    PubMed Central

    Chow, Simon C. Y.

    2016-01-01

    In the modern era when screening and early surveillance of pulmonary nodules is increasing in importance, the management of the pulmonary nodule represents a different challenge to thoracic surgeons. The difficulty lies in the merging of sound surgical and oncological principles with more minimally invasive and appropriate lung sparing surgery. Furthermore, the intra-operative identification and surgical management of small and sometimes multi-focal pulmonary lesions remain challenging. There have been many developments and innovations in the field of video-assisted thoracoscopic surgery (VATS) to cater for the demands from increasing incidence of pulmonary nodules with associated paradigm shift in their surgical management. Recently, uniportal VATS and non-intubated VATS represent an even less invasive alternative to the conventional multiport VATS. The emergence of image guided VATS, hybrid operating theatre and fluorescence thoracoscopy have all contributed to improved precision of VATS lung resection, and are becoming important adjuncts to lung sparing surgery. In this chapter, some of these recent developments in VATS with emphasize on their importance in surgical management of the pulmonary nodule will be discussed. PMID:27606081

  1. Rapeseed-legume intercrops: plant growth and nitrogen balance in early stages of growth and development.

    PubMed

    Génard, Thaïs; Etienne, Philippe; Diquélou, Sylvain; Yvin, Jean-Claude; Revellin, Cécile; Laîné, Philippe

    2017-03-01

    In this study we tested whether legumes can improve the growth and N and S nutrition of rapeseed in an intercropping system and compared the effect of mixtures on legume N-fixation and soil N-resources. Rapeseed was cultivated in low N conditions in monocrops using one (R) or two plants (RR) per pot and in mixtures with lupine, clover or vetch. The R monocrop was the most relevant control, intraspecific competition inducing a significant growth delay resulting in a significantly lower leaf number, in RR monocrop compared to R and the three mixtures considered. Plant biomass, and the N and S contents of rapeseed grown in mixtures were the same than those measured in R monocrop. Compared to the monocrop, the proportion of N derived from the atmosphere was increased by 34, 140 and 290% in lupine, clover and vetch, respectively when intercropped with rapeseed. In mixture with clover and lupine, the soil N pool at harvest was higher than in other treatments, while N export by crop was constant. Legumes suffered from competition for soil S resulting in a decrease of 40% in their S content compared to the monocrop. Compared to rapeseeds grown in R monocrop and in mixture with lupine and vetch, rapeseed mixed with clover showed significantly higher SPAD values in old leaves. In our conditions, mixing legumes with rapeseed is relevant to reduce N fertilization and improve nutrition and growth of rapeseed.

  2. High intensity, short duration rotational grazing on reclaimed cool season fescue/legume pastures: I. System development

    SciTech Connect

    Erickson, W.R.; Carlson, K.E.

    1995-09-01

    The Pittsburg & Midway Coal Mining Co.`s ({open_quotes}P&M{close_quotes}) Midway Mine lies 50 miles south of Kansas City, Kansas, straddling the border of Kansas and Missouri. P&M actively mined the area until 1989, when the mine was closed and reclaimed. Approximately 3,750 acres of surface mined land were topsoiled and revegetated to cool season fescue/legume pasture. Various pasture management methods are being utilized to meet reclamation success standards and achieve final bond release. The effectiveness and costs of various cool season fescue/legume pasture management methods are evaluated and contrasted. These methods include sharecropping, bush hogging, burning and livestock grazing. It presents guidelines used to develop a site specific rotational livestock grazing programs with land owners or contractors, and local, state and federal agencies. Rotational grazing uses both cow/calf or feeder livestock operations. Key managerial elements used to control grazing activities, either by the landowner or a contractor, are reviewed. Methods used to determine stocking levels for successful rotational grazing on this type of pasture are presented. Rotational grazing of livestock has proven to be the most effective method for managing established cool season fescue/legume pastures at this site. Initial stocking rates of 1 A.U.M. per 5 acres have been modified to a current stocking rate of 1 A.U.M. per 2.5 acres. Supporting physical and chemical data are presented and discussed.

  3. The role of nodules in the tolerance of common bean to iron deficiency.

    PubMed

    Slatni, Tarek; Ben Salah, Imen; Kouas, Saber; Abdelly, Chedly

    2014-05-01

    Iron is vital for the establishment and function of symbiotic root nodules of legumes. Although abundant in the environment, Fe is often a limiting nutrient for plant growth due to its low solubility and availability in some soils. We have studied the mechanism of iron uptake in the root nodules of common bean to evaluate the role of nodules in physiological responses to iron deficiency. Based on experiments using full or partial submergence of nodulated roots in the nutrient solution, our results show that the nodules were affected only slightly under iron deficiency, especially when the nodules were submerged in nutrient solution in the tolerant cultivar. In addition, fully submerged root nodules showed enhanced acidification of the nutrient solution and showed higher ferric chelate reductase activity than that of partially submerged roots in plants cultivated under Fe deficiency. The main results obtained in this work suggest that in addition to preferential Fe allocation from the root system to the nodules, this symbiotic organ probably develops some mechanisms to respond to iron deficiency. These mechanisms were implied especially in nodule Fe absorption efficiency and in the ability of this organ to take up Fe directly from the medium.

  4. Introduction of a novel pathway for IAA biosynthesis to rhizobia alters vetch root nodule development.

    PubMed

    Camerini, Serena; Senatore, Beatrice; Lonardo, Enza; Imperlini, Esther; Bianco, Carmen; Moschetti, Giancarlo; Rotino, Giuseppe L; Campion, Bruno; Defez, Roberto

    2008-07-01

    We introduced into Rhizobium leguminosarum bv. viciae LPR1105 a new pathway for the biosynthesis of the auxin, indole-3-acetic acid (IAA), under the control of a stationary phase-activated promoter active both in free-living bacteria and bacteroids. The newly introduced genes are the iaaM gene from Pseudomonas savastanoi and the tms2 gene from Agrobacterium tumefaciens. Free-living bacteria harbouring the promoter-iaaMtms2 construct release into the growth medium 14-fold more IAA than the wild-type parental strain. This IAA overproducing R. l. viciae, the RD20 strain, elicits the development of vetch root nodules containing up to 60-fold more IAA than nodules infected by the wild-type strain LPR1105. Vetch root nodules derived from RD20 are fewer in number per plant, heavier in terms of dry weight and show an enlarged and more active meristem. A significant increase in acetylene reduction activity was measured in nodules elicited in vetch by RD20.

  5. Metabolomic Profiling of Bradyrhizobium diazoefficiens-Induced Root Nodules Reveals Both Host Plant-Specific and Developmental Signatures

    PubMed Central

    Lardi, Martina; Murset, Valérie; Fischer, Hans-Martin; Mesa, Socorro; Ahrens, Christian H.; Zamboni, Nicola; Pessi, Gabriella

    2016-01-01

    Bradyrhizobium diazoefficiens is a nitrogen-fixing endosymbiont, which can grow inside root-nodule cells of the agriculturally important soybean and other host plants. Our previous studies described B. diazoefficiens host-specific global expression changes occurring during legume infection at the transcript and protein level. In order to further characterize nodule metabolism, we here determine by flow injection–time-of-flight mass spectrometry analysis the metabolome of (i) nodules and roots from four different B. diazoefficiens host plants; (ii) soybean nodules harvested at different time points during nodule development; and (iii) soybean nodules infected by two strains mutated in key genes for nitrogen fixation, respectively. Ribose (soybean), tartaric acid (mungbean), hydroxybutanoyloxybutanoate (siratro) and catechol (cowpea) were among the metabolites found to be specifically elevated in one of the respective host plants. While the level of C4-dicarboxylic acids decreased during soybean nodule development, we observed an accumulation of trehalose-phosphate at 21 days post infection (dpi). Moreover, nodules from non-nitrogen-fixing bacteroids (nifA and nifH mutants) showed specific metabolic alterations; these were also supported by independent transcriptomics data. The alterations included signs of nitrogen limitation in both mutants, and an increased level of a phytoalexin in nodules induced by the nifA mutant, suggesting that the tissue of these nodules exhibits defense and stress reactions. PMID:27240350

  6. [Characterization of rhizobia causing nodules on leguminous trees native to Uruguay using the rep-PCR technique].

    PubMed

    Rodríguez, A; Frioni, L

    2003-01-01

    Methods for identifying and following microorganisms in the environment such as soils, water and plant association have been highly developed in recent years. In this study, we used rep-PCR for the characterization of Rhizobium bacteria isolated from legume trees native of Uruguay which permitted to follow them in plant inoculation assays. Among the primers used, ERIC and BOX1AR, the latter allowed the differentiation of isolates from different legumes and the finding of a high level of homology among rhizobia that nodulate the same legume species. Besides, it demonstrated that the profiles of the isolates recovered from nodules of Acacia caven, were identical to the ones used as inoculants; this confirmed the efficiency of these methods to follow these diazotrophs in the environment.

  7. Functional Implication of β-Carotene Hydroxylases in Soybean Nodulation1[C][W][OA

    PubMed Central

    Kim, Yun-Kyoung; Kim, Sunghan; Um, Ji-Hyun; Kim, Kyunga; Choi, Sun-Kang; Um, Byung-Hun; Kang, Suk-Woo; Kim, Jee-Woong; Takaichi, Shinichi; Song, Seok-Bo; Lee, Choon-Hwan; Kim, Ho-Seung; Kim, Ki Woo; Nam, Kyoung Hee; Lee, Suk-Ha; Kim, Yul-Ho; Park, Hyang-Mi; Ha, Sun-Hwa; Verma, Desh Pal S.; Cheon, Choong-Ill

    2013-01-01

    Legume-Rhizobium spp. symbiosis requires signaling between the symbiotic partners and differential expression of plant genes during nodule development. Previously, we cloned a gene encoding a putative β-carotene hydroxylase (GmBCH1) from soybean (Glycine max) whose expression increased during nodulation with Bradyrhizobium japonicum. In this work, we extended our study to three GmBCHs to examine their possible role(s) in nodule development, as they were additionally identified as nodule specific, along with the completion of the soybean genome. In situ hybridization revealed the expression of three GmBCHs (GmBCH1, GmBCH2, and GmBCH3) in the infected cells of root nodules, and their enzymatic activities were confirmed by functional assays in Escherichia coli. Localization of GmBCHs by transfecting Arabidopsis (Arabidopsis thaliana) protoplasts with green fluorescent protein fusions and by electron microscopic immunogold detection in soybean nodules indicated that GmBCH2 and GmBCH3 were present in plastids, while GmBCH1 appeared to be cytosolic. RNA interference of the GmBCHs severely impaired nitrogen fixation as well as nodule development. Surprisingly, we failed to detect zeaxanthin, a product of GmBCH, or any other carotenoids in nodules. Therefore, we examined the possibility that most of the carotenoids in nodules are converted or cleaved to other compounds. We detected the expression of some carotenoid cleavage dioxygenases (GmCCDs) in wild-type nodules and also a reduced amount of zeaxanthin in GmCCD8-expressing E. coli, suggesting cleavage of the carotenoid. In view of these findings, we propose that carotenoids such as zeaxanthin synthesized in root nodules are cleaved by GmCCDs, and we discuss the possible roles of the carotenoid cleavage products in nodulation. PMID:23700351

  8. Cell- and Tissue-Specific Transcriptome Analyses of Medicago truncatula Root Nodules

    PubMed Central

    Limpens, Erik; Moling, Sjef; Hooiveld, Guido; Pereira, Patrícia A.; Bisseling, Ton; Becker, Jörg D.; Küster, Helge

    2013-01-01

    Legumes have the unique ability to host nitrogen-fixing Rhizobium bacteria as symbiosomes inside root nodule cells. To get insight into this key process, which forms the heart of the endosymbiosis, we isolated specific cells/tissues at different stages of symbiosome formation from nodules of the model legume Medicago truncatula using laser-capture microdissection. Next, we determined their associated expression profiles using Affymetrix Medicago GeneChips. Cells were collected from the nodule infection zone divided into a distal (where symbiosome formation and division occur) and proximal region (where symbiosomes are mainly differentiating), as well as infected cells from the fixation zone containing mature nitrogen fixing symbiosomes. As non-infected cells/tissue we included nodule meristem cells and uninfected cells from the fixation zone. Here, we present a comprehensive gene expression map of an indeterminate Medicago nodule and selected genes that show specific enriched expression in the different cells or tissues. Validation of the obtained expression profiles, by comparison to published gene expression profiles and experimental verification, indicates that the data can be used as digital “in situ”. This digital “in situ” offers a genome-wide insight into genes specifically associated with subsequent stages of symbiosome and nodule cell development, and can serve to guide future functional studies. PMID:23734198

  9. Aspartate Aminotransferase in Effective and Ineffective Alfalfa Nodules 1

    PubMed Central

    Gantt, J. Stephen; Larson, Ruby J.; Farnham, Mark W.; Pathirana, Sudam M.; Miller, Susan S.; Vance, Carroll P.

    1992-01-01

    Aspartate aminotransferase (AAT) is a key plant enzyme affecting nitrogen and carbon metabolism, particularly in legume root nodules and leaves of C4 species. To ascertain the molecular genetic characteristics and biochemical regulation of AAT, we have isolated a cDNA encoding the nodule-enhanced AAT (AAT-2) of alfalfa (Medicago sativa L.) by screening a root nodule cDNA expression library with antibodies. Complementation of an Escherichia coli AAT mutant with the alfalfa nodule AAT-2 cDNA verified the identity of the clone. The deduced amino acid sequence of alfalfa AAT-2 is 53 and 47% identical to animal mitochondrial and cytosolic AATs, respectively. The deduced molecular mass of AAT-2 is 50,959 daltons, whereas the mass of purified AAT-2 is about 40 kilodaltons as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the protein's N-terminal domain (amino acids 1-59) contains many of the characteristics of plastid-targeting peptides. We postulate that AAT-2 is localized to the plastid. Southern blot analysis suggests that AAT-2 is encoded by a small, multigene family. The expression of AAT-2 mRNA in nodules is severalfold greater than that in either leaves or roots. Northern and western blots showed that expression of AAT activity during effective nodule development is accompanied by a sevenfold increase in AAT-2 mRNA and a comparable increase in enzyme protein. By contrast, plant-controlled ineffective nodules express AAT-2 mRNA at much lower levels and have little to no AAT-2 enzyme protein. Expression of root nodule AAT-2 appears to be regulated by at least two events: the first is independent of nitrogenase activity; the second is associated with nodule effectiveness. ImagesFigure 3Figure 4Figure 5Figure 7Figure 8 PMID:16668758

  10. Assessing genotypic diversity and symbiotic efficiency of five rhizobial legume interactions under cadmium stress for soil phytoremediation.

    PubMed

    Guefrachi, I; Rejili, M; Mahdhi, M; Mars, M

    2013-01-01

    In the framework of soil phytoremediation using local legume plants coupled with their native root-nodulating bacteria to increase forage yields and preserve contaminated soils in arid regions of Tunisia, we investigated the diversity of bacteria from root nodules of Lathyrus sativus, Lens culinaris, Medicago marina, M. truncatula, and M. minima and the symbiotic efficiency of these five legume symbiosis under Cadmium stress. Fifty bacterial strains were characterized using physiological and biochemical features such heavy metals resistant, and PCR-RFLP of 16S rDNA. Taxonomically, the isolates nodulating L. sativus, and L. culinaris are species within the genera Rhizobium and the ones associated to Medicago sp, within the genera Sinorhizobium. The results revealed also that the cadmium tolerance of the different legumes-rhizobia interaction was as follows: M. minima < M. truncatula < M. marina < L. sativus < L. culinaris indicating that the effect of Cadmium on root nodulation and biomass production is more deleterious on M. minima-S. meliloti and M. truncatula-S. meliloti than in other symbiosis. Knowledge on genetic and functional diversity of M. marina, L. sativus and L. culinaris microsymbiotes is very useful for inoculant strain selection and can be selected to develop inoculants for soil phytoremediation.

  11. Identifying abnormalities in symbiotic development between Trifolium spp. and Rhizobium leguminosarum bv. trifolii leading to sub-optimal and ineffective nodule phenotypes

    PubMed Central

    Melino, V. J.; Drew, E. A.; Ballard, R. A.; Reeve, W. G.; Thomson, G.; White, R. G.; O'Hara, G. W.

    2012-01-01

    Background and Aims Legumes overcome nitrogen limitations by entering into a mutualistic symbiosis with N2-fixing bacteria (rhizobia). Fully compatible associations (effective) between Trifolium spp. and Rhizobium leguminosarum bv. trifolii result from successful recognition of symbiotic partners in the rhizosphere, root hair infection and the formation of nodules where N2-fixing bacteroids reside. Poorly compatible associations can result in root nodule formation with minimal (sub-optimal) or no (ineffective) N2-fixation. Despite the abundance and persistence of strains in agricultural soils which are poorly compatible with the commercially grown clover species, little is known of how and why they fail symbiotically. The aims of this research were to determine the morphological aberrations occurring in sub-optimal and ineffective clover nodules and to determine whether reduced bacteroid numbers or reduced N2-fixing activity is the main cause for the Sub-optimal phenotype. Methods Symbiotic effectiveness of four Trifolium hosts with each of four R. leguminosarum bv. trifolii strains was assessed by analysis of plant yields and nitrogen content; nodule yields, abundance, morphology and internal structure; and bacteroid cytology, quantity and activity. Key Results Effective nodules (Nodule Function 83–100 %) contained four developmental zones and N2-fixing bacteroids. In contrast, Sub-optimal nodules of the same age (Nodule Function 24–57 %) carried prematurely senescing bacteroids and a small bacteroid pool resulting in reduced shoot N. Ineffective-differentiated nodules carried bacteroids aborted at stage 2 or 3 in differentiation. In contrast, bacteroids were not observed in Ineffective-vegetative nodules despite the presence of bacteria within infection threads. Conclusions Three major responses to N2-fixation incompatibility between Trifolium spp. and R. l. trifolii strains were found: failed bacterial endocytosis from infection threads into plant cortical

  12. Effect of Co-Inoculation with Mycorrhiza and Rhizobia on the Nodule Trehalose Content of Different Bean Genotypes

    PubMed Central

    Ballesteros-Almanza, L; Altamirano-Hernandez, J; Peña-Cabriales, J.J; Santoyo, G; Sanchez-Yañez, J.M; Valencia-Cantero, E; Macias-Rodriguez, L; Lopez-Bucio, J; Cardenas-Navarro, R; Farias-Rodriguez, R

    2010-01-01

    Studies on Rhizobium-legume symbiosis show that trehalose content in nodules under drought stress correlates positively with an increase in plant tolerance to this stress. Fewer reports describe trehalose accumulation in mycorrhiza where, in contrast with rhizobia, there is no flux of carbohydrates from the microsymbiont to the plant. However, the trehalose dynamics in the Mycorrhiza-Rhizobium-Legume tripartite symbiosis is unknown. The present study explores the role of this tripartite symbiosis in the trehalose content of nodules grown under contrasting moisture conditions. Three wild genotypes (P. filiformis, P. acutifolis and P. vulgaris) and two commercial genotypes of Phaseolus vulgaris (Pinto villa and Flor de Mayo) were used. Co-inoculation treatments were conducted with Glomus intraradices and a mixture of seven native rhizobial strains, and trehalose content was determined by GC/MS. The results showed a negative effect of mycorrhizal inoculation on nodule development, as mycorrhized plants showed fewer nodules and lower nodule dry weight compared to plants inoculated only with Rhizobium. Mycorrhizal colonization was also higher in plants inoculated only with Glomus as compared to plants co-inoculated with both microsymbionts. In regard to trehalose, co-inoculation negatively affects its accumulation in the nodules of each genotype tested. However, the correlation analysis showed a significantly positive correlation between mycorrhizal colonization and nodule trehalose content. PMID:21253462

  13. The REL3-mediated TAS3 ta-siRNA pathway integrates auxin and ethylene signaling to regulate nodulation in Lotus japonicus.

    PubMed

    Li, Xiaolin; Lei, Mingjuan; Yan, Zhongyuan; Wang, Qi; Chen, Aimin; Sun, Jie; Luo, Da; Wang, Yanzhang

    2014-01-01

    The ta-siRNA pathway is required for lateral organ development, including leaf patterning, flower differentiation and lateral root growth. Legumes can develop novel lateral root organs--nodules--resulting from symbiotic interactions with rhizobia. However, ta-siRNA regulation in nodule formation remains unknown. To explore ta-siRNA regulation in nodule formation, we investigated the roles of REL3, a key component of TAS3 ta-siRNA biogenesis, during nodulation in Lotus japonicus. We characterized the symbiotic phenotypes of the TAS3 ta-siRNA defective rel3 mutant, and analyzed the responses of the rel3 mutant to auxin and ethylene in order to gain insight into TAS3 ta-siRNA regulation of nodulation. The rel3 mutant produced fewer pink nitrogen-fixing nodules, with substantially decreased infection frequency and nodule initiation. Moreover, the rel3 mutant was more resistant than wild-type to 1-naphthaleneacetic acid (NAA) and N-1-naphthylphthalamic acid (NPA) in root growth, and exhibited insensitivity to auxins but greater sensitivity to auxin transport inhibitors during nodulation. Furthermore, the rel3 mutant has enhanced root-specific ethylene sensitivity and altered responses to ethylene during nodulation; the low-nodulating phenotype of the rel3 mutant can be restored by ethylene synthesis inhibitor L-α-(2-aminoethoxyvinyl)-glycine (AVG) or action inhibitor Ag(+). The REL3-mediated TAS3 ta-siRNA pathway regulates nodulation by integrating ethylene and auxin signaling.

  14. Determinants of nodulation competitiveness in Rhizobium etli. Final report for period September 30, 1996--September 29, 1999

    SciTech Connect

    Handelsman, Jo

    2000-01-04

    Nitrogen is a major limiting nutrient in crop production. Chemical fertilizers, which are used extensively to meet crop nitrogen requirements, contribute to the high energy inputs of modern agriculture and cause human health and environmental problems. Legumes and their bacterial associates have long been used in crop rotations to replenish soil nitrogen, but effective and reliable biological nitrogen fixation for beans is prevented by the lack of nodulation competitiveness of many Rhizobium strains used as inoculants. The result is that the inoculant strains will not occupy the host's nodules and no benefit will be derived from inoculation. Many indigenous soil strains of Rhizobium etli bv. phaseoli, the symbiont of bean, nodulate but fix little or no nitrogen, and therefore the nodulation competitiveness problem is significant for achieving maximum nitrogen benefit from bean crops. This project was directed toward developing an understanding of the basis of nodulation competitiveness.

  15. Strigolactones promote nodulation in pea.

    PubMed

    Foo, Eloise; Davies, Noel W

    2011-11-01

    Strigolactones are recently defined plant hormones with roles in mycorrhizal symbiosis and shoot and root architecture. Their potential role in controlling nodulation, the related symbiosis between legumes and Rhizobium bacteria, was explored using the strigolactone-deficient rms1 mutant in pea (Pisum sativum L.). This work indicates that endogenous strigolactones are positive regulators of nodulation in pea, required for optimal nodule number but not for nodule formation per se. rms1 mutant root exudates and root tissue are almost completely deficient in strigolactones, and rms1 mutant plants have approximately 40% fewer nodules than wild-type plants. Treatment with the synthetic strigolactone GR24 elevated nodule number in wild-type pea plants and also elevated nodule number in rms1 mutant plants to a level similar to that seen in untreated wild-type plants. Grafting studies revealed that nodule number and strigolactone levels in root tissue of rms1 roots were unaffected by grafting to wild-type scions indicating that strigolactones in the root, but not shoot-derived factors, regulate nodule number and provide the first direct evidence that the shoot does not make a major contribution to root strigolactone levels.

  16. Transient Nod factor-dependent gene expression in the nodulation-competent zone of soybean (Glycine max [L.] Merr.) roots.

    PubMed

    Hayashi, Satomi; Reid, Dugald E; Lorenc, Michał T; Stiller, Jiri; Edwards, David; Gresshoff, Peter M; Ferguson, Brett J

    2012-10-01

    All lateral organ development in plants, such as nodulation in legumes, requires the temporal and spatial regulation of genes and gene networks. A total mRNA profiling approach using RNA-seq to target the specific soybean (Glycine max) root tissues responding to compatible rhizobia [i.e. the Zone Of Nodulation (ZON)] revealed a large number of novel, often transient, mRNA changes occurring during the early stages of nodulation. Focusing on the ZON enabled us to discard the majority of root tissues and their developmentally diverse gene transcripts, thereby highlighting the lowly and transiently expressed nodulation-specific genes. It also enabled us to concentrate on a precise moment in early nodule development at each sampling time. We focused on discovering genes regulated specifically by the Bradyrhizobium-produced Nod factor signal, by inoculating roots with either a competent wild-type or incompetent mutant (nodC(-) ) strain of Bradyrhizobium japonicum. Collectively, 2915 genes were identified as being differentially expressed, including many known soybean nodulation genes. A number of unknown nodulation gene candidates and soybean orthologues of nodulation genes previously reported in other legume species were also identified. The differential expression of several candidates was confirmed and further characterized via inoculation time-course studies and qRT-PCR. The expression of many genes, including an endo-1,4-β-glucanase, a cytochrome P450 and a TIR-LRR-NBS receptor kinase, was transient, peaking quickly during the initiation of nodule ontogeny. Additional genes were found to be down-regulated. Significantly, a set of differentially regulated genes acting in the gibberellic acid (GA) biosynthesis pathway was discovered, suggesting a novel role of GAs in nodulation. © 2012 The Authors. Plant Biotechnology Journal © 2012 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd.

  17. Secretion systems and signal exchange between nitrogen-fixing rhizobia and legumes.

    PubMed

    Nelson, Matthew S; Sadowsky, Michael J

    2015-01-01

    The formation of symbiotic nitrogen-fixing nodules on the roots and/or stem of leguminous plants involves a complex signal exchange between both partners. Since many microorganisms are present in the soil, legumes and rhizobia must recognize and initiate communication with each other to establish symbioses. This results in the formation of nodules. Rhizobia within nodules exchange fixed nitrogen for carbon from the legume. Symbiotic relationships can become non-beneficial if one partner ceases to provide support to the other. As a result, complex signal exchange mechanisms have evolved to ensure continued, beneficial symbioses. Proper recognition and signal exchange is also the basis for host specificity. Nodule formation always provides a fitness benefit to rhizobia, but does not always provide a fitness benefit to legumes. Therefore, legumes have evolved a mechanism to regulate the number of nodules that are formed, this is called autoregulation of nodulation. Sequencing of many different rhizobia have revealed the presence of several secretion systems - and the Type III, Type IV, and Type VI secretion systems are known to be used by pathogens to transport effector proteins. These secretion systems are also known to have an effect on host specificity and are a determinant of overall nodule number on legumes. This review focuses on signal exchange between rhizobia and legumes, particularly focusing on the role of secretion systems involved in nodule formation and host specificity.

  18. Secretion systems and signal exchange between nitrogen-fixing rhizobia and legumes

    PubMed Central

    Nelson, Matthew S.; Sadowsky, Michael J.

    2015-01-01

    The formation of symbiotic nitrogen-fixing nodules on the roots and/or stem of leguminous plants involves a complex signal exchange between both partners. Since many microorganisms are present in the soil, legumes and rhizobia must recognize and initiate communication with each other to establish symbioses. This results in the formation of nodules. Rhizobia within nodules exchange fixed nitrogen for carbon from the legume. Symbiotic relationships can become non-beneficial if one partner ceases to provide support to the other. As a result, complex signal exchange mechanisms have evolved to ensure continued, beneficial symbioses. Proper recognition and signal exchange is also the basis for host specificity. Nodule formation always provides a fitness benefit to rhizobia, but does not always provide a fitness benefit to legumes. Therefore, legumes have evolved a mechanism to regulate the number of nodules that are formed, this is called autoregulation of nodulation. Sequencing of many different rhizobia have revealed the presence of several secretion systems - and the Type III, Type IV, and Type VI secretion systems are known to be used by pathogens to transport effector proteins. These secretion systems are also known to have an effect on host specificity and are a determinant of overall nodule number on legumes. This review focuses on signal exchange between rhizobia and legumes, particularly focusing on the role of secretion systems involved in nodule formation and host specificity. PMID:26191069

  19. Interaction between Orobanche crenata and its Host Legumes: Unsuccessful Haustorial Penetration and Necrosis of the Developing Parasite

    PubMed Central

    PÉREZ-DE-LUQUE, A.; RUBIALES, D.; CUBERO, J. I.; PRESS, M. C.; SCHOLES, J.; YONEYAMA, K.; TAKEUCHI, Y.; PLAKHINE, D.; JOEL, D. M.

    2005-01-01

    • Background and Aims Orobanche species represent major constraints to crop production in many parts of the world as they reduce yield and alter root/shoot allometry. Although much is known about the histology and effect of Orobanche spp. on susceptible hosts, less is known about the basis of host resistance to these parasites. In this work, histological aspects related to the resistance of some legumes to Orobanche crenata have been investigated in order to determine which types of resistance responses are involved in the unsuccessful penetration of O. crenata. • Methods Samples of resistance reactions against O. crenata on different genotypes of resistant legumes were collected. The samples were fixed, sectioned and stained using different procedures. Sections were observed using a transmission light microscope and by epi-fluorescence. • Key Results Lignification of endodermal and pericycle host cells seems to prevent parasite intrusion into the root vascular cylinder at early infection stages. But in other cases, established tubercles became necrotic and died. Contrary to some previous studies, it was found that darkening at the infection site in these latter cases does not correspond to death of host tissues, but to the secretion of substances that fill the apoplast in the host–parasite interface and in much of the infected host tissues. The secretions block neighbouring host vessels. This may interfere with the nutrient flux between host and parasite, and may lead to necrosis and death of the developing parasite. • Conclusions The unsuccessful penetration of O. crenata seedlings into legume roots cannot be attributed to cell death in the host. It seems to be associated with lignification of host endodermis and pericycle cells at the penetration site. The accumulation of secretions at the infection site, may lead to the activation of xylem occlusion, another defence mechanism, which may cause further necrosis of established tubercles. PMID:15749751

  20. Molecular cloning of the BLADE-ON-PETIOLE gene and expression analyses during nodule development in Lupinus luteus.

    PubMed

    Frankowski, Kamil; Wilmowicz, Emilia; Kućko, Agata; Zienkiewicz, Agnieszka; Zienkiewicz, Krzysztof; Kopcewicz, Jan

    2015-05-01

    The BLADE-ON-PETIOLE (BOP) genes have been recently shown to play an essential role in many physiological processes, including embryogenesis, meristem determinacy, leaf patterning and nodule development. In our research we used Lupinus luteus, a plant with great agronomic potential due to its high protein content and nitrogen fixation ability. In this work, LlBOP in L. luteus was identified for the first time and its expression during nodule development was analyzed. The high expression levels of LlBOP and LlLbI (LEGHEMOGLOBIN), essential to nitrogen-fixing symbiosis, were noted in the developing root nodules and were correlated with the occurrence of leghemoglobin. All of these data indicate that LlBOP is an important regulator of root nodule formation and functioning in L. luteus. Copyright © 2015 Elsevier GmbH. All rights reserved.

  1. Development of a computerized scheme for detection of very subtle lung nodules located in opaque areas on chest radiographs

    NASA Astrophysics Data System (ADS)

    Shiraishi, Junji; Li, Qiang; Doi, Kunio

    2006-03-01

    The detection of lung nodules located in opaque areas including the mediastinum, retrocardiac lung, and lung projected below or on the diaphragm has been very difficult, because the contrast of these nodules is usually extremely low, and sometimes radiologists may not pay attention to these locations. In this study, we have developed a new computer-aided diagnostic (CAD) scheme designed specifically for the detection of these difficult-to-detect lung nodules located in opaque areas. We used 1,000 chest images with 1,076 lung nodules, which included 73 very difficult lung nodules in these opaque areas. In this new computerized scheme, opaque areas within a chest image were segmented by use of an adaptive multi-thresholding method based on edge-gradient values, and then the gray level and contrast of the chest image were adjusted for the opaque areas. Initial candidates were identified by use of the nodule-enhanced image obtained with the average radial-gradient (ARG) filtering technique based on radial gradient values. We employed a total of 35 image features for sequential application of artificial neural networks (ANNs) in order to reduce the number of false-positive candidates. The ANNs were trained and tested by use of a k-fold cross-validation test method (k=100), in which each of 100 different combinations of training and test image data sets included 990 and 10 chest images, respectively. The overall performance determined from the results of 100 test data sets indicated that the average sensitivity in detecting lung nodules was 52.1% with 1.89 false positives per image, which was considered "acceptable", because these nodules were very subtle and difficult to detect. By combination of this advanced CAD scheme with our standard CAD scheme for lung-nodule detection, the clinical usefulness of the CAD scheme would be improved significantly.

  2. Exploring genetic variability within lentil (Lens culinaris Medik.) and across related legumes using a newly developed set of microsatellite markers.

    PubMed

    Verma, Priyanka; Sharma, Tilak R; Srivastava, Prem S; Abdin, M Z; Bhatia, Sabhyata

    2014-09-01

    Lentil (Lens culinaris Medik.) is an economically important grain legume, yet the genetic and genomic resources remain largely uncharacterized and unexploited in this crop. Microsatellites have become markers of choice for crop improvement applications. Hence, simple sequence repeat (SSR) markers were developed for lentil through the construction of genomic library enriched for GA/CT motifs. As a result 122 functional SSR primer pairs were developed from 151 microsatellite loci and validated in L. culinaris cv. Precoz. Thirty three SSR markers were utilized for the analysis of genetic relationships between cultivated and wild species of Lens and related legumes. A total of 123 alleles were amplified at 33 loci ranging from 2-5 alleles with an average of 3.73 alleles per locus. Polymorphic information content (PIC) for all the loci ranged from 0.13 to 0.99 with an average of 0.66 per locus. Varied levels of cross genera transferability were obtained ranging from 69.70 % across Pisum sativum to 12.12 % across Vigna radiata. The UPGMA based dendrogram was able to establish the uniqueness of each genotype and grouped them into two major clusters clearly resolving the genetic relationships within lentil and related species. The new set of SSR markers reported here were efficient and highly polymorphic and would add to the existing repertoire of lentil SSR markers to be utilized in molecular breeding. Moreover, the improved knowledge about intra- and inter-specific genetic relationships would facilitate germplasm utilization for lentil improvement.

  3. Nitrogen Fixation, Nodule Development, and Vegetative Regrowth of Alfalfa (Medicago sativa L.) following Harvest 1

    PubMed Central

    Vance, Carroll P.; Heichel, Gary H.; Barnes, Donald K.; Bryan, Jeff W.; Johnson, Lois E.

    1979-01-01

    Nitrogenase-dependent acetylene reduction, nodule function, and nodule regrowth were studied during vegetative regrowth of harvested (detopped) alfalfa (Medicago sativa L.) seedlings grown in the glasshouse. Compared with controls, harvesting caused an 88% decline in acetylene reduction capacity of detached root systems within 24 hours. Acetylene reduction in harvested plants remained low for 13 days, then increased to a level comparable to the controls by day 18. Protease activity increased in nodules from harvested plants, reached a maximum at day 7 after harvest, and then declined to a level almost equal to the control by day 22 after harvest. Soluble protein and leghemoglobin decreased in nodules from harvested plants in an inverse relationship to protease activity. Nitrate reductase activity of nodules from harvested plants increased significantly within 24 hours and was inversely associated with acetylene reduction. The difference in nitrate reductase between nodules from harvested plants and control plants became less evident as shoot regrowth occurred and as acetylene reduction increased in the harvested plants. No massive loss of nodules occurred after harvest as evidenced by little net change in nodule fresh weight. There was, however, a rapid localized senescence which occurred in nodules of harvested plants. Histology of nodules from harvested plants showed that they degenerated at the proximal end after harvest. Starch in the nodule was depleted by 10 days after harvest. The meristem and vascular bundles of nodules from harvested plants remained intact. The senescent nodules began to regrow and fix nitrogen after shoot growth resumed. Images PMID:16660893

  4. Iron: an essential micronutrient for the legume-rhizobium symbiosis

    PubMed Central

    Brear, Ella M.; Day, David A.; Smith, Penelope M. C.

    2013-01-01

    Legumes, which develop a symbiosis with nitrogen-fixing bacteria, have an increased demand for iron. Iron is required for the synthesis of iron-containing proteins in the host, including the highly abundant leghemoglobin, and in bacteroids for nitrogenase and cytochromes of the electron transport chain. Deficiencies in iron can affect initiation and development of the nodule. Within root cells, iron is chelated with organic acids such as citrate and nicotianamine and distributed to other parts of the plant. Transport to the nitrogen-fixing bacteroids in infected cells of nodules is more complicated. Formation of the symbiosis results in bacteroids internalized within root cortical cells of the legume where they are surrounded by a plant-derived membrane termed the symbiosome membrane (SM). This membrane forms an interface that regulates nutrient supply to the bacteroid. Consequently, iron must cross this membrane before being supplied to the bacteroid. Iron is transported across the SM as both ferric and ferrous iron. However, uptake of Fe(II) by both the symbiosome and bacteroid is faster than Fe(III) uptake. Members of more than one protein family may be responsible for Fe(II) transport across the SM. The only Fe(II) transporter in nodules characterized to date is GmDMT1 (Glycine max divalent metal transporter 1), which is located on the SM in soybean. Like the root plasma membrane, the SM has ferric iron reductase activity. The protein responsible has not been identified but is predicted to reduce ferric iron accumulated in the symbiosome space prior to uptake by the bacteroid. With the recent publication of a number of legume genomes including Medicago truncatula and G. max, a large number of additional candidate transport proteins have been identified. Members of the NRAMP (natural resistance-associated macrophage protein), YSL (yellow stripe-like), VIT (vacuolar iron transporter), and ZIP (Zrt-, Irt-like protein) transport families show enhanced expression in

  5. Nodule-Specific Polypeptides from Effective Alfalfa Root Nodules and from Ineffective Nodules Lacking Nitrogenase 1

    PubMed Central

    Lang-Unnasch, Naomi; Ausubel, Frederick M.

    1985-01-01

    In addition to leghemoglobin, at least nine nodule-specific polypeptides from the alfalfa (Medicago sativa L.)-Rhizobium meliloti symbiosis were identified by immune assay. Some of these polypeptides may be subunits of larger proteins but none appeared to be subunits of the same multimeric protein. All nine of the nodule-specific polypeptides were localized to within the plant cytosol; they were not found in extracts of bacteroids or in the peribacteroid space. At least one of these nodule-specific polypeptides was found to be antigenically related to nodule-specific polypeptides in pea and/or soybean. Ineffective nodules elicited by R. meliloti strains containing mutations in four different genes required for nitrogenase synthesis contained reduced concentrations of leghemoglobin and of several of the nodule-specific polypeptides. Other nodule-specific polypeptides were unaltered or actually enriched in the ineffective nodules. Many of the differences between the ineffective and effective nodules were apparent in nodules harvested shortly after the nodules became visible. These differences were greatly amplified in older nodules. When the four ineffective nodule types were compared to one another, there were clear quantitative differences in the concentrations of several of the nodule-specific polypeptides. These differences suggest that lack of a functional nitrogenase does not have a single direct effect on nodule development. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 PMID:16664146

  6. A nonRD receptor-like kinase prevents nodule early senescence and defense-like reactions during symbiosis.

    PubMed

    Berrabah, Fathi; Bourcy, Marie; Eschstruth, Alexis; Cayrel, Anne; Guefrachi, Ibtissem; Mergaert, Peter; Wen, Jiangqi; Jean, Viviane; Mysore, Kirankumar S; Gourion, Benjamin; Ratet, Pascal

    2014-09-01

    Rhizobia and legumes establish symbiotic interactions leading to the production of root nodules, in which bacteria fix atmospheric nitrogen for the plant's benefit. This symbiosis is efficient because of the high rhizobia population within nodules. Here, we investigated how legumes accommodate such bacterial colonization. We used a reverse genetic approach to identify a Medicago truncatula gene, SymCRK, which encodes a cysteine-rich receptor-like kinase that is required for rhizobia maintenance within the plant cells, and performed detailed phenotypic analyses of the corresponding mutant. The Medicago truncatula symCRK mutant developed nonfunctional and necrotic nodules. A nonarginine asparate (nonRD) motif, typical of receptors involved in innate immunity, is present in the SymCRK kinase domain. Similar to the dnf2 mutant, bacteroid differentiation defect, defense-like reactions and early senescence were observed in the symCRK nodules. However, the dnf2 and symCRK nodules differ by their degree of colonization, which is higher in symCRK. Furthermore, in contrast to dnf2, symCRK is not a conditional mutant. These results suggest that in M. truncatula at least two genes are involved in the symbiotic control of immunity. Furthermore, phenotype differences between the two mutants suggest that two distinct molecular mechanisms control suppression of plant immunity during nodulation.

  7. Minor components in the sex pheromone of legume podborer: Maruca vitrata development of an attractive blend.

    PubMed

    Downham, M C A; Hall, D R; Chamberlain, D J; Cork, A; Farman, D I; Tamò, M; Dahounto, D; Datinon, B; Adetonah, S

    2003-04-01

    The legume podborer, Maruca vitrata (syn. M. testulalis) (F.) (Lepidoptera: Pyralidae) is a pantropical pest of legume crops. Sex pheromone was collected by gland extraction or trapping of volatiles from virgin female moths originating in India, West Africa, or Taiwan. Analysis by GC-EAG and GC-MS confirmed previously published findings that (E,E)-10,12-hexadecadienal is the most abundant EAG-active component with 2-5% of (E,E)-10,12-hexadecadienol also present. At least one other EAG response was detected at retention times typical of monounsaturated hexadecenals or tetradecenyl acetates, but neither could be detected by GC-MS. Laboratory wind-tunnel bioassays and a field bioassay of blends of (E,E)-10,12-hexadecadienal with (E,E )-10,12-hexadecadienol and a range of monounsaturated hexadecenal and tetradecenyl acetate isomers indicated greatest attraction of males was to those including (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal as minor components. In subsequent trapping experiments in cowpea fields in Benin, traps baited with a three-component blend of (E,E)-10,12-hexadecadienal and these two minor components in a 100:5:5 ratio caught significantly more males than traps baited with the major component alone, either two-component blend, or virgin female moths. Further blend optimization experiments did not produce a more attractive blend. No significant differences in catches were found between traps baited with polyethylene vials or rubber septa, or between lures containing 0.01 and 0.1 mg of synthetic pheromone. Significant numbers of female M. vitrata moths, up to 50% of total catches, were trapped with synthetic blends but not with virgin females. At present there is no clear explanation for this almost unprecedented finding, but the phenomenon may improve the predictive power of traps for population monitoring.

  8. Rhizobia from wild legumes: diversity, taxonomy, ecology, nitrogen fixation and biotechnology.

    PubMed

    Zahran, H H

    2001-10-04

    Wild legumes (herb or tree) are widely distributed in arid regions and actively contribute to soil fertility in these environments. The N2-fixing activity and tolerance to drastic conditions may be higher in wild legumes than in crop legumes. The wild legumes in arid zones harbor diverse and promiscuous rhizobia in their root-nodules. Specificity existed only in few rhizobia from wild legumes, however, the majority of them are with wide host range. Based on phenotypic characteristics and molecular techniques (protein profiles, polysaccharides, plasmids, DNA-DNA hybridization, 16SrRNA, etc.), the root-nodule bacteria that was isolated from wild legumes had been classified into four genera (Rhizobium, Bradyrhizobium, Mesorhizobium and Sinorhizobium). The rhizobia of wild legumes in arid zones, exhibit higher tolerance to the prevailing adverse conditions, e.g. salt stress, elevated temperatures and desiccation. These rhizobia may be used to inoculate wild, as well as, crop legumes, cultivated in reclaimed desert lands. Recent reports indicated that the wild-legume rhizobia formed successful symbioses with some grain legumes. Moreover, intercropping of some N2-fixing tree legumes (e.g. Lablab, Leucaena, Sesbania, etc.) to pasture grasses improved biomass yield and herb quality. In recent years, the rhizobia of wild legumes turn the attention of biotechnologists. These bacteria may have specific traits that can be transferred to other rhizobia through genetic engineering tools or used to produce industrially important compounds. Therefore, these bacteria are very important from both economic and environmental points of view.

  9. Genetics and mapping of quantitative traits for nodule number, weight, and size in soybean (Glycine max L. [Merr.])

    USDA-ARS?s Scientific Manuscript database

    Legume studies, including soybean, have reported that nodule traits, especially nodule biomass, are associated with N2 fixation ability. Two genotypes, differing in nodule number and individual nodule weight, KS4895 and Jackson, were mated and used to create 97 F3- and F5-derived RILs. The populatio...

  10. Two Direct Targets of Cytokinin Signaling Regulate Symbiotic Nodulation in Medicago truncatula[W][OA

    PubMed Central

    Ariel, Federico; Brault-Hernandez, Marianne; Laffont, Carole; Huault, Emeline; Brault, Mathias; Plet, Julie; Moison, Michael; Blanchet, Sandrine; Ichanté, Jean Laurent; Chabaud, Mireille; Carrere, Sébastien; Crespi, Martin; Chan, Raquel L.; Frugier, Florian

    2012-01-01

    Cytokinin regulates many aspects of plant development, and in legume crops, this phytohormone is necessary and sufficient for symbiotic nodule organogenesis, allowing them to fix atmospheric nitrogen. To identify direct links between cytokinins and nodule organogenesis, we determined a consensus sequence bound in vitro by a transcription factor (TF) acting in cytokinin signaling, the nodule-enhanced Medicago truncatula Mt RR1 response regulator (RR). Among genes rapidly regulated by cytokinins and containing this so-called RR binding site (RRBS) in their promoters, we found the nodulation-related Type-A RR Mt RR4 and the Nodulation Signaling Pathway 2 (NSP2) TF. Site-directed mutagenesis revealed that RRBS cis-elements in the RR4 and NSP2 promoters are essential for expression during nodule development and for cytokinin induction. Furthermore, a microRNA targeting NSP2 (miR171 h) is also rapidly induced by cytokinins and then shows an expression pattern anticorrelated with NSP2. Other primary targets regulated by cytokinins depending on the Cytokinin Response1 (CRE1) receptor were a cytokinin oxidase/dehydrogenase (CKX1) and a basic Helix-Loop-Helix TF (bHLH476). RNA interference constructs as well as insertion of a Tnt1 retrotransposon in the bHLH gene led to reduced nodulation. Hence, we identified two TFs, NSP2 and bHLH476, as direct cytokinin targets acting at the convergence of phytohormonal and symbiotic cues. PMID:23023168

  11. Nitrogen assimilation in alfalfa: isolation and characterization of an asparagine synthetase gene showing enhanced expression in root nodules and dark-adapted leaves.

    PubMed Central

    Shi, L; Twary, S N; Yoshioka, H; Gregerson, R G; Miller, S S; Samac, D A; Gantt, J S; Unkefer, P J; Vance, C P

    1997-01-01

    Asparagine, the primary assimilation product from N2 fixation in temperate legumes and the predominant nitrogen transport product in many plant species, is synthesized via asparagine synthetase (AS; EC 6.3.5.4). Here, we report the isolation and characterization of a cDNA and a gene encoding the nodule-enhanced form of AS from alfalfa. The AS gene is comprised of 13 exons separated by 12 introns. The 5' flanking region of the AS gene confers nodule-enhanced reporter gene activity in transformed alfalfa. This region also confers enhanced reporter gene activity in dark-treated leaves. These results indicate that the 5' upstream region of the AS gene contains elements that affect expression in root nodules and leaves. Both AS mRNA and enzyme activity increased approximately 10- to 20-fold during the development of effective nodules. Ineffective nodules have strikingly reduced amounts of AS transcript. Alfalfa leaves have quite low levels of AS mRNA and protein; however, exposure to darkness resulted in a considerable increase in both. In situ hybridization with effective nodules and beta-glucuronidase staining of nodules from transgenic plants showed that AS is expressed in both infected and uninfected cells of the nodule symbiotic zone and in the nodule parenchyma. RNA gel blot analysis and in situ hybridization results are consistent with the hypothesis that initial AS expression in nodules is independent of nitrogenase activity. PMID:9286111

  12. Nodule characterization: subsolid nodules.

    PubMed

    Raad, Roy A; Suh, James; Harari, Saul; Naidich, David P; Shiau, Maria; Ko, Jane P

    2014-01-01

    In this review, we focus on the radiologic, clinical, and pathologic aspects primarily of solitary subsolid pulmonary nodules. Particular emphasis will be placed on the pathologic classification and correlative computed tomography (CT) features of adenocarcinoma of the lung. The capabilities of fluorodeoxyglucose positron emission tomography-CT and histologic sampling techniques, including CT-guided biopsy, endoscopic-guided biopsy, and surgical resection, are discussed. Finally, recently proposed management guidelines by the Fleischner Society and the American College of Chest Physicians are reviewed.

  13. Small RNA pathways and diversity in model legumes: lessons from genomics

    PubMed Central

    Bustos-Sanmamed, Pilar; Bazin, Jérémie; Hartmann, Caroline; Crespi, Martin; Lelandais-Brière, Christine

    2013-01-01

    Small non-coding RNAs (smRNA) participate in the regulation of development, cell differentiation, adaptation to environmental constraints and defense responses in plants. They negatively regulate gene expression by degrading specific mRNA targets, repressing their translation or modifying chromatin conformation through homologous interaction with target loci. MicroRNAs (miRNA) and short-interfering RNAs (siRNA) are generated from long double stranded RNA (dsRNA) that are cleaved into 20–24-nucleotide dsRNAs by RNase III proteins called DICERs (DCL). One strand of the duplex is then loaded onto effective complexes containing different ARGONAUTE (AGO) proteins. In this review, we explored smRNA diversity in model legumes and compiled available data from miRBAse, the miRNA database, and from 22 reports of smRNA deep sequencing or miRNA identification genome-wide in three legumes: Medicago truncatula, soybean (Glycine max) and Lotus japonicus. In addition to conserved miRNAs present in other plant species, 229, 179, and 35 novel miRNA families were identified respectively in these 3 legumes, among which several seems legume-specific. New potential functions of several miRNAs in the legume-specific nodulation process are discussed. Furthermore, a new category of siRNA, the phased siRNAs, which seems to mainly regulate disease-resistance genes, was recently discovered in legumes. Despite that the genome sequence of model legumes are not yet fully completed, further analysis was performed by database mining of gene families and protein characteristics of DCLs and AGOs in these genomes. Although most components of the smRNA pathways are conserved, identifiable homologs of key smRNA players from non-legumes, like AGO10 or DCL4, could not yet be detected in M. truncatula available genomic and expressed sequence (EST) databases. In contrast to Arabidopsis, an important gene diversification was observed in the three legume models (for DCL2, AGO4, AGO2, and AGO10) or

  14. Electron Microscopy of the Infection and Subsequent Development of Soybean Nodule Cells

    PubMed Central

    Goodchild, D. J.; Bergersen, F. J.

    1966-01-01

    Goodchild, D. J. (Commonwealth Scientific and Industrial Research Organization, Canberra, Australia), and F. J. Bergersen. Electron microscopy of the infection and subsequent development of soybean nodule cells. J. Bacteriol. 92:204–213. 1966—Electron microscopy of thin sections of the developing central tissue cells of young soybean root nodules has shown that infection is initiated by a few infection threads which penetrate cells of the young central tissue. Extension growth of the threads may be a result of pressure developed from the growth of the bacteria within the threads. Release of bacteria from a thread is preceded by the development on an infection thread of a bulge with a cellulose-free membrane-bounded extension; bacteria move from this into the host cells by an endocytotic process and remain enclosed in an infection vacuole which is bounded by a membrane of host-cell origin. Multiplication of the intracellular bacteria takes place within these vacuoles. Until the host cell becomes filled with bacteria, the vacuoles separate into discrete units at each division. Later, division of the bacteria occurs within each vacuole, thus leading to the mature structure of the central tissue cells in which several bacteria are enclosed within each membrane-bounded unit. Images PMID:5949564

  15. [Evolution of legume-rhizobium symbiosis for an improved ecological efficiency and genotypic specificity of partner interactions].

    PubMed

    Provorov, N A; Vorob'ev, N I

    2011-03-01

    Mathematical simulation of the evolution of polymorphic legume-rhizobium symbiosis showed that co-evolution of the partners for an improved ecological efficiency of symbiosis is greatly stimulated when low-active N2-fixing and non-N2-fixing strains of nodule bacteria are prohibited from colonizing nodules. The results of analysis of the model were collated with the comparative morphology of the infection process in various legumes, and its was assumed that mechanisms controlling bacterial reproduction in nodules arose in early evolution of symbiosis in primitive legumes owing to a transition from mixed to clonal infection. The development of such mechanisms was associated with adaptively valuable macroevolutionary transformations of symbiosis and directed its microevolution towards a parallel increase in the specificity and efficiency of mutualism. The increase was due to a reorganization of selective processes in endosymbiotic bacterial populations, which was based on changes in their genetic and spatial structures and optimized metabolic feedbacks between the partners (preferential allocation of photosynthesis products to the most active N2-fixing strains).

  16. A Medicago truncatula NADPH oxidase is involved in symbiotic nodule functioning

    PubMed Central

    Marino, Daniel; Andrio, Emilie; Danchin, Etienne G J; Oger, Elodie; Gucciardo, Sébastien; Lambert, Annie; Puppo, Alain; Pauly, Nicolas

    2011-01-01

    Summary The plant plasma membrane-localized NADPH oxidases, known as respiratory burst oxidase homologues (RBOHs), appear to play crucial roles in plant growth and development. They are involved in important processes, such as root hair growth, plant defence reactions and abscisic acid signalling.Using sequence similarity searches, we identified seven putative RBOH-encoding genes in the Medicago truncatula genome. A phylogenetic reconstruction showed that Rboh gene duplications occurred in legume species. We analysed the expression of these MtRboh genes in different M. truncatula tissues: one of them, MtRbohA, was significantly up-regulated in Sinorhizobium meliloti-induced symbiotic nodules.MtRbohA expression appeared to be restricted to the nitrogen-fixing zone of the functional nodule. Moreover, using S. meliloti bacA and nifH mutants unable to form efficient nodules, a strong link between nodule nitrogen fixation and MtRbohA up-regulation was shown. MtRbohA expression was largely enhanced under hypoxic conditions. Specific RNA interference for MtRbohA provoked a decrease in the nodule nitrogen fixation activity and the modulation of genes encoding the microsymbiont nitrogenase.These results suggest that hypoxia, prevailing in the nodule-fixing zone, may drive the stimulation of MtRbohA expression, which would, in turn, lead to the regulation of nodule functioning. PMID:21155825

  17. Rhizobium meliloti lipooligosaccharide nodulation factors: different structural requirements for bacterial entry into target root hair cells and induction of plant symbiotic developmental responses.

    PubMed

    Ardourel, M; Demont, N; Debellé, F; Maillet, F; de Billy, F; Promé, J C; Dénarié, J; Truchet, G

    1994-10-01

    Rhizobium meliloti produces lipochitooligosaccharide nodulation NodRm factors that are required for nodulation of legume hosts. NodRm factors are O-acetylated and N-acylated by specific C16-unsaturated fatty acids. nodL mutants produce non-O-acetylated factors, and nodFE mutants produce factors with modified acyl substituents. Both mutants exhibited a significantly reduced capacity to elicit infection thread (IT) formation in alfalfa. However, once initiated, ITs developed and allowed the formation of nitrogen-fixing nodules. In contrast, double nodF/nodL mutants were unable to penetrate into legume hosts and to form ITs. Nevertheless, these mutants induced widespread cell wall tip growth in trichoblasts and other epidermal cells and were also able to elicit cortical cell activation at a distance. NodRm factor structural requirements are thus clearly more stringent for bacterial entry than for the elicitation of developmental plant responses.

  18. Rhizobium cellulase CelC2 is essential for primary symbiotic infection of legume host roots

    PubMed Central

    Robledo, M.; Jiménez-Zurdo, J. I.; Velázquez, E.; Trujillo, M. E.; Zurdo-Piñeiro, J. L.; Ramírez-Bahena, M. H.; Ramos, B.; Díaz-Mínguez, J. M.; Dazzo, F.; Martínez-Molina, E.; Mateos, P. F.

    2008-01-01

    The rhizobia–legume, root-nodule symbiosis provides the most efficient source of biologically fixed ammonia fertilizer for agricultural crops. Its development involves pathways of specificity, infectivity, and effectivity resulting from expressed traits of the bacterium and host plant. A key event of the infection process required for development of this root-nodule symbiosis is a highly localized, complete erosion of the plant cell wall through which the bacterial symbiont penetrates to establish a nitrogen-fixing, intracellular endosymbiotic state within the host. This process of wall degradation must be delicately balanced to avoid lysis and destruction of the host cell. Here, we describe the purification, biochemical characterization, molecular genetic analysis, biological activity, and symbiotic function of a cell-bound bacterial cellulase (CelC2) enzyme from Rhizobium leguminosarum bv. trifolii, the clover-nodulating endosymbiont. The purified enzyme can erode the noncrystalline tip of the white clover host root hair wall, making a localized hole of sufficient size to allow wild-type microsymbiont penetration. This CelC2 enzyme is not active on root hairs of the nonhost legume alfalfa. Microscopy analysis of the symbiotic phenotypes of the ANU843 wild type and CelC2 knockout mutant derivative revealed that this enzyme fulfils an essential role in the primary infection process required for development of the canonical nitrogen-fixing R. leguminosarum bv. trifolii-white clover symbiosis. PMID:18458328

  19. Development of an Agrobacterium-mediated transformation protocol for the tree-legume Leucaena leucocephala using immature zygotic embryos.

    PubMed

    Jube, Sandro; Borthakur, Dulal

    2009-01-01

    The tree-legume Leucaena leucocephala (leucaena) is used as a perennial fodder because of its fast-growing foliage, which is high in protein content. The use of leucaena as a fodder is however restricted due to the presence of the toxin mimosine. Improvements in the nutritional contents as well as other agronomic traits of leucaena can be accomplished through genetic transformation. The objective of this research was to develop a transformation protocol for leucaena using phosphinothricin resistance as the plant selectable marker. Explants obtained from immature zygotic embryos infected with the Agrobacterium tumefaciens strain C58C1 containing the binary plasmid pCAMBIA3201 produced four putative transformed leucaena plants. Transformation was con- firmed by PCR, RT-PCR, Southern blot, Western analyses, GUS-specific enzyme activity and herbicide leaf spraying assay. A transformation efficiency of 2% was established using this protocol.

  20. Transcription profiling of soybean nodulation by Bradyrhizobium japonicum

    USDA-ARS?s Scientific Manuscript database

    Legumes interact with nodulating bacteria to convert atmospheric nitrogen into ammonia for plant use. This nitrogen fixation takes place within root nodules that form after infection of root hairs by compatible rhizobium. Using cDNA microarrays, we monitored gene expression in soybean (Glycine max) ...

  1. Development of a virus induced gene silencing vector from a legumes infecting tobamovirus.

    PubMed

    Várallyay, Eva; Lichner, Zsuzsanna; Sáfrány, Judit; Havelda, Z; Salamon, P; Bisztray, Gy; Burgyán, J

    2010-12-01

    Medicago truncatula, the model plant of legumes, is well characterized, but there is only a little knowledge about it as a viral host. Viral vectors can be used for expressing foreign genes or for virus-induced gene silencing (VIGS), what is a fast and powerful tool to determine gene functions in plants. Viral vectors effective on Nicotiana benthamiana have been constructed from a number of viruses, however, only few of them were effective in other plants. A Tobamovirus, Sunnhemp mosaic virus (SHMV) systemically infects Medicago truncatula without causing severe symptoms. To set up a viral vector for Medicago truncatula, we prepared an infectious cDNA clone of SHMV. We constructed two VIGS vectors differing in the promoter element to drive foreign gene expression. The vectors were effective both in the expression and in the silencing of a transgene Green Fluorescent Protein (GFP) and in silencing of an endogenous gene Phytoene desaturase (PDS) on N. benthamiana. Still only one of the vectors was able to successfully silence the endogenous Chlorata 42 gene in M. truncatula.

  2. Policing the legume-Rhizobium symbiosis: a critical test of partner choice.

    PubMed

    Westhoek, Annet; Field, Elsa; Rehling, Finn; Mulley, Geraldine; Webb, Isabel; Poole, Philip S; Turnbull, Lindsay A

    2017-05-03

    In legume-Rhizobium symbioses, specialised soil bacteria fix atmospheric nitrogen in return for carbon. However, ineffective strains can arise, making discrimination essential. Discrimination can occur via partner choice, where legumes prevent ineffective strains from entering, or via sanctioning, where plants provide fewer resources. Several studies have inferred that legumes exercise partner choice, but the rhizobia compared were not otherwise isogenic. To test when and how plants discriminate ineffective strains we developed sets of fixing and non-fixing strains that differed only in the expression of nifH - essential for nitrogen fixation - and could be visualised using marker genes. We show that the plant is unable to select against the non-fixing strain at the point of entry, but that non-fixing nodules are sanctioned. We also used the technique to characterise mixed nodules (containing both a fixing and a non-fixing strain), whose frequency could be predicted using a simple diffusion model. We discuss that sanctioning is likely to evolve in preference to partner choice in any symbiosis where partner quality cannot be adequately assessed until goods or services are actively exchanged.

  3. Rj (rj) genes involved in nitrogen-fixing root nodule formation in soybean

    PubMed Central

    Hayashi, Masaki; Saeki, Yuichi; Haga, Michiyo; Harada, Kyuya; Kouchi, Hiroshi; Umehara, Yosuke

    2012-01-01

    It has long been known that formation of symbiotic root nodules in soybean (Glycine max (L.) Merr.) is controlled by several host genes referred to as Rj (rj) genes, but molecular cloning of these genes has been hampered by soybean’s complicated genome structure and large genome size. Progress in molecular identification of legume genes involved in root nodule symbiosis have been mostly achieved by using two model legumes, Lotus japonicus and Medicago truncatula, that have relatively simple and small genomes and are capable of molecular transfection. However, recent development of resources for soybean molecular genetic research, such as genome sequencing, large EST databases, and high-density linkage maps, have enabled us to isolate several Rj genes. This progress has been achieved in connection with systematic utilization of the information obtained from molecular genetics of the model legumes. In this review, we summarize the current status of knowledge of host-controlled nodulation in soybean based on information from recent studies on Rj genes, and discuss the future research prospects. PMID:23136493

  4. WUSCHEL-RELATED HOMEOBOX5 Gene Expression and Interaction of CLE Peptides with Components of the Systemic Control Add Two Pieces to the Puzzle of Autoregulation of Nodulation1[W

    PubMed Central

    Osipova, Maria A.; Mortier, Virginie; Demchenko, Kirill N.; Tsyganov, Victor E.; Tikhonovich, Igor A.; Lutova, Ludmila A.; Dolgikh, Elena A.; Goormachtig, Sofie

    2012-01-01

    In legumes, the symbiotic nodules are formed as a result of dedifferentiation and reactivation of cortical root cells. A shoot-acting receptor complex, similar to the Arabidopsis (Arabidopsis thaliana) CLAVATA1 (CLV1)/CLV2 receptor, regulating development of the shoot apical meristem, is involved in autoregulation of nodulation (AON), a mechanism that systemically controls nodule number. The targets of CLV1/CLV2 in the shoot apical meristem, the WUSCHEL (WUS)-RELATED HOMEOBOX (WOX) family transcription factors, have been proposed to be important regulators of apical meristem maintenance and to be expressed in apical meristem “organizers.” Here, we focus on the role of the WOX5 transcription factor upon nodulation in Medicago truncatula and pea (Pisum sativum) that form indeterminate nodules. Analysis of temporal WOX5 expression during nodulation with quantitative reverse transcription-polymerase chain reaction and promoter-reporter fusion revealed that the WOX5 gene was expressed during nodule organogenesis, suggesting that WOX genes are common regulators of cell proliferation in different systems. Furthermore, in nodules of supernodulating mutants, defective in AON, WOX5 expression was higher than that in wild-type nodules. Hence, a conserved WUS/WOX-CLV regulatory system might control cell proliferation and differentiation not only in the root and shoot apical meristems but also in nodule meristems. In addition, the link between nodule-derived CLE peptides activating AON in different legumes and components of the AON system was investigated. We demonstrate that the identified AON component, NODULATION3 of pea, might act downstream from or beside the CLE peptides during AON. PMID:22232385

  5. Multiple Autoregulation of Nodulation (AON) Signals Identified through Split Root Analysis of Medicago truncatula sunn and rdn1 Mutants.

    PubMed

    Kassaw, Tessema; Jr, William Bridges; Frugoli, Julia

    2015-04-27

    Nodulation is energetically costly to the host: legumes balance the nitrogen demand with the energy expense by limiting the number of nodules through long-distance signaling. A split root system was used to investigate systemic autoregulation of nodulation (AON) in Medicago truncatula and the role of the AON genes RDN1 and SUNN in the regulatory circuit. Developing nodule primordia did not trigger AON in plants carrying mutations in RDN1 and SUNN genes, while wild type plants had fully induced AON within three days. However, despite lacking an early suppression response, AON mutants suppressed nodulation when roots were inoculated 10 days or more apart, correlated with the maturation of nitrogen fixing nodules. In addition to correlation between nitrogen fixation and suppression of nodulation, suppression by extreme nutrient stress was also observed in all genotypes and may be a component of the observed response due to the conditions of the assay. These results suggest there is more than one systemic regulatory circuit controlling nodulation in M. truncatula. While both signals are present in wild type plants, the second signal can only be observed in plants lacking the early repression (AON mutants). RDN1 and SUNN are not essential for response to the later signal.

  6. Multiple Autoregulation of Nodulation (AON) Signals Identified through Split Root Analysis of Medicago truncatula sunn and rdn1 Mutants

    PubMed Central

    Kassaw, Tessema; Bridges, William; Frugoli, Julia

    2015-01-01

    Nodulation is energetically costly to the host: legumes balance the nitrogen demand with the energy expense by limiting the number of nodules through long-distance signaling. A split root system was used to investigate systemic autoregulation of nodulation (AON) in Medicago truncatula and the role of the AON genes RDN1 and SUNN in the regulatory circuit. Developing nodule primordia did not trigger AON in plants carrying mutations in RDN1 and SUNN genes, while wild type plants had fully induced AON within three days. However, despite lacking an early suppression response, AON mutants suppressed nodulation when roots were inoculated 10 days or more apart, correlated with the maturation of nitrogen fixing nodules. In addition to correlation between nitrogen fixation and suppression of nodulation, suppression by extreme nutrient stress was also observed in all genotypes and may be a component of the observed response due to the conditions of the assay. These results suggest there is more than one systemic regulatory circuit controlling nodulation in M. truncatula. While both signals are present in wild type plants, the second signal can only be observed in plants lacking the early repression (AON mutants). RDN1 and SUNN are not essential for response to the later signal. PMID:27135324

  7. Landmark Research in Legumes

    USDA-ARS?s Scientific Manuscript database

    Legumes are members of family Fabaceae or Leguminosae and include economically important grain legumes, oilseed crops, forage crops, shrubs and tropical or subtropical trees. Many legumes are rich source of quality protein for humans and animals and enrich the soil by producing their own nitrogen i...

  8. Nodulation gene mutants of Mesorhizobium loti R7A-nodZ and nolL mutants have host-specific phenotypes on Lotus spp.

    PubMed

    Rodpothong, Patsarin; Sullivan, John T; Songsrirote, Kriangsak; Sumpton, David; Cheung, Kenneth W J-T; Thomas-Oates, Jane; Radutoiu, Simona; Stougaard, Jens; Ronson, Clive W

    2009-12-01

    Rhizobial Nod factors induce plant responses and facilitate bacterial infection, leading to the development of nitrogen-fixing root nodules on host legumes. Nodule initiation is highly dependent on Nod-factor structure and, hence, on at least some of the nodulation genes that encode Nod-factor production. Here, we report the effects of mutations in Mesorhizobium loti R7A nodulation genes on nodulation of four Lotus spp. and on Nod-factor structure. Most mutants, including a DeltanodSDeltanolO double mutant that produced Nod factors lacking the carbamoyl and possibly N-methyl groups on the nonreducing terminal residue, were unaffected for nodulation. R7ADeltanodZ and R7ADeltanolL mutants that produced Nod factors without the (acetyl)fucose on the reducing terminal residue had a host-specific phenotype, forming mainly uninfected nodule primordia on Lotus filicaulis and L. corniculatus and effective nodules with a delay on L. japonicus. The mutants also showed significantly reduced infection thread formation and Nin gene induction. In planta complementation experiments further suggested that the acetylfucose was important for balanced signaling in response to Nod factor by the L. japonicus NFR1/NFR5 receptors. Overall the results reveal differences in the sensitivity of plant perception with respect to signaling leading to root hair deformation and nodule primordium development versus infection thread formation and rhizobial entry.

  9. Inoculation of Woody Legumes with Selected Arbuscular Mycorrhizal Fungi and Rhizobia To Recover Desertified Mediterranean Ecosystems

    PubMed Central

    Herrera, M. A.; Salamanca, C. P.; Barea, J. M.

    1993-01-01

    Revegetation strategies, either for reclamation or for rehabilitation, are being used to recover desertified ecosystems. Woody legumes are recognized as species that are useful for revegetation of water-deficient, low-nutrient environments because of their ability to form symbiotic associations with rhizobial bacteria and mycorrhizal fungi, which improve nutrient acquisition and help plants to become established and cope with stress situations. A range of woody legumes used in revegetation programs, particularly in Mediterranean regions, were assayed. These legumes included both exotic and native species and were used in a test of a desertified semiarid ecosystem in southeast Spain. Screening for the appropriate plant species-microsymbiont combinations was performed previously, and a simple procedure to produce plantlets with optimized mycorrhizal and nodulated status was developed. The results of a 4-year trial showed that (i) only the native shrub legumes were able to become established under the local environmental conditions (hence, a reclamation strategy is recommended) and (ii) biotechnological manipulation of the seedlings to be used for revegetation (by inoculation with selected rhizobia and mycorrhizal fungi) improved outplanting performance, plant survival, and biomass development. PMID:16348838

  10. Nodule morphology, symbiotic specificity and association with unusual rhizobia are distinguishing features of the genus Listia within the Southern African crotalarioid clade Lotononis s.l.

    PubMed

    Ardley, Julie K; Reeve, Wayne G; O'Hara, Graham W; Yates, Ron J; Dilworth, Michael J; Howieson, John G

    2013-07-01

    The legume clade Lotononis sensu lato (s.l.; tribe Crotalarieae) comprises three genera: Listia, Leobordea and Lotononis sensu stricto (s.s.). Listia species are symbiotically specific and form lupinoid nodules with rhizobial species of Methylobacterium and Microvirga. This work investigated whether these symbiotic traits were confined to Listia by determining the ability of rhizobial strains isolated from species of Lotononis s.l. to nodulate Listia, Leobordea and Lotononis s.s. hosts and by examining the morphology and structure of the resulting nodules. Rhizobia were characterized by sequencing their 16S rRNA and nodA genes. Nodulation and N2 fixation on eight taxonomically diverse Lotononis s.l. species were determined in glasshouse trials. Nodules of all hosts, and the process of infection and nodule initiation in Listia angolensis and Listia bainesii, were examined by light microscopy. Rhizobia associated with Lotononis s.l. were phylogenetically diverse. Leobordea and Lotononis s.s. isolates were most closely related to Bradyrhizobium spp., Ensifer meliloti, Mesorhizobium tianshanense and Methylobacterium nodulans. Listia angolensis formed effective nodules only with species of Microvirga. Listia bainesii nodulated only with pigmented Methylobacterium. Five lineages of nodA were found. Listia angolensis and L. bainesii formed lupinoid nodules, whereas nodules of Leobordea and Lotononis s.s. species were indeterminate. All effective nodules contained uniformly infected central tissue. Listia angolensis and L. bainesii nodule initials occurred on the border of the hypocotyl and along the tap root, and nodule primordia developed in the outer cortical layer. Neither root hair curling nor infection threads were seen. Two specificity groups occur within Lotononis s.l.: Listia species are symbiotically specific, while species of Leobordea and Lotononis s.s. are generally promiscuous and interact with rhizobia of diverse chromosomal and symbiotic lineages. The

  11. Nodule morphology, symbiotic specificity and association with unusual rhizobia are distinguishing features of the genus Listia within the southern African crotalarioid clade Lotononis s.l.

    PubMed Central

    Ardley, Julie K.; Reeve, Wayne G.; O'Hara, Graham W.; Yates, Ron J.; Dilworth, Michael J.; Howieson, John G.

    2013-01-01

    Background and Aims The legume clade Lotononis sensu lato (s.l.; tribe Crotalarieae) comprises three genera: Listia, Leobordea and Lotononis sensu stricto (s.s.). Listia species are symbiotically specific and form lupinoid nodules with rhizobial species of Methylobacterium and Microvirga. This work investigated whether these symbiotic traits were confined to Listia by determining the ability of rhizobial strains isolated from species of Lotononis s.l. to nodulate Listia, Leobordea and Lotononis s.s. hosts and by examining the morphology and structure of the resulting nodules. Methods Rhizobia were characterized by sequencing their 16S rRNA and nodA genes. Nodulation and N2 fixation on eight taxonomically diverse Lotononis s.l. species were determined in glasshouse trials. Nodules of all hosts, and the process of infection and nodule initiation in Listia angolensis and Listia bainesii, were examined by light microscopy. Key Results Rhizobia associated with Lotononis s.l. were phylogenetically diverse. Leobordea and Lotononis s.s. isolates were most closely related to Bradyrhizobium spp., Ensifer meliloti, Mesorhizobium tianshanense and Methylobacterium nodulans. Listia angolensis formed effective nodules only with species of Microvirga. Listia bainesii nodulated only with pigmented Methylobacterium. Five lineages of nodA were found. Listia angolensis and L. bainesii formed lupinoid nodules, whereas nodules of Leobordea and Lotononis s.s. species were indeterminate. All effective nodules contained uniformly infected central tissue. Listia angolensis and L. bainesii nodule initials occurred on the border of the hypocotyl and along the tap root, and nodule primordia developed in the outer cortical layer. Neither root hair curling nor infection threads were seen. Conclusions Two specificity groups occur within Lotononis s.l.: Listia species are symbiotically specific, while species of Leobordea and Lotononis s.s. are generally promiscuous and interact with rhizobia of

  12. RNA-Seq analysis of nodule development at five different developmental stages of soybean (Glycine max) inoculated with Bradyrhizobium japonicum strain 113-2

    PubMed Central

    Yuan, Song L.; Li, Rong; Chen, Hai F.; Zhang, Chan J.; Chen, Li M.; Hao, Qing N.; Chen, Shui L.; Shan, Zhi H.; Yang, Zhong L.; Zhang, Xiao J.; Qiu, De Z.; Zhou, Xin A.

    2017-01-01

    Nodule development directly affects nitrogen fixation efficiency during soybean growth. Although abundant genome-based information related to nodule development has been released and some studies have reported the molecular mechanisms that regulate nodule development, information on the way nodule genes operate in nodule development at different developmental stages of soybean is limited. In this report, notably different nodulation phenotypes in soybean roots inoculated with Bradyrhizobium japonicum strain 113-2 at five developmental stages (branching stage, flowering stage, fruiting stage, pod stage and harvest stage) were shown, and the expression of nodule genes at these five stages was assessed quantitatively using RNA-Seq. Ten comparisons were made between these developmental periods, and their differentially expressed genes were analysed. Some important genes were identified, primarily encoding symbiotic nitrogen fixation-related proteins, cysteine proteases, cystatins and cysteine-rich proteins, as well as proteins involving plant-pathogen interactions. There were no significant shifts in the distribution of most GO functional annotation terms and KEGG pathway enrichment terms between these five development stages. A cystatin Glyma18g12240 was firstly identified from our RNA-seq, and was likely to promote nodulation and delay nodule senescence. This study provides molecular material for further investigations into the mechanisms of nitrogen fixation at different soybean developmental stages. PMID:28169364

  13. N-fixation in legumes--An assessment of the potential threat posed by ozone pollution.

    PubMed

    Hewitt, D K L; Mills, G; Hayes, F; Norris, D; Coyle, M; Wilkinson, S; Davies, W

    2016-01-01

    The growth, development and functioning of legumes are often significantly affected by exposure to tropospheric ozone (O3) pollution. However, surprisingly little is known about how leguminous Nitrogen (N) fixation responds to ozone, with a scarcity of studies addressing this question in detail. In the last decade, ozone impacts on N-fixation in soybean, cowpea, mung bean, peanut and clover have been shown for concentrations which are now commonly recorded in ambient air or are likely to occur in the near future. We provide a synthesis of the existing literature addressing this issue, and also explore the effects that may occur on an agroecosystem scale by predicting reductions in Trifolium (clovers) root nodule biomass in United Kingdom (UK) pasture based on ozone concentration data for a "high" (2006) and "average" ozone year (2008). Median 8% and 5% reductions in clover root nodule biomass in pasture across the UK were predicted for 2006 and 2008 respectively. Seasonal exposure to elevated ozone, or short-term acute concentrations >100 ppb, are sufficient to reduce N-fixation and/or impact nodulation, in a range of globally-important legumes. However, an increasing global burden of CO2, the use of artificial fertiliser, and reactive N-pollution may partially mitigate impacts of ozone on N-fixation.

  14. An experimental and modelling exploration of the host-sanction hypothesis in legume-rhizobia mutualism.

    PubMed

    Marco, Diana E; Carbajal, Juan P; Cannas, Sergio; Pérez-Arnedo, Rebeca; Hidalgo-Perea, Angeles; Olivares, José; Ruiz-Sainz, José E; Sanjuán, Juan

    2009-08-07

    Despite the importance of mutualism as a key ecological process, its persistence in nature is difficult to explain since the existence of exploitative, "cheating" partners that could erode the interaction is common. By analogy with the proposed policing strategy stabilizing intraspecific cooperation, host sanctions against non-N(2) fixing, cheating symbionts have been proposed as a force stabilizing mutualism in legume-Rhizobium symbiosis. Following this proposal, penalizations would include decreased nodular rhizobial viability and/or early nodule senescence in nodules occupied by cheating rhizobia. In this work, we analyse the stability of Rhizobium-legume symbiosis when non-fixing, cheating strains are present, using an experimental and modelling approach. We used split-root experiments with soybean plants inoculated with two rhizobial strains, a cooperative, normal N(2) fixing strain and an isogenic non-fixing, "perfect" cheating mutant derivative that lacks nitrogenase activity but has the same nodulation abilities inoculated to split-root plants. We found no experimental evidence of functioning plant host sanctions to cheater rhizobia based on nodular rhizobia viability and nodule senescence and maturity molecular markers. Based on these experiments, we developed a population dynamic model with and without the inclusion of plant host sanctions. We show that plant populations persist in spite of the presence of cheating rhizobia without the need of incorporating any sanction against the cheater populations in the model, under the realistic assumption that plants can at least get some amount of fixed N(2) from the effectively mutualistic rhizobia occupying some nodules. Inclusion of plant sanctions leads to the unrealistic effect of ultimate extinction of cheater strains in soil. Our simulation results are in agreement with increasing experimental evidence and theoretical work showing that mutualisms can persist in presence of cheating partners.

  15. GmTIR1/GmAFB3-based auxin perception regulated by miR393 modulates soybean nodulation.

    PubMed

    Cai, Zhaoming; Wang, Youning; Zhu, Lin; Tian, Yinping; Chen, Liang; Sun, Zhengxi; Ullah, Ihteram; Li, Xia

    2017-07-01

    Auxins play important roles in the nodulation of legumes. However, the mechanism by which auxin signaling regulates root nodulation is largely unknown. In particular, the role of auxin receptors and their regulation in determinate nodule development remains elusive. We checked the expression pattern of the auxin receptor GmTIR1/GmAFB3 genes in soybean. We analyzed the functions of GmTIR1/AFB3 in the regulation of rhizobial infection and nodule number, and also tested the functions of miR393 during nodulation and its relationship with GmTIR1/AFB3. The results showed that GmTIR1 and GmAFB3 genes exhibit diverse expression patterns during nodulation and overexpression of GmTIR1 genes significantly increased inflection foci and eventual nodule number. GmTIR1/AFB3 genes were post-transcriptionally cleaved by miR393 family and knock-down of the miR393 family members significantly increased rhizobial infection and the nodule number. Overexpression of the mutated form of GmTIR1C at the miR393 cleavage site that is resistant to miR393 cleavage led to a further increase in the number of infection foci and nodules, suggesting that miR393s modulate nodulation by directly targeting GmTIR1C. This study demonstrated that GmTIR1- and GmAFB3-mediated auxin signaling, that is spatio-temporally regulated by miR393, plays a crucial role in determinate nodule development in soybean. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  16. The evolutionary dynamics of ancient and recent polyploidy in the African semiaquatic species of the legume genus Aeschynomene.

    PubMed

    Chaintreuil, Clémence; Gully, Djamel; Hervouet, Catherine; Tittabutr, Panlada; Randriambanona, Herizo; Brown, Spencer C; Lewis, Gwilym P; Bourge, Mickaël; Cartieaux, Fabienne; Boursot, Marc; Ramanankierana, Heriniaina; D'Hont, Angélique; Teaumroong, Neung; Giraud, Eric; Arrighi, Jean-François

    2016-08-01

    The legume genus Aeschynomene is notable in the ability of certain semiaquatic species to develop nitrogen-fixing stem nodules. These species are distributed in two clades. In the first clade, all the species are characterized by the use of a unique Nod-independent symbiotic process. In the second clade, the species use a Nod-dependent symbiotic process and some of them display a profuse stem nodulation as exemplified in the African Aeschynomene afraspera. To facilitate the molecular analysis of the symbiotic characteristics of such legumes, we took an integrated molecular and cytogenetic approach to track occurrences of polyploidy events and to analyze their impact on the evolution of the African species of Aeschynomene. Our results revealed two rounds of polyploidy: a paleopolyploid event predating the African group and two neopolyploid speciations, along with significant chromosomal variations. Hence, we found that A. afraspera (8x) has inherited the contrasted genomic properties and the stem-nodulation habit of its parental lineages (4x). This study reveals a comprehensive picture of African Aeschynomene diversification. It notably evidences a history that is distinct from the diploid Nod-independent clade, providing clues for the identification of the specific determinants of the Nod-dependent and Nod-independent symbiotic processes, and for comparative analysis of stem nodulation.

  17. NPR1 Protein Regulates Pathogenic and Symbiotic Interactions between Rhizobium and Legumes and Non-Legumes

    PubMed Central

    Peleg-Grossman, Smadar; Golani, Yael; Kaye, Yuval; Melamed-Book, Naomi; Levine, Alex

    2009-01-01

    Background Legumes are unique in their ability to establish symbiotic interaction with rhizobacteria from Rhizobium genus, which provide them with available nitrogen. Nodulation factors (NFs) produced by Rhizobium initiate legume root hair deformation and curling that entrap the bacteria, and allow it to grow inside the plant. In contrast, legumes and non-legumes activate defense responses when inoculated with pathogenic bacteria. One major defense pathway is mediated by salicylic acid (SA). SA is sensed and transduced to downstream defense components by a redox-regulated protein called NPR1. Methodology/Principal Findings We used Arabidopsis mutants in SA defense pathway to test the role of NPR1 in symbiotic interactions. Inoculation of Sinorhizobium meliloti or purified NF on Medicago truncatula or nim1/npr1 A. thaliana mutants induced root hair deformation and transcription of early and late nodulins. Application of S. meliloti or NF on M. truncatula or A. thaliana roots also induced a strong oxidative burst that lasted much longer than in plants inoculated with pathogenic or mutualistic bacteria. Transient overexpression of NPR1 in M. truncatula suppressed root hair curling, while inhibition of NPR1 expression by RNAi accelerated curling. Conclusions/Significance We show that, while NPR1 has a positive effect on pathogen resistance, it has a negative effect on symbiotic interactions, by inhibiting root hair deformation and nodulin expression. Our results also show that basic plant responses to Rhizobium inoculation are conserved in legumes and non-legumes. PMID:20027302

  18. A Novel Family in Medicago truncatula Consisting of More Than 300 Nodule-Specific Genes Coding for Small, Secreted Polypeptides with Conserved Cysteine Motifs1[w

    PubMed Central

    Mergaert, Peter; Nikovics, Krisztina; Kelemen, Zsolt; Maunoury, Nicolas; Vaubert, Danièle; Kondorosi, Adam; Kondorosi, Eva

    2003-01-01

    Transcriptome analysis of Medicago truncatula nodules has led to the discovery of a gene family named NCR (nodule-specific cysteine rich) with more than 300 members. The encoded polypeptides were short (60–90 amino acids), carried a conserved signal peptide, and, except for a conserved cysteine motif, displayed otherwise extensive sequence divergence. Family members were found in pea (Pisum sativum), broad bean (Vicia faba), white clover (Trifolium repens), and Galega orientalis but not in other plants, including other legumes, suggesting that the family might be specific for galegoid legumes forming indeterminate nodules. Gene expression of all family members was restricted to nodules except for two, also expressed in mycorrhizal roots. NCR genes exhibited distinct temporal and spatial expression patterns in nodules and, thus, were coupled to different stages of development. The signal peptide targeted the polypeptides in the secretory pathway, as shown by green fluorescent protein fusions expressed in onion (Allium cepa) epidermal cells. Coregulation of certain NCR genes with genes coding for a potentially secreted calmodulin-like protein and for a signal peptide peptidase suggests a concerted action in nodule development. Potential functions of the NCR polypeptides in cell-to-cell signaling and creation of a defense system are discussed. PMID:12746522

  19. Thyroid nodule

    MedlinePlus

    ... has grown Another possible treatment is an ethanol (alcohol) injection into the nodule to shrink ... Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, ...

  20. Manganese nodules

    USGS Publications Warehouse

    Hein, James R.; Harff, Jan; Petersen, Sven; Thiede, Jorn

    2016-01-01

    The existence of manganese (Mn) nodules (Fig. 1) has been known since the late 1800s when they were collected during the Challenger expedition of 1873–1876. However, it was not until after WWII that nodules were further studied in detail for their ability to adsorb metals from seawater. Many of the early studies did not distinguish Mn nodules from Mn crusts. Economic interest in Mn nodules began in the late 1950s and early 1960s when John Mero finished his Ph.D. thesis on this subject, which was published...

  1. Growth and foliar nitrogen concentrations of interplanted native woody legumes and pecan

    Treesearch

    J.W. Van Sambeek; Nadia E. Navarrete-Tindall; Kenneth L. Hunt

    2008-01-01

    The interplanting and underplanting of nodulated nitrogen-fixing plants in tree plantings can increase early growth and foliage nitrogen content of hardwoods, especially black walnut and pecan. Recent studies have demonstrated that some non-nodulated woody legumes may be capable of fixing significant levels of atmospheric nitrogen. The following nine nurse crop...

  2. The Ribosomal RNA is a Useful Marker to Visualize Rhizobia Interacting with Legume Plants

    ERIC Educational Resources Information Center

    Rinaudi, Luciana; Isola, Maria C.; Giordano, Walter

    2004-01-01

    Symbiosis between rhizobia and leguminous plants leads to the formation of nitrogen-fixing root nodules. In the present article, we recommend the use of the ribosomal RNA (rRNA) isolated from legume nodules in an experimental class with the purpose of introducing students to the structure of eukaryotic and prokaryotic ribosomes and of…

  3. The Ribosomal RNA is a Useful Marker to Visualize Rhizobia Interacting with Legume Plants

    ERIC Educational Resources Information Center

    Rinaudi, Luciana; Isola, Maria C.; Giordano, Walter

    2004-01-01

    Symbiosis between rhizobia and leguminous plants leads to the formation of nitrogen-fixing root nodules. In the present article, we recommend the use of the ribosomal RNA (rRNA) isolated from legume nodules in an experimental class with the purpose of introducing students to the structure of eukaryotic and prokaryotic ribosomes and of…

  4. Antisense Repression of the Medicago truncatula Nodule-Enhanced Sucrose Synthase Leads to a Handicapped Nitrogen Fixation Mirrored by Specific Alterations in the Symbiotic Transcriptome and Metabolome1[W

    PubMed Central

    Baier, Markus C.; Barsch, Aiko; Küster, Helge; Hohnjec, Natalija

    2007-01-01

    We analyzed the role of the sucrose (Suc) synthase MtSucS1 during nodulation of the model legume Medicago truncatula, integrating data for the developmental, transcriptional, and metabolic processes affected downstream of an impaired Suc cleavage in root nodules. To reduce carbohydrate supply to nodule tissues, transgenic plants expressing a p35S-driven MtSucS1-antisense fusion were constructed. These plants displayed an up to 90% reduction of MtSucS1 proteins in roots and nodules. Phenotypic studies of two independent MtSucS1-reduced lines demonstrated that only under conditions depending on nodulation, these plants appeared to be impaired in above-ground growth. Specifically plant height, shoot weight, leaf development, flowering, as well as seed maturation were reduced, and the efficiency of photosynthesis was affected. Concomitantly, a significantly enhanced root to shoot ratio with a marked increase in root tip numbers was observed. Root nodule formation was found retarded and the impaired nodulation was accompanied by a less efficient nitrogen (N) acquisition. The decreased total N content of MtSucS1-antisense lines and an enhanced carbon to N ratio in roots, nodules, and shoots correlated with the extent of MtSucS1 knockdown. On the level of transcription, effects of an MtSucS1 reduction were evident for genes representing important nodes of the nodule carbon and N metabolism, while metabolite profiling revealed significantly lower levels of amino acids and their derivatives particularly in strongly MtSucS1-reduced nodules. Our results support the model that nodule-enhanced Suc synthase 1 of the model legume M. truncatula is required for the establishment and maintenance of an efficient N-fixing symbiosis. PMID:17951459

  5. Flooding tolerance of forage legumes.

    PubMed

    Striker, Gustavo G; Colmer, Timothy D

    2016-06-20

    We review waterlogging and submergence tolerances of forage (pasture) legumes. Growth reductions from waterlogging in perennial species ranged from >50% for Medicago sativa and Trifolium pratense to <25% for Lotus corniculatus, L. tenuis, and T. fragiferum For annual species, waterlogging reduced Medicago truncatula by ~50%, whereas Melilotus siculus and T. michelianum were not reduced. Tolerant species have higher root porosity (gas-filled volume in tissues) owing to aerenchyma formation. Plant dry mass (waterlogged relative to control) had a positive (hyperbolic) relationship to root porosity across eight species. Metabolism in hypoxic roots was influenced by internal aeration. Sugars accumulate in M. sativa due to growth inhibition from limited respiration and low energy in roots of low porosity (i.e. 4.5%). In contrast, L. corniculatus, with higher root porosity (i.e. 17.2%) and O2 supply allowing respiration, maintained growth better and sugars did not accumulate. Tolerant legumes form nodules, and internal O2 diffusion along roots can sustain metabolism, including N2 fixation, in submerged nodules. Shoot physiology depends on species tolerance. In M. sativa, photosynthesis soon declines and in the longer term (>10 d) leaves suffer chlorophyll degradation, damage, and N, P, and K deficiencies. In tolerant L corniculatus and L. tenuis, photosynthesis is maintained longer, shoot N is less affected, and shoot P can even increase during waterlogging. Species also differ in tolerance of partial and complete shoot submergence. Gaps in knowledge include anoxia tolerance of roots, N2 fixation during field waterlogging, and identification of traits conferring the ability to recover after water subsides.

  6. Clinical characteristics that distinguish eosinophilic organ infiltration from metastatic nodule development in cancer patients with eosinophilia

    PubMed Central

    2012-01-01

    Background When new space-occupying lesions are observed together with peripheral blood eosinophilia in patients diagnosed with cancer, the possibility of eosinophilic organ involvement should be differentiated from metastasis of primary cancer, since a misdiagnosis could lead to unnecessary chemotherapy. The aim of this study is to identify the clinical characteristics of eosinophilic organ involvement that distinguish it from distant metastasis in patients with primary cancer. Methods The medical records of 43 cancer patients who developed hepatic or pulmonary nodules with peripheral blood eosinophilia between January 2005 and February 2010 in the Asan Medical Center (Seoul) were reviewed. Eosinophilic infiltration and distant metastasis were identified on the basis of pathological findings and radiological features. Fisher’s exact test, χ2 test or Mann-Whitney test were used for statistical analysis. Results In total, 33 patients (76%) were diagnosed with eosinophilic infiltration, 5 (12%) with cancer metastasis and 5 (12%) had undetermined diagnoses. Compared to the patients with metastases, the patients with eosinophilic infiltration were significantly more likely to have serology indicating a parasitic infection, a history of eating raw food, high serum levels of total IgE, normal liver function, normal C-reactive protein levels, a normal erythrocyte sedimentation rate, and fewer and smaller nodules. The most common underlying malignancy in the eosinophilic organ infiltration group was stomach cancer. Physicians tended to neglect the eosinophilia in patients with a history of cancer. Conclusions Several clinical characteristics of eosinophilic organ infiltration distinguish it from cancer metastasis. Physicians should make greater efforts to determine the causes of organ involvement with peripheral blood eosinophilia, especially in cancer patients. PMID:22929225

  7. Nodulation of Cyclopia spp. (Leguminosae, Papilionoideae) by Burkholderia tuberum

    PubMed Central

    Elliott, Geoffrey N.; Chen, Wen-Ming; Bontemps, Cyril; Chou, Jui-Hsing; Young, J. Peter W.; Sprent, Janet I.; James, Euan K.

    2007-01-01

    Background and Aims Species of the genus Burkholderia, from the Betaproteobacteria, have been isolated from legume nodules, but so far they have only been shown to form symbioses with species of Mimosa, sub-family Mimosoideae. This work investigates whether Burkholderia tuberum strains STM678 (isolated from Aspalathus carnosa) and DUS833 (from Aspalathus callosa) can nodulate species of the South African endemic papilionoid genera Cyclopia (tribe Podalyrieae) and Aspalathus (Crotalarieae) as well as the promiscuous legume Macroptilium atropurpureum (Phaseoleae). Method Bacterial strains and the phylogeny of their symbiosis-related (nod) genes were examined via 16S rRNA gene sequencing. Seedlings were grown in liquid culture and inoculated with one of the two strains of B. tuberum or with Sinorhizobium strain NGR 234 (from Lablab purpureus), Mesorhizobium strain DUS835 (from Aspalathus linearis) or Methylobacterium nodulans (from Crotalaria podocarpa). Some nodules, inoculated with green fluorescence protein (GFP)-tagged strains, were examined by light and electron microscopy coupled with immunogold labelling with a Burkholderia-specific antibody. The presence of active nitrogenase was checked by immunolabelling of nitrogenase and by the acetylene reduction assay. B. tuberum STM678 was also tested on a wide range of legumes from all three sub-families. Key Results Nodules were not formed on any of the Aspalathus spp. Only B. tuberum nodulated Cyclopia falcata, C. galioides, C. genistoides, C. intermedia and C. pubescens. It also effectively nodulated M. atropurpureum but no other species tested. GFP-expressing inoculant strains were located inside infected cells of C. genistoides, and bacteroids in both Cyclopia spp. and M. atropurpureum were immunogold-labelled with antibodies against Burkholderia and nitrogenase. Nitrogenase activity was also shown using the acetylene reduction assay. This is the first demonstration that a β-rhizobial strain can effectively

  8. Micromonospora from nitrogen fixing nodules of alfalfa (Medicago sativa L.). A new promising Plant Probiotic Bacteria.

    PubMed

    Martínez-Hidalgo, Pilar; Galindo-Villardón, Purificación; Trujillo, Martha E; Igual, José M; Martínez-Molina, Eustoquio

    2014-09-17

    Biotic interactions can improve agricultural productivity without costly and environmentally challenging inputs. Micromonospora strains have recently been reported as natural endophytes of legume nodules but their significance for plant development and productivity has not yet been established. The aim of this study was to determine the diversity and function of Micromonospora isolated from Medicago sativa root nodules. Micromonospora-like strains from field alfalfa nodules were characterized by BOX-PCR fingerprinting and 16S rRNA gene sequencing. The ecological role of the interaction of the 15 selected representative Micromonospora strains was tested in M. sativa. Nodulation, plant growth and nutrition parameters were analyzed. Alfalfa nodules naturally contain abundant and highly diverse populations of Micromonospora, both at the intra- and at interspecific level. Selected Micromonospora isolates significantly increase the nodulation of alfalfa by Ensifer meliloti 1021 and also the efficiency of the plant for nitrogen nutrition. Moreover, they promote aerial growth, the shoot-to-root ratio, and raise the level of essential nutrients. Our results indicate that Micromonospora acts as a Rhizobia Helper Bacteria (RHB) agent and has probiotic effects, promoting plant growth and increasing nutrition efficiency. Its ecological role, biotechnological potential and advantages as a plant probiotic bacterium (PPB) are also discussed.

  9. Micromonospora from nitrogen fixing nodules of alfalfa (Medicago sativa L.). A new promising Plant Probiotic Bacteria.

    PubMed Central

    Martínez-Hidalgo, Pilar; Galindo-Villardón, Purificación; Igual, José M.; Martínez-Molina, Eustoquio

    2014-01-01

    Biotic interactions can improve agricultural productivity without costly and environmentally challenging inputs. Micromonospora strains have recently been reported as natural endophytes of legume nodules but their significance for plant development and productivity has not yet been established. The aim of this study was to determine the diversity and function of Micromonospora isolated from Medicago sativa root nodules. Micromonospora-like strains from field alfalfa nodules were characterized by BOX-PCR fingerprinting and 16S rRNA gene sequencing. The ecological role of the interaction of the 15 selected representative Micromonospora strains was tested in M. sativa. Nodulation, plant growth and nutrition parameters were analyzed. Alfalfa nodules naturally contain abundant and highly diverse populations of Micromonospora, both at the intra- and at interspecific level. Selected Micromonospora isolates significantly increase the nodulation of alfalfa by Ensifer meliloti 1021 and also the efficiency of the plant for nitrogen nutrition. Moreover, they promote aerial growth, the shoot-to-root ratio, and raise the level of essential nutrients. Our results indicate that Micromonospora acts as a Rhizobia Helper Bacteria (RHB) agent and has probiotic effects, promoting plant growth and increasing nutrition efficiency. Its ecological role, biotechnological potential and advantages as a plant probiotic bacterium (PPB) are also discussed. PMID:25227415

  10. Lotus japonicus Cytokinin Receptors Work Partially Redundantly to Mediate Nodule Formation[W][OPEN

    PubMed Central

    Held, Mark; Hou, Hongwei; Miri, Mandana; Huynh, Christian; Ross, Loretta; Hossain, Md Shakhawat; Sato, Shusei; Tabata, Satoshi; Perry, Jillian; Wang, Trevor L.; Szczyglowski, Krzysztof

    2014-01-01

    Previous analysis of the Lotus histidine kinase1 (Lhk1) cytokinin receptor gene has shown that it is required and also sufficient for nodule formation in Lotus japonicus. The L. japonicus mutant carrying the loss-of-function lhk1-1 allele is hyperinfected by its symbiotic partner, Mesorhizobium loti, in the initial absence of nodule organogenesis. At a later time point following bacterial infection, lhk1-1 develops a limited number of nodules, suggesting the presence of an Lhk1-independent mechanism. We have tested a hypothesis that other cytokinin receptors function in at least a partially redundant manner with LHK1 to mediate nodule organogenesis in L. japonicus. We show here that L. japonicus contains a small family of four cytokinin receptor genes, which all respond to M. loti infection. We show that within the root cortex, LHK1 performs an essential role but also works partially redundantly with LHK1A and LHK3 to mediate cell divisions for nodule primordium formation. The LHK1 receptor is also presumed to partake in mediating a feedback mechanism that negatively regulates bacterial infections at the root epidermis. Interestingly, the Arabidopsis thaliana AHK4 receptor gene can functionally replace Lhk1 in mediating nodule organogenesis, indicating that the ability to perform this developmental process is not determined by unique, legume-specific properties of LHK1. PMID:24585837

  11. Controlling the expression of rhizobial genes during nodule development with elements and an inducer of the lac operon.

    PubMed

    Box, Jodie; Noel, K Dale

    2011-04-01

    A simple strategy was tested for imposing artificial regulation of rhizobial genes during nodule development. Isopropyl-β-d-1-thiogalactoside (IPTG) was added to liquid root media to sustain expression of rhizobial genes controlled by Escherichia coli lac promoter/operators and repressor gene lacI. Conversely, a rinsing protocol was devised to remove IPTG sufficiently that genes could be repressed after having been induced. gusA under this control exhibited clearly delineated expression and repression in both the determinate Rhizobium etli-Phaseolus vulgaris and the indeterminate Sinorhizobium meliloti-Medicago sativa symbioses. Apparently, IPTG was taken up in sufficiently undegraded concentrations that gene expression was derepressed even in interior portions of the nodule. Moreover, the rinsing protocol led to obvious repression of gusA. Importantly, no deleterious effects of IPTG on nodule development, infection, or nitrogen fixation were observed. An R. etli CE3 gene required for lipopolysaccharide O antigen and infection on bean was put under this control by means of a two-plasmid construct. When this construct was added to a strain with a null mutation in this gene, infection, nodule development, and nitrogenase activity all depended on the length of time before IPTG was rinsed from the roots after inoculation.

  12. Host legume-exuded antimetabolites optimize the symbiotic rhizosphere.

    PubMed

    Cai, Tao; Cai, Wentong; Zhang, Jiang; Zheng, Huiming; Tsou, Amy M; Xiao, Lin; Zhong, Zengtao; Zhu, Jun

    2009-08-01

    Rhizobia form symbiotic nodules on host legumes and fix nitrogen for their hosts in exchange for nutrients. In order to establish this mutually beneficial relationship, rhizobia must compete with other soil bacteria in the host legume rhizosphere to colonize plant roots efficiently. A promoter-trap transposon screen in Mesorhizobium tianshanense, a Rhizobium that forms nodules on licorice (Glycyrrhiza uralensis) plants revealed that the expression of msiA, which encodes a putative exporter protein belonging to the LysE family of translocators, is activated by both legume exudates and MsiR, a LysR family transcriptional regulator. Chemical analysis suggests that the msiA-inducing signal in exudates is canavanine, an anti-metabolite present in the seeds and exudates of a variety of legume plants. We show that MsiA serves as a canavanine exporter that is indispensable for canavanine resistance in M. tianshanense. We also show that the expression of MsiA homologues in other rhizobial species is induced by canavanine and is critical for canavanine resistance. Furthermore, rhizobial canavanine resistance is important for root hair adherence as well as for survival in a canavanine-producing legume rhizosphere. Together, these data suggest that host legumes may exude specific antimetabolites into their surroundings to optimize the bacterial population in order to have successful symbiotic events with rhizobia.

  13. [Genetic diversity of rhizobia isolated from common legumes in the Karst area. Northwest Guangxi].

    PubMed

    Liu, Lu; He, Xun-yang; Xie, Qiang; Wang, Ke-lin

    2015-12-01

    Legumes, with a strong resistance to the adverse environmental conditions, are pioneer plants in degraded habitats, and play an important role in ecosystem restoration. In this study, the nodulation characteristics of 24 legumes were surveyed in the Karst area of Northwest Guangxi. A total of 39 nodule samples were collected from 15 legumes, the DNA was extracted and the 16S rDNA and nifH gene were amplified. A phylogenetic tree was then constructed to analyze the genetic diversity of rhizobia. The results showed that 15 legumes were nodulated, of which 14 belonged to the Papilionoideae, one to the Mimosaceae, and none to the Caesalpinoideae. No nodules were found on some legumes that were reported as nodulated, which might result from soil water stress in Karst. BLAST result and phylogenetic analyse indicated that most of the legumes were associated with rhizobia that belonged to the genus Bradyrhizobium, with the exception of two samples from Callerya nitida that were associated with the genus Mesorhizobium. In the phylogenetic tree, the sequences obtained from the same plot or the sequences from the same host species clustered together in most cases. This finding suggested that host selection and the ecological environment are the major factors that influence the genotype of rhizobia.

  14. Development of a SIDA-LC-MS/MS Method for the Determination of Phomopsin A in Legumes.

    PubMed

    Schloß, Svenja; Koch, Matthias; Rohn, Sascha; Maul, Ronald

    2015-12-09

    A novel method for the determination of phomopsin A (1) in lupin flour, pea flour, and bean flour as well as whole lupin plants was established based on stable isotope dilution assay (SIDA) LC-MS/MS using (15)N6-1 as an isotopically labeled internal standard. Artificially infected samples were used to develop an optimized extraction procedure and sample pretreatment. The limits of detection were 0.5-1 μg/kg for all matrices. The limits of quantitation were 2-4 μg/kg. The method was used to analyze flour samples generated from selected legume seeds and lupin plant samples that had been inoculated with Diaporthe toxica and two further fungal strains. Finally, growing lupin plants infected with D. toxica were investigated to simulate a naturally in-field mycotoxicosis. Toxin levels of up to 10.1 μg/kg of 1 were found in the pods and 7.2 μg/kg in the stems and leaves.

  15. Manganese nodules

    USGS Publications Warehouse

    Hein, James R.; Harff, Jan; Petersen, Sven; Thiede, Jorn

    2016-01-01

    The existence of manganese (Mn) nodules (Figure 1) has been known since the late 1800s when they were collected during the Challenger expedition of 1873–1876. However, it was not until after WWII that nodules were further studied in detail for their ability to adsorb metals from seawater. Many of the early studies did not distinguish Mn nodules from Mn crusts. Economic interest in Mn nodules began in the late 1950s and early 1960s when John Mero finished his Ph.D. thesis on this subject, which was published in the journal Economic Geology (Mero, 1962) and later as a book (Mero, 1965). By the mid-1970s, large consortia had formed to search for and mine Mn nodules that occur between the Clarion and Clipperton fracture zones (CCZ) in the NE Pacific (Figure 2). This is still the area considered of greatest economic potential in the global ocean because of high nickel (Ni), copper (Cu), and Mn contents and the dense distribution of nodules in the area. While the mining of nodules was fully expected to begin in the late 1970s or early 1980s, this never occurred due to a downturn in the price of metals on the global market. Since then, many research cruises have been undertaken to study the CCZ nodules, and now 15 contracts for exploration sites have been given or are pending by the International Seabed Authority (ISA). Many books and science journal articles have been published summarizing the early work (e.g., Baturin, 1988; Halbach et al., 1988), and research has continued to the present day (e.g., ISA, 1999; ISA, 2010). Although the initial attraction for nodules was their high Ni, Cu, and Mn contents, subsequent work has shown that nodules host large quantities of other critical metals needed for high-tech, green-tech, and energy applications (Hein et al., 2013; Hein and Koschinsky, 2014).

  16. Impact of the energy crop Jatropha curcas L. on the composition of rhizobial populations nodulating cowpea (Vigna unguiculata L.) and acacia (Acacia seyal L.).

    PubMed

    Dieng, Amadou; Duponnois, Robin; Floury, Antoine; Laguerre, Gisèle; Ndoye, Ibrahima; Baudoin, Ezékiel

    2015-03-01

    Jatropha curcas, a Euphorbiaceae species that produces many toxicants, is increasingly planted as an agrofuel plant in Senegal. The purpose of this study was to determine whether soil priming induced by J. curcas monoculture could alter the rhizobial populations that nodulate cowpea and acacia, two locally widespread legumes. Soil samples were transferred into a greenhouse from three fields previously cultivated with Jatropha for 1, 2, and 15 years, and the two trap legumes were grown in them. Control soil samples were also taken from adjacent Jatropha-fallow plots. Both legumes tended to develop fewer but larger nodules when grown in Jatropha soils. Nearly all the nifH sequences amplified from nodule DNA were affiliated to the Bradyrhizobium genus. Only sequences from Acacia seyal nodules grown in the most recent Jatropha plantation were related to the Mesorhizobium genus, which was much a more conventional finding on A. seyal than the unexpected Bradyrhizobium genus. Apart from this particular case, only minor differences were found in the respective compositions of Jatropha soil versus control soil rhizobial populations. Lastly, the structure of these rhizobial populations was systematically imbalanced owing to the overwhelming dominance of a very small number of nifH genotypes, some of which were identical across soil types or even sites. Despite these weak and sparse effects on rhizobial diversity, future investigations should focus on the characterization of the nitrogen-fixing abilities of the predominant rhizobial strains.

  17. Legumes, N2 fixation and the H2 cycle

    NASA Astrophysics Data System (ADS)

    Layzell, D. B.

    2004-12-01

    Legume plants such as soybean or pea can form symbiotic, N2 fixing associations with bacteria that exist in root nodules. For every N2 fixed, 1 to 3 H2 are produced as a by-product of the nitrogenase reaction. Therefore, a typical N2 fixing legume crop produces about 200,000 L H2 gas (at STP) per hectare per crop season. This paper will summarize our current understanding of the processes leading to H2 production in legumes, the magnitude of H2 production associated with global cropping systems, and the implications for its production and oxidation on both the legumes and the soils in which they grow. Specific points may include: ˜ In symbioses lacking uptake hydrogenase (HUP) activity (thought to be the majority of crop legumes), the H2 diffuses into the soil where it is oxidized by soil microbes that grow up around the legume nodules. The kinetic properties of these microbes are very different (higher Km and Vmax) from that of microbes in soils exposed to normal air (ca. 0.5 ppm H2); ˜ Laboratory studies indicate that 60% of the reducing power from H2 is coupled to O2 uptake, whereas 40% is coupled to autotrophic CO2 fixation. The latter process should increase soil carbon stocks by about 25 kg C/ha/yr; ˜ At the site of the nitrogenase enzyme, H2 production is autocatalytic such that the higher the H2 concentration, the more H2 is produced and the less N2 fixed. The variable O2 diffusion barrier in legumes can act to restrict H2 diffusion from the nodule, thereby increasing the relative magnitude of H2 production versus N2 fixation; ˜ Studies to understand why legume symbioses make such an energy investment in H2 production have led to the discovery that H2 treated soils have improved fertility, supporting the growth and yield of legume and non-legume crops. This observation may account for the benefits of legumes when used in rotation with cereal crops, a phenomenon that has been used by farmers for over 2000 years, but which has remained unexplained. An

  18. Central focused convolutional neural networks: Developing a data-driven model for lung nodule segmentation.

    PubMed

    Wang, Shuo; Zhou, Mu; Liu, Zaiyi; Liu, Zhenyu; Gu, Dongsheng; Zang, Yali; Dong, Di; Gevaert, Olivier; Tian, Jie

    2017-08-01

    Accurate lung nodule segmentation from computed tomography (CT) images is of great importance for image-driven lung cancer analysis. However, the heterogeneity of lung nodules and the presence of similar visual characteristics between nodules and their surroundings make it difficult for robust nodule segmentation. In this study, we propose a data-driven model, termed the Central Focused Convolutional Neural Networks (CF-CNN), to segment lung nodules from heterogeneous CT images. Our approach combines two key insights: 1) the proposed model captures a diverse set of nodule-sensitive features from both 3-D and 2-D CT images simultaneously; 2) when classifying an image voxel, the effects of its neighbor voxels can vary according to their spatial locations. We describe this phenomenon by proposing a novel central pooling layer retaining much information on voxel patch center, followed by a multi-scale patch learning strategy. Moreover, we design a weighted sampling to facilitate the model training, where training samples are selected according to their degree of segmentation difficulty. The proposed method has been extensively evaluated on the public LIDC dataset including 893 nodules and an independent dataset with 74 nodules from Guangdong General Hospital (GDGH). We showed that CF-CNN achieved superior segmentation performance with average dice scores of 82.15% and 80.02% for the two datasets respectively. Moreover, we compared our results with the inter-radiologists consistency on LIDC dataset, showing a difference in average dice score of only 1.98%. Copyright © 2017. Published by Elsevier B.V.

  19. Phytosulfokine Is Involved in Positive Regulation of Lotus japonicus Nodulation.

    PubMed

    Wang, Chao; Yu, Haixiang; Zhang, Zhongming; Yu, Liangliang; Xu, Xiaoshu; Hong, Zonglie; Luo, Li

    2015-08-01

    Phytosulfokine (PSK) is a tyrosine-sulfated peptide that is widely distributed in plants, participating in cell proliferation, differentiation, and innate immunity. The potential role of PSK in nodulation in legumes has not been reported. In this work, five PSK precursor genes were identified in Lotus japonicas, designated as LjPSK1 to LjPSK5. Three of them (LjPSK1, LjPSK4, and LjPSK5) were found to be expressed in nitrogen-fixing root nodules. LjPSK1 and LjPSK4 were not induced at the early stage of nodulation. Interestingly, while the expression of LjPSK4 was also found in spontaneous nodules without rhizobial colonization, LjPSK1 was not induced in these pseudo nodules. Promoter-β-glucuronidase analysis revealed that LjPSK1 was highly expressed in enlarged symbiotic cells of nodules. Exogenous addition of 1 1M synthetic PSK peptide resulted in increased nodule numbers per plant. Consistently, the number of mature nodules but not the events of rhizobial infection and nodule initiation was increased by overexpressing LjPSK1 in transgenic hairy roots, in which the expression of jasmonate-responsive genes was found to be repressed. These results suggest that PSK is a new peptide signal that regulates nodulation in legumes, probably through cross-talking with other phytohormones.

  20. Host-specific Nod-factors associated with Medicago truncatula nodule infection differentially induce calcium influx and calcium spiking in root hairs

    PubMed Central

    Morieri, Giulia; Martinez, Eduardo A; Jarynowski, Andrzej; Driguez, Hugues; Morris, Richard; Oldroyd, Giles E D; Downie, J Allan

    2013-01-01

    Rhizobial nodulation (Nod) factors activate both nodule morphogenesis and infection thread development during legume nodulation. Nod factors induce two different calcium responses: intra-nuclear calcium oscillations and a calcium influx at the root hair tip. Calcium oscillations activate nodule development; we wanted to test if the calcium influx is associated with infection. Sinorhizobium meliloti nodL and nodF mutations additively reduce infection of Medicago truncatula. Nod-factors made by the nodL mutant lack an acetyl group; mutation of nodF causes the nitrogen (N)-linked C16:2 acyl chain to be replaced by C18:1. We tested whether these Nod-factors differentially induced calcium influx and calcium spiking. The absence of the NodL-determined acetyl group greatly reduced the induction of calcium influx without affecting calcium spiking. The calcium influx was even further reduced if the N-linked C16:2 acyl group was replaced by C18:1. These additive effects on calcium influx correlate with the additive effects of mutations in nodF and nodL on legume infection. Infection thread development is inhibited by ethylene, which also inhibited Nod-factor-induced calcium influx. We conclude that Nod-factor perception differentially activates the two developmental pathways required for nodulation and that activation of the pathway involving the calcium influx is important for efficient infection. PMID:24015832

  1. Correlation of endogenous free polyamine levels with root nodule senescence in different genotypes in Vigna mungo L.

    PubMed

    Lahiri, Kajari; Chattopadhyay, Soumen; Ghosh, Bharati

    2004-05-01

    Endogenous free polyamines, nitrogenase (EC 1.1.8.6.1, acetylene reduction), and leghaemoglobin (pyridine-hemochrome assay) levels were compared among five genotypes of developing Vigna root nodules grown under field conditions. Nitrogenase activity and leghaemoglobin level attained a peak at the flowering stage and gradually declined thereafter. Individual and total polyamine also followed the same pattern. Ranking on the basis of legume yield and other morphometric attributes was PDU-2 > UH-28 > UH-82 > T-9 > Sardhomash. Except spermine, the levels of putrescine, spermidine, and total polyamine showed significant differences (p<0.05) amongst the genotypes, particularly from flowering to mid-pod development stage. Genotype, development stage, and their interaction between the two had significant (p<0.01) effects on individual as well as total polyamines. Moreover, significant high linear correlations were found between total free polyamine and putrescine with conventional nodule senescence marker like nitrogenase (R2 = 0.94 and R2 = 0.92, respectively). Putrescine had an overall positive correlation with high legume yield. The results strongly suggest a relationship between polyamine and nodule senescence. Endogenous free polyamine and putrescine may be considered as genotypic markers for nodule senescence in field grown V. mungo. It is suggested that the flowering stage is more suitable for selection.

  2. Root developmental programs shape the Medicago truncatula nodule meristem.

    PubMed

    Franssen, Henk J; Xiao, Ting Ting; Kulikova, Olga; Wan, Xi; Bisseling, Ton; Scheres, Ben; Heidstra, Renze

    2015-09-01

    Nodules on the roots of legume plants host nitrogen-fixing Rhizobium bacteria. Several lines of evidence indicate that nodules are evolutionarily related to roots. We determined whether developmental control of the Medicago truncatula nodule meristem bears resemblance to that in root meristems through analyses of root meristem-expressed PLETHORA genes. In nodules, MtPLETHORA 1 and 2 are preferentially expressed in cells positioned at the periphery of the meristem abutting nodule vascular bundles. Their expression overlaps with an auxin response maximum and MtWOX5, which is a marker for the root quiescent center. Strikingly, the cells in the central part of the nodule meristem have a high level of cytokinin and display MtPLETHORA 3 and 4 gene expression. Nodule-specific knockdown of MtPLETHORA genes results in a reduced number of nodules and/or in nodules in which meristem activity has ceased. Our nodule gene expression map indicates that the nodule meristem is composed of two distinct domains in which different MtPLETHORA gene subsets are expressed. Our mutant studies show that MtPLETHORA genes function redundantly in nodule meristem maintenance. This indicates that Rhizobium has recruited root developmental programs for nodule formation. © 2015. Published by The Company of Biologists Ltd.

  3. Recent technological and application developments in computed tomography and magnetic resonance imaging for improved pulmonary nodule detection and lung cancer staging

    PubMed Central

    Sieren, Jessica C.; Ohno, Yoshiharu; Koyama, Hisanobu; Sugimura, Kazuro; McLennan, Geoffrey

    2010-01-01

    This review compares the emerging technologies and approaches in the application of magnetic resonance (MR) and computed tomography (CT) imaging for the assessment of pulmonary nodules and staging of malignant findings. Included in this review is a brief definition of pulmonary nodules and an introduction to the challenges faced. We have highlighted the current status of both MR and CT for the early detection of lung nodules. Developments are detailed in this review for the management of pulmonary nodules using advanced imaging, including; dynamic imaging studies, dual energy CT, computer aided detection and diagnosis, and imaging assisted nodule biopsy approaches which have improved lung nodule detection and diagnosis rates. Recent advancements linking in-vivo imaging to corresponding histological pathology are also highlighted. In-vivo imaging plays a pivotal role in the clinical staging of pulmonary nodules through TNM assessment. While CT and PET/CT are currently the most commonly clinically employed modalities for pulmonary nodule staging, studies are presented which highlight the augmentative potential of MR. PMID:21105140

  4. Final Report Grant No. DE-FG02-98ER20307 Lipopolysaccharide Structures and Genes Required for Root Nodule Development August 1, 2004 to July 31, 2008

    SciTech Connect

    Noel, K. Dale

    2008-12-07

    This project dealt with the plant-bacterial symbiosis that gives rise to root nodules on leguminous plants in which the bacteria carry out nitrogen fixation. Nitrogen fixation, like carbon dioxide fixation, is essential for life on planet earth, and this symbiosis is estimated to account for half of all nitrogen fixed on land. Aside from being important for the sustenance of global life, this ability allows legumes to grow without nitrogen fertilizers. Basic studies such as this project are aimed at understanding the symbiosis well enough that eventually it can be engineered into important crop species so that they no longer depend on nitrogen fertilizer for growth. The production and distribution of excessive fertilizer needed for optimal crop yields is responsible for a significant portion of the energy costs in agriculture. The specific aims of this work were to further the understanding of a bacterial factor that is essential for the symbiotic infection process. This factor is a bacterial surface molecule, lipopolysaccharide O antigen. In this project we showed that, not only the presence, but the specific structure of this molecule is crucial for infection. Although the success of bacterial infections in many pathogenic and mutualistic interactions have been shown to depend on intact O antigen, it has been very rare to establish that specific features of the structure are important. One of the features in this case is the presence of one additional methyl group on one sugar in the O antigen. It is very surprising that such a minor change should have an observable effect. This work sets the stage for biochemical studies of possible plant receptors that may be involved. During the course of this grant period, we developed a method of testing the importance of this bacterial component at stages of nodule development beyond the step that is blocked by null mutation. The method works adequately for this purpose and is being improved. It has implications for testing

  5. Differentiation of Symbiotic Cells and Endosymbionts in Medicago truncatula Nodulation Are Coupled to Two Transcriptome-Switches

    PubMed Central

    Maunoury, Nicolas; Redondo-Nieto, Miguel; Bourcy, Marie; Van de Velde, Willem; Alunni, Benoit; Laporte, Philippe; Durand, Patricia; Agier, Nicolas; Marisa, Laetitia; Vaubert, Danièle; Delacroix, Hervé; Duc, Gérard; Ratet, Pascal; Aggerbeck, Lawrence; Kondorosi, Eva; Mergaert, Peter

    2010-01-01

    The legume plant Medicago truncatula establishes a symbiosis with the nitrogen-fixing bacterium Sinorhizobium meliloti which takes place in root nodules. The formation of nodules employs a complex developmental program involving organogenesis, specific cellular differentiation of the host cells and the endosymbiotic bacteria, called bacteroids, as well as the specific activation of a large number of plant genes. By using a collection of plant and bacterial mutants inducing non-functional, Fix− nodules, we studied the differentiation processes of the symbiotic partners together with the nodule transcriptome, with the aim of unravelling links between cell differentiation and transcriptome activation. Two waves of transcriptional reprogramming involving the repression and the massive induction of hundreds of genes were observed during wild-type nodule formation. The dominant features of this “nodule-specific transcriptome” were the repression of plant defense-related genes, the transient activation of cell cycle and protein synthesis genes at the early stage of nodule development and the activation of the secretory pathway along with a large number of transmembrane and secretory proteins or peptides throughout organogenesis. The fifteen plant and bacterial mutants that were analyzed fell into four major categories. Members of the first category of mutants formed non-functional nodules although they had differentiated nodule cells and bacteroids. This group passed the two transcriptome switch-points similarly to the wild type. The second category, which formed nodules in which the plant cells were differentiated and infected but the bacteroids did not differentiate, passed the first transcriptome switch but not the second one. Nodules in the third category contained infection threads but were devoid of differentiated symbiotic cells and displayed a root-like transcriptome. Nodules in the fourth category were free of bacteria, devoid of differentiated symbiotic

  6. A receptor kinase gene of the LysM type is involved in legume perception of rhizobial signals.

    PubMed

    Madsen, Esben Bjørn; Madsen, Lene Heegaard; Radutoiu, Simona; Olbryt, Magdalena; Rakwalska, Magdalena; Szczyglowski, Krzysztof; Sato, Shusei; Kaneko, Takakazu; Tabata, Satoshi; Sandal, Niels; Stougaard, Jens

    2003-10-09

    Plants belonging to the legume family develop nitrogen-fixing root nodules in symbiosis with bacteria commonly known as rhizobia. The legume host encodes all of the functions necessary to build the specialized symbiotic organ, the nodule, but the process is elicited by the bacteria. Molecular communication initiates the interaction, and signals, usually flavones, secreted by the legume root induce the bacteria to produce a lipochitin-oligosaccharide signal molecule (Nod-factor), which in turn triggers the plant organogenic process. An important determinant of bacterial host specificity is the structure of the Nod-factor, suggesting that a plant receptor is involved in signal perception and signal transduction initiating the plant developmental response. Here we describe the cloning of a putative Nod-factor receptor kinase gene (NFR5) from Lotus japonicus. NFR5 is essential for Nod-factor perception and encodes an unusual transmembrane serine/threonine receptor-like kinase required for the earliest detectable plant responses to bacteria and Nod-factor. The extracellular domain of the putative receptor has three modules with similarity to LysM domains known from peptidoglycan-binding proteins and chitinases. Together with an atypical kinase domain structure this characterizes an unusual receptor-like kinase.

  7. Large-scale microsatellite development in grasspea (Lathyrus sativus L.), an orphan legume of the arid areas

    USDA-ARS?s Scientific Manuscript database

    Grasspea (Lathyrus sativus L., 2n = 14), a member of the family Leguminosae, holds great agronomic potential as grain and forage legume crop in the arid areas for its superb resilience to abiotic stresses such as drought, flood and salinity. The crop could not make much progress through conventional...

  8. Transcriptome sequencing, and rapid development and application of SNP markers for the legume pod borer Maruca vitrata (Lepidoptera: Crambidae)

    USDA-ARS?s Scientific Manuscript database

    The legume pod borer, Maruca vitrata (Lepidoptera: Crambidae), is an insect pest species that is destructive to crops grown by subsistence farmers in tropical regions of West Africa. We present the de novo assembly of 3729 contigs from 454- and Sanger-derived sequencing reads for midgut, salivary, ...

  9. Forage legumes - untrapped resource

    SciTech Connect

    Barnes, R.F.

    1985-02-01

    Legumes are important in nutrition, nitrogen fixation and in reducing dependence on nitrogen fertilizers. At a meeting between scientists from Australia, New Zealand and the United States the role of legumes was assessed and coordinated research programs set up to deal with problems such as disease, soil, climate and selective breeding.

  10. Development and evaluation of a computer-aided diagnostic scheme for lung nodule detection in chest radiographs by means of two-stage nodule enhancement with support vector classification

    SciTech Connect

    Chen Sheng; Suzuki, Kenji; MacMahon, Heber

    2011-04-15

    Purpose: To develop a computer-aided detection (CADe) scheme for nodules in chest radiographs (CXRs) with a high sensitivity and a low false-positive (FP) rate. Methods: The authors developed a CADe scheme consisting of five major steps, which were developed for improving the overall performance of CADe schemes. First, to segment the lung fields accurately, the authors developed a multisegment active shape model. Then, a two-stage nodule-enhancement technique was developed for improving the conspicuity of nodules. Initial nodule candidates were detected and segmented by using the clustering watershed algorithm. Thirty-one shape-, gray-level-, surface-, and gradient-based features were extracted from each segmented candidate for determining the feature space, including one of the new features based on the Canny edge detector to eliminate a major FP source caused by rib crossings. Finally, a nonlinear support vector machine (SVM) with a Gaussian kernel was employed for classification of the nodule candidates. Results: To evaluate and compare the scheme to other published CADe schemes, the authors used a publicly available database containing 140 nodules in 140 CXRs and 93 normal CXRs. The CADe scheme based on the SVM classifier achieved sensitivities of 78.6% (110/140) and 71.4% (100/140) with averages of 5.0 (1165/233) FPs/image and 2.0 (466/233) FPs/image, respectively, in a leave-one-out cross-validation test, whereas the CADe scheme based on a linear discriminant analysis classifier had a sensitivity of 60.7% (85/140) at an FP rate of 5.0 FPs/image. For nodules classified as ''very subtle'' and ''extremely subtle,'' a sensitivity of 57.1% (24/42) was achieved at an FP rate of 5.0 FPs/image. When the authors used a database developed at the University of Chicago, the sensitivities was 83.3% (40/48) and 77.1% (37/48) at an FP rate of 5.0 (240/48) FPs/image and 2.0 (96/48) FPs /image, respectively. Conclusions: These results compare favorably to those described for

  11. Initial development of a computer-aided diagnosis tool for solitary pulmonary nodules

    NASA Astrophysics Data System (ADS)

    Catarious, David M., Jr.; Baydush, Alan H.; Floyd, Carey E., Jr.

    2001-07-01

    This paper describes the development of a computer-aided diagnosis (CAD) tool for solitary pulmonary nodules. This CAD tool is built upon physically meaningful features that were selected because of their relevance to shape and texture. These features included a modified version of the Hotelling statistic (HS), a channelized HS, three measures of fractal properties, two measures of spicularity, and three manually measured shape features. These features were measured from a difficult database consisting of 237 regions of interest (ROIs) extracted from digitized chest radiographs. The center of each 256x256 pixel ROI contained a suspicious lesion which was sent to follow-up by a radiologist and whose nature was later clinically determined. Linear discriminant analysis (LDA) was used to search the feature space via sequential forward search using percentage correct as the performance metric. An optimized feature subset, selected for the highest accuracy, was then fed into a three layer artificial neural network (ANN). The ANN's performance was assessed by receiver operating characteristic (ROC) analysis. A leave-one-out testing/training methodology was employed for the ROC analysis. The performance of this system is competitive with that of three radiologists on the same database.

  12. Development and comparison of shelf stable extended and dehydrated goat meat cubes containing four different legume based binder mixes.

    PubMed

    Nayar, Renuka; Mendiratta, S K; Prabhakaran, P P; Chand, Sagar; Sharma, B D

    2015-07-01

    A study was undertaken to develop shelf stable hot air oven dried goat meat cubes extended with different legume based binder mixes. Based on preliminary trials, four different formulations containing 80 % meat mince + 10 % Bengal gram based binder mix (HBE), 70 % meat mince + 20 % green gram based binder mix (HGR), 80 % meat mince + 10 % black gram based binder mix (HBL) and 80 % meat mince + 10 % lentil based binder mix (HLE) were selected and subjected to physico-chemical, microbiological and sensory characteristics. Among treatments, HGR showed a significantly higher pH (6.53 ± 0.01), whereas there was no significant difference in other physico-chemical parameters. Moisture content (10.37 ± 1.06 %) was highest in HLE, while protein (49.68 ± 1.78 %) and ash (8.71 ± 0.30 %) contents were higher in HBL. On texture profile analysis, hardness, gumminess and chewiness parameters were highest for HLE and lowest for HBL. In all treatments, total plate, Staphylococcus aureus and yeast and mold counts were in acceptable range and coliforms were not detected. Scores for sensory attributes of rehydrated cubes were in good to very good range in all treatments, however, higher scores for appearance, flavour, texture, juiciness and overall acceptability were observed in HBL. The dehydrated cubes could be used to prepare curry within few minutes and is a boon to busy housewives.

  13. A Medicago truncatula Tobacco Retrotransposon Insertion Mutant Collection with Defects in Nodule Development and Symbiotic Nitrogen Fixation1[W][OA

    PubMed Central

    Pislariu, Catalina I.; D. Murray, Jeremy; Wen, JiangQi; Cosson, Viviane; Muni, RajaSekhara Reddy Duvvuru; Wang, Mingyi; A. Benedito, Vagner; Andriankaja, Andry; Cheng, Xiaofei; Jerez, Ivone Torres; Mondy, Samuel; Zhang, Shulan; Taylor, Mark E.; Tadege, Million; Ratet, Pascal; Mysore, Kirankumar S.; Chen, Rujin; Udvardi, Michael K.

    2012-01-01

    A Tnt1-insertion mutant population of Medicago truncatula ecotype R108 was screened for defects in nodulation and symbiotic nitrogen fixation. Primary screening of 9,300 mutant lines yielded 317 lines with putative defects in nodule development and/or nitrogen fixation. Of these, 230 lines were rescreened, and 156 lines were confirmed with defective symbiotic nitrogen fixation. Mutants were sorted into six distinct phenotypic categories: 72 nonnodulating mutants (Nod−), 51 mutants with totally ineffective nodules (Nod+ Fix−), 17 mutants with partially ineffective nodules (Nod+ Fix+/−), 27 mutants defective in nodule emergence, elongation, and nitrogen fixation (Nod+/− Fix−), one mutant with delayed and reduced nodulation but effective in nitrogen fixation (dNod+/− Fix+), and 11 supernodulating mutants (Nod++Fix+/−). A total of 2,801 flanking sequence tags were generated from the 156 symbiotic mutant lines. Analysis of flanking sequence tags revealed 14 insertion alleles of the following known symbiotic genes: NODULE INCEPTION (NIN), DOESN’T MAKE INFECTIONS3 (DMI3/CCaMK), ERF REQUIRED FOR NODULATION, and SUPERNUMERARY NODULES (SUNN). In parallel, a polymerase chain reaction-based strategy was used to identify Tnt1 insertions in known symbiotic genes, which revealed 25 additional insertion alleles in the following genes: DMI1, DMI2, DMI3, NIN, NODULATION SIGNALING PATHWAY1 (NSP1), NSP2, SUNN, and SICKLE. Thirty-nine Nod− lines were also screened for arbuscular mycorrhizal symbiosis phenotypes, and 30 mutants exhibited defects in arbuscular mycorrhizal symbiosis. Morphological and developmental features of several new symbiotic mutants are reported. The collection of mutants described here is a source of novel alleles of known symbiotic genes and a resource for cloning novel symbiotic genes via Tnt1 tagging. PMID:22679222

  14. Competition Experiments for Legume Infection Identify Burkholderia phymatum as a Highly Competitive β-Rhizobium

    PubMed Central

    Lardi, Martina; de Campos, Samanta Bolzan; Purtschert, Gabriela; Eberl, Leo; Pessi, Gabriella

    2017-01-01

    Members of the genus Burkholderia (β-proteobacteria) have only recently been shown to be able to establish a nitrogen-fixing symbiosis with several legumes, which is why they are also referred to as β-rhizobia. Therefore, very little is known about the competitiveness of these species to nodulate different legume host plants. In this study, we tested the competitiveness of several Burkholderia type strains (B. diazotrophica, B. mimosarum, B. phymatum, B. sabiae, B. symbiotica and B. tuberum) to nodulate four legumes (Phaseolus vulgaris, Macroptilium atropurpureum, Vigna unguiculata and Mimosa pudica) under our closely defined growth conditions. The assessment of nodule occupancy of these species on different legume host plants revealed that B. phymatum was the most competitive strain in the three papilionoid legumes (bean, cowpea and siratro), while B. mimosarum outcompeted the other strains in mimosa. The analysis of phenotypes known to play a role in nodulation competitiveness (motility, exopolysaccharide production) and additional in vitro competition assays among β-rhizobial strains suggested that B. phymatum has the potential to be a very competitive legume symbiont. PMID:28861050

  15. Legume receptors perceive the rhizobial lipochitin oligosaccharide signal molecules by direct binding

    PubMed Central

    Broghammer, Angelique; Krusell, Lene; Blaise, Mickaël; Sauer, Jørgen; Sullivan, John T.; Maolanon, Nicolai; Vinther, Maria; Lorentzen, Andrea; Madsen, Esben B.; Jensen, Knud J.; Roepstorff, Peter; Thirup, Søren; Ronson, Clive W.; Thygesen, Mikkel B.; Stougaard, Jens

    2012-01-01

    Lipochitin oligosaccharides called Nod factors function as primary rhizobial signal molecules triggering legumes to develop new plant organs: root nodules that host the bacteria as nitrogen-fixing bacteroids. Here, we show that the Lotus japonicus Nod factor receptor 5 (NFR5) and Nod factor receptor 1 (NFR1) bind Nod factor directly at high-affinity binding sites. Both receptor proteins were posttranslationally processed when expressed as fusion proteins and extracted from purified membrane fractions of Nicotiana benthamiana or Arabidopsis thaliana. The N-terminal signal peptides were cleaved, and NFR1 protein retained its in vitro kinase activity. Processing of NFR5 protein was characterized by determining the N-glycosylation patterns of the ectodomain. Two different glycan structures with identical composition, Man3XylFucGlcNAc4, were identified by mass spectrometry and located at amino acid positions N68 and N198. Receptor–ligand interaction was measured by using ligands that were labeled or immobilized by application of chemoselective chemistry at the anomeric center. High-affinity ligand binding was demonstrated with both solid-phase and free solution techniques. The Kd values obtained for Nod factor binding were in the nanomolar range and comparable to the concentration range sufficient for biological activity. Structure-dependent ligand specificity was shown by using chitin oligosaccharides. Taken together, our results suggest that ligand recognition through direct ligand binding is a key step in the receptor-mediated activation mechanism leading to root nodule development in legumes. PMID:22859506

  16. Effects of nano-ZnO on the agronomically relevant Rhizobium-legume symbiosis.

    PubMed

    Huang, Yu Chu; Fan, Ruimei; Grusak, Michael A; Sherrier, Janine D; Huang, C P

    2014-11-01

    The impact of nano-ZnO (nZnO) on Rhizobium-legume symbiosis was studied with garden pea and its compatible bacterial partner Rhizobium leguminosarum bv. viciae 3841. Exposure of peas to nZnO had no impact on germination, but significantly affected root length. Chronic exposure of plant to nZnO impacted its development by decreasing the number of the first- and the second-order lateral roots, stem length, leaf surface area, and transpiration. The effect of nZnO dissolution on phytotoxicity was also examined. Results showed that Zn(2+) had negative impact on plant development. Exposure of R. leguminosarum bv. viciae 3841 to nZnO brought about morphological changes by rendering the microbial cells toward round shape and damaging the bacterial surface. Furthermore, the presence of nZnO in the rhizosphere affected root nodulation, delayed the onset of nitrogen fixation, and caused early senescence of nodules. Attachment of nanoparticles on the root surface and dissolution of Zn(2+) are important factors affecting the phytotocity of nZnO. Hence, the presence of nZnO in the environment is potentially hazardous to the Rhizobium-legume symbiosis system.

  17. Characterization of the common bean uricase II and its expression in organs other than nodules.

    PubMed Central

    Capote-Maínez, N; Sánchez, F

    1997-01-01

    Uricase II is a purine metabolic enzyme highly induced in root nodules during the symbiosis established between legumes and bacteria of the genera Rhizobium and Bradyrhizobium. Here we describe the characterization of bean (Phaseolus vulgaris) nodule uricase II cDNA and show that uricase II is encoded by a single gene in the bean genome. This gene is also expressed in cotyledons, roots, and hypocotyls during bean seedling establishment, and an anti-uricase antibody recognizes the protein in different seedling organs. Uricase II has also been found in Leucaena leucocephala seedlings, suggesting that it participates during seedling establishment in legumes that do not transport ureides. A 50-kD polypeptide that is detected by the anti-uricase antibody is found in cotyledons during seedling development. This higher-molecular-mass form is also detected in developing roots and hypocotyls but not in nodules. In situ hybridization experiments in root seedlings showed uricase II transcripts in the metaxylem parenchyma cells and phloem fibers of the vascular system. PMID:9414545

  18. Characterization of the common bean uricase II and its expression in organs other than nodules.

    PubMed

    Capote-Maínez, N; Sánchez, F

    1997-12-01

    Uricase II is a purine metabolic enzyme highly induced in root nodules during the symbiosis established between legumes and bacteria of the genera Rhizobium and Bradyrhizobium. Here we describe the characterization of bean (Phaseolus vulgaris) nodule uricase II cDNA and show that uricase II is encoded by a single gene in the bean genome. This gene is also expressed in cotyledons, roots, and hypocotyls during bean seedling establishment, and an anti-uricase antibody recognizes the protein in different seedling organs. Uricase II has also been found in Leucaena leucocephala seedlings, suggesting that it participates during seedling establishment in legumes that do not transport ureides. A 50-kD polypeptide that is detected by the anti-uricase antibody is found in cotyledons during seedling development. This higher-molecular-mass form is also detected in developing roots and hypocotyls but not in nodules. In situ hybridization experiments in root seedlings showed uricase II transcripts in the metaxylem parenchyma cells and phloem fibers of the vascular system.

  19. Negotiation of mutualism: rhizobia and legumes

    PubMed Central

    Akçay, Erol; Roughgarden, Joan

    2006-01-01

    The evolution and persistence of biological cooperation have been an important puzzle in evolutionary theory. Here, we suggest a new approach based on bargaining theory to tackle the question. We present a mechanistic model for negotiation of benefits between a nitrogen-fixing nodule and a legume plant. To that end, we first derive growth rates for the nodule and plant from metabolic models of each as a function of material fluxes between them. We use these growth rates as pay-off functions in the negotiation process, which is analogous to collective bargaining between a firm and a workers' union. Our model predicts that negotiations lead to the Nash bargaining solution, maximizing the product of players' pay-offs. This work introduces elements of cooperative game theory into the field of mutualistic interactions. In the discussion of the paper, we argue for the benefits of such an approach in studying the question of biological cooperation. PMID:17015340

  20. Coordinated changes in storage proteins during development and germination of elite seeds of Pongamia pinnata, a versatile biodiesel legume

    PubMed Central

    Kesari, Vigya; Rangan, Latha

    2011-01-01

    Background and aims The oleaginous legume Pongamia pinnata is a rapidly growing and economically important tree. The seeds are used increasingly as feedstock for biodiesel production, with the protein-rich residue providing valuable supplement to farm animal diets. However, little is known about seed development and the characteristics of germination. We therefore studied morphological, protein and ultrastructural changes during seed maturation and germination using seeds from a tree selected for superior morphological and reproductive characters (candidate plus tree). Methodology Phenology, sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE), and scanning and transmission electron microscopy were used to investigate seed development from 90 to 350 days after flowering (DAF), and germination and seedling development from 0 to 45 days after the start of imbibition (DAI) (Stages 0–VII). Principal results Seven distinct developmental stages were identified during seed development. Fresh weight, length, breadth and thickness increased from Stage I (90 DAF) to V (270 DAF) and decreased at Stages VI (315 DAF) and VII (350 DAF), when the seeds were fully ripe. Marked changes in total soluble protein content and SDS–PAGE profile were observed in vegetative and reproductive tissues and in the cotyledons of germinating seedlings. Polypeptide fragments of 150–14 kDa were observed during seed maturation and germination. In SDS–PAGE the expression of three main polypeptide bands (50, 18 and 14 kDa) increased from Stage I to Stage V and then almost became the same until Stage VII during seed maturation. During germination the expression of 50 kDa polypeptide decreased and that of 18 and 14 kDa increased from Stage 0 (ungerminated seed) to Stage VI (30 DAI), respectively; however, all three polypeptides (50, 18 and 14 kDa) completely disappeared at Stage VII (45 DAI). Ultrastructural changes during four stages of seed maturation (early immature, 90

  1. Nitric oxide detoxification in the rhizobia-legume symbiosis.

    PubMed

    Sánchez, Cristina; Cabrera, Juan J; Gates, Andrew J; Bedmar, Eulogio J; Richardson, David J; Delgado, María J

    2011-01-01

    NO (nitric oxide) is a signal molecule involved in diverse physiological processes in cells which can become very toxic under certain conditions determined by its rate of production and diffusion. Several studies have clearly shown the production of NO in early stages of rhizobia-legume symbiosis and in mature nodules. In functioning nodules, it has been demonstrated that NO, which has been reported as a potent inhibitor of nitrogenase activity, can bind Lb (leghaemoglobin) to form LbNOs (nitrosyl-leghaemoglobin complexes). These observations have led to the question of how nodules overcome the toxicity of NO. On the bacterial side, one candidate for NO detoxification in nodules is the respiratory Nor (NO reductase) that catalyses the reduction of NO to nitrous oxide. In addition, rhizobial fHbs (flavohaemoglobins) and single-domain Hbs which dioxygenate NO to form nitrate are candidates to detoxify NO under free-living and symbiotic conditions. On the plant side, sHbs (symbiotic Hbs) (Lb) and nsHbs (non-symbiotic Hbs) have been proposed to play important roles as modulators of NO levels in the rhizobia-legume symbiosis. In the present review, current knowledge of NO detoxification by legume-associated endosymbiotic bacteria is summarized.

  2. Wide distribution range of rhizobial symbionts associated with pantropical sea-dispersed legumes.

    PubMed

    Bamba, Masaru; Nakata, Sayuri; Aoki, Seishiro; Takayama, Koji; Núñez-Farfán, Juan; Ito, Motomi; Miya, Masaki; Kajita, Tadashi

    2016-12-01

    To understand the geographic distributions of rhizobia that associated with widely distributed wild legumes, 66 nodules obtained from 41 individuals including three sea-dispersed legumes (Vigna marina, Vigna luteola, and Canavalia rosea) distributed across the tropical and subtropical coastal regions of the world were studied. Partial sequences of 16S rRNA and nodC genes extracted from the nodules showed that only Bradyrhizobium and Sinorhizobium were associated with the pantropical legumes, and some of the symbiont strains were widely distributed over the Pacific. Horizontal gene transfer of nodulation genes were observed within the Bradyrhizobium and Sinorhizobium lineages. BLAST searches in GenBank also identified records of these strains from various legumes across the world, including crop species. However, one of the rhizobial strains was not found in GenBank, which implies the strain may have adapted to the littoral environment. Our results suggested that some rhizobia, which associate with the widespread sea-dispersed legume, distribute across a broad geographic range. By establishing symbiotic relationships with widely distributed rhizobia, the pantropical legumes may also be able to extend their range much further than other legume species.

  3. SUBFOVEAL NODULE IN COATS' DISEASE

    PubMed Central

    Daruich, Alejandra L.; Moulin, Alexandre P.; Tran, Hoai V.; Matet, Alexandre

    2017-01-01

    Purpose: To determine the prevalence, clinical characteristics and nature of subfoveal nodules in Coats' disease and the associated impact on the long-term visual outcome. Methods: Consecutive cases of Coats' disease with foveal exudation were retrospectively reviewed. The presence of a subfoveal nodule or macular fibrosis was recorded. Clinical characteristics, retinal imaging, and outcome were analyzed by comparative analysis. The histopathological description of an enucleated eye with subfoveal nodule was performed. Results: Among 40 patients presenting unilateral Stage 2B or 3A1 Coats' disease, a subfoveal nodule was detected in 21 patients (52.5%). The median follow-up was 4.7 years. Nineteen patients (47.5%) did not present a subfoveal nodule. Three patients (15.8%) without subfoveal nodule and 21 patients (100%) with subfoveal nodule progressed to a macular fibrotic scar (P < 0.0001), and the mean time of macular fibrosis onset was 11.0 ± 2.6 months. Final visual acuity was significantly worse in patients who presented a subfoveal nodule at diagnosis (P = 0.01). Of 18 cases with subfoveal nodule who underwent fluorescein angiography, retinal–retinal anastomosis and neovascularization were detected in 13 (72.2%) and 2 eyes (11.1%), respectively. Histopathological analysis of a subfoveal nodule revealed an aggregate of proteinaceous material including fibrin, spindle cells, macrophages, and pigmented cells. Conclusion: The presence of a subfoveal nodule at presentation is a predictive factor for macular fibrosis development and worse visual outcome in patients with Coats' disease. These observations suggest an updated classification introducing two subcategories within Stage 2B: without subfoveal nodule (Stage 2B1) and with subfoveal nodule (Stage 2B2). PMID:28030429

  4. Nod factors stimulate seed germination and promote growth and nodulation of pea and vetch under competitive conditions.

    PubMed

    Kidaj, Dominika; Wielbo, Jerzy; Skorupska, Anna

    2012-03-20

    Nod factors are lipochitooligosaccharide (LCO) produced by soil bacteria commonly known as rhizobia acting as signals for the legume plants to initiate symbiosis. Nod factors trigger early symbiotic responses in plant roots and initiate the development of specialized plant organs called nodules, where biological nitrogen fixation takes place. Here, the effect of specific LCO originating from flavonoid induced Rhizobium leguminosarum bv. viciae GR09 culture was studied on germination, plant growth and nodulation of pea and vetch. A crude preparation of GR09 LCO significantly enhanced symbiotic performance of pea and vetch grown under laboratory conditions and in the soil. Moreover, the effect of GR09 LCOs seed treatments on the genetic diversity of rhizobia recovered from vetch and pea nodules was presented.

  5. Mapping and identification of a Cicer arietinum NSP2 gene involved in nodulation pathway.

    PubMed

    Ali, L; Madrid, E; Varshney, R K; Azam, S; Millan, T; Rubio, J; Gil, J

    2014-02-01

    For the first time the putative NSP2 gene in chickpea has been identified using pairs of NILs differing for the Rn1 / rn1 nodulation gene that was located in LG5 of chickpea genetic map. An intraspecific cross between the mutant non-nodulating genotype PM233, carrying the recessive gene rn1, and the wild-type CA2139 was used to develop two pairs of near-isogenic lines (NILs) for nodulation in chickpea. These pairs of NILs were characterized using sequence tagged microsatellite site (STMS) markers distributed across different linkage groups (LGs) of the chickpea genetic map leading to the detection of polymorphic markers located in LG5. Using this information, together with the genome annotation in Medicago truncatula, a candidate gene (NSP2) known to be involved in nodulation pathway was selected for mapping in chickpea. The full length sequence obtained in chickpea wild-type (CaNSP2) was 1,503 bp. Linkage analysis in an F3 population of 118 plants derived from the cross between the pair of NILS NIL7-2A (nod) × NIL7-2B (non-nod) revealed a co-localization between CaNSP2 and Rn1 gene. These data implicate the CaNSP2 gene as a candidate for identity to Rn1, and suggest that it could act in the nodulation signaling transduction pathway similarly to that in other legumes species.

  6. Development of local complexity metrics to quantify the effect of anatomical noise on detectability of lung nodules in chest CT imaging

    NASA Astrophysics Data System (ADS)

    Solomon, Justin; Rubin, Geoffrey; Smith, Taylor; Harrawood, Brian; Choudhury, Kingshuk Roy; Samei, Ehsan

    2017-03-01

    The purpose of this study was to develop metrics of local anatomical complexity and compare them with detectability of lung nodules in CT. Data were drawn retrospectively from a published perception experiment in which detectability was assessed in cases enriched with virtual nodules (13 radiologists x 157 total nodules = 2041 responses). A local anatomical complexity metric called the distractor index was developed, defined as the Gaussian weighted proportion (i.e., average) of distracting local voxels (50 voxels in-plane, 5 slices). A distracting voxel was classified by thresholding image data that had been selectively filtered to enhance nodule-like features. The distractor index was measured for each nodule location in the nodule-free images. The local pixel standard deviation (STD) was also measured for each nodule. Other confounding factors of search fraction (proportion of lung voxels to total voxels in the given slice) and peripheral distance (defined as the 3D distance of the nodule from the trachea bifurcation) were measured. A generalized linear mixed-effects statistical model (no interaction terms, probit link function, random reader term) was fit to the data to determine the influence of each metric on detectability. In order of decreasing effect size: distractor index, STD, and search fraction all significantly affected detectability (P < 0.001). Distance to the trachea did not have a significant effect (P < 0.05). These data demonstrate that local lung complexity degrades detection of lung nodules and the distractor index could serve as a good surrogate metric to quantify anatomical complexity.

  7. Lung Nodules: Overview

    MedlinePlus

    ... Research & Science Education & Training Home Conditions Lung Nodules Lung Nodules Make an Appointment Find a Doctor Ask ... Kern, MD (June 01, 2016) What is a lung nodule? A lung nodule is also called a ...

  8. Lung Nodules: Overview

    MedlinePlus

    ... Research & Science Education & Training Home Conditions Lung Nodules Lung Nodules Make an Appointment Find a Doctor Ask ... Kern, MD (June 01, 2016) What is a lung nodule? A lung nodule is also called a ...

  9. Lentils: the Forgotten Legumes

    MedlinePlus

    ... page: https://medlineplus.gov/news/fullstory_166192.html Lentils: The Forgotten Legumes Beans' little cousins pack in ... 2, 2017 FRIDAY, June 2, 2017 (HealthDay News) -- Lentils may be the least well known members of ...

  10. Potential Maternal Effects of Elevated Atmospheric CO2 on Development and Disease Severity in a Mediterranean Legume

    PubMed Central

    Grünzweig, José M.

    2011-01-01

    Global change can greatly affect plant populations both directly by influencing growing conditions and indirectly by maternal effects on development of offspring. More information is needed on transgenerational effects of global change on plants and their interactions with pathogens. The current study assessed potential maternal effects of atmospheric CO2 enrichment on performance and disease susceptibility of first-generation offspring of the Mediterranean legume Onobrychis crista-galli. Mother plants were grown at three CO2 concentrations, and the study focused on their offspring that were raised under common ambient climate and CO2. In addition, progeny were exposed to natural infection by the fungal pathogen powdery mildew. In one out of 3 years, offspring of high-CO2 treatments (440 and 600 ppm) had lower shoot biomass and reproductive output than offspring of low-CO2 treatment (280 ppm). Disease severity in a heavy-infection year was higher in high-CO2 than in low-CO2 offspring. However, some of the findings on maternal effects changed when the population was divided into two functionally diverging plant types distinguishable by flower color (pink, Type P; white, Type W). Disease severity in a heavy-infection year was higher in high-CO2 than in low-CO2 progeny in the more disease-resistant (Type P), but not in the more susceptible plant type (Type W). In a low-infection year, maternal CO2 treatments did not differ in disease severity. Mother plants of Type P exposed to low CO2 produced larger seeds than all other combinations of CO2 and plant type, which might contribute to higher offspring performance. This study showed that elevated CO2 potentially exerts environmental maternal effects on performance of progeny and, notably, also on their susceptibility to natural infection by a pathogen. Maternal effects of global change might differently affect functionally divergent plant types, which could impact population fitness and alter plant communities

  11. Rhizobium-legume symbiosis shares an exocytotic pathway required for arbuscule formation.

    PubMed

    Ivanov, Sergey; Fedorova, Elena E; Limpens, Erik; De Mita, Stephane; Genre, Andrea; Bonfante, Paola; Bisseling, Ton

    2012-05-22

    Endosymbiotic interactions are characterized by the formation of specialized membrane compartments, by the host in which the microbes are hosted, in an intracellular manner. Two well-studied examples, which are of major agricultural and ecological importance, are the widespread arbuscular mycorrhizal symbiosis and the Rhizobium-legume symbiosis. In both symbioses, the specialized host membrane that surrounds the microbes forms a symbiotic interface, which facilitates the exchange of, for example, nutrients in a controlled manner and, therefore, forms the heart of endosymbiosis. Despite their key importance, the molecular and cellular mechanisms underlying the formation of these membrane interfaces are largely unknown. Recent studies strongly suggest that the Rhizobium-legume symbiosis coopted a signaling pathway, including receptor, from the more ancient arbuscular mycorrhizal symbiosis to form a symbiotic interface. Here, we show that two highly homologous exocytotic vesicle-associated membrane proteins (VAMPs) are required for formation of the symbiotic membrane interface in both interactions. Silencing of these Medicago VAMP72 genes has a minor effect on nonsymbiotic plant development and nodule formation. However, it blocks symbiosome as well as arbuscule formation, whereas root colonization by the microbes is not affected. Identification of these VAMP72s as common symbiotic regulators in exocytotic vesicle trafficking suggests that the ancient exocytotic pathway forming the periarbuscular membrane compartment has also been coopted in the Rhizobium-legume symbiosis.

  12. Ectopic expression of miR156 represses nodulation and causes morphological and developmental changes in Lotus japonicus.

    PubMed

    Wang, Ying; Wang, Zhishuo; Amyot, Lisa; Tian, Lining; Xu, Ziqin; Gruber, Margaret Y; Hannoufa, Abdelali

    2015-04-01

    The effects of microRNA156 overexpression on general plant architecture, branching, flowering time and nodulation were investigated in the model legume, Lotus japonicus. We cloned an miR156 homolog, LjmiR156a, from L. japonicus, and investigated its SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes and its biological function at enhancing vegetative biomass yield, extending flowering time, and its impact on nodulation. Thirteen potential targets for LjmiR156 were identified in vitro and their expression profiles were determined in aerial and underground parts of mature plants, including genes coding for eight SPLs, one WD-40, one RNA-directed DNA polymerase, two transport proteins, and one histidine-phosphotransfer protein. Two SPL and one WD-40 cleavage targets for LjmiR156-TC70253, AU089191, and TC57859-were identified. Transgenic plants with ectopic expression of LjmiR156a showed enhanced branching, dramatically delayed flowering, underdeveloped roots, and reduced nodulation. We also examined the transcript levels of key genes involved in nodule organogenesis and infection thread formation to determine the role of miR156 in regulating symbiosis. Overexpression of LjmiR156a led to repression of several nodulation genes during the early stages of root development such as three ENOD genes, SymPK, POLLUX, CYCLOPS, Cerberus, and Nsp1, and the stimulation of NFR1. Our results show that miR156 regulates vegetative biomass yield, flowering time and nodulation by silencing downstream target SPLs and other genes, suggesting that the miR156 regulatory network could be modified in forage legumes (such as alfalfa and trefoils) and in leafy vegetables (like lettuce and spinach) to positively impact economically valuable crop species.

  13. MtZR1, a PRAF protein, is involved in the development of roots and symbiotic root nodules in Medicago truncatula.

    PubMed

    Hopkins, Julie; Pierre, Olivier; Kazmierczak, Théophile; Gruber, Véronique; Frugier, Florian; Clement, Mathilde; Frendo, Pierre; Herouart, Didier; Boncompagni, Eric

    2014-03-01

    PRAF proteins are present in all plants, but their functions remain unclear. We investigated the role of one member of the PRAF family, MtZR1, on the development of roots and nitrogen-fixing nodules in Medicago truncatula. We found that MtZR1 was expressed in all M. truncatula organs. Spatiotemporal analysis showed that MtZR1 expression in M. truncatula roots was mostly limited to the root meristem and the vascular bundles of mature nodules. MtZR1 expression in root nodules was down-regulated in response to various abiotic stresses known to affect nitrogen fixation efficiency. The down-regulation of MtZR1 expression by RNA interference in transgenic roots decreased root growth and impaired nodule development and function. MtZR1 overexpression resulted in longer roots and significant changes to nodule development. Our data thus indicate that MtZR1 is involved in the development of roots and nodules. To our knowledge, this work provides the first in vivo experimental evidence of a biological role for a typical PRAF protein in plants.

  14. Thiol synthetases of legumes: immunogold localization and differential gene regulation by phytohormones.

    PubMed

    Clemente, Maria R; Bustos-Sanmamed, Pilar; Loscos, Jorge; James, Euan K; Pérez-Rontomé, Carmen; Navascués, Joaquín; Gay, Marina; Becana, Manuel

    2012-06-01

    In plants and other organisms, glutathione (GSH) biosynthesis is catalysed sequentially by γ-glutamylcysteine synthetase (γECS) and glutathione synthetase (GSHS). In legumes, homoglutathione (hGSH) can replace GSH and is synthesized by γECS and a specific homoglutathione synthetase (hGSHS). The subcellular localization of the enzymes was examined by electron microscopy in several legumes and gene expression was analysed in Lotus japonicus plants treated for 1-48 h with 50 μM of hormones. Immunogold localization studies revealed that γECS is confined to chloroplasts and plastids, whereas hGSHS is also in the cytosol. Addition of hormones caused differential expression of thiol synthetases in roots. After 24-48 h, abscisic and salicylic acids downregulated GSHS whereas jasmonic acid upregulated it. Cytokinins and polyamines activated GSHS but not γECS or hGSHS. Jasmonic acid elicited a coordinated response of the three genes and auxin induced both hGSHS expression and activity. Results show that the thiol biosynthetic pathway is compartmentalized in legumes. Moreover, the similar response profiles of the GSH and hGSH contents in roots of non-nodulated and nodulated plants to the various hormonal treatments indicate that thiol homeostasis is independent of the nitrogen source of the plants. The differential regulation of the three mRNA levels, hGSHS activity, and thiol contents by hormones indicates a fine control of thiol biosynthesis at multiple levels and strongly suggests that GSH and hGSH play distinct roles in plant development and stress responses.

  15. Thiol synthetases of legumes: immunogold localization and differential gene regulation by phytohormones

    PubMed Central

    Clemente, Maria R.; Bustos-Sanmamed, Pilar; Loscos, Jorge; James, Euan K.; Pérez-Rontomé, Carmen; Navascués, Joaquín; Gay, Marina; Becana, Manuel

    2012-01-01

    In plants and other organisms, glutathione (GSH) biosynthesis is catalysed sequentially by γ-glutamylcysteine synthetase (γECS) and glutathione synthetase (GSHS). In legumes, homoglutathione (hGSH) can replace GSH and is synthesized by γECS and a specific homoglutathione synthetase (hGSHS). The subcellular localization of the enzymes was examined by electron microscopy in several legumes and gene expression was analysed in Lotus japonicus plants treated for 1–48 h with 50 μM of hormones. Immunogold localization studies revealed that γECS is confined to chloroplasts and plastids, whereas hGSHS is also in the cytosol. Addition of hormones caused differential expression of thiol synthetases in roots. After 24–48 h, abscisic and salicylic acids downregulated GSHS whereas jasmonic acid upregulated it. Cytokinins and polyamines activated GSHS but not γECS or hGSHS. Jasmonic acid elicited a coordinated response of the three genes and auxin induced both hGSHS expression and activity. Results show that the thiol biosynthetic pathway is compartmentalized in legumes. Moreover, the similar response profiles of the GSH and hGSH contents in roots of non-nodulated and nodulated plants to the various hormonal treatments indicate that thiol homeostasis is independent of the nitrogen source of the plants. The differential regulation of the three mRNA levels, hGSHS activity, and thiol contents by hormones indicates a fine control of thiol biosynthesis at multiple levels and strongly suggests that GSH and hGSH play distinct roles in plant development and stress responses. PMID:22442424

  16. Insights into post-transcriptional regulation during legume-rhizobia symbiosis.

    PubMed

    Reynoso, Mauricio Alberto; Blanco, Flavio Antonio; Zanetti, María Eugenia

    2013-02-01

    During the past ten years, changes in the transcriptome have been assessed at different stages of the legume-rhizobia association by the use of DNA microarrays and, more recently, by RNA sequencing technologies. These studies allowed the identification of hundred or thousand of genes whose steady-state mRNA levels increase or decrease upon bacterial infection or in nodules as compared with uninfected roots. However, transcriptome based-approaches do not distinguish between mRNAs that are being actively translated, stored as messenger ribonucleoproteins (mRNPs) or targeted for degradation. Despite that the increase in steady-state levels of an mRNA does not necessarily correlate with an increase in abundance or activity of the encoded protein, this information has been commonly used to select genes that are candidates to play a role during nodule organogenesis or bacterial infection. Such criterion does not take into account the post-transcriptional mechanisms that contribute to the regulation of gene expression. One of such mechanisms, which has significant impact on gene expression, is the selective recruitment of mRNAs to the translational machinery.  Here, we review the post-transcriptional mechanisms that contribute to the regulation of gene expression in the context of the ecological and agronomical important symbiotic interaction established between roots of legumes and the nitrogen fixing bacteria collectively known as rhizobia. In addition, we discuss how the development of new technologies that allow the assessment of these regulatory layers would help to understand the genetic network governing legume rhizobia symbiosis.

  17. Genome Sequence of Micromonospora lupini Lupac 08, Isolated from Root Nodules of Lupinus angustifolius

    PubMed Central

    Alonso-Vega, Pablo; Normand, Philippe; Bacigalupe, Rodrigo; Pujic, Petar; Lajus, Aurelie; Vallenet, David; Carro, Lorena; Coll, Pedro

    2012-01-01

    Micromonospora strains have been isolated from diverse niches, including soil, water, and marine sediments and root nodules of diverse symbiotic plants. In this work, we report the genome sequence of Micromonospora lupini Lupac 08 isolated from root nodules of the wild legume Lupinus angustifolious. PMID:22815450

  18. Effect of mercury on seedling growth, nodulation and ultrastructural deformation of Vigna radiata (L) Wilczek.

    PubMed

    Mondal, Naba Kumar; Das, Chittaranjan; Datta, Jayanta Kumar

    2015-05-01

    Heavy metals are major environmental pollutant when they present in high concentration in soil and have toxic effects on growth, nodulation and nitrogen fixation of legumes and development of plants. Mercury stress triggers disturbances in cellular structure, and metabolismn is poorly understood. The response of seedling growth and nodulation of Vigna radiata (L) Wilczek to different concentrations (0.1, 0.5, 1.0 and 1.5 ppm) of mercury (Hg) salt solutions were studied. Morphological parameters like root and shoot length, dry weight, nodule number, total leaf area and biochemical constituents (chlorophyll, malondialdehyde and leghaemoglobin) of bean plants were recorded at an interval of 30 days. The successive growth deformaties in seedlings and nodules were recorded at lower concentration (0.1 ppm), but marginal (0.5 ppm) and higher (1.0 ppm) level of Hg salt solution showed significant suppression. The maximum level of Hg concentration (1.5 ppm) shows high level of tolerance index without any nodule. The control treatment shows maximum level of leghaemoglobin (0.219 mM) and all other morpho-physiological and bio-chemical properties of roots and shoots excepting tolerance index (0.00) and chlorophyll 'a' (7.52 mg g(-1) FW). Mercury accumulation pattern follows the sequences: leaf > nodule > root ≈ shoot at lower level of Hg (0.1 and 0.5 ppm). However, higher level of Hg (1.0 and 1.5 ppm) showed shoot > root > leaf > nodule. The scanning electron microscopy (SEM) study of root also highlights the deleterious effect of Hg salt at higher concentration.

  19. Specific subunits of heterotrimeric G proteins play important roles during nodulation in soybean.

    PubMed

    Choudhury, Swarup Roy; Pandey, Sona

    2013-05-01

    Heterotrimeric G proteins comprising Gα, Gβ, and Gγ subunits regulate many fundamental growth and development processes in all eukaryotes. Plants possess a relatively limited number of G-protein components compared with mammalian systems, and their detailed functional characterization has been performed mostly in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa). However, the presence of single Gα and Gβ proteins in both these species has significantly undermined the complexity and specificity of response regulation in plant G-protein signaling. There is ample pharmacological evidence for the role of G proteins in regulation of legume-specific processes such as nodulation, but the lack of genetic data from a leguminous species has restricted its direct assessment. Our recent identification and characterization of an elaborate G-protein family in soybean (Glycine max) and the availability of appropriate molecular-genetic resources have allowed us to directly evaluate the role of G-protein subunits during nodulation. We demonstrate that all G-protein genes are expressed in nodules and exhibit significant changes in their expression in response to Bradyrhizobium japonicum infection and in representative supernodulating and nonnodulating soybean mutants. RNA interference suppression and overexpression of specific G-protein components results in lower and higher nodule numbers, respectively, validating their roles as positive regulators of nodule formation. Our data further show preferential usage of distinct G-protein subunits in the presence of an additional signal during nodulation. Interestingly, the Gα proteins directly interact with the soybean nodulation factor receptors NFR1α and NFR1β, suggesting that the plant G proteins may couple with receptors other than the canonical heptahelical receptors common in metazoans to modulate signaling.

  20. Diversity and symbiotic effectiveness of beta-rhizobia isolated from sub-tropical legumes of a Brazilian Araucaria Forest.

    PubMed

    Lammel, Daniel R; Cruz, Leonardo M; Carrer, Helaine; Cardoso, Elke J B N

    2013-12-01

    While the occurrence of Betaproteobacteria occupying the nodules of tropical legumes has been shown, little is known about subtropical areas. Araucaria Forest is a subtropical endangered ecosystem, and a better understanding of the legume-rhizobial symbionts may allow their use in land reclamation. The 16S rRNA gene of bacteria isolated from nine leguminous species was sequenced and their nodulation tested in Mimosa scabrella and Phaseolus vulgaris. 196 isolates were identified as eight genotypes: Pantoea, Pseudomonas, Bradyrhizobium sp1-2, Rhizobium, and Burkholderia sp1-3. The majority of the isolates from native plants (87 %) were taxonomically related to β-rhizobia, namely Burkholderia, however the legumes Galactia crassifolia and Collea speciosa were nodulated by both α and β-rhizobia, and Acacia dealbata, an exotic plant, only by α-rhizobia. The nifH genes of some isolates were sequenced and N-fixing potential shown by the acetylene reduction test. Most of the isolates nodulated the test plants, some were effective in M. scabrella, but all presented low efficiency in the exotic promiscuous legume P. vulgaris. Pantoea and Pseudomonas did not nodulate and probably are endophytic bacteria. The presented data shows diversity of α, β and γ-Proteobacteria in nodules of subtropical legumes, and suggests host specificity with β-rhizobia. Potential isolates were found for M. scabrella, indicating that a high N-fixing strain may be further inoculated in plants for use in reforestation.

  1. Flower development of Goniorrhachis marginata reveals new insights into the evolution of the florally diverse detarioid legumes.

    PubMed

    Prenner, Gerhard; Cardoso, Domingos

    2017-02-01

    The study of floral morphology and ontogeny and the re-investigation of existing data help to uncover potential synapomorphic characters and foster our understanding of phylogenetic relationships that rely primarily on molecular analyses. Goniorrhachis marginata is a monotypic caesalpinioid legume (Leguminosae) that shows some interesting floral features, such as a long hypanthium and regular Rosaceae-like flowers. We studied the ontogeny and morphology of the flowers in detail and present our results in a broad phylogenetic context. Flower buds were collected in the field, fixed in 70 % ethanol and investigated using scanning electron microscopy. Older buds in spirit were carefully opened to investigate the direction of style bending. Characters of the style from 131 taxa from the main legume lineages were analysed and mapped on a Bayesian molecular phylogeny. The tetramerous calyx is the result of complete loss of one sepal. The formation of the radially symmetrical corolla starts in a typical caesalpinioid pattern with the adaxial petal innermost (ascending aestivation). The young style bends in the abaxial direction, which is a character found exclusively in all studied detarioid legumes and therefore a newly described synapomorphy for the clade. We show that investigation of unstudied taxa and reinvestigation of published data can uncover new, previously overlooked and important characters. Curvature of the style can be detected in young buds with a hand lens and therefore is an important character for field botanists. Our study reveals the importance of including poorly studied and/or phylogenetically enigmatic taxa in molecular phylogenies and in detailed morphological and ontogenetic analyses. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  2. Unlocking the potential of orphan legumes.

    PubMed

    Cullis, Christopher; Kunert, Karl J

    2016-12-21

    Orphan, or underutilized, legumes are domesticated legumes with useful properties, but with less importance than major world crops due to use and supply constraints. However, they play a significant role in many developing countries, providing food security and nutrition to consumers, as well as income to resource-poor farmers. They have been largely neglected by both researchers and industry due to their limited economic importance in the global market. Orphan legumes are better adapted than the major legume crops to extreme soil and climatic conditions, with high tolerance to abiotic environmental stresses such as drought. As a stress response they can also produce compounds with pharmaceutical value. Orphan legumes are therefore a likely source of important traits for introduction into major crops to aid in combating the stresses associated with global climate change. Modern large-scale genomics techniques are now being applied to many of these previously understudied crops, with the first successes reported in the genomics area. However, greater investment of resources and manpower are necessary if the potential of orphan legumes is to be unlocked and applied in the future.

  3. Involvement of the Azorhizobial Chromosome Partition Gene (parA) in the Onset of Bacteroid Differentiation during Sesbania rostrata Stem Nodule Development ▿ †

    PubMed Central

    Liu, Chi-Te; Lee, Kyung-Bum; Wang, Yu-Sheng; Peng, Min-Hua; Lee, Kung-Ta; Suzuki, Shino; Suzuki, Tadahiro; Oyaizu, Hiroshi

    2011-01-01

    A parA gene in-frame deletion mutant of Azorhizobium caulinodans ORS571 (ORS571-ΔparA) was constructed to evaluate the roles of the chromosome-partitioning gene on various bacterial traits and on the development of stem-positioned nodules. The ΔparA mutant showed a pleiomorphic cell shape phenotype and was polyploid, with differences in nucleoid sizes due to dramatic defects in chromosome partitioning. Upon inoculation of the ΔparA mutant onto the stem of Sesbania rostrata, three types of immature nodule-like structures with impaired nitrogen-fixing activity were generated. Most showed signs of bacteroid early senescence. Moreover, the ΔparA cells within the nodule-like structures exhibited multiple developmental-stage phenotypes. Since the bacA gene has been considered an indicator for bacteroid formation, we applied the expression pattern of bacA as a nodule maturity index in this study. Our data indicate that the bacA gene expression is parA dependent in symbiosis. The presence of the parA gene transcript was inversely correlated with the maturity of nodule; the transcript was switched off in fully mature bacteroids. In summary, our experimental evidence demonstrates that the parA gene not only plays crucial roles in cellular development when the microbe is free-living but also negatively regulates bacteroid formation in S. rostrata stem nodules. PMID:21571889

  4. Nonnodulating Bradyrhizobium spp. Modulate the Benefits of Legume-Rhizobium Mutualism

    PubMed Central

    Gano-Cohen, Kelsey A.; Stokes, Peter J.; Blanton, Mia A.; Wendlandt, Camille E.; Hollowell, Amanda C.; Regus, John U.; Kim, Deborah; Patel, Seema; Pahua, Victor J.

    2016-01-01

    ABSTRACT Rhizobia are best known for nodulating legume roots and fixing atmospheric nitrogen for the host in exchange for photosynthates. However, the majority of the diverse strains of rhizobia do not form nodules on legumes, often because they lack key loci that are needed to induce nodulation. Nonnodulating rhizobia are robust heterotrophs that can persist in bulk soil, thrive in the rhizosphere, or colonize roots as endophytes, but their role in the legume-rhizobium mutualism remains unclear. Here, we investigated the effects of nonnodulating strains on the native Acmispon-Bradyrhizobium mutualism. To examine the effects on both host performance and symbiont fitness, we performed clonal inoculations of diverse nonnodulating Bradyrhizobium strains on Acmispon strigosus hosts and also coinoculated hosts with mixtures of sympatric nodulating and nonnodulating strains. In isolation, nonnodulating Bradyrhizobium strains did not affect plant performance. In most cases, coinoculation of nodulating and nonnodulating strains reduced host performance compared to that of hosts inoculated with only a symbiotic strain. However, coinoculation increased host performance only under one extreme experimental treatment. Nearly all estimates of nodulating strain fitness were reduced in the presence of nonnodulating strains. We discovered that nonnodulating strains were consistently capable of coinfecting legume nodules in the presence of nodulating strains but that the fitness effects of coinfection for hosts and symbionts were negligible. Our data suggest that nonnodulating strains most often attenuate the Acmispon-Bradyrhizobium mutualism and that this occurs via competitive interactions at the root-soil interface as opposed to in planta. IMPORTANCE Rhizobia are soil bacteria best known for their capacity to form root nodules on legume plants and enhance plant growth through nitrogen fixation. Yet, most rhizobia in soil do not have this capacity, and their effects on this

  5. Nonnodulating Bradyrhizobium spp. Modulate the Benefits of Legume-Rhizobium Mutualism.

    PubMed

    Gano-Cohen, Kelsey A; Stokes, Peter J; Blanton, Mia A; Wendlandt, Camille E; Hollowell, Amanda C; Regus, John U; Kim, Deborah; Patel, Seema; Pahua, Victor J; Sachs, Joel L

    2016-09-01

    Rhizobia are best known for nodulating legume roots and fixing atmospheric nitrogen for the host in exchange for photosynthates. However, the majority of the diverse strains of rhizobia do not form nodules on legumes, often because they lack key loci that are needed to induce nodulation. Nonnodulating rhizobia are robust heterotrophs that can persist in bulk soil, thrive in the rhizosphere, or colonize roots as endophytes, but their role in the legume-rhizobium mutualism remains unclear. Here, we investigated the effects of nonnodulating strains on the native Acmispon-Bradyrhizobium mutualism. To examine the effects on both host performance and symbiont fitness, we performed clonal inoculations of diverse nonnodulating Bradyrhizobium strains on Acmispon strigosus hosts and also coinoculated hosts with mixtures of sympatric nodulating and nonnodulating strains. In isolation, nonnodulating Bradyrhizobium strains did not affect plant performance. In most cases, coinoculation of nodulating and nonnodulating strains reduced host performance compared to that of hosts inoculated with only a symbiotic strain. However, coinoculation increased host performance only under one extreme experimental treatment. Nearly all estimates of nodulating strain fitness were reduced in the presence of nonnodulating strains. We discovered that nonnodulating strains were consistently capable of coinfecting legume nodules in the presence of nodulating strains but that the fitness effects of coinfection for hosts and symbionts were negligible. Our data suggest that nonnodulating strains most often attenuate the Acmispon-Bradyrhizobium mutualism and that this occurs via competitive interactions at the root-soil interface as opposed to in planta Rhizobia are soil bacteria best known for their capacity to form root nodules on legume plants and enhance plant growth through nitrogen fixation. Yet, most rhizobia in soil do not have this capacity, and their effects on this symbiosis are poorly

  6. Study of phenanthrene utilizing bacterial consortia associated with cowpea (Vigna unguiculata) root nodules.

    PubMed

    Sun, Ran; Crowley, David E; Wei, Gehong

    2015-02-01

    Many legumes have been selected as model plants to degrade organic contaminants with their special associated rhizosphere microbes in soil. However, the function of root nodules during microbe-assisted phytoremediation is not clear. A pot study was conducted to examine phenanthrene (PHE) utilizing bacteria associated with root nodules and the effects of cowpea root nodules on phytoremediation in two different types of soils (freshly contaminated soil and aged contaminated soil). Cowpea nodules in freshly-contaminated soil showed less damage in comparison to the aged-contaminated soil, both morphologically and ultra-structurally by scanning electron microscopy. The study of polycyclic aromatic hydrocarbon (PAH) attenuation conducted by high performance liquid chromatography revealed that more PAH was eliminated from liquid culture around nodulated roots than nodule-free roots. PAH sublimation and denaturation gradient gel electrophoresis were applied to analyze the capability and diversity of PAH degrading bacteria from the following four parts of rhizo-microzone: bulk soil, root surface, nodule surface and nodule inside. The results indicated that the surface and inside of cowpea root nodules were colonized with bacterial consortia that utilized PHE. Our results demonstrated that root nodules not only fixed nitrogen, but also enriched PAH-utilizing microorganisms both inside and outside of the nodules. Legume nodules may have biotechnological values for PAH degradation.

  7. Transport and metabolism in legume-rhizobia symbioses.

    PubMed

    Udvardi, Michael; Poole, Philip S

    2013-01-01

    Symbiotic nitrogen fixation by rhizobia in legume root nodules injects approximately 40 million tonnes of nitrogen into agricultural systems each year. In exchange for reduced nitrogen from the bacteria, the plant provides rhizobia with reduced carbon and all the essential nutrients required for bacterial metabolism. Symbiotic nitrogen fixation requires exquisite integration of plant and bacterial metabolism. Central to this integration are transporters of both the plant and the rhizobia, which transfer elements and compounds across various plant membranes and the two bacterial membranes. Here we review current knowledge of legume and rhizobial transport and metabolism as they relate to symbiotic nitrogen fixation. Although all legume-rhizobia symbioses have many metabolic features in common, there are also interesting differences between them, which show that evolution has solved metabolic problems in different ways to achieve effective symbiosis in different systems.

  8. Selection and characterization of coal mine autochthonous rhizobia for the inoculation of herbaceous legumes.

    PubMed

    Hernández, Anabel González; de Moura, Ginaini Doin; Binati, Renato Leal; Nascimento, Francisco Xavier Inês; Londoño, Diana Morales; Mamede, Ana Carolina Peixoto; da Silva, Emanuela Pille; de Armas, Rafael Dutra; Giachini, Admir José; Rossi, Márcio José; Soares, Cláudio Roberto Fonsêca Sousa

    2017-04-05

    Coal open pit mining in the South of Santa Catarina state (Brazil) was inappropriately developed, affecting approximately 6.700 ha. Re-vegetation is an alternative for the recovery of these areas. Furthermore, the use of herbaceous legumes inoculated with nitrogen fixing bacteria is motivated due to the difficulty implementing a vegetation cover in these areas, mainly due to low nutrient availability. Therefore, the aim of this work was to evaluate, among 16 autochthonous rhizobia isolated from the coal mining areas, those with the greatest potential to increase growth of the herbaceous legumes Vicia sativa and Calopogonium mucunoides. Tests were conducted in greenhouse containing 17 inoculation treatments (16 autochthonous rhizobia + Brazilian recommended strain for each plant species), plus two treatments without inoculation (with and without mineral nitrogen). After 60 days, nodulation, growth, N uptake, and symbiotic efficiency were evaluated. Isolates characterization was assessed by the production of indole acetic acid, ACC deaminase, siderophores, and inorganic phosphate solubilization. The classification of the isolates was performed by 16 S rDNA gene sequencing. Only isolates UFSC-M4 and UFSC-M8 were able to nodulate C. mucunoides. Among rhizobia capable of nodulating V. sativa, only UFSC-M8 was considered efficient. It was found the presence of more than one growth-promoting attributes in the same organism, and isolate UFSC-M8 presented all of them. Isolates were classified as belonging to Rhizobium, Burkholderia and Curtobacterium. The results suggest the inoculation of Vicia sativa with strain UFSC-M8, classified as Rhizobium sp., as a promising alternative for the revegetation of coal mining degraded areas.

  9. Estimating variability in grain legume yields across Europe and the Americas

    NASA Astrophysics Data System (ADS)

    Cernay, Charles; Ben-Ari, Tamara; Pelzer, Elise; Meynard, Jean-Marc; Makowski, David

    2015-06-01

    Grain legume production in Europe has recently come under scrutiny. Although legume crops are often promoted to provide environmental services, European farmers tend to turn to non-legume crops. It is assumed that high variability in legume yields explains this aversion, but so far this hypothesis has not been tested. Here, we estimate the variability of major grain legume and non-legume yields in Europe and the Americas from yield time series over 1961-2013. Results show that grain legume yields are significantly more variable than non-legume yields in Europe. These differences are smaller in the Americas. Our results are robust at the level of the statistical methods. In all regions, crops with high yield variability are allocated to less than 1% of cultivated areas. Although the expansion of grain legumes in Europe may be hindered by high yield variability, some species display risk levels compatible with the development of specialized supply chains.

  10. Estimating variability in grain legume yields across Europe and the Americas.

    PubMed

    Cernay, Charles; Ben-Ari, Tamara; Pelzer, Elise; Meynard, Jean-Marc; Makowski, David

    2015-06-08

    Grain legume production in Europe has recently come under scrutiny. Although legume crops are often promoted to provide environmental services, European farmers tend to turn to non-legume crops. It is assumed that high variability in legume yields explains this aversion, but so far this hypothesis has not been tested. Here, we estimate the variability of major grain legume and non-legume yields in Europe and the Americas from yield time series over 1961-2013. Results show that grain legume yields are significantly more variable than non-legume yields in Europe. These differences are smaller in the Americas. Our results are robust at the level of the statistical methods. In all regions, crops with high yield variability are allocated to less than 1% of cultivated areas. Although the expansion of grain legumes in Europe may be hindered by high yield variability, some species display risk levels compatible with the development of specialized supply chains.

  11. Estimating variability in grain legume yields across Europe and the Americas

    PubMed Central

    Cernay, Charles; Ben-Ari, Tamara; Pelzer, Elise; Meynard, Jean-Marc; Makowski, David

    2015-01-01

    Grain legume production in Europe has recently come under scrutiny. Although legume crops are often promoted to provide environmental services, European farmers tend to turn to non-legume crops. It is assumed that high variability in legume yields explains this aversion, but so far this hypothesis has not been tested. Here, we estimate the variability of major grain legume and non-legume yields in Europe and the Americas from yield time series over 1961–2013. Results show that grain legume yields are significantly more variable than non-legume yields in Europe. These differences are smaller in the Americas. Our results are robust at the level of the statistical methods. In all regions, crops with high yield variability are allocated to less than 1% of cultivated areas. Although the expansion of grain legumes in Europe may be hindered by high yield variability, some species display risk levels compatible with the development of specialized supply chains. PMID:26054055

  12. Genetic control of inflorescence architecture in legumes

    PubMed Central

    Benlloch, Reyes; Berbel, Ana; Ali, Latifeh; Gohari, Gholamreza; Millán, Teresa; Madueño, Francisco

    2015-01-01

    The architecture of the inflorescence, the shoot system that bears the flowers, is a main component of the huge diversity of forms found in flowering plants. Inflorescence architecture has also a strong impact on the production of fruits and seeds, and on crop management, two highly relevant agronomical traits. Elucidating the genetic networks that control inflorescence development, and how they vary between different species, is essential to understanding the evolution of plant form and to being able to breed key architectural traits in crop species. Inflorescence architecture depends on the identity and activity of the meristems in the inflorescence apex, which determines when flowers are formed, how many are produced and their relative position in the inflorescence axis. Arabidopsis thaliana, where the genetic control of inflorescence development is best known, has a simple inflorescence, where the primary inflorescence meristem directly produces the flowers, which are thus borne in the main inflorescence axis. In contrast, legumes represent a more complex inflorescence type, the compound inflorescence, where flowers are not directly borne in the main inflorescence axis but, instead, they are formed by secondary or higher order inflorescence meristems. Studies in model legumes such as pea (Pisum sativum) or Medicago truncatula have led to a rather good knowledge of the genetic control of the development of the legume compound inflorescence. In addition, the increasing availability of genetic and genomic tools for legumes is allowing to rapidly extending this knowledge to other grain legume crops. This review aims to describe the current knowledge of the genetic network controlling inflorescence development in legumes. It also discusses how the combination of this knowledge with the use of emerging genomic tools and resources may allow rapid advances in the breeding of grain legume crops. PMID:26257753

  13. 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase1 Interacts with NORK and Is Crucial for Nodulation in Medicago truncatula

    PubMed Central

    Kevei, Zoltán; Lougnon, Géraldine; Mergaert, Peter; Horváth, Gábor V.; Kereszt, Attila; Jayaraman, Dhileepkumar; Zaman, Najia; Marcel, Fabian; Regulski, Krzysztof; Kiss, György B.; Kondorosi, Adam; Endre, Gabriella; Kondorosi, Eva; Ané, Jean-Michel

    2007-01-01

    NORK in legumes encodes a receptor-like kinase that is required for Nod factor signaling and root nodule development. Using Medicago truncatula NORK as bait in a yeast two-hybrid assay, we identified 3-hydroxy-3-methylglutaryl CoA reductase 1 (Mt HMGR1) as a NORK interacting partner. HMGR1 belongs to a multigene family in M. truncatula, and different HMGR isoforms are key enzymes in the mevalonate biosynthetic pathway leading to the production of a diverse array of isoprenoid compounds. Testing other HMGR members revealed a specific interaction between NORK and HMGR1. Mutagenesis and deletion analysis showed that this interaction requires the cytosolic active kinase domain of NORK and the cytosolic catalytic domain of HMGR1. NORK homologs from Lotus japonicus and Sesbania rostrata also interacted with Mt HMGR1, but homologous nonsymbiotic kinases of M. truncatula did not. Pharmacological inhibition of HMGR activities decreased nodule number and delayed nodulation, supporting the importance of the mevalonate pathway in symbiotic development. Decreasing HMGR1 expression in M. truncatula transgenic roots by RNA interference led to a dramatic decrease in nodulation, confirming that HMGR1 is essential for nodule development. Recruitment of HMGR1 by NORK could be required for production of specific isoprenoid compounds, such as cytokinins, phytosteroids, or isoprenoid moieties involved in modification of signaling proteins. PMID:18156218

  14. Genetic Variability in Nodulation and Root Growth Affects Nitrogen Fixation and Accumulation in Pea

    PubMed Central

    Bourion, Virginie; Laguerre, Gisele; Depret, Geraldine; Voisin, Anne-Sophie; Salon, Christophe; Duc, Gerard

    2007-01-01

    Background and Aims Legume nitrogen is derived from two different sources, symbiotically fixed atmospheric N2 and soil N. The effect of genetic variability of root and nodule establishment on N acquisition and seed protein yield was investigated under field conditions in pea (Pisum sativum). In addition, these parameters were related to the variability in preference for rhizobial genotypes. Methods Five different spring pea lines (two hypernodulating mutants and three cultivars), previously identified in artificial conditions as contrasted for both root and nodule development, were characterized under field conditions. Root and nodule establishment was examined from the four-leaf stage up to the beginning of seed filling and was related to the patterns of shoot dry matter and nitrogen accumulation. The genetic structure of rhizobial populations associated with the pea lines was obtained by analysis of nodule samples. The fraction of nitrogen derived from symbiotic fixation was estimated at the beginning of seed filling and at physiological maturity, when seed protein content and yield were determined. Key Results The hypernodulating mutants established nodules earlier and maintained them longer than was the case for the three cultivars, whereas their root development and nitrogen accumulation were lower. The seed protein yield was higher in ‘Athos’ and ‘Austin’, the two cultivars with increased root development, consistent with their higher N absorption during seed filling. Conclusion The hypernodulating mutants did not accumulate more nitrogen, probably due to the C cost for nodulation being higher than for root development. Enhancing exogenous nitrogen supply at the end of the growth cycle, by increasing the potential for root N uptake from soil, seems a good option for improving pea seed filling. PMID:17670753

  15. Nodulation genes and type III secretion systems in rhizobia

    USDA-ARS?s Scientific Manuscript database

    For establishment of symbiosis, rhizobia and legumes have to communicate. Specific signaling starts with the release of flavonoids by the plant. All rhizobia encode at least one NodD protein, which responds to the presence of specific flavonoids by activation of nodulation genes. In Bradyrhizobium j...

  16. PREDICTIVE VALUE OF SOMATIC MUTATIONS FOR THE DEVELOPMENT OF MALIGNANCY IN THYROID NODULES BY CYTOPATHOLOGY.

    PubMed

    Halászlaki, Csaba; Tóbiás, Bálint; Balla, Bernadett; Kósa, János P; Horányi, János; Bölöny, Eszter; Nagy, Zsolt; Speer, Gábor; Járay, Balázs; Székely, Eszter; Istók, Roland; Székely, Tamás; Putz, Zsuzsanna; Dank, Magdolna; Lakatos, Péter; Takács, István

    2016-09-01

    The purpose of our prospective longitudinal study was to evaluate the predictive efficacy of genetic testing for malignancies in fine-needle aspiration biopsy samples that are cytologically benign at the time of biopsy. A total of 779 aspirated cytological samples collected from thyroid nodules of 626 patients were included in a 3-year follow-up study. Consecutive patients with cytologically benign thyroid nodules by the Bethesda System for Reporting Thyroid Cytopathology were enrolled in the study. At enrollment, somatic 1-point nucleotide polymorphisms of BRAF and RAS family genes were tested by melting-point analysis, while RET/PTC and PAX8/PPAR-gamma rearrangements were examined by real-time polymerase chain reaction. The genetic test was considered to be positive if a somatic mutation was found. Malignant cytopathologic diagnoses were confirmed by histopathology. In samples collected from 779 thyroid nodules, there were 39 BRAF, 33 RAS mutations, and 1 RET/PTC rearrangements found at the beginning of the study. No PAX8/PPAR-gamma rearrangement was identified. There were 52 malignant thyroid tumors removed during follow-up, out of which 24 contained a somatic mutation. The specificity of the presence of somatic mutations for malignancies was as high as 93.3%, and sensitivity was 46.2%. The negative predictive value of genetic testing reached 96.0%. Our results show that our set of genetic tests can predict the appearance of malignancy in benign thyroid nodules (at the beginning of follow-up) with high specificity and strong negative predictive value. BRAF = v-raf murine sarcoma viral oncogene homolog B1 FLUS = follicular lesion of undetermined significance FNAB = fine-needle aspiration biopsy FTC = follicular thyroid carcinoma HRAS = homologous to the oncogene from the Harvey rat sarcoma virus KRAS = homologous to the oncogene from the Kirsten rat sarcoma virus NRAS = first isolated from a human neuroblastoma/neuroblastoma RAS = viral oncogene homolog PAX8

  17. Cupriavidus necator isolates are able to fix nitrogen in symbiosis with different legume species.

    PubMed

    da Silva, Krisle; Florentino, Ligiane Aparecida; da Silva, Karina Barroso; de Brandt, Evie; Vandamme, Peter; de Souza Moreira, Fatima Maria

    2012-05-01

    The aim of the present study was to identify a collection of 35 Cupriavidus isolates at the species level and to examine their capacity to nodulate and fix N(2). These isolates were previously obtained from the root nodules of two promiscuous trap species, Phaseolus vulgaris and Leucaena leucocephala, inoculated with soil samples collected near Sesbania virgata plants growing in Minas Gerais (Brazil) pastures. Phenotypic and genotypic methods applied for this study were SDS-PAGE of whole-cell proteins, and 16S rRNA and gyrB gene sequencing. To confirm the ability to nodulate and fix N(2), the presence of the nodC and nifH genes was also determined, and an experiment was carried out with two representative isolates in order to authenticate them as legume nodule symbionts. All 35 isolates belonged to the betaproteobacterium Cupriavidus necator, they possessed the nodC and nifH genes, and two representative isolates were able to nodulate five different promiscuous legume species: Mimosa caesalpiniaefolia, L. leucocephala, Macroptilium atropurpureum, P. vulgaris and Vigna unguiculata. This is the first study to demonstrate that C. necator can nodulate legume species. Copyright © 2012 Elsevier GmbH. All rights reserved.

  18. Shaping bacterial symbiosis with legumes by experimental evolution.

    PubMed

    Marchetti, Marta; Jauneau, Alain; Capela, Delphine; Remigi, Philippe; Gris, Carine; Batut, Jacques; Masson-Boivin, Catherine

    2014-09-01

    Nitrogen-fixing symbionts of legumes have appeared after the emergence of legumes on earth, approximately 70 to 130 million years ago. Since then, symbiotic proficiency has spread to distant genera of α- and β-proteobacteria, via horizontal transfer of essential symbiotic genes and subsequent recipient genome remodeling under plant selection pressure. To tentatively replay rhizobium evolution in laboratory conditions, we previously transferred the symbiotic plasmid of the Mimosa symbiont Cupriavidus taiwanensis in the plant pathogen Ralstonia solanacearum, and selected spontaneous nodulating variants of the chimeric Ralstonia sp. using Mimosa pudica as a trap. Here, we pursued the evolution experiment by submitting two of the rhizobial drafts to serial ex planta-in planta (M. pudica) passages that may mimic alternating of saprophytic and symbiotic lives of rhizobia. Phenotyping 16 cycle-evolved clones showed strong and parallel evolution of several symbiotic traits (i.e., nodulation competitiveness, intracellular infection, and bacteroid persistence). Simultaneously, plant defense reactions decreased within nodules, suggesting that the expression of symbiotic competence requires the capacity to limit plant immunity. Nitrogen fixation was not acquired in the frame of this evolutionarily short experiment, likely due to the still poor persistence of final clones within nodules compared with the reference rhizobium C. taiwanensis. Our results highlight the potential of experimental evolution in improving symbiotic proficiency and for the elucidation of relationship between symbiotic capacities and elicitation of immune responses.

  19. The model legume genomes

    USDA-ARS?s Scientific Manuscript database

    The primary model legumes to-date have been Medicago truncatula and Lotus japonicus. Both species are tractable both genetically and in the greenhouse, and for both, a substantial sets of tools and resources for molecular genetic research have been assembled. As sequencing costs have declined, howev...

  20. Edible grain legumes

    USDA-ARS?s Scientific Manuscript database

    Edible grain legumes including dry bean, dry pea, chickpeas, and lentils, have served as important sources of protein for human diets for thousands of years. In the US, these crops are predominately produced for export markets. The objective of this study was to examine yield gains in these crops ov...

  1. Extrusion cooking: Legume pulses

    USDA-ARS?s Scientific Manuscript database

    Extrusion is used commercially to produce high value breakfast and snack foods based on cereals such as wheat or corn. However, this processing method is not being commercially used for legume pulses seeds due to the perception that they do not expand well in extrusion. Extrusion cooking of pulses (...

  2. A MAP Kinase Kinase Interacts with SymRK and Regulates Nodule Organogenesis in Lotus japonicus[C][W

    PubMed Central

    Chen, Tao; Zhu, Hui; Ke, Danxia; Cai, Kai; Wang, Chao; Gou, Honglan; Hong, Zonglie; Zhang, Zhongming

    2012-01-01

    The symbiosis receptor kinase, SymRK, is required for root nodule development. A SymRK-interacting protein (SIP2) was found to form protein complex with SymRK in vitro and in planta. The interaction between SymRK and SIP2 is conserved in legumes. The SIP2 gene was expressed in all Lotus japonicus tissues examined. SIP2 represents a typical plant mitogen-activated protein kinase kinase (MAPKK) and exhibited autophosphorylation and transphosphorylation activities. Recombinant SIP2 protein could phosphorylate casein and the Arabidopsis thaliana MAP kinase MPK6. SymRK and SIP2 could not use one another as a substrate for phosphorylation. Instead, SymRK acted as an inhibitor of SIP2 kinase when MPK6 was used as a substrate, suggesting that SymRK may serve as a negative regulator of the SIP2 signaling pathway. Knockdown expression of SIP2 via RNA interference (RNAi) resulted in drastic reduction of nodules formed in transgenic hairy roots. A significant portion of SIP2 RNAi hairy roots failed to form a nodule. In these roots, the expression levels of SIP2 and three marker genes for infection thread and nodule primordium formation were downregulated drastically, while the expression of two other MAPKK genes were not altered. These observations demonstrate an essential role of SIP2 in the early symbiosis signaling and nodule organogenesis. PMID:22353370

  3. Genetic diversity and distribution of rhizobia associated with the medicinal legumes Astragalus spp. and Hedysarum polybotrys in agricultural soils.

    PubMed

    Yan, Hui; Ji, Zhao Jun; Jiao, Yin Shan; Wang, En Tao; Chen, Wen Feng; Guo, Bao Lin; Chen, Wen Xin

    2016-03-01

    With the increasing cultivation of medicinal legumes in agricultural fields, the rhizobia associated with these plants are facing new stresses, mainly from fertilization and irrigation. In this study, investigations on the nodulation of three cultivated medicinal legumes, Astragalus mongholicus, Astragalus membranaceus and Hedysarum polybotrys were performed. Bacterial isolates from root nodules of these legumes were subjected to genetic diversity and multilocus sequence analyses. In addition, the distribution of nodule bacteria related to soil factors and host plants was studied. A total 367 bacterial isolates were obtained and 13 genospecies were identified. The predominant microsymbionts were identified as Mesorhizobium septentrionale, Mesorhizobium temperatum, Mesorhizobium tianshanense, Mesorhizobium ciceri and Mesorhizobium muleiense. M. septentrionale was found in most root nodules especially from legumes grown in the barren soils (with low available nitrogen and low organic carbon contents), while M. temperatum was predominant in nodules where the plants were grown in the nitrogen-rich fields. A. mongholicus tended to be associated with M. septentrionale, M. temperatum and M. ciceri in different soils, while A. membranaceus and H. polybotrys tended to be associated with M. tianshanense and M. septentrionale, respectively. This study showed that soil fertility may be the main determinant for the distribution of rhizobia associated with these cultured legume plants.

  4. Lotus corniculatus nodulation specificity is changed by the presence of a soybean lectin gene

    PubMed

    van Rhijn P; Goldberg; Hirsch

    1998-08-01

    Plant lectins have been implicated as playing an important role in mediating recognition and specificity in the Rhizobium-legume nitrogen-fixing symbiosis. To test this hypothesis, we introduced the soybean lectin gene Le1 either behind its own promoter or behind the cauliflower mosaic virus 35S promoter into Lotus corniculatus, which is nodulated by R. loti. We found that nodulelike outgrowths developed on transgenic L. corniculatus plant roots in response to Bradyrhizobium japonicum, which nodulates soybean and not Lotus spp. Soybean lectin was properly targeted to L. corniculatus root hairs, and although infection threads formed, they aborted in epidermal or hypodermal cells. Mutation of the lectin sugar binding site abolished infection thread formation and nodulation. Incubation of bradyrhizobia in the nodulation (nod) gene-inducing flavonoid genistein increased the number of nodulelike outgrowths on transgenic L. corniculatus roots. Studies of bacterial mutants, however, suggest that a component of the exopolysaccharide surface of B. japonicum, rather than Nod factor, is required for extension of host range to the transgenic L. corniculatus plants.

  5. The Independent Acquisition of Plant Root Nitrogen-Fixing Symbiosis in Fabids Recruited the Same Genetic Pathway for Nodule Organogenesis

    PubMed Central

    Svistoonoff, Sergio; Benabdoun, Faiza Meriem; Nambiar-Veetil, Mathish; Imanishi, Leandro; Vaissayre, Virginie; Cesari, Stella; Diagne, Nathalie; Hocher, Valérie; de Billy, Françoise; Bonneau, Jocelyne; Wall, Luis; Ykhlef, Nadia; Rosenberg, Charles; Bogusz, Didier; Franche, Claudine; Gherbi, Hassen

    2013-01-01

    Only species belonging to the Fabid clade, limited to four classes and ten families of Angiosperms, are able to form nitrogen-fixing root nodule symbioses (RNS) with soil bacteria. This concerns plants of the legume family (Fabaceae) and Parasponia (Cannabaceae) associated with the Gram-negative proteobacteria collectively called rhizobia and actinorhizal plants associated with the Gram-positive actinomycetes of the genus Frankia. Calcium and calmodulin-dependent protein kinase (CCaMK) is a key component of the common signaling pathway leading to both rhizobial and arbuscular mycorrhizal symbioses (AM) and plays a central role in cross-signaling between root nodule organogenesis and infection processes. Here, we show that CCaMK is also needed for successful actinorhiza formation and interaction with AM fungi in the actinorhizal tree Casuarina glauca and is also able to restore both nodulation and AM symbioses in a Medicago truncatula ccamk mutant. Besides, we expressed auto-active CgCCaMK lacking the auto-inhibitory/CaM domain in two actinorhizal species: C. glauca (Casuarinaceae), which develops an intracellular infection pathway, and Discaria trinervis (Rhamnaceae) which is characterized by an ancestral intercellular infection mechanism. In both species, we found induction of nodulation independent of Frankia similar to response to the activation of CCaMK in the rhizobia-legume symbiosis and conclude that the regulation of actinorhiza organogenesis is conserved regardless of the infection mode. It has been suggested that rhizobial and actinorhizal symbioses originated from a common ancestor with several independent evolutionary origins. Our findings are consistent with the recruitment of a similar genetic pathway governing rhizobial and Frankia nodule organogenesis. PMID:23741336

  6. The independent acquisition of plant root nitrogen-fixing symbiosis in Fabids recruited the same genetic pathway for nodule organogenesis.

    PubMed

    Svistoonoff, Sergio; Benabdoun, Faiza Meriem; Nambiar-Veetil, Mathish; Imanishi, Leandro; Vaissayre, Virginie; Cesari, Stella; Diagne, Nathalie; Hocher, Valérie; de Billy, Françoise; Bonneau, Jocelyne; Wall, Luis; Ykhlef, Nadia; Rosenberg, Charles; Bogusz, Didier; Franche, Claudine; Gherbi, Hassen

    2013-01-01

    Only species belonging to the Fabid clade, limited to four classes and ten families of Angiosperms, are able to form nitrogen-fixing root nodule symbioses (RNS) with soil bacteria. This concerns plants of the legume family (Fabaceae) and Parasponia (Cannabaceae) associated with the Gram-negative proteobacteria collectively called rhizobia and actinorhizal plants associated with the Gram-positive actinomycetes of the genus Frankia. Calcium and calmodulin-dependent protein kinase (CCaMK) is a key component of the common signaling pathway leading to both rhizobial and arbuscular mycorrhizal symbioses (AM) and plays a central role in cross-signaling between root nodule organogenesis and infection processes. Here, we show that CCaMK is also needed for successful actinorhiza formation and interaction with AM fungi in the actinorhizal tree Casuarina glauca and is also able to restore both nodulation and AM symbioses in a Medicago truncatula ccamk mutant. Besides, we expressed auto-active CgCCaMK lacking the auto-inhibitory/CaM domain in two actinorhizal species: C. glauca (Casuarinaceae), which develops an intracellular infection pathway, and Discaria trinervis (Rhamnaceae) which is characterized by an ancestral intercellular infection mechanism. In both species, we found induction of nodulation independent of Frankia similar to response to the activation of CCaMK in the rhizobia-legume symbiosis and conclude that the regulation of actinorhiza organogenesis is conserved regardless of the infection mode. It has been suggested that rhizobial and actinorhizal symbioses originated from a common ancestor with several independent evolutionary origins. Our findings are consistent with the recruitment of a similar genetic pathway governing rhizobial and Frankia nodule organogenesis.

  7. A CDPK isoform participates in the regulation of nodule number in Medicago truncatula.

    PubMed

    Gargantini, Pablo R; Gonzalez-Rizzo, Silvina; Chinchilla, Delphine; Raices, Marcela; Giammaria, Verónica; Ulloa, Rita M; Frugier, Florian; Crespi, Martin D

    2006-12-01

    Medicago spp. are able to develop root nodules via symbiotic interaction with Sinorhizobium meliloti. Calcium-dependent protein kinases (CDPKs) are involved in various signalling pathways in plants, and we found that expression of MtCPK3, a CDPK isoform present in roots of the model legume Medicago truncatula, is regulated during the nodulation process. Early inductions were detected 15 min and 3-4 days post-inoculation (dpi). The very early induction of CPK3 messengers was also present in inoculated M. truncatula dmi mutants and in wild-type roots subjected to salt stress, indicating that this rapid response is probably stress-related. In contrast, the later response was concomitant with cortical cell division and the formation of nodule primordia, and was not observed in wild-type roots inoculated with nod (-) strains. This late induction correlated with a change in the subcellular distribution of CDPK activities. Accordingly, an anti-MtCPK3 antibody detected two bands in soluble root extracts and one in the particulate fraction. CPK3::GFP fusions are targeted to the plasma membrane in epidermal onion cells, a localization that depends on myristoylation and palmitoylation sites of the protein, suggesting a dual subcellular localization. MtCPK3 mRNA and protein were also up-regulated by cytokinin treatment, a hormone linked to the regulation of cortical cell division and other nodulation-related responses. An RNAi-CDPK construction was used to silence CPK3 in Agrobacterium rhizogenes-transformed roots. Although no major phenotype was detected in these roots, when infected with rhizobia, the total number of nodules was, on average, twofold higher than in controls. This correlates with the lack of MtCPK3 induction in the inoculated super-nodulator sunn mutant. Our results suggest that CPK3 participates in the regulation of the symbiotic interaction.

  8. Soybean root nodule acid phosphatase.

    PubMed Central

    Penheiter, A R; Duff, S M; Sarath, G

    1997-01-01

    Acid phosphatases are ubiquitous enzymes that exhibit activity against a variety of substrates in vitro, although little is known about their intracellular function. In this study, we report the isolation, characterization, and partial sequence of the major acid phosphatase from soybean (Glycine max L.) root nodules. The phosphatase was purified predominantly as a heterodimer with subunits of 28 and 31 kD; homodimers of both subunits were also observed and exhibited phosphatase activity. In addition to the general phosphatase substrate, p-nitrophenyl phosphate, the heterodimeric form of the enzyme readily hydrolyzed 5'-nucleotides, flavin mononucleotide, and O-phospho-L-Tyr. Low or negligible activity was observed with ATP or polyphosphate. Purified nodule acid phosphatase was stimulated by magnesium, inhibited by calcium and EDTA, and competitively inhibited by cGMP and cAMP with apparent Ki values of 7 and 12 microM, respectively. Partial N-terminal and internal sequencing of the nodule acid phosphatase revealed homology to the soybean vegetative storage proteins. There was a 17-fold increase in enzyme activity and a noticeable increase in protein levels detected by immunoblotting methods during nodule development. Both of these parameters were low in young nodules and reached a peak in mature, functional nodules, suggesting that this enzyme is important for efficient nodule metabolism. PMID:9193092

  9. Differentially expressed genes in mycorrhized and nodulated roots of common bean are associated with defense, cell wall architecture, N metabolism, and P metabolism

    PubMed Central

    Gómez, Brenda-Mariana; Blanco, Lourdes; Lara, Miguel

    2017-01-01

    Legumes participate in two important endosymbiotic associations, with phosphorus-acquiring arbuscular mycorrhiza (AM, soil fungi) and with nitrogen-fixing bacterial rhizobia. These divergent symbionts share a common symbiotic signal transduction pathway that facilitates the establishment of mycorrhization and nodulation in legumes. However, the unique and shared downstream genes essential for AM and nodule development have not been identified in crop legumes. Here, we used ion torrent next-generation sequencing to perform comparative transcriptomics of common bean (Phaseolus vulgaris) roots colonized by AM or rhizobia. We analyzed global gene expression profiles to identify unique and shared differentially expressed genes (DEGs) that regulate these two symbiotic interactions, and quantitatively compared DEG profiles. We identified 3,219 (1,959 upregulated and 1,260 downregulated) and 2,645 (1,247 upregulated and 1,398 downregulated) unigenes that were differentially expressed in response to mycorrhizal or rhizobial colonization, respectively, compared with uninoculated roots. We obtained quantitative expression profiles of unique and shared genes involved in processes related to defense, cell wall structure, N metabolism, and P metabolism in mycorrhized and nodulated roots. KEGG pathway analysis indicated that most genes involved in jasmonic acid and salicylic acid signaling, N metabolism, and inositol phosphate metabolism are variably expressed during symbiotic interactions. These combined data provide valuable information on symbiotic gene signaling networks that respond to mycorrhizal and rhizobial colonization, and serve as a guide for future genetic strategies to enhance P uptake and N-fixing capacity to increase the net yield of this valuable grain legume. PMID:28771548

  10. Differentially expressed genes in mycorrhized and nodulated roots of common bean are associated with defense, cell wall architecture, N metabolism, and P metabolism.

    PubMed

    Nanjareddy, Kalpana; Arthikala, Manoj-Kumar; Gómez, Brenda-Mariana; Blanco, Lourdes; Lara, Miguel

    2017-01-01

    Legumes participate in two important endosymbiotic associations, with phosphorus-acquiring arbuscular mycorrhiza (AM, soil fungi) and with nitrogen-fixing bacterial rhizobia. These divergent symbionts share a common symbiotic signal transduction pathway that facilitates the establishment of mycorrhization and nodulation in legumes. However, the unique and shared downstream genes essential for AM and nodule development have not been identified in crop legumes. Here, we used ion torrent next-generation sequencing to perform comparative transcriptomics of common bean (Phaseolus vulgaris) roots colonized by AM or rhizobia. We analyzed global gene expression profiles to identify unique and shared differentially expressed genes (DEGs) that regulate these two symbiotic interactions, and quantitatively compared DEG profiles. We identified 3,219 (1,959 upregulated and 1,260 downregulated) and 2,645 (1,247 upregulated and 1,398 downregulated) unigenes that were differentially expressed in response to mycorrhizal or rhizobial colonization, respectively, compared with uninoculated roots. We obtained quantitative expression profiles of unique and shared genes involved in processes related to defense, cell wall structure, N metabolism, and P metabolism in mycorrhized and nodulated roots. KEGG pathway analysis indicated that most genes involved in jasmonic acid and salicylic acid signaling, N metabolism, and inositol phosphate metabolism are variably expressed during symbiotic interactions. These combined data provide valuable information on symbiotic gene signaling networks that respond to mycorrhizal and rhizobial colonization, and serve as a guide for future genetic strategies to enhance P uptake and N-fixing capacity to increase the net yield of this valuable grain legume.

  11. Regulatory patterns of a large family of defensin-like genes expressed in nodules of Medicago truncatula

    USDA-ARS?s Scientific Manuscript database

    Root nodules are the symbiotic organ of legumes that house nitrogen-fixing bacteria. Many genes are specifically induced in nodules during the interactions between the host plant and symbiotic rhizobia. Information regarding the regulation of expression for most of these genes is lacking. One of the...

  12. Specific Subunits of Heterotrimeric G Proteins Play Important Roles during Nodulation in Soybean1[W][OA

    PubMed Central

    Choudhury, Swarup Roy; Pandey, Sona

    2013-01-01

    Heterotrimeric G proteins comprising Gα, Gβ, and Gγ subunits regulate many fundamental growth and development processes in all eukaryotes. Plants possess a relatively limited number of G-protein components compared with mammalian systems, and their detailed functional characterization has been performed mostly in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa). However, the presence of single Gα and Gβ proteins in both these species has significantly undermined the complexity and specificity of response regulation in plant G-protein signaling. There is ample pharmacological evidence for the role of G proteins in regulation of legume-specific processes such as nodulation, but the lack of genetic data from a leguminous species has restricted its direct assessment. Our recent identification and characterization of an elaborate G-protein family in soybean (Glycine max) and the availability of appropriate molecular-genetic resources have allowed us to directly evaluate the role of G-protein subunits during nodulation. We demonstrate that all G-protein genes are expressed in nodules and exhibit significant changes in their expression in response to Bradyrhizobium japonicum infection and in representative supernodulating and nonnodulating soybean mutants. RNA interference suppression and overexpression of specific G-protein components results in lower and higher nodule numbers, respectively, validating their roles as positive regulators of nodule formation. Our data further show preferential usage of distinct G-protein subunits in the presence of an additional signal during nodulation. Interestingly, the Gα proteins directly interact with the soybean nodulation factor receptors NFR1α and NFR1β, suggesting that the plant G proteins may couple with receptors other than the canonical heptahelical receptors common in metazoans to modulate signaling. PMID:23569109

  13. Crowdsourcing the nodulation gene network discovery environment.

    PubMed

    Li, Yupeng; Jackson, Scott A

    2016-05-26

    The Legumes (Fabaceae) are an economically and ecologically important group of plant species with the conspicuous capacity for symbiotic nitrogen fixation in root nodules, specialized plant organs containing symbiotic microbes. With the aim of understanding the underlying molecular mechanisms leading to nodulation, many efforts are underway to identify nodulation-related genes and determine how these genes interact with each other. In order to accurately and efficiently reconstruct nodulation gene network, a crowdsourcing platform, CrowdNodNet, was created. The platform implements the jQuery and vis.js JavaScript libraries, so that users are able to interactively visualize and edit the gene network, and easily access the information about the network, e.g. gene lists, gene interactions and gene functional annotations. In addition, all the gene information is written on MediaWiki pages, enabling users to edit and contribute to the network curation. Utilizing the continuously updated, collaboratively written, and community-reviewed Wikipedia model, the platform could, in a short time, become a comprehensive knowledge base of nodulation-related pathways. The platform could also be used for other biological processes, and thus has great potential for integrating and advancing our understanding of the functional genomics and systems biology of any process for any species. The platform is available at http://crowd.bioops.info/ , and the source code can be openly accessed at https://github.com/bioops/crowdnodnet under MIT License.

  14. Functional analysis of duplicated Symbiosis Receptor Kinase (SymRK) genes during nodulation and mycorrhizal infection in soybean (Glycine max).

    PubMed

    Indrasumunar, Arief; Wilde, Julia; Hayashi, Satomi; Li, Dongxue; Gresshoff, Peter M

    2015-03-15

    Association between legumes and rhizobia results in the formation of root nodules, where symbiotic nitrogen fixation occurs. The early stages of this association involve a complex of signalling events between the host and microsymbiont. Several genes dealing with early signal transduction have been cloned, and one of them encodes the leucine-rich repeat (LRR) receptor kinase (SymRK; also termed NORK). The Symbiosis Receptor Kinase gene is required by legumes to establish a root endosymbiosis with Rhizobium bacteria as well as mycorrhizal fungi. Using degenerate primer and BAC sequencing, we cloned duplicated SymRK homeologues in soybean called GmSymRKα and GmSymRKβ. These duplicated genes have high similarity of nucleotide (96%) and amino acid sequence (95%). Sequence analysis predicted a malectin-like domain within the extracellular domain of both genes. Several putative cis-acting elements were found in promoter regions of GmSymRKα and GmSymRKβ, suggesting a participation in lateral root development, cell division and peribacteroid membrane formation. The mutant of SymRK genes is not available in soybean; therefore, to know the functions of these genes, RNA interference (RNAi) of these duplicated genes was performed. For this purpose, RNAi construct of each gene was generated and introduced into the soybean genome by Agrobacterium rhizogenes-mediated hairy root transformation. RNAi of GmSymRKβ gene resulted in an increased reduction of nodulation and mycorrhizal infection than RNAi of GmSymRKα, suggesting it has the major activity of the duplicated gene pair. The results from the important crop legume soybean confirm the joint phenotypic action of GmSymRK genes in both mycorrhizal and rhizobial infection seen in model legumes.

  15. Crotalarieae and Genisteae of the South African Great Escarpment are nodulated by novel Bradyrhizobium species with unique and diverse symbiotic loci.

    PubMed

    Beukes, Chrizelle W; Stępkowski, Tomasz; Venter, Stephanus N; Cłapa, Tomasz; Phalane, Francina L; le Roux, Marianne M; Steenkamp, Emma T

    2016-07-01

    The genus Bradyrhizobium contains predominantly nitrogen-fixing legume symbionts. Phylogenetic analysis of the genes responsible for their symbiotic abilities (i.e., those encoded on the nodulation [nod] and nitrogen-fixation [nif] loci) has facilitated the development of an extensive phylogeographic framework for the genus. This framework however contains only a few nodulating isolates from Africa. Here we focused on nodulating Bradyrhizobium isolates associated with native southern African legumes in the tribes Genisteae and Crotalarieae found along the Great Escarpment in the Mpumalanga Province of South Africa. The aims of this study were to: (1) obtain rhizobial isolates from legumes in the Genisteae and Crotalarieae; (2) verify their nodulation ability; (3) characterize them to species level based on phylogenetic analyses of several protein coding gene regions (atpD, dnaK, glnII, recA, rpoB and gyrB) and (4) determine their placement in the phylogeographic framework inferred from the sequences of the symbiotic loci nodA and nifD. Twenty of the 21 Bradyrhizobium isolates belonged to six novel species, while one was conspecific with the recently described B. arachidis. Among these isolates, the nodA phylogeny revealed several new clades, with 18 of our isolates found in Clades XIV and XV, and only three forming part of the cosmopolitan Clade III. These strains formed predominantly the same groups in the nifD phylogeny although with slight differences; indicating that both vertical and horizontal inheritance of the symbiotic loci occurred. These findings suggest that the largely unexplored diversity of indigenous African rhizobia are characterized by unique ancestries that might mirror the distribution of their hosts and the environmental factors driving their evolution. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Drought Stress, Permeability to O2 Diffusion, and the Respiratory Kinetics of Soybean Root Nodules.

    PubMed Central

    Del Castillo, L. D.; Layzell, D. B.

    1995-01-01

    In legume nodules, treatments such as detopping or nitrate fertilization inhibit nodule metabolism and N2 fixation by decreasing the nodule's permeability to O2 diffusion, thereby decreasing the infected cell O2 concentration (Oi) and increasing the degree to which nodule metabolism is limited by O2 availability. In the present study we used nodule oximetry to assess and compare the role of O2 limitation in soybean (Glycine max L. Merr) nodules inhibited by either drought or detopping. Compared to detopping, drought caused only minor decreases in Oi, and when the external O2 concentration was increased to raise Oi, the infected cell respiration rate in the drought-stressed plants was not stimulated as much as it was in the nodules of the detopped plants. Unlike those in detopped plants, nodules exposed to moderate drought stress displayed an O2-sufficient respiration rate that was significantly lower than that in control nodules. Despite possible side effects of oximetry in altering nodule metabolism, these results provided direct evidence that, compared to detopping, O2 limitation plays a minor role in the inhibition of nodule metabolism during drought stress and changes in nodule permeability are the effect, not the cause, of a drought-induced inhibition of nodule metabolism and the O2-suffiecient rate of respiration. PMID:12228425

  17. Global Synthesis of Drought Effects on Food Legume Production

    PubMed Central

    Daryanto, Stefani; Wang, Lixin; Jacinthe, Pierre-André

    2015-01-01

    Food legume crops play important roles in conservation farming systems and contribute to food security in the developing world. However, in many regions of the world, their production has been adversely affected by drought. Although water scarcity is a severe abiotic constraint of legume crops productivity, it remains unclear how the effects of drought co-vary with legume species, soil texture, agroclimatic region, and drought timing. To address these uncertainties, we collected literature data between 1980 and 2014 that reported monoculture legume yield responses to drought under field conditions, and analyzed this data set using meta-analysis techniques. Our results showed that the amount of water reduction was positively related with yield reduction, but the extent of the impact varied with legume species and the phenological state during which drought occurred. Overall, lentil (Lens culinaris), groundnut (Arachis hypogaea), and pigeon pea (Cajanus cajan) were found to experience lower drought-induced yield reduction compared to legumes such as cowpea (Vigna unguiculata) and green gram (Vigna radiate). Yield reduction was generally greater when legumes experienced drought during their reproductive stage compared to during their vegetative stage. Legumes grown in soil with medium texture also exhibited greater yield reduction compared to those planted on soil of either coarse or fine texture. In contrast, regions and their associated climatic factors did not significantly affect legume yield reduction. In the face of changing climate, our study provides useful information for agricultural planning and research directions for development of drought-resistant legume species to improve adaptation and resilience of agricultural systems in the drought-prone regions of the world. PMID:26061704

  18. Global Synthesis of Drought Effects on Food Legume Production.

    PubMed

    Daryanto, Stefani; Wang, Lixin; Jacinthe, Pierre-André

    2015-01-01

    Food legume crops play important roles in conservation farming systems and contribute to food security in the developing world. However, in many regions of the world, their production has been adversely affected by drought. Although water scarcity is a severe abiotic constraint of legume crops productivity, it remains unclear how the effects of drought co-vary with legume species, soil texture, agroclimatic region, and drought timing. To address these uncertainties, we collected literature data between 1980 and 2014 that reported monoculture legume yield responses to drought under field conditions, and analyzed this data set using meta-analysis techniques. Our results showed that the amount of water reduction was positively related with yield reduction, but the extent of the impact varied with legume species and the phenological state during which drought occurred. Overall, lentil (Lens culinaris), groundnut (Arachis hypogaea), and pigeon pea (Cajanus cajan) were found to experience lower drought-induced yield reduction compared to legumes such as cowpea (Vigna unguiculata) and green gram (Vigna radiate). Yield reduction was generally greater when legumes experienced drought during their reproductive stage compared to during their vegetative stage. Legumes grown in soil with medium texture also exhibited greater yield reduction compared to those planted on soil of either coarse or fine texture. In contrast, regions and their associated climatic factors did not significantly affect legume yield reduction. In the face of changing climate, our study provides useful information for agricultural planning and research directions for development of drought-resistant legume species to improve adaptation and resilience of agricultural systems in the drought-prone regions of the world.

  19. Diversity of rhizobia from nodules of the leguminous tree Gliricidia sepium, a natural host of Rhizobium tropici.

    PubMed

    Acosta-Durán, Carlos; Martínez-Romero, Esperanza

    2002-08-01

    The Rhizobium species that nodulate the legume tree Gliricidia sepium were analyzed by phenotypic characteristics (including nodule formation in different hosts), PCR-RFLP patterns and sequences of 16S rRNA genes, multilocus enzyme electrophoresis, and plasmid patterns. Strains of Rhizobium tropici type A and B, Sinorhizobium spp., and Rhizobium etli bv. phaseoli were encountered in G. sepium nodules and their presence depended on the site sampled.

  20. Clover development during spaceflight: A model system

    NASA Technical Reports Server (NTRS)

    Guikema, James A.; Debell, Lynnette; Paulsen, Avelina; Spooner, Brian S.; Wong, Peter P.

    1994-01-01

    The development of legume root nodules was studied as a model system for the examination of gravitational effects on plant root development. In order to examine whether rhizobial association with clover roots can be achieved in microgravity, experiments were performed aboard the KC-135 parabolic aircraft and aboard the sounding rocket mission Consort 3. Binding of rhizobia to roots and the initial stages of root nodule development successfully occurred in microgravity. Seedling germination experiments were performed in the sliding block device, the Materials Dispersion Apparatus, aboard STS-37. When significant hydration of the seeds was achieved, normal rates of germination and seedling development were observed.

  1. Clover development during spaceflight: a model system.

    PubMed

    Guikema, J A; DeBell, L; Paulsen, A; Spooner, B S; Wong, P P

    1994-01-01

    The development of legume root nodules was studied as a model system for the examination of gravitational effects on plant root development. In order to examine whether rhizobial association with clover roots can be achieved in microgravity, experiments were performed aboard the KC-135 parabolic aircraft and aboard the sounding rocket mission Consort 3. Binding of rhizobia to roots and the initial stages of root nodule development successfully occurred in microgravity. Seedling germination experiments were performed in the sliding block device, the Materials Dispersion Apparatus, aboard STS-37. When significant hydration of the seeds was achieved, normal rates of germination and seedling development were observed.

  2. Clover development during spaceflight: A model system

    NASA Astrophysics Data System (ADS)

    Guikema, James A.; Debell, Lynnette; Paulsen, Avelina; Spooner, Brian S.; Wong, Peter P.

    1994-08-01

    The development of legume root nodules was studied as a model system for the examination of gravitational effects on plant root development. In order to examine whether rhizobial association with clover roots can be achieved in microgravity, experiments were performed aboard the KC-135 parabolic aircraft and aboard the sounding rocket mission Consort 3. Binding of rhizobia to roots and the initial stages of root nodule development successfully occurred in microgravity. Seedling germination experiments were performed in the sliding block device, the Materials Dispersion Apparatus, aboard STS-37. When significant hydration of the seeds was achieved, normal rates of germination and seedling development were observed.

  3. Ethylene, a Hormone at the Center-Stage of Nodulation

    PubMed Central

    Guinel, Frédérique C.

    2015-01-01

    Nodulation is the result of a beneficial interaction between legumes and rhizobia. It is a sophisticated process leading to nutrient exchange between the two types of symbionts. In this association, within a nodule, the rhizobia, using energy provided as photosynthates, fix atmospheric nitrogen and convert it to ammonium which is available to the plant. Nodulation is recognized as an essential process in nitrogen cycling and legume crops are known to enrich agricultural soils in nitrogenous compounds. Furthermore, as they are rich in nitrogen, legumes are considered important as staple foods for humans and fodder for animals. To tightly control this association and keep it mutualistic, the plant uses several means, including hormones. The hormone ethylene has been known as a negative regulator of nodulation for almost four decades. Since then, much progress has been made in the understanding of both the ethylene signaling pathway and the nodulation process. Here I have taken a large view, using recently obtained knowledge, to describe in some detail the major stages of the process. I have not only reviewed the steps most commonly covered (the common signaling transduction pathway, and the epidermal and cortical programs), but I have also looked into steps less understood (the pre-infection step with the plant defense response, the bacterial release and the formation of the symbiosome, and nodule functioning and senescence). After a succinct review of the ethylene signaling pathway, I have used the knowledge obtained from nodulation- and ethylene-related mutants to paint a more complete picture of the role played by the hormone in nodule organogenesis, functioning, and senescence. It transpires that ethylene is at the center of this effective symbiosis. It has not only been involved in most of the steps leading to a mature nodule, but it has also been implicated in host immunity and nodule senescence. It is likely responsible for the activation of other hormonal

  4. Ethylene, a Hormone at the Center-Stage of Nodulation.

    PubMed

    Guinel, Frédérique C

    2015-01-01

    Nodulation is the result of a beneficial interaction between legumes and rhizobia. It is a sophisticated process leading to nutrient exchange between the two types of symbionts. In this association, within a nodule, the rhizobia, using energy provided as photosynthates, fix atmospheric nitrogen and convert it to ammonium which is available to the plant. Nodulation is recognized as an essential process in nitrogen cycling and legume crops are known to enrich agricultural soils in nitrogenous compounds. Furthermore, as they are rich in nitrogen, legumes are considered important as staple foods for humans and fodder for animals. To tightly control this association and keep it mutualistic, the plant uses several means, including hormones. The hormone ethylene has been known as a negative regulator of nodulation for almost four decades. Since then, much progress has been made in the understanding of both the ethylene signaling pathway and the nodulation process. Here I have taken a large view, using recently obtained knowledge, to describe in some detail the major stages of the process. I have not only reviewed the steps most commonly covered (the common signaling transduction pathway, and the epidermal and cortical programs), but I have also looked into steps less understood (the pre-infection step with the plant defense response, the bacterial release and the formation of the symbiosome, and nodule functioning and senescence). After a succinct review of the ethylene signaling pathway, I have used the knowledge obtained from nodulation- and ethylene-related mutants to paint a more complete picture of the role played by the hormone in nodule organogenesis, functioning, and senescence. It transpires that ethylene is at the center of this effective symbiosis. It has not only been involved in most of the steps leading to a mature nodule, but it has also been implicated in host immunity and nodule senescence. It is likely responsible for the activation of other hormonal

  5. From model to crop: functional analysis of a STAY-GREEN gene in the model legume Medicago truncatula and effective use of the gene for alfalfa improvement.

    PubMed

    Zhou, Chuanen; Han, Lu; Pislariu, Catalina; Nakashima, Jin; Fu, Chunxiang; Jiang, Qingzhen; Quan, Li; Blancaflor, Elison B; Tang, Yuhong; Bouton, Joseph H; Udvardi, Michael; Xia, Guangmin; Wang, Zeng-Yu

    2011-11-01

    Medicago truncatula has been developed into a model legume. Its close relative alfalfa (Medicago sativa) is the most widely grown forage legume crop in the United States. By screening a large population of M. truncatula mutants tagged with the transposable element of tobacco (Nicotiana tabacum) cell type1 (Tnt1), we identified a mutant line (NF2089) that maintained green leaves and showed green anthers, central carpels, mature pods, and seeds during senescence. Genetic and molecular analyses revealed that the mutation was caused by Tnt1 insertion in a STAY-GREEN (MtSGR) gene. Transcript profiling analysis of the mutant showed that loss of the MtSGR function affected the expression of a large number of genes involved in different biological processes. Further analyses revealed that SGR is implicated in nodule development and senescence. MtSGR expression was detected across all nodule developmental zones and was higher in the senescence zone. The number of young nodules on the mutant roots was higher than in the wild type. Expression levels of several nodule senescence markers were reduced in the sgr mutant. Based on the MtSGR sequence, an alfalfa SGR gene (MsSGR) was cloned, and transgenic alfalfa lines were produced by RNA interference. Silencing of MsSGR led to the production of stay-green transgenic alfalfa. This beneficial trait offers the opportunity to produce premium alfalfa hay with a more greenish appearance. In addition, most of the transgenic alfalfa lines retained more than 50% of chlorophylls during senescence and had increased crude protein content. This study illustrates the effective use of knowledge gained from a model system for the genetic improvement of an important commercial crop.

  6. Widespread fitness alignment in the legume-rhizobium symbiosis.

    PubMed

    Friesen, Maren L

    2012-06-01

    Although 'cheaters' potentially destabilize the legume-rhizobium mutualism, we lack a comprehensive review of host-symbiont fitness correlations. Studies measuring rhizobium relative or absolute fitness and host benefit are surveyed. Mutant studies are tallied for evidence of pleiotropy; studies of natural strains are analyzed with meta-analysis. Of 80 rhizobium mutations, 19 decrease both partners' fitness, four increase both, two increase host fitness but decrease symbiont fitness and none increase symbiont fitness at the host's expense. The pooled correlation between rhizobium nodulation competitiveness and plant aboveground biomass is 0.65 across five experiments that compete natural strains against a reference, whereas, across 14 experiments that compete rhizobia against soil populations or each other, the pooled correlation is 0.24. Pooled correlations between aboveground biomass and nodule number and nodule biomass are 0.76 and 0.83. Positive correlations between legume and rhizobium fitness imply that most ineffective rhizobia are 'defective' rather than 'defectors'; this extends to natural variants, with only one significant fitness conflict. Most studies involve non-coevolved associations, indicating that fitness alignment is the default state. Rhizobium mutations that increase both host and symbiont fitness suggest that some plants maladaptively restrict symbiosis with novel strains.

  7. Facultative nitrogen fixation by canopy legumes in a lowland tropical forest.

    PubMed

    Barron, Alexander R; Purves, Drew W; Hedin, Lars O

    2011-02-01

    Symbiotic dinitrogen (N(2)) fixation is often invoked to explain the N richness of tropical forests as ostensibly N(2)-fixing trees can be a major component of the community. Such arguments assume N(2) fixers are fixing N when present. However, in laboratory experiments, legumes consistently reduce N(2) fixation in response to increased soil N availability. These contrasting views of N(2) fixation as either obligate or facultative have drastically different implications for the N cycle of tropical forests. We tested these models by directly measuring N(2)-fixing root nodules and nitrogenase activity of individual canopy-dominant legume trees (Inga sp.) across several lowland forest types. Fixation was substantial in disturbed forests and some gaps but near zero in the high N soils of mature forest. Our findings suggest that canopy legumes closely regulate N(2) fixation, leading to large variations in N inputs across the landscape, and low symbiotic fixation in mature forests despite abundant legumes.

  8. Local and Systemic Regulation of Plant Root System Architecture and Symbiotic Nodulation by a Receptor-Like Kinase

    PubMed Central

    Huault, Emeline; Laffont, Carole; Wen, Jiangqi; Mysore, Kirankumar S.; Ratet, Pascal; Duc, Gérard; Frugier, Florian

    2014-01-01

    In plants, root system architecture is determined by the activity of root apical meristems, which control the root growth rate, and by the formation of lateral roots. In legumes, an additional root lateral organ can develop: the symbiotic nitrogen-fixing nodule. We identified in Medicago truncatula ten allelic mutants showing a compact root architecture phenotype (cra2) independent of any major shoot phenotype, and that consisted of shorter roots, an increased number of lateral roots, and a reduced number of nodules. The CRA2 gene encodes a Leucine-Rich Repeat Receptor-Like Kinase (LRR-RLK) that primarily negatively regulates lateral root formation and positively regulates symbiotic nodulation. Grafting experiments revealed that CRA2 acts through different pathways to regulate these lateral organs originating from the roots, locally controlling the lateral root development and nodule formation systemically from the shoots. The CRA2 LRR-RLK therefore integrates short- and long-distance regulations to control root system architecture under non-symbiotic and symbiotic conditions. PMID:25521478

  9. A phylogenetic strategy based on a legume-specific whole genome duplication yields symbiotic cytokinin type-A response regulators.

    PubMed

    Op den Camp, Rik H M; De Mita, Stéphane; Lillo, Alessandra; Cao, Qingqin; Limpens, Erik; Bisseling, Ton; Geurts, René

    2011-12-01

    Legumes host their Rhizobium spp. symbiont in novel root organs called nodules. Nodules originate from differentiated root cortical cells that dedifferentiate and subsequently form nodule primordia, a process controlled by cytokinin. A whole-genome duplication has occurred at the root of the legume Papilionoideae subfamily. We hypothesize that gene pairs originating from this duplication event and are conserved in distinct Papilionoideae lineages have evolved symbiotic functions. A phylogenetic strategy was applied to search for such gene pairs to identify novel regulators of nodulation, using the cytokinin phosphorelay pathway as a test case. In this way, two paralogous type-A cytokinin response regulators were identified that are involved in root nodule symbiosis. Response Regulator9 (MtRR9) and MtRR11 in medicago (Medicago truncatula) and an ortholog in lotus (Lotus japonicus) are rapidly induced upon Rhizobium spp. Nod factor signaling. Constitutive expression of MtRR9 results in arrested primordia that have emerged from cortical, endodermal, and pericycle cells. In legumes, lateral root primordia are not exclusively formed from pericycle cells but also require the involvement of the root cortical cell layer. Therefore, the MtRR9-induced foci of cell divisions show a strong resemblance to lateral root primordia, suggesting an ancestral function of MtRR9 in this process. Together, these findings provide a proof of principle for the applied phylogenetic strategy to identify genes with a symbiotic function in legumes.

  10. Casuarina glauca prenodule cells display the same differentiation as the corresponding nodule cells.

    PubMed

    Laplaze, L; Duhoux, E; Franche, C; Frutz, T; Svistoonoff, S; Bisseling, T; Bogusz, D; Pawlowski, K

    2000-01-01

    Recent phylogenetic studies have implied that all plants able to enter root nodule symbioses with nitrogen-fixing bacteria go back to a common ancestor (D.E. Soltis, P.S. Soltis, D.R. Morgan, S.M. Swensen, B.C. Mullin, J.M. Dowd, and P.G. Martin, Proc. Natl. Acad. Sci. USA, 92:2647-2651, 1995). However, nodules formed by plants from different groups are distinct in nodule organogenesis and structure. In most groups, nodule organogenesis involves the induction of cortical cell divisions. In legumes these divisions lead to the formation of a nodule primordium, while in non-legumes they lead to the formation of a so-called prenodule consisting of infected and uninfected cells. Nodule primordium formation does not involve prenodule cells, and the function of prenodules is not known. Here, we examine the differentiation of actinorhizal prenodule cells in comparison to nodule cells with regard to both symbionts. Our findings indicate that prenodules represent primitive symbiotic organs whose cell types display the same characteristics as their nodule counterparts. The results are discussed in the context of the evolution of root nodule symbioses.

  11. Deciphering composition and function of the root microbiome of a legume plant.

    PubMed

    Hartman, Kyle; van der Heijden, Marcel Ga; Roussely-Provent, Valexia; Walser, Jean-Claude; Schlaeppi, Klaus

    2017-01-17

    Diverse assemblages of microbes colonize plant roots and collectively function as a microbiome. Earlier work has characterized the root microbiomes of numerous plant species, but little information is available for legumes despite their key role in numerous ecosystems including agricultural systems. Legumes form a root nodule symbiosis with nitrogen-fixing Rhizobia bacteria and thereby account for large, natural nitrogen inputs into soils. Here, we describe the root bacteria microbiome of the legume Trifolium pratense combining culture-dependent and independent methods. For a functional understanding of individual microbiome members and their impact on plant growth, we began to inoculate root microbiome members alone or in combination to Trifolium roots. At a whole-root scale, Rhizobia bacteria accounted for ~70% of the root microbiome. Other enriched members included bacteria from the genera Pantoea, Sphingomonas, Novosphingobium, and Pelomonas. We built a reference stock of 200 bacteria isolates, and we found that they corresponded to ~20% of the abundant root microbiome members. We developed a microcosm system to conduct simplified microbiota inoculation experiments with plants. We observed that while an abundant root microbiome member reduced plant growth when inoculated alone, this negative effect was alleviated if this Flavobacterium was co-inoculated with other root microbiome members. The Trifolium root microbiome was dominated by nutrient-providing Rhizobia bacteria and enriched for bacteria from genera that may provide disease protection. First microbiota inoculation experiments indicated that individual community members can have plant growth compromising activities without being apparently pathogenic, and a more diverse root community can alleviate plant growth compromising activities of its individual members. A trait-based characterization of the reference stock bacteria will permit future microbiota manipulation experiments to decipher overall

  12. Total Glutamine Synthetase Activity during Soybean Nodule Development Is Controlled at the Level of Transcription and Holoprotein Turnover.

    PubMed Central

    Temple, S. J.; Kunjibettu, S.; Roche, D.; Sengupta-Gopalan, C.

    1996-01-01

    Gln synthetase (GS) catalyzes the ATP-dependent condensation of ammonia with glutamate to yield Gln. In higher plants GS is an octameric enzyme and the subunits are encoded by members of a small multigene family. In soybeans (Glycine max), following the onset of N2 fixation there is a dramatic increase in GS activity in the root nodules. GS activity staining of native polyacrylamide gels containing nodule and root extracts showed a common band of activity (GSrs). The nodules also contained a slower-migrating, broad band of enzyme activity (GSns). The GSns activity band is a complex of many isozymes made up of different proportions of two kinds of GS subunits: GSr and GSn. Root nodules formed following inoculation with an Nif- strain of Bradyrhizobium japonicum showed the presence of GS isoenzymes (GSns1) with low enzyme activity, which migrated more slowly than GSns. Gsns1 is most likely made up predominantly of GSn subunits. Our data suggest that, whereas the class I GS genes encoding the GSr subunits are regulated by the availability of NH3, the class II GS genes coding for the GSn subunits are developmentally regulated. Furthermore, we have demonstrated that the GSns1 isozymes in the Nif- nodules are relatively more labile. Our overall conclusion is that GSns activity in soybean nodules is regulated by N2 fixation both at the level of transcription and at the level of holoprotein stability. PMID:12226474

  13. Ribosomal protein biomarkers provide root nodule bacterial identification by MALDI-TOF MS.

    PubMed

    Ziegler, Dominik; Pothier, Joël F; Ardley, Julie; Fossou, Romain Kouakou; Pflüger, Valentin; de Meyer, Sofie; Vogel, Guido; Tonolla, Mauro; Howieson, John; Reeve, Wayne; Perret, Xavier

    2015-07-01

    Accurate identification of soil bacteria that form nitrogen-fixing associations with legume crops is challenging given the phylogenetic diversity of root nodule bacteria (RNB). The labor-intensive and time-consuming 16S ribosomal RNA (rRNA) sequencing and/or multilocus sequence analysis (MLSA) of conserved genes so far remain the favored molecular tools to characterize symbiotic bacteria. With the development of mass spectrometry (MS) as an alternative method to rapidly identify bacterial isolates, we recently showed that matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) can accurately characterize RNB found inside plant nodules or grown in cultures. Here, we report on the development of a MALDI-TOF RNB-specific spectral database built on whole cell MS fingerprints of 116 strains representing the major rhizobial genera. In addition to this RNB-specific module, which was successfully tested on unknown field isolates, a subset of 13 ribosomal proteins extracted from genome data was found to be sufficient for the reliable identification of nodule isolates to rhizobial species as shown in the putatively ascribed ribosomal protein masses (PARPM) database. These results reveal that data gathered from genome sequences can be used to expand spectral libraries to aid the accurate identification of bacterial species by MALDI-TOF MS.

  14. Overexpression of alfalfa cytosolic glutamine synthetase in nodules and flowers of transgenic Lotus japonicus plants.

    PubMed

    Suárez, Ramón; Márquez, Judith; Shishkova, Svetlana; Hernández, Georgina

    2003-03-01

    Legumes can obtain nitrogen from symbiotic nitrogen fixation in root nodules. The glutamine synthetase/glutamate synthase cycle is responsible for the initial nitrogen assimilation. This work reports the analysis of transgenic Lotus japonicus plants with the chimeric gene containing the alfalfa cytosolic glutamine synthetase (GS1) (EC 6.3.1.2) gene controlled by the Sesbania rostrata leghemoglobin gene promoter (Srglb3p). Surprisingly, all of the transgenic primary transformants analysed were sterile. Two transformants designated GS39 and GS44 were further analysed. GS in nodules of GS39 and GS44 plants was upregulated, at the level of transcript and protein. The transgenic plants had 2-fold higher nodule GS activity and similar root GS activity compared to control plants. The GS39 and GS44 sterile plants showed morphological alterations in pollen grains and in ovules. An increase in GS transcript abundance and enzyme activity was measured during early and late stages of flower development of GS plants. Flowers of GS plants showed higher glutamine content, resulting in an increased glutamine/glutamate ratio. The GS transcript and protein were detected in ovules. These data indicate that overexpression of GS1 in reproductive organs critically affects their development and might be a reason for sterility of L. japonicus plants.

  15. Large-Scale Development of Cost-Effective Single-Nucleotide Polymorphism Marker Assays for Genetic Mapping in Pigeonpea and Comparative Mapping in Legumes

    PubMed Central

    Saxena, Rachit K.; Varma Penmetsa, R.; Upadhyaya, Hari D.; Kumar, Ashish; Carrasquilla-Garcia, Noelia; Schlueter, Jessica A.; Farmer, Andrew; Whaley, Adam M.; Sarma, Birinchi K.; May, Gregory D.; Cook, Douglas R.; Varshney, Rajeev K.

    2012-01-01

    Single-nucleotide polymorphisms (SNPs, >2000) were discovered by using RNA-seq and allele-specific sequencing approaches in pigeonpea (Cajanus cajan). For making the SNP genotyping cost-effective, successful competitive allele-specific polymerase chain reaction (KASPar) assays were developed for 1616 SNPs and referred to as PKAMs (pigeonpea KASPar assay markers). Screening of PKAMs on 24 genotypes [23 from cultivated species and 1 wild species (Cajanus scarabaeoides)] defined a set of 1154 polymorphic markers (77.4%) with a polymorphism information content (PIC) value from 0.04 to 0.38. One thousand and ninety-four PKAMs showed polymorphisms between parental lines of the reference mapping population (C. cajan ICP 28 × C. scarabaeoides ICPW 94). By using high-quality marker genotyping data on 167 F2 lines from the population, a comprehensive genetic map comprising 875 PKAMs with an average inter-marker distance of 1.11 cM was developed. Previously mapped 35 simple sequence repeat markers were integrated into the PKAM map and an integrated genetic map of 996.21 cM was constructed. Mapped PKAMs showed a higher degree of synteny with the genome of Glycine max followed by Medicago truncatula and Lotus japonicus and least with Vigna unguiculata. These PKAMs will be useful for genetics research and breeding applications in pigeonpea and for utilizing genome information from other legume species. PMID:23103470

  16. Organogenic nodule formation in hop: a tool to study morphogenesis in plants with biotechnological and medicinal applications.

    PubMed

    Fortes, Ana M; Santos, Filipa; Pais, Maria S

    2010-01-01

    The usage of Humulus lupulus for brewing increased the demand for high-quality plant material. Simultaneously, hop has been used in traditional medicine and recently recognized with anticancer and anti-infective properties. Tissue culture techniques have been reported for a wide range of species, and open the prospect for propagation of disease-free, genetically uniform and massive amounts of plants in vitro. Moreover, the development of large-scale culture methods using bioreactors enables the industrial production of secondary metabolites. Reliable and efficient tissue culture protocol for shoot regeneration through organogenic nodule formation was established for hop. The present review describes the histological, and biochemical changes occurring during this morphogenic process, together with an analysis of transcriptional and metabolic profiles. We also discuss the existence of common molecular factors among three different morphogenic processes: organogenic nodules and somatic embryogenesis, which strictly speaking depend exclusively on intrinsic developmental reprogramming, and legume nitrogen-fixing root nodules, which arises in response to symbiosis. The review of the key factors that participate in hop nodule organogenesis and the comparison with other morphogenic processes may have merit as a study presenting recent advances in complex molecular networks occurring during morphogenesis and together, these provide a rich framework for biotechnology applications.

  17. Organogenic Nodule Formation in Hop: A Tool to Study Morphogenesis in Plants with Biotechnological and Medicinal Applications

    PubMed Central

    Fortes, Ana M.; Santos, Filipa; Pais, Maria S.

    2010-01-01

    The usage of Humulus lupulus for brewing increased the demand for high-quality plant material. Simultaneously, hop has been used in traditional medicine and recently recognized with anticancer and anti-infective properties. Tissue culture techniques have been reported for a wide range of species, and open the prospect for propagation of disease-free, genetically uniform and massive amounts of plants in vitro. Moreover, the development of large-scale culture methods using bioreactors enables the industrial production of secondary metabolites. Reliable and efficient tissue culture protocol for shoot regeneration through organogenic nodule formation was established for hop. The present review describes the histological, and biochemical changes occurring during this morphogenic process, together with an analysis of transcriptional and metabolic profiles. We also discuss the existence of common molecular factors among three different morphogenic processes: organogenic nodules and somatic embryogenesis, which strictly speaking depend exclusively on intrinsic developmental reprogramming, and legume nitrogen-fixing root nodules, which arises in response to symbiosis. The review of the key factors that participate in hop nodule organogenesis and the comparison with other morphogenic processes may have merit as a study presenting recent advances in complex molecular networks occurring during morphogenesis and together, these provide a rich framework for biotechnology applications. PMID:20811599

  18. Effects of legume species introduction on vegetation and soil nutrient development on abandoned croplands in a semi-arid environment on the Loess Plateau, China.

    PubMed

    Yuan, Zi-Qiang; Yu, Kai-Liang; Epstein, Howard; Fang, Chao; Li, Jun-Ting; Liu, Qian-Qian; Liu, Xue-Wei; Gao, Wen-Juan; Li, Feng-Min

    2016-01-15

    Revegetation facilitated by legume species introduction has been used for soil erosion control on the Loess Plateau, China. However, it is still unclear how vegetation and soil resources develop during this restoration process, especially over the longer term. In this study, we investigated the changes of plant aboveground biomass, vegetation cover, species richness and density of all individuals, and soil total nitrogen, mineral nitrogen, total phosphorus and available phosphorus over 11 years from 2003 to 2013 in three treatments (natural revegetation, Medicago sativa L. introduction and Melilotus suaveolens L. introduction) on the semi-arid Loess Plateau. Medicago significantly increased aboveground biomass and vegetation cover, and soil total nitrogen and mineral nitrogen contents. The Medicago treatment had lower species richness and density of all individuals, lower soil moisture in the deep soil (i.e., 1.4-5m), and lower soil available phosphorus. Melilotus introduction significantly increased aboveground biomass in only the first two years, and it was not an effective approach to improve vegetation biomass and cover, and soil nutrients, especially in later stages of revegetation. Overall, our study suggests that M. sativa can be the preferred plant species for revegetation of degraded ecosystems on the Loess Plateau, although phosphorus fertilizer should be applied for the sustainability of the revegetation.

  19. Rhizobial strains isolated from nodules of Medicago marina in southwest Spain are abiotic-stress tolerant and symbiotically diverse.

    PubMed

    Alías-Villegas, Cynthia; Cubo, M Teresa; Lara-Dampier, Victoria; Bellogín, Ramón A; Camacho, María; Temprano, Francisco; Espuny, M Rosario

    2015-10-01

    The isolation and characterisation of nitrogen-fixing root nodule bacteria from Medicago marina, a tolerant legume species, were studied in two areas from southwest Spain. A total of 30 out of 82 isolates with distinct ERIC-PCR fingerprints were analysed on the basis of molecular (PCR-RFLP of the 16S-23S rDNA intergenic spacer region (IGS) with two endonucleases, analysis of the 16S rDNA and symbiotic nodC gene sequences, plasmid profiles and SDS-PAGE of LPS, including the partial sequence of the housekeeping gene glnII and the symbiotic gene nodA of some representatives), physiological (utilisation of sole carbon sources, tolerance to antibiotics, NaCl, heavy metals, temperature and pH) and symbiotic parameters (efficacy on M. marina, M. minima, M. murex, M. orbicularis, M. polymorpha, M. sativa and M. truncatula). All the bacteria isolated from M. marina nodules belonged to Ensifer meliloti, except for one strain that belonged to E. medicae. To determine the nodulation range of M. marina, 10 different Ensifer species were tested for their ability to nodulate on this plant. E. kummerowiae CCBAU 71714 and the E. medicae control strain M19.1 were the only Ensifer species tested that developed nitrogen-fixing nodules on this plant. Most of the M. marina-nodulating strains showed tolerance to stress factors and all of them shared the presence of a gene similar to cadA, a gene that encodes for a PIB-type ATPase, which is a transporter belonging to the large superfamily of ATP-driven pumps involved in the transport of metals across cell membranes. Copyright © 2015 Elsevier GmbH. All rights reserved.

  20. Novel Expression Pattern of Cytosolic Gln Synthetase in Nitrogen-Fixing Root Nodules of the Actinorhizal Host, Datisca glomerata1[w

    PubMed Central

    Berry, Alison M.; Murphy, Terence M.; Okubara, Patricia A.; Jacobsen, Karin R.; Swensen, Susan M.; Pawlowski, Katharina

    2004-01-01

    Gln synthetase (GS) is the key enzyme of primary ammonia assimilation in nitrogen-fixing root nodules of legumes and actinorhizal (Frankia-nodulated) plants. In root nodules of Datisca glomerata (Datiscaceae), transcripts hybridizing to a conserved coding region of the abundant nodule isoform, DgGS1-1, are abundant in uninfected nodule cortical tissue, but expression was not detectable in the infected zone or in the nodule meristem. Similarly, the GS holoprotein is immunolocalized exclusively to the uninfected nodule tissue. Phylogenetic analysis of the full-length cDNA of DgGS1-1 indicates affinities with cytosolic GS genes from legumes, the actinorhizal species Alnus glutinosa, and nonnodulating species, Vitis vinifera and Hevea brasilensis. The D. glomerata nodule GS expression pattern is a new variant among reported root nodule symbioses and may reflect an unusual nitrogen transfer pathway from the Frankia nodule microsymbiont to the plant infected tissue, coupled to a distinctive nitrogen cycle in the uninfected cortical tissue. Arg, Gln, and Glu are the major amino acids present in D. glomerata nodules, but Arg was not detected at high levels in leaves or roots. Arg as a major nodule nitrogen storage form is not found in other root nodule types except in the phylogenetically related Coriaria. Catabolism of Arg through the urea cycle could generate free ammonium in the uninfected tissue where GS is expressed. PMID:15247391

  1. Responses of Legume Versus Nonlegume Tropical Tree Seedlings to Elevated CO2 Concentration1[OA

    PubMed Central

    Cernusak, Lucas A.; Winter, Klaus; Martínez, Carlos; Correa, Edwin; Aranda, Jorge; Garcia, Milton; Jaramillo, Carlos; Turner, Benjamin L.

    2011-01-01

    We investigated responses of growth, leaf gas exchange, carbon-isotope discrimination, and whole-plant water-use efficiency (WP) to elevated CO2 concentration ([CO2]) in seedlings of five leguminous and five nonleguminous tropical tree species. Plants were grown at CO2 partial pressures of 40 and 70 Pa. As a group, legumes did not differ from nonlegumes in growth response to elevated [CO2]. The mean ratio of final plant dry mass at elevated to ambient [CO2] (ME/MA) was 1.32 and 1.24 for legumes and nonlegumes, respectively. However, there was large variation in ME/MA among legume species (0.92–2.35), whereas nonlegumes varied much less (1.21–1.29). Variation among legume species in ME/MA was closely correlated with their capacity for nodule formation, as expressed by nodule mass ratio, the dry mass of nodules for a given plant dry mass. WP increased markedly in response to elevated [CO2] in all species. The ratio of intercellular to ambient CO2 partial pressures during photosynthesis remained approximately constant at ambient and elevated [CO2], as did carbon isotope discrimination, suggesting that WP should increase proportionally for a given increase in atmospheric [CO2]. These results suggest that tree legumes with a strong capacity for nodule formation could have a competitive advantage in tropical forests as atmospheric [CO2] rises and that the water-use efficiency of tropical tree species will increase under elevated [CO2]. PMID:21788363

  2. Responses of legume versus nonlegume tropical tree seedlings to elevated CO2 concentration.

    PubMed

    Cernusak, Lucas A; Winter, Klaus; Martínez, Carlos; Correa, Edwin; Aranda, Jorge; Garcia, Milton; Jaramillo, Carlos; Turner, Benjamin L

    2011-09-01

    We investigated responses of growth, leaf gas exchange, carbon-isotope discrimination, and whole-plant water-use efficiency (W(P)) to elevated CO(2) concentration ([CO(2)]) in seedlings of five leguminous and five nonleguminous tropical tree species. Plants were grown at CO(2) partial pressures of 40 and 70 Pa. As a group, legumes did not differ from nonlegumes in growth response to elevated [CO(2)]. The mean ratio of final plant dry mass at elevated to ambient [CO(2)] (M(E)/M(A)) was 1.32 and 1.24 for legumes and nonlegumes, respectively. However, there was large variation in M(E)/M(A) among legume species (0.92-2.35), whereas nonlegumes varied much less (1.21-1.29). Variation among legume species in M(E)/M(A) was closely correlated with their capacity for nodule formation, as expressed by nodule mass ratio, the dry mass of nodules for a given plant dry mass. W(P) increased markedly in response to elevated [CO(2)] in all species. The ratio of intercellular to ambient CO(2) partial pressures during photosynthesis remained approximately constant at ambient and elevated [CO(2)], as did carbon isotope discrimination, suggesting that W(P) should increase proportionally for a given increase in atmospheric [CO(2)]. These results suggest that tree legumes with a strong capacity for nodule formation could have a competitive advantage in tropical forests as atmospheric [CO(2)] rises and that the water-use efficiency of tropical tree species will increase under elevated [CO(2)].

  3. Beneficial consequences of a selective glutamine synthetase inhibitor in oats and legumes

    SciTech Connect

    Langston-Unkefer, P.J.; Knight, T.J.; Sengupta-Gopalan, C.

    1988-01-01

    We report on the effects of administering a unique glutamine synthetase inhibitor to cereals and N/sub 2/-fixing legumes. A bacterium (Pseudomonas syringae pv. tabaci) delivers this inhibitor to provide extended treatment periods; we inoculated the root systems of oat and legume plants with pv. tabaci to provide for delivery of this inhibitor to their root or root/nodule systems. Inoculation of legumes is accompanied by increased plant growth, total plant nitrogen, nodulation, and nitrogen fixation activity. Inoculation of the oats is accompanied by either of two results depending upon the genotype of the oat plant. One result is inhibition of plant growth followed by plant death as consequences of the loss of all of the glutamine synthetase activities in the plant and the subsequent accumulation of ammonia and cessation of nitrate uptake. The second and opposite result is observed in a small population of oats screened from a commercial cultivar and includes increased plant growth and leaf protein. The effects of this inhibitor can be beneficial when applied to appropriate plant material. In an attempt to effectively communicate these findings to the reader, we first introduce the inhibitor (a novel amino acid) and its bacterial delivery systems, the target of the inhibitor (glutamine synthetase-catalyzed ammonia assimilation), and the two different nitrogen economics in the legume and cereal plants used experimentally. The physiological, biochemical, and molecular genetic consequences of the inhibitor action in cereals and legumes, as we presently understand them, are then presented. 18 refs., 4 figs., 3 tabs.,

  4. [Study of the root nodules in some species of the Papilionaceae subfamily by scanning electron microscopy].

    PubMed

    Novikova, T I; Gordienko, N Ia

    2001-01-01

    Nitrogen-fixing nodules from 16 species in 6 tribes of the sub-family Papilionaceae have been examined by scanning electron microscopy. The structure of infection threads was similar in all the studied papilionoid species except Lupinus polyphillus. In this species the infection threads were found in young nodules only. The morphology of bacterioids and the character of their "package" are determined by the host plant genotype. The obtained results are discussed in relation to the evolution of the legumes.

  5. Competition by Bradyrhizobium Strains for Nodulation of the Nonlegume Parasponia andersonii

    PubMed Central

    Trinick, M. J.; Hadobas, P. A.

    1989-01-01

    Bradyrhizobium strains isolated from the nonlegume Parasponia spp. formed a group of strains that were highly competitive for nodulation of P. andersonii when paired with strains isolated from legumes. Strains from legumes, including those of similar effectiveness to NGR231 and CP283, were not able to form nodules as single occupants on P. andersonii in the presence of Parasponia strains. However, NGR86, an isolate from Macroptilium lathyroides, jointly occupied one-third of the nodules formed with each of the three strains isolated from Parasponia spp. Time taken for nodules to appear may have influenced the outcome of competition, since CP283 and all isolates from legumes were slow to nodulate P. andersonii. Among the Parasponia strains, competitiveness for nodulation of P. andersonii was not associated with effectiveness of nitrogen fixation. The highly effective strain CP299 was a poor competitor when paired with the least effective strain NGR231. CP283 was the least competitive of the Parasponia strains but was still able to dominate nodules when paired with legume isolates. Dual occupancy was high, up to 67% when the inoculum contained CP299 and CP273. Both the Muc+ and Muc- types of CP283 form a symbiosis of similar effectiveness and were similarly competitive at high inoculation densities, but the Muc- form was more competitive at low inoculum densities. Both forms frequently occupied the same nodule. Bradyrhizobium strains isolated from Parasponia spp. may have specific genetic information that favor their ability to competitively and effectively infect plants in the genus Parasponia (Ulmaceae) outside the Leguminosae. PMID:16347913

  6. High-Resolution Transcriptomic Analyses of Sinorhizobium sp. NGR234 Bacteroids in Determinate Nodules of Vigna unguiculata and Indeterminate Nodules of Leucaena leucocephala

    PubMed Central

    Li, Yan; Tian, Chang Fu; Chen, Wen Feng; Wang, Lei; Sui, Xin Hua; Chen, Wen Xin

    2013-01-01

    The rhizobium-legume symbiosis is a model system for studying mutualistic interactions between bacteria and eukaryotes. Sinorhizobium sp. NGR234 is distinguished by its ability to form either indeterminate nodules or determinate nodules with diverse legumes. Here, we presented a high-resolution RNA-seq transcriptomic analysis of NGR234 bacteroids in indeterminate nodules of Leucaena leucocephala and determinate nodules of Vigna unguiculata. In contrast to exponentially growing free-living bacteria, non-growing bacteroids from both legumes recruited several common cellular functions such as cbb3 oxidase, thiamine biosynthesis, nitrate reduction pathway (NO-producing), succinate metabolism, PHB (poly-3-hydroxybutyrate) biosynthesis and phosphate/phosphonate transporters. However, different transcription profiles between bacteroids from two legumes were also uncovered for genes involved in the biosynthesis of exopolysaccharides, lipopolysaccharides, T3SS (type three secretion system) and effector proteins, cytochrome bd ubiquinol oxidase, PQQ (pyrroloquinoline quinone), cytochrome c550, pseudoazurin, biotin, phasins and glycolate oxidase, and in the metabolism of glutamate and phenylalanine. Noteworthy were the distinct expression patterns of genes encoding phasins, which are thought to be involved in regulating the surface/volume ratio of PHB granules. These patterns are in good agreement with the observed granule size difference between bacteroids from L. leucocephala and V. unguiculata. PMID:23936444

  7. High-resolution transcriptomic analyses of Sinorhizobium sp. NGR234 bacteroids in determinate nodules of Vigna unguiculata and indeterminate nodules of Leucaena leucocephala.

    PubMed

    Li, Yan; Tian, Chang Fu; Chen, Wen Feng; Wang, Lei; Sui, Xin Hua; Chen, Wen Xin

    2013-01-01

    The rhizobium-legume symbiosis is a model system for studying mutualistic interactions between bacteria and eukaryotes. Sinorhizobium sp. NGR234 is distinguished by its ability to form either indeterminate nodules or determinate nodules with diverse legumes. Here, we presented a high-resolution RNA-seq transcriptomic analysis of NGR234 bacteroids in indeterminate nodules of Leucaena leucocephala and determinate nodules of Vigna unguiculata. In contrast to exponentially growing free-living bacteria, non-growing bacteroids from both legumes recruited several common cellular functions such as cbb3 oxidase, thiamine biosynthesis, nitrate reduction pathway (NO-producing), succinate metabolism, PHB (poly-3-hydroxybutyrate) biosynthesis and phosphate/phosphonate transporters. However, different transcription profiles between bacteroids from two legumes were also uncovered for genes involved in the biosynthesis of exopolysaccharides, lipopolysaccharides, T3SS (type three secretion system) and effector proteins, cytochrome bd ubiquinol oxidase, PQQ (pyrroloquinoline quinone), cytochrome c550, pseudoazurin, biotin, phasins and glycolate oxidase, and in the metabolism of glutamate and phenylalanine. Noteworthy were the distinct expression patterns of genes encoding phasins, which are thought to be involved in regulating the surface/volume ratio of PHB granules. These patterns are in good agreement with the observed granule size difference between bacteroids from L. leucocephala and V. unguiculata.

  8. Shoot HAR1 mediates nitrate inhibition of nodulation in Lotus japonicus.

    PubMed

    Okamoto, Satoru; Kawaguchi, Masayoshi

    2015-01-01

    Nitrate is a major environmental factor in the inhibition of nodulation. In a model legume Lotus japonicus, a CLV1-like receptor kinase, HAR1, mediates nitrate inhibition and autoregulation of nodulation. Autoregulation of nodulation involves root-to-shoot-to-root long-distance communication, and HAR1 functions in shoots. However, it remains elusive where HAR1 functions in the nitrate inhibition of nodulation. We performed grafting experiments with the har1 mutant under various nitrate conditions, and found that shoot HAR1 is critical for the inhibition of nodulation at 10 mM nitrate. Combined with our recent finding that the nitrate-induced CLE-RS2 glycopeptide binds directly to the HAR1 receptor, this result suggests that CLE-RS2/HAR1 long-distance signaling plays an important role in the both nitrate inhibition and the autoregulation of nodulation.

  9. Narrow- and Broad-Host-Range Symbiotic Plasmids of Rhizobium spp. Strains That Nodulate Phaseolus vulgaris

    PubMed Central

    Brom, Susana; Martinez, Esperanza; Dávila, Guillermo; Palacios, Rafael

    1988-01-01

    Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and single-copy nitrogenase genes conferred a Fix+ phenotype to the Agrobacterium transconjugants. A Fix− phenotype was obtained with Sym plasmids of strains isolated from P. vulgaris nodules that had a narrow host range and reiterated nif genes, as well as with Sym plasmids of strains isolated from other legumes that presented single nif genes and a broad nodulation host range. This indicates that different types of Sym plasmids can confer the ability to establish an effective symbiosis with P. vulgaris. Images PMID:16347637

  10. Potential of rice stubble as a reservoir of bradyrhizobial inoculum in rice-legume crop rotation.

    PubMed

    Piromyou, Pongdet; Greetatorn, Teerana; Teamtisong, Kamonluck; Tittabutr, Panlada; Boonkerd, Nantakorn; Teaumroong, Neung

    2017-09-15

    concern due to NO possible deleterious effect on rice growth. In addition, this study reports the application of endophytic bradyrhizobia in rice stubbles, and the rice stubbles were used directly as an inoculum for a leguminous plant (mung bean). The degradation of rice stubbles leads to an increased number of SUTN9-2 in the soil and may result in increased mung bean nodulation. Therefore, the persistence of endophytic bradyrhizobia in rice tissues can be developed for using rice stubbles as inoculum for mung bean in the system of rice - legume crop rotation. Copyright © 2017 American Society for Microbiology.

  11. A Novel Sucrose-Regulatory MADS-Box Transcription Factor GmNMHC5 Promotes Root Development and Nodulation in Soybean (Glycine max [L.] Merr.).

    PubMed

    Liu, Wei; Han, Xiangdong; Zhan, Ge; Zhao, Zhenfang; Feng, Yongjun; Wu, Cunxiang

    2015-08-31

    The MADS-box protein family includes many transcription factors that have a conserved DNA-binding MADS-box domain. The proteins in this family were originally recognized to play prominent roles in floral development. Recent findings, especially with regard to the regulatory roles of the AGL17 subfamily in root development, have greatly broadened their known functions. In this study, a gene from soybean (Glycine max [L.] Merr.), GmNMHC5, was cloned from the Zigongdongdou cultivar and identified as a member of the AGL17 subfamily. Real-time fluorescence quantitative PCR analysis showed that GmNMHC5 was expressed at much higher levels in roots and nodules than in other organs. The activation of expression was first examined in leaves and roots, followed by shoot apexes. GmNMHC5 expression levels rose sharply when the plants were treated under short-day conditions (SD) and started to pod, whereas low levels were maintained in non-podding plants under l