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Sample records for arabidopsis shoot apical

  1. An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis

    PubMed Central

    Guo, Hongyan; Zhang, Wei; Tian, Hainan; Zheng, Kaijie; Dai, Xuemei; Liu, Shanda; Hu, Qingnan; Wang, Xianling; Liu, Bao; Wang, Shucai

    2015-01-01

    Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance, and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa) CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION) gene, as an auxin response gene, and the functional characterization of OsCLE48 in Arabidopsis and rice. OsCLE48 encodes a CLE peptide hormone that is similar to Arabidopsis CLEs. RT-PCR analysis showed that OsCLE48 was induced by exogenously application of IAA (indole-3-acetic acid), a naturally occurred auxin. Expression of integrated OsCLE48p:GUS reporter gene in transgenic Arabidopsis plants was also induced by exogenously IAA treatment. These results indicate that OsCLE48 is an auxin responsive gene. Histochemical staining showed that GUS activity was detected in all the tissue and organs of the OsCLE48p:GUS transgenic Arabidopsis plants. Expression of OsCLE48 under the control of the 35S promoter in Arabidopsis inhibited shoot apical meristem development. Expression of OsCLE48 under the control of the CLV3 native regulatory elements almost completely complemented clv3-2 mutant phenotypes, suggesting that OsCLE48 is functionally similar to CLV3. On the other hand, expression of OsCLE48 under the control of the 35S promoter in Arabidopsis has little, if any effects on root apical meristem development, and transgenic rice plants overexpressing OsCLE48 are morphologically indistinguishable from wild type plants, suggesting that the functions of some CLE peptides may not be fully conserved in Arabidopsis and rice. Taken together, our results showed that OsCLE48 is an auxin responsive peptide hormone gene, and it regulates shoot apical

  2. An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis.

    PubMed

    Guo, Hongyan; Zhang, Wei; Tian, Hainan; Zheng, Kaijie; Dai, Xuemei; Liu, Shanda; Hu, Qingnan; Wang, Xianling; Liu, Bao; Wang, Shucai

    2015-01-01

    Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance, and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa) CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION) gene, as an auxin response gene, and the functional characterization of OsCLE48 in Arabidopsis and rice. OsCLE48 encodes a CLE peptide hormone that is similar to Arabidopsis CLEs. RT-PCR analysis showed that OsCLE48 was induced by exogenously application of IAA (indole-3-acetic acid), a naturally occurred auxin. Expression of integrated OsCLE48p:GUS reporter gene in transgenic Arabidopsis plants was also induced by exogenously IAA treatment. These results indicate that OsCLE48 is an auxin responsive gene. Histochemical staining showed that GUS activity was detected in all the tissue and organs of the OsCLE48p:GUS transgenic Arabidopsis plants. Expression of OsCLE48 under the control of the 35S promoter in Arabidopsis inhibited shoot apical meristem development. Expression of OsCLE48 under the control of the CLV3 native regulatory elements almost completely complemented clv3-2 mutant phenotypes, suggesting that OsCLE48 is functionally similar to CLV3. On the other hand, expression of OsCLE48 under the control of the 35S promoter in Arabidopsis has little, if any effects on root apical meristem development, and transgenic rice plants overexpressing OsCLE48 are morphologically indistinguishable from wild type plants, suggesting that the functions of some CLE peptides may not be fully conserved in Arabidopsis and rice. Taken together, our results showed that OsCLE48 is an auxin responsive peptide hormone gene, and it regulates shoot apical

  3. The ERECTA receptor kinase regulates Arabidopsis shoot apical meristem size, phyllotaxy and floral meristem identity

    PubMed Central

    Mandel, Tali; Moreau, Fanny; Kutsher, Yaarit; Fletcher, Jennifer C.; Carles, Cristel C.; Williams, Leor Eshed

    2014-01-01

    In plants, the shoot apical meristem (SAM) serves as a reservoir of pluripotent stem cells from which all above ground organs originate. To sustain proper growth, the SAM must maintain homeostasis between the self-renewal of pluripotent stem cells and cell recruitment for lateral organ formation. At the core of the network that regulates this homeostasis in Arabidopsis are the WUSCHEL (WUS) transcription factor specifying stem cell fate and the CLAVATA (CLV) ligand-receptor system limiting WUS expression. In this study, we identified the ERECTA (ER) pathway as a second receptor kinase signaling pathway that regulates WUS expression, and therefore shoot apical and floral meristem size, independently of the CLV pathway. We demonstrate that reduction in class III HD-ZIP and ER function together leads to a significant increase in WUS expression, resulting in extremely enlarged shoot meristems and a switch from spiral to whorled vegetative phyllotaxy. We further show that strong upregulation of WUS in the inflorescence meristem leads to ectopic expression of the AGAMOUS homeotic gene to a level that switches cell fate from floral meristem founder cell to carpel founder cell, suggesting an indirect role for ER in regulating floral meristem identity. This work illustrates the delicate balance between stem cell specification and differentiation in the meristem and shows that a shift in this balance leads to abnormal phyllotaxy and to altered reproductive cell fate. PMID:24496620

  4. Sample Preparation of Arabidopsis thaliana Shoot Apices for Expression Studies of Photoperiod-Induced Genes.

    PubMed

    Andrés, Fernando; Torti, Stefano; Vincent, Coral; Coupland, George

    2016-01-01

    Plants produce new organs from a population of pluripotent cells which are located in specific tissues called meristems. One of these meristems, the shoot apical meristem (SAM), gives rise to leaves during the vegetative phase and flowers during the reproductive phase. The transition from vegetative SAM to an inflorescence meristem (IM) is a dramatic developmental switch, which has been particularly well studied in the model species Arabidopsis thaliana. This developmental switch is controlled by multiple environmental signals such as day length (or photoperiod), and it is accompanied by changes in expression of hundreds of genes. A major interest in plant biology is to identify and characterize those genes which are regulated in the stem cells of the SAM in response to the photoperiodic signals. In this sense, techniques such as RNA in situ hybridization (RNA ISH) have been very successfully employed to detect the temporal and spatial expression patterns of genes in the SAM. This method can be specifically optimized for photoperiodic-flowering studies. In this chapter, we describe improved methods to generate plant material and histological samples to be combined with RNA ISH in flowering-related studies. PMID:26867617

  5. Mechanically, the Shoot Apical Meristem of Arabidopsis Behaves like a Shell Inflated by a Pressure of About 1 MPa

    PubMed Central

    Beauzamy, Léna; Louveaux, Marion; Hamant, Olivier; Boudaoud, Arezki

    2015-01-01

    In plants, the shoot apical meristem contains the stem cells and is responsible for the generation of all aerial organs. Mechanistically, organogenesis is associated with an auxin-dependent local softening of the epidermis. This has been proposed to be sufficient to trigger outgrowth, because the epidermis is thought to be under tension and stiffer than internal tissues in all the aerial part of the plant. However, this has not been directly demonstrated in the shoot apical meristem. Here we tested this hypothesis in Arabidopsis using indentation methods and modeling. We considered two possible scenarios: either the epidermis does not have unique properties and the meristem behaves as a homogeneous linearly-elastic tissue, or the epidermis is under tension and the meristem exhibits the response of a shell under pressure. Large indentation depths measurements with a large tip (~size of the meristem) were consistent with a shell-like behavior. This also allowed us to deduce a value of turgor pressure, estimated at 0.82±0.16 MPa. Indentation with atomic force microscopy provided local measurements of pressure in the epidermis, further confirming the range of values obtained from large deformations. Altogether, our data demonstrate that the Arabidopsis shoot apical meristem behaves like a shell under a MPa range pressure and support a key role for the epidermis in shaping the shoot apex. PMID:26635855

  6. The ERECTA receptor kinase regulates Arabidopsis shoot apical meristem size, phyllotaxy and floral meristem identity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In plants, the shoot apical meristem (SAM) serves as a reservoir of pluripotent stem cells from which all above ground organs originate. To sustain proper growth, the SAM must maintain homeostasis between the self-renewal of pluripotent stem cells and cell recruitment for lateral organ formation. At...

  7. The mitochondrial protease AtFTSH4 safeguards Arabidopsis shoot apical meristem function.

    PubMed

    Dolzblasz, Alicja; Smakowska, Elwira; Gola, Edyta M; Sokołowska, Katarzyna; Kicia, Marta; Janska, Hanna

    2016-01-01

    The shoot apical meristem (SAM) ensures continuous plant growth and organogenesis. In LD 30 °C, plants lacking AtFTSH4, an ATP-dependent mitochondrial protease that counteracts accumulation of internal oxidative stress, exhibit a puzzling phenotype of premature SAM termination. We aimed to elucidate the underlying cellular and molecular processes that link AtFTSH4 with SAM arrest. We studied AtFTSH4 expression, internal oxidative stress accumulation, and SAM morphology. Directly in the SAM we analysed H2O2 accumulation, mitochondria behaviour, and identity of stem cells using WUS/CLV3 expression. AtFTSH4 was expressed in proliferating tissues, particularly during the reproductive phase. In the mutant, SAM, in which internal oxidative stress accumulates predominantly at 30 °C, lost its meristematic fate. This process was progressive and stage-specific. Premature meristem termination was associated with an expansion in SAM area, where mitochondria lost their functionality. All these effects destabilised the identity of the stem cells. SAM termination in ftsh4 mutants is caused both by internal oxidative stress accumulation with time/age and by the tissue-specific role of AtFTSH4 around the flowering transition. Maintaining mitochondria functionality within the SAM, dependent on AtFTSH4, is vital to preserving stem cell activity throughout development. PMID:27321362

  8. The mitochondrial protease AtFTSH4 safeguards Arabidopsis shoot apical meristem function

    PubMed Central

    Dolzblasz, Alicja; Smakowska, Elwira; Gola, Edyta M.; Sokołowska, Katarzyna; Kicia, Marta; Janska, Hanna

    2016-01-01

    The shoot apical meristem (SAM) ensures continuous plant growth and organogenesis. In LD 30 °C, plants lacking AtFTSH4, an ATP-dependent mitochondrial protease that counteracts accumulation of internal oxidative stress, exhibit a puzzling phenotype of premature SAM termination. We aimed to elucidate the underlying cellular and molecular processes that link AtFTSH4 with SAM arrest. We studied AtFTSH4 expression, internal oxidative stress accumulation, and SAM morphology. Directly in the SAM we analysed H2O2 accumulation, mitochondria behaviour, and identity of stem cells using WUS/CLV3 expression. AtFTSH4 was expressed in proliferating tissues, particularly during the reproductive phase. In the mutant, SAM, in which internal oxidative stress accumulates predominantly at 30 °C, lost its meristematic fate. This process was progressive and stage-specific. Premature meristem termination was associated with an expansion in SAM area, where mitochondria lost their functionality. All these effects destabilised the identity of the stem cells. SAM termination in ftsh4 mutants is caused both by internal oxidative stress accumulation with time/age and by the tissue-specific role of AtFTSH4 around the flowering transition. Maintaining mitochondria functionality within the SAM, dependent on AtFTSH4, is vital to preserving stem cell activity throughout development. PMID:27321362

  9. A correlative microscopy approach relates microtubule behaviour, local organ geometry, and cell growth at the Arabidopsis shoot apical meristem

    PubMed Central

    Burian, Agata; Uyttewaal, Magalie

    2013-01-01

    Cortical microtubules (CMTs) are often aligned in a particular direction in individual cells or even in groups of cells and play a central role in the definition of growth anisotropy. How the CMTs themselves are aligned is not well known, but two hypotheses have been proposed. According to the first hypothesis, CMTs align perpendicular to the maximal growth direction, and, according to the second, CMTs align parallel to the maximal stress direction. Since both hypotheses were formulated on the basis of mainly qualitative assessments, the link between CMT organization, organ geometry, and cell growth is revisited using a quantitative approach. For this purpose, CMT orientation, local curvature, and growth parameters for each cell were measured in the growing shoot apical meristem (SAM) of Arabidopsis thaliana. Using this approach, it has been shown that stable CMTs tend to be perpendicular to the direction of maximal growth in cells at the SAM periphery, but parallel in the cells at the boundary domain. When examining the local curvature of the SAM surface, no strict correlation between curvature and CMT arrangement was found, which implies that SAM geometry, and presumed geometry-derived stress distribution, is not sufficient to prescribe the CMT orientation. However, a better match between stress and CMTs was found when mechanical stress derived from differential growth was also considered. PMID:24153420

  10. The Essential Gene EMB1611 Maintains Shoot Apical Meristem Function During Arabidopsis Development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Arabidopsis thaliana genome contains hundreds of genes essential for seed development. Because null mutations in these genes cause embryo lethality, their specific molecular and developmental functions are largely unknown. Here, we identify a role for EMB1611/MEE22, an essential gene in Arabidop...

  11. Centering the Organizing Center in the Arabidopsis thaliana Shoot Apical Meristem by a Combination of Cytokinin Signaling and Self-Organization

    PubMed Central

    Adibi, Milad; Yoshida, Saiko; Weijers, Dolf; Fleck, Christian

    2016-01-01

    Plants have the ability to continously generate new organs by maintaining populations of stem cells throught their lives. The shoot apical meristem (SAM) provides a stable environment for the maintenance of stem cells. All cells inside the SAM divide, yet boundaries and patterns are maintained. Experimental evidence indicates that patterning is independent of cell lineage, thus a dynamic self-regulatory mechanism is required. A pivotal role in the organization of the SAM is played by the WUSCHEL gene (WUS). An important question in this regard is that how WUS expression is positioned in the SAM via a cell-lineage independent signaling mechanism. In this study we demonstrate via mathematical modeling that a combination of an inhibitor of the Cytokinin (CK) receptor, Arabidopsis histidine kinase 4 (AHK4) and two morphogens originating from the top cell layer, can plausibly account for the cell lineage-independent centering of WUS expression within SAM. Furthermore, our laser ablation and microsurgical experiments support the hypothesis that patterning in SAM occurs at the level of CK reception and signaling. The model suggests that the interplay between CK signaling, WUS/CLV feedback loop and boundary signals can account for positioning of the WUS expression, and provides directions for further experimental investigation. PMID:26872130

  12. Centering the Organizing Center in the Arabidopsis thaliana Shoot Apical Meristem by a Combination of Cytokinin Signaling and Self-Organization.

    PubMed

    Adibi, Milad; Yoshida, Saiko; Weijers, Dolf; Fleck, Christian

    2016-01-01

    Plants have the ability to continously generate new organs by maintaining populations of stem cells throught their lives. The shoot apical meristem (SAM) provides a stable environment for the maintenance of stem cells. All cells inside the SAM divide, yet boundaries and patterns are maintained. Experimental evidence indicates that patterning is independent of cell lineage, thus a dynamic self-regulatory mechanism is required. A pivotal role in the organization of the SAM is played by the WUSCHEL gene (WUS). An important question in this regard is that how WUS expression is positioned in the SAM via a cell-lineage independent signaling mechanism. In this study we demonstrate via mathematical modeling that a combination of an inhibitor of the Cytokinin (CK) receptor, Arabidopsis histidine kinase 4 (AHK4) and two morphogens originating from the top cell layer, can plausibly account for the cell lineage-independent centering of WUS expression within SAM. Furthermore, our laser ablation and microsurgical experiments support the hypothesis that patterning in SAM occurs at the level of CK reception and signaling. The model suggests that the interplay between CK signaling, WUS/CLV feedback loop and boundary signals can account for positioning of the WUS expression, and provides directions for further experimental investigation. PMID:26872130

  13. Using high competent shoot apical meristems of cockscomb as explants for studying function of ASYMMETRIC LEAVES2-LIKE11 (ASL11) gene of Arabidopsis.

    PubMed

    Sun, Shao-Bo; Meng, Lai-Sheng; Sun, Xu-Dong; Feng, Zhen-Hua

    2010-12-01

    Though shoot apical meristems (SAMs) commonly exhibit low or no competence for transformation, the potent regeneration of this tissue merits further research. Especially, when shoot regeneration is recalcitrant using other tissues as explants, SAM probably is an excellent selection. In cockscomb plants, using SAMs from seedlings obtained from MS medium with 0.5 mg l(-1) 6-BA as explants, high frequency of transformation (approximate 20%) is obtained; whereas control SAMs performed poorly for transformation (approximate 3%). These SAMs are malformed in morphology compared to control SAMs. Further observation found that, in these SAMs, cell proliferation and/or TE formation are seen; which are not found in control SAMs. GUS assays indicated that GUS-positive blue spots at TE zones are obvious; whereas the case was contrary in control SAMs. All these data suggest that cell proliferation and/or TE formation might cause high effective transformation. This transformation system should facilitate the use of this species for studies on gene manipulation and expression. Therefore, we introduced 35S:ASL11-GFP to cockscomb via Agrobacterium tumefaciens. ASYMMETRIC LEAVES2-LIKE11 (ASL11) gene of Arabidopsis is a member of the ASYMMETRIC LEAVES2 (AS2)/LATERAL ORGAN BOUNDARIES (LOB) domain gene family, and its function is largely unclear. By confocal laser scanning microscopy, we found that in most over 35S:ASL11-GFP cockscomb plants, ASL11-GFP fusion protein was in discrete nuclear location. These results indicate that the T-DNA contains within the construct inserted into the host chromosomes in an integral form, and also suggest that ASL11 might be a nuclear protein and function as a potential transcription factor. Moreover, SAMs of the over 35S:ASL11-GFP plants show needle-like patterns that lack organ primordial; suggesting ASL11 might be involved in sustaining indeterminate cell fate of SAMs. PMID:20306306

  14. XAANTAL2 (AGL14) Is an Important Component of the Complex Gene Regulatory Network that Underlies Arabidopsis Shoot Apical Meristem Transitions.

    PubMed

    Pérez-Ruiz, Rigoberto V; García-Ponce, Berenice; Marsch-Martínez, Nayelli; Ugartechea-Chirino, Yamel; Villajuana-Bonequi, Mitzi; de Folter, Stefan; Azpeitia, Eugenio; Dávila-Velderrain, José; Cruz-Sánchez, David; Garay-Arroyo, Adriana; Sánchez, María de la Paz; Estévez-Palmas, Juan M; Álvarez-Buylla, Elena R

    2015-05-01

    In Arabidopsis thaliana, multiple genes involved in shoot apical meristem (SAM) transitions have been characterized, but the mechanisms required for the dynamic attainment of vegetative, inflorescence, and floral meristem (VM, IM, FM) cell fates during SAM transitions are not well understood. Here we show that a MADS-box gene, XAANTAL2 (XAL2/AGL14), is necessary and sufficient to induce flowering, and its regulation is important in FM maintenance and determinacy. xal2 mutants are late flowering, particularly under short-day (SD) condition, while XAL2 overexpressing plants are early flowering, but their flowers have vegetative traits. Interestingly, inflorescences of the latter plants have higher expression levels of LFY, AP1, and TFL1 than wild-type plants. In addition we found that XAL2 is able to bind the TFL1 regulatory regions. On the other hand, the basipetal carpels of the 35S::XAL2 lines lose determinacy and maintain high levels of WUS expression under SD condition. To provide a mechanistic explanation for the complex roles of XAL2 in SAM transitions and the apparently paradoxical phenotypes of XAL2 and other MADS-box (SOC1, AGL24) overexpressors, we conducted dynamic gene regulatory network (GRN) and epigenetic landscape modeling. We uncovered a GRN module that underlies VM, IM, and FM gene configurations and transition patterns in wild-type plants as well as loss and gain of function lines characterized here and previously. Our approach thus provides a novel mechanistic framework for understanding the complex basis of SAM development. PMID:25636918

  15. Genetic and phenotypic analysis of shoot apical and floral meristem development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The shoot apical and floral meristems (SAM and FM, respectively) of Arabidopsis thaliana contain reservoirs of self-renewing stem cells that function as sources of progenitor cells for organ formation during development. The primary SAM produces all of the aerial structures of the adult plant, where...

  16. Giant Shoot Apical Meristems in Cacti Have Ordinary Leaf Primordia but Altered Phyllotaxy and Shoot Diameter

    PubMed Central

    MAUSETH, JAMES D.

    2004-01-01

    • Background and Aims Shoot apical meristems (SAMs) in most seed plants are quite uniform in size and zonation, and molecular genetic studies of Arabidopsis and other model plants are revealing details of SAM morphogenesis. Some cacti have SAMs much larger than those of A. thaliana and other seed plants. This study examined how SAM size affects leaf primordium (LP) size, phyllotaxy and shoot diameter. • Methods. Apices from 183 species of cacti were fixed, microtomed and studied by light microscopy. • Key Results Cactus SAM diameter varies from 93 to 2565 µm, the latter being 36 times wider than SAMs of A. thaliana and having a volume 45 thousand times larger. Phyllotaxy ranges from distichous to having 56 rows of leaves and is not restricted to Fibonacci numbers. Leaf primordium diameter ranges from 44 to 402 µm, each encompassing many more cells than do LP of other plants. Species with high phyllotaxy have smaller LP, although the correlation is weak. There is almost no correlation between SAM diameter and LP size, but SAM diameter is strongly correlated with shoot diameter, with shoots being about 189·5 times wider than SAMs. • Conclusions Presumably, genes such as SHOOT‐MERISTEMLESS, WUSCHEL and CLAVATA must control much larger volumes of SAM tissue in cacti than they do in A. thaliana, and genes such as PERIANTHIA might establish much more extensive fields of inhibition around LP. These giant SAMs should make it possible to more accurately map gene expression patterns relative to SAM zonation and LP sites. PMID:15145794

  17. Normal and Abnormal Development in the Arabidopsis Vegetative Shoot Apex.

    PubMed Central

    Medford, JI; Behringer, FJ; Callos, JD; Feldmann, KA

    1992-01-01

    Vegetative development in the Arabidopsis shoot apex follows both sequential and repetitive steps. Early in development, the young vegetative meristem is flat and has a rectangular shape with bilateral symmetry. The first pair of leaf primordia is radially symmetrical and is initiated on opposite sides of the meristem. As development proceeds, the meristem changes first to a bilaterally symmetrical trapezoid and then to a radially symmetrical dome. Vegetative development from the domed meristem continues as leaves are initiated in a repetitive manner. Abnormal development of the vegetative shoot apex is described for a number of mutants. The mutants we describe fall into at least three classes: (1) lesions in the shoot apex that do not show an apparent alteration in the shoot apical meristem, (2) lesions in the apical meristem that also (directly or indirectly) alter leaf primordia, and (3) lesions in the apical meristem that alter meristem size and leaf number but not leaf morphology. These mutations provide tools both to genetically analyze vegetative development of the shoot apex and to learn how vegetative development influences floral development. PMID:12297656

  18. Morphogenesis in Plants: Modeling the Shoot Apical Meristem, and Possible Applications

    NASA Technical Reports Server (NTRS)

    Mjolsness, Eric; Gor, Victoria; Meyerowitz, Elliot; Mann, Tobias

    1998-01-01

    A key determinant of overall morphogenesis in flowering plants such as Arabidopsis thaliana is the shoot apical meristem (growing tip of a shoot). Gene regulation networks can be used to model this system. We exhibit a very preliminary two-dimensional model including gene regulation and intercellular signaling, but omitting cell division and dynamical geometry. The model can be trained to have three stable regions of gene expression corresponding to the central zone, peripheral zone, and rib meristem. We also discuss a space-engineering motivation for studying and controlling the morphogenesis of plants using such computational models.

  19. The Mobile bypass Signal Arrests Shoot Growth by Disrupting Shoot Apical Meristem Maintenance, Cytokinin Signaling, and WUS Transcription Factor Expression.

    PubMed

    Lee, Dong-Keun; Parrott, David L; Adhikari, Emma; Fraser, Nisa; Sieburth, Leslie E

    2016-07-01

    The bypass1 (bps1) mutant of Arabidopsis (Arabidopsis thaliana) produces a root-sourced compound (the bps signal) that moves to the shoot and is sufficient to arrest growth of a wild-type shoot; however, the mechanism of growth arrest is not understood. Here, we show that the earliest shoot defect arises during germination and is a failure of bps1 mutants to maintain their shoot apical meristem (SAM). This finding suggested that the bps signal might affect expression or function of SAM regulatory genes, and we found WUSCHEL (WUS) expression to be repressed in bps1 mutants. Repression appears to arise from the mobile bps signal, as the bps1 root was sufficient to rapidly down-regulate WUS expression in wild-type shoots. Normally, WUS is regulated by a balance between positive regulation by cytokinin (CK) and negative regulation by CLAVATA (CLV). In bps1, repression of WUS was independent of CLV, and, instead, the bps signal down-regulates CK responses. Cytokinin treatment of bps1 mutants restored both WUS expression and activity, but only in the rib meristem. How the bps signal down-regulates CK remains unknown, though the bps signal was sufficient to repress expression of one CK receptor (AHK4) and one response regulator (AHP6). Together, these data suggest that the bps signal pathway has the potential for long-distance regulation through modification of CK signaling and altering gene expression. PMID:27208247

  20. Repression of apical homeobox genes is required for embryonic root development in Arabidopsis.

    PubMed

    Grigg, Stephen P; Galinha, Carla; Kornet, Noortje; Canales, Claudia; Scheres, Ben; Tsiantis, Miltos

    2009-09-15

    Development of seed plant embryos is polarized along the apical-basal axis. This polarization occurs in the absence of cell migration and culminates in the establishment of two distinct pluripotent cell populations: the shoot apical meristem (SAM) and root meristem (RM), which postembryonically give rise to the entire shoot and root systems of the plant. The acquisition of genetic pathways that delimit root from shoot during embryogenesis must have played a pivotal role during land plant evolution because roots evolved after shoots in ancestral vascular plants and may be shoot-derived organs. However, such pathways are very poorly understood. Here we show that RM establishment in the model plant Arabidopsis thaliana requires apical confinement of the Class III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) proteins PHABULOSA (PHB) and PHAVOLUTA (PHV), which direct both SAM development and shoot lateral organ polarity. Failure to restrict PHB and PHV expression apically via a microRNA-dependent pathway prevents correct elaboration of the embryonic root development program and results in embryo lethality. As such, repression of a fundamental shoot development pathway is essential for correct root development. Additionally, our data suggest that a single patterning process, based on HD-ZIP III repression, mediates both apical-basal and radial polarity in the embryo and lateral organ polarity in the shoot. PMID:19646874

  1. Chapter Four - Shoot apical meristem form and function. In:

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The shoot apical meristem (SAM) generates above-ground aerial organs throughout the lifespan of higher plants. In order to fulfill this function, the meristem must maintain a balance between the self-renewal of a reservoir of central stem cells and organ initiation from peripheral cells. The activit...

  2. Transformation of shoots into roots in Arabidopsis embryos mutant at the TOPLESS locus.

    PubMed

    Long, Jeff A; Woody, Scott; Poethig, Scott; Meyerowitz, Elliot M; Barton, M Kathryn

    2002-06-01

    We describe a novel phenotype in Arabidopsis embryos homozygous for the temperature-sensitive topless-1 mutation. This mutation causes the transformation of the shoot pole into a root. Developing topless embryos fail to express markers for the shoot apical meristem (SHOOT MERISTEMLESS and UNUSUAL FLORAL ORGANS) and the hypocotyl (KNAT1). By contrast, the pattern of expression of root markers is either duplicated (LENNY, J1092) or expanded (SCARECROW). Shifts of developing topless embryos between permissive and restrictive temperatures show that apical fates (cotyledons plus shoot apical meristem) can be transformed to basal fates (root) as late as transition stage. As the apical pole of transition stage embryos shows both morphological and molecular characteristics of shoot development, this demonstrates that the topless 1 mutation is capable of causing structures specified as shoot to be respecified as root. Finally, our experiments fail to show a clear link between auxin signal transduction and topless-1 mutant activity: the development of the apical root in topless mutant individuals is not dependent on the activity of the predicted auxin response factor MONOPTEROS nor is the expression of DR5, a proposed 'auxin maximum reporter', expanded in the apical domain of topless embryos. PMID:12050130

  3. HANABA TARANU regulates the shoot apical meristem and leaf development in cucumber (Cucumis sativus L.)

    PubMed Central

    Ding, Lian; Yan, Shuangshuang; Jiang, Li; Liu, Meiling; Zhang, Juan; Zhao, Jianyu; Zhao, Wensheng; Han, Ying-yan; Wang, Qian; Zhang, Xiaolan

    2015-01-01

    The shoot apical meristem (SAM) is essential for continuous organogenesis in higher plants, while the leaf is the primary source organ and the leaf shape directly affects the efficiency of photosynthesis. HANABA TARANU (HAN) encodes a GATA3-type transcription factor that functions in floral organ development, SAM organization, and embryo development in Arabidopsis, but is involved in suppressing bract outgrowth and promoting branching in grass species. Here the function of the HAN homologue CsHAN1 was characterized in cucumber, an important vegetable with great agricultural and economic value. CsHAN1 is predominantly expressed at the junction of the SAM and the stem, and can partially rescue the han-2 floral organ phenotype in Arabidopsis. Overexpression and RNAi of CsHAN1 transgenic cucumber resulted in retarded growth early after embryogenesis and produced highly lobed leaves. Further, it was found that CsHAN1 may regulate SAM development through regulating the WUSCHEL (WUS) and SHOOT MERISTEMLESS (STM) pathways, and mediate leaf development through a complicated gene regulatory network in cucumber. PMID:26320238

  4. HANABA TARANU regulates the shoot apical meristem and leaf development in cucumber (Cucumis sativus L.).

    PubMed

    Ding, Lian; Yan, Shuangshuang; Jiang, Li; Liu, Meiling; Zhang, Juan; Zhao, Jianyu; Zhao, Wensheng; Han, Ying-Yan; Wang, Qian; Zhang, Xiaolan

    2015-12-01

    The shoot apical meristem (SAM) is essential for continuous organogenesis in higher plants, while the leaf is the primary source organ and the leaf shape directly affects the efficiency of photosynthesis. HANABA TARANU (HAN) encodes a GATA3-type transcription factor that functions in floral organ development, SAM organization, and embryo development in Arabidopsis, but is involved in suppressing bract outgrowth and promoting branching in grass species. Here the function of the HAN homologue CsHAN1 was characterized in cucumber, an important vegetable with great agricultural and economic value. CsHAN1 is predominantly expressed at the junction of the SAM and the stem, and can partially rescue the han-2 floral organ phenotype in Arabidopsis. Overexpression and RNAi of CsHAN1 transgenic cucumber resulted in retarded growth early after embryogenesis and produced highly lobed leaves. Further, it was found that CsHAN1 may regulate SAM development through regulating the WUSCHEL (WUS) and SHOOT MERISTEMLESS (STM) pathways, and mediate leaf development through a complicated gene regulatory network in cucumber. PMID:26320238

  5. The Mobile bypass Signal Arrests Shoot Growth by Disrupting Shoot Apical Meristem Maintenance, Cytokinin Signaling, and WUS Transcription Factor Expression1[OPEN

    PubMed Central

    Parrott, David L.; Adhikari, Emma; Fraser, Nisa

    2016-01-01

    The bypass1 (bps1) mutant of Arabidopsis (Arabidopsis thaliana) produces a root-sourced compound (the bps signal) that moves to the shoot and is sufficient to arrest growth of a wild-type shoot; however, the mechanism of growth arrest is not understood. Here, we show that the earliest shoot defect arises during germination and is a failure of bps1 mutants to maintain their shoot apical meristem (SAM). This finding suggested that the bps signal might affect expression or function of SAM regulatory genes, and we found WUSCHEL (WUS) expression to be repressed in bps1 mutants. Repression appears to arise from the mobile bps signal, as the bps1 root was sufficient to rapidly down-regulate WUS expression in wild-type shoots. Normally, WUS is regulated by a balance between positive regulation by cytokinin (CK) and negative regulation by CLAVATA (CLV). In bps1, repression of WUS was independent of CLV, and, instead, the bps signal down-regulates CK responses. Cytokinin treatment of bps1 mutants restored both WUS expression and activity, but only in the rib meristem. How the bps signal down-regulates CK remains unknown, though the bps signal was sufficient to repress expression of one CK receptor (AHK4) and one response regulator (AHP6). Together, these data suggest that the bps signal pathway has the potential for long-distance regulation through modification of CK signaling and altering gene expression. PMID:27208247

  6. Mechanical stress contributes to the expression of the STM homeobox gene in Arabidopsis shoot meristems.

    PubMed

    Landrein, Benoît; Kiss, Annamaria; Sassi, Massimiliano; Chauvet, Aurélie; Das, Pradeep; Cortizo, Millan; Laufs, Patrick; Takeda, Seiji; Aida, Mitsuhiro; Traas, Jan; Vernoux, Teva; Boudaoud, Arezki; Hamant, Olivier

    2015-01-01

    The role of mechanical signals in cell identity determination remains poorly explored in tissues. Furthermore, because mechanical stress is widespread, mechanical signals are difficult to uncouple from biochemical-based transduction pathways. Here we focus on the homeobox gene SHOOT MERISTEMLESS (STM), a master regulator and marker of meristematic identity in Arabidopsis. We found that STM expression is quantitatively correlated to curvature in the saddle-shaped boundary domain of the shoot apical meristem. As tissue folding reflects the presence of mechanical stress, we test and demonstrate that STM expression is induced after micromechanical perturbations. We also show that STM expression in the boundary domain is required for organ separation. While STM expression correlates with auxin depletion in this domain, auxin distribution and STM expression can also be uncoupled. STM expression and boundary identity are thus strengthened through a synergy between auxin depletion and an auxin-independent mechanotransduction pathway at the shoot apical meristem. PMID:26623515

  7. Gibberellin-enhanced elongation of inverted Pharbitis nil shoot prevents the release of apical dominance

    NASA Technical Reports Server (NTRS)

    Prasad, T. K.; Cline, M. G.

    1987-01-01

    Ethylene evolution resulting from the gravity stress of shoot inversion appears to induce the release of apical dominance in Pharbitis nil (L.) by inhibiting elongation of the inverted shoot. It has been previously demonstrated that this shoot inversion release of apical dominance can be prevented by promoting elongation in the inverted shoot via interference with ethylene synthesis or action. In the present study it was shown that apical dominance release can also be prevented by promoting elongation of the inverted shoot via treatment with gibberellic acid (GA3). A synergistic effect was observed when AgNO3, the ethylene action inhibitor, was applied with GA3. Both GA3 and AgNO3 increased ethylene production in the inverted shoot. These results are consistent with the view that it is ethylene-induced inhibition of elongation and not any direct effect of ethylene per se which is responsible for the outgrowth of the highest lateral bud.

  8. The control of apical dominance: localization of the growth region of the Pharbitis nil shoot

    NASA Technical Reports Server (NTRS)

    Prasad, T. K.; Cline, M. G.

    1986-01-01

    The growing region of the upright Pharbitis nil shoot extends over a distance 13 cm basipetal to the shoot apex. When the shoot is inverted, ethylene production in this region is greatly enhanced whereas stem elongation is significantly inhibited. This growth region is ethylene-sensitive and the restriction of its growth by shoot inversion-induced ethylene may mediate the release of apical dominance.

  9. ERECTA Family Genes Regulate Auxin Transport in the Shoot Apical Meristem and Forming Leaf Primordia1[C][W][OPEN

    PubMed Central

    Chen, Ming-Kun; Wilson, Rebecca L.; Palme, Klaus; Ditengou, Franck Anicet; Shpak, Elena D.

    2013-01-01

    Leaves are produced postembryonically at the flanks of the shoot apical meristem. Their initiation is induced by a positive feedback loop between auxin and its transporter PIN-FORMED1 (PIN1). The expression and polarity of PIN1 in the shoot apical meristem is thought to be regulated primarily by auxin concentration and flow. The formation of an auxin maximum in the L1 layer of the meristem is the first sign of leaf initiation and is promptly followed by auxin flow into the inner tissues, formation of the midvein, and appearance of the primordium bulge. The ERECTA family genes (ERfs) encode leucine-rich repeat receptor-like kinases, and in Arabidopsis (Arabidopsis thaliana), this gene family consists of ERECTA (ER), ERECTA-LIKE1 (ERL1), and ERL2. Here, we show that ERfs regulate auxin transport during leaf initiation. The shoot apical meristem of the er erl1 erl2 triple mutant produces leaf primordia at a significantly reduced rate and with altered phyllotaxy. This phenotype is likely due to deficiencies in auxin transport in the shoot apex, as judged by altered expression of PIN1, the auxin reporter DR5rev::GFP, and the auxin-inducible genes MONOPTEROS, INDOLE-3-ACETIC ACID INDUCIBLE1 (IAA1), and IAA19. In er erl1 erl2, auxin presumably accumulates in the L1 layer of the meristem, unable to flow into the vasculature of a hypocotyl. Our data demonstrate that ERfs are essential for PIN1 expression in the forming midvein of future leaf primordia and in the vasculature of emerging leaves. PMID:23821653

  10. The Dynamics of Soybean Leaf and Shoot Apical Meristem Transcriptome Undergoing Floral Initiation Process

    PubMed Central

    Wong, Chui E.; Singh, Mohan B.; Bhalla, Prem L.

    2013-01-01

    Flowering process governs seed set and thus affects agricultural productivity. Soybean, a major legume crop, requires short-day photoperiod conditions for flowering. While leaf-derived signal(s) are essential for the photoperiod-induced floral initiation process at the shoot apical meristem, molecular events associated with early floral transition stages in either leaves or shoot apical meristems are not well understood. To provide novel insights into the molecular basis of floral initiation, RNA-Seq was used to characterize the soybean transcriptome of leaf and micro-dissected shoot apical meristem at different time points after short-day treatment. Shoot apical meristem expressed a higher number of transcripts in comparison to that of leaf highlighting greater diversity and abundance of transcripts expressed in the shoot apical meristem. A total of 2951 shoot apical meristem and 13,609 leaf sequences with significant profile changes during the time course examined were identified. Most changes in mRNA level occurred after 1short-day treatment. Transcripts involved in mediating responses to stimulus including hormones or in various metabolic processes represent the top enriched GO functional category for the SAM and leaf dataset, respectively. Transcripts associated with protein degradation were also significantly changing in leaf and SAM implicating their involvement in triggering the developmental switch. RNA-Seq analysis of shoot apical meristem and leaf from soybean undergoing floral transition reveal major reprogramming events in leaves and the SAM that point toward hormones gibberellins (GA) and cytokinin as key regulators in the production of systemic flowering signal(s) in leaves. These hormones may form part of the systemic signals in addition to the established florigen, FLOWERING LOCUS T (FT). Further, evidence is emerging that the conversion of shoot apical meristem to inflorescence meristem is linked with the interplay of auxin, cytokinin and GA

  11. Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices.

    PubMed

    Bennett, Tom; Hines, Geneviève; van Rongen, Martin; Waldie, Tanya; Sawchuk, Megan G; Scarpella, Enrico; Ljung, Karin; Leyser, Ottoline

    2016-04-01

    The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS. PMID:27119525

  12. Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices

    PubMed Central

    Bennett, Tom; Hines, Geneviève; van Rongen, Martin; Sawchuk, Megan G.; Scarpella, Enrico; Ljung, Karin

    2016-01-01

    The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS. PMID:27119525

  13. Microarray gene expression profiling of developmental transitions in Sitka spruce (Picea sitchensis) apical shoots.

    PubMed

    Friedmann, Michael; Ralph, Steven G; Aeschliman, Dana; Zhuang, Jun; Ritland, Kermit; Ellis, Brian E; Bohlmann, Joerg; Douglas, Carl J

    2007-01-01

    The apical shoot drives the yearly new stem growth of conifer trees, is the primary site for the establishment of chemical and physical defences, and is important in establishing subsequent perennial growth. This organ presents an interesting developmental system, with growth and development progressing from a meristematic tip through development of a primary vascular system, to a base with fully differentiated and lignified secondary xylem on the inside and bark tissue with constitutive defence structures such as resin, polyphenolic phloem parenchyma cells, and sclereids on the outside. A spruce (Picea spp.) microarray containing approximately 16.7K unique cDNAs was used to study transcript profiles that characterize the developmental transition in apical shoots of Sitka spruce (Picea sitchensis) from their vegetative tips to their woody bases. Along with genes involved in cell-wall modification and lignin biosynthesis, a number of differentially regulated genes encoding protein kinases and transcription factors with base-preferred expression patterns were identified, which could play roles in the formation of woody tissues inside the apical shoot, as well as in regulating other developmental transitions associated with organ maturation. Preferential expression of known conifer defence genes, genes encoding defence-related proteins, and genes encoding regulatory proteins was observed at the apical shoot tip and in the green bark tissues at the apical shoot base, suggesting a commitment to constitutive defence in the apical shoot that is co-ordinated with rapid development of secondary xylem. PMID:17220514

  14. Gene expression in arabidopsis shoot tips after liquid nitrogen exposure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arabidopsis thaliana shoot tips can be successfully cryopreserved using either Plant Vitrification Solution 2 (PVS2) or Plant Vitrification Solution 3 (PVS3) as the cryoprotectant. We used this model system to identify suites of genes that were either upregulated or downregulated as shoot tips recov...

  15. Inhibition of auxin movement from the shoot into the root inhibits lateral root development in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Reed, R. C.; Brady, S. R.; Muday, G. K.

    1998-01-01

    In roots two distinct polar movements of auxin have been reported that may control different developmental and growth events. To test the hypothesis that auxin derived from the shoot and transported toward the root controls lateral root development, the two polarities of auxin transport were uncoupled in Arabidopsis. Local application of the auxin-transport inhibitor naphthylphthalamic acid (NPA) at the root-shoot junction decreased the number and density of lateral roots and reduced the free indoleacetic acid (IAA) levels in the root and [3H]IAA transport into the root. Application of NPA to the basal half of or at several positions along the root only reduced lateral root density in regions that were in contact with NPA or in regions apical to the site of application. Lateral root development was restored by application of IAA apical to NPA application. Lateral root development in Arabidopsis roots was also inhibited by excision of the shoot or dark growth and this inhibition was reversible by IAA. Together, these results are consistent with auxin transport from the shoot into the root controlling lateral root development.

  16. Shoot inversion-induced ethylene in Pharbitis nil induces the release of apical dominance by restricting shoot elongation

    NASA Technical Reports Server (NTRS)

    Prasad, T. K.; Cline, M. G.

    1985-01-01

    Shoot inversion induces outgrowth of the highest lateral bud (HLB) adjacent to the bend in the stem in Pharbitis nil. In order to determine whether or not ethylene produced by shoot inversion plays a direct role in promoting or inhibiting bud outgrowth, comparisons were made of endogenous levels of ethylene in the HLB and HLB node of plants with and without inverted shoots. That no changes were found suggests that the control of apical dominance does not involve the direction action of ethylene. This conclusion is further supported by evidence that the direct application of ethylene inhibitors or ethrel to inactive or induced lateral buds has no significant effect on bud outgrowth. The hypothesis that ethylene evolved during shoot inversion indirectly promotes the outgrowth of the highest lateral bud (HLB) in restricting terminal bud (TB) growth is found to be supported by the following observations: (1) the restriction of TB growth appears to occur before the beginning of HLB outgrowth; (2) the treatment of the inverted portion of the shoot with AgNO3, an inhibitor of ethylene action, dramatically eliminates both the restriction of TB growth and the promotion of HLB outgrowth which usually accompany shoot inversion; and (3) the treatment of the upper shoot of an upright plant with ethrel mimics shoot inversion by retarding upper shoot growth and inducing outgrowth of the lateral bud basipetal to the treated region.

  17. Real-Time Lineage Analysis to Study Cell Division Orientation in the Arabidopsis Shoot Meristem.

    PubMed

    Tobin, Cory J; Meyerowitz, Elliot M

    2016-01-01

    Cells in the Arabidopsis shoot apical meristem are small and divide frequently throughout the life-time of the organism making them good candidates for studying the mechanisms of cell division in plants. But tracking these cell divisions requires multiple images to be taken of the same specimen over time which means the specimen must stay alive throughout the process. This chapter provides details on how to prepare plants for live imaging, keep them alive and growing through multiple time points, and how to process the data to extract cell boundary coordinates from three-dimensional images. PMID:26659961

  18. Comparative evaluation of total RNA extraction methods in Theobroma cacao using shoot apical meristems.

    PubMed

    Silva, D V; Branco, S M J; Holanda, I S A; Royaert, S; Motamayor, J C; Marelli, J P; Corrêa, R X

    2016-01-01

    Theobroma cacao is a species of great economic importance with its beans used for chocolate production. The tree has been a target of various molecular studies. It contains many polyphenols, which complicate the extraction of nucleic acids with the extraction protocols requiring a large amount of plant material. These issues, therefore, necessitate the optimization of the protocols. The aim of the present study was to evaluate different methods for extraction of total RNA from shoot apical meristems of T. cacao 'CCN 51' and to assess the influence of storage conditions for the meristems on the extraction. The study also aimed to identify the most efficient protocol for RNA extraction using a small amount of plant material. Four different protocols were evaluated for RNA extraction using one shoot apical meristem per sample. Among these protocols, one that was more efficient was then tested to extract RNA using four different numbers of shoot apical meristems, subjected to three different storage conditions. The best protocol was tested for cDNA amplification using reverse transcription-polymerase chain reaction; the cDNA quality was determined to be satisfactory for molecular analyses. The study revealed that with the best RNA extraction protocol, one shoot apical meristem was sufficient for extraction of high-quality total RNA. The results obtained might enable advances in genetic analyses and molecular studies using reduced amount of plant material. PMID:26985935

  19. Responses of metabolites in soybean shoot apices to changing atmospheric carbon dioxide concentrations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean seedlings were grown in controlled environment chambers with chamber air CO2 partial pressures of 38 (ambient) and 72 (elevated) Pa. Samples were collected 21 to 24 days after sowing by harvesting five or six apices from the main shoot and from lateral branches on a single plant. Metabolit...

  20. Mechanical stress contributes to the expression of the STM homeobox gene in Arabidopsis shoot meristems

    PubMed Central

    Landrein, Benoît; Kiss, Annamaria; Sassi, Massimiliano; Chauvet, Aurélie; Das, Pradeep; Cortizo, Millan; Laufs, Patrick; Takeda, Seiji; Aida, Mitsuhiro; Traas, Jan; Vernoux, Teva; Boudaoud, Arezki; Hamant, Olivier

    2015-01-01

    The role of mechanical signals in cell identity determination remains poorly explored in tissues. Furthermore, because mechanical stress is widespread, mechanical signals are difficult to uncouple from biochemical-based transduction pathways. Here we focus on the homeobox gene SHOOT MERISTEMLESS (STM), a master regulator and marker of meristematic identity in Arabidopsis. We found that STM expression is quantitatively correlated to curvature in the saddle-shaped boundary domain of the shoot apical meristem. As tissue folding reflects the presence of mechanical stress, we test and demonstrate that STM expression is induced after micromechanical perturbations. We also show that STM expression in the boundary domain is required for organ separation. While STM expression correlates with auxin depletion in this domain, auxin distribution and STM expression can also be uncoupled. STM expression and boundary identity are thus strengthened through a synergy between auxin depletion and an auxin-independent mechanotransduction pathway at the shoot apical meristem. DOI: http://dx.doi.org/10.7554/eLife.07811.001 PMID:26623515

  1. Hormonally controlled expression of the Arabidopsis MAX4 shoot branching regulatory gene.

    PubMed

    Bainbridge, Katherine; Sorefan, Karim; Ward, Sally; Leyser, Ottoline

    2005-11-01

    The Arabidopsis MORE AXILLARY BRANCHING 4 (MAX4) gene is required for the production of a long-range, graft-transmissible signal that inhibits shoot branching. Buds of max4 mutant plants are resistant to the inhibitory effects of apically applied auxin, indicating that MAX4 is required for auxin-mediated bud inhibition. The RAMOSUS 1 (RMS1) and DECREASED APICAL DOMINANCE 1 (DAD1) genes of pea and petunia, respectively, are orthologous to MAX4 and function in a similar way. Here we show that, despite the similarities between these three genes, there are significant differences in the regulation of their expression. RMS1 is known to be upregulated by auxin in the shoot, suggesting a straightforward link between the RMS1-dependent branch-inhibiting signal and auxin, whereas we find that MAX4 is only upregulated by auxin in the root and hypocotyl, and this is not required for the inhibition of shoot branching. Furthermore, both RMS1 and DAD1 are subject to feedback regulation, for which there is no evidence for MAX4. Instead, overexpression studies and reciprocal grafting experiments demonstrate that the most functionally significant point of interaction between auxin and MAX4 is post-transcriptional and indeed post-synthesis of the MAX4-dependent graft-transmissible signal. PMID:16262707

  2. Ready, aim, shoot: stem cell regulation of the shoot apical meristem.

    PubMed

    Soyars, Cara L; James, Sean R; Nimchuk, Zachary L

    2016-02-01

    Plant shoot meristems contain stem cells that are continuously renewed to replenish cells that exit and differentiate during lateral organ formation. Complex cell-to-cell signaling systems balance division and differentiation. These center on ligand-receptor networks, hormone pathways, and transcriptional regulators that function in an integrated manner. In this review, we aim to highlight new findings in shoot stem cell regulation across species. PMID:26803586

  3. Genome-wide analyses for dissecting gene regulatory networks in the shoot apical meristem.

    PubMed

    Bustamante, Mariana; Matus, José Tomás; Riechmann, José Luis

    2016-04-01

    Shoot apical meristem activity is controlled by complex regulatory networks in which components such as transcription factors, miRNAs, small peptides, hormones, enzymes and epigenetic marks all participate. Many key genes that determine the inherent characteristics of the shoot apical meristem have been identified through genetic approaches. Recent advances in genome-wide studies generating extensive transcriptomic and DNA-binding datasets have increased our understanding of the interactions within the regulatory networks that control the activity of the meristem, identifying new regulators and uncovering connections between previously unlinked network components. In this review, we focus on recent studies that illustrate the contribution of whole genome analyses to understand meristem function. PMID:26956505

  4. Hormonal Control of Parthenocarpic Ovary Growth by the Apical Shoot in Pea1

    PubMed Central

    Rodrigo, María J.; García-Martínez, José L.

    1998-01-01

    The role of the apical shoot as a source of inhibitors preventing fruit growth in the absence of a stimulus (e.g. pollination or application of gibberellic acid) has been investigated in pea (Pisum sativum L.). Plant decapitation stimulated parthenocarpic growth, even in derooted plants, and this effect was counteracted by the application of indole acetic acid (IAA) or abscisic acid (ABA) in agar blocks to the severed stump. The treatment of unpollinated ovaries with gibberellic acid blocked the effect of IAA or ABA applied to the stump. [3H]IAA and [3H]ABA applied to the stump were transported basipetally, and [3H]ABA but not [3H]IAA was also detected in unpollinated ovaries. The concentration of ABA in unpollinated ovaries increased significantly in the absence of a promotive stimulus. The application of IAA to the stump enhanced by 2- to 5-fold the concentration of ABA in the inhibited ovary, whereas the inhibition of IAA transport from the apical shoot by triiodobenzoic acid decreased the ovary content of ABA (to approximately one-half). Triiodobenzoic acid alone, however, was unable to stimulate ovary growth. Thus, in addition to removing IAA transport from the apical shoot, the accumulation of a promotive factor is also necessary to induce parthenocarpic growth in decapitated plants. PMID:9490755

  5. Hormonal Control of Parthenocarpic Ovary Growth by the Apical Shoot in Pea

    PubMed

    Rodrigo; García-Martínez

    1998-02-01

    The role of the apical shoot as a source of inhibitors preventing fruit growth in the absence of a stimulus (e.g. pollination or application of gibberellic acid) has been investigated in pea (Pisum sativum L.). Plant decapitation stimulated parthenocarpic growth, even in derooted plants, and this effect was counteracted by the application of indole acetic acid (IAA) or abscisic acid (ABA) in agar blocks to the severed stump. The treatment of unpollinated ovaries with gibberellic acid blocked the effect of IAA or ABA applied to the stump. [3H]IAA and [3H]ABA applied to the stump were transported basipetally, and [3H]ABA but not [3H]IAA was also detected in unpollinated ovaries. The concentration of ABA in unpollinated ovaries increased significantly in the absence of a promotive stimulus. The application of IAA to the stump enhanced by 2- to 5-fold the concentration of ABA in the inhibited ovary, whereas the inhibition of IAA transport from the apical shoot by triiodobenzoic acid decreased the ovary content of ABA (to approximately one-half). Triiodobenzoic acid alone, however, was unable to stimulate ovary growth. Thus, in addition to removing IAA transport from the apical shoot, the accumulation of a promotive factor is also necessary to induce parthenocarpic growth in decapitated plants. PMID:9490755

  6. Differentiating Arabidopsis Shoots from Leaves by Combined YABBY Activities[W][OA

    PubMed Central

    Sarojam, Rajani; Sappl, Pia G.; Goldshmidt, Alexander; Efroni, Idan; Floyd, Sandra K.; Eshed, Yuval; Bowman, John L.

    2010-01-01

    In seed plants, leaves are born on radial shoots, but unlike shoots, they are determinate dorsiventral organs made of flat lamina. YABBY genes are found only in seed plants and in all cases studied are expressed primarily in lateral organs and in a polar manner. Despite their simple expression, Arabidopsis thaliana plants lacking all YABBY gene activities have a wide range of morphological defects in all lateral organs as well as the shoot apical meristem (SAM). Here, we show that leaves lacking all YABBY activities are initiated as dorsiventral appendages but fail to properly activate lamina programs. In particular, the activation of most CINCINNATA-class TCP genes does not commence, SAM-specific programs are reactivated, and a marginal leaf domain is not established. Altered distribution of auxin signaling and the auxin efflux carrier PIN1, highly reduced venation, initiation of multiple cotyledons, and gradual loss of the SAM accompany these defects. We suggest that YABBY functions were recruited to mold modified shoot systems into flat plant appendages by translating organ polarity into lamina-specific programs that include marginal auxin flow and activation of a maturation schedule directing determinate growth. PMID:20628155

  7. The role of gravity in apical dominance: effects of clinostating on shoot inversion-induced ethylene production, shoot elongation and lateral bud growth

    NASA Technical Reports Server (NTRS)

    Prasad, T. K.; Cline, M. G.

    1987-01-01

    Shoot inversion-induced release of apical dominance in Pharbitis nil is inhibited by rotating the plant at 0.42 revolutions per minute in a vertical plane perpendicular to the axis of rotation of a horizontal clinostat. Clinostating prevented lateral bud outgrowth, apparently by negating the restriction of the shoot elongation via reduction of ethylene production in the inverted shoot. Radial stem expansion was also decreased. Data from experiments with intact tissue and isolated segments indicated that shoot-inversion stimulates ethylene production by increasing the activity of 1-aminocyclopropane-1-carboxylic acid synthase. The results support the hypothesis that shoot inversion-induced release of apical dominance in Pharbitis nil is due to gravity stress and is mediated by ethylene-induced retardation of the elongation of the inverted shoot.

  8. Inhibition of Auxin Movement from the Shoot into the Root Inhibits Lateral Root Development in Arabidopsis1

    PubMed Central

    Reed, Robyn C.; Brady, Shari R.; Muday, Gloria K.

    1998-01-01

    In roots two distinct polar movements of auxin have been reported that may control different developmental and growth events. To test the hypothesis that auxin derived from the shoot and transported toward the root controls lateral root development, the two polarities of auxin transport were uncoupled in Arabidopsis. Local application of the auxin-transport inhibitor naphthylphthalamic acid (NPA) at the root-shoot junction decreased the number and density of lateral roots and reduced the free indoleacetic acid (IAA) levels in the root and [3H]IAA transport into the root. Application of NPA to the basal half of or at several positions along the root only reduced lateral root density in regions that were in contact with NPA or in regions apical to the site of application. Lateral root development was restored by application of IAA apical to NPA application. Lateral root development in Arabidopsis roots was also inhibited by excision of the shoot or dark growth and this inhibition was reversible by IAA. Together, these results are consistent with auxin transport from the shoot into the root controlling lateral root development. PMID:9847111

  9. Mechanical perturbation-induced ethylene releases apical dominance in Pharbitis nil by restricting shoot growth

    NASA Technical Reports Server (NTRS)

    Prasad, T. K.; Cline, M. G.

    1985-01-01

    Mechanical perturbation (MP, rubbing) or internodes of Pharbitis nil shoots initiates release of lateral buds (LB) from apical dominance within 48 h. Evidence is presented which suggests that MP promotion of LB outgrowth is mediated by ethylene-induced restriction of main shoot growth. Ethylene production in the internodes is stimulated by MP within 2 h. Effects of MP are mimicked by treatments with 1-aminocyclopropane-1-carboxylic acid (ACC) and are negated by the inhibitors of ethylene production or action, aminoethoxy vinylglycine (AVG) and AgNO3. The fact that effects of MP, ACC, and ethylene inhibitors are observed to occur on main shoot growth at least 24 h before they are observed to occur on LB growth suggests a possible cause and effect relationship. MP also causes an increase in internode diameter. MP stimulation of ethylene production appears to be mediated by ACC synthase. The results of this study and our previous studies suggest that apical dominance may be released by any mechanism which induces ethylene restriction of main shoot growth.

  10. Gene expression in response to cryoprotectant and liquid nitrogen exposure in Arabidopsis shoot tips

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arabidopsis thaliana serves as an ideal model system to study cryopreservation at the molecular level. We have developed reliable cryopreservation methods for Arabidopsis shoot tips using Plant Vitrification Solution 2, Plant Vitrification Solution 3 and polyethylene glycol-glucose-dimethylsulfoxid...

  11. Manipulation of hemoglobin expression affects Arabidopsis shoot organogenesis.

    PubMed

    Wang, Yaping; Elhiti, Mohamed; Hebelstrup, Kim H; Hill, Robert D; Stasolla, Claudio

    2011-10-01

    Over the past few years non-symbiotic plant hemoglobins have been described in a variety of plant species where they fulfill several functions ranging from detoxification processes to basic aspects of plant growth and post-embryonic development. To date no information is available on the role of hemoglobins during in vitro morphogenesis. Shoot organogenesis was induced in Arabidopsis lines constitutively expressing class 1, 2 and 3 hemoglobins (GLB1, 2 and 3) and lines in which the respective genes were either downregulated by RNAi (GLB1) or knocked out (GLB2 and GLB3). The process was executed by culturing root explants on an initial auxin-rich callus induction medium (CIM) followed by a transfer onto a cytokinin-containing shoot induction medium (SIM). While the repression of GLB2 inhibited organogenesis the over-expression of GLB1 or GLB2 enhanced the number of shoots produced in culture, and altered the transcript levels of genes participating in cytokinin perception and signalling. The up-regulation of GLB1 or GLB2 activated CKI1 and AHK3, genes encoding cytokinin receptors and affected the transcript levels of cytokinin responsive regulators (ARRs). The expression of Type-A ARRs (ARR4, 5, 7, 15, and 16), feed-back repressors of the cytokinin pathway, was repressed in both hemoglobin over-expressors whereas that of several Type-B ARRs (ARR2, 12, and 13), transcription activators of cytokinin-responsive genes, was induced. Such changes enhanced the sensitivity of the root explants to cytokinin allowing the 35S::GLB1 and 35S::GLB2 lines to produce shoots at low cytokinin concentrations which did not promote organogenesis in the WT line. These results show that manipulation of hemoglobin can modify shoot organogenesis in Arabidopsis and possibly in those systems partially or completely unresponsive to applications of exogenous cytokinins. PMID:21741261

  12. Arabidopsis HD-Zip II transcription factors control apical embryo development and meristem function.

    PubMed

    Turchi, Luana; Carabelli, Monica; Ruzza, Valentino; Possenti, Marco; Sassi, Massimiliano; Peñalosa, Andrés; Sessa, Giovanna; Salvi, Sergio; Forte, Valentina; Morelli, Giorgio; Ruberti, Ida

    2013-05-01

    The Arabidopsis genome encodes ten Homeodomain-Leucine zipper (HD-Zip) II proteins. ARABIDOPSIS THALIANA HOMEOBOX 2 (ATHB2), HOMEOBOX ARABIDOPSIS THALIANA 1 (HAT1), HAT2, HAT3 and ATHB4 are regulated by changes in the red/far red light ratio that induce shade avoidance in most of the angiosperms. Here, we show that progressive loss of HAT3, ATHB4 and ATHB2 activity causes developmental defects from embryogenesis onwards in white light. Cotyledon development and number are altered in hat3 athb4 embryos, and these defects correlate with changes in auxin distribution and response. athb2 gain-of-function mutation and ATHB2 expression driven by its promoter in hat3 athb4 result in significant attenuation of phenotypes, thus demonstrating that ATHB2 is functionally redundant to HAT3 and ATHB4. In analogy to loss-of-function mutations in HD-Zip III genes, loss of HAT3 and ATHB4 results in organ polarity defects, whereas triple hat3 athb4 athb2 mutants develop one or two radialized cotyledons and lack an active shoot apical meristem (SAM). Consistent with overlapping expression pattern of HD-Zip II and HD-Zip III gene family members, bilateral symmetry and SAM defects are enhanced when hat3 athb4 is combined with mutations in PHABULOSA (PHB), PHAVOLUTA (PHV) or REVOLUTA (REV). Finally, we show that ATHB2 is part of a complex regulatory circuit directly involving both HD-Zip II and HD-Zip III proteins. Taken together, our study provides evidence that a genetic system consisting of HD-Zip II and HD-Zip III genes cooperates in establishing bilateral symmetry and patterning along the adaxial-abaxial axis in the embryo as well as in controlling SAM activity. PMID:23578926

  13. Influence of arbuscular mycorrhizae and phosphate fertilization on shoot apical growth of micropropagated apple and plum rootstocks.

    PubMed

    Fortuna, P; Citernesi, A S; Morini, S; Vitagliano, C; Giovannetti, M

    1996-09-01

    We studied the effects of phosphate fertilization and inoculation with the arbuscular mycorrhizal fungi Glomus mosseae (Nicol. and Gerd.) Gerdmann and Trappe, Glomus intraradices Schenck and Smith or Glomus viscosum Nicolson on shoot apical growth of plantlets that had been micropropagated from MM 106 apple (Malus pumila L.) and Mr.S. 2/5 plum (Prunus cerasifera Ehrh.) rootstocks. Unfertilized and non-mycorrhizal plantlets showed no apical growth during the post in vitro acclimation phase, whereas P fertilization induced early resumption of shoot apical growth. Growth enhancement and percentage of actively growing apices of mycorrhizal-inoculated plantlets were comparable to those obtained in plantlets fertilized with P. Furthermore, tissue P concentrations of mycorrhizal plantlets were similar to those of plantlets fertilized with P. We conclude that mycorrhizal inoculation can be used as a biotechnological tool to overcome blocked apical growth and to reduce chemical inputs, especially P inputs, to micropropagated fruit trees. PMID:14871682

  14. Mapping symplasmic fields at the shoot apical meristem using iontophoresis and membrane potential measurements.

    PubMed

    van der Schoot, Christiaan; Rinne, Päivi L H

    2015-01-01

    Microinjections of fluorescent dyes have revealed that the shoot apical meristem (SAM) is dynamically partitioned into symplasmic fields (SFs), implying that plasmodesmata (Pd) are held shut at specific locations in the proliferating cellular matrix. The SFs are integrated into a coherent morphogenetic unit by exchange of morphogens and transcription factors via gating Pd between adjacent SFs, and by ligand-receptor interactions that operate across the extracellular space. We describe a method for the real-time mapping of SF in the SAM by iontophoresis and membrane potential measurements. PMID:25287203

  15. Integration of light and metabolic signals for stem cell activation at the shoot apical meristem

    PubMed Central

    Pfeiffer, Anne; Janocha, Denis; Dong, Yihan; Medzihradszky, Anna; Schöne, Stefanie; Daum, Gabor; Suzaki, Takuya; Forner, Joachim; Langenecker, Tobias; Rempel, Eugen; Schmid, Markus; Wirtz, Markus; Hell, Rüdiger; Lohmann, Jan U

    2016-01-01

    A major feature of embryogenesis is the specification of stem cell systems, but in contrast to the situation in most animals, plant stem cells remain quiescent until the postembryonic phase of development. Here, we dissect how light and metabolic signals are integrated to overcome stem cell dormancy at the shoot apical meristem. We show on the one hand that light is able to activate expression of the stem cell inducer WUSCHEL independently of photosynthesis and that this likely involves inter-regional cytokinin signaling. Metabolic signals, on the other hand, are transduced to the meristem through activation of the TARGET OF RAPAMYCIN (TOR) kinase. Surprisingly, TOR is also required for light signal dependent stem cell activation. Thus, the TOR kinase acts as a central integrator of light and metabolic signals and a key regulator of stem cell activation at the shoot apex. DOI: http://dx.doi.org/10.7554/eLife.17023.001 PMID:27400267

  16. Integration of light and metabolic signals for stem cell activation at the shoot apical meristem.

    PubMed

    Pfeiffer, Anne; Janocha, Denis; Dong, Yihan; Medzihradszky, Anna; Schöne, Stefanie; Daum, Gabor; Suzaki, Takuya; Forner, Joachim; Langenecker, Tobias; Rempel, Eugen; Schmid, Markus; Wirtz, Markus; Hell, Rüdiger; Lohmann, Jan U

    2016-01-01

    A major feature of embryogenesis is the specification of stem cell systems, but in contrast to the situation in most animals, plant stem cells remain quiescent until the postembryonic phase of development. Here, we dissect how light and metabolic signals are integrated to overcome stem cell dormancy at the shoot apical meristem. We show on the one hand that light is able to activate expression of the stem cell inducer WUSCHEL independently of photosynthesis and that this likely involves inter-regional cytokinin signaling. Metabolic signals, on the other hand, are transduced to the meristem through activation of the TARGET OF RAPAMYCIN (TOR) kinase. Surprisingly, TOR is also required for light signal dependent stem cell activation. Thus, the TOR kinase acts as a central integrator of light and metabolic signals and a key regulator of stem cell activation at the shoot apex. PMID:27400267

  17. The cytokinin response factors modulate root and shoot growth and promote leaf senescence in Arabidopsis.

    PubMed

    Raines, Tracy; Shanks, Carly; Cheng, Chia-Yi; McPherson, Duncan; Argueso, Cristiana T; Kim, Hyo J; Franco-Zorrilla, José M; López-Vidriero, Irene; Solano, Roberto; Vaňková, Radomíra; Schaller, G Eric; Kieber, Joseph J

    2016-01-01

    The cytokinin response factors (CRFs) are a group of related AP2/ERF transcription factors that are transcriptionally induced by cytokinin. Here we explore the role of the CRFs in Arabidopsis thaliana growth and development by analyzing lines with decreased and increased CRF function. While single crf mutations have no appreciable phenotypes, disruption of multiple CRFs results in larger rosettes, delayed leaf senescence, a smaller root apical meristem (RAM), reduced primary and lateral root growth, and, in etiolated seedlings, shorter hypocotyls. In contrast, overexpression of CRFs generally results in the opposite phenotypes. The crf1,2,5,6 quadruple mutant is embryo lethal, indicating that CRF function is essential for embryo development. Disruption of the CRFs results in partially insensitivity to cytokinin in a root elongation assay and affects the basal expression of a significant number of cytokinin-regulated genes, including the type-A ARRs, although it does not impair the cytokinin induction of the type-A ARRs. Genes encoding homeobox transcription factors are mis-expressed in the crf1,3,5,6 mutant, including STIMPY/WOX9 that is required for root and shoot apical meristem maintenance roots and which has previously been linked to cytokinin. These results indicate that the CRF transcription factors play important roles in multiple aspects of plant growth and development, in part through a complex interaction with cytokinin signaling. PMID:26662515

  18. Transcriptional, Posttranscriptional, and Posttranslational Regulation of SHOOT MERISTEMLESS Gene Expression in Arabidopsis Determines Gene Function in the Shoot Apex1[OPEN

    PubMed Central

    Aguilar-Martínez, José Antonio; Uchida, Naoyuki; Townsley, Brad; West, Donnelly Ann; Yanez, Andrea; Lynn, Nafeesa; Kimura, Seisuke

    2015-01-01

    The activity of SHOOT MERISTEMLESS (STM) is required for the functioning of the shoot apical meristem (SAM). STM is expressed in the SAM but is down-regulated at the site of leaf initiation. STM is also required for the formation of compound leaves. However, how the activity of STM is regulated at the transcriptional, posttranscriptional, and posttranslational levels is poorly understood. We previously found two conserved noncoding sequences in the promoters of STM-like genes across angiosperms, the K-box and the RB-box. Here, we characterize the function of the RB-box in Arabidopsis (Arabidopsis thaliana). The RB-box, along with the K-box, regulates the expression of STM in leaf sinuses, which are areas on the leaf blade with meristematic potential. The RB-box also contributes to restrict STM expression to the SAM. We identified FAR1-RELATED SEQUENCES-RELATED FACTOR1 (FRF1) as a binding factor to the RB-box region. FRF1 is an uncharacterized member of a subfamily of four truncated proteins related to the FAR1-RELATED SEQUENCES factors. Internal deletion analysis of the STM promoter identified a region required to repress the expression of STM in hypocotyls. Expression of STM in leaf primordia under the control of the JAGGED promoter produced plants with partially undifferentiated leaves. We further found that the ELK domain has a role in the posttranslational regulation of STM by affecting the nuclear localization of STM. PMID:25524441

  19. Invasion of shoot apical meristems by Chrysanthemum stunt viroid differs among Argyranthemum cultivars.

    PubMed

    Zhang, Zhibo; Lee, YeonKyeong; Spetz, Carl; Clarke, Jihong Liu; Wang, Qiaochun; Blystad, Dag-Ragnar

    2015-01-01

    Chrysanthemum stunt viroid (CSVd) is a damaging pathogen attacking Argyranthemum plants. Our study attempted to reveal distribution patterns of CSVd in shoot apical meristems (SAM) and to explore reasons for differential ability of CSVd to invade SAM of selected Argyranthemum cultivars. Symptom development was also observed on greenhouse-grown Argyranthemum plants. Viroid localization using in situ hybridization revealed that the ability of CSVd to invade SAM differed among cultivars. In diseased 'Yellow Empire' and 'Butterfly', CSVd was found in all tissues including the uppermost cell layers in the apical dome (AD) and the youngest leaf primordia 1 and 2. In diseased 'Border Dark Red' and 'Border Pink', CSVd was detected in the lower part of the AD and elder leaf primordia, leaving the upper part of the AD, and leaf primordia 1 and 2 free of viroid. Histological observations and transmission electron microscopy showed similar developmental patterns of vascular tissues and plasmodesmata (PD) in the SAM of 'Yellow Empire' and 'Border Dark Red', while immunolocalization studies revealed a major difference in the number of callose (β-1, 3-glucan) particles deposited at PD in SAM. A lower number of callose particles were found deposited at PD of SAM of 'Yellow Empire' than 'Border Dark Red'. This difference is most likely responsible for the differences in ability of CSVd to invade SAM among Argyranthemum cultivars. PMID:25763000

  20. Invasion of shoot apical meristems by Chrysanthemum stunt viroid differs among Argyranthemum cultivars

    PubMed Central

    Zhang, Zhibo; Lee, YeonKyeong; Spetz, Carl; Clarke, Jihong Liu; Wang, Qiaochun; Blystad, Dag-Ragnar

    2014-01-01

    Chrysanthemum stunt viroid (CSVd) is a damaging pathogen attacking Argyranthemum plants. Our study attempted to reveal distribution patterns of CSVd in shoot apical meristems (SAM) and to explore reasons for differential ability of CSVd to invade SAM of selected Argyranthemum cultivars. Symptom development was also observed on greenhouse-grown Argyranthemum plants. Viroid localization using in situ hybridization revealed that the ability of CSVd to invade SAM differed among cultivars. In diseased ‘Yellow Empire’ and ‘Butterfly’, CSVd was found in all tissues including the uppermost cell layers in the apical dome (AD) and the youngest leaf primordia 1 and 2. In diseased ‘Border Dark Red’ and ‘Border Pink’, CSVd was detected in the lower part of the AD and elder leaf primordia, leaving the upper part of the AD, and leaf primordia 1 and 2 free of viroid. Histological observations and transmission electron microscopy showed similar developmental patterns of vascular tissues and plasmodesmata (PD) in the SAM of ‘Yellow Empire’ and ‘Border Dark Red’, while immunolocalization studies revealed a major difference in the number of callose (β-1, 3-glucan) particles deposited at PD in SAM. A lower number of callose particles were found deposited at PD of SAM of ‘Yellow Empire’ than ‘Border Dark Red’. This difference is most likely responsible for the differences in ability of CSVd to invade SAM among Argyranthemum cultivars. PMID:25763000

  1. Arabidopsis FIM5 decorates apical actin filaments and regulates their organization in the pollen tube

    PubMed Central

    Zhang, Meng; Zhang, Ruihui; Qu, Xiaolu; Huang, Shanjin

    2016-01-01

    The actin cytoskeleton is increasingly recognized as a major regulator of pollen tube growth. Actin filaments have distinct distribution patterns and dynamic properties within different regions of the pollen tube. Apical actin filaments are highly dynamic and crucial for pollen tube growth. However, how apical actin filaments are generated and properly constructed remains an open question. Here we showed that Arabidopsis fimbrin5 (FIM5) decorates filamentous structures throughout the entire tube but is apically concentrated. Apical actin structures are disorganized to different degrees in the pollen tubes of fim5 loss-of-function mutants. Further observations suggest that apical actin structures are not constructed properly because apical actin filaments cannot be maintained at the cortex of fim5 pollen tubes. Actin filaments appeared to be more curved in fim5 pollen tubes and this was confirmed by measurements showing that the convolutedness and the rate of change of convolutedness of actin filaments was significantly increased in fim5 pollen tubes. This suggests that the rigidity of the actin filaments may be compromised in fim5 pollen tubes. Further, the apical cell wall composition is altered, implying that tip-directed vesicle trafficking events are impaired in fim5 pollen tubes. Thus, we found that FIM5 decorates apical actin filaments and regulates their organization in order to drive polarized pollen tube growth. PMID:27117336

  2. Mystery in genetics: PUB4 gives a clue to the complex mechanism of CLV signaling pathway in the shoot apical meristem.

    PubMed

    Kinoshita, Atsuko; Seo, Mitsunori; Kamiya, Yuji; Sawa, Shinichiro

    2015-01-01

    Postembryonic growth and development in higher plants are ultimately reliant on the activity of meristems, where the cells divide frequently to provide source cells for new organs and tissues while in part maintain their pluripotent nature as stem cells. The shoot apical meristem (SAM) is maintained throughout the life of plants and responsible for the development of all areal tissues. In Arabidopsis thaliana, the size of SAM is controlled by a peptide ligand, CLAVATA3 (CLV3). Previously, genetic studies have identified several genes that function downstream of CLV3, many of which, intriguingly, encode receptors. Recently we identified an E3 ubiquitin ligase, PLANT U-BOX 4 (PUB4), as a key regulatory component of root meristem maintenance that functions downstream of an exogenous synthetic CLV3 peptide. Here, we report an additional function of PUB4 in the SAM. PMID:25898239

  3. Interplay between miRNA regulation and mechanical stress for CUC gene expression at the shoot apical meristem

    PubMed Central

    Fal, Kateryna; Landrein, Benoit; Hamant, Olivier

    2016-01-01

    ABSTRACT The shoot apical meristem is the central organizer of plant aerial organogenesis. The molecular bases of its functions involve several cross-talks between transcription factors, hormones and microRNAs. We recently showed that the expression of the homeobox transcription factor STM is induced by mechanical perturbations, adding another layer of complexity to this regulation. Here we provide additional evidence that mechanical perturbations impact the promoter activity of CUC3, an important regulator of boundary formation at the shoot meristem. Interestingly, we did not detect such an effect for CUC1. This suggests that the robustness of expression patterns and developmental programs is controlled via a combined action of molecular factors as well as mechanical cues in the shoot apical meristem. PMID:26653277

  4. Interplay between miRNA regulation and mechanical stress for CUC gene expression at the shoot apical meristem.

    PubMed

    Fal, Kateryna; Landrein, Benoit; Hamant, Olivier

    2016-03-01

    The shoot apical meristem is the central organizer of plant aerial organogenesis. The molecular bases of its functions involve several cross-talks between transcription factors, hormones and microRNAs. We recently showed that the expression of the homeobox transcription factor STM is induced by mechanical perturbations, adding another layer of complexity to this regulation. Here we provide additional evidence that mechanical perturbations impact the promoter activity of CUC3, an important regulator of boundary formation at the shoot meristem. Interestingly, we did not detect such an effect for CUC1. This suggests that the robustness of expression patterns and developmental programs is controlled via a combined action of molecular factors as well as mechanical cues in the shoot apical meristem. PMID:26653277

  5. Transcriptome profiling of low temperature-treated cassava apical shoots showed dynamic responses of tropical plant to cold stress

    PubMed Central

    2012-01-01

    Background Cassava is an important tropical root crop adapted to a wide range of environmental stimuli such as drought and acid soils. Nevertheless, it is an extremely cold-sensitive tropical species. Thus far, there is limited information about gene regulation and signalling pathways related to the cold stress response in cassava. The development of microarray technology has accelerated the study of global transcription profiling under certain conditions. Results A 60-mer oligonucleotide microarray representing 20,840 genes was used to perform transcriptome profiling in apical shoots of cassava subjected to cold at 7°C for 0, 4 and 9 h. A total of 508 transcripts were identified as early cold-responsive genes in which 319 sequences had functional descriptions when aligned with Arabidopsis proteins. Gene ontology annotation analysis identified many cold-relevant categories, including 'Response to abiotic and biotic stimulus', 'Response to stress', 'Transcription factor activity', and 'Chloroplast'. Various stress-associated genes with a wide range of biological functions were found, such as signal transduction components (e.g., MAP kinase 4), transcription factors (TFs, e.g., RAP2.11), and reactive oxygen species (ROS) scavenging enzymes (e.g., catalase 2), as well as photosynthesis-related genes (e.g., PsaL). Seventeen major TF families including many well-studied members (e.g., AP2-EREBP) were also involved in the early response to cold stress. Meanwhile, KEGG pathway analysis uncovered many important pathways, such as 'Plant hormone signal transduction' and 'Starch and sucrose metabolism'. Furthermore, the expression changes of 32 genes under cold and other abiotic stress conditions were validated by real-time RT-PCR. Importantly, most of the tested stress-responsive genes were primarily expressed in mature leaves, stem cambia, and fibrous roots rather than apical buds and young leaves. As a response to cold stress in cassava, an increase in transcripts and

  6. Gene expression in response to cryoprotectant and liquid nitrogen exposure in Arabidopsis shoot tips

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arabidopsis thaliana is an ideal model system to study plant cryopreservation at the molecular level. We have developed reliable cryopreservation methods for Arabidopsis shoot tips using Plant Vitrification Solution 2 and Plant Vitrification Solution 3 (PVS3) cryoprotectants. We have made use of th...

  7. SUPPRESSOR OF APICAL DOMINANCE1 of Sporisorium reilianum Modulates Inflorescence Branching Architecture in Maize and Arabidopsis.

    PubMed

    Ghareeb, Hassan; Drechsler, Frank; Löfke, Christian; Teichmann, Thomas; Schirawski, Jan

    2015-12-01

    The biotrophic fungus Sporisorium reilianum causes head smut of maize (Zea mays) after systemic plant colonization. Symptoms include the formation of multiple female inflorescences at subapical nodes of the stalk because of loss of apical dominance. By deletion analysis of cluster 19-1, the largest genomic divergence cluster in S. reilianum, we identified a secreted fungal effector responsible for S. reilianum-induced loss of apical dominance, which we named SUPPRESSOR OF APICAL DOMINANCE1 (SAD1). SAD1 transcript levels were highly up-regulated during biotrophic fungal growth in all infected plant tissues. SAD1-green fluorescent protein fusion proteins expressed by recombinant S. reilianum localized to the extracellular hyphal space. Transgenic Arabidopsis (Arabidopsis thaliana)-expressing green fluorescent protein-SAD1 displayed an increased number of secondary rosette-leaf branches. This suggests that SAD1 manipulates inflorescence branching architecture in maize and Arabidopsis through a conserved pathway. Using a yeast (Saccharomyces cerevisiae) two-hybrid library of S. reilianum-infected maize tissues, we identified potential plant interaction partners that had a predicted function in ubiquitination, signaling, and nuclear processes. Presence of SAD1 led to an increase of the transcript levels of the auxin transporter PIN-FORMED1 in the root and a reduction of the branching regulator TEOSINTE BRANCHED1 in the stalk. This indicates a role of SAD1 in regulation of apical dominance by modulation of branching through increasing transcript levels of the auxin transporter PIN1 and derepression of bud outgrowth. PMID:26511912

  8. Global gene expression analysis of the shoot apical meristem of maize (Zea mays L.)

    PubMed Central

    Ohtsu, Kazuhiro; Smith, Marianne B; Emrich, Scott J; Borsuk, Lisa A; Zhou, Ruilian; Chen, Tianle; Zhang, Xiaolan; Timmermans, Marja C P; Beck, Jon; Buckner, Brent; Janick-Buckner, Diane; Nettleton, Dan; Scanlon, Michael J; Schnable, Patrick S

    2007-01-01

    All above-ground plant organs are derived from shoot apical meristems (SAMs). Global analyses of gene expression were conducted on maize (Zea mays L.) SAMs to identify genes preferentially expressed in the SAM. The SAMs were collected from 14-day-old B73 seedlings via laser capture microdissection (LCM). The RNA samples extracted from LCM-collected SAMs and from seedlings were hybridized to microarrays spotted with 37 660 maize cDNAs. Approximately 30% (10 816) of these cDNAs were prepared as part of this study from manually dissected B73 maize apices. Over 5000 expressed sequence tags (ESTs) (about 13% of the total) were differentially expressed (P<0.0001) between SAMs and seedlings. Of these, 2783 and 2248 ESTs were up- and down-regulated in the SAM, respectively. The expression in the SAM of several of the differentially expressed ESTs was validated via quantitative RT-PCR and/or in situ hybridization. The up-regulated ESTs included many regulatory genes including transcription factors, chromatin remodeling factors and components of the gene-silencing machinery, as well as about 900 genes with unknown functions. Surprisingly, transcripts that hybridized to 62 retrotransposon-related cDNAs were also substantially up-regulated in the SAM. Complementary DNAs derived from the LCM-collected SAMs were sequenced to identify additional genes that are expressed in the SAM. This generated around 550 000 ESTs (454-SAM ESTs) from two genotypes. Consistent with the microarray results, approximately 14% of the 454-SAM ESTs from B73 were retrotransposon-related. Possible roles of genes that are preferentially expressed in the SAM are discussed. PMID:17764504

  9. Studies of aberrant phyllotaxy1 Mutants of Maize Indicate Complex Interactions between Auxin and Cytokinin Signaling in the Shoot Apical Meristem1[W][OA

    PubMed Central

    Lee, Byeong-ha; Johnston, Robyn; Yang, Yan; Gallavotti, Andrea; Kojima, Mikiko; Travençolo, Bruno A.N.; Costa, Luciano da F.; Sakakibara, Hitoshi; Jackson, David

    2009-01-01

    One of the most fascinating aspects of plant morphology is the regular geometric arrangement of leaves and flowers, called phyllotaxy. The shoot apical meristem (SAM) determines these patterns, which vary depending on species and developmental stage. Auxin acts as an instructive signal in leaf initiation, and its transport has been implicated in phyllotaxy regulation in Arabidopsis (Arabidopsis thaliana). Altered phyllotactic patterns are observed in a maize (Zea mays) mutant, aberrant phyllotaxy1 (abph1, also known as abphyl1), and ABPH1 encodes a cytokinin-inducible type A response regulator, suggesting that cytokinin signals are also involved in the mechanism by which phyllotactic patterns are established. Therefore, we investigated the interaction between auxin and cytokinin signaling in phyllotaxy. Treatment of maize shoots with a polar auxin transport inhibitor, 1-naphthylphthalamic acid, strongly reduced ABPH1 expression, suggesting that auxin or its polar transport is required for ABPH1 expression. Immunolocalization of the PINFORMED1 (PIN1) polar auxin transporter revealed that PIN1 expression marks leaf primordia in maize, similarly to Arabidopsis. Interestingly, maize PIN1 expression at the incipient leaf primordium was greatly reduced in abph1 mutants. Consistently, auxin levels were reduced in abph1, and the maize PIN1 homolog was induced not only by auxin but also by cytokinin treatments. Our results indicate distinct roles for ABPH1 as a negative regulator of SAM size and a positive regulator of PIN1 expression. These studies highlight a complex interaction between auxin and cytokinin signaling in the specification of phyllotactic patterns and suggest an alternative model for the generation of altered phyllotactic patterns in abph1 mutants. We propose that reduced auxin levels and PIN1 expression in abph1 mutant SAMs delay leaf initiation, contributing to the enlarged SAM and altered phyllotaxy of these mutants. PMID:19321707

  10. Studies of aberrant phyllotaxy1 mutants of maize indicate complex interactions between auxin and cytokinin signaling in the shoot apical meristem.

    PubMed

    Lee, Byeong-ha; Johnston, Robyn; Yang, Yan; Gallavotti, Andrea; Kojima, Mikiko; Travençolo, Bruno A N; Costa, Luciano da F; Sakakibara, Hitoshi; Jackson, David

    2009-05-01

    One of the most fascinating aspects of plant morphology is the regular geometric arrangement of leaves and flowers, called phyllotaxy. The shoot apical meristem (SAM) determines these patterns, which vary depending on species and developmental stage. Auxin acts as an instructive signal in leaf initiation, and its transport has been implicated in phyllotaxy regulation in Arabidopsis (Arabidopsis thaliana). Altered phyllotactic patterns are observed in a maize (Zea mays) mutant, aberrant phyllotaxy1 (abph1, also known as abphyl1), and ABPH1 encodes a cytokinin-inducible type A response regulator, suggesting that cytokinin signals are also involved in the mechanism by which phyllotactic patterns are established. Therefore, we investigated the interaction between auxin and cytokinin signaling in phyllotaxy. Treatment of maize shoots with a polar auxin transport inhibitor, 1-naphthylphthalamic acid, strongly reduced ABPH1 expression, suggesting that auxin or its polar transport is required for ABPH1 expression. Immunolocalization of the PINFORMED1 (PIN1) polar auxin transporter revealed that PIN1 expression marks leaf primordia in maize, similarly to Arabidopsis. Interestingly, maize PIN1 expression at the incipient leaf primordium was greatly reduced in abph1 mutants. Consistently, auxin levels were reduced in abph1, and the maize PIN1 homolog was induced not only by auxin but also by cytokinin treatments. Our results indicate distinct roles for ABPH1 as a negative regulator of SAM size and a positive regulator of PIN1 expression. These studies highlight a complex interaction between auxin and cytokinin signaling in the specification of phyllotactic patterns and suggest an alternative model for the generation of altered phyllotactic patterns in abph1 mutants. We propose that reduced auxin levels and PIN1 expression in abph1 mutant SAMs delay leaf initiation, contributing to the enlarged SAM and altered phyllotaxy of these mutants. PMID:19321707

  11. New insights in shoot apical meristem morphogenesis: Isotropy comes into play

    PubMed Central

    Sassi, Massimiliano; Traas, Jan

    2015-01-01

    The great complexity and plasticity of aerial plant shapes largely results from the activity of the shoot apical meristem (SAM), a group of undifferentiated cells which produces all the aboveground organs of the plant. Organogenesis at the SAM is regulated by the hormone auxin, which, through an integration of active transport, signalling and transcriptional regulation, determines the positional and temporal information dictating where, when, and how a new organ will be formed. At the cellular level, the information stemming from the regulatory molecular networks influences the growth of the cells within the tissue to give rise to the final organ shape. The growth of plant cells is mainly controlled by the cell wall, a rigid structure mainly made of polysaccharides, which surrounds the cells and links them together in an organismal continuum. Over the years, several lines of evidence have pointed at a role for the regulation of the elasticity of the cell wall, downstream of auxin action, in the formation of organs at the SAM. We have recently shown that auxin also induces a shift toward isotropic growth by modulating the organization of cortical microtubules in peripheral SAM cells, which promotes organ formation. Here, we discuss our results and identify new hypotheses to drive future research. PMID:26337646

  12. Roles of extensins in cotyledon primordium formation and shoot apical meristem activity in Nicotiana tabacum

    PubMed Central

    Zhang, XueLian; Ren, YuJun; Zhao, Jie

    2008-01-01

    Extensins are cell wall basic glycoproteins with a polypeptide backbone that is extremely rich in hydroxyproline. In this paper, the function of extensins in embryo development was studied in Nicotiana tabacum. By using Western blot and immunohistochemistry, the extensin JIM20 epitopes were found to express in different developmental stages of embryos, and specifically in the top of the embryo proper (EP) and the suspensor of the late globular embryos. In order to clarify the functions of extensins, a potent hydroxyproline synthesis inhibitor, 3,4-dehydro-L-proline (3,4-DHP), was used in ovule and embryo culture. The results showed that the addition of 3,4-DHP caused abnormal embryos with single, asymmetry and supernumerary cotyledon primordia, and continuous culture led to cotyledon defects in the germinated seedlings. Histological sections showed that the shoot apical meristem (SAM) of the abnormal seedlings was dissimilar from the controls, especially in the seedlings with cup-shaped cotyledons. Furthermore, the vasculature of the abnormal cotyledons was in an out-of-order format and contained at least two main veins. Finally, both the hydroxyproline assay and fluorescent immunolocalization confirmed that 3,4-DHP treatment reduced the level of extensins in the cultured ovules and embryos. These results indicate that extensins may play important roles in the cotyledon primordium formation, SAM activity, and vasculature differentiation during embryo development. PMID:18931351

  13. Genetic control of morphometric diversity in the maize shoot apical meristem

    PubMed Central

    Leiboff, Samuel; Li, Xianran; Hu, Heng-Cheng; Todt, Natalie; Yang, Jinliang; Li, Xiao; Yu, Xiaoqing; Muehlbauer, Gary J.; Timmermans, Marja C. P.; Yu, Jianming; Schnable, Patrick S.; Scanlon, Michael J.

    2015-01-01

    The maize shoot apical meristem (SAM) comprises a small pool of stem cells that generate all above-ground organs. Although mutational studies have identified genetic networks regulating SAM function, little is known about SAM morphological variation in natural populations. Here we report the use of high-throughput image processing to capture rich SAM size variation within a diverse maize inbred panel. We demonstrate correlations between seedling SAM size and agronomically important adult traits such as flowering time, stem size and leaf node number. Combining SAM phenotypes with 1.2 million single nucleotide polymorphisms (SNPs) via genome-wide association study reveals unexpected SAM morphology candidate genes. Analyses of candidate genes implicated in hormone transport, cell division and cell size confirm correlations between SAM morphology and trait-associated SNP alleles. Our data illustrate that the microscopic seedling SAM is predictive of adult phenotypes and that SAM morphometric variation is associated with genes not previously predicted to regulate SAM size. PMID:26584889

  14. Genetic control of morphometric diversity in the maize shoot apical meristem.

    PubMed

    Leiboff, Samuel; Li, Xianran; Hu, Heng-Cheng; Todt, Natalie; Yang, Jinliang; Li, Xiao; Yu, Xiaoqing; Muehlbauer, Gary J; Timmermans, Marja C P; Yu, Jianming; Schnable, Patrick S; Scanlon, Michael J

    2015-01-01

    The maize shoot apical meristem (SAM) comprises a small pool of stem cells that generate all above-ground organs. Although mutational studies have identified genetic networks regulating SAM function, little is known about SAM morphological variation in natural populations. Here we report the use of high-throughput image processing to capture rich SAM size variation within a diverse maize inbred panel. We demonstrate correlations between seedling SAM size and agronomically important adult traits such as flowering time, stem size and leaf node number. Combining SAM phenotypes with 1.2 million single nucleotide polymorphisms (SNPs) via genome-wide association study reveals unexpected SAM morphology candidate genes. Analyses of candidate genes implicated in hormone transport, cell division and cell size confirm correlations between SAM morphology and trait-associated SNP alleles. Our data illustrate that the microscopic seedling SAM is predictive of adult phenotypes and that SAM morphometric variation is associated with genes not previously predicted to regulate SAM size. PMID:26584889

  15. Local auxin sources orient the apical-basal axis in Arabidopsis embryos.

    PubMed

    Robert, Hélène S; Grones, Peter; Stepanova, Anna N; Robles, Linda M; Lokerse, Annemarie S; Alonso, Jose M; Weijers, Dolf; Friml, Jiří

    2013-12-16

    Establishment of the embryonic axis foreshadows the main body axis of adults both in plants and in animals, but underlying mechanisms are considered distinct. Plants utilize directional, cell-to-cell transport of the growth hormone auxin to generate an asymmetric auxin response that specifies the embryonic apical-basal axis. The auxin flow directionality depends on the polarized subcellular localization of PIN-FORMED (PIN) auxin transporters. It remains unknown which mechanisms and spatial cues guide cell polarization and axis orientation in early embryos. Herein, we provide conceptually novel insights into the formation of embryonic axis in Arabidopsis by identifying a crucial role of localized tryptophan-dependent auxin biosynthesis. Local auxin production at the base of young embryos and the accompanying PIN7-mediated auxin flow toward the proembryo are required for the apical auxin response maximum and the specification of apical embryonic structures. Later in embryogenesis, the precisely timed onset of localized apical auxin biosynthesis mediates PIN1 polarization, basal auxin response maximum, and specification of the root pole. Thus, the tight spatiotemporal control of distinct local auxin sources provides a necessary, non-cell-autonomous trigger for the coordinated cell polarization and subsequent apical-basal axis orientation during embryogenesis and, presumably, also for other polarization events during postembryonic plant life. PMID:24291089

  16. Gene Expression patterns in cryogenically stored Arabidopsis thaliana shoot tips

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The genes expressed in response to cryostress in plant shoot tips are not known. In this project we compared the gene expression patterns in untreated, cryoprotectant-treated, and recovering shoot tips using differential display methods. This project identified two genes that appeared to be differ...

  17. Induction of Differentiation in the Shoot Apical Meristem by Transient Overexpression of a Retinoblastoma-Related Protein1

    PubMed Central

    Wyrzykowska, Joanna; Schorderet, Martine; Pien, Stéphane; Gruissem, Wilhelm; Fleming, Andrew J.

    2006-01-01

    The shoot apical meristem contains cells that undergo continual growth and division to generate the building blocks for the aerial portion of the plant. As cells leave the meristem, they undergo differentiation to form specific cell types. Most notably, heterotrophic cells of the meristem rapidly gain autotrophic capability by synthesis and assembly of components of the chloroplast. At the same time, cells undergo enlargement via vacuolation. Despite significant advances in the characterization of transcriptional networks involved in meristem maintenance and leaf determination, our understanding of the actual mechanism of meristem cell differentiation remains very limited. Using a microinduction technique, we show that local, transient overexpression of a retinoblastoma-related (RBR) protein in the shoot apical meristem is sufficient to trigger cells in the meristem to undergo the initial stages of differentiation. Taken together with recent data showing that RBR protein plays a key role in restricting stem cell differentiation in the root apical meristem, our data contribute to an emerging picture of RBR proteins as a central part of the mechanism controlling meristem cell differentiation. PMID:16815954

  18. Transcriptional profiling of the pea shoot apical meristem reveals processes underlying its function and maintenance

    PubMed Central

    Wong, Chui E; Bhalla, Prem L; Ottenhof, Harald; Singh, Mohan B

    2008-01-01

    Background Despite the importance of the shoot apical meristem (SAM) in plant development and organ formation, our understanding of the molecular mechanisms controlling its function is limited. Genomic tools have the potential to unravel the molecular mysteries of the SAM, and legume systems are increasingly being used in plant-development studies owing to their unique characteristics such as nitrogen fixation, secondary metabolism, and pod development. Garden pea (Pisum sativum) is a well-established classic model species for genetics studies that has been used since the Mendel era. In addition, the availability of a plethora of developmental mutants makes pea an ideal crop legume for genomics studies. This study aims to utilise genomics tools in isolating genes that play potential roles in the regulation of SAM activity. Results In order to identify genes that are differentially expressed in the SAM, we generated 2735 ESTs from three cDNA libraries derived from freshly micro-dissected SAMs from 10-day-old garden peas (Pisum sativum cv Torsdag). Custom-designed oligonucleotide arrays were used to compare the transcriptional profiles of pea SAMs and non-meristematic tissues. A total of 184 and 175 transcripts were significantly up- or down-regulated in the pea SAM, respectively. As expected, close to 61% of the transcripts down-regulated in the SAM were found in the public database, whereas sequences from the same source only comprised 12% of the genes that were expressed at higher levels in the SAM. This highlights the under-representation of transcripts from the meristematic tissues in the current public pea protein database, and demonstrates the utility of our SAM EST collection as an essential genetic resource for revealing further information on the regulation of this developmental process. In addition to unknowns, many of the up-regulated transcripts are known to encode products associated with cell division and proliferation, epigenetic regulation, auxin

  19. COORDINATION OF CELL PROLIFERATION AND CELL FATE DECISIONS IN THE ANGIOSPERM SHOOT APICAL MERISTEM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A unique feature of flowering plants is their ability to produce organs continuously, for hundreds of years in some species, from actively growing tips called apical meristems. All plants possess at least one form of apical meristem, whose cells are functionally analogous to animal stem cells becau...

  20. Quantitative trait loci associated with adventitious shoot formation in tissue culture and the program of shoot development in Arabidopsis.

    PubMed Central

    Lall, Sonia; Nettleton, Dan; DeCook, Rhonda; Che, Ping; Howell, Stephen H

    2004-01-01

    Arabidopsis ecotypes, Columbia (Col) and Landsberg erecta (Ler), differ in their capacity to regenerate shoots in culture, as do many other cultivars and varieties of the same plant species. Recombinant inbred (RI) lines derived from a cross of Col x Ler were scored for shoot regeneration, and the Arabidopsis genome was scanned using composite interval mapping for loci associated with shoot regeneration. Three QTL were identified--a major one on chromosome 5 in which the Col parent contributed the superior allele and two minor QTL on chromosomes 1 and 4 in which the Ler parent contributed the superior alleles. The RI lines were binned into genotypic pools to isolate the effects of the major QTL on chromosome 5 while holding the minor QTL constant. To identify genes with expression levels that are associated with the allelic state of the major QTL on chromosome 5, oligonucleotide array expression patterns for genes in the LLC pool (Ler alleles at the minor QTL and a Col allele at the major QTL) were compared to those in the LLL pool (Ler alleles at all QTL). The genes that were significantly differentially expressed between the two pools included several encoding transcription factors and signaling or transposon-related proteins. PMID:15342526

  1. Arabidopsis ABCG14 is essential for the root-to-shoot translocation of cytokinin

    PubMed Central

    Ko, Donghwi; Kang, Joohyun; Kiba, Takatoshi; Park, Jiyoung; Kojima, Mikiko; Do, Jihye; Kim, Kyung Yoon; Kwon, Mi; Endler, Anne; Song, Won-Yong; Martinoia, Enrico; Sakakibara, Hitoshi; Lee, Youngsook

    2014-01-01

    Cytokinins are phytohormones that induce cytokinesis and are essential for diverse developmental and physiological processes in plants. Cytokinins of the trans-zeatin type are mainly synthesized in root vasculature and transported to the shoot, where they regulate shoot growth. However, the mechanism of long-distance transport of cytokinin was hitherto unknown. Here, we report that the Arabidopsis ATP-binding cassette (ABC) transporter subfamily G14 (AtABCG14) is mainly expressed in roots and plays a major role in delivering cytokinins to the shoot. Loss of AtABCG14 expression resulted in severe shoot growth retardation, which was rescued by exogenous trans-zeatin application. Cytokinin content was decreased in the shoots of atabcg14 plants and increased in the roots, with consistent changes in the expression of cytokinin-responsive genes. Grafting of atabcg14 scions onto wild-type rootstocks restored shoot growth, whereas wild-type scions grafted onto atabcg14 rootstocks exhibited shoot growth retardation similar to that of atabcg14. Cytokinin concentrations in the xylem are reduced by ∼90% in the atabcg14 mutant. These results indicate that AtABCG14 is crucial for the translocation of cytokinin to the shoot. Our results provide molecular evidence for the long-distance transport of cytokinin and show that this transport is necessary for normal shoot development. PMID:24778257

  2. Clonal Analysis Provides Evidence for Transient Initial Cells in Shoot Apical Meristems of Seed Plants.

    PubMed

    Zagórska-Marek; Turzańska

    2000-03-01

    Drift of mutated sectors in sectorial or mericlinal plant chimeras has been interpreted as indirect evidence of initial impermanence at the apex. However, the same effect may result from mutation in noninitial cells positioned close to the vertex of the apical dome. Clonal analysis of the cell packets present in the superficial layer of spruce and magnolia apices provided the library of patterns suggesting that the position and the number of initial cells, and in some cases also the meristem axis inclination, may change over time. Multicellular clones originating from a single cell have been found in the geometric center of some apices, whereas in other apices the cellular center (where three or four clonal borders meet) did not correspond to the geome PMID:11010992

  3. Shared and distinct functions of the pseudokinase CORYNE (CRN) in shoot and root stem cell maintenance of Arabidopsis

    PubMed Central

    Somssich, Marc; Bleckmann, Andrea; Simon, Rüdiger

    2016-01-01

    Stem cell maintenance in plants depends on the activity of small secreted signaling peptides of the CLAVATA3/EMBRYO SURROUNDING REGION (CLE) family, which, in the shoot, act through at least three kinds of receptor complexes, CLAVATA1 (CLV1) homomers, CLAVATA2 (CLV2) / CORYNE (CRN) heteromers, and CLV1/CLV2/CRN multimers. In the root, the CLV2/CRN receptor complexes function in the proximal meristem to transmit signals from the CLE peptide CLE40. While CLV1 consists of an extracellular receptor domain and an intracellular kinase domain, CLV2, a leucine-rich repeat (LRR) receptor-like protein, and CRN, a protein kinase, have to interact to form a receptor–kinase complex. The kinase domain of CRN has been reported to be catalytically inactive, and it is not yet known how the CLV2/CRN complex can relay the perceived signal into the cells, and whether the kinase domain is necessary for signal transduction at all. In this study we show that the kinase domain of CRN is actively involved in CLV3 signal transduction in the shoot apical meristem of Arabidopsis, but it is dispensable for CRN protein function in root meristem maintenance. Hence, we provide an example of a catalytically inactive pseudokinase that is involved in two homologous pathways, but functions in distinctively different ways in each of them. PMID:27229734

  4. Dysfunctional mitochondria regulate the size of root apical meristem and leaf development in Arabidopsis

    PubMed Central

    Hsieh, Wei-Yu; Liao, Jo-Chien; Hsieh, Ming-Hsiun

    2015-01-01

    Mitochondria play an important role in maintaining metabolic and energy homeostasis in the plant cell. Thus, perturbation of mitochondrial structure and function will affect plant growth and development. Arabidopsis slow growth3 (slo3) is defective in At3g61360 that encodes a pentatricopeptide repeat (PPR) protein. Analysis of slo3 mitochondrial RNA metabolism revealed that the splicing of nad7 intron 2 is impaired, which leads to a dramatic reduction in complex I activity. So the SLO3 PPR protein is a splicing factor that is required for the removal of nad7 intron 2 in Arabidopsis. The slo3 mutant plants have obvious phenotypes with severe growth retardation and delayed development. The size of root apical meristem (RAM) is reduced and the production of meristem cells is decreased in slo3. Furthermore, the rosette leaves of slo3 are curled or crinkled, which may be derived from uneven growth of the leaf surface. The underlying mechanisms by which dysfunctional mitochondria affect these growth and developmental phenotypes have yet to be established. Nonetheless, plant hormone auxin is known to play an important role in orchestrating the development of RAM and leaf shape. It is possible that dysfunctional mitochondria may interact with auxin signaling pathways to regulate the boundary of RAM and the cell division arrest front during leaf growth in Arabidopsis. PMID:26237004

  5. ROS-mediated vascular homeostatic control of root-to-shoot soil Na delivery in Arabidopsis

    PubMed Central

    Jiang, Caifu; Belfield, Eric J; Mithani, Aziz; Visscher, Anne; Ragoussis, Jiannis; Mott, Richard; Smith, J Andrew C; Harberd, Nicholas P

    2012-01-01

    Sodium (Na) is ubiquitous in soils, and is transported to plant shoots via transpiration through xylem elements in the vascular tissue. However, excess Na is damaging. Accordingly, control of xylem-sap Na concentration is important for maintenance of shoot Na homeostasis, especially under Na stress conditions. Here we report that shoot Na homeostasis of Arabidopsis thaliana plants grown in saline soils is conferred by reactive oxygen species (ROS) regulation of xylem-sap Na concentrations. We show that lack of A. thaliana respiratory burst oxidase protein F (AtrbohF; an NADPH oxidase catalysing ROS production) causes hypersensitivity of shoots to soil salinity. Lack of AtrbohF-dependent salinity-induced vascular ROS accumulation leads to increased Na concentrations in root vasculature cells and in xylem sap, thus causing delivery of damaging amounts of Na to the shoot. We also show that the excess shoot Na delivery caused by lack of AtrbohF is dependent upon transpiration. We conclude that AtrbohF increases ROS levels in wild-type root vasculature in response to raised soil salinity, thereby limiting Na concentrations in xylem sap, and in turn protecting shoot cells from transpiration-dependent delivery of excess Na. PMID:23064146

  6. Disentangling the Intertwined Genetic Bases of Root and Shoot Growth in Arabidopsis

    PubMed Central

    Bouteillé, Marie; Rolland, Gaëlle; Balsera, Crispulo; Loudet, Olivier; Muller, Bertrand

    2012-01-01

    Root growth and architecture are major components of plant nutrient and water use efficiencies and these traits are the matter of extensive genetic analysis in several crop species. Because root growth relies on exported assimilate from the shoot, and changes in assimilate supply are known to alter root architecture, we hypothesized (i) that the genetic bases of root growth could be intertwined with the genetic bases of shoot growth and (ii) that the link could be either positive, with alleles favouring shoot growth also favouring root growth, or negative, because of competition for assimilates. We tested these hypotheses using a quantitative genetics approach in the model species Arabidopsis thaliana and the Bay-0×Shahdara recombinant inbred lines population. In accordance with our hypothesis, root and shoot growth traits were strongly correlated and most root growth quantitative trait loci (QTLs) colocalized with shoot growth QTLs with positive alleles originating from either the same or the opposite parent. In order to identify regions that could be responsible for root growth independently of the shoot, we generated new variables either based on root to shoot ratios, residuals of root to shoot correlations or coordinates of principal component analysis. These variables showed high heritability allowing genetic analysis. They essentially all yielded similar results pointing towards two regions involved in the root – shoot balance. Using Heterogeneous Inbred Families (a kind of near-isogenic lines), we validated part of the QTLs present in these two regions for different traits. Our study thus highlights the difficulty of disentangling intertwined genetic bases of root and shoot growth and shows that this difficulty can be overcome by using simple statistical tools. PMID:22384215

  7. Coordinated regulation of apical hook development by gibberellins and ethylene in etiolated Arabidopsis seedlings

    PubMed Central

    An, Fengying; Zhang, Xing; Zhu, Ziqiang; Ji, Yusi; He, Wenrong; Jiang, Zhiqiang; Li, Mingzhe; Guo, Hongwei

    2012-01-01

    Dark-grown Arabidopsis seedlings develop an apical hook when germinating in soil, which protects the cotyledons and apical meristematic tissues when protruding through the soil. Several hormones are reported to distinctly modulate this process. Previous studies have shown that ethylene and gibberellins (GAs) coordinately regulate the hook development, although the underlying molecular mechanism is largely unknown. Here we showed that GA3 enhanced while paclobutrazol repressed ethylene- and EIN3-overexpression (EIN3ox)-induced hook curvature, and della mutant exhibited exaggerated hook curvature, which required an intact ethylene signaling pathway. Genetic study revealed that GA-enhanced hook development was dependent on HOOKLESS 1 (HLS1), a central regulator mediating the input of the multiple signaling pathways during apical hook development. We further found that GA3 induced (and DELLA proteins repressed) HLS1 expression in an ETHYLENE INSENSITIVE 3/EIN3-LIKE 1 (EIN3/EIL1)-dependent manner, whereby EIN3/EIL1 activated HLS1 transcription by directly binding to its promoter. Additionally, DELLA proteins were found to interact with the DNA-binding domains of EIN3/EIL1 and repress EIN3/EIL1-regulated HLS1 expression. Treatment with naphthylphthalamic acid, a polar auxin transport inhibitor, repressed the constitutively exaggerated hook curvature of EIN3ox line and della mutant, supporting that auxin functions downstream of the ethylene and GA pathways in hook development. Taken together, our results identify EIN3/EIL1 as a new class of DELLA-associated transcription factors and demonstrate that GA promotes apical hook formation in cooperation with ethylene partly by inducing the expression of HLS1 via derepression of EIN3/EIL1 functions. PMID:22349459

  8. An Indirect Role for Ethylene in Shoot-inversion Release of Apical Dominance in Pharbitis Nil

    NASA Technical Reports Server (NTRS)

    Cline, M. G.

    1985-01-01

    Evidence is presented which indicated that ethylene does not play a direct role in promoting or inhibiting bud outgrowth as a gravity response. It is concluded that the treatment of inactive or induced lateral buds with ethylene inhibitors or ethrel has no significant effect on bud outgrowth and that no changes occur in ethylene emanation in the Highest Lateral Bud (HLB) or HLB node following shoot inversion. Possible mechanisms by which ethylene released by shoot inversion may indirectly promote outgrowth of the HLB is presented.

  9. Cryopreservation of in vitro grown shoot tips and apical meristems of the forage legume Arachis pintoi.

    PubMed

    Rey, Hebe Y; Faloci, Mirta; Medina, Ricardo; Dolce, Natalia; Mroginski, Luis; Engelmann, Florent

    2009-01-01

    A cryopreservation protocol using the encapsulation-dehydration procedure was established for shoot tips (2-3 mm in length) and meristems (0.3-0.5 mm) sampled from in vitro plantlets of diploid and triploid cytotypes of Arachis pintoi. The optimal protocol was the following: after dissection, explants were precultured for 24 h on establishment medium (EM), encapsulated in calcium alginate beads and pretreated in liquid EM medium with daily increasing sucrose concentration (0.5, 0.75, 1.0 M) and desiccated to 22-23 percent moisture content (fresh weight basis). Explants were frozen using slow cooling (1 C per min from 25C to -30C followed by direct immersion in liquid nitrogen), thawed rapidly and post-cultured in liquid EM medium enriched with daily decreasing sucrose concentrations (0.75, 0.50, 0.1 M). Explants were then transferred to solid EM medium in order to achieve shoot regeneration, then on Murashige and Skoog medium supplemented with 0.05 microM naphthalene acetic acid to induce rooting of shoots. With this procedure, 53 percent and 56 percent of cryopreserved shoot tips of the diploid and triploid cytotypes, respectively, survived and formed plants. However, only 16 percent of cryopreserved meristems of both cytotypes regenerated plants. Using ten isozyme systems and seven RAPD profiles, no modification induced by cryopreservation could be detected in plantlets regenerated from cryopreserved material. PMID:19946657

  10. Grafting with rootstocks induces extensive transcriptional re-programming in the shoot apical meristem of grapevine

    PubMed Central

    2013-01-01

    Background Grafting is widely used in the agriculture of fruit-bearing crops; rootstocks are known to confer differences in scion biomass in addition to improving other traits of agricultural interest. However, little is known about the effect of rootstocks on scion gene expression. The objective of this study was to determine whether hetero-grafting the grapevine variety Vitis vinifera cv. 'Cabernet Sauvignon N’ with two different rootstocks alters gene expression in the shoot apex in comparison to the auto-grafted control. Cabernet Sauvignon was hetero-grafted with two commercial rootstock genotypes and auto-grafted with itself. Vigor was quantified by measurements of root, stem, leaf and trunk biomass. Gene expression profiling was done using a whole genome grapevine microarray; four pools of five shoot apex samples were harvested 4 months after grafting for each scion/rootstock combination. Results The rootstocks increased stem biomass or conferred increased vigor by the end of the first growth cycle. Globally hetero-grafting two different genotypes together triggered an increase in shoot apex gene expression; however no genes were differentially expressed between the two hetero-grafts. The functional categories related to DNA, chromatin structure, histones, flavonoids and leucine rich repeat containing receptor kinases were the most enriched in the up-regulated genes in the shoot apex of hetero-grafted plants. Conclusions The choice of rootstock genotype had little effect on the gene expression in the shoot apex; this could suggest that auto- and hetero-grafting was the major factor regulating gene expression. PMID:24083813

  11. Using Arabidopsis to Study Shoot Branching in Biomass Willow1[C][W][OA

    PubMed Central

    Ward, Sally P.; Salmon, Jemma; Hanley, Steven J.; Karp, Angela; Leyser, Ottoline

    2013-01-01

    The success of the short-rotation coppice system in biomass willow (Salix spp.) relies on the activity of the shoot-producing meristems found on the coppice stool. However, the regulation of the activity of these meristems is poorly understood. In contrast, our knowledge of the mechanisms behind axillary meristem regulation in Arabidopsis (Arabidopsis thaliana) has grown rapidly in the past few years through the exploitation of integrated physiological, genetic, and molecular assays. Here, we demonstrate that these assays can be directly transferred to study the control of bud activation in biomass willow and to assess similarities with the known hormone regulatory system in Arabidopsis. Bud hormone response was found to be qualitatively remarkably similar in Salix spp. and Arabidopsis. These similarities led us to test whether Arabidopsis hormone mutants could be used to assess allelic variation in the cognate Salix spp. hormone genes. Allelic differences in Salix spp. strigolactone genes were observed using this approach. These results demonstrate that both knowledge and assays from Arabidopsis axillary meristem biology can be successfully applied to Salix spp. and can increase our understanding of a fundamental aspect of short-rotation coppice biomass production, allowing more targeted breeding. PMID:23610219

  12. Interaction between selected bacterial strains and Arabidopsis halleri modulates shoot proteome and cadmium and zinc accumulation

    PubMed Central

    Panigati, Monica; Furini, Antonella

    2011-01-01

    The effects of plant–microbe interactions between the hyperaccumulator Arabidopsis halleri and eight bacterial strains, isolated from the rhizosphere of A. halleri plants grown in a cadmium- and zinc-contaminated site, were analysed for shoot metal accumulation, shoot proteome, and the transcription of genes involved in plant metal homeostasis and hyperaccumulation. Cadmium and zinc concentrations were lower in the shoots of plants cultivated in the presence of these metals plus the selected bacterial strains compared with plants grown solely with these metals or, as previously reported, with plants grown with these metals plus the autochthonous rhizosphere-derived microorganisms. The shoot proteome of plants cultivated in the presence of these selected bacterial strains plus metals, showed an increased abundance of photosynthesis- and abiotic stress-related proteins (e.g. subunits of the photosynthetic complexes, Rubisco, superoxide dismutase, and malate dehydrogenase) counteracted by a decreased amount of plant defence-related proteins (e.g. endochitinases, vegetative storage proteins, and β-glucosidase). The transcription of several homeostasis genes was modulated by the microbial communities and by Cd and Zn content in the shoot. Altogether these results highlight the importance of plant-microbe interactions in plant protein expression and metal accumulation and emphasize the possibility of exploiting microbial consortia for increasing or decreasing shoot metal content. PMID:21357773

  13. An improved grafting technique for mature Arabidopsis plants demonstrates long-distance shoot-to-root transport of phytochelatins in Arabidopsis.

    PubMed

    Chen, Alice; Komives, Elizabeth A; Schroeder, Julian I

    2006-05-01

    Phytochelatins (PCs) are peptides that function in heavy-metal chelation and detoxification in plants and fungi. A recent study showed that PCs have the ability to undergo long-distance transport in a root-to-shoot direction in transgenic Arabidopsis (Arabidopsis thaliana). To determine whether long-distance transport of PCs can occur in the opposite direction, from shoots to roots, the wheat (Triticum aestivum) PC synthase (TaPCS1) gene was expressed under the control of a shoot-specific promoter (CAB2) in an Arabidopsis PC-deficient mutant, cad1-3 (CAB2TaPCS1/cad1-3). Analyses demonstrated that TaPCS1 is expressed only in shoots and that CAB2TaPCS1/cad1-3 lines complement the cadmium (Cd) and arsenic metal sensitivity of cad1-3 shoots. CAB2TaPCS1/cad1-3 plants exhibited higher Cd accumulation in roots and lower Cd accumulation in shoots compared to wild type. Fluorescence HPLC coupled to mass spectrometry analyses directly detected PC2 in the roots of CAB2:TaPCS1/cad1-3 but not in cad1-3 controls, suggesting that PC2 is transported over long distances in the shoot-to-root direction. In addition, wild-type shoot tissues were grafted onto PC synthase cad1-3 atpcs2-1 double loss-of-function mutant root tissues. An Arabidopsis grafting technique for mature plants was modified to obtain an 84% success rate, significantly greater than a previous rate of approximately 11%. Fluorescence HPLC-mass spectrometry showed the presence of PC2, PC3, and PC4 in the root tissue of grafts between wild-type shoots and cad1-3 atpcs2-1 double-mutant roots, demonstrating that PCs are transported over long distances from shoots to roots in Arabidopsis. PMID:16531489

  14. Dissecting the molecular signatures of apical cell-type shoot meristems from two ancient land plant lineages.

    PubMed

    Frank, Margaret H; Edwards, Molly B; Schultz, Eric R; McKain, Michael R; Fei, Zhangjun; Sørensen, Iben; Rose, Jocelyn K C; Scanlon, Michael J

    2015-08-01

    Shoot apical meristem (SAM) structure varies markedly within the land plants. The SAMs of many seedless vascular plants contain a conspicuous inverted, pyramidal cell called the apical cell (AC), which is unidentified in angiosperms. In this study, we use transcriptomic sequencing with precise laser microdissections of meristem subdomains to define the molecular signatures of anatomically distinct zones from the AC-type SAMs of a lycophyte (Selaginella moellendorffii) and a monilophyte (Equisetum arvense). The two model species for this study represent vascular plant lineages that diverged > 400 million yr ago. Our data comprise comprehensive molecular signatures for the distinct subdomains within AC-type SAMs, an anatomical anomaly whose functional significance has been debated in the botanical literature for over two centuries. Moreover, our data provide molecular support for distinct gene expression programs between the AC-type SAMs of Selaginella and Equisetum, as compared with the SAM transcriptome of the angiosperm maize. The results are discussed in light of the functional significance and evolutionary success of the AC-type SAM within the embryophytes. PMID:25900772

  15. SUPPRESSOR OF APICAL DOMINANCE1 of Sporisorium reilianum Modulates Inflorescence Branching Architecture in Maize and Arabidopsis1[OPEN

    PubMed Central

    Ghareeb, Hassan; Löfke, Christian; Teichmann, Thomas; Schirawski, Jan

    2015-01-01

    The biotrophic fungus Sporisorium reilianum causes head smut of maize (Zea mays) after systemic plant colonization. Symptoms include the formation of multiple female inflorescences at subapical nodes of the stalk because of loss of apical dominance. By deletion analysis of cluster 19-1, the largest genomic divergence cluster in S. reilianum, we identified a secreted fungal effector responsible for S. reilianum-induced loss of apical dominance, which we named SUPPRESSOR OF APICAL DOMINANCE1 (SAD1). SAD1 transcript levels were highly up-regulated during biotrophic fungal growth in all infected plant tissues. SAD1-green fluorescent protein fusion proteins expressed by recombinant S. reilianum localized to the extracellular hyphal space. Transgenic Arabidopsis (Arabidopsis thaliana)-expressing green fluorescent protein-SAD1 displayed an increased number of secondary rosette-leaf branches. This suggests that SAD1 manipulates inflorescence branching architecture in maize and Arabidopsis through a conserved pathway. Using a yeast (Saccharomyces cerevisiae) two-hybrid library of S. reilianum-infected maize tissues, we identified potential plant interaction partners that had a predicted function in ubiquitination, signaling, and nuclear processes. Presence of SAD1 led to an increase of the transcript levels of the auxin transporter PIN-FORMED1 in the root and a reduction of the branching regulator TEOSINTE BRANCHED1 in the stalk. This indicates a role of SAD1 in regulation of apical dominance by modulation of branching through increasing transcript levels of the auxin transporter PIN1 and derepression of bud outgrowth. PMID:26511912

  16. N(6)-Methyladenosine RNA Modification Regulates Shoot Stem Cell Fate in Arabidopsis.

    PubMed

    Shen, Lisha; Liang, Zhe; Gu, Xiaofeng; Chen, Ying; Teo, Zhi Wei Norman; Hou, Xingliang; Cai, Weiling Maggie; Dedon, Peter C; Liu, Lu; Yu, Hao

    2016-07-25

    N(6)-Methyladenosine (m(6)A) represents the most prevalent internal modification on mRNA and requires a multicomponent m(6)A methyltransferase complex in mammals. How their plant counterparts determine the global m(6)A modification landscape and its molecular link to plant development remain unknown. Here we show that FKBP12 INTERACTING PROTEIN 37 KD (FIP37) is a core component of the m(6)A methyltransferase complex, which underlies control of shoot stem cell fate in Arabidopsis. The mutants lacking FIP37 exhibit massive overproliferation of shoot meristems and a transcriptome-wide loss of m(6)A RNA modifications. We further demonstrate that FIP37 mediates m(6)A RNA modification on key shoot meristem genes inversely correlated with their mRNA stability, thus confining their transcript levels to prevent shoot meristem overproliferation. Our results suggest an indispensable role of FIP37 in mediating m(6)A mRNA modification, which is required for maintaining the shoot meristem as a renewable source for continuously producing all aerial organs in plants. PMID:27396363

  17. ALTERED MERISTEM PROGRAM1 Suppresses Ectopic Stem Cell Niche Formation in the Shoot Apical Meristem in a Largely Cytokinin-Independent Manner1[OPEN

    PubMed Central

    Huang, Wenwen; Pitorre, Delphine; Poretska, Olena; Marizzi, Christine; Winter, Nikola; Poppenberger, Brigitte; Sieberer, Tobias

    2015-01-01

    Plants are able to reiteratively form new organs in an environmentally adaptive manner during postembryonic development. Organ formation in plants is dependent on stem cell niches (SCNs), which are located in the so-called meristems. Meristems show a functional zonation along the apical-basal axis and the radial axis. Shoot apical meristems of higher plants are dome-like structures, which contain a central SCN that consists of an apical stem cell pool and an underlying organizing center. Organ primordia are formed in the circular peripheral zone (PZ) from stem cell descendants in which differentiation programs are activated. One mechanism to keep this radial symmetry integrated is that the existing SCN actively suppresses stem cell identity in the PZ. However, how this lateral inhibition system works at the molecular level is far from understood. Here, we show that a defect in the putative carboxypeptidase ALTERED MERISTEM PROGRAM1 (AMP1) causes the formation of extra SCNs in the presence of an intact primary shoot apical meristem, which at least partially contributes to the enhanced shoot meristem size and leaf initiation rate found in the mutant. This defect appears to be neither a specific consequence of the altered cytokinin levels in amp1 nor directly mediated by the WUSCHEL/CLAVATA feedback loop. De novo formation of supernumerary stem cell pools was further enhanced in plants mutated in both AMP1 and its paralog LIKE AMP1, indicating that they exhibit partially overlapping roles to suppress SCN respecification in the PZ. PMID:25673776

  18. Structural Requirements of Strigolactones for Shoot Branching Inhibition in Rice and Arabidopsis.

    PubMed

    Umehara, Mikihisa; Cao, Mengmeng; Akiyama, Kohki; Akatsu, Tomoki; Seto, Yoshiya; Hanada, Atsushi; Li, Weiqiang; Takeda-Kamiya, Noriko; Morimoto, Yu; Yamaguchi, Shinjiro

    2015-06-01

    The structural requirements of strigolactones (SLs) involved in germination induction of root parasitic plants and hyphal branching in arbuscular mycorrhizal (AM) fungi have been extensively studied. However, our knowledge of the requirements of SLs involved in shoot branching inhibition in plants is still limited. To address this question, we investigated the structure-activity relationships of SLs in shoot branching inhibition in rice and Arabidopsis. SLs possess a four-ring structure, with a tricyclic lactone (ABC-rings) connected to a methylbutenolide part (D-ring) via an enol ether bridge. Here, we show that the the (R) configuration at C-2', which determines the steric position of the D-ring relative to the enol ether olefin bond, is critical for the hormonal activity in rice. Replacement of the enol ether moiety by an alkoxy or imino ether resulted in a severe reduction in biological activity in rice. Moreover, yeast two-hybrid experiments using a possible SL receptor, DWARF14 (D14), and a repressor in the SL signaling pathway, DWARF53 (D53), showed that D14 can interact with D53 in the presence of (2'R) stereoisomers of SLs, but not (2'S) stereoisomers, suggesting that the stereostructure of SLs is crucial for the interaction of these proteins. When GR5, an AB-ring-truncated analog, was applied to the hydroponic culture medium, strong inhibition of shoot branching was observed both in rice and in Arabidopsis. However, GR5 was only weakly active when directly applied to the axillary buds of Arabidopsis. Our results indicate that the difference in plant species and application methods greatly influences the apparent SL biological activity. PMID:25713176

  19. Auxin Overproduction in Shoots Cannot Rescue Auxin Deficiencies in Arabidopsis Roots

    PubMed Central

    Chen, Qingguo; Dai, Xinhua; De-Paoli, Henrique; Cheng, Youfa; Takebayashi, Yumiko; Kasahara, Hiroyuki; Kamiya, Yuji; Zhao, Yunde

    2014-01-01

    Auxin plays an essential role in root development. It has been a long-held dogma that auxin required for root development is mainly transported from shoots into roots by polarly localized auxin transporters. However, it is known that auxin is also synthesized in roots. Here we demonstrate that a group of YUCCA (YUC) genes, which encode the rate-limiting enzymes for auxin biosynthesis, plays an essential role in Arabidopsis root development. Five YUC genes (YUC3, YUC5, YUC7, YUC8 and YUC9) display distinct expression patterns during root development. Simultaneous inactivation of the five YUC genes (yucQ mutants) leads to the development of very short and agravitropic primary roots. The yucQ phenotypes are rescued by either adding 5 nM of the natural auxin, IAA, in the growth media or by expressing a YUC gene in the roots of yucQ. Interestingly, overexpression of a YUC gene in shoots in yucQ causes the characteristic auxin overproduction phenotypes in shoots; however, the root defects of yucQ are not rescued. Our data demonstrate that localized auxin biosynthesis in roots is required for normal root development and that auxin transported from shoots is not sufficient for supporting root elongation and root gravitropic responses. PMID:24562917

  20. Auxin overproduction in shoots cannot rescue auxin deficiencies in Arabidopsis roots.

    PubMed

    Chen, Qingguo; Dai, Xinhua; De-Paoli, Henrique; Cheng, Youfa; Takebayashi, Yumiko; Kasahara, Hiroyuki; Kamiya, Yuji; Zhao, Yunde

    2014-06-01

    Auxin plays an essential role in root development. It has been a long-held dogma that auxin required for root development is mainly transported from shoots into roots by polarly localized auxin transporters. However, it is known that auxin is also synthesized in roots. Here we demonstrate that a group of YUCCA (YUC) genes, which encode the rate-limiting enzymes for auxin biosynthesis, plays an essential role in Arabidopsis root development. Five YUC genes (YUC3, YUC5, YUC7, YUC8 and YUC9) display distinct expression patterns during root development. Simultaneous inactivation of the five YUC genes (yucQ mutants) leads to the development of very short and agravitropic primary roots. The yucQ phenotypes are rescued by either adding 5 nM of the natural auxin, IAA, in the growth media or by expressing a YUC gene in the roots of yucQ. Interestingly, overexpression of a YUC gene in shoots in yucQ causes the characteristic auxin overproduction phenotypes in shoots; however, the root defects of yucQ are not rescued. Our data demonstrate that localized auxin biosynthesis in roots is required for normal root development and that auxin transported from shoots is not sufficient for supporting root elongation and root gravitropic responses. PMID:24562917

  1. Gene expression and proteomic analysis of shoot apical meristem transition from dormancy to activation in Cunninghamia lanceolata (Lamb.) Hook

    PubMed Central

    Xu, Huimin; Cao, Dechang; Chen, Yanmei; Wei, Dongmei; Wang, Yanwei; Stevenson, Rebecca Ann; Zhu, Yingfang; Lin, Jinxing

    2016-01-01

    In contrast to annual plants, in perennial plants, the shoot apical meristem (SAM) can undergo seasonal transitions between dormancy and activity; understanding this transition is crucial for understanding growth in perennial plants. However, little is known about the molecular mechanisms of SAM development in trees. Here, light and transmission electron microscopy revealed that evident changes in starch granules, lipid bodies, and cell walls thickness of the SAM in C. lanceolata during the transition from dormancy to activation. HPLC-ESI-MS/MS analysis showed that levels of indole-3-acetic acid (IAA) increased and levels of abscisic acid (ABA) decreased from dormant to active stage. Examination of 20 genes and 132 differentially expressed proteins revealed that the expression of genes and proteins potentially involved in cell division and expansion significantly increased in the active stage, whereas those related to the abscisic acid insensitive 3(ABI3), the cytoskeleton and energy metabolism decreased in the dormant stage. These findings provide new insights into the complex mechanism of gene and protein expression and their relation to cytological and physiological changes of SAM in this coniferous species. PMID:26832850

  2. Gene expression and proteomic analysis of shoot apical meristem transition from dormancy to activation in Cunninghamia lanceolata (Lamb.) Hook.

    PubMed

    Xu, Huimin; Cao, Dechang; Chen, Yanmei; Wei, Dongmei; Wang, Yanwei; Stevenson, Rebecca Ann; Zhu, Yingfang; Lin, Jinxing

    2016-01-01

    In contrast to annual plants, in perennial plants, the shoot apical meristem (SAM) can undergo seasonal transitions between dormancy and activity; understanding this transition is crucial for understanding growth in perennial plants. However, little is known about the molecular mechanisms of SAM development in trees. Here, light and transmission electron microscopy revealed that evident changes in starch granules, lipid bodies, and cell walls thickness of the SAM in C. lanceolata during the transition from dormancy to activation. HPLC-ESI-MS/MS analysis showed that levels of indole-3-acetic acid (IAA) increased and levels of abscisic acid (ABA) decreased from dormant to active stage. Examination of 20 genes and 132 differentially expressed proteins revealed that the expression of genes and proteins potentially involved in cell division and expansion significantly increased in the active stage, whereas those related to the abscisic acid insensitive 3(ABI3), the cytoskeleton and energy metabolism decreased in the dormant stage. These findings provide new insights into the complex mechanism of gene and protein expression and their relation to cytological and physiological changes of SAM in this coniferous species. PMID:26832850

  3. Arabidopsis alcohol dehydrogenase expression in both shoots and roots is conditioned by root growth environment

    NASA Technical Reports Server (NTRS)

    Chung, H. J.; Ferl, R. J.

    1999-01-01

    It is widely accepted that the Arabidopsis Adh (alcohol dehydrogenase) gene is constitutively expressed at low levels in the roots of young plants grown on agar media, and that the expression level is greatly induced by anoxic or hypoxic stresses. We questioned whether the agar medium itself created an anaerobic environment for the roots upon their growing into the gel. beta-Glucuronidase (GUS) expression driven by the Adh promoter was examined by growing transgenic Arabidopsis plants in different growing systems. Whereas roots grown on horizontal-positioned plates showed high Adh/GUS expression levels, roots from vertical-positioned plates had no Adh/GUS expression. Additional results indicate that growth on vertical plates closely mimics the Adh/GUS expression observed for soil-grown seedlings, and that growth on horizontal plates results in induction of high Adh/GUS expression that is consistent with hypoxic or anoxic conditions within the agar of the root zone. Adh/GUS expression in the shoot apex is also highly induced by root penetration of the agar medium. This induction of Adh/GUS in shoot apex and roots is due, at least in part, to mechanisms involving Ca2+ signal transduction.

  4. Complexation of arsenite with phytochelatins reduces arsenite efflux and translocation from roots to shoots in Arabidopsis.

    PubMed

    Liu, Wen-Ju; Wood, B Alan; Raab, Andrea; McGrath, Steve P; Zhao, Fang-Jie; Feldmann, Jörg

    2010-04-01

    Complexation of arsenite [As(III)] with phytochelatins (PCs) is an important mechanism employed by plants to detoxify As; how this complexation affects As mobility was little known. We used high-resolution inductively coupled plasma-mass spectrometry and accurate mass electrospray ionization-mass spectrometry coupled to HPLC to identify and quantify As(III)-thiol complexes and free thiol compounds in Arabidopsis (Arabidopsis thaliana) exposed to arsenate [As(V)]. As(V) was efficiently reduced to As(III) in roots. In wild-type roots, 69% of As was complexed as As(III)-PC4, As(III)-PC3, and As(III)-(PC2)2. Both the glutathione (GSH)-deficient mutant cad2-1 and the PC-deficient mutant cad1-3 were approximately 20 times more sensitive to As(V) than the wild type. In cad1-3 roots, only 8% of As was complexed with GSH as As(III)-(GS)3 and no As(III)-PCs were detected, while in cad2-1 roots, As(III)-PCs accounted for only 25% of the total As. The two mutants had a greater As mobility, with a significantly higher accumulation of As(III) in shoots and 4.5 to 12 times higher shoot-to-root As concentration ratio than the wild type. Roots also effluxed a substantial proportion of the As(V) taken up as As(III) to the external medium, and this efflux was larger in the two mutants. Furthermore, when wild-type plants were exposed to l-buthionine sulfoximine or deprived of sulfur, both As(III) efflux and root-to-shoot translocation were enhanced. The results indicate that complexation of As(III) with PCs in Arabidopsis roots decreases its mobility for both efflux to the external medium and for root-to-shoot translocation. Enhancing PC synthesis in roots may be an effective strategy to reduce As translocation to the edible organs of food crops. PMID:20130102

  5. Apical control, gravitropic signaling, and the growth of lateral roots in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Mullen, Jack L.; Wolverton, Chris; Hangarter, Roger P.

    Most research on gravity responses in plants has focused on primary roots and shoots, which typically grow in a vertical orientation. However, the patterns of lateral organ growth, which generally have large effects on overall plant architecture, are such that the organs are typically not vertical. In lateral roots of Arabidopsis, growth is initially in a nearly horizontal orientation but changes to a near-vertical orientation as the lateral root develops. Although the non-vertical lateral roots are gravitropically competent, following gravitropic reorientation of seedlings, the lateral roots on the upper flank of the primary root have different growth patterns from those on the lower side of the primary root. The differences are in part dependent on reorientation of the primary root, suggesting that gravitropic signaling from the primary root also contributes to the control of lateral root growth. The hormone auxin appears to play a role in this signaling between the primary and lateral roots, as auxin transport inhibitors applied to the primary root affect lateral root growth. Also, lateral roots of pin3 mutants, which are impaired in polar auxin transport, have altered lateral root orientations. However, other signals from the primary root tip also play an important role in regulating lateral root growth.

  6. Regrowth patterns and rosette attributes contribute to the differential compensatory responses of Arabidopsis thaliana genotypes to apical damage.

    PubMed

    Scholes, D R; Wszalek, A E; Paige, K N

    2016-03-01

    A plant's compensatory performance refers to its ability to maintain or increase its reproductive output following damage. The ability of a plant to compensate depends on numerous factors including the type, severity, frequency and timing of damage, the environmental conditions and the plant's genotype. Upon apical damage, a cascade of hormonal and genetic responses often produces dramatic changes in a plant's growth, development, architecture and physiology. All else being equal, this response is largely dependent on a plant's genotype, with different regrowth patterns displayed by different genotypes of a given species. In this study, we compare the architectural and growth patterns of two Arabidopsis thaliana genotypes following apical damage. Specifically, we characterise regrowth patterns of the genotypes Columbia-4 and Landsberg erecta, which typically differ in their compensation to apical meristem removal. We report that Landsberg erecta suffered reductions in the number of stems produced, maximum elongation rate, a delay in reaching this rate, lower average rosette quality throughout the growing period, and ultimately, less aboveground dry biomass and seed production when damaged compared to undamaged control plants. Columbia-4 had no reductions in any of these measures and maintained larger rosette area when clipped relative to when unclipped. Based on the apparent influence of the rosette on these genotypes' compensatory performances, we performed a rosette removal experiment, which confirmed that the rosette contributes to compensatory performance. This study provides a novel characterisation of regrowth patterns following apical damage, with insights into those measures having the largest effect on plant performance. PMID:26434737

  7. Caesium and strontium accumulation in shoots of Arabidopsis thaliana: genetic and physiological aspects

    PubMed Central

    Kanter, Ulrike; Hauser, Andreas; Michalke, Bernhard; Dräxl, Stephan; Schäffner, Anton R.

    2010-01-01

    Due to the physico-chemical similarities of caesium (Cs+) to potassium (K+) on the one hand and strontium (Sr2+) to calcium (Ca2+) on the other hand, both elements can easily be taken up by plants and thus enter the food chain. This could be detrimental when radionuclides such as 137Cs and 90Sr are involved. In this study, both genetic and physiological aspects of Cs+ and Sr2+ accumulation in Arabidopsis thaliana were investigated using 86 Arabidopsis accessions and a segregating F2 population of the low Cs+ accumulating Sq-1 (Ascot, UK) crossed with the high uptaking Sorbo (Khurmatov, Tajikistan). Hydroponically grown plants were exposed to subtoxic levels of Cs+ and Sr2+ using radioactive isotopes as tracers. In the natural accessions shoot concentration of Cs+ as well as Sr2+ varied about 2-fold, whereas its heritability ranged for both ions between 0.60 and 0.73. Shoot accumulation of Cs+ and Sr2+ could be compromised by increasing concentrations of their essential analogues K+ and Ca2+, respectively, causing a reduction of up to 80%. In the case of the segregating F2/F3 population Sq-1×Sorbo, this study identified several QTL for the trait Cs+ and Sr2+ accumulation, with main QTL on chromosomes 1 and 5. According to the correlation and discrimination surveys combined with QTL-analysis Cs+ and Sr2+ uptake seemed to be mediated mostly via non-selective cation channels. A polymorphism, affecting amino acids close to the K+-pore of one candidate, CYCLIC-NUCLEOTIDE-GATED CHANNEL 1 (CNGC1), was identified in Sorbo and associated with high Cs+ concentrating accessions. PMID:20624763

  8. Arabidopsis thaliana: A Model for the Study of Root and Shoot Gravitropism

    PubMed Central

    Masson, Patrick H.; Tasaka, Masao; Morita, Miyo T.; Guan, Changhui; Chen, Rujin; Boonsirichai, Kanokporn

    2002-01-01

    For most plants, shoots grow upward and roots grow downward. These growth patterns illustrate the ability for plant organs to guide their growth at a specified angle from the gravity vector (gravitropism). They allow shoots to grow upward toward light, where they can photosynthesize, and roots to grow downward into the soil, where they can anchor the plant as well as take up water and mineral ions. Gravitropism involves several steps organized in a specific response pathway. These include the perception of a gravistimulus (reorientation within the gravity field), the transduction of this mechanical stimulus into a physiological signal, the transmission of this signal from the site of sensing to the site of response, and a curvature-response which allows the organ tip to resume growth at a predefined set angle from the gravity vector. The primary sites for gravity sensing are located in the cap for roots, and in the endodermis for shoots. The curvature response occurs in the elongation zones for each organ. Upon gravistimulation, a gradient of auxin appears to be generated across the stimulated organ, and be transmitted to the site of response where it promotes a differential growth response. Therefore, while the gravity-induced auxin gradient has to be transmitted from the cap to the elongation zones in roots, there is no need for a longitudinal transport in shoots, as sites for gravity sensing and response overlap in this organ. A combination of molecular genetics, physiology, biochemistry and cell biology, coupled with the utilization of Arabidopsis thaliana as a model system, have recently allowed the identification of a number of molecules involved in the regulation of each phase of gravitropism in shoots and roots of higher plants. In this review, we attempt to summarize the results of these experiments, and we conclude by comparing the molecular and physiological mechanisms that underlie gravitropism in these organs. Abbreviations: GSPA: gravitational set

  9. Long-distance root-to-shoot transport of phytochelatins and cadmium in Arabidopsis.

    PubMed

    Gong, Ji-Ming; Lee, David A; Schroeder, Julian I

    2003-08-19

    Phytochelatin synthases (PCS) mediate cellular heavy-metal resistance in plants, fungi, and worms. However, phytochelatins (PCs) are generally considered to function as intracellular heavy-metal detoxification mechanisms, and whether long-distance transport of PCs occurs during heavy-metal detoxification remains unknown. Here, wheat TaPCS1 cDNA expression was either targeted to Arabidopsis roots with the Arabidopsis alcohol dehydrogenase (Adh) promoter (Adh::TaPCS1/cad1-3) or ectopically expressed with the cauliflower mosaic virus 35S promoter (35S::TaPCS1/cad1-3) in the PC-deficient mutant cad1-3. Adh::TaPCS1/cad1-3 and 35S::TaPCS1/cad1-3 complemented the cadmium, mercury, and arsenic sensitivities of the cad1-3 mutant. Northern blot, RT-PCR, and Western blot analyses showed Adh promoter-driven TaPCS1 expression only in roots and thus demonstrated lack of long-distance TaPCS1 mRNA and protein transport in plants. Fluorescence HPLC analyses showed that under Cd2+ stress, no PCs were detectable in cad1-3. However, in Adh::TaPCS1/cad1-3 plants, PCs were detected in roots and in rosette leaves and stems. Inductively coupled plasma atomic emission spectrometer analyses showed that either root-specific or ectopic expression of TaPCS1 significantly enhanced long-distance Cd2+ transport into stems and rosette leaves. Unexpectedly, transgenic expression of TaPCS1 reduced Cd2+ accumulation in roots compared with cad1-3. The reduced Cd2+ accumulation in roots and enhanced root-to-shoot Cd2+ transport in transgenic plants were abrogated by l-buthionine sulfoximine. The presented findings show that (i) transgenic expression of TaPCS1 suppresses the heavy-metal sensitivity of cad1-3, (ii) PCs can be transported from roots to shoots, and (iii) transgenic expression of the TaPCS1 gene increases long-distance root-to-shoot Cd2+ transport and reduces Cd2+ accumulation in roots. PMID:12909714

  10. Inhibition of auxin transport from the ovary or from the apical shoot induces parthenocarpic fruit-set in tomato mediated by gibberellins.

    PubMed

    Serrani, Juan Carlos; Carrera, Esther; Ruiz-Rivero, Omar; Gallego-Giraldo, Lina; Peres, Lázaro Eustáquio Pereira; García-Martínez, José Luis

    2010-06-01

    Fruit-set in tomato (Solanum lycopersicum) depends on gibberellins and auxins (GAs). Here, we show, using the cv MicroTom, that application of N-1-naphthylphthalamic acid (NPA; an inhibitor of auxin transport) to unpollinated ovaries induced parthenocarpic fruit-set, associated with an increase of indole-3-acetic acid (IAA) content, and that this effect was negated by paclobutrazol (an inhibitor of GA biosynthesis). NPA-induced ovaries contained higher content of GA(1) (an active GA) and transcripts of GA biosynthetic genes (SlCPS, SlGA20ox1, and -2). Interestingly, application of NPA to pollinated ovaries prevented their growth, potentially due to supraoptimal IAA accumulation. Plant decapitation and inhibition of auxin transport by NPA from the apical shoot also induced parthenocarpic fruit growth of unpollinated ovaries. Application of IAA to the severed stump negated the plant decapitation effect, indicating that the apical shoot prevents unpollinated ovary growth through IAA transport. Parthenocarpic fruit growth induced by plant decapitation was associated with high levels of GA(1) and was counteracted by paclobutrazol treatment. Plant decapitation also produced changes in transcript levels of genes encoding enzymes of GA biosynthesis (SlCPS and SlGA20ox1) in the ovary, quite similar to those found in NPA-induced fruits. All these results suggest that auxin can have opposing effects on fruit-set, either inducing (when accumulated in the ovary) or repressing (when transported from the apical shoot) that process, and that GAs act as mediators in both cases. The effect of NPA application and decapitation on fruit-set induction was also observed in MicroTom lines bearing introgressed DWARF and SELF-PRUNING wild-type alleles. PMID:20388661

  11. Inhibition of Auxin Transport from the Ovary or from the Apical Shoot Induces Parthenocarpic Fruit-Set in Tomato Mediated by Gibberellins1[C][W

    PubMed Central

    Serrani, Juan Carlos; Carrera, Esther; Ruiz-Rivero, Omar; Gallego-Giraldo, Lina; Peres, Lázaro Eustáquio Pereira; García-Martínez, José Luis

    2010-01-01

    Fruit-set in tomato (Solanum lycopersicum) depends on gibberellins and auxins (GAs). Here, we show, using the cv MicroTom, that application of N-1-naphthylphthalamic acid (NPA; an inhibitor of auxin transport) to unpollinated ovaries induced parthenocarpic fruit-set, associated with an increase of indole-3-acetic acid (IAA) content, and that this effect was negated by paclobutrazol (an inhibitor of GA biosynthesis). NPA-induced ovaries contained higher content of GA1 (an active GA) and transcripts of GA biosynthetic genes (SlCPS, SlGA20ox1, and -2). Interestingly, application of NPA to pollinated ovaries prevented their growth, potentially due to supraoptimal IAA accumulation. Plant decapitation and inhibition of auxin transport by NPA from the apical shoot also induced parthenocarpic fruit growth of unpollinated ovaries. Application of IAA to the severed stump negated the plant decapitation effect, indicating that the apical shoot prevents unpollinated ovary growth through IAA transport. Parthenocarpic fruit growth induced by plant decapitation was associated with high levels of GA1 and was counteracted by paclobutrazol treatment. Plant decapitation also produced changes in transcript levels of genes encoding enzymes of GA biosynthesis (SlCPS and SlGA20ox1) in the ovary, quite similar to those found in NPA-induced fruits. All these results suggest that auxin can have opposing effects on fruit-set, either inducing (when accumulated in the ovary) or repressing (when transported from the apical shoot) that process, and that GAs act as mediators in both cases. The effect of NPA application and decapitation on fruit-set induction was also observed in MicroTom lines bearing introgressed DWARF and SELF-PRUNING wild-type alleles. PMID:20388661

  12. Multi-layered Regulation of SPL15 and Cooperation with SOC1 Integrate Endogenous Flowering Pathways at the Arabidopsis Shoot Meristem.

    PubMed

    Hyun, Youbong; Richter, René; Vincent, Coral; Martinez-Gallegos, Rafael; Porri, Aimone; Coupland, George

    2016-05-01

    Flowering is initiated in response to environmental and internal cues that are integrated at the shoot apical meristem (SAM). We show that SPL15 coordinates the basal floral promotion pathways required for flowering of Arabidopsis in non-inductive environments. SPL15 directly activates transcription of the floral regulators FUL and miR172b in the SAM during floral induction, whereas its paralog SPL9 is expressed later on the flanks of the SAM. The capacity of SPL15 to promote flowering is regulated by age through miR156, which targets SPL15 mRNA, and gibberellin (GA), which releases SPL15 from DELLAs. Furthermore, SPL15 and the MADS-box protein SOC1 cooperate to promote transcription of their target genes. SPL15 recruits RNAPII and MED18, a Mediator complex component, in a GA-dependent manner, while SOC1 facilitates active chromatin formation with the histone demethylase REF6. Thus, we present a molecular basis for assimilation of flowering signals and transcriptional control at the SAM during flowering. PMID:27134142

  13. Transcriptional profiling of Arabidopsis root hairs and pollen defines an apical cell growth signature

    PubMed Central

    2014-01-01

    Background Current views on the control of cell development are anchored on the notion that phenotypes are defined by networks of transcriptional activity. The large amounts of information brought about by transcriptomics should allow the definition of these networks through the analysis of cell-specific transcriptional signatures. Here we test this principle by applying an analogue to comparative anatomy at the cellular level, searching for conserved transcriptional signatures, or conserved small gene-regulatory networks (GRNs) on root hairs (RH) and pollen tubes (PT), two filamentous apical growing cells that are a striking example of conservation of structure and function in plants. Results We developed a new method for isolation of growing and mature root hair cells, analysed their transcriptome by microarray analysis, and further compared it with pollen and other single cell transcriptomics data. Principal component analysis shows a statistical relation between the datasets of RHs and PTs which is suggestive of a common transcriptional profile pattern for the apical growing cells in a plant, with overlapping profiles and clear similarities at the level of small GTPases, vesicle-mediated transport and various specific metabolic responses. Furthermore, cis-regulatory element analysis of co-regulated genes between RHs and PTs revealed conserved binding sequences that are likely required for the expression of genes comprising the apical signature. This included a significant occurrence of motifs associated to a defined transcriptional response upon anaerobiosis. Conclusions Our results suggest that maintaining apical growth mechanisms synchronized with energy yielding might require a combinatorial network of transcriptional regulation. We propose that this study should constitute the foundation for further genetic and physiological dissection of the mechanisms underlying apical growth of plant cells. PMID:25080170

  14. Identification of a Stelar-Localized Transport Protein That Facilitates Root-to-Shoot Transfer of Chloride in Arabidopsis.

    PubMed

    Li, Bo; Byrt, Caitlin; Qiu, Jiaen; Baumann, Ute; Hrmova, Maria; Evrard, Aurelie; Johnson, Alexander A T; Birnbaum, Kenneth D; Mayo, Gwenda M; Jha, Deepa; Henderson, Sam W; Tester, Mark; Gilliham, Mathew; Roy, Stuart J

    2016-02-01

    Under saline conditions, higher plants restrict the accumulation of chloride ions (Cl(-)) in the shoot by regulating their transfer from the root symplast into the xylem-associated apoplast. To identify molecular mechanisms underpinning this phenomenon, we undertook a transcriptional screen of salt stressed Arabidopsis (Arabidopsis thaliana) roots. Microarrays, quantitative RT-PCR, and promoter-GUS fusions identified a candidate gene involved in Cl(-) xylem loading from the Nitrate transporter 1/Peptide Transporter family (NPF2.4). This gene was highly expressed in the root stele compared to the cortex, and its expression decreased after exposure to NaCl or abscisic acid. NPF2.4 fused to fluorescent proteins, expressed either transiently or stably, was targeted to the plasma membrane. Electrophysiological analysis of NPF2.4 in Xenopus laevis oocytes suggested that NPF2.4 catalyzed passive Cl(-) efflux out of cells and was much less permeable to NO3(-). Shoot Cl(-) accumulation was decreased following NPF2.4 artificial microRNA knockdown, whereas it was increased by overexpression of NPF2.4. Taken together, these results suggest that NPF2.4 is involved in long-distance transport of Cl(-) in plants, playing a role in the loading and the regulation of Cl(-) loading into the xylem of Arabidopsis roots during salinity stress. PMID:26662602

  15. Shoot branching.

    PubMed

    Ward, Sally P; Leyser, Ottoline

    2004-02-01

    The mature form of a plant shoot system is an expression of several genetically controlled traits, many of which are also environmentally regulated. A major component of this architectural variation is the degree of shoot branching. Recent results indicate conserved mechanisms for shoot branch development across the monocots and eudicots. The existence of a novel long-range branch-inhibiting signal has been inferred from studies of branching mutants in pea and Arabidopsis. PMID:14732444

  16. A Nitrogen-Regulated Glutamine Amidotransferase (GAT1_2.1) Represses Shoot Branching in Arabidopsis[C][W

    PubMed Central

    Zhu, Huifen; Kranz, Robert G.

    2012-01-01

    Shoot branching in plants is regulated by many environmental cues and by specific hormones such as strigolactone (SL). We show that the GAT1_2.1 gene (At1g15040) is repressed over 50-fold by nitrogen stress, and is also involved in branching control. At1g15040 is predicted to encode a class I glutamine amidotransferase (GAT1), a superfamily for which Arabidopsis (Arabidopsis thaliana) has 30 potential members. Most members can be categorized into known biosynthetic pathways, for the amidation of known acceptor molecules (e.g. CTP synthesis). Some members, like GAT1_2.1, are of unknown function, likely involved in amidation of unknown acceptors. A gat1_2.1 mutant exhibits a significant increase in shoot branching, similar to mutants in SL biosynthesis. The results suggest that GAT1_2.1 is not involved in SL biosynthesis since exogenously applied GR24 (a synthetic SL) does not correct the mutant phenotype. The subfamily of GATs (GATase1_2), with At1g15040 as the founding member, appears to be present in all plants (including mosses), but not other organisms. This suggests a plant-specific function such as branching control. We discuss the possibility that the GAT1_2.1 enzyme may activate SLs (e.g. GR24) by amidation, or more likely could embody a new pathway for repression of branching. PMID:22885937

  17. Metabolism and Biological Activity of Gibberellin A4 in Vegetative Shoots of Zea mays, Oryza sativa, and Arabidopsis thaliana.

    PubMed Central

    Kobayashi, M.; Gaskin, P.; Spray, C. R.; Suzuki, Y.; Phinney, B. O.; MacMillan, J.

    1993-01-01

    [17-13C,3H]Gibberellin A4 (GA4) was injected into the shoots of tall (W23/L317), dwarf-1 (d1), and dwarf-5 (d5) Zea mays L. (maize); tall (cv Nipponbare), dwarf-x (dx), and dwarf-y (dy) Oryza sativa L. (rice); and tall (ecotype Landsberg erecta), ga4, and ga5 Arabidopsis thaliana (L.) Heynh. [13C]GA4 and its metabolites were identified from the shoots by full-scan gas chromatography-mass spectrometry and Kovats retention indices. GA4 was metabolized to GA1 in all nine genotypes. GA4 was also metabolized in some of the genotypes to 3-epi-GA1, GA2, 2[beta]-OH-GA2, 3-epi-GA2, endo-GA4, 16[alpha], 17-H2-16, 17-(OH)2-GA4, GA34, endo-GA34, GA58, 15-epi-GA63, GA71, and 16-epi-GA82. No evidence was found for the metabolism of GA4 to GA7 or of GA4 to GA3. The bioactivities of GA4 and GA1 were determined using the six dwarf mutants for assay. GA4 and GA1 had similar activities for the maize and rice mutants. For the Arabidopsis mutants, GA4 was more active than GA1 at low dosages; GA4 was less active than GA1 at higher dosages. PMID:12231829

  18. Transcriptomic Analysis of Soil-Grown Arabidopsis thaliana Roots and Shoots in Response to a Drought Stress.

    PubMed

    Rasheed, Sultana; Bashir, Khurram; Matsui, Akihiro; Tanaka, Maho; Seki, Motoaki

    2016-01-01

    Drought stress has a negative impact on crop yield. Thus, understanding the molecular mechanisms responsible for plant drought stress tolerance is essential for improving this beneficial trait in crops. In the current study, a transcriptional analysis was conducted of gene regulatory networks in roots of soil-grown Arabidopsis plants in response to a drought stress treatment. A microarray analysis of drought-stressed roots and shoots was performed at 0, 1, 3, 5, 7, and 9 days. Results indicated that the expression of many drought stress-responsive genes and abscisic acid biosynthesis-related genes was differentially regulated in roots and shoots from days 3 to 9. The expression of cellular and metabolic process-related genes was up-regulated at an earlier time-point in roots than in shoots. In this regard, the expression of genes involved in oxidative signaling, chromatin structure, and cell wall modification also increased significantly in roots compared to shoots. Moreover, the increased expression of genes involved in the transport of amino acids and other solutes; including malate, iron, and sulfur, was observed in roots during the early time points following the initiation of the drought stress. These data suggest that plants may utilize these signaling channels and metabolic adjustments as adaptive responses in the early stages of a drought stress. Collectively, the results of the present study increases our understanding of the differences pertaining to the molecular mechanisms occurring in roots vs. shoots in response to a drought stress. Furthermore, these findings also aid in the selection of novel genes and promoters that can be used to potentially produce crop plants with increased drought tolerance. PMID:26941754

  19. Transcriptomic Analysis of Soil-Grown Arabidopsis thaliana Roots and Shoots in Response to a Drought Stress

    PubMed Central

    Rasheed, Sultana; Bashir, Khurram; Matsui, Akihiro; Tanaka, Maho; Seki, Motoaki

    2016-01-01

    Drought stress has a negative impact on crop yield. Thus, understanding the molecular mechanisms responsible for plant drought stress tolerance is essential for improving this beneficial trait in crops. In the current study, a transcriptional analysis was conducted of gene regulatory networks in roots of soil-grown Arabidopsis plants in response to a drought stress treatment. A microarray analysis of drought-stressed roots and shoots was performed at 0, 1, 3, 5, 7, and 9 days. Results indicated that the expression of many drought stress-responsive genes and abscisic acid biosynthesis-related genes was differentially regulated in roots and shoots from days 3 to 9. The expression of cellular and metabolic process-related genes was up-regulated at an earlier time-point in roots than in shoots. In this regard, the expression of genes involved in oxidative signaling, chromatin structure, and cell wall modification also increased significantly in roots compared to shoots. Moreover, the increased expression of genes involved in the transport of amino acids and other solutes; including malate, iron, and sulfur, was observed in roots during the early time points following the initiation of the drought stress. These data suggest that plants may utilize these signaling channels and metabolic adjustments as adaptive responses in the early stages of a drought stress. Collectively, the results of the present study increases our understanding of the differences pertaining to the molecular mechanisms occurring in roots vs. shoots in response to a drought stress. Furthermore, these findings also aid in the selection of novel genes and promoters that can be used to potentially produce crop plants with increased drought tolerance. PMID:26941754

  20. Complexation of Arsenite with Phytochelatins Reduces Arsenite Efflux and Translocation from Roots to Shoots in Arabidopsis1[W

    PubMed Central

    Liu, Wen-Ju; Wood, B. Alan; Raab, Andrea; McGrath, Steve P.; Zhao, Fang-Jie; Feldmann, Jörg

    2010-01-01

    Complexation of arsenite [As(III)] with phytochelatins (PCs) is an important mechanism employed by plants to detoxify As; how this complexation affects As mobility was little known. We used high-resolution inductively coupled plasma-mass spectrometry and accurate mass electrospray ionization-mass spectrometry coupled to HPLC to identify and quantify As(III)-thiol complexes and free thiol compounds in Arabidopsis (Arabidopsis thaliana) exposed to arsenate [As(V)]. As(V) was efficiently reduced to As(III) in roots. In wild-type roots, 69% of As was complexed as As(III)-PC4, As(III)-PC3, and As(III)-(PC2)2. Both the glutathione (GSH)-deficient mutant cad2-1 and the PC-deficient mutant cad1-3 were approximately 20 times more sensitive to As(V) than the wild type. In cad1-3 roots, only 8% of As was complexed with GSH as As(III)-(GS)3 and no As(III)-PCs were detected, while in cad2-1 roots, As(III)-PCs accounted for only 25% of the total As. The two mutants had a greater As mobility, with a significantly higher accumulation of As(III) in shoots and 4.5 to 12 times higher shoot-to-root As concentration ratio than the wild type. Roots also effluxed a substantial proportion of the As(V) taken up as As(III) to the external medium, and this efflux was larger in the two mutants. Furthermore, when wild-type plants were exposed to l-buthionine sulfoximine or deprived of sulfur, both As(III) efflux and root-to-shoot translocation were enhanced. The results indicate that complexation of As(III) with PCs in Arabidopsis roots decreases its mobility for both efflux to the external medium and for root-to-shoot translocation. Enhancing PC synthesis in roots may be an effective strategy to reduce As translocation to the edible organs of food crops. PMID:20130102

  1. Systemic above- and belowground cross talk: hormone-based responses triggered by Heterodera schachtii and shoot herbivores in Arabidopsis thaliana

    PubMed Central

    Kammerhofer, Nina; Egger, Barbara; Dobrev, Petre; Vankova, Radomira; Hofmann, Julia; Schausberger, Peter; Wieczorek, Krzysztof

    2015-01-01

    Above- and belowground plant parts are simultaneously attacked by different pests and pathogens. The host mediates these interactions and physiologically reacts, e.g. with local and systemic alterations of endogenous hormone levels coupled with coordinated transcriptional changes. This in turn affects attractiveness and susceptibility of the plant to subsequent attackers. Here, the model plant Arabidopsis thaliana is used to study stress hormone-based systemic responses triggered by simultaneous root parasitism by the cyst nematode Heterodera schachtii and shoot herbivory by the thrips Frankliniella occidentalis and the spider mite Tetranychus urticae. First, HPLC/MS and quantitative reverse transcriptase PCR are used to show that nematode parasitism strongly affects stress hormone levels and expression of hormone marker genes in shoots. Previous nematode infection is then demonstrated to affect the behavioural and life history performance of both arthropods. While thrips explicitly avoid nematode-infected plants, spider mites prefer them. In addition, the life history performance of T. urticae is significantly enhanced by nematode infection. Finally, systemic changes triggered by shoot-feeding F. occidentalis but not T. urticae are shown to make the roots more attractive for H. schachtii. This work emphasises the importance of above- and belowground signalling and contributes to a better understanding of plant systemic defence mechanisms against plant-parasitic nematodes. PMID:26324462

  2. Systemic above- and belowground cross talk: hormone-based responses triggered by Heterodera schachtii and shoot herbivores in Arabidopsis thaliana.

    PubMed

    Kammerhofer, Nina; Egger, Barbara; Dobrev, Petre; Vankova, Radomira; Hofmann, Julia; Schausberger, Peter; Wieczorek, Krzysztof

    2015-12-01

    Above- and belowground plant parts are simultaneously attacked by different pests and pathogens. The host mediates these interactions and physiologically reacts, e.g. with local and systemic alterations of endogenous hormone levels coupled with coordinated transcriptional changes. This in turn affects attractiveness and susceptibility of the plant to subsequent attackers. Here, the model plant Arabidopsis thaliana is used to study stress hormone-based systemic responses triggered by simultaneous root parasitism by the cyst nematode Heterodera schachtii and shoot herbivory by the thrips Frankliniella occidentalis and the spider mite Tetranychus urticae. First, HPLC/MS and quantitative reverse transcriptase PCR are used to show that nematode parasitism strongly affects stress hormone levels and expression of hormone marker genes in shoots. Previous nematode infection is then demonstrated to affect the behavioural and life history performance of both arthropods. While thrips explicitly avoid nematode-infected plants, spider mites prefer them. In addition, the life history performance of T. urticae is significantly enhanced by nematode infection. Finally, systemic changes triggered by shoot-feeding F. occidentalis but not T. urticae are shown to make the roots more attractive for H. schachtii. This work emphasises the importance of above- and belowground signalling and contributes to a better understanding of plant systemic defence mechanisms against plant-parasitic nematodes. PMID:26324462

  3. High temperature attenuates the gravitropism of inflorescence stems by inducing SHOOT GRAVITROPISM 5 alternative splicing in Arabidopsis.

    PubMed

    Kim, Joo-Young; Ryu, Jae Yong; Baek, Kon; Park, Chung-Mo

    2016-01-01

    In higher plants, gravitropism proceeds through three sequential steps in the responding organs: perception of gravity signals, signal transduction and asymmetric cell elongation. Light and temperature also influence the gravitropic orientation of plant organs. A series of Arabidopsis shoot gravitropism (sgr) mutants has been shown to exhibit disturbed shoot gravitropism. SGR5 is functionally distinct from other SGR members in that it mediates the early events of gravitropic responses in inflorescence stems. Here, we demonstrated that SGR5 alternative splicing produces two protein variants (SGR5α and SGR5β) in modulating the gravitropic response of inflorescence stems at high temperatures. SGR5β inhibits SGR5α function by forming non-DNA-binding heterodimers. Transgenic plants overexpressing SGR5β (35S:SGR5β) exhibit reduced gravitropic growth of inflorescence stems, as observed in the SGR5-deficient sgr5-5 mutant. Interestingly, SGR5 alternative splicing is accelerated at high temperatures, resulting in the high-level accumulation of SGR5β transcripts. When plants were exposed to high temperatures, whereas gravitropic curvature was reduced in Col-0 inflorescence stems, it was uninfluenced in the inflorescence stems of 35S:SGR5β transgenic plants and sgr5-5 mutant. We propose that the thermoresponsive alternative splicing of SGR5 provides an adaptation strategy by which plants protect the shoots from hot air under high temperature stress in natural habitats. PMID:26256266

  4. Root-shoot interactions explain the reduction of leaf mineral content in Arabidopsis plants grown under elevated [CO2 ] conditions.

    PubMed

    Jauregui, Ivan; Aparicio-Tejo, Pedro M; Avila, Concepción; Cañas, Rafael; Sakalauskiene, Sandra; Aranjuelo, Iker

    2016-09-01

    Although shoot N depletion in plants exposed to elevated [CO2 ] has already been reported on several occasions, some uncertainty remains about the mechanisms involved. This study illustrates (1) the importance of characterizing root-shoot interactions and (2) the physiological, biochemical and gene expression mechanisms adopted by nitrate-fed Arabidopsis thaliana plants grown under elevated [CO2 ]. Elevated [CO2 ] increases biomass and photosynthetic rates; nevertheless, the decline in total soluble protein, Rubisco and leaf N concentrations revealed a general decrease in leaf N availability. A transcriptomic approach (conducted at the root and shoot level) revealed that exposure to 800 ppm [CO2 ] induced the expression of genes involved in the transport of nitrate and mineral elements. Leaf N and mineral status revealed that N assimilation into proteins was constrained under elevated [CO2 ]. Moreover, this study also highlights how elevated [CO2 ] induced the reorganization of nitrate assimilation between tissues; root nitrogen assimilation was favored over leaf assimilation to offset the decline in nitrogen metabolism in the leaves of plants exposed to elevated [CO2 ]. PMID:26801348

  5. Quantitative analysis of live-cell growth at the shoot apex of Arabidopsis thaliana: algorithms for feature measurement and temporal alignment.

    PubMed

    Tataw, Oben M; Reddy, G Venugopala; Keogh, Eamonn J; Roy-Chowdhury, Amit K

    2013-01-01

    Study of the molecular control of organ growth requires establishment of the causal relationship between gene expression and cell behaviors. We seek to understand this relationship at the shoot apical meristem (SAM) of model plant Arabidopsis thaliana. This requires the spatial mapping and temporal alignment of different functional domains into a single template. Live-cell imaging techniques allow us to observe real-time organ primordia growth and gene expression dynamics at cellular resolution. In this paper, we propose a framework for the measurement of growth features at the 3D reconstructed surface of organ primordia, as well as algorithms for robust time alignment of primordia. We computed areas and deformation values from reconstructed 3D surfaces of individual primordia from live-cell imaging data. Based on these growth measurements, we applied a multiple feature landscape matching (LAM-M) algorithm to ensure a reliable temporal alignment of multiple primordia. Although the original landscape matching (LAM) algorithm motivated our alignment approach, it sometimes fails to properly align growth curves in the presence of high noise/distortion. To overcome this shortcoming, we modified the cost function to consider the landscape of the corresponding growth features. We also present an alternate parameter-free growth alignment algorithm which performs as well as LAM-M for high-quality data, but is more robust to the presence of outliers or noise. Results on primordia and guppy evolutionary growth data show that the proposed alignment framework performs at least as well as the LAM algorithm in the general case, and significantly better in the case of increased noise. PMID:24384704

  6. Overexpression of Arabidopsis phytochelatin synthase in tobacco plants enhances Cd(2+) tolerance and accumulation but not translocation to the shoot.

    PubMed

    Pomponi, Mirella; Censi, Vincenzo; Di Girolamo, Valentina; De Paolis, Angelo; di Toppi, Luigi Sanità; Aromolo, Rita; Costantino, Paolo; Cardarelli, Maura

    2006-01-01

    Phytochelatins (PCs) are metal binding peptides involved in heavy metal detoxification. To assess whether enhanced phytochelatin synthesis would increase heavy metal tolerance and accumulation in plants, we overexpressed the Arabidopsis phytochelatin synthase gene (AtPCS1) in the non-accumulator plant Nicotiana tabacum. Wild-type plants and plants harbouring the Agrobacterium rhizogenes rolB oncogene were transformed with a 35S AtPCS1 construct. Root cultures from rolB plants could be easily established and we demonstrated here that they represent a reliable system to study heavy metal tolerance. Cd(2+) tolerance in cultured rolB roots was increased as a result of overexpression of AtPCS1, and further enhanced when reduced glutathione (GSH, the substrate of PCS1) was added to the culture medium. Accordingly, HPLC analysis showed that total PC production in PCS1-overexpressing rolB roots was higher than in rolB roots in the presence of GSH. Overexpression of AtPCS1 in whole seedlings led to a twofold increase in Cd(2+) accumulation in the roots and shoots of both rolB and wild-type seedlings. Similarly, a significant increase in Cd(2+) accumulation linked to a higher production of PCs in both roots and shoots was observed in adult plants. However, the percentage of Cd(2+) translocated to the shoots of seedlings and adult overexpressing plants was unaffected. We conclude that the increase in Cd(2+) tolerance and accumulation of PCS1 overexpressing plants is directly related to the availability of GSH, while overexpression of phytochelatin synthase does not enhance long distance root-to-shoot Cd(2+) transport. PMID:16133212

  7. Comparative proteomic analysis of the shoot apical meristem in maize between a ZmCCT-associated near-isogenic line and its recurrent parent.

    PubMed

    Wu, Liuji; Wang, Xintao; Wang, Shunxi; Wu, Liancheng; Tian, Lei; Tian, Zhiqiang; Liu, Ping; Chen, Yanhui

    2016-01-01

    The ZmCCT, one of the most important genes affecting photoperiod response, delays flowering under long-day conditions in maize (Zea mays). In this study we used the isobaric tags for relative and absolute quantification (iTRAQ) technique-based proteomics approach to identify differentially expressed proteins between a near-isogenic line (NIL) and its recurrent parent, contrasting in alleles of ZmCCT. A total of 5,259 distinct proteins were identified. Among them, 386 proteins were differentially expressed between NIL-cml line (ZmCCT-positive) and H4 line (ZmCCT-negative). Functional categorization showed that the differentially proteins were mainly involved in energy production, photosynthesis, signal transduction, and cell organization and biogenesis. Our results showed that during shoot apical meristem (SAM) development cell division proteins, carbohydrate metabolism-related proteins, and flower inhibition-related proteins were more abundant in the ZmCCT-positive line than the ZmCCT-negative line. These results, taken together with morphological observations, showed that the effect of ZmCCT on flowering might be caused by its effect on one or all of these biological processes. Although the exact roles of these putative related proteins remain to be examined, our results obtained using the proteomics approach lead to a better understanding of the photoperiodicity mechanism in maize plants. PMID:27468931

  8. Global Transcriptome Profiling of Developing Leaf and Shoot Apices Reveals Distinct Genetic and Environmental Control of Floral Transition and Inflorescence Development in Barley[OPEN

    PubMed Central

    2015-01-01

    Timing of the floral transition and inflorescence development strongly affect yield in barley (Hordeum vulgare). Therefore, we examined the effects of daylength and the photoperiod response gene PHOTOPERIOD1 (Ppd-H1) on barley development and analyzed gene expression changes in the developing leaves and main shoot apices (MSAs) of barley by RNA sequencing. The daylength sensitivity of MSA development had two phases, floret primordia initiated under long and short days, whereas successful inflorescence development occurred only under long days. The transcripts associated with floral transition were largely regulated independently of photoperiod and allelic variation at Ppd-H1. The photoperiod- and Ppd-H1-dependent differences in inflorescence development and flower fertility were associated with the induction of barley FLOWERING LOCUS T orthologs: FT1 in leaves and FT2 in MSAs. FT1 expression was coregulated with transcripts involved in nutrient transport, carbohydrate metabolism, and cell cycle regulation, suggesting that FT1 might alter source-sink relationships. Successful inflorescence development correlated with upregulation of FT2 and transcripts related to floral organ development, phytohormones, and cell cycle regulation. Identification of photoperiod and stage-specific transcripts gives insights into the regulation of reproductive development in barley and provides a resource for investigation of the complexities of development and yield in temperate grasses. PMID:26307377

  9. Comparative proteomic analysis of the shoot apical meristem in maize between a ZmCCT-associated near-isogenic line and its recurrent parent

    PubMed Central

    Wu, Liuji; Wang, Xintao; Wang, Shunxi; Wu, Liancheng; Tian, Lei; Tian, Zhiqiang; Liu, Ping; Chen, Yanhui

    2016-01-01

    The ZmCCT, one of the most important genes affecting photoperiod response, delays flowering under long-day conditions in maize (Zea mays). In this study we used the isobaric tags for relative and absolute quantification (iTRAQ) technique-based proteomics approach to identify differentially expressed proteins between a near-isogenic line (NIL) and its recurrent parent, contrasting in alleles of ZmCCT. A total of 5,259 distinct proteins were identified. Among them, 386 proteins were differentially expressed between NIL-cml line (ZmCCT-positive) and H4 line (ZmCCT-negative). Functional categorization showed that the differentially proteins were mainly involved in energy production, photosynthesis, signal transduction, and cell organization and biogenesis. Our results showed that during shoot apical meristem (SAM) development cell division proteins, carbohydrate metabolism–related proteins, and flower inhibition-related proteins were more abundant in the ZmCCT-positive line than the ZmCCT-negative line. These results, taken together with morphological observations, showed that the effect of ZmCCT on flowering might be caused by its effect on one or all of these biological processes. Although the exact roles of these putative related proteins remain to be examined, our results obtained using the proteomics approach lead to a better understanding of the photoperiodicity mechanism in maize plants. PMID:27468931

  10. Shoot Na+ Exclusion and Increased Salinity Tolerance Engineered by Cell Type–Specific Alteration of Na+ Transport in Arabidopsis[W][OA

    PubMed Central

    Møller, Inge S.; Gilliham, Matthew; Jha, Deepa; Mayo, Gwenda M.; Roy, Stuart J.; Coates, Juliet C.; Haseloff, Jim; Tester, Mark

    2009-01-01

    Soil salinity affects large areas of cultivated land, causing significant reductions in crop yield globally. The Na+ toxicity of many crop plants is correlated with overaccumulation of Na+ in the shoot. We have previously suggested that the engineering of Na+ exclusion from the shoot could be achieved through an alteration of plasma membrane Na+ transport processes in the root, if these alterations were cell type specific. Here, it is shown that expression of the Na+ transporter HKT1;1 in the mature root stele of Arabidopsis thaliana decreases Na+ accumulation in the shoot by 37 to 64%. The expression of HKT1;1 specifically in the mature root stele is achieved using an enhancer trap expression system for specific and strong overexpression. The effect in the shoot is caused by the increased influx, mediated by HKT1;1, of Na+ into stelar root cells, which is demonstrated in planta and leads to a reduction of root-to-shoot transfer of Na+. Plants with reduced shoot Na+ also have increased salinity tolerance. By contrast, plants constitutively expressing HKT1;1 driven by the cauliflower mosaic virus 35S promoter accumulated high shoot Na+ and grew poorly. Our results demonstrate that the modification of a specific Na+ transport process in specific cell types can reduce shoot Na+ accumulation, an important component of salinity tolerance of many higher plants. PMID:19584143

  11. Root and shoot performance of Arabidopsis thaliana exposed to elevated CO2: A physiologic, metabolic and transcriptomic response.

    PubMed

    Jauregui, Iván; Aparicio-Tejo, Pedro M; Avila, Concepción; Rueda-López, Marina; Aranjuelo, Iker

    2015-09-15

    The responsiveness of C3 plants to raised atmospheric [CO2] levels has been frequently described as constrained by photosynthetic downregulation. The main goal of the current study was to characterize the shoot-root relationship and its implications in plant responsiveness under elevated [CO2] conditions. For this purpose, Arabidopsis thaliana plants were exposed to elevated [CO2] (800ppm versus 400ppm [CO2]) and fertilized with a mixed (NH4NO3) nitrogen source. Plant growth, physiology, metabolite and transcriptomic characterizations were carried out at the root and shoot levels. Plant growth under elevated [CO2] conditions was doubled due to increased photosynthetic rates and gas exchange measurements revealed that these plants maintain higher photosynthetic rates over extended periods of time. This positive response of photosynthetic rates to elevated [CO2] was caused by the maintenance of leaf protein and Rubisco concentrations at control levels alongside enhanced energy efficiency. The increased levels of leaf carbohydrates, organic acids and amino acids supported the augmented respiration rates of plants under elevated [CO2]. A transcriptomic analysis allowed the identification of photoassimilate allocation and remobilization as fundamental process used by the plants to maintain the outstanding photosynthetic performance. Moreover, based on the relationship between plant carbon status and hormone functioning, the transcriptomic analyses provided an explanation of why phenology accelerates under elevated [CO2] conditions. PMID:26519814

  12. Two-Step Regulation of a Meristematic Cell Population Acting in Shoot Branching in Arabidopsis.

    PubMed

    Shi, Bihai; Zhang, Cui; Tian, Caihuan; Wang, Jin; Wang, Quan; Xu, Tengfei; Xu, Yan; Ohno, Carolyn; Sablowski, Robert; Heisler, Marcus G; Theres, Klaus; Wang, Ying; Jiao, Yuling

    2016-07-01

    Shoot branching requires the establishment of new meristems harboring stem cells; this phenomenon raises questions about the precise regulation of meristematic fate. In seed plants, these new meristems initiate in leaf axils to enable lateral shoot branching. Using live-cell imaging of leaf axil cells, we show that the initiation of axillary meristems requires a meristematic cell population continuously expressing the meristem marker SHOOT MERISTEMLESS (STM). The maintenance of STM expression depends on the leaf axil auxin minimum. Ectopic expression of STM is insufficient to activate axillary buds formation from plants that have lost leaf axil STM expressing cells. This suggests that some cells undergo irreversible commitment to a developmental fate. In more mature leaves, REVOLUTA (REV) directly up-regulates STM expression in leaf axil meristematic cells, but not in differentiated cells, to establish axillary meristems. Cell type-specific binding of REV to the STM region correlates with epigenetic modifications. Our data favor a threshold model for axillary meristem initiation, in which low levels of STM maintain meristematic competence and high levels of STM lead to meristem initiation. PMID:27398935

  13. Two-Step Regulation of a Meristematic Cell Population Acting in Shoot Branching in Arabidopsis

    PubMed Central

    Tian, Caihuan; Wang, Jin; Xu, Tengfei; Xu, Yan; Ohno, Carolyn; Sablowski, Robert; Heisler, Marcus G.; Theres, Klaus; Wang, Ying

    2016-01-01

    Shoot branching requires the establishment of new meristems harboring stem cells; this phenomenon raises questions about the precise regulation of meristematic fate. In seed plants, these new meristems initiate in leaf axils to enable lateral shoot branching. Using live-cell imaging of leaf axil cells, we show that the initiation of axillary meristems requires a meristematic cell population continuously expressing the meristem marker SHOOT MERISTEMLESS (STM). The maintenance of STM expression depends on the leaf axil auxin minimum. Ectopic expression of STM is insufficient to activate axillary buds formation from plants that have lost leaf axil STM expressing cells. This suggests that some cells undergo irreversible commitment to a developmental fate. In more mature leaves, REVOLUTA (REV) directly up-regulates STM expression in leaf axil meristematic cells, but not in differentiated cells, to establish axillary meristems. Cell type-specific binding of REV to the STM region correlates with epigenetic modifications. Our data favor a threshold model for axillary meristem initiation, in which low levels of STM maintain meristematic competence and high levels of STM lead to meristem initiation. PMID:27398935

  14. Auxin can act independently of CRC, LUG, SEU, SPT and STY1 in style development but not apical-basal patterning of the Arabidopsis gynoecium.

    PubMed

    Ståldal, Veronika; Sohlberg, Joel J; Eklund, D Magnus; Ljung, Karin; Sundberg, Eva

    2008-01-01

    Patterning of the Arabidopsis thaliana gynoecium is dependent on the localization and concentration of the plant hormone auxin and it has been previously reported that STYLISH1 (STY1) activates transcription of the auxin biosynthesis gene YUCCA4 (YUC4) and affects gynoecium development. Here, the relationship between auxin, STY1 and other regulators of gynoecium development was examined. Exogenous auxin in droplets of lanolin paste were applied to young gynoecia; auxin biosynthesis rate was measured and STY1 overexpression or chemically mediated polar auxin transport (PAT) inhibition were induced in various mutants. The style phenotype of sty1-1sty2-1 mutants was restored by exogenous application of auxin, and STY1 over-activation resulted in an elevated auxin biosynthesis rate. Both over-activation of STY1 and inhibition of PAT restored the stylar defects of several unrelated mutants, but with regard to gynoecium apical-basal patterning the mutants responded differently to inhibition of PAT. These results suggest that reduced auxin concentrations cause the sty1-1 sty2-1 phenotype, that STY1 induces auxin biosynthesis, that elevated apical auxin concentrations can compensate for the loss of several style-promoting factors, and that auxin may act downstream of, or in parallel with these during style development but is dependent on their action in apical-basal patterning. PMID:18811619

  15. Jasmonate-Activated MYC2 Represses ETHYLENE INSENSITIVE3 Activity to Antagonize Ethylene-Promoted Apical Hook Formation in Arabidopsis[C][W

    PubMed Central

    Zhang, Xing; Zhu, Ziqiang; An, Fengying; Hao, Dongdong; Li, Pengpeng; Song, Jinghui; Yi, Chengqi; Guo, Hongwei

    2014-01-01

    The apical hook is an essential structure that enables epigeal plants to protrude through the soil. Arabidopsis thaliana HOOKLESS1 (HLS1) is reported to be a key regulator of hook development and a direct target gene of the ethylene (ET)-activated transcription factors ETHYLENE INSENSITIVE3 (EIN3) and its close homolog EIN3-Like1. Previous research has shown that the phytohormones jasmonate (JA) and ET antagonistically regulate apical hook development, although the underlying molecular mechanism is largely unknown. Here, we report that JA represses hook formation by reducing HLS1 expression. Our results further reveal that the JA-activated transcription factor MYC2 represses EIN3 function to reduce HLS1 expression through at least the following two layers of regulation: (1) MYC2 binds to the promoter of an F-box gene, EIN3 BINDING F-BOX PROTEIN1, to induce its expression and thus promote EIN3 degradation; and (2) MYC2 physically interacts with EIN3 and inhibits its DNA binding activity. Collectively, our findings shed light on the molecular mechanism underlying the antagonism between JA and ET during apical hook development and provide insight into the coaction of multiple phytohormones in the regulation of plant growth and development. PMID:24668749

  16. Vacuolar Ca2+/H+ Transport Activity Is Required for Systemic Phosphate Homeostasis Involving Shoot-to-Root Signaling in Arabidopsis1[W][OA

    PubMed Central

    Liu, Tzu-Yin; Aung, Kyaw; Tseng, Ching-Ying; Chang, Tzu-Yun; Chen, Ying-Shin; Chiou, Tzyy-Jen

    2011-01-01

    Calcium ions (Ca2+) and Ca2+-related proteins mediate a wide array of downstream processes involved in plant responses to abiotic stresses. In Arabidopsis (Arabidopsis thaliana), disruption of the vacuolar Ca2+/H+ transporters CAX1 and CAX3 causes notable alterations in the shoot ionome, including phosphate (Pi) content. In this study, we showed that the cax1/cax3 double mutant displays an elevated Pi level in shoots as a result of increased Pi uptake in a miR399/PHO2-independent signaling pathway. Microarray analysis of the cax1/cax3 mutant suggests the regulatory function of CAX1 and CAX3 in suppressing the expression of a subset of shoot Pi starvation-responsive genes, including genes encoding the PHT1;4 Pi transporter and two SPX domain-containing proteins, SPX1 and SPX3. Moreover, although the expression of several PHT1 genes and PHT1;1/2/3 proteins is not up-regulated in the root of cax1/cax3, results from reciprocal grafting experiments indicate that the cax1/cax3 scion is responsible for high Pi accumulation in grafted plants and that the pht1;1 rootstock is sufficient to moderately repress such Pi accumulation. Based on these findings, we propose that CAX1 and CAX3 mediate a shoot-derived signal that modulates the activity of the root Pi transporter system, likely in part via posttranslational regulation of PHT1;1 Pi transporters. PMID:21546457

  17. Arabidopsis Roots and Shoots Show Distinct Temporal Adaptation Patterns toward Nitrogen Starvation1[W

    PubMed Central

    Krapp, Anne; Berthomé, Richard; Orsel, Mathilde; Mercey-Boutet, Stéphanie; Yu, Agnes; Castaings, Loren; Elftieh, Samira; Major, Hilary; Renou, Jean-Pierre; Daniel-Vedele, Françoise

    2011-01-01

    Nitrogen (N) is an essential macronutrient for plants. N levels in soil vary widely, and plants have developed strategies to cope with N deficiency. However, the regulation of these adaptive responses and the coordinating signals that underlie them are still poorly understood. The aim of this study was to characterize N starvation in adult Arabidopsis (Arabidopsis thaliana) plants in a spatiotemporal manner by an integrative, multilevel global approach analyzing growth, metabolites, enzyme activities, and transcript levels. We determined that the remobilization of N and carbon compounds to the growing roots occurred long before the internal N stores became depleted. A global metabolite analysis by gas chromatography-mass spectrometry revealed organ-specific differences in the metabolic adaptation to complete N starvation, for example, for several tricarboxylic acid cycle intermediates, but also for carbohydrates, secondary products, and phosphate. The activities of central N metabolism enzymes and the capacity for nitrate uptake adapted to N starvation by favoring N remobilization and by increasing the high-affinity nitrate uptake capacity after long-term starvation. Changes in the transcriptome confirmed earlier studies and added a new dimension by revealing specific spatiotemporal patterns and several unknown N starvation-regulated genes, including new predicted small RNA genes. No global correlation between metabolites, enzyme activities, and transcripts was evident. However, this multilevel spatiotemporal global study revealed numerous new patterns of adaptation mechanisms to N starvation. In the context of a sustainable agriculture, this work will give new insight for the production of crops with increased N use efficiency. PMID:21900481

  18. Nitrogen Source and External Medium pH Interaction Differentially Affects Root and Shoot Metabolism in Arabidopsis

    PubMed Central

    Sarasketa, Asier; González-Moro, M. Begoña; González-Murua, Carmen; Marino, Daniel

    2016-01-01

    Ammonium nutrition often represents an important growth-limiting stress in plants. Some of the symptoms that plants present under ammonium nutrition have been associated with pH deregulation, in fact external medium pH control is known to improve plants ammonium tolerance. However, the way plant cell metabolism adjusts to these changes is not completely understood. Thus, in this work we focused on how Arabidopsis thaliana shoot and root respond to different nutritional regimes by varying the nitrogen source (NO3- and NH4+), concentration (2 and 10 mM) and pH of the external medium (5.7 and 6.7) to gain a deeper understanding of cell metabolic adaptation upon altering these environmental factors. The results obtained evidence changes in the response of ammonium assimilation machinery and of the anaplerotic enzymes associated to Tricarboxylic Acids (TCA) cycle in function of the plant organ, the nitrogen source and the degree of ammonium stress. A greater stress severity at pH 5.7 was related to NH4+ accumulation; this could not be circumvented in spite of the stimulation of glutamine synthetase, glutamate dehydrogenase, and TCA cycle anaplerotic enzymes. Moreover, this study suggests specific functions for different gln and gdh isoforms based on the nutritional regime. Overall, NH4+ accumulation triggering ammonium stress appears to bear no relation to nitrogen assimilation impairment. PMID:26870054

  19. SUPPRESSOR OF APICAL DOMINANCE1 of Sporisorium reilianum changes inflorescence branching at early stages in di- and monocot plants and induces fruit abortion in Arabidopsis thaliana.

    PubMed

    Drechsler, Frank; Schwinges, Patrick; Schirawski, Jan

    2016-05-01

    sporisorium reilianum f. sp. zeae is a biotrophic smut fungus that infects maize (Zea mays). Among others, the fungus-plant interaction is governed by secreted fungal effector proteins. The effector SUPPRESSOR OF APICAL DOMINANCE1 (SAD1) changes the development of female inflorescences and induces outgrowth of subapical ears in S. reilianum-infected maize. When stably expressed in Arabidopsis thaliana as a GFP-SAD1 fusion protein, SAD1 induces earlier inflorescence branching and abortion of siliques. Absence of typical hormone-dependent phenotypes in other parts of the transgenic A. thaliana plants expressing GFP-SAD1 hint to a hormone-independent induction of bud outgrowth by SAD1. Silique abortion and bud outgrowth are also known to be controlled by carbon source concentration and by stress-induced molecules, making these factors interesting potential SAD1 targets. PMID:27058118

  20. Identification of a Stelar-Localized Transport Protein That Facilitates Root-to-Shoot Transfer of Chloride in Arabidopsis1[OPEN

    PubMed Central

    Li, Bo; Baumann, Ute; Hrmova, Maria; Evrard, Aurelie; Johnson, Alexander A.T.; Birnbaum, Kenneth D.; Mayo, Gwenda M.; Jha, Deepa

    2016-01-01

    Under saline conditions, higher plants restrict the accumulation of chloride ions (Cl–) in the shoot by regulating their transfer from the root symplast into the xylem-associated apoplast. To identify molecular mechanisms underpinning this phenomenon, we undertook a transcriptional screen of salt stressed Arabidopsis (Arabidopsis thaliana) roots. Microarrays, quantitative RT-PCR, and promoter-GUS fusions identified a candidate gene involved in Cl– xylem loading from the Nitrate transporter 1/Peptide Transporter family (NPF2.4). This gene was highly expressed in the root stele compared to the cortex, and its expression decreased after exposure to NaCl or abscisic acid. NPF2.4 fused to fluorescent proteins, expressed either transiently or stably, was targeted to the plasma membrane. Electrophysiological analysis of NPF2.4 in Xenopus laevis oocytes suggested that NPF2.4 catalyzed passive Cl– efflux out of cells and was much less permeable to NO3−. Shoot Cl– accumulation was decreased following NPF2.4 artificial microRNA knockdown, whereas it was increased by overexpression of NPF2.4. Taken together, these results suggest that NPF2.4 is involved in long-distance transport of Cl– in plants, playing a role in the loading and the regulation of Cl– loading into the xylem of Arabidopsis roots during salinity stress. PMID:26662602

  1. CLV3 IS LOCALIZED TO THE EXTRACELLULAR SPACE, WHERE IT ACTIVATES THE ARABIDOPSIS CLAVATA STEM CELL SIGNALING PATHWAY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant growth and development depends upon the activity of a continuously replenished pool of stem cells within the shoot apical meristem to supply cells for organogenesis. In Arabidopsis, the stem cell-specific protein CLAVATA3 (CLV3) acts cell nonautonomously to restrict the size of the stem cell p...

  2. Strigolactone Signaling in Arabidopsis Regulates Shoot Development by Targeting D53-Like SMXL Repressor Proteins for Ubiquitination and Degradation[OPEN

    PubMed Central

    Jiang, Liang; Liu, Xue; Li, Xilong; Lu, Zefu; Meng, Xiangbing; Wang, Yonghong

    2015-01-01

    Strigolactones (SLs) are carotenoid-derived phytohormones that control many aspects of plant development, including shoot branching, leaf shape, stem secondary thickening, and lateral root growth. In rice (Oryza sativa), SL signaling requires the degradation of DWARF53 (D53), mediated by a complex including D14 and D3, but in Arabidopsis thaliana, the components and mechanism of SL signaling involving the D3 ortholog MORE AXILLARY GROWTH2 (MAX2) are unknown. Here, we show that SL-dependent regulation of shoot branching in Arabidopsis requires three D53-like proteins, SUPPRESSOR OF MORE AXILLARY GROWTH2-LIKE6 (SMXL6), SMXL7, and SMXL8. The smxl6 smxl7 smxl8 triple mutant suppresses the highly branched phenotypes of max2 and the SL-deficient mutant max3. Overexpression of a mutant form of SMXL6 that is resistant to SL-induced ubiquitination and degradation enhances shoot branching. Exogenous application of the SL analog rac-GR24 causes ubiquitination and degradation of SMXL6, 7, and 8; this requires D14 and MAX2. D53-like SMXLs form complexes with MAX2 and TOPLESS-RELATED PROTEIN2 (TPR2) and interact with D14 in a GR24-responsive manner. Furthermore, D53-like SMXLs exhibit TPR2-dependent transcriptional repression activity and repress the expression of BRANCHED1. Our findings reveal that in Arabidopsis, D53-like SMXLs act with TPR2 to repress transcription and so allow lateral bud outgrowth but that SL-induced degradation of D53-like proteins activates transcription to inhibit outgrowth. PMID:26546446

  3. AXR1 Acts after Lateral Bud Formation to Inhibit Lateral Bud Growth in Arabidopsis1

    PubMed Central

    Stirnberg, Petra; Chatfield, Steven P.; Leyser, H.M. Ottoline

    1999-01-01

    The AXR1 gene of Arabidopsis is required for many auxin responses. The highly branched shoot phenotype of mature axr1 mutant plants has been taken as genetic evidence for a role of auxin in the control of shoot branching. We compared the development of lateral shoots in wild-type Columbia and axr1-12 plants. In the wild type, the pattern of lateral shoot development depends on the developmental stage of the plant. During prolonged vegetative growth, axillary shoots arise and develop in a basal-apical sequence. After floral transition, axillary shoots arise rapidly along the primary shoot axis and grow out to form lateral inflorescences in an apical-basal sequence. For both patterns, the axr1 mutation does not affect the timing of axillary meristem formation; however, subsequent lateral shoot development proceeds more rapidly in axr1 plants. The outgrowth of lateral inflorescences from excised cauline nodes of wild-type plants is inhibited by apical auxin. axr1-12 nodes are resistant to this inhibition. These results provide evidence for common control of axillary growth in both patterns, and suggest a role for auxin during the late stages of axillary shoot development following the formation of the axillary bud and several axillary leaf primordia. PMID:10557232

  4. Kaempferol 3-O-rhamnoside-7-O-rhamnoside is an endogenous flavonol inhibitor of polar auxin transport in Arabidopsis shoots

    PubMed Central

    Yin, Ruohe; Han, Kerstin; Heller, Werner; Albert, Andreas; Dobrev, Petre I; Zažímalová, Eva; Schäffner, Anton R

    2014-01-01

    Polar auxin transport (PAT) plays key roles in the regulation of plant growth and development. Flavonoids have been implicated in the inhibition of PAT. However, the active flavonoid derivative(s) involved in this process in vivo has not yet been identified. Here, we provide evidence that a specific flavonol bis-glycoside is correlated with shorter plant stature and reduced PAT. Specific flavonoid-biosynthetic or flavonoid-glycosylating steps were genetically blocked in Arabidopsis thaliana. The differential flavonol patterns established were analyzed by high-performance liquid chromatography (HPLC) and related to altered plant stature. PAT was monitored in stem segments using a radioactive [3H]-indole-3-acetic acid tracer. The flavonoid 3-O-glucosyltransferase mutant ugt78d2 exhibited a dwarf stature in addition to its altered flavonol glycoside pattern. This was accompanied by reduced PAT in ugt78d2 shoots. The ugt78d2-dependent growth defects were flavonoid dependent, as they were rescued by genetic blocking of flavonoid biosynthesis. Phenotypic and metabolic analyses of a series of mutants defective at various steps of flavonoid formation narrowed down the potentially active moiety to kaempferol 3-O-rhamnoside-7-O-rhamnoside. Moreover, the level of this compound was negatively correlated with basipetal auxin transport. These results indicate that kaempferol 3-O-rhamnoside-7-O-rhamnoside acts as an endogenous PAT inhibitor in Arabidopsis shoots. PMID:24251900

  5. SMAX1-LIKE7 Signals from the Nucleus to Regulate Shoot Development in Arabidopsis via Partially EAR Motif-Independent Mechanisms[OPEN

    PubMed Central

    Li, Ping

    2016-01-01

    Strigolactones (SLs) are hormonal signals that regulate multiple aspects of shoot architecture, including shoot branching. Like many plant hormonal signaling systems, SLs act by promoting ubiquitination of target proteins and their subsequent proteasome-mediated degradation. Recently, SMXL6, SMXL7, and SMXL8, members of the SMAX1-LIKE (SMXL) family of chaperonin-like proteins, have been identified as proteolytic targets of SL signaling in Arabidopsis thaliana. However, the mechanisms by which these proteins regulate downstream events remain largely unclear. Here, we show that SMXL7 functions in the nucleus, as does the SL receptor, DWARF14 (D14). We show that nucleus-localized D14 can physically interact with both SMXL7 and the MAX2 F-box protein in a SL-dependent manner and that disruption of specific conserved domains in SMXL7 affects its localization, SL-induced degradation, and activity. By expressing and overexpressing these SMXL7 protein variants, we show that shoot tissues are broadly sensitive to SMXL7 activity, but degradation normally buffers the effect of increasing SMXL7 expression. SMXL7 contains a well-conserved EAR (ETHYLENE-RESPONSE FACTOR Amphiphilic Repression) motif, which contributes to, but is not essential for, SMXL7 functionality. Intriguingly, different developmental processes show differential sensitivity to the loss of the EAR motif, raising the possibility that there may be several distinct mechanisms at play downstream of SMXL7. PMID:27317673

  6. Modulation of Zn/Cd P(1B2)-ATPase activities in Arabidopsis impacts differently on Zn and Cd contents in shoots and seeds.

    PubMed

    Cun, Pierre; Sarrobert, Catherine; Richaud, Pierre; Chevalier, Anne; Soreau, Paul; Auroy, Pascaline; Gravot, Antoine; Baltz, Anthony; Leonhardt, Nathalie; Vavasseur, Alain

    2014-11-01

    Zn is an essential microelement for all living cells and Zn deficiency is widespread in world's population. At the same time, high Zn concentration and low Cd concentration are toxic to the environment. Both Zn and Cd are transported in planta via Zn/Cd HMA transporters. Engineering of HMAs expression in plants may provide a way for Zn biofortification of food as well as phytoremediation of polluted soils. In the present study we have assessed the impact of Zn/Cd HMAs invalidation/overexpression in Arabidopsis thaliana on Zn and Cd translocation from the roots to the shoots and in Zn grain filling. Overexpression of AtHMA4 had a large impact on Zn and Cd translocation and resulted in a 3-fold higher potential of Cd and Zn extraction from an industrial soil highly contaminated by Zn, Pb and Cd. Despite AtHMA4 overexpressing lines presenting a higher Zn concentration in the shoot, the Zn content in the seeds was found to be lower than in wild type plants. Our results indicate that AtHMA4 overexpression is an efficient tool to increase the root to shoot translocation of Zn and Cd in plants. Concerning biofortification of seeds, this study underlines the need for specific promoters to drive an expression pattern of the transporters in favour of Zn grain filling. PMID:25272315

  7. Conservation and Diversification of the SHR-SCR-SCL23 Regulatory Network in the Development of the Functional Endodermis in Arabidopsis Shoots.

    PubMed

    Yoon, Eun Kyung; Dhar, Souvik; Lee, Mi-Hyun; Song, Jae Hyo; Lee, Shin Ae; Kim, Gyuree; Jang, Sejeong; Choi, Ji Won; Choe, Jeong-Eun; Kim, Jeong Hoe; Lee, Myeong Min; Lim, Jun

    2016-08-01

    Development of the functional endodermis of Arabidopsis thaliana roots is controlled, in part, by GRAS transcription factors, namely SHORT-ROOT (SHR), SCARECROW (SCR), and SCARECROW-LIKE 23 (SCL23). Recently, it has been shown that the SHR-SCR-SCL23 regulatory module is also essential for specification of the endodermis (known as the bundle sheath) in leaves. Nevertheless, compared with what is known about the role of the SHR-SCR-SCL23 regulatory network in roots, the molecular interactions of SHR, SCR, and SCL23 are much less understood in shoots. Here, we show that SHR forms protein complexes with SCL23 to regulate transcription of SCL23 in shoots, similar to the regulation mode of SCR expression. Our results indicate that SHR acts as master regulator to directly activate the expression of SCR and SCL23. In the SHR-SCR-SCL23 network, we found a previously uncharacterized negative feedback loop whereby SCL23 modulates SHR levels. Through molecular, genetic, physiological, and morphological analyses, we also reveal that the SHR-SCR-SCL23 module plays a key role in the formation of the endodermis (known as the starch sheath) in hypocotyls. Taken together, our results provide new insights into the regulatory role of the SHR-SCR-SCL23 network in the endodermis development in both roots and shoots. PMID:27353361

  8. Plastid-Localized Glutathione Reductase2–Regulated Glutathione Redox Status Is Essential for Arabidopsis Root Apical Meristem Maintenance[C][W

    PubMed Central

    Yu, Xin; Pasternak, Taras; Eiblmeier, Monika; Ditengou, Franck; Kochersperger, Philip; Sun, Jiaqiang; Wang, Hui; Rennenberg, Heinz; Teale, William; Paponov, Ivan; Zhou, Wenkun; Li, Chuanyou; Li, Xugang; Palme, Klaus

    2013-01-01

    Glutathione is involved in thiol redox signaling and acts as a major redox buffer against reactive oxygen species, helping to maintain a reducing environment in vivo. Glutathione reductase (GR) catalyzes the reduction of glutathione disulfide (GSSG) into reduced glutathione (GSH). The Arabidopsis thaliana genome encodes two GRs: GR1 and GR2. Whereas the cytosolic/peroxisomal GR1 is not crucial for plant development, we show here that the plastid-localized GR2 is essential for root growth and root apical meristem (RAM) maintenance. We identify a GR2 mutant, miao, that displays strong inhibition of root growth and severe defects in the RAM, with GR activity being reduced to ∼50%. miao accumulates high levels of GSSG and exhibits increased glutathione oxidation. The exogenous application of GSH or the thiol-reducing agent DTT can rescue the root phenotype of miao, demonstrating that the RAM defects in miao are triggered by glutathione oxidation. Our in silico analysis of public microarray data shows that auxin and glutathione redox signaling generally act independently at the transcriptional level. We propose that glutathione redox status is essential for RAM maintenance through both auxin/PLETHORA (PLT)-dependent and auxin/PLT-independent redox signaling pathways. PMID:24249834

  9. The concept of the eudicot shoot apical meristem as it applies to four Spiraea (Rosaceae), one Mentha (Lamiaceae) and one Euonymus (Celastraceae) cultivars based on chimeric analysis

    PubMed Central

    Korn, Robert W.

    2013-01-01

    Background and Aims Eversporting eudicots were sought to see if they behave like gymnosperms. Behaviour of eversporting gymnosperm chimeras indicates a single apical cell is present in SAM and it would be of interest to see if eudicot chimeras have the same behaviour. Methods Four eversporting spireas, the pineapple mint and the Silver King euonymus were inspected for the fate of the yellow (mutant)–green (wild type) chimeras. Key Results As with gymnosperms, unstable eudicot chimeras in the four spireas, the pineapple mint and the Silver King euonymus became stable yellow about 80 % or more of the time and 20 % or less became stable green. Conclusions The statistically significant preponderance of chimeric fates becoming all yellow suggests that a single apical cell resides in the yellow tunica. As with gymnosperms, descendent cells of the yellow replacement corpus cell eventually take over the corpus. Here is the first chimeric set of data to support the hypothesis of a one-celled meristem in eudicots rather than the traditional view of a muticellular meristem. PMID:23482330

  10. Roles of DgD14 in regulation of shoot branching in chrysanthemum (Dendranthema grandiflorum 'Jinba').

    PubMed

    Wen, Chao; Xi, Lin; Gao, Bin; Wang, Keyong; Lv, Suhui; Kou, Yaping; Ma, Nan; Zhao, Liangjun

    2015-11-01

    Shoot branching plays an important role in determining plant architecture. Strigolactones (SLs) negatively regulate shoot branching, and can respond to conditions of low or absent phosphate or nitrogen. The D14 gene is a probable candidate as an SL receptor in rice, petunia, and Arabidopsis. To investigate the roles of D14 in shoot branching of chrysanthemum, we isolated the D14 homolog DgD14. Functional analysis showed that DgD14 was a nuclear-localized protein, and restored the phenotype of Arabidopsis d14-1. Exogenous SL (GR24) could down-regulate DgD14 expression, but this effect could be overridden by apical auxin application. Decapitation could down-regulate DgD14 expression, but this effect could be restored by exogenous auxin. In addition, DgD14 transcripts produced rapid responses in shoot and root under conditions of phosphate absence, but only a mild variation in bud and stem with low nitrogen treatment. Indistinct reductions of P levels in shoot were observed in plants grown under low nitrogen conditions. The absence of phosphate and low levels of nitrogen negatively affected plant growth. These results demonstrate that P levels in shoot had a close relationship with phosphate, whereas nitrogen did not directly regulate DgD14 expression in shoot. Taken together, these results demonstrated that DgD14 was the functional strigolactone signaling component in chrysanthemum. PMID:26310142

  11. Arabidopsis YL1/BPG2 Is Involved in Seedling Shoot Response to Salt Stress through ABI4.

    PubMed

    Li, Peng-Cheng; Huang, Jin-Guang; Yu, Shao-Wei; Li, Yuan-Yuan; Sun, Peng; Wu, Chang-Ai; Zheng, Cheng-Chao

    2016-01-01

    The chloroplast-localized proteins play roles in plant salt stress response, but their mechanisms remain largely unknown. In this study, we screened a yellow leaf mutant, yl1-1, whose shoots exhibited hypersensitivity to salt stress. We mapped YL1 to AT3G57180, which encodes a YqeH-type GTPase. YL1, as a chloroplast stroma-localized protein, could be markedly reduced by high salinity. Upon exposure to high salinity, seedling shoots of yl1-1 and yl1-2 accumulated significantly higher levels of Na(+) than wild type. Expression analysis of factors involved in plant salt stress response showed that the expression of ABI4 was increased and HKT1 was evidently suppressed in mutant shoots compared with the wild type under normal growth conditions. Moreover, salinity effects on ABI4 and HKT1 were clearly weakened in the mutant shoots, suggesting that the loss of YL1 function impairs ABI4 and HKT1 expression. Notably, the shoots of yl1-2 abi4 double mutant exhibited stronger resistance to salt stress and accumulated less Na(+) levels after salt treatment compared with the yl1-2 single mutant, suggesting the salt-sensitive phenotype of yl1-2 seedlings could be rescued via loss of ABI4 function. These results reveal that YL1 is involved in the salt stress response of seedling shoots through ABI4. PMID:27444988

  12. Arabidopsis YL1/BPG2 Is Involved in Seedling Shoot Response to Salt Stress through ABI4

    PubMed Central

    Li, Peng-Cheng; Huang, Jin-Guang; Yu, Shao-Wei; Li, Yuan-Yuan; Sun, Peng; Wu, Chang-Ai; Zheng, Cheng-Chao

    2016-01-01

    The chloroplast-localized proteins play roles in plant salt stress response, but their mechanisms remain largely unknown. In this study, we screened a yellow leaf mutant, yl1-1, whose shoots exhibited hypersensitivity to salt stress. We mapped YL1 to AT3G57180, which encodes a YqeH-type GTPase. YL1, as a chloroplast stroma-localized protein, could be markedly reduced by high salinity. Upon exposure to high salinity, seedling shoots of yl1-1 and yl1-2 accumulated significantly higher levels of Na+ than wild type. Expression analysis of factors involved in plant salt stress response showed that the expression of ABI4 was increased and HKT1 was evidently suppressed in mutant shoots compared with the wild type under normal growth conditions. Moreover, salinity effects on ABI4 and HKT1 were clearly weakened in the mutant shoots, suggesting that the loss of YL1 function impairs ABI4 and HKT1 expression. Notably, the shoots of yl1-2 abi4 double mutant exhibited stronger resistance to salt stress and accumulated less Na+ levels after salt treatment compared with the yl1-2 single mutant, suggesting the salt-sensitive phenotype of yl1-2 seedlings could be rescued via loss of ABI4 function. These results reveal that YL1 is involved in the salt stress response of seedling shoots through ABI4. PMID:27444988

  13. Measurement of Differential Na+ Efflux from Apical and Bulk Root Zones of Intact Barley and Arabidopsis Plants

    PubMed Central

    Hamam, Ahmed M.; Britto, Dev T.; Flam-Shepherd, Rubens; Kronzucker, Herbert J.

    2016-01-01

    Rapid sodium cycling across the plasma membrane of root cells is widely thought to be associated with Na+ toxicity in plants. However, the efflux component of this cycling is not well understood. Efflux of Na+ from root cells is believed to be mediated by Salt Overly-Sensitive-1, although expression of this Na+/H+ antiporter has been localized to the vascular tissue and root meristem. Here, we used a chambered cuvette system in which the distal root of intact salinized barley and Arabidopsis thaliana plants (wild-type and sos1) were isolated from the bulk of the root by a silicone-acrylic barrier, so that we could compare patterns of 24Na+ efflux in these two regions of root. In barley, steady-state release of 24Na+ was about four times higher from the distal root than from the bulk roots. In the distal root, 24Na+ release was pronouncedly decreased by elevated pH (9.2), while the bulk-root release was not significantly affected. In A. thaliana, tracer efflux was about three times higher from the wild-type distal root than from the wild-type bulk root and also three to four times higher than both distal- and bulk-root fluxes of Atsos1 mutants. Elevated pH also greatly reduced the efflux from wild-type roots. These findings support a significant role of SOS1-mediated Na+ efflux in the distal root, but not in the bulk root. PMID:27014297

  14. Cytokinin is required for escape but not release from auxin mediated apical dominance

    PubMed Central

    Müller, Dörte; Waldie, Tanya; Miyawaki, Kaori; To, Jennifer PC; Melnyk, Charles W; Kieber, Joseph J; Kakimoto, Tatsuo; Leyser, Ottoline

    2015-01-01

    Auxin produced by an active primary shoot apex is transported down the main stem and inhibits the growth of the axillary buds below it, contributing to apical dominance. Here we use Arabidopsis thaliana cytokinin (CK) biosynthetic and signalling mutants to probe the role of CK in this process. It is well established that bud outgrowth is promoted by CK, and that CK synthesis is inhibited by auxin, leading to the hypothesis that release from apical dominance relies on an increased supply of CK to buds. Our data confirm that decapitation induces the expression of at least one ISOPENTENYLTRANSFERASE (IPT) CK biosynthetic gene in the stem. We further show that transcript abundance of a clade of the CK-responsive type-A Arabidopsis response regulator (ARR) genes increases in buds following CK supply, and that, contrary to their typical action as inhibitors of CK signalling, these genes are required for CK-mediated bud activation. However, analysis of the relevant arr and ipt multiple mutants demonstrates that defects in bud CK response do not affect auxin-mediated bud inhibition, and increased IPT transcript levels are not needed for bud release following decapitation. Instead, our data suggest that CK acts to overcome auxin-mediated bud inhibition, allowing buds to escape apical dominance under favourable conditions, such as high nitrate availability. Significance Statement It has been proposed that the release of buds from auxin-mediated apical dominance following decapitation requires increased cytokinin biosynthesis and consequent increases in cytokinin supply to buds. Here we show that in Arabidopsis, increases in cytokinin appear to be unnecessary for the release of buds from apical dominance, but rather allow buds to escape the inhibitory effect of apical auxin, thereby promoting bud activation in favourable growth conditions. PMID:25904120

  15. A Shoot-Specific Hypoxic Response of Arabidopsis Sheds Light on the Role of the Phosphate-Responsive Transcription Factor PHOSPHATE STARVATION RESPONSE11[W

    PubMed Central

    Klecker, Maria; Gasch, Philipp; Peisker, Helga; Dörmann, Peter; Schlicke, Hagen; Grimm, Bernhard; Mustroph, Angelika

    2014-01-01

    Plant responses to biotic and abiotic stresses are often very specific, but signal transduction pathways can partially or completely overlap. Here, we demonstrate that in Arabidopsis (Arabidopsis thaliana), the transcriptional responses to phosphate starvation and oxygen deficiency stress comprise a set of commonly induced genes. While the phosphate deficiency response is systemic, under oxygen deficiency, most of the commonly induced genes are found only in illuminated shoots. This jointly induced response to the two stresses is under control of the transcription factor PHOSPHATE STARVATION RESPONSE1 (PHR1), but not of the oxygen-sensing N-end rule pathway, and includes genes encoding proteins for the synthesis of galactolipids, which replace phospholipids in plant membranes under phosphate starvation. Despite the induction of galactolipid synthesis genes, total galactolipid content and plant survival are not severely affected by the up-regulation of galactolipid gene expression in illuminated leaves during hypoxia. However, changes in galactolipid molecular species composition point to an adaptation of lipid fluxes through the endoplasmic reticulum and chloroplast pathways during hypoxia. PHR1-mediated signaling of phosphate deprivation was also light dependent. Because a photoreceptor-mediated PHR1 activation was not detectable under hypoxia, our data suggest that a chloroplast-derived retrograde signal, potentially arising from metabolic changes, regulates PHR1 activity under both oxygen and phosphate deficiency. PMID:24753539

  16. Mitogen-Activated Protein Kinase Cascade MKK7-MPK6 Plays Important Roles in Plant Development and Regulates Shoot Branching by Phosphorylating PIN1 in Arabidopsis.

    PubMed

    Jia, Weiyan; Li, Baohua; Li, Shujia; Liang, Yan; Wu, Xiaowei; Ma, Mei; Wang, Jiyao; Gao, Jin; Cai, Yueyue; Zhang, Yuanya; Wang, Yingchun; Li, Jiayang; Wang, Yonghong

    2016-09-01

    Emerging evidences exhibit that mitogen-activated protein kinase (MAPK/MPK) signaling pathways are connected with many aspects of plant development. The complexity of MAPK cascades raises challenges not only to identify the MAPK module in planta but also to define the specific role of an individual module. So far, our knowledge of MAPK signaling has been largely restricted to a small subset of MAPK cascades. Our previous study has characterized an Arabidopsis bushy and dwarf1 (bud1) mutant, in which the MAP Kinase Kinase 7 (MKK7) was constitutively activated, resulting in multiple phenotypic alterations. In this study, we found that MPK3 and MPK6 are the substrates for phosphorylation by MKK7 in planta. Genetic analysis showed that MKK7-MPK6 cascade is specifically responsible for the regulation of shoot branching, hypocotyl gravitropism, filament elongation, and lateral root formation, while MKK7-MPK3 cascade is mainly involved in leaf morphology. We further demonstrated that the MKK7-MPK6 cascade controls shoot branching by phosphorylating Ser 337 on PIN1, which affects the basal localization of PIN1 in xylem parenchyma cells and polar auxin transport in the primary stem. Our results not only specify the functions of the MKK7-MPK6 cascade but also reveal a novel mechanism for PIN1 phosphorylation, establishing a molecular link between the MAPK cascade and auxin-regulated plant development. PMID:27618482

  17. Water Deficit Enhances C Export to the Roots in Arabidopsis thaliana Plants with Contribution of Sucrose Transporters in Both Shoot and Roots1[OPEN

    PubMed Central

    Durand, Mickaël; Porcheron, Benoît; Maurousset, Laurence; Lemoine, Rémi; Pourtau, Nathalie

    2016-01-01

    Root high plasticity is an adaptation to its changing environment. Water deficit impairs growth, leading to sugar accumulation in leaves, part of which could be available to roots via sucrose (Suc) phloem transport. Phloem loading is widely described in Arabidopsis (Arabidopsis thaliana), while unloading in roots is less understood. To gain information on leaf-to-root transport, a soil-based culture system was developed to monitor root system architecture in two dimensions. Under water deficit (50% of soil water-holding capacity), total root length was strongly reduced but the depth of root foraging and the shape of the root system were less affected, likely to improve water uptake. 14CO2 pulse-chase experiments confirmed that water deficit enhanced carbon (C) export to the roots, as suggested by the increased root-to-shoot ratio. The transcript levels of AtSWEET11 (for sugar will eventually be exported transporter), AtSWEET12, and AtSUC2 (for Suc carrier) genes, all three involved in Suc phloem loading, were significantly up-regulated in leaves of water deficit plants, in accordance with the increase in C export from the leaves to the roots. Interestingly, the transcript levels of AtSUC2 and AtSWEET11 to AtSWEET15 were also significantly higher in stressed roots, underlying the importance of Suc apoplastic unloading in Arabidopsis roots and a putative role for these Suc transporters in Suc unloading. These data demonstrate that, during water deficit, plants respond to growth limitation by allocating relatively more C to the roots to maintain an efficient root system and that a subset of Suc transporters is potentially involved in the flux of C to and in the roots. PMID:26802041

  18. Water Deficit Enhances C Export to the Roots in Arabidopsis thaliana Plants with Contribution of Sucrose Transporters in Both Shoot and Roots.

    PubMed

    Durand, Mickaël; Porcheron, Benoît; Hennion, Nils; Maurousset, Laurence; Lemoine, Rémi; Pourtau, Nathalie

    2016-03-01

    Root high plasticity is an adaptation to its changing environment. Water deficit impairs growth, leading to sugar accumulation in leaves, part of which could be available to roots via sucrose (Suc) phloem transport. Phloem loading is widely described in Arabidopsis (Arabidopsis thaliana), while unloading in roots is less understood. To gain information on leaf-to-root transport, a soil-based culture system was developed to monitor root system architecture in two dimensions. Under water deficit (50% of soil water-holding capacity), total root length was strongly reduced but the depth of root foraging and the shape of the root system were less affected, likely to improve water uptake. (14)CO2 pulse-chase experiments confirmed that water deficit enhanced carbon (C) export to the roots, as suggested by the increased root-to-shoot ratio. The transcript levels of AtSWEET11 (for sugar will eventually be exported transporter), AtSWEET12, and AtSUC2 (for Suc carrier) genes, all three involved in Suc phloem loading, were significantly up-regulated in leaves of water deficit plants, in accordance with the increase in C export from the leaves to the roots. Interestingly, the transcript levels of AtSUC2 and AtSWEET11 to AtSWEET15 were also significantly higher in stressed roots, underlying the importance of Suc apoplastic unloading in Arabidopsis roots and a putative role for these Suc transporters in Suc unloading. These data demonstrate that, during water deficit, plants respond to growth limitation by allocating relatively more C to the roots to maintain an efficient root system and that a subset of Suc transporters is potentially involved in the flux of C to and in the roots. PMID:26802041

  19. Structure–Function Relationships in Highly Modified Shoots of Cactaceae

    PubMed Central

    MAUSETH, JAMES D.

    2006-01-01

    • Background and Aims Cacti are extremely diverse structurally and ecologically, and so modified as to be intimidating to many biologists. Yet all have the same organization as most dicots, none differs fundamentally from Arabidopsis or other model plants. This review explains cactus shoot structure, discusses relationships between structure, ecology, development and evolution, and indicates areas where research on cacti is necessary to test general theories of morphogenesis. • Scope Cactus leaves are diverse; all cacti have foliage leaves; many intermediate stages in evolutionary reduction of leaves are still present; floral shoots often have large, complex leaves whereas vegetative shoots have microscopic leaves. Spines are modified bud scales, some secrete sugar as extra-floral nectaries. Many cacti have juvenile/adult phases in which the flowering adult phase (a cephalium) differs greatly from the juvenile; in some, one side of a shoot becomes adult, all other sides continue to grow as the juvenile phase. Flowers are inverted: the exterior of a cactus ‘flower’ is a hollow vegetative shoot with internodes, nodes, leaves and spines, whereas floral organs occur inside, with petals physically above stamens. Many cacti have cortical bundles vascularizing the cortex, however broad it evolves to be, thus keeping surface tissues alive. Great width results in great weight of weak parenchymatous shoots, correlated with reduced branching. Reduced numbers of shoot apices is compensated by great increases in number of meristematic cells within individual SAMs. Ribs and tubercles allow shoots to swell without tearing during wet seasons. Shoot epidermis and cortex cells live and function for decades then convert to cork cambium. Many modifications permit water storage within cactus wood itself, adjacent to vessels. PMID:16820405

  20. Evaluation of Growth Regulators on In Vitro Hibiscus Shoot Regeneration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Multiple shoot induction and plant regeneration was achieved from shoot apices in two genotypes (red and green variants) of Hibiscus acetosella Welw. ex. Hiern using the growth regulators thidiazuron (N-phenyl-N’-1,2,3-thidazol-5-ylurea, TDZ) and 6-benzyladenine (BA). Shoot apices were cultured for ...

  1. Bystander/abscopal effects induced in intact Arabidopsis seeds by low-energy heavy-ion radiation.

    PubMed

    Yang, Gen; Mei, Tao; Yuan, Hang; Zhang, Weiming; Chen, Lianyun; Xue, Jianming; Wu, Lijun; Wang, Yugang

    2008-09-01

    To date, radiation-induced bystander effects have been observed largely in in vitro single-cell systems; verification of both the effects and the mechanisms in multicellular systems in vivo is important. Previously we showed that bystander/ abscopal effects can be induced by irradiating the shoot apical meristem cells in Arabidopsis embryos. In this study, we investigated the in vivo effects induced by 30 keV 40Ar ions in intact Arabidopsis seeds and traced the postembryonic development of both irradiated and nonirradiated shoot apical meristem and root apical meristem cells. Since the range of 30 keV 40Ar ions in water is about 0.07 microm, which is less than the distance from the testa to shoot apical meristem and root apical meristem in Arabidopsis seeds (about 100 microm), the incident low-energy heavy ions generally stop in the proximal surface. Our results showed that, after the 30 keV 40Ar-ion irradiation of shielded and nonshielded Arabidopsis seeds at a fluence of 1.5 x 10(17) ions/cm2, short- and long-term postembryonic development, including germination, root hair differentiation, primary root elongation, lateral root initiation and survival, was significantly inhibited. Since shoot apical meristem and root apical meristem cells were not damaged directly by radiation, the results suggested that a damage signal(s) is transferred from the irradiated cells to shoot apical meristem and root apical meristem cells and causes the ultimate developmental alterations, indicating that long-distance bystander/ abscopal effects exist in the intact seed. A further study of mechanisms showed that the effects are associated with either enhanced generation of reactive oxygen species (ROS) or decreased auxin-dependent transcription in postembryonic development. Treatment with the ROS scavenger dimethyl sulfoxide (DMSO) or synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) can significantly reverse both the alterations in postembryonic development and auxin

  2. In Vitro multiple shoot induction and plant regeneraton from shoot apex of Hibiscus actosella Welw. ex. Hiern

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Multiple shoot induction and plant regeneration was achieved from shoot apices in two Hibiscus acetosella Welw. ex. Hiern variants by using the growth regulators thidiazuron (N-phenyl-N’-1,2,3-thidazol-5-ylurea, TDZ) and 6-benzyladenine (BA) and growing shoot apices for 30 days in 21 different media...

  3. Nitrate-Dependent Control of Shoot K Homeostasis by the Nitrate Transporter1/Peptide Transporter Family Member NPF7.3/NRT1.5 and the Stelar K+ Outward Rectifier SKOR in Arabidopsis1[OPEN

    PubMed Central

    Drechsler, Navina; Zheng, Yue; Nobmann, Barbara; Rausch, Christine

    2015-01-01

    Root-to-shoot translocation and shoot homeostasis of potassium (K) determine nutrient balance, growth, and stress tolerance of vascular plants. To maintain the cation-anion balance, xylem loading of K+ in the roots relies on the concomitant loading of counteranions, like nitrate (NO3−). However, the coregulation of these loading steps is unclear. Here, we show that the bidirectional, low-affinity Nitrate Transporter1 (NRT1)/Peptide Transporter (PTR) family member NPF7.3/NRT1.5 is important for the NO3−-dependent K+ translocation in Arabidopsis (Arabidopsis thaliana). Lack of NPF7.3/NRT1.5 resulted in K deficiency in shoots under low NO3− nutrition, whereas the root elemental composition was unchanged. Gene expression data corroborated K deficiency in the nrt1.5-5 shoot, whereas the root responded with a differential expression of genes involved in cation-anion balance. A grafting experiment confirmed that the presence of NPF7.3/NRT1.5 in the root is a prerequisite for proper root-to-shoot translocation of K+ under low NO3− supply. Because the depolarization-activated Stelar K+ Outward Rectifier (SKOR) has previously been described as a major contributor for root-to-shoot translocation of K+ in Arabidopsis, we addressed the hypothesis that NPF7.3/NRT1.5-mediated NO3− translocation might affect xylem loading and root-to-shoot K+ translocation through SKOR. Indeed, growth of nrt1.5-5 and skor-2 single and double mutants under different K/NO3− regimes revealed that both proteins contribute to K+ translocation from root to shoot. SKOR activity dominates under high NO3− and low K+ supply, whereas NPF7.3/NRT1.5 is required under low NO3− availability. This study unravels nutritional conditions as a critical factor for the joint activity of SKOR and NPF7.3/NRT1.5 for shoot K homeostasis. PMID:26508776

  4. Burkholderia phytofirmans Inoculation-Induced Changes on the Shoot Cell Anatomy and Iron Accumulation Reveal Novel Components of Arabidopsis-Endophyte Interaction that Can Benefit Downstream Biomass Deconstruction

    PubMed Central

    Zhao, Shuai; Wei, Hui; Lin, Chien-Yuan; Zeng, Yining; Tucker, Melvin P.; Himmel, Michael E.; Ding, Shi-You

    2016-01-01

    It is known that plant growth promoting bacteria (PGPB) elicit positive effects on plant growth and biomass yield. However, the actual mechanism behind the plant-PGPB interaction is poorly understood, and the literature is scarce regarding the thermochemical pretreatability and enzymatic degradability of biomass derived from PGPB-inoculated plants. Most recent transcriptional analyses of PGPB strain Burkholderia phytofirmans PsJN inoculating potato in literature and Arabidopsis in our present study have revealed the expression of genes for ferritin and the biosynthesis and transport of siderophores (i.e., the molecules with high affinity for iron), respectively. The expression of such genes in the shoots of PsJN-inoculated plants prompted us to propose that PsJN-inoculation can improve the host plant's iron uptake and accumulation, which facilitates the downstream plant biomass pretreatment and conversion to simple sugars. In this study, we employed B. phytofirmans PsJN to inoculate the Arabidopsis thaliana plants, and conducted the first investigation for its effects on the biomass yield, the anatomical organization of stems, the iron accumulation, and the pretreatment and enzymatic hydrolysis of harvested biomass. The results showed that the strain PsJN stimulated plant growth in the earlier period of plant development and enlarged the cell size of stem piths, and it also indeed enhanced the essential metals uptake and accumulation in host plants. Moreover, we found that the PsJN-inoculated plant biomass released more glucose and xylose after hot water pretreatment and subsequent co-saccharification, which provided a novel insight into development of lignocellulosic biofuels from renewable biomass resources. PMID:26858740

  5. Burkholderia phytofirmans inoculation-induced changes on the shoot cell anatomy and iron accumulation reveal novel components of Arabidopsis-endophyte interaction that can benefit downstream biomass deconstruction

    DOE PAGESBeta

    Zhao, Shuai; Wei, Hui; Lin, Chien -Yuan; Zeng, Yining; Tucker, Melvin P.; Himmel, Michael E.; Ding, Shi -You

    2016-01-29

    In this study, it is known that plant growth promoting bacteria (PGPB) elicit positive effects on plant growth and biomass yield. However, the actual mechanism behind the plant-PGPB interaction is poorly understood, and the literature is scarce regarding the thermochemical pretreatability and enzymatic degradability of biomass derived from PGPB-inoculated plants. Most recent transcriptional analyses of PGPB strain Burkholderia phytofirmans PsJN inoculating potato in literature and Arabidopsis in our present study have revealed the expression of genes for ferritin and the biosynthesis and transport of siderophores (i.e., the molecules with high affinity for iron), respectively. The expression of such genes inmore » the shoots of PsJN-inoculated plants prompted us to propose that PsJN-inoculation can improve the host plant's iron uptake and accumulation, which facilitates the downstream plant biomass pretreatment and conversion to simple sugars. In this study, we employed B. phytofirmans PsJN to inoculate the Arabidopsis thaliana plants, and conducted the first investigation for its effects on the biomass yield, the anatomical organization of stems, the iron accumulation, and the pretreatment and enzymatic hydrolysis of harvested biomass. The results showed that the strain PsJN stimulated plant growth in the earlier period of plant development and enlarged the cell size of stem piths, and it also indeed enhanced the essential metals uptake and accumulation in host plants. Moreover, we found that the PsJN-inoculated plant biomass released more glucose and xylose after hot water pretreatment and subsequent co-saccharification, which provided a novel insight into development of lignocellulosic biofuels from renewable biomass resources.« less

  6. Burkholderia phytofirmans Inoculation-Induced Changes on the Shoot Cell Anatomy and Iron Accumulation Reveal Novel Components of Arabidopsis-Endophyte Interaction that Can Benefit Downstream Biomass Deconstruction.

    PubMed

    Zhao, Shuai; Wei, Hui; Lin, Chien-Yuan; Zeng, Yining; Tucker, Melvin P; Himmel, Michael E; Ding, Shi-You

    2016-01-01

    It is known that plant growth promoting bacteria (PGPB) elicit positive effects on plant growth and biomass yield. However, the actual mechanism behind the plant-PGPB interaction is poorly understood, and the literature is scarce regarding the thermochemical pretreatability and enzymatic degradability of biomass derived from PGPB-inoculated plants. Most recent transcriptional analyses of PGPB strain Burkholderia phytofirmans PsJN inoculating potato in literature and Arabidopsis in our present study have revealed the expression of genes for ferritin and the biosynthesis and transport of siderophores (i.e., the molecules with high affinity for iron), respectively. The expression of such genes in the shoots of PsJN-inoculated plants prompted us to propose that PsJN-inoculation can improve the host plant's iron uptake and accumulation, which facilitates the downstream plant biomass pretreatment and conversion to simple sugars. In this study, we employed B. phytofirmans PsJN to inoculate the Arabidopsis thaliana plants, and conducted the first investigation for its effects on the biomass yield, the anatomical organization of stems, the iron accumulation, and the pretreatment and enzymatic hydrolysis of harvested biomass. The results showed that the strain PsJN stimulated plant growth in the earlier period of plant development and enlarged the cell size of stem piths, and it also indeed enhanced the essential metals uptake and accumulation in host plants. Moreover, we found that the PsJN-inoculated plant biomass released more glucose and xylose after hot water pretreatment and subsequent co-saccharification, which provided a novel insight into development of lignocellulosic biofuels from renewable biomass resources. PMID:26858740

  7. AtMYB2 Regulates Whole Plant Senescence by Inhibiting Cytokinin-Mediated Branching at Late Stages of Development in Arabidopsis1[C][W][OA

    PubMed Central

    Guo, Yongfeng; Gan, Susheng

    2011-01-01

    Whole plant senescence of monocarpic plants consists of three major processes: arrest of shoot apical meristem, organ senescence, and permanent suppression of axillary buds. At early stages of development, axillary buds are inhibited by shoot apex-produced auxin, a mechanism known as apical dominance. How the buds are suppressed as an essential part of whole plant senescence, especially when the shoot apexes are senescent, is not clear. Here, we report an AtMYB2-regulated post apical dominance mechanism by which Arabidopsis (Arabidopsis thaliana) inhibits the outgrowth of axillary buds as part of the whole plant senescence program. AtMYB2 is expressed in the compressed basal internode region of Arabidopsis at late stages of development to suppress the production of cytokinins, the group of hormones that are required for axillary bud outgrowth. atmyb2 T-DNA insertion lines have enhanced expression of cytokinin-synthesizing isopentenyltransferases genes, contain higher levels of cytokinins, and display a bushy phenotype at late stages of development. As a result of the continuous generation of new shoots, atmyb2 plants have a prolonged life span. The AtMYB2 promoter-directed cytokinin oxidase 1 gene in the T-DNA insertion lines reduces the endogenous cytokinin levels and restores the bushy phenotype to the wild type. PMID:21543729

  8. β-Amylase–Like Proteins Function as Transcription Factors in Arabidopsis, Controlling Shoot Growth and Development[C][W][OA

    PubMed Central

    Reinhold, Heike; Soyk, Sebastian; Šimková, Klára; Hostettler, Carmen; Marafino, John; Mainiero, Samantha; Vaughan, Cara K.; Monroe, Jonathan D.; Zeeman, Samuel C.

    2011-01-01

    Plants contain β-amylase–like proteins (BAMs; enzymes usually associated with starch breakdown) present in the nucleus rather than targeted to the chloroplast. They possess BRASSINAZOLE RESISTANT1 (BZR1)-type DNA binding domains—also found in transcription factors mediating brassinosteroid (BR) responses. The two Arabidopsis thaliana BZR1-BAM proteins (BAM7 and BAM8) bind a cis-regulatory element that both contains a G box and resembles a BR-responsive element. In protoplast transactivation assays, these BZR1-BAMs activate gene expression. Structural modeling suggests that the BAM domain’s glucan binding cleft is intact, but the recombinant proteins are at least 1000 times less active than chloroplastic β-amylases. Deregulation of BZR1-BAMs (the bam7bam8 double mutant and BAM8-overexpressing plants) causes altered leaf growth and development. Of the genes upregulated in plants overexpressing BAM8 and downregulated in bam7bam8 plants, many carry the cis-regulatory element in their promoters. Many genes that respond to BRs are inversely regulated by BZR1-BAMs. We propose a role for BZR1-BAMs in controlling plant growth and development through crosstalk with BR signaling. Furthermore, we speculate that BZR1-BAMs may transmit metabolic signals by binding a ligand in their BAM domain, although diurnal changes in the concentration of maltose, a candidate ligand produced by chloroplastic β-amylases, do not influence their transcription factor function. PMID:21487098

  9. An auxin-mediated shift toward growth isotropy promotes organ formation at the shoot meristem in Arabidopsis.

    PubMed

    Sassi, Massimiliano; Ali, Olivier; Boudon, Frédéric; Cloarec, Gladys; Abad, Ursula; Cellier, Coralie; Chen, Xu; Gilles, Benjamin; Milani, Pascale; Friml, Jiří; Vernoux, Teva; Godin, Christophe; Hamant, Olivier; Traas, Jan

    2014-10-01

    To control morphogenesis, molecular regulatory networks have to interfere with the mechanical properties of the individual cells of developing organs and tissues, but how this is achieved is not well known. We study this issue here in the shoot meristem of higher plants, a group of undifferentiated cells where complex changes in growth rates and directions lead to the continuous formation of new organs. Here, we show that the plant hormone auxin plays an important role in this process via a dual, local effect on the extracellular matrix, the cell wall, which determines cell shape. Our study reveals that auxin not only causes a limited reduction in wall stiffness but also directly interferes with wall anisotropy via the regulation of cortical microtubule dynamics. We further show that to induce growth isotropy and organ outgrowth, auxin somehow interferes with the cortical microtubule-ordering activity of a network of proteins, including AUXIN BINDING PROTEIN 1 and KATANIN 1. Numerical simulations further indicate that the induced isotropy is sufficient to amplify the effects of the relatively minor changes in wall stiffness to promote organogenesis and the establishment of new growth axes in a robust manner. PMID:25264254

  10. Cytokinin is required for escape but not release from auxin mediated apical dominance.

    PubMed

    Müller, Dörte; Waldie, Tanya; Miyawaki, Kaori; To, Jennifer P C; Melnyk, Charles W; Kieber, Joseph J; Kakimoto, Tatsuo; Leyser, Ottoline

    2015-06-01

    Auxin produced by an active primary shoot apex is transported down the main stem and inhibits the growth of the axillary buds below it, contributing to apical dominance. Here we use Arabidopsis thaliana cytokinin (CK) biosynthetic and signalling mutants to probe the role of CK in this process. It is well established that bud outgrowth is promoted by CK, and that CK synthesis is inhibited by auxin, leading to the hypothesis that release from apical dominance relies on an increased supply of CK to buds. Our data confirm that decapitation induces the expression of at least one ISOPENTENYLTRANSFERASE (IPT) CK biosynthetic gene in the stem. We further show that transcript abundance of a clade of the CK-responsive type-A Arabidopsis response regulator (ARR) genes increases in buds following CK supply, and that, contrary to their typical action as inhibitors of CK signalling, these genes are required for CK-mediated bud activation. However, analysis of the relevant arr and ipt multiple mutants demonstrates that defects in bud CK response do not affect auxin-mediated bud inhibition, and increased IPT transcript levels are not needed for bud release following decapitation. Instead, our data suggest that CK acts to overcome auxin-mediated bud inhibition, allowing buds to escape apical dominance under favourable conditions, such as high nitrate availability. PMID:25904120

  11. Arabidopsis Cytokinin Receptor Mutants Reveal Functions in Shoot Growth, Leaf Senescence, Seed Size, Germination, Root Development, and Cytokinin MetabolismW⃞

    PubMed Central

    Riefler, Michael; Novak, Ondrej; Strnad, Miroslav; Schmülling, Thomas

    2006-01-01

    We used loss-of-function mutants to study three Arabidopsis thaliana sensor histidine kinases, AHK2, AHK3, and CRE1/AHK4, known to be cytokinin receptors. Mutant seeds had more rapid germination, reduced requirement for light, and decreased far-red light sensitivity, unraveling cytokinin functions in seed germination control. Triple mutant seeds were more than twice as large as wild-type seeds. Genetic analysis indicated a cytokinin-dependent endospermal and/or maternal control of embryo size. Unchanged red light sensitivity of mutant hypocotyl elongation suggests that previously reported modulation of red light signaling by A-type response regulators may not depend on cytokinin. Combined loss of AHK2 and AHK3 led to the most prominent changes during vegetative development. Leaves of ahk2 ahk3 mutants formed fewer cells, had reduced chlorophyll content, and lacked the cytokinin-dependent inhibition of dark-induced chlorophyll loss, indicating a prominent role of AHK2 and, particularly, AHK3 in the control of leaf development. ahk2 ahk3 double mutants developed a strongly enhanced root system through faster growth of the primary root and, more importantly, increased branching. This result supports a negative regulatory role for cytokinin in root growth regulation. Increased cytokinin content of receptor mutants indicates a homeostatic control of steady state cytokinin levels through signaling. Together, the analyses reveal partially redundant functions of the cytokinin receptors and prominent roles for the AHK2/AHK3 receptor combination in quantitative control of organ growth in plants, with opposite regulatory functions in roots and shoots. PMID:16361392

  12. Seed Production Affects Maternal Growth and Senescence in Arabidopsis.

    PubMed

    Wuest, Samuel Elias; Philipp, Matthias Anton; Guthörl, Daniela; Schmid, Bernhard; Grossniklaus, Ueli

    2016-05-01

    Correlative control (influence of one organ over another organ) of seeds over maternal growth is one of the most obvious phenotypic expressions of the trade-off between growth and reproduction. However, the underlying molecular mechanisms are largely unknown. Here, we characterize the physiological and molecular effects of correlative inhibition by seeds on Arabidopsis (Arabidopsis thaliana) inflorescences, i.e. global proliferative arrest (GPA) during which all maternal growth ceases upon the production of a given number of seeds. We observed transcriptional responses to growth- and branching-inhibitory hormones, and low mitotic activity in meristems upon GPA, but found that meristems retain their identity and proliferative potential. In shoot tissues, we detected the induction of stress- and senescence-related gene expression upon fruit production and GPA, and a drop in chlorophyll levels, suggestive of altered source-sink relationships between vegetative shoot and reproductive tissues. Levels of shoot reactive oxygen species, however, strongly decreased upon GPA, a phenomenon that is associated with bud dormancy in some perennials. Indeed, gene expression changes in arrested apical inflorescences after fruit removal resembled changes observed in axillary buds following release from apical dominance. This suggests that GPA represents a form of bud dormancy, and that dominance is gradually transferred from growing inflorescences to maturing seeds, allowing offspring control over maternal resources, simultaneously restricting offspring number. This would provide a mechanistic explanation for the constraint between offspring quality and quantity. PMID:27009281

  13. Strigolactone regulation of shoot branching in chrysanthemum (Dendranthema grandiflorum).

    PubMed

    Liang, Jianli; Zhao, Liangjun; Challis, Richard; Leyser, Ottoline

    2010-06-01

    Previous studies of highly branched mutants in pea (rms1-rms5), Arabidopsis thaliana (max1-max4), petunia (dad1-dad3), and rice (d3, d10, htd1/d17, d14, d27) identified strigolactones or their derivates (SLs), as shoot branching inhibitors. This recent discovery offers the possibility of using SLs to regulate branching commercially, for example, in chrysanthemum, an important cut flower crop. To investigate this option, SL physiology and molecular biology were studied in chrysanthemum (Dendranthema grandiflorum), focusing on the CCD8/MAX4/DAD1/RMS1/D10 gene. Our results suggest that, as has been proposed for Arabidopsis, the ability of SLs to inhibit bud activity depends on the presence of a competing auxin source. The chrysanthemum SL biosynthesis gene, CCD8 was cloned, and found to be regulated in a similar, but not identical way to known CCD8s. Expression analyses revealed that DgCCD8 is predominantly expressed in roots and stems, and is up-regulated by exogenous auxin. Exogenous SL can down-regulate DgCCD8 expression, but this effect can be overridden by apical auxin application. This study provides evidence that SLs are promising candidates to alter the shoot branching habit of chrysanthemum. PMID:20478970

  14. SLAH1, a homologue of the slow type anion channel SLAC1, modulates shoot Cl− accumulation and salt tolerance in Arabidopsis thaliana

    PubMed Central

    Qiu, Jiaen; Henderson, Sam W; Tester, Mark; Roy, Stuart J; Gilliham, Mathew

    2016-01-01

    Salinity tolerance is correlated with shoot chloride (Cl–) exclusion in multiple crops, but the molecular mechanisms of long-distance Cl– transport are poorly defined. Here, we characterize the in planta role of AtSLAH1 (a homologue of the slow type anion channel-associated 1 (SLAC1)). This protein, localized to the plasma membrane of root stelar cells, has its expression reduced by salt or ABA, which are key predictions for a protein involved with loading Cl– into the root xylem. Artificial microRNA knockdown mutants of AtSLAH1 had significantly reduced shoot Cl− accumulation when grown under low Cl–, whereas shoot Cl– increased and the shoot nitrate/chloride ratio decreased following AtSLAH1 constitutive or stelar-specific overexpression when grown in high Cl–. In both sets of overexpression lines a significant reduction in shoot biomass over the null segregants was observed under high Cl– supply, but not low Cl– supply. Further in planta data showed AtSLAH3 overexpression increased the shoot nitrate/chloride ratio, consistent with AtSLAH3 favouring nitrate transport. Heterologous expression of AtSLAH1 in Xenopus laevis oocytes led to no detectible transport, suggesting the need for post-translational modifications for AtSLAH1 to be active. Our in planta data are consistent with AtSLAH1 having a role in controlling root-to-shoot Cl– transport. PMID:27340232

  15. SLAH1, a homologue of the slow type anion channel SLAC1, modulates shoot Cl- accumulation and salt tolerance in Arabidopsis thaliana.

    PubMed

    Qiu, Jiaen; Henderson, Sam W; Tester, Mark; Roy, Stuart J; Gilliham, Mathew

    2016-08-01

    Salinity tolerance is correlated with shoot chloride (Cl(-)) exclusion in multiple crops, but the molecular mechanisms of long-distance Cl(-) transport are poorly defined. Here, we characterize the in planta role of AtSLAH1 (a homologue of the slow type anion channel-associated 1 (SLAC1)). This protein, localized to the plasma membrane of root stelar cells, has its expression reduced by salt or ABA, which are key predictions for a protein involved with loading Cl(-) into the root xylem. Artificial microRNA knockdown mutants of AtSLAH1 had significantly reduced shoot Cl(-) accumulation when grown under low Cl(-), whereas shoot Cl(-) increased and the shoot nitrate/chloride ratio decreased following AtSLAH1 constitutive or stelar-specific overexpression when grown in high Cl(-) In both sets of overexpression lines a significant reduction in shoot biomass over the null segregants was observed under high Cl(-) supply, but not low Cl(-) supply. Further in planta data showed AtSLAH3 overexpression increased the shoot nitrate/chloride ratio, consistent with AtSLAH3 favouring nitrate transport. Heterologous expression of AtSLAH1 in Xenopus laevis oocytes led to no detectible transport, suggesting the need for post-translational modifications for AtSLAH1 to be active. Our in planta data are consistent with AtSLAH1 having a role in controlling root-to-shoot Cl(-) transport. PMID:27340232

  16. UV-B Induced Generation of Reactive Oxygen Species Promotes Formation of BFA-Induced Compartments in Cells of Arabidopsis Root Apices

    PubMed Central

    Yokawa, Ken; Kagenishi, Tomoko; Baluška, František

    2016-01-01

    UV-B radiation is an important part of the electromagnetic spectrum emitted by the sun. For much of the period of biological evolution organisms have been exposed to UV radiation, and have developed diverse mechanisms to cope with this potential stress factor. Roots are usually shielded from exposure to UV by the surrounding soil, but may nevertheless be exposed to high energy radiation on the soil surface. Due to their high sensitivity to UV-B radiation, plant roots need to respond rapidly in order to minimize exposure on the surface. In addition to root gravitropism, effective light perception by roots has recently been discovered to be essential for triggering negative root phototropism in Arabidopsis. However, it is not fully understood how UV-B affects root growth and phototropism. Here, we report that UV-B induces rapid generation of reactive oxygen species which in turn promotes the formation of BFA-induced compartments in the Arabidopsis root apex. During unilateral UV-B irradiation of roots changes in auxin concentration on the illuminated side have been recorded. In conclusion, UV-B-induced and ROS-mediated stimulation of vesicle recycling promotes root growth and induces negative phototropism. PMID:26793199

  17. UV-B Induced Generation of Reactive Oxygen Species Promotes Formation of BFA-Induced Compartments in Cells of Arabidopsis Root Apices.

    PubMed

    Yokawa, Ken; Kagenishi, Tomoko; Baluška, František

    2015-01-01

    UV-B radiation is an important part of the electromagnetic spectrum emitted by the sun. For much of the period of biological evolution organisms have been exposed to UV radiation, and have developed diverse mechanisms to cope with this potential stress factor. Roots are usually shielded from exposure to UV by the surrounding soil, but may nevertheless be exposed to high energy radiation on the soil surface. Due to their high sensitivity to UV-B radiation, plant roots need to respond rapidly in order to minimize exposure on the surface. In addition to root gravitropism, effective light perception by roots has recently been discovered to be essential for triggering negative root phototropism in Arabidopsis. However, it is not fully understood how UV-B affects root growth and phototropism. Here, we report that UV-B induces rapid generation of reactive oxygen species which in turn promotes the formation of BFA-induced compartments in the Arabidopsis root apex. During unilateral UV-B irradiation of roots changes in auxin concentration on the illuminated side have been recorded. In conclusion, UV-B-induced and ROS-mediated stimulation of vesicle recycling promotes root growth and induces negative phototropism. PMID:26793199

  18. Auxin controls local cytokinin biosynthesis in the nodal stem in apical dominance.

    PubMed

    Tanaka, Mina; Takei, Kentaro; Kojima, Mikiko; Sakakibara, Hitoshi; Mori, Hitoshi

    2006-03-01

    In intact plants, the shoot apex grows predominantly and inhibits outgrowth of axillary buds. After decapitation of the shoot apex, outgrowth of axillary buds begins. This phenomenon is called an apical dominance. Although the involvement of auxin, which represses outgrowth of axillary buds, and cytokinin (CK), which promotes outgrowth of axillary buds, has been proposed, little is known about the underlying molecular mechanisms. In the present study, we demonstrated that auxin negatively regulates local CK biosynthesis in the nodal stem by controlling the expression level of the pea (Pisum sativum L.) gene adenosine phosphate-isopentenyltransferase (PsIPT), which encodes a key enzyme in CK biosynthesis. Before decapitation, PsIPT1 and PsIPT2 transcripts were undetectable; after decapitation, they were markedly induced in the nodal stem along with accumulation of CK. Expression of PsIPT was repressed by the application of indole-3-acetic acid (IAA). In excised nodal stem, PsIPT expression and CK levels also increased under IAA-free conditions. Furthermore, beta-glucuronidase expression, under the control of the PsIPT2 promoter region in transgenic Arabidopsis, was repressed by an IAA. Our results indicate that in apical dominance one role of auxin is to repress local biosynthesis of CK in the nodal stem and that, after decapitation, CKs, which are thought to be derived from the roots, are locally biosynthesized in the nodal stem rather than in the roots. PMID:16507092

  19. Arabidopsis florigen FT binds to diurnally oscillating phospholipids that accelerate flowering

    PubMed Central

    Nakamura, Yuki; Andrés, Fernando; Kanehara, Kazue; Liu, Yu-chi; Dörmann, Peter; Coupland, George

    2014-01-01

    Arabidopsis FT protein is a component of florigen, which transmits photoperiodic flowering signals from leaf companion cells to the shoot apex. Here, we show that FT specifically binds phosphatidylcholine (PC) in vitro. A transgenic approach to increase PC levels in vivo in the shoot meristem accelerates flowering whereas reduced PC levels delay flowering, demonstrating that PC levels are correlated with flowering time. The early flowering is related to FT activity, because expression of FT-effector genes is increased in these plants. Simultaneous increase of FT and PC in the shoot apical meristem further stimulates flowering, whereas a loss of FT function leads to an attenuation of the effect of increased PC. Specific molecular species of PC oscillate diurnally, and night-dominant species are not the preferred ligands of FT. Elevating night-dominant species during the day delays flowering. We suggest that FT binds to diurnally changing molecular species of PC to promote flowering. PMID:24698997

  20. Changing the spatial pattern of TFL1 expression reveals its key role in the shoot meristem in controlling Arabidopsis flowering architecture

    PubMed Central

    Baumann, Kim; Venail, Julien; Berbel, Ana; Domenech, Maria Jose; Money, Tracy; Conti, Lucio; Hanzawa, Yoshie; Madueno, Francisco; Bradley, Desmond

    2015-01-01

    Models for the control of above-ground plant architectures show how meristems can be programmed to be either shoots or flowers. Molecular, genetic, transgenic, and mathematical studies have greatly refined these models, suggesting that the phase of the shoot reflects different genes contributing to its repression of flowering, its vegetativeness (‘veg’), before activators promote flower development. Key elements of how the repressor of flowering and shoot meristem gene TFL1 acts have now been tested, by changing its spatiotemporal pattern. It is shown that TFL1 can act outside of its normal expression domain in leaf primordia or floral meristems to repress flower identity. These data show how the timing and spatial pattern of TFL1 expression affect overall plant architecture. This reveals that the underlying pattern of TFL1 interactors is complex and that they may be spatially more widespread than TFL1 itself, which is confined to shoots. However, the data show that while TFL1 and floral genes can both act and compete in the same meristem, it appears that the main shoot meristem is more sensitive to TFL1 rather than floral genes. This spatial analysis therefore reveals how a difference in response helps maintain the ‘veg’ state of the shoot meristem. PMID:26019254

  1. Strigolactone acts downstream of auxin to regulate bud outgrowth in pea and Arabidopsis.

    PubMed

    Brewer, Philip B; Dun, Elizabeth A; Ferguson, Brett J; Rameau, Catherine; Beveridge, Christine A

    2009-05-01

    During the last century, two key hypotheses have been proposed to explain apical dominance in plants: auxin promotes the production of a second messenger that moves up into buds to repress their outgrowth, and auxin saturation in the stem inhibits auxin transport from buds, thereby inhibiting bud outgrowth. The recent discovery of strigolactone as the novel shoot-branching inhibitor allowed us to test its mode of action in relation to these hypotheses. We found that exogenously applied strigolactone inhibited bud outgrowth in pea (Pisum sativum) even when auxin was depleted after decapitation. We also found that strigolactone application reduced branching in Arabidopsis (Arabidopsis thaliana) auxin response mutants, suggesting that auxin may act through strigolactones to facilitate apical dominance. Moreover, strigolactone application to tiny buds of mutant or decapitated pea plants rapidly stopped outgrowth, in contrast to applying N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, which significantly slowed growth only after several days. Whereas strigolactone or NPA applied to growing buds reduced bud length, only NPA blocked auxin transport in the bud. Wild-type and strigolactone biosynthesis mutant pea and Arabidopsis shoots were capable of instantly transporting additional amounts of auxin in excess of endogenous levels, contrary to predictions of auxin transport models. These data suggest that strigolactone does not act primarily by affecting auxin transport from buds. Rather, the primary repressor of bud outgrowth appears to be the auxin-dependent production of strigolactones. PMID:19321710

  2. Seed Production Affects Maternal Growth and Senescence in Arabidopsis1[OPEN

    PubMed Central

    Philipp, Matthias Anton; Guthörl, Daniela

    2016-01-01

    Correlative control (influence of one organ over another organ) of seeds over maternal growth is one of the most obvious phenotypic expressions of the trade-off between growth and reproduction. However, the underlying molecular mechanisms are largely unknown. Here, we characterize the physiological and molecular effects of correlative inhibition by seeds on Arabidopsis (Arabidopsis thaliana) inflorescences, i.e. global proliferative arrest (GPA) during which all maternal growth ceases upon the production of a given number of seeds. We observed transcriptional responses to growth- and branching-inhibitory hormones, and low mitotic activity in meristems upon GPA, but found that meristems retain their identity and proliferative potential. In shoot tissues, we detected the induction of stress- and senescence-related gene expression upon fruit production and GPA, and a drop in chlorophyll levels, suggestive of altered source-sink relationships between vegetative shoot and reproductive tissues. Levels of shoot reactive oxygen species, however, strongly decreased upon GPA, a phenomenon that is associated with bud dormancy in some perennials. Indeed, gene expression changes in arrested apical inflorescences after fruit removal resembled changes observed in axillary buds following release from apical dominance. This suggests that GPA represents a form of bud dormancy, and that dominance is gradually transferred from growing inflorescences to maturing seeds, allowing offspring control over maternal resources, simultaneously restricting offspring number. This would provide a mechanistic explanation for the constraint between offspring quality and quantity. PMID:27009281

  3. FASCIATED EAR4 encodes a bZIP transcription factor that regulates shoot meristem size in maize.

    PubMed

    Pautler, Michael; Eveland, Andrea L; LaRue, Therese; Yang, Fang; Weeks, Rebecca; Lunde, China; Je, Byoung Il; Meeley, Robert; Komatsu, Mai; Vollbrecht, Erik; Sakai, Hajime; Jackson, David

    2015-01-01

    Plant architecture is dictated by precise control of meristematic activity. In the shoot, an imbalance in positive or negative maintenance signals can result in a fasciated or enlarged meristem phenotype. fasciated ear4 (fea4) is a semidwarfed mutant with fasciated ears and tassels as well as greatly enlarged vegetative and inflorescence meristems. We identified FEA4 as a bZIP transcription factor, orthologous to Arabidopsis thaliana PERIANTHIA. FEA4 was expressed in the peripheral zone of the vegetative shoot apical meristem and in the vasculature of immature leaves and conspicuously excluded from the stem cell niche at the tip of the shoot apical meristem and from incipient leaf primordia. Following the transition to reproductive fate, FEA4 was expressed throughout the entire inflorescence and floral meristems. Native expression of a functional YFP:FEA4 fusion recapitulated this pattern of expression. We used chromatin immunoprecipitation-sequencing to identify 4060 genes proximal to FEA4 binding sites, including ones that were potentially bound and modulated by FEA4 based on transcriptional changes in fea4 mutant ears. Our results suggest that FEA4 promotes differentiation in the meristem periphery by regulating auxin-based responses and genes associated with leaf differentiation and polarity, potentially in opposition to factors such as KNOTTED1 and WUSCHEL. PMID:25616871

  4. Proteomic Identification of Putative MicroRNA394 Target Genes in Arabidopsis thaliana Identifies Major Latex Protein Family Members Critical for Normal Development.

    PubMed

    Litholdo, Celso G; Parker, Benjamin L; Eamens, Andrew L; Larsen, Martin R; Cordwell, Stuart J; Waterhouse, Peter M

    2016-06-01

    Expression of the F-Box protein Leaf Curling Responsiveness (LCR) is regulated by microRNA, miR394, and alterations to this interplay in Arabidopsis thaliana produce defects in leaf polarity and shoot apical meristem organization. Although the miR394-LCR node has been documented in Arabidopsis, the identification of proteins targeted by LCR F-box itself has proven problematic. Here, a proteomic analysis of shoot apices from plants with altered LCR levels identified a member of the Latex Protein (MLP) family gene as a potential LCR F-box target. Bioinformatic and molecular analyses also suggested that other MLP family members are likely to be targets for this post-translational regulation. Direct interaction between LCR F-Box and MLP423 was validated. Additional MLP members had reduction in protein accumulation, in varying degrees, mediated by LCR F-Box. Transgenic Arabidopsis lines, in which MLP28 expression was reduced through an artificial miRNA technology, displayed severe developmental defects, including changes in leaf patterning and morphology, shoot apex defects, and eventual premature death. These phenotypic characteristics resemble those of Arabidopsis plants modified to over-express LCR Taken together, the results demonstrate that MLPs are driven to degradation by LCR, and indicate that MLP gene family is target of miR394-LCR regulatory node, representing potential targets for directly post-translational regulation mediated by LCR F-Box. In addition, MLP28 family member is associated with the LCR regulation that is critical for normal Arabidopsis development. PMID:27067051

  5. Microdissection of Shoot Meristem Functional Domains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The shoot apical meristem (SAM) maintains a pool of indeterminate cells within the SAM proper, while lateral organs are initiated from the SAM periphery. Laser microdissection–microarray technology was used to compare transcriptional profiles within these SAM domains to identify novel maize genes th...

  6. OBE3 and WUS Interaction in Shoot Meristem Stem Cell Regulation

    PubMed Central

    Lin, Ta-Fang; Saiga, Shunsuke; Abe, Mitsutomo; Laux, Thomas

    2016-01-01

    The stem cells in the shoot apical meristem (SAM) are the origin of all above ground tissues in plants. In Arabidopsis thaliana, shoot meristem stem cells are maintained by the homeobox transcription factor gene WUS (WUSCHEL) that is expressed in cells of the organizing center underneath the stem cells. In order to identify factors that operate together with WUS in stem cell maintenance, we performed an EMS mutant screen for modifiers of the hypomorphic wus-6 allele. We isolated the oberon3-2 (obe3-2) mutant that enhances stem cell defects in wus-6, but does not affect the putative null allele wus-1. The OBE3 gene encodes a PHD (Plant Homeo Domain) protein that is thought to function in chromatin regulation. Single mutants of OBE3 or its closest homolog OBE4 do not display any defects, whereas the obe3-2 obe4-2 double mutant displays broad growth defects and developmental arrest of seedlings. Transcript levels of WUS and its target gene in the stem cells, CLAVATA3, are reduced in obe3-2. On the other hand, OBE3 and OBE4 transcripts are both indirectly upregulated by ectopic WUS expression. Our results suggest a positive feedback regulation between WUS and OBE3 that contributes to shoot meristem homeostasis. PMID:27196372

  7. OBE3 and WUS Interaction in Shoot Meristem Stem Cell Regulation.

    PubMed

    Lin, Ta-Fang; Saiga, Shunsuke; Abe, Mitsutomo; Laux, Thomas

    2016-01-01

    The stem cells in the shoot apical meristem (SAM) are the origin of all above ground tissues in plants. In Arabidopsis thaliana, shoot meristem stem cells are maintained by the homeobox transcription factor gene WUS (WUSCHEL) that is expressed in cells of the organizing center underneath the stem cells. In order to identify factors that operate together with WUS in stem cell maintenance, we performed an EMS mutant screen for modifiers of the hypomorphic wus-6 allele. We isolated the oberon3-2 (obe3-2) mutant that enhances stem cell defects in wus-6, but does not affect the putative null allele wus-1. The OBE3 gene encodes a PHD (Plant Homeo Domain) protein that is thought to function in chromatin regulation. Single mutants of OBE3 or its closest homolog OBE4 do not display any defects, whereas the obe3-2 obe4-2 double mutant displays broad growth defects and developmental arrest of seedlings. Transcript levels of WUS and its target gene in the stem cells, CLAVATA3, are reduced in obe3-2. On the other hand, OBE3 and OBE4 transcripts are both indirectly upregulated by ectopic WUS expression. Our results suggest a positive feedback regulation between WUS and OBE3 that contributes to shoot meristem homeostasis. PMID:27196372

  8. A Journey Through a Leaf: Phenomics Analysis of Leaf Growth in Arabidopsis thaliana

    PubMed Central

    Vanhaeren, Hannes; Gonzalez, Nathalie; Inzé, Dirk

    2015-01-01

    In Arabidopsis, leaves contribute to the largest part of the aboveground biomass. In these organs, light is captured and converted into chemical energy, which plants use to grow and complete their life cycle. Leaves emerge as a small pool of cells at the vegetative shoot apical meristem and develop into planar, complex organs through different interconnected cellular events. Over the last decade, numerous phenotyping techniques have been developed to visualize and quantify leaf size and growth, leading to the identification of numerous genes that contribute to the final size of leaves. In this review, we will start at the Arabidopsis rosette level and gradually zoom in from a macroscopic view on leaf growth to a microscopic and molecular view. Along this journey, we describe different techniques that have been key to identify important events during leaf development and discuss approaches that will further help unraveling the complex cellular and molecular mechanisms that underlie leaf growth. PMID:26217168

  9. The CUP-SHAPED COTYLEDON2 and 3 genes have a post-meristematic effect on Arabidopsis thaliana phyllotaxis

    PubMed Central

    Burian, Agata; Raczyńska-Szajgin, Magdalena; Borowska-Wykręt, Dorota; Piatek, Agnieszka; Aida, Mitsuhiro; Kwiatkowska, Dorota

    2015-01-01

    Background and Aims The arrangement of flowers in inflorescence shoots of Arabidopsis thaliana represents a regular spiral Fibonacci phyllotaxis. However, in the cuc2 cuc3 double mutant, flower pedicels are fused to the inflorescence stem, and phyllotaxis is aberrant in the mature shoot regions. This study examined the causes of this altered development, and in particular whether the mutant phenotype is a consequence of defects at the shoot apex, or whether post-meristematic events are involved. Methods The distribution of flower pedicels and vascular traces was examined in cross-sections of mature shoots; sequential replicas were used to investigate the phyllotaxis and geometry of shoot apices, and growth of the young stem surface. The expression pattern of CUC3 was analysed by examining its promoter activity. Key Results Phyllotaxis irregularity in the cuc2 cuc3 double mutant arises during the post-meristematic phase of shoot development. In particular, growth and cell divisions in nodes of the elongating stem are not restricted in the mutant, resulting in pedicel–stem fusion. On the other hand, phyllotaxis in the mutant shoot apex is nearly as regular as that of the wild type. Vascular phyllotaxis, generated almost simultaneously with the phyllotaxis at the apex, is also much more regular than pedicel phyllotaxis. The most apparent phenotype of the mutant apices is a higher number of contact parastichies. This phenotype is associated with increased meristem size, decreased angular width of primordia and a shorter plastochron. In addition, the appearance of a sharp and deep crease, a characteristic shape of the adaxial primordium boundary, is slightly delayed and reduced in the mutant shoot apices. Conclusions The cuc2 cuc3 double mutant displays irregular phyllotaxis in the mature shoot but not in the shoot apex, thus showing a post-meristematic effect of the mutations on phyllotaxis. The main cause of this effect is the formation of pedicel–stem fusions

  10. Interactions between axillary branches of Arabidopsis.

    PubMed

    Ongaro, Veronica; Bainbridge, Katherine; Williamson, Lisa; Leyser, Ottoline

    2008-03-01

    Studies of apical dominance have benefited greatly from two-branch assays in pea and bean, in which the shoot system is trimmed back to leave only two active cotyledonary axillary branches. In these two-branch shoots, a large body of evidence shows that one actively growing branch is able to inhibit the growth of the other, prompting studies on the nature of the inhibitory signals, which are still poorly understood. Here, we describe the establishment of two-branch assays in Arabidopsis, using consecutive branches on the bolting stem. As with the classical studies in pea and bean, these consecutive branches are able to inhibit one another's growth. Not only can the upper branch inhibit the lower branch, but also the lower branch can inhibit the upper branch, illustrating the bi-directional action of the inhibitory signals. Using mutants, we show that the inhibition is partially dependent on the MAX pathway and that while the inhibition is clearly transmitted across the stem from the active to the inhibited branch, the vascular connectivity of the two branches is weak, and the MAX pathway is capable of acting unilaterally in the stem. PMID:19825548

  11. Co-Overexpression FIT with AtbHLH38 or AtbHLH39 in Arabidopsis-Enhanced Cadmium Tolerance via Increased Cadmium Sequestration in Roots and Improved Iron Homeostasis of Shoots1[W

    PubMed Central

    Wu, Huilan; Chen, Chunlin; Du, Juan; Liu, Hongfei; Cui, Yan; Zhang, Yue; He, Yujing; Wang, Yiqing; Chu, Chengcai; Feng, Zongyun; Li, Junming; Ling, Hong-Qing

    2012-01-01

    Cadmium (Cd) is toxic to plant cells. Under Cd exposure, the plant displayed leaf chlorosis, which is a typical symptom of iron (Fe) deficiency. Interactions of Cd with Fe have been reported. However, the molecular mechanisms of Cd-Fe interactions are not well understood. Here, we showed that FER-like Deficiency Induced Transcripition Factor (FIT), AtbHLH38, and AtbHLH39, three basic helix-loop-helix transcription factors involved in Fe homeostasis in plants, also play important roles in Cd tolerance. The gene expression analysis showed that the expression of FIT, AtbHLH38, and AtbHLH39 was up-regulated in the roots of plants treated with Cd. The plants overexpressing AtbHLH39 and double-overexpressing FIT/AtbHLH38 and FIT/AtbHLH39 exhibited more tolerance to Cd exposure than wild type, whereas no Cd tolerance was observed in plants overexpressing either AtbHLH38 or FIT. Further analysis revealed that co-overexpression of FIT with AtbHLH38 or AtbHLH39 constitutively activated the expression of Heavy Metal Associated3 (HMA3), Metal Tolerance Protein3 (MTP3), Iron Regulated Transporter2 (IRT2), and Iron Regulated Gene2 (IREG2), which are involved in the heavy metal detoxification in Arabidopsis (Arabidopis thaliana). Moreover, co-overexpression of FIT with AtbHLH38 or AtbHLH39 also enhanced the expression of NICOTIANAMINE SYNTHETASE1 (NAS1) and NAS2, resulting in the accumulation of nicotiananamine, a crucial chelator for Fe transportation and homeostasis. Finally, we showed that maintaining high Fe content in shoots under Cd exposure could alleviate the Cd toxicity. Our results provide new insight to understand the molecular mechanisms of Cd tolerance in plants. PMID:22184655

  12. Repression of Lateral Organ Boundary Genes by PENNYWISE and POUND-FOOLISH Is Essential for Meristem Maintenance and Flowering in Arabidopsis1[OPEN

    PubMed Central

    Khan, Madiha; Ragni, Laura; Tabb, Paul; Salasini, Brenda C.; Chatfield, Steven; Datla, Raju; Lock, John; Kuai, Xiahezi; Després, Charles; Proveniers, Marcel; Yongguo, Cao; Xiang, Daoquan; Morin, Halima; Rullière, Jean-Pierre; Citerne, Sylvie; Hepworth, Shelley R.; Pautot, Véronique

    2015-01-01

    In the model plant Arabidopsis (Arabidopsis thaliana), endogenous and environmental signals acting on the shoot apical meristem cause acquisition of inflorescence meristem fate. This results in changed patterns of aerial development seen as the transition from making leaves to the production of flowers separated by elongated internodes. Two related BEL1-like homeobox genes, PENNYWISE (PNY) and POUND-FOOLISH (PNF), fulfill this transition. Loss of function of these genes impairs stem cell maintenance and blocks internode elongation and flowering. We show here that pny pnf apices misexpress lateral organ boundary genes BLADE-ON-PETIOLE1/2 (BOP1/2) and KNOTTED-LIKE FROM ARABIDOPSIS THALIANA6 (KNAT6) together with ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1). Inactivation of genes in this module fully rescues pny pnf defects. We further show that BOP1 directly activates ATH1, whereas activation of KNAT6 is indirect. The pny pnf restoration correlates with renewed accumulation of transcripts conferring floral meristem identity, including FD, SQUAMOSA PROMOTER-BINDING PROTEIN LIKE genes, LEAFY, and APETALA1. To gain insight into how this module blocks flowering, we analyzed the transcriptome of BOP1-overexpressing plants. Our data suggest a central role for the microRNA156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE-microRNA172 module in integrating stress signals conferred in part by promotion of jasmonic acid biosynthesis. These data reveal a potential mechanism by which repression of lateral organ boundary genes by PNY-PNF is essential for flowering. PMID:26417006

  13. Repression of Lateral Organ Boundary Genes by PENNYWISE and POUND-FOOLISH Is Essential for Meristem Maintenance and Flowering in Arabidopsis.

    PubMed

    Khan, Madiha; Ragni, Laura; Tabb, Paul; Salasini, Brenda C; Chatfield, Steven; Datla, Raju; Lock, John; Kuai, Xiahezi; Després, Charles; Proveniers, Marcel; Yongguo, Cao; Xiang, Daoquan; Morin, Halima; Rullière, Jean-Pierre; Citerne, Sylvie; Hepworth, Shelley R; Pautot, Véronique

    2015-11-01

    In the model plant Arabidopsis (Arabidopsis thaliana), endogenous and environmental signals acting on the shoot apical meristem cause acquisition of inflorescence meristem fate. This results in changed patterns of aerial development seen as the transition from making leaves to the production of flowers separated by elongated internodes. Two related BEL1-like homeobox genes, PENNYWISE (PNY) and POUND-FOOLISH (PNF), fulfill this transition. Loss of function of these genes impairs stem cell maintenance and blocks internode elongation and flowering. We show here that pny pnf apices misexpress lateral organ boundary genes BLADE-ON-PETIOLE1/2 (BOP1/2) and KNOTTED-LIKE FROM ARABIDOPSIS THALIANA6 (KNAT6) together with ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1). Inactivation of genes in this module fully rescues pny pnf defects. We further show that BOP1 directly activates ATH1, whereas activation of KNAT6 is indirect. The pny pnf restoration correlates with renewed accumulation of transcripts conferring floral meristem identity, including FD, SQUAMOSA PROMOTER-BINDING PROTEIN LIKE genes, LEAFY, and APETALA1. To gain insight into how this module blocks flowering, we analyzed the transcriptome of BOP1-overexpressing plants. Our data suggest a central role for the microRNA156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE-microRNA172 module in integrating stress signals conferred in part by promotion of jasmonic acid biosynthesis. These data reveal a potential mechanism by which repression of lateral organ boundary genes by PNY-PNF is essential for flowering. PMID:26417006

  14. Separate elements of the TERMINAL FLOWER 1 cis-regulatory region integrate pathways to control flowering time and shoot meristem identity.

    PubMed

    Serrano-Mislata, Antonio; Fernández-Nohales, Pedro; Doménech, María J; Hanzawa, Yoshie; Bradley, Desmond; Madueño, Francisco

    2016-09-15

    TERMINAL FLOWER 1 (TFL1) is a key regulator of Arabidopsis plant architecture that responds to developmental and environmental signals to control flowering time and the fate of shoot meristems. TFL1 expression is dynamic, being found in all shoot meristems, but not in floral meristems, with the level and distribution changing throughout development. Using a variety of experimental approaches we have analysed the TFL1 promoter to elucidate its functional structure. TFL1 expression is based on distinct cis-regulatory regions, the most important being located 3' of the coding sequence. Our results indicate that TFL1 expression in the shoot apical versus lateral inflorescence meristems is controlled through distinct cis-regulatory elements, suggesting that different signals control expression in these meristem types. Moreover, we identified a cis-regulatory region necessary for TFL1 expression in the vegetative shoot and required for a wild-type flowering time, supporting that TFL1 expression in the vegetative meristem controls flowering time. Our study provides a model for the functional organisation of TFL1 cis-regulatory regions, contributing to our understanding of how developmental pathways are integrated at the genomic level of a key regulator to control plant architecture. PMID:27385013

  15. Arabidopsis cold shock domain proteins: relationships to floral and silique development

    PubMed Central

    Nakaminami, Kentaro; Hill, Kristine; Perry, Sharyn E.; Sentoku, Naoki; Long, Jeffrey A.; Karlson, Dale T.

    2009-01-01

    Cold shock domain proteins (CSPs) are highly conserved from bacteria to higher plants and animals. Bacterial cold shock proteins function as RNA chaperones by destabilizing RNA secondary structures and promoting translation as an adaptative mechanism to low temperature stress. In animals, cold shock domain proteins exhibit broad functions related to growth and development. In order to understand better the function of CSPs in planta, detailed analyses were performed for Arabidopsis thaliana CSPs (AtCSPs) on the transcript and protein levels using an extensive series of tissue harvested throughout developmental stages within the entire life cycle of Arabidopsis. On both the transcript and protein levels, AtCSPs were enriched in shoot apical meristems and siliques. Although all AtCSPs exhibited similar expression patterns, AtCSP2 was the most abundantly expressed gene. In situ hybridization analyses were also used to confirm that AtCSP2 and AtCSP4 transcripts accumulate in developing embryos and shoot apices. AtCSPs transcripts were also induced during a controlled floral induction study. In vivo ChIP analysis confirmed that an embryo expressed MADS box transcription factor, AGL15, interacts within two AtCSP promoter regions and alters the respective patterns of AtCSP transcription. Comparative analysis of AtCSP gene expression between Landsberg and Columbia ecotypes confirmed a 1000-fold reduction of AtCSP4 gene expression in the Landsberg background. Analysis of the AtCSP4 genomic locus identified multiple polymorphisms in putative regulatory cis-elements between the two ecotypes. Collectively, these data support the hypothesis that AtCSPs are involved in the transition to flowering and silique development in Arabidopsis. PMID:19269998

  16. MOL1 is required for cambium homeostasis in Arabidopsis.

    PubMed

    Gursanscky, Nial Rau; Jouannet, Virginie; Grünwald, Karin; Sanchez, Pablo; Laaber-Schwarz, Martina; Greb, Thomas

    2016-05-01

    Plants maintain pools of pluripotent stem cells which allow them to constantly produce new tissues and organs. Stem cell homeostasis in shoot and root tips depends on negative regulation by ligand-receptor pairs of the CLE peptide and leucine-rich repeat receptor-like kinase (LRR-RLK) families. However, regulation of the cambium, the stem cell niche required for lateral growth of shoots and roots, is poorly characterized. Here we show that the LRR-RLK MOL1 is necessary for cambium homeostasis in Arabidopsis thaliana. By employing promoter reporter lines, we reveal that MOL1 is active in a domain that is distinct from the domain of the positively acting CLE41/PXY signaling module. In particular, we show that MOL1 acts in an opposing manner to the CLE41/PXY module and that changing the domain or level of MOL1 expression both result in disturbed cambium organization. Underlining discrete roles of MOL1 and PXY, both LRR-RLKs are not able to replace each other when their expression domains are interchanged. Furthermore, MOL1 but not PXY is able to rescue CLV1 deficiency in the shoot apical meristem. By identifying genes mis-expressed in mol1 mutants, we demonstrate that MOL1 represses genes associated with stress-related ethylene and jasmonic acid hormone signaling pathways which have known roles in coordinating lateral growth of the Arabidopsis stem. Our findings provide evidence that common regulatory mechanisms in different plant stem cell niches are adapted to specific niche anatomies and emphasize the importance of a complex spatial organization of intercellular signaling cascades for a strictly bidirectional tissue production. PMID:26991973

  17. The role of mechanical forces in the shoot apical meristem

    NASA Astrophysics Data System (ADS)

    Steele, Charles

    2003-03-01

    The past work on the possible relation of mechanical instability of a shell surface to the patterns that develop in plants will be summarized. It is found that there is a linear relation between the epidermis (tunica) thickness and the wave length between new leaves (primordia). This relation is near the buckling wave length calculated from the geometry of the tunica and interior (corpus) cells. In recent work, the focus has been on the tip growth of root hairs, which is basic and deceptively simple. A single cell has a wall that is cylindrical with a prolate spheroid as an end cap. The growth takes place in the end cap. The measurements by S. Shaw provide detail of the shape of the end cap, and it is known that the mechanical loading which drives the growth consists of turgor pressure of magnitude 5 -10 atmospheres. However, the prolate spheroid has minumum stress at the apex where the growth is maximum. Recent work with J. Dumais toward understanding this paradox will be reported.

  18. Ferns: the missing link in shoot evolution and development

    PubMed Central

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

    2015-01-01

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

  19. AtLa1 protein initiates IRES-dependent translation of WUSCHEL mRNA and regulates the stem cell homeostasis of Arabidopsis in response to environmental hazards.

    PubMed

    Cui, Yuchao; Rao, Shaofei; Chang, Beibei; Wang, Xiaoshuang; Zhang, Kaidian; Hou, Xueliang; Zhu, Xueyi; Wu, Haijun; Tian, Zhaoxia; Zhao, Zhong; Yang, Chengwei; Huang, Tao

    2015-10-01

    Plant stem cells are hypersensitive to environmental hazards throughout their life cycle, but the mechanism by which plants safeguard stem cell homeostasis in response to environmental hazards is largely unknown. The homeodomain transcription factor WUSCHEL (WUS) protein maintains the stem cell pool in the shoot apical meristem of Arabidopsis. Here, we demonstrate that the translation of WUS mRNA is directed by an internal ribosomal entry site (IRES) located in the 5'-untranslated region. The AtLa1 protein, an RNA-binding factor, binds to the 5'-untranslated region and initiates the IRES-dependent translation of WUS mRNA. Knockdown of AtLa1 expression represses the WUS IRES-dependent translation and leads to the arrest of growth and development. The AtLa1 protein is mainly located in the nucleoplasm. However, environmental hazards promote the nuclear-to-cytoplasmic translocation of the AtLa1 protein, which further enhances the IRES-dependent translation of WUS mRNA. Genetic evidence indicates that the WUS protein increases the tolerance of the shoot apical meristem to environmental hazards. Based on these results, we conclude that the stem cell niche in Arabidopsis copes with environmental hazards by enhancing the IRES-dependent translation of WUS mRNA under the control of the AtLa1 protein. PMID:25764476

  20. Comparative Analysis of the Conserved Functions of Arabidopsis DRL1 and Yeast KTI12

    PubMed Central

    Jun, Sang Eun; Cho, Kiu-Hyung; Hwang, Ji-Young; Abdel-Fattah, Wael; Hammermeister, Alexander; Schaffrath, Raffael; Bowman, John L.; Kim, Gyung-Tae

    2015-01-01

    Patterning of the polar axis during the early leaf developmental stage is established by cell-to-cell communication between the shoot apical meristem (SAM) and the leaf primordia. In a previous study, we showed that the DRL1 gene, which encodes a homolog of the Elongator-associated protein KTI12 of yeast, acts as a positive regulator of adaxial leaf patterning and shoot meristem activity. To determine the evolutionally conserved functions of DRL1, we performed a comparison of the deduced amino acid sequence of DRL1 and its yeast homolog, KTI12, and found that while overall homology was low, well-conserved domains were presented. DRL1 contained two conserved plant-specific domains. Expression of the DRL1 gene in a yeast KTI12-deficient yeast mutant suppressed the growth retardation phenotype, but did not rescue the caffeine sensitivity, indicating that the role of Arabidopsis Elongator-associated protein is partially conserved with yeast KTI12, but may have changed between yeast and plants in response to caffeine during the course of evolution. In addition, elevated expression of DRL1 gene triggered zymocin sensitivity, while overexpression of KTI12 maintained zymocin resistance, indicating that the function of Arabidopsis DRL1 may not overlap with yeast KTI12 with regards to toxin sensitivity. In this study, expression analysis showed that class-I KNOX genes were downregulated in the shoot apex, and that YAB and KAN were upregulated in leaves of the Arabidopsis drl1-101 mutant. Our results provide insight into the communication network between the SAM and leaf primordia required for the establishment of leaf polarity by mediating histone acetylation or through other mechanisms. PMID:25518926

  1. Energy related germination and survival rates of water-imbibed Arabidopsis seeds irradiated with protons

    NASA Astrophysics Data System (ADS)

    Qin, H. L.; Xue, J. M.; Lai, J. N.; Wang, J. Y.; Zhang, W. M.; Miao, Q.; Yan, S.; Zhao, W. J.; He, F.; Gu, H. Y.; Wang, Y. G.

    2006-04-01

    In order to investigate the influence of ion energy on the germination and survival rates, water-imbibed Arabidopsis seeds were irradiated with protons in atmosphere. The ion fluence used in this experiment was in the range of 4 × 109-1 × 1014 ions/cm2. The ion energy is from 1.1 MeV to 6.5 MeV. According to the structure of the seed and TRIM simulation, the ions with the energy of 6.5 MeV can irradiate the shoot apical meristem directly whereas the ions with the energy of 1.1 MeV cannot. The results showed that both the germination and survival rates decrease while increasing the ion fluence, and the fluence-respond curve for each energy has different character. Besides the shoot apical meristem (SAM), which is generally considered as the main radiobiological target, the existence of a secondary target around SAM is proposed in this paper.

  2. Developmental anatomy of blueberry (Vaccinium corymbosum L. ‘Aurora’) shoot regeneration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The culture of Vaccinium corymbosum L. ’Aurora’ leaves on regeneration medium results in the regeneration of adventitious shoots. We present anatomical evidence that these new shoot apices are directly regenerated from the cultured blades. Mounds of densely staining cells, which formed from epidermi...

  3. Ribonuclease J is required for chloroplast and embryo development in Arabidopsis

    PubMed Central

    Chen, Hongyu; Zou, Wenxuan; Zhao, Jie

    2015-01-01

    Chloroplasts perform many essential metabolic functions and their proper development is critically important in embryogenesis. However, little is known about how chloroplasts function in embryogenesis and more relevant components need to be characterized. In this study, we show that Arabidopsis Ribonuclease J (RNase J) is required for chloroplast and embryo development. Mutation of AtRNJ led to albino ovules containing aborted embryos; the morphological development of rnj embryos was disturbed after the globular stage. Observation of ultrastructures indicated that these aborted embryos may result from impaired chloroplast development. Furthermore, by analyzing the molecular markers of cell fate decisions (STM, FIL, ML1, SCR, and WOX5) in rnj embryos, we found that this impairment of chloroplast development may lead to aberrant embryo patterning along the apical-basal axis, indicating that AtRNJ is important in initiating and maintaining the organization of shoot apical meristems (SAMs), cotyledons, and hypocotyls. Moreover, the transport and response of auxin in rnj embryos was found to be disrupted, suggesting that AtRNJ may be involved in auxin-mediated pathways during embryogenesis. Therefore, we speculate that RNJ plays a vital role in embryo morphogenesis and apical-basal pattern formation by regulating chloroplast development. PMID:25871650

  4. CLAVATA-WUSCHEL signaling in the shoot meristem.

    PubMed

    Somssich, Marc; Je, Byoung Il; Simon, Rüdiger; Jackson, David

    2016-09-15

    Shoot meristems are maintained by pluripotent stem cells that are controlled by CLAVATA-WUSCHEL feedback signaling. This pathway, which coordinates stem cell proliferation with differentiation, was first identified in Arabidopsis, but appears to be conserved in diverse higher plant species. In this Review, we highlight the commonalities and differences between CLAVATA-WUSCHEL pathways in different species, with an emphasis on Arabidopsis, maize, rice and tomato. We focus on stem cell control in shoot meristems, but also briefly discuss the role of these signaling components in root meristems. PMID:27624829

  5. Geminivirus C4 protein alters Arabidopsis development.

    PubMed

    Mills-Lujan, Katherine; Deom, Carl Michael

    2010-03-01

    The C4 protein of beet curly top virus [BCTV-B (US:Log:76)] induces hyperplasia in infected phloem tissue and tumorigenic growths in transgenic plants. The protein offers an excellent model for studying cell cycle control, cell differentiation, and plant development. To investigate the role of the C4 protein in plant development, transgenic Arabidopsis thaliana plants were generated in which the C4 transgene was expressed under the control of an inducible promoter. A detailed analysis of the developmental changes that occur in cotyledons and hypocotyls of seedlings expressing the C4 transgene showed extensive cell division in all tissues types examined, radically altered tissue layer organization, and the absence of a clearly defined vascular system. Induced seedlings failed to develop true leaves, lateral roots, and shoot and root apical meristems, as well as vascular tissue. Specialized epidermis structures, such as stomata and root hairs, were either absent or developmentally impaired in seedlings that expressed C4 protein. Exogenous application of brassinosteroid and abscisic acid weakly rescued the C4-induced phenotype, while induced seedlings were hypersensitive to gibberellic acid and kinetin. These results indicate that ectopic expression of the BCTV C4 protein in A. thaliana drastically alters plant development, possibly through the disruption of multiple hormonal pathways. PMID:20091067

  6. Cell Proliferation Analysis Using EdU Labeling in Whole Plant and Histological Samples of Arabidopsis.

    PubMed

    Kazda, Anita; Akimcheva, Svetlana; Watson, J Matthew; Riha, Karel

    2016-01-01

    The ability to analyze cell division in both spatial and temporal dimensions within an organism is a key requirement in developmental biology. Specialized cell types within individual organs, such as those within shoot and root apical meristems, have often been identified by differences in their rates of proliferation prior to the characterization of distinguishing molecular markers. Replication-dependent labeling of DNA is a widely used method for assaying cell proliferation. The earliest approaches used radioactive labeling with tritiated thymidine, which were later followed by immunodetection of bromodeoxyuridine (BrdU). A major advance in DNA labeling came with the use of 5-ethynyl-2'deoxyuridine (EdU) which has proven to have multiple advantages over BrdU. Here we describe the methodology for analyzing EdU labeling and retention in whole plants and histological sections of Arabidopsis. PMID:26659962

  7. Hop Shoot Proliferation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hop shoot proliferation disease has been described in Poland., and is associated with phytoplasma infection. Hop shoot proliferation occurs rarely and seems to be of little economic concern in most regions of hop production. Hop shoot proliferation is thought to be caused by aster yellows phytoplas...

  8. Gravity perception and gravitropic response of inflorescence stems in Arabidopsis thaliana

    NASA Astrophysics Data System (ADS)

    Fukaki, H.; Tasaka, M.

    1999-01-01

    Shoots of higher plants exhibit negative gravitropism. However, little is known about the site of gravity perception in shoots and the molecular mechanisms of shoot gravitropic responses. Our recent analysis using shoot gravitropism1(sgr1)/scarecrow(scr) and sgr7/short-root (shr) mutants in Arabidopsis thaliana indicated that the endodermis is essential for shoot gravitropism and strongly suggested that the endodermis functions as the gravity-sensing cell layer in dicotyledonous plant shoots. In this paper, we present our recent analysis and model of gravity perception and gravitropic response of inflorescence stems in Arabidopsis thaliana.

  9. Stress-induced somatic embryogenesis in vegetative tissues of Arabidopsis thaliana.

    PubMed

    Ikeda-Iwai, Miho; Umehara, Mikihisa; Satoh, Shinobu; Kamada, Hiroshi

    2003-04-01

    Somatic embryogenesis is an obvious experimental evidence of totipotency, and is used as a model system for studying the mechanisms of de-differentiation and re-differentiation of plant cells. Although Arabidopsis is widely used as a model plant for genetic and molecular biological studies, there is no available tissue culture system for inducing somatic embryogenesis from somatic cells in this plant. We established a new tissue culture system using stress treatment to induce somatic embryogenesis in Arabidopsis. In this system, stress treatment induced formation of somatic embryos from shoot-apical-tip and floral-bud explants. The somatic embryos grew into young plantlets with normal morphology, including cotyledons, hypocotyls, and roots, and some embryo-specific genes (ABI3 and FUS3) were expressed in these embryos. Several stresses (osmotic, heavy metal ion, and dehydration stress) induced somatic embryogenesis, but the optimum stress treatment differed between different stressors. When we used mannitol to cause osmotic stress, the optimal conditions for somatic embryogenesis were 6-9 h of culture on solid B5 medium containing 0.7 m mannitol, after which the explants were transferred to B5 medium containing 2,4-dichlorophenoxyacetic acid (2,4-D, 4.5 microm), but no mannitol. Using this tissue culture system, we induced somatic embryogenesis in three major ecotypes of Arabidopsis thaliana-Ws, Col, and Ler. PMID:12662313

  10. The impact of heat stress targeting on the hormonal and transcriptomic response in Arabidopsis.

    PubMed

    Dobrá, Jana; Černý, Martin; Štorchová, Helena; Dobrev, Petre; Skalák, Jan; Jedelský, Petr L; Lukšanová, Hana; Gaudinová, Alena; Pešek, Bedřich; Malbeck, Jiří; Vanek, Tomas; Brzobohatý, Břetislav; Vanková, Radomíra

    2015-02-01

    Targeting of the heat stress (HS, 40°C) to shoots, roots or whole plants substantially affects Arabidopsis physiological responses. Effective stress targeting was proved by determination of the expression of HS markers, HsfA2 and HSA32, which were quickly stimulated in the targeted organ(s), but remained low in non-stressed tissues for at least 2h. When shoots or whole plants were subjected to HS, a transient decrease in abscisic acid, accompanied by a small increase in active cytokinin levels, was observed in leaves, consistent with stimulation of transpiration, the main cooling mechanism in leaves. HS application targeted to part of plant resulted in a rapid stimulation of expression of components of cytokinin signaling pathway (especially of receptor genes) in the non-exposed tissues, which indicated fast inter-organ communication. Under all HS treatments, shoot apices responded by transient elevation of active cytokinin contents and stimulation of transcription of genes involved in photosynthesis and carbohydrate metabolism. Duration of this stimulation was negatively correlated with stress strength. The impact of targeted HS on the expression of 63 selected genes, including those coding regulatory 14-3-3 proteins, was compared. Stimulation of GRF9 (GRF14μ) in stressed organs after 2-6h may be associated with plant stress adaptation. PMID:25575991

  11. N-Myristoylation Regulates the SnRK1 Pathway in Arabidopsis[W

    PubMed Central

    Pierre, Michèle; Traverso, José A.; Boisson, Bertrand; Domenichini, Séverine; Bouchez, David; Giglione, Carmela; Meinnel, Thierry

    2007-01-01

    Cotranslational and posttranslational modifications are increasingly recognized as important in the regulation of numerous essential cellular functions. N-myristoylation is a lipid modification ensuring the proper function and intracellular trafficking of proteins involved in many signaling pathways. Arabidopsis thaliana, like human, has two tightly regulated N-myristoyltransferase (NMT) genes, NMT1 and NMT2. Characterization of knockout mutants showed that NMT1 was strictly required for plant viability, whereas NMT2 accelerated flowering. NMT1 impairment induced extremely severe defects in the shoot apical meristem during embryonic development, causing growth arrest after germination. A transgenic plant line with an inducible NMT1 gene demonstrated that NMT1 expression had further effects at later stages. NMT2 did not compensate for NMT1 in the nmt1-1 mutant, but NMT2 overexpression resulted in shoot and root meristem abnormalities. Various data from complementation experiments in the nmt1-1 background, using either yeast or human NMTs, demonstrated a functional link between the developmental arrest of nmt1-1 mutants and the myristoylation state of an extremely small set of protein targets. We show here that protein N-myristoylation is systematically associated with shoot meristem development and that SnRK1 (for SNF1-related kinase) is one of its essential primary targets. PMID:17827350

  12. Sugar demand, not auxin, is the initial regulator of apical dominance.

    PubMed

    Mason, Michael G; Ross, John J; Babst, Benjamin A; Wienclaw, Brittany N; Beveridge, Christine A

    2014-04-22

    For almost a century the plant hormone auxin has been central to theories on apical dominance, whereby the growing shoot tip suppresses the growth of the axillary buds below. According to the classic model, the auxin indole-3-acetic acid is produced in the shoot tip and transported down the stem, where it inhibits bud growth. We report here that the initiation of bud growth after shoot tip loss cannot be dependent on apical auxin supply because we observe bud release up to 24 h before changes in auxin content in the adjacent stem. After the loss of the shoot tip, sugars are rapidly redistributed over large distances and accumulate in axillary buds within a timeframe that correlates with bud release. Moreover, artificially increasing sucrose levels in plants represses the expression of BRANCHED1 (BRC1), the key transcriptional regulator responsible for maintaining bud dormancy, and results in rapid bud release. An enhancement in sugar supply is both necessary and sufficient for suppressed buds to be released from apical dominance. Our data support a theory of apical dominance whereby the shoot tip's strong demand for sugars inhibits axillary bud outgrowth by limiting the amount of sugar translocated to those buds. PMID:24711430

  13. Apical Functionalization of Tribenzotriquinacenes.

    PubMed

    Dhara, Ayan; Weinmann, Joshua; Krause, Ana-Maria; Beuerle, Florian

    2016-08-22

    The introduction of one alkyne moiety at the central carbon atom of the tripodal tribenzotriquinacene scaffold allows easy access to a great variety of apically functionalized derivatives. The spatially well-separated arrangement of different functional units on the convex face and outer rim was further proven by single-crystal X-ray studies. Subsequent modifications that feature a general protecting group-free strategy for the demethylation of protected catechols in the presence of a terminal alkyne group, an azide-alkyne Huisgen cycloaddition, and Sonogashira cross-coupling reactions showcase the high synthetic potential of this modular approach for tribenzotriquinacene derivatization. PMID:27444414

  14. The Arabidopsis GAMYB-Like Genes, MYB33 and MYB65, Are MicroRNA-Regulated Genes That Redundantly Facilitate Anther Development

    PubMed Central

    Millar, Anthony A.; Gubler, Frank

    2005-01-01

    The functions of the vast majority of genes encoding R2R3 MYB domain proteins remain unknown. The closely related MYB33 and MYB65 genes of Arabidopsis thaliana have high sequence similarity to the barley (Hordeum vulgare) GAMYB gene. T-DNA insertional mutants were isolated for both genes, and a myb33 myb65 double mutant was defective in anther development. In myb33 myb65 anthers, the tapetum undergoes hypertrophy at the pollen mother cell stage, resulting in premeiotic abortion of pollen development. However, myb33 myb65 sterility was conditional, where fertility increased both under higher light or lower temperature conditions. Thus, MYB33/MYB65 facilitate, but are not essential for, anther development. Neither single mutant displayed a phenotype, implying that MYB33 and MYB65 are functionally redundant. Consistent with functional redundancy, promoter–β-glucuronidase (GUS) fusions of MYB33 and MYB65 gave identical expression patterns in flowers (sepals, style, receptacle, anther filaments, and connective but not in anthers themselves), shoot apices, and root tips. By contrast, expression of a MYB33:GUS translational fusion in flowers was solely in young anthers (consistent with the male sterile phenotype), and no staining was seen in shoot meristems or root tips. A microRNA target sequence is present in the MYB genes, and mutating this sequence in the MYB33:GUS fusion results in an expanded expression pattern, in tissues similar to that observed in the promoter-GUS lines, implying that the microRNA target sequence is restricting MYB33 expression. Arabidopsis transformed with MYB33 containing the mutated microRNA target had dramatic pleiotrophic developmental defects, suggesting that restricting MYB33 expression, especially in the shoot apices, is essential for proper plant development. PMID:15722475

  15. Hormonal control of second flushing in Douglas-fir shoots.

    PubMed

    Cline, Morris; Yoders, Mark; Desai, Dipti; Harrington, Constance; Carlson, William

    2006-10-01

    Spring-flushing, over-wintered buds of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) produce new buds that may follow various developmental pathways. These include second flushing in early summer or dormancy before flushing during the following spring. Second flushing usually entails an initial release of apical dominance as some of the current-season upper lateral buds grow out. Four hypotheses concerning control of current bud outgrowth in spring-flushing shoots were tested: (1) apically derived auxin in the terminal spring-flushing shoot suppresses lateral bud outgrowth (second flushing); (2) cytokinin (0.5 mM benzyladenine) spray treatments given midway through the spring flush period induce bud formation; (3) similar cytokinin spray treatments induce the outgrowth of existing current lateral buds; and (4) defoliation of the terminal spring-flushing shoot promotes second flushing. Hypothesis 1 was supported by data demonstrating that decapitation-released apical dominance was completely restored by treatment with exogenous auxin (22.5 or 45 mM naphthalene acetic acid) (Thimann-Skoog test). Hypothesis 2 was marginally supported by a small, but significant increase in bud number; and Hypothesis 3 was strongly supported by a large increase in the number of outgrowing buds following cytokinin applications. Defoliation produced similar results to cytokinin application. We conclude that auxin and cytokinin play important repressive and promotive roles, respectively, in the control of second flushing in the terminal spring-flushing Douglas-fir shoot. PMID:16815839

  16. Repression of AS2 by WOX family transcription factors is required for leaf development in Medicago and Arabidopsis

    PubMed Central

    Zhang, Fei; Tadege, Million

    2015-01-01

    WOX transcription factors are key regulators of meristematic activity in plants. The Medicago WOX gene, STF, functions in maintenance of leaf marginal meristem, analogous to the function of WUS in the shoot apical meristem. Both STF and WUS directly repress AS2 expression in their respective domains. Ectopic expression of AS2 with WUS promoter leads to a narrow leaf phenotype and other phenotypes similar to the wus mutant. We also found that a wox1 prs wus triple mutant produces much narrower leaf blades than the wox1 prs double mutant, indicating that WUS genetically interacts with WOX1 and PRS in Arabidopsis leaf blade development. Our data points to a general requirement for AS2 repression in meristematic regions to allow cell proliferation. PMID:25807065

  17. Repression of AS2 by WOX family transcription factors is required for leaf development in Medicago and Arabidopsis.

    PubMed

    Zhang, Fei; Tadege, Million

    2015-01-01

    WOX transcription factors are key regulators of meristematic activity in plants. The Medicago WOX gene, STF, functions in maintenance of leaf marginal meristem, analogous to the function of WUS in the shoot apical meristem. Both STF and WUS directly repress AS2 expression in their respective domains. Ectopic expression of AS2 with WUS promoter leads to a narrow leaf phenotype and other phenotypes similar to the wus mutant. We also found that a wox1 prs wus triple mutant produces much narrower leaf blades than the wox1 prs double mutant, indicating that WUS genetically interacts with WOX1 and PRS in Arabidopsis leaf blade development. Our data points to a general requirement for AS2 repression in meristematic regions to allow cell proliferation. PMID:25807065

  18. Regulation of SHOOT MERISTEMLESS genes via an upstream-conserved noncoding sequence coordinates leaf development

    PubMed Central

    Uchida, Naoyuki; Townsley, Brad; Chung, Kook-Hyun; Sinha, Neelima

    2007-01-01

    The indeterminate shoot apical meristem of plants is characterized by the expression of the Class 1 KNOTTED1-LIKE HOMEOBOX (KNOX1) genes. KNOX1 genes have been implicated in the acquisition and/or maintenance of meristematic fate. One of the earliest indicators of a switch in fate from indeterminate meristem to determinate leaf primordium is the down-regulation of KNOX1 genes orthologous to SHOOT MERISTEMLESS (STM) in Arabidopsis (hereafter called STM genes) in the initiating primordia. In simple leafed plants, this down-regulation persists during leaf formation. In compound leafed plants, however, KNOX1 gene expression is reestablished later in the developing primordia, creating an indeterminate environment for leaflet formation. Despite this knowledge, most aspects of how STM gene expression is regulated remain largely unknown. Here, we identify two evolutionarily conserved noncoding sequences within the 5′ upstream region of STM genes in both simple and compound leafed species across monocots and dicots. We show that one of these elements is involved in the regulation of the persistent repression and/or the reestablishment of STM expression in the developing leaves but is not involved in the initial down-regulation in the initiating primordia. We also show evidence that this regulation is developmentally significant for leaf formation in the pathway involving ASYMMETRIC LEAVES1/2 (AS1/2) gene expression; these genes are known to function in leaf development. Together, these findings reveal a regulatory point of leaf development mediated through a conserved, noncoding sequence in STM genes. PMID:17898165

  19. Formation of polarity convergences underlying shoot outgrowths.

    PubMed

    Abley, Katie; Sauret-Güeto, Susanna; Marée, Athanasius Fm; Coen, Enrico

    2016-01-01

    The development of outgrowths from plant shoots depends on formation of epidermal sites of cell polarity convergence with high intracellular auxin at their centre. A parsimonious model for generation of convergence sites is that cell polarity for the auxin transporter PIN1 orients up auxin gradients, as this spontaneously generates convergent alignments. Here we test predictions of this and other models for the patterns of auxin biosynthesis and import. Live imaging of outgrowths from kanadi1 kanadi2 Arabidopsis mutant leaves shows that they arise by formation of PIN1 convergence sites within a proximodistal polarity field. PIN1 polarities are oriented away from regions of high auxin biosynthesis enzyme expression, and towards regions of high auxin importer expression. Both expression patterns are required for normal outgrowth emergence, and may form part of a common module underlying shoot outgrowths. These findings are more consistent with models that spontaneously generate tandem rather than convergent alignments. PMID:27478985

  20. Shoot dieback in pecan

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two shoot dieback maladies (SDM) of pecan [Carya illinoinensis (Wangenh.) C. Koch] are of unknown cause and can adversely affect canopy health. They occur during either early spring (SpSDM) or early summer (SuSDM). Field evaluation found that both maladies predominately occur on shoots retaining p...

  1. Water availability limits tolerance of apical damage in the Chilean tarweed Madia sativa

    NASA Astrophysics Data System (ADS)

    Gonzáles, Wilfredo L.; Suárez, Lorena H.; Molina-Montenegro, Marco A.; Gianoli, Ernesto

    2008-07-01

    Plant tolerance is the ability to reduce the negative impact of herbivory on plant fitness. Numerous studies have shown that plant tolerance is affected by nutrient availability, but the effect of soil moisture has received less attention. We evaluated tolerance of apical damage (clipping that mimicked insect damage) under two watering regimes (control watering and drought) in the tarweed Madia sativa (Asteraceae). We recorded number of heads with seeds and total number of heads as traits related to fitness. Net photosynthetic rate, water use efficiency, number of branches, shoot biomass, and the root:shoot biomass ratio were measured as traits potentially related to tolerance via compensatory responses to damage. In the drought treatment, damaged plants showed ≈43% reduction in reproductive fitness components in comparison with undamaged plants. In contrast, there was no significant difference in reproductive fitness between undamaged and damaged plants in the control watering treatment. Shoot biomass was not affected by apical damage. The number of branches increased after damage in both water treatments but this increase was limited by drought stress. Net photosynthetic rate increased in damaged plants only in the control watering treatment. Water use efficiency increased with drought stress and, in plants regularly watered, also increased after damage. Root:shoot ratio was higher in the low water treatment and damaged plants tended to reduce root:shoot ratio only in this water treatment. It is concluded that water availability limits tolerance to apical damage in M. sativa, and that putative compensatory mechanisms are differentially affected by water availability.

  2. Identification of the arabidopsis RAM/MOR signalling network: adding new regulatory players in plant stem cell maintenance and cell polarization

    PubMed Central

    Zermiani, Monica; Begheldo, Maura; Nonis, Alessandro; Palme, Klaus; Mizzi, Luca; Morandini, Piero; Nonis, Alberto; Ruperti, Benedetto

    2015-01-01

    Background and Aims The RAM/MOR signalling network of eukaryotes is a conserved regulatory module involved in co-ordination of stem cell maintenance, cell differentiation and polarity establishment. To date, no such signalling network has been identified in plants. Methods Genes encoding the bona fide core components of the RAM/MOR pathway were identified in Arabidopsis thaliana (arabidopsis) by sequence similarity searches conducted with the known components from other species. The transcriptional network(s) of the arabidopsis RAM/MOR signalling pathway were identified by running in-depth in silico analyses for genes co-regulated with the core components. In situ hybridization was used to confirm tissue-specific expression of selected RAM/MOR genes. Key Results Co-expression data suggested that the arabidopsis RAM/MOR pathway may include genes involved in floral transition, by co-operating with chromatin remodelling and mRNA processing/post-transcriptional gene silencing factors, and genes involved in the regulation of pollen tube polar growth. The RAM/MOR pathway may act upstream of the ROP1 machinery, affecting pollen tube polar growth, based on the co-expression of its components with ROP-GEFs. In silico tissue-specific co-expression data and in situ hybridization experiments suggest that different components of the arabidopsis RAM/MOR are expressed in the shoot apical meristem and inflorescence meristem and may be involved in the fine-tuning of stem cell maintenance and cell differentiation. Conclusions The arabidopsis RAM/MOR pathway may be part of the signalling cascade that converges in pollen tube polarized growth and in fine-tuning stem cell maintenance, differentiation and organ polarity. PMID:26078466

  3. Putative sugarcane FT/TFL1 genes delay flowering time and alter reproductive architecture in Arabidopsis

    PubMed Central

    Coelho, Carla P.; Minow, Mark A. A.; Chalfun-Júnior, Antonio; Colasanti, Joseph

    2014-01-01

    Agriculturally important grasses such as rice, maize, and sugarcane are evolutionarily distant from Arabidopsis, yet some components of the floral induction process are highly conserved. Flowering in sugarcane is an important factor that negatively affects cane yield and reduces sugar/ethanol production from this important perennial bioenergy crop. Comparative studies have facilitated the identification and characterization of putative orthologs of key flowering time genes in sugarcane, a complex polyploid plant whose genome has yet to be sequenced completely. Using this approach we identified phosphatidylethanolamine-binding protein (PEBP) gene family members in sugarcane that are similar to the archetypical FT and TFL1 genes of Arabidopsis that play an essential role in controlling the transition from vegetative to reproductive growth. Expression analysis of ScTFL1, which falls into the TFL1-clade of floral repressors, showed transcripts in developing leaves surrounding the shoot apex but not at the apex itself. ScFT1 was detected in immature leaves and apical regions of vegetatively growing plants and, after the floral transition, expression also occurred in mature leaves. Ectopic over-expression of ScTFL1 in Arabidopsis caused delayed flowering in Arabidopsis, as might be expected for a gene related to TFL1. In addition, lines with the latest flowering phenotype exhibited aerial rosette formation. Unexpectedly, over-expression of ScFT1, which has greatest similarity to the florigen-encoding FT, also caused a delay in flowering. This preliminary analysis of divergent sugarcane FT and TFL1 gene family members from Saccharum spp. suggests that their expression patterns and roles in the floral transition has diverged from the predicted role of similar PEBP family members. PMID:24904616

  4. Violence and school shootings.

    PubMed

    Flannery, Daniel J; Modzeleski, William; Kretschmar, Jeff M

    2013-01-01

    Multiple-homicide school shootings are rare events, but when they happen they significantly impact individuals, the school and the community. We focus on multiple-homicide incidents and identified mental health issues of shooters. To date, studies of school shootings have concluded that no reliable profile of a shooter exists, so risk should be assessed using comprehensive threat assessment protocols. Existing studies primarily utilize retrospective case histories or media accounts. The field requires more empirical and systematic research on all types of school shootings including single victim incidents, those that result in injury but not death and those that are successfully averted. We discuss current policies and practices related to school shootings and the role of mental health professionals in assessing risk and supporting surviving victims. PMID:23254623

  5. Strategy for shoot meristem proliferation in plants

    PubMed Central

    Fujita, Hironori; Kawaguchi, Masayoshi

    2011-01-01

    Shoot apical meristem (SAM) of plants harbors stem cells capable of generating the aerial tissues including reproductive organs. Therefore, it is very important for plants to control SAM proliferation and its density as a survival strategy. The SAM is regulated by the dynamics of a specific gene network, such as the WUS-CLV interaction of A. thaliana. By using a mathematical model, we previously proposed six possible SAM patterns in terms of the manner and frequency of stem cell proliferation. Two of these SAM patterns are predicted to generate either dichotomous or axillary shoot branch. Dichotomous shoot branches caused by this mechanism are characteristic of the earliest vascular plants, such as Cooksonia and Rhynia, but are observed in only a small minority of plant species of the present day. On the other hand, axillary branches are observed in the majority of plant species and are induced by a different dynamics of the feedback regulation between auxin and the asymmetric distribution of PIN auxin efflux carriers. During evolution, some plants may have adopted this auxin-PIN system to more strictly control SAM proliferation. PMID:22067107

  6. LEAFY COTYLEDON1 Is an Essential Regulator of Late Embryogenesis and Cotyledon Identity in Arabidopsis.

    PubMed Central

    West, MAL.; Yee, K. M.; Danao, J.; Zimmerman, J. L.; Fischer, R. L.; Goldberg, R. B.; Harada, J. J.

    1994-01-01

    LEAFY COTYLEDON1 (LEC1) is an embryo defective mutation that affects cotyledon identity in Arabidopsis. Mutant cotyledons possess trichomes that are normally a leaf trait in Arabidopsis, and the cellular organization of these organs is intermediate between that of cotyledons and leaves from wild-type plants. We present several lines of evidence that indicate that the control of late embryogenesis is compromised by the mutation. First, mutant embryos are desiccation intolerant, yet embryos can be rescued before they dry to yield homozygous recessive plants that produce defective embryos exclusively. Second, although many genes normally expressed during embryonic development are active in the mutant, at least one maturation phase-specific gene is not activated. Third, the shoot apical meristem is activated precociously in mutant embryos. Fourth, in mutant embryos, several genes characteristic of postgerminative development are expressed at levels typical of wild-type seedlings rather than embryos. We conclude that postgerminative development is initiated prematurely and that embryonic and postgerminative programs operate simultaneously in mutant embryos. The pleiotropic effects of the mutation indicate that the LEC1 gene plays a fundamental role in regulating late embryogenesis. The role of LEC1 and its relationship to other genes involved in controlling late embryonic development are discussed. PMID:12244233

  7. Meristem size contributes to the robustness of phyllotaxis in Arabidopsis

    PubMed Central

    Landrein, Benoit; Refahi, Yassin; Besnard, Fabrice; Hervieux, Nathan; Mirabet, Vincent; Boudaoud, Arezki; Vernoux, Teva; Hamant, Olivier

    2015-01-01

    Using the plant model Arabidopsis, the relationship between day length, the size of the shoot apical meristem, and the robustness of phyllotactic patterns were analysed. First, it was found that reducing day length leads to an increased meristem size and an increased number of alterations in the final positions of organs along the stem. Most of the phyllotactic defects could be related to an altered tempo of organ emergence, while not affecting the spatial positions of organ initiations at the meristem. A correlation was also found between meristem size and the robustness of phyllotaxis in two accessions (Col-0 and WS-4) and a mutant (clasp-1), independent of growth conditions. A reduced meristem size in clasp-1 was even associated with an increased robustness of the phyllotactic pattern, beyond what is observed in the wild type. Interestingly it was also possible to modulate the robustness of phyllotaxis in these different genotypes by changing day length. To conclude, it is shown first that robustness of the phyllotactic pattern is not maximal in the wild type, suggesting that, beyond its apparent stereotypical order, the robustness of phyllotaxis is regulated. Secondly, a role for day length in the robustness of the phyllotaxis was also identified, thus providing a new example of a link between patterning and environment in plants. Thirdly, the experimental results validate previous model predictions suggesting a contribution of meristem size in the robustness of phyllotaxis via the coupling between the temporal sequence and spatial pattern of organ initiations. PMID:25504644

  8. Superroot, a recessive mutation in Arabidopsis, confers auxin overproduction.

    PubMed Central

    Boerjan, W; Cervera, M T; Delarue, M; Beeckman, T; Dewitte, W; Bellini, C; Caboche, M; Van Onckelen, H; Van Montagu, M; Inzé, D

    1995-01-01

    We have isolated seven allelic recessive Arabidopsis mutants, designated superroot (sur1-1 to sur1-7), displaying several abnormalities reminiscent of auxin effects. These characteristics include small and epinastic cotyledons, an elongated hypocotyl in which the connection between the stele and cortical and epidermal cells disintegrates, the development of excess adventitious and lateral roots, a reduced number of leaves, and the absence of an inflorescence. When germinated in the dark, sur1 mutants did not develop the apical hook characteristic of etiolated seedlings. We were able to phenocopy the Sur1- phenotype by supplying auxin to wild-type seedlings, to propagate sur1 explants on phytohormone-deficient medium, and to regenerate shoots from these explants by the addition of cytokinins alone to the culture medium. Analysis by gas chromatography coupled to mass spectrometry indicated increased levels of both free and conjugated indole-3-acetic acid. sur1 was crossed to the mutant axr2 and the altered-auxin response mutant ctr1. The phenotype of both double mutants was additive. The sur1 gene was mapped on chromosome 2 at 0.5 centimorgans from the gene encoding phytochrome B. PMID:8589625

  9. Plastid DNA polymerases from higher plants, Arabidopsis thaliana

    SciTech Connect

    Mori, Yoko; Kimura, Seisuke; Saotome, Ai; Kasai, Nobuyuki; Sakaguchi, Norihiro; Uchiyama, Yukinobu; Ishibashi, Toyotaka; Yamamoto, Taichi; Chiku, Hiroyuki; Sakaguchi, Kengo . E-mail: kengo@rs.noda.sut.ac.jp

    2005-08-19

    Previously, we described a novel DNA polymerase, designated as OsPolI-like, from rice. The OsPolI-like showed a high degree of sequence homology with the DNA polymerase I of cyanobacteria and was localized in the plastid. Here, we describe two PolI-like polymerases, designated as AtPolI-like A and AtPolI-like B, from Arabidopsis thaliana. In situ hybridization analysis demonstrated expression of both mRNAs in proliferating tissues such as the shoot apical meristem. Analysis of the localizations of GFP fusion proteins showed that AtPolI-like A and AtPolI-like B were localized to plastids. AtPolI-like B expression could be induced by exposure to the mutagen H{sub 2}O{sub 2}. These results suggested that AtPolI-like B has a role in the repair of oxidation-induced DNA damage. Our data indicate that higher plants possess two plastid DNA polymerases that are not found in animals and yeasts.

  10. Oxidative metabolism involved in non-targeted effects induced by proton radiation in intact Arabidopsis seeds.

    PubMed

    Mei, Tao; Yang, Gen; Quan, Yi; Wang, Weikang; Zhang, Weiming; Xue, Jianming; Wu, Lijun; Gu, Hongya; Schettino, Giuseppe; Wang, Yugang

    2011-01-01

    Non-targeted effects induced by ionizing radiation have been demonstrated both in vitro and in vivo. Previously, we have also demonstrated the existence of non-targeted effects in intact Arabidopsis seeds following low-energy heavy-ion radiation. In the present study, 6.5 MeV protons with 8 × 10(11) ions/cm(2) and 2 × 10(11) ions/cm(2) fluence respectively were used to irradiate non-shielded or partial-shielded Arabidopsis seeds to further explore the mechanisms which regulate in vivo non-targeted effects and to investigate the difference between damage caused by non-targeted effects and direct irradiation. Results showed that excess reactive oxygen species (ROS) are present in the non-irradiated part of the partially irradiated samples, indicating that in vivo non-targeted effects can promote the generation of excess metabolic ROS in the non-irradiated shoot apical meristem/root apical meristem cells. Furthermore, pretreatment with 0.5% ROS scavenger dimethyl sulfoxide (DMSO) or 0.02 mM reactive nitrogen species (RNS) scavenger 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) significantly suppresses the non-targeted effects in the partially irradiated samples, while in the whole-body irradiated samples, the cPTIO pretreatment has no effect. On the other hand using antioxidant enzyme assays, superoxide dismutase activity was found to increase for partial irradiated samples and decrease for the whole-body exposed seeds. Taken together, these results implicate that damage caused by non-targeted effects is different from that induced by direct irradiation in vivo. Metabolic products such as ROS and RNS are involved in the in vivo non-targeted effects. PMID:21343677

  11. [Distribution and speciation of Pb in Arabidopsis thaliana shoot and rhizosphere soil by in situ synchrotron radiation micro X-ray fluorescence and X-ray absorption near edge structure].

    PubMed

    Shen, Ya-Ting

    2014-03-01

    In order to investigate plant reacting mechanism with heavy metal stress in organ and tissue level, synchrotron radiation micro X-ray fluorescence (micro-SRXRF) was used to determine element distribution characteristics of K, Ca, Mn, Fe, Cu, Zn, Pb in an Arabidopsis thaliana seedling grown in tailing dam soil taken from a lead-zinc mine exploration area. The results showed a regular distribution characters of K, Ca, Fe, Cu and Zn, while Pb appeared not only in root, but also in a leaf bud which was beyond previously understanding that Pb mainly appeared in plant root. Pb competed with Mn in the distribution of the whole seedling. Pb may cause the increase of oxidative stress in root and leaf bud, and restrict Mn absorption and utilization which explained the phenomenon of seedling death in this tailing damp soil. Speciation of Pb in Arabidopsis thaliana and tailing damp rhizosphere soil were also presented after using PbL3 micro X-ray absorption near edge structure (micro-XANES). By comparison of PbL3 XANES peak shape and peak position between standard samples and rhizosphere soil sample, it was demonstrated that the tailing damp soil was mainly formed by amorphous forms like PbO (64.2%), Pb (OH)2 (28.8%) and Pb3O4 (6.3%) rather than mineral or organic Pb speciations. The low plant bioavailability of Pb demonstrated a further research focusing on Pb absorption and speciation conversion is needed, especially the role of dissolve organic matter in soil which may enhance Pb bioavailability. PMID:25208420

  12. TYPE-ONE PROTEIN PHOSPHATASE4 Regulates Pavement Cell Interdigitation by Modulating PIN-FORMED1 Polarity and Trafficking in Arabidopsis1

    PubMed Central

    Guo, Xiaola; Qin, Qianqian; Yan, Jia; Niu, Yali; Huang, Bingyao; Guan, Liping; Li, Yuan; Ren, Dongtao; Li, Jia; Hou, Suiwen

    2015-01-01

    In plants, cell morphogenesis is dependent on intercellular auxin accumulation. The polar subcellular localization of the PIN-FORMED (PIN) protein is crucial for this process. Previous studies have shown that the protein kinase PINOID (PID) and protein phosphatase6-type phosphatase holoenzyme regulate the phosphorylation status of PIN1 in root tips and shoot apices. Here, we show that a type-one protein phosphatase, TOPP4, is essential for the formation of interdigitated pavement cell (PC) pattern in Arabidopsis (Arabidopsis thaliana) leaf. The dominant-negative mutant topp4-1 showed severely inhibited interdigitated PC growth. Expression of topp4-1 gene in wild-type plants recapitulated the PC defects in the mutant. Genetic analyses suggested that TOPP4 and PIN1 likely function in the same pathway to regulate PC morphogenesis. Furthermore, colocalization, in vitro and in vivo protein interaction studies, and dephosphorylation assays revealed that TOPP4 mediated PIN1 polar localization and endocytic trafficking in PCs by acting antagonistically with PID to modulate the phosphorylation status of PIN1. In addition, TOPP4 affects the cytoskeleton pattern through the Rho of Plant GTPase-dependent auxin-signaling pathway. Therefore, we conclude that TOPP4-regulated PIN1 polar targeting through direct dephosphorylation is crucial for PC morphogenesis in the Arabidopsis leaf. PMID:25560878

  13. Cellular localization of the Ca2+ binding TCH3 protein of Arabidopsis

    NASA Technical Reports Server (NTRS)

    Antosiewicz, D. M.; Polisensky, D. H.; Braam, J.

    1995-01-01

    TCH3 is an Arabidopsis touch (TCH) gene isolated as a result of its strong and rapid upregulation in response to mechanical stimuli, such as touch and wind. TCH3 encodes an unusual calcium ion-binding protein that is closely related to calmodulin but has the potential to bind six calcium ions. Here it is shown that TCH3 shows a restricted pattern of accumulation during Arabidopsis vegetative development. These data provide insight into the endogenous signals that may regulate TCH3 expression and the sites of TCH3 action. TCH3 is abundant in the shoot apical meristem, vascular tissue, the root columella and pericycle cells that give rise to lateral roots. In addition, TCH3 accumulation in cells of developing shoots and roots closely correlates with the process of cellular expansion. Following wind stimulation, TCH3 becomes more abundant in specific regions including the branchpoints of leaf primordia and stipules, pith parenchyma, and the vascular tissue. The consequences of TCH3 upregulation by wind are therefore spatially restricted and TCH3 may function at these sites to modify cell or tissue characteristics following mechanical stimulation. Because TCH3 accumulates specifically in cells and tissues that are thought to be under the influence of auxin, auxin levels may regulate TCH3 expression during development. TCH3 is upregulated in response to low levels of exogenous indole-3-acetic acid (IAA), but not by inactive auxin-related compounds. These results suggest that TCH3 protein may play roles in mediating physiological responses to auxin and mechanical environmental stimuli.

  14. Warm spring temperatures induce persistent season-long changes in shoot development in grapevines

    PubMed Central

    Keller, Markus; Tarara, Julie M.

    2010-01-01

    Background and Aims The influence of temperature on the timing of budbreak in woody perennials is well known, but its effect on subsequent shoot growth and architecture has received little attention because it is understood that growth is determined by current temperature. Seasonal shoot development of grapevines (Vitis vinifera) was evaluated following differences in temperature near budbreak while minimizing the effects of other microclimatic variables. Methods Dormant buds and emerging shoots of field-grown grapevines were heated above or cooled below the temperature of ambient buds from before budbreak until individual flowers were visible on inflorescences, at which stage the shoots had four to eight unfolded leaves. Multiple treatments were imposed randomly on individual plants and replicated across plants. Shoot growth and development were monitored during two growing seasons. Key Results Higher bud temperatures advanced the date of budbreak and accelerated shoot growth and leaf area development. Differences were due to higher rates of shoot elongation, leaf appearance, leaf-area expansion and axillary-bud outgrowth. Although shoots arising from heated buds grew most vigorously, apical dominance in these shoots was reduced, as their axillary buds broke earlier and gave rise to more vigorous lateral shoots. In contrast, axillary-bud outgrowth was minimal on the slow-growing shoots emerging from buds cooled below ambient. Variation in shoot development persisted or increased during the growing season, well after temperature treatments were terminated and despite an imposed soil water deficit. Conclusions The data indicate that bud-level differences in budbreak temperature may lead to marked differences in shoot growth, shoot architecture and leaf-area development that are maintained or amplified during the growing season. Although growth rates commonly are understood to reflect current temperatures, these results demonstrate a persistent effect of early

  15. Expression of almond KNOTTED1 homologue (PdKn1) anticipates adventitious shoot initiation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background and Aims: The transcription factor encoded by the gene Knotted1 is a nuclear homeodomain protein, regulating meristematic cells at the shoot apical meristem. It has been proven that Knotted1 (KN1) has a role in the switch from an indeterminate to determinate cell fate and as such this gen...

  16. Mechanism of shoot gravitropism

    NASA Technical Reports Server (NTRS)

    Rayle, D. L.

    1984-01-01

    A better understanding of the cellular basis of plant shoot gravitropism was sought. A critical evaluation of the role of auxin gravitropism was provided. An alternative hypothesis which links Ca(42) fluxes to the asymmetric growth that leads to gravicurvature was evaluated.

  17. School Shootings Stun Reservation

    ERIC Educational Resources Information Center

    Borja, Rhea R.; Cavanagh, Sean

    2005-01-01

    This article deals with the impact brought by the school shootings at Red Lake Indian Reservation in Minnesota to the school community. A deeply troubled 16-year-old student shot and killed seven other people and himself at a high school. The nation's deadliest school attack since the 1999 slayings at Colorado's suburban Columbine High School took…

  18. Point and Shoot Astronomy

    NASA Astrophysics Data System (ADS)

    Hoot, John E.

    2011-05-01

    A new generation of point and shoot digital cameras, when combined with open source firmware enhancements can operate as astrographs. This paper explores the research and astro-photographic opportunities and capabilities offered by this pairing of mass production optics and open source functional extensions that retail for as little as $200.

  19. Roles of arabinogalactan proteins in cotyledon formation and cell wall deposition during embryo development of Arabidopsis.

    PubMed

    Zhong, Jing; Ren, YuJun; Yu, Miao; Ma, TengFei; Zhang, XueLian; Zhao, Jie

    2011-07-01

    Arabinogalactan proteins (AGPs) are a class of highly glycosylated, widely distributed proteins in higher plants. In the previous study, we found that the green fluorescence from JIM13-labeled AGPs was mainly distributed in embryo proper and the basal part of suspensor but gradually disappeared after the torpedo-stage embryos in Arabidopsis. And (β-D-Glc)(3) Yariv phenylglycoside (βGlcY), a synthetic reagent that specifically binds to AGPs, could inhibit embryo development. In this study, as a continuous work, we investigated the AGP functions in embryo germination, cotyledon formation, and cell wall deposition in Arabidopsis embryos by using immunofluorescent, immunoenzyme, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) techniques. The results showed that 50 μM βGlcY caused inhibition of embryo germination, formation of abnormal cotyledon embryos, and disorder of cotyledon vasculature. Compared with the normal embryos in vitro and in vivo, the AGPs and pectin signals were quite weaker in the whole abnormal embryos, whereas the cellulose signal was stronger in the shoot apical meristem (SAM) of abnormal embryo by calcofluor white staining. The FTIR assay demonstrated that the cell wall of abnormal embryos was relatively poorer in pectins and richer in cellulose than those of normal embryos. By TEM observation, the SAM cells of the abnormal embryos had less cytoplasm, more plastid and starch grains, and larger vacuole than that of normal embryos. These results indicated that AGPs may play roles in embryo germination, cotyledon formation, cell wall cellulose and pectin deposition, and cell division potentiality during embryo development of Arabidopsis. PMID:20830495

  20. The Binomial Distribution in Shooting

    ERIC Educational Resources Information Center

    Chalikias, Miltiadis S.

    2009-01-01

    The binomial distribution is used to predict the winner of the 49th International Shooting Sport Federation World Championship in double trap shooting held in 2006 in Zagreb, Croatia. The outcome of the competition was definitely unexpected.

  1. Key Proliferative Activity in the Junction between the Leaf Blade and Leaf Petiole of Arabidopsis1[W][OA

    PubMed Central

    Ichihashi, Yasunori; Kawade, Kensuke; Usami, Takeshi; Horiguchi, Gorou; Takahashi, Taku; Tsukaya, Hirokazu

    2011-01-01

    Leaves are the most important, fundamental units of organogenesis in plants. Although the basic form of a leaf is clearly divided into the leaf blade and leaf petiole, no study has yet revealed how these are differentiated from a leaf primordium. We analyzed the spatiotemporal pattern of mitotic activity in leaf primordia of Arabidopsis (Arabidopsis thaliana) in detail using molecular markers in combination with clonal analysis. We found that the proliferative zone is established after a short interval following the occurrence of a rod-shaped early leaf primordium; it is separated spatially from the shoot apical meristem and seen at the junction region between the leaf blade and leaf petiole and produces both leaf-blade and leaf-petiole cells. This proliferative region in leaf primordia is marked by activity of the ANGUSTIFOLIA3 (AN3) promoter as a whole and seems to be differentiated into several spatial compartments: activities of the CYCLIN D4;2 promoter and SPATULA enhancer mark parts of it specifically. Detailed analyses of the an3 and blade-on-petiole mutations further support the idea that organogenesis of the leaf blade and leaf petiole is critically dependent on the correct spatial regulation of the proliferative region of leaf primordia. Thus, the proliferative zone of leaf primordia is spatially differentiated and supplies both the leaf-blade and leaf-petiole cells. PMID:21880932

  2. Analysis of the Competence to Respond to KNOTTED1 Activity in Arabidopsis Leaves Using a Steroid Induction System1

    PubMed Central

    Hay, Angela; Jackson, David; Ori, Naomi; Hake, Sarah

    2003-01-01

    Expression of KNOX (KNOTTED1-like homeobox) genes in the shoot apical meristem of Arabidopsis is required for maintenance of a functional meristem, whereas exclusion of KNOX gene expression from leaf primordia is required for the elaboration of normal leaf morphology. We have constructed a steroid-inducible system to regulate both the amount and timing of KN1 (KNOTTED1) misexpression in Arabidopsis leaves. We demonstrate that lobed leaf morphology is produced in a dose-dependent manner, indicating that the amount of KN1 quantitatively affects the severity of lobing. The KN1-glucocorticoid receptor fusion protein is not detected in leaves in the absence of steroid induction, suggesting that it is only stable when associated with steroid in an active state. By using a second inducible fusion protein to mark exposure of leaf primordia to the steroid, we determined the stage of leaf development that produces lobed leaves in response to KN1. Primordia as old as plastochron 7 and as young as plastochron 2 were competent to respond to KN1. PMID:12692326

  3. The Control of Arabidopsis thaliana Growth by Cell Proliferation and Endoreplication Requires the F-Box Protein FBL17[OPEN

    PubMed Central

    Marrocco, Katia; Masoud, Kinda; Thomann, Alexis; Gusti, Andi; Bitrian, Marta; Schnittger, Arp; Genschik, Pascal

    2015-01-01

    A key step of the cell cycle is the entry into the DNA replication phase that typically commits cells to divide. However, little is known about the molecular mechanisms regulating this transition in plants. Here, we investigated the function of FBL17 (F BOX-LIKE17), an Arabidopsis thaliana F-box protein previously shown to govern the progression through the second mitosis during pollen development. Our work reveals that FBL17 function is not restricted to gametogenesis. FBL17 transcripts accumulate in both proliferating and postmitotic cell types of Arabidopsis plants. Loss of FBL17 function drastically reduces plant growth by altering cell division activity in both shoot and root apical meristems. In fbl17 mutant plants, DNA replication is severely impaired and endoreplication is fully suppressed. At the molecular level, lack of FBL17 increases the stability of the CDK (CYCLIN-DEPENDENT KINASE) inhibitor KIP-RELATED PROTEIN2 known to switch off CDKA;1 kinase activity. Despite the strong inhibition of cell proliferation in fbl17, some cells are still able to enter S phase and eventually to divide, but they exhibit a strong DNA damage response and often missegregate chromosomes. Altogether, these data indicate that the F-box protein FBL17 acts as a master cell cycle regulator during the diploid sporophyte phase of the plant. PMID:25944099

  4. Synergistic action of histone acetyltransferase GCN5 and receptor CLAVATA1 negatively affects ethylene responses in Arabidopsis thaliana.

    PubMed

    Poulios, Stylianos; Vlachonasios, Konstantinos E

    2016-02-01

    GENERAL CONTROL NON-REPRESSIBLE 5 (GCN5) is a histone acetyltransferase (HAT) and the catalytic subunit of several multicomponent HAT complexes that acetylate lysine residues of histone H3. Mutants in AtGCN5 display pleiotropic developmental defects including aberrant meristem function. Shoot apical meristem (SAM) maintenance is regulated by CLAVATA1 (CLV1), a receptor kinase that controls the size of the shoot and floral meristems. Upon activation through CLV3 binding, CLV1 signals to the transcription factor WUSCHEL (WUS), restricting WUS expression and thus the meristem size. We hypothesized that GCN5 and CLV1 act together to affect SAM function. Using genetic and molecular approaches, we generated and characterized clv gcn5 mutants. Surprisingly, the clv1-1 gcn5-1 double mutant exhibited constitutive ethylene responses, suggesting that GCN5 and CLV signaling act synergistically to inhibit ethylene responses in Arabidopsis. This genetic and molecular interaction was mediated by ETHYLENE INSENSITIVE 3/ EIN3-LIKE1 (EIN3/EIL1) transcription factors. Our data suggest that signals from the CLV transduction pathway reach the GCN5-containing complexes in the nucleus and alter the histone acetylation status of ethylene-responsive genes, thus translating the CLV information to transcriptional activity and uncovering a link between histone acetylation and SAM maintenance in the complex mode of ethylene signaling. PMID:26596766

  5. Shooting Star Experiment

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Shooting Star Experiment (SSE) is designed to develop and demonstrate the technology required to focus the sun's energy and use the energy for inexpensive space Propulsion Research. Pictured is an engineering model (Pathfinder III) of the Shooting Star Experiment (SSE). This model was used to test and characterize the motion and deformation of the structure caused by thermal effects. In this photograph, alignment targets are being placed on the engineering model so that a theodolite (alignment telescope) could be used to accurately measure the deformation and deflections of the engineering model under extreme conditions, such as the coldness of deep space and the hotness of the sun as well as vacuum. This thermal vacuum test was performed at the X-Ray Calibration Facility because of the size of the test article and the capabilities of the facility to simulate in-orbit conditions

  6. Ship and Shoot

    NASA Technical Reports Server (NTRS)

    Woods, Ron

    2012-01-01

    Ron Woods shared incredibly valuable insights gained during his 28 years at the Kennedy Space Center (KSC) packaging Flight Crew Equipment for shuttle and ISS missions. In particular, Woods shared anecdotes and photos from various processing events. The moral of these stories and the main focus of this discussion were the additional processing efforts and effects related to a "ship-and-shoot" philosophy toward flight hardware.

  7. WAG2 represses apical hook opening downstream from gibberellin and PHYTOCHROME INTERACTING FACTOR 5.

    PubMed

    Willige, Björn C; Ogiso-Tanaka, Eri; Zourelidou, Melina; Schwechheimer, Claus

    2012-11-01

    When penetrating the soil during germination, dicotyledonous plants protect their shoot apical meristem through the formation of an apical hook. Apical hook formation is a dynamic process that can be subdivided into hook formation, maintenance and opening. It has previously been established that these processes require the transport and signaling of the phytohormone auxin, as well as the biosynthesis and signaling of the phytohormones ethylene and gibberellin (GA). Here, we identify a molecular mechanism for an auxin-GA crosstalk by demonstrating that the auxin transport-regulatory protein kinase WAG2 is a crucial transcription target during apical hook opening downstream from GA signaling. We further show that WAG2 is directly activated by PHYTOCHROME INTERACTING FACTOR 5 (PIF5), a light-labile interactor of the DELLA repressors of the GA pathway. We find that wag2 mutants are impaired in the repression of apical hook opening in dark-grown seedlings and that this phenotype correlates with GA-regulated WAG2 expression in the concave (inner) side of the apical hook. Furthermore, wag2 mutants are also impaired in the maintenance or formation of a local auxin maximum at the site of WAG2 expression in the hook. WAG2 is a regulator of PIN auxin efflux facilitators and, in line with previous data, we show that this kinase can phosphorylate the central intracellular loop of all PIN-FORMED (PIN) proteins regulating apical hook opening. We therefore propose that apical hook opening is controlled by the differential GA-regulated accumulation of WAG2 and subsequent local changes in PIN-mediated auxin transport. PMID:22992959

  8. An Intrinsic MicroRNA Timer Regulates Progressive Decline in Shoot Regenerative Capacity in Plants

    PubMed Central

    Zhang, Tian-Qi; Lian, Heng; Tang, Hongbo; Dolezal, Karel; Zhou, Chuan-Miao; Yu, Sha; Chen, Juan-Hua; Chen, Qi; Liu, Hongtao; Ljung, Karin

    2015-01-01

    Plant cells are totipotent and competent to regenerate from differentiated organs. It has been shown that two phytohormones, auxin and cytokinin, play critical roles within this process. As in animals, the regenerative capacity declines with age in plants, but the molecular basis for this phenomenon remains elusive. Here, we demonstrate that an age-regulated microRNA, miR156, regulates shoot regenerative capacity. As a plant ages, the gradual increase in miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors leads to the progressive decline in shoot regenerative capacity. In old plants, SPL reduces shoot regenerative capacity by attenuating the cytokinin response through binding with the B-type ARABIDOPSIS RESPONSE REGULATORs, which encode the transcriptional activators in the cytokinin signaling pathway. Consistently, the increased amount of exogenous cytokinin complements the reduced shoot regenerative capacity in old plants. Therefore, the recruitment of age cues in response to cytokinin contributes to shoot regenerative competence. PMID:25649435

  9. Plasma Membrane-Targeted PIN Proteins Drive Shoot Development in a Moss

    PubMed Central

    Bennett, Tom A.; Liu, Maureen M.; Aoyama, Tsuyoshi; Bierfreund, Nicole M.; Braun, Marion; Coudert, Yoan; Dennis, Ross J.; O’Connor, Devin; Wang, Xiao Y.; White, Chris D.; Decker, Eva L.; Reski, Ralf; Harrison, C. Jill

    2014-01-01

    Summary Background Plant body plans arise by the activity of meristematic growing tips during development and radiated independently in the gametophyte (n) and sporophyte (2n) stages of the life cycle during evolution. Although auxin and its intercellular transport by PIN family efflux carriers are primary regulators of sporophytic shoot development in flowering plants, the extent of conservation in PIN function within the land plants and the mechanisms regulating bryophyte gametophytic shoot development are largely unknown. Results We have found that treating gametophytic shoots of the moss Physcomitrella patens with exogenous auxins and auxin transport inhibitors disrupts apical function and leaf development. Two plasma membrane-targeted PIN proteins are expressed in leafy shoots, and pin mutants resemble plants treated with auxins or auxin transport inhibitors. PIN-mediated auxin transport regulates apical cell function, leaf initiation, leaf shape, and shoot tropisms in moss gametophytes. pin mutant sporophytes are sometimes branched, reproducing a phenotype only previously seen in the fossil record and in rare natural moss variants. Conclusions Our results show that PIN-mediated auxin transport is an ancient, conserved regulator of shoot development. PMID:25448003

  10. The Arabidopsis-related halophyte Thellungiella halophila: boron tolerance via boron complexation with metabolites?

    PubMed

    Lamdan, Netta Li; Attia, Ziv; Moran, Nava; Moshelion, Menachem

    2012-04-01

    Tolerance to boron (B) is still not completely understood. We tested here the hypothesis that Thellungiella halophila, an Arabidopsis thaliana-related 'extremophile' plant, with abundance of B in its natural environment, is tolerant to B, and examined the potential mechanisms of this tolerance. With 1-10 mm B applied ([B](ext)) to Thellungiella and Arabidopsis grown in hydroponics, the steady-state accumulated B concentration ([B](int)) in the root was below [B](ext), and was similar in both, suggesting both extrude B actively. Whether grown in soil or hydroponically, the shoot [B](int) was higher in Arabidopsis than in Thellungiella, suggesting more effective net B exclusion by Thellungiella root. Arabidopsis exhibited toxicity symptoms including reduced shoot fresh weight (FW), but Thellungiella was not affected, even at similar levels of shoot-accumulated [B](int) (about 10 to 40 mm B in 'shoot water'), suggesting additional B tolerance mechanism in Thellungiella shoot. At [B](ext) = 5 mm, the summed shoot concentration of the potentially B-binding polyhydroxyl metabolites (malic acid, fructose, glucose, sucrose and citric acid) in Arabidopsis was below [B](int) , but in Thellungiella it was over twofold higher than [B](int) , and therefore likely to allow appreciable 1:2 boron-metabolite complexation in the shoot. This, we suggest, is an important component of Thellungiella B tolerance mechanism. PMID:21999349

  11. Formation of polarity convergences underlying shoot outgrowths

    PubMed Central

    Abley, Katie; Sauret-Güeto, Susanna; Marée, Athanasius FM; Coen, Enrico

    2016-01-01

    The development of outgrowths from plant shoots depends on formation of epidermal sites of cell polarity convergence with high intracellular auxin at their centre. A parsimonious model for generation of convergence sites is that cell polarity for the auxin transporter PIN1 orients up auxin gradients, as this spontaneously generates convergent alignments. Here we test predictions of this and other models for the patterns of auxin biosynthesis and import. Live imaging of outgrowths from kanadi1 kanadi2 Arabidopsis mutant leaves shows that they arise by formation of PIN1 convergence sites within a proximodistal polarity field. PIN1 polarities are oriented away from regions of high auxin biosynthesis enzyme expression, and towards regions of high auxin importer expression. Both expression patterns are required for normal outgrowth emergence, and may form part of a common module underlying shoot outgrowths. These findings are more consistent with models that spontaneously generate tandem rather than convergent alignments. DOI: http://dx.doi.org/10.7554/eLife.18165.001 PMID:27478985

  12. Roles for auxin, cytokinin, and strigolactone in regulating shoot branching.

    PubMed

    Ferguson, Brett J; Beveridge, Christine A

    2009-04-01

    Many processes have been described in the control of shoot branching. Apical dominance is defined as the control exerted by the shoot tip on the outgrowth of axillary buds, whereas correlative inhibition includes the suppression of growth by other growing buds or shoots. The level, signaling, and/or flow of the plant hormone auxin in stems and buds is thought to be involved in these processes. In addition, RAMOSUS (RMS) branching genes in pea (Pisum sativum) control the synthesis and perception of a long-distance inhibitory branching signal produced in the stem and roots, a strigolactone or product. Auxin treatment affects the expression of RMS genes, but it is unclear whether the RMS network can regulate branching independently of auxin. Here, we explore whether apical dominance and correlative inhibition show independent or additive effects in rms mutant plants. Bud outgrowth and branch lengths are enhanced in decapitated and stem-girdled rms mutants compared with intact control plants. This may relate to an RMS-independent induction of axillary bud outgrowth by these treatments. Correlative inhibition was also apparent in rms mutant plants, again indicating an RMS-independent component. Treatments giving reductions in RMS1 and RMS5 gene expression, auxin transport, and auxin level in the main stem were not always sufficient to promote bud outgrowth. We suggest that this may relate to a failure to induce the expression of cytokinin biosynthesis genes, which always correlated with bud outgrowth in our treatments. We present a new model that accounts for apical dominance, correlative inhibition, RMS gene action, and auxin and cytokinin and their interactions in controlling the progression of buds through different control points from dormancy to sustained growth. PMID:19218361

  13. Inactivation of plasma membrane-localized CDPK-RELATED KINASE5 decelerates PIN2 exocytosis and root gravitropic response in Arabidopsis.

    PubMed

    Rigó, Gábor; Ayaydin, Ferhan; Tietz, Olaf; Zsigmond, Laura; Kovács, Hajnalka; Páy, Anikó; Salchert, Klaus; Darula, Zsuzsanna; Medzihradszky, Katalin F; Szabados, László; Palme, Klaus; Koncz, Csaba; Cséplo, Agnes

    2013-05-01

    CRK5 is a member of the Arabidopsis thaliana Ca(2+)/calmodulin-dependent kinase-related kinase family. Here, we show that inactivation of CRK5 inhibits primary root elongation and delays gravitropic bending of shoots and roots. Reduced activity of the auxin-induced DR5-green fluorescent protein reporter suggests that auxin is depleted from crk5 root tips. However, no tip collapse is observed and the transcription of genes for auxin biosynthesis, AUXIN TRANSPORTER/AUXIN TRANSPORTER-LIKE PROTEIN (AUX/LAX) auxin influx, and PIN-FORMED (PIN) efflux carriers is unaffected by the crk5 mutation. Whereas AUX1, PIN1, PIN3, PIN4, and PIN7 display normal localization, PIN2 is depleted from apical membranes of epidermal cells and shows basal to apical relocalization in the cortex of the crk5 root transition zone. This, together with an increase in the number of crk5 lateral root primordia, suggests facilitated auxin efflux through the cortex toward the elongation zone. CRK5 is a plasma membrane-associated kinase that forms U-shaped patterns facing outer lateral walls of epidermis and cortex cells. Brefeldin inhibition of exocytosis stimulates CRK5 internalization into brefeldin bodies. CRK5 phosphorylates the hydrophilic loop of PIN2 in vitro, and PIN2 shows accelerated accumulation in brefeldin bodies in the crk5 mutant. Delayed gravitropic response of the crk5 mutant thus likely reflects defective phosphorylation of PIN2 and deceleration of its brefeldin-sensitive membrane recycling. PMID:23673979

  14. Developmental anatomy of the reproductive shoot in Hydrobryum japonicum (Podostemaceae).

    PubMed

    Katayama, Natsu; Koi, Satoshi; Kato, Masahiro

    2008-07-01

    Podostemaceae are unusual aquatic angiosperms adapting to extreme habitats, i.e., rapids and waterfalls, and have unique morphologies. We investigated the developmental anatomy of reproductive shoots scattered on crustose roots of Hydrobryum japonicum by scanning electron microscopy and using semi-thin serial sections. Two developmental patterns were observed: bracts arise either continuously from an area of meristematic cells that has produced leaves, or within differentiated root ground tissue beneath, and internal to, leaf base scars after an interruption. In both patterns, the bract primordia arise endogenously at the base of youngest bracts in the absence of shoot apical meristem, involving vacuolated-cell detachment to each bract separately. The different transition patterns of reproductive shoot development may be caused by different stages of parental vegetative shoots. The floral meristem arises between the two youngest bracts, and is similarly accompanied by cell degeneration. In contrast, the floral organs, including the spathella, arise exogenously from the meristem. Bract development, like vegetative leaf development, is unique to this podostemad, while floral-organ development is conserved. PMID:18506393

  15. Radiocesium Distribution in Bamboo Shoots after the Fukushima Nuclear Accident

    PubMed Central

    Higaki, Takumi; Higaki, Shogo; Hirota, Masahiro; Hasezawa, Seiichiro

    2014-01-01

    The distribution of radiocesium was examined in bamboo shoots, Phyllostachys pubescens, collected from 10 sites located some 41 to 1140 km from the Fukushima Daiichi nuclear power plant, Japan, in the Spring of 2012, 1 year after the Fukushima nuclear accident. Maximum activity concentrations for radiocesium 134Cs and 137Cs in the edible bamboo shoot parts, 41 km away from the Fukushima Daiichi plant, were in excess of 15.3 and 21.8 kBq/kg (dry weight basis; 1.34 and 1.92 kBq/kg, fresh weight), respectively. In the radiocesium-contaminated samples, the radiocesium activities were higher in the inner tip parts, including the upper edible parts and the apical culm sheath, than in the hardened culm sheath and underground basal parts. The radiocesium/potassium ratios also tended to be higher in the inner tip parts. The radiocesium activities increased with bamboo shoot length in another bamboo species, Phyllostachys bambusoides, suggesting that radiocesium accumulated in the inner tip parts during growth of the shoots. PMID:24831096

  16. Gain-of-function analysis of poplar CLE genes in Arabidopsis by exogenous application and over-expression assays.

    PubMed

    Liu, Yisen; Yang, Shaohui; Song, Yingjin; Men, Shuzhen; Wang, Jiehua

    2016-04-01

    Among 50CLEgene family members in thePopulus trichocarpagenome, three and sixPtCLEgenes encode a CLE motif sequence highly homologous toArabidopsisCLV3 and TDIF peptides, respectively, which potentially make them functional equivalents. To test and compare their biological activity, we first chemically synthesized each dodecapeptide and analysed itsin vitrobioactivity on Arabidopsis seedlings. Similarly, but to a different extent, three types of poplar CLV3-related peptides caused root meristem consumption, phyllotaxis disorder, anthocyanin accumulation and failure to enter the bolting stage. In comparison, application of two poplar TDIF-related peptides led to root length promotion in a dose-dependent manner with an even stronger effect observed for poplar TDIF-like peptide than TDIF. Next, we constructedCaMV35S:PtCLEtransgenic plants for each of the ninePtCLEgenes. Phenotypic abnormalities exemplified by arrested shoot apical meristem and abnormal flower structure were found to be more dominant and severe in35S:PtCLV3and35S:PtCLV3-like2lines than in the35S:PtCLV3-like1line. Disordered vasculature was detected in both stem and hypocotyl cross-sections in Arabidopsis plants over-expressing poplarTDIF-relatedgenes with the most defective vascular patterning observed forTDIF2and twoTDIF-likegenes. Phenotypic difference consistently observed in peptide application assay and transgenic analysis indicated the functional diversity of nine poplarPtCLEgenes under investigation. This work represents the first report on the functional analysis ofCLEgenes in a tree species and constitutes a basis for further study of the CLE peptide signalling pathway in tree development. PMID:26912800

  17. Involvement of auxin and CKs in boron deficiency induced changes in apical dominance of pea plants (Pisum sativum L.).

    PubMed

    Wang, Guoying; Römheld, Volker; Li, Chunjian; Bangerth, Fritz

    2006-04-01

    It has previously been shown that boron (B) deficiency inhibits growth of the plant apex, which consequently results in a relatively weak apical dominance, and a subsequent sprouting of lateral buds. Auxin and cytokinins (CKs) are the two most important phytohormones involved in the regulation of apical dominance. In this study, the possible involvement of these two hormones in B-deficiency-induced changes in apical dominance was investigated by applying B or the synthetic CK CPPU to the shoot apex of pea plants grown in nutrient solution without B supply. Export of IAA out of the shoot apex, as well as the level of IAA, Z/ZR and isopentenyl-adenine/isopentenyl-adenosine (i-Ade/i-Ado) in the shoot apex were assayed. In addition, polar IAA transport capacity was measured in two internodes of different ages using 3H-IAA. In B-deficient plants, both the level of auxin and CKs were reduced, and the export of auxin from the shoot apex was considerably decreased relative to plants well supplied with B. Application of B to the shoot apex restored the endogenous Z/ZR and IAA level to control levels and increased the export of IAA from the shoot apex, as well as the 3H-IAA transport capacity in the newly developed internodes. Further, B application to the shoot apex inhibited lateral bud growth and stimulated lateral root formation, presumably by stimulated polar IAA transport. Applying CPPU to the shoot apex, a treatment that stimulates IAA export under adequate B supply, considerably reduced the endogenous Z/ZR concentration in the shoot apex, but had no stimulatory effect on IAA concentration and transport in B-deficient plants. A similar situation appeared to exist in lateral buds of B-deficient plants as, in contrast to plants well supplied with B, application of CKs to these plants did not stimulate lateral bud growth. In contrast to the changes of Z/ZR levels in the shoot apex, which occurred after application of B or CPPU, the levels of i-Ade/i-Ado stayed more or

  18. Floral Induction in Arabidopsis by FLOWERING LOCUS T Requires Direct Repression of BLADE-ON-PETIOLE Genes by the Homeodomain Protein PENNYWISE1[OPEN

    PubMed Central

    Andrés, Fernando; Romera-Branchat, Maida; Martínez-Gallegos, Rafael; Patel, Vipul; Schneeberger, Korbinian; Jang, Seonghoe; Altmüller, Janine; Nürnberg, Peter; Coupland, George

    2015-01-01

    Flowers form on the flanks of the shoot apical meristem (SAM) in response to environmental and endogenous cues. In Arabidopsis (Arabidopsis thaliana), the photoperiodic pathway acts through FLOWERING LOCUS T (FT) to promote floral induction in response to day length. A complex between FT and the basic leucine-zipper transcription factor FD is proposed to form in the SAM, leading to activation of APETALA1 and LEAFY and thereby promoting floral meristem identity. We identified mutations that suppress FT function and recovered a new allele of the homeodomain transcription factor PENNYWISE (PNY). Genetic and molecular analyses showed that ectopic expression of BLADE-ON-PETIOLE1 (BOP1) and BOP2, which encode transcriptional coactivators, in the SAM during vegetative development, confers the late flowering of pny mutants. In wild-type plants, BOP1 and BOP2 are expressed in lateral organs close to boundaries of the SAM, whereas in pny mutants, their expression occurs in the SAM. This ectopic expression lowers FD mRNA levels, reducing responsiveness to FT and impairing activation of APETALA1 and LEAFY. We show that PNY binds to the promoters of BOP1 and BOP2, repressing their transcription. These results demonstrate a direct role for PNY in defining the spatial expression patterns of boundary genes and the significance of this process for floral induction by FT. PMID:26417007

  19. Floral Induction in Arabidopsis by FLOWERING LOCUS T Requires Direct Repression of BLADE-ON-PETIOLE Genes by the Homeodomain Protein PENNYWISE.

    PubMed

    Andrés, Fernando; Romera-Branchat, Maida; Martínez-Gallegos, Rafael; Patel, Vipul; Schneeberger, Korbinian; Jang, Seonghoe; Altmüller, Janine; Nürnberg, Peter; Coupland, George

    2015-11-01

    Flowers form on the flanks of the shoot apical meristem (SAM) in response to environmental and endogenous cues. In Arabidopsis (Arabidopsis thaliana), the photoperiodic pathway acts through FLOWERING LOCUS T (FT) to promote floral induction in response to day length. A complex between FT and the basic leucine-zipper transcription factor FD is proposed to form in the SAM, leading to activation of APETALA1 and LEAFY and thereby promoting floral meristem identity. We identified mutations that suppress FT function and recovered a new allele of the homeodomain transcription factor PENNYWISE (PNY). Genetic and molecular analyses showed that ectopic expression of BLADE-ON-PETIOLE1 (BOP1) and BOP2, which encode transcriptional coactivators, in the SAM during vegetative development, confers the late flowering of pny mutants. In wild-type plants, BOP1 and BOP2 are expressed in lateral organs close to boundaries of the SAM, whereas in pny mutants, their expression occurs in the SAM. This ectopic expression lowers FD mRNA levels, reducing responsiveness to FT and impairing activation of APETALA1 and LEAFY. We show that PNY binds to the promoters of BOP1 and BOP2, repressing their transcription. These results demonstrate a direct role for PNY in defining the spatial expression patterns of boundary genes and the significance of this process for floral induction by FT. PMID:26417007

  20. ASYMMETRIC LEAVES2 gene, a member of LOB/AS2 family of Arabidopsis thaliana, causes an abaxializing leaves in transgenic cockscomb.

    PubMed

    Sun, Shao-Bo; Song, Jiang-Ping; Meng, Lai-Sheng

    2012-04-01

    The leaf primordium derives from the peripheral zone of shoot apical meristem. During the formation of leaf primordia, they need to establish the proximodistal, mediolateral, and ab/adaxial axes. Among these axes, the ab/adaxial axis might be the most important. ASYMMETRIC LEAVES2 (AS2) gene is a member of AS2/LATERAL ORGAN BOUNDARY (LOB) family of Arabidopsis thaliana. In this work, we transformed 35S:AS2 transgene constructs to cockscomb (Celosia cristata) via Agrobacterium tumefaciens. All primary transformants subsequently obtained were placed into phenotypic categories and self-pollinated. As a whole, a total of 44 T1 35S:AS2 cockscomb plants obtained were grouped into two major categories: (I) slightly wrinkled leaves (28/44), (II) extremely curved leaves (16/44), on the basis of their leaf phenotypes. Furthermore, we characterized the anatomical features of these malformed leaves; and found the transformation of adaxial cell types into abaxial cell ones. A series of data suggest that AS2 might be involved in the determination of abaxial polarity in cockscomb plants. However, a few research teams have reported that AS2 might be involved in the determination of adaxial polarity in leaf primodia of Arabidopsis thaliana. These data above indicate that the roles of the same ab/adaxial determinant might differ between distinct species. At last, the different function of AS2 in distinct species was discussed. PMID:22143880

  1. HANABA TARANU (HAN) Bridges Meristem and Organ Primordia Boundaries through PINHEAD, JAGGED, BLADE-ON-PETIOLE2 and CYTOKININ OXIDASE 3 during Flower Development in Arabidopsis.

    PubMed

    Ding, Lian; Yan, Shuangshuang; Jiang, Li; Zhao, Wensheng; Ning, Kang; Zhao, Jianyu; Liu, Xiaofeng; Zhang, Juan; Wang, Qian; Zhang, Xiaolan

    2015-09-01

    Shoot organ primordia are initiated from the shoot apical meristem and develop into leaves during the vegetative stage, and into flowers during the reproductive phase. Between the meristem and the newly formed organ primordia, a boundary with specialized cells is formed that separates meristematic activity from determinate organ growth. Despite interactions that have been found between boundary regulators with genes controlling meristem maintenance or primordial development, most boundary studies were performed during embryogenesis or vegetative growth, hence little is known about whether and how boundaries communicate with meristem and organ primordia during the reproductive stage. We combined genetic, molecular and biochemical tools to explore interactions between the boundary gene HANABA TARANU (HAN) and two meristem regulators BREVIPEDICELLUS (BP) and PINHEAD (PNH), and three primordia-specific genes PETAL LOSS (PTL), JAGGED (JAG) and BLADE-ON-PETIOLE (BOP) during flower development. We demonstrated the key role of HAN in determining petal number, as part of a set of complex genetic interactions. HAN and PNH transcriptionally promote each other, and biochemically interact to regulate meristem organization. HAN physically interacts with JAG, and directly stimulates the expression of JAG and BOP2 to regulate floral organ development. Further, HAN directly binds to the promoter and intron of CYTOKININ OXIDASE 3 (CKX3) to modulate cytokinin homeostasis in the boundary. Our data suggest that boundary-expressing HAN communicates with the meristem through the PNH, regulates floral organ development via JAG and BOP2, and maintains boundary morphology through CKX3 during flower development in Arabidopsis. PMID:26390296

  2. HANABA TARANU (HAN) Bridges Meristem and Organ Primordia Boundaries through PINHEAD, JAGGED, BLADE-ON-PETIOLE2 and CYTOKININ OXIDASE 3 during Flower Development in Arabidopsis

    PubMed Central

    Zhao, Wensheng; Ning, Kang; Zhao, Jianyu; Liu, Xiaofeng; Zhang, Juan; Wang, Qian; Zhang, Xiaolan

    2015-01-01

    Shoot organ primordia are initiated from the shoot apical meristem and develop into leaves during the vegetative stage, and into flowers during the reproductive phase. Between the meristem and the newly formed organ primordia, a boundary with specialized cells is formed that separates meristematic activity from determinate organ growth. Despite interactions that have been found between boundary regulators with genes controlling meristem maintenance or primordial development, most boundary studies were performed during embryogenesis or vegetative growth, hence little is known about whether and how boundaries communicate with meristem and organ primordia during the reproductive stage. We combined genetic, molecular and biochemical tools to explore interactions between the boundary gene HANABA TARANU (HAN) and two meristem regulators BREVIPEDICELLUS (BP) and PINHEAD (PNH), and three primordia-specific genes PETAL LOSS (PTL), JAGGED (JAG) and BLADE-ON-PETIOLE (BOP) during flower development. We demonstrated the key role of HAN in determining petal number, as part of a set of complex genetic interactions. HAN and PNH transcriptionally promote each other, and biochemically interact to regulate meristem organization. HAN physically interacts with JAG, and directly stimulates the expression of JAG and BOP2 to regulate floral organ development. Further, HAN directly binds to the promoter and intron of CYTOKININ OXIDASE 3 (CKX3) to modulate cytokinin homeostasis in the boundary. Our data suggest that boundary-expressing HAN communicates with the meristem through the PNH, regulates floral organ development via JAG and BOP2, and maintains boundary morphology through CKX3 during flower development in Arabidopsis. PMID:26390296

  3. A gain-of-function mutation in Msl10 triggers cell death and wound-induced hyperaccumulation of jasmonic acid in Arabidopsis.

    PubMed

    Zou, Yan; Chintamanani, Satya; He, Ping; Fukushige, Hirotada; Yu, Liping; Shao, Meiyu; Zhu, Lihuang; Hildebrand, David F; Tang, Xiaoyan; Zhou, Jian-Min

    2016-06-01

    Jasmonates (JAs) are rapidly induced after wounding and act as key regulators for wound induced signaling pathway. However, what perceives the wound signal and how that triggers JA biosynthesis remains poorly understood. To identify components involved in Arabidopsis wound and JA signaling pathway, we screened for mutants with abnormal expression of a luciferase reporter, which is under the control of a wound-responsive promoter of an ethylene response factor (ERF) transcription factor gene, RAP2.6 (Related to APetala 2.6). The rea1 (RAP2.6 expresser in shoot apex) mutant constitutively expressed the RAP2.6-LUC reporter gene in young leaves. Along with the typical JA phenotypes including shorter petioles, loss of apical dominance, accumulation of anthocyanin pigments and constitutive expression of JA response gene, rea1 plants also displayed cell death and accumulated high levels of JA in response to wounding. The phenotype of rea1 mutant is caused by a gain-of-function mutation in the C-terminus of a mechanosensitive ion channel MscS-like 10 (MSL10). MSL10 is localized in the plasma membrane and is expressed predominantly in root tip, shoot apex and vascular tissues. These results suggest that MSL10 is involved in the wound-triggered early signal transduction pathway and possibly in regulating the positive feedback synthesis of JA. PMID:26356550

  4. The EXS Domain of PHO1 Participates in the Response of Shoots to Phosphate Deficiency via a Root-to-Shoot Signal1[OPEN

    PubMed Central

    Jung, Ji-Yul; Pradervand, Sylvain

    2016-01-01

    The response of shoots to phosphate (Pi) deficiency implicates long-distance communication between roots and shoots, but the participating components are poorly understood. We have studied the topology of the Arabidopsis (Arabidopsis thaliana) PHOSPHATE1 (PHO1) Pi exporter and defined the functions of its different domains in Pi homeostasis and signaling. The results indicate that the amino and carboxyl termini of PHO1 are both oriented toward the cytosol and that the protein spans the membrane twice in the EXS domain, resulting in a total of six transmembrane α-helices. Using transient expression in Nicotiana benthamiana leaf, we demonstrated that the EXS domain of PHO1 is essential for Pi export activity and proper localization to the Golgi and trans-Golgi network, although the EXS domain by itself cannot mediate Pi export. In contrast, removal of the amino-terminal hydrophilic SPX domain does not affect the Pi export capacity of the truncated PHO1 in N. benthamiana. While the Arabidopsis pho1 mutant has low shoot Pi and shows all the hallmarks associated with Pi deficiency, including poor shoot growth and overexpression of numerous Pi deficiency-responsive genes, expression of only the EXS domain of PHO1 in the roots of the pho1 mutant results in a remarkable improvement of shoot growth despite low shoot Pi. Transcriptomic analysis of pho1 expressing the EXS domain indicates an attenuation of the Pi signaling cascade and the up-regulation of genes involved in cell wall synthesis and the synthesis or response to several phytohormones in leaves as well as an altered expression of genes responsive to abscisic acid in roots. PMID:26546667

  5. Genome-wide study of KNOX regulatory network reveals brassinosteroid catabolic genes important for shoot meristem function in rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In flowering plants, knotted1-like homeobox (KNOX) transcription factors play crucial roles in establishment and maintenance of the shoot apical meristem (SAM), from which aerial organs such as leaves, stems, and flowers initiate. We report that a rice (Oryza sativa) KNOX gene Oryza sativa homeobox1...

  6. Shooting Star Experiment

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Shooting Star Experiment (SSE) is designed to develop and demonstrate the technology required to focus the Sun's energy and use the energy for inexpensive space propulsion research. Pictured is an engineering model (Pathfinder III) of SSE and its thermal vacuum test to simulate in-orbit conditions at the X-Ray Calibration Facility at the Marshall Space Flight Center (MSFC). This model was used to test and characterize the motion and deformation of the structure caused by thermal effects. In this photograph, alignment targets are being placed on the engineering model so that a theodolite (alignment telescope) could be used to accurately measure the deformation and deflection of the engineering model under extreme condition, such as the coldness of deep space and the hotness of the Sun, as well as vacuum.

  7. The Myb-domain protein ULTRAPETALA1 INTERACTING FACTOR 1 controls floral meristem activities in Arabidopsis.

    PubMed

    Moreau, Fanny; Thévenon, Emmanuel; Blanvillain, Robert; Lopez-Vidriero, Irene; Franco-Zorrilla, Jose Manuel; Dumas, Renaud; Parcy, François; Morel, Patrice; Trehin, Christophe; Carles, Cristel C

    2016-04-01

    Higher plants continuously and iteratively produce new above-ground organs in the form of leaves, stems and flowers. These organs arise from shoot apical meristems whose homeostasis depends on coordination between self-renewal of stem cells and their differentiation into organ founder cells. This coordination is stringently controlled by the central transcription factor WUSCHEL (WUS), which is both necessary and sufficient for stem cell specification in Arabidopsis thaliana ULTRAPETALA1 (ULT1) was previously identified as a plant-specific, negative regulator of WUS expression. However, molecular mechanisms underlying this regulation remain unknown. ULT1 protein contains a SAND putative DNA-binding domain and a B-box, previously proposed as a protein interaction domain in eukaryotes. Here, we characterise a novel partner of ULT1, named ULT1 INTERACTING FACTOR 1 (UIF1), which contains a Myb domain and an EAR motif. UIF1 and ULT1 function in the same pathway for regulation of organ number in the flower. Moreover, UIF1 displays DNA-binding activity and specifically binds to WUS regulatory elements. We thus provide genetic and molecular evidence that UIF1 and ULT1 work together in floral meristem homeostasis, probably by direct repression of WUS expression. PMID:26903506

  8. WOX2 and STIMPY-LIKE/WOX8 promote cotyledon boundary formation in Arabidopsis.

    PubMed

    Lie, Catharine; Kelsom, Corey; Wu, Xuelin

    2012-11-01

    One of the key events in dicot plant embryogenesis is the emergence of the two cotyledon primordia, which marks the transition from radial symmetry to bilateral symmetry. In Arabidopsis thaliana, the three CUP-SHAPED COTYLEDON (CUC) genes are responsible for determining the boundary region between the cotyledons. However, the mechanisms controlling their transcription activation are not well understood. Previous studies found that several WOX family homeobox transcription factors are involved in embryo apical patterning and cotyledon development. Here we show that WOX2 and STIMPY-LIKE (STPL/WOX8) act redundantly to differentially regulate the expression of the CUC genes in promoting the establishment of the cotyledon boundary, without affecting the primary shoot meristem. Loss of both WOX2 and STPL results in reduced CUC2 and CUC3 expression in one side of the embryo, but an expansion of the CUC1 domain. Furthermore, we found that STPL is expressed in the embryo proper, and its activation is enhanced by the removal of WOX2, providing an explanation for the functional redundancy between WOX2 and STPL. Additional evidence also showed that WOX2 and STPL function independently in regulating different aspects of local auxin gradient formation during early embryogenesis. PMID:22827849

  9. Gibberellic acid signaling is required for ambient temperature-mediated induction of flowering in Arabidopsis thaliana.

    PubMed

    Galvão, Vinicius Costa; Collani, Silvio; Horrer, Daniel; Schmid, Markus

    2015-12-01

    Distinct molecular mechanisms integrate changes in ambient temperature into the genetic pathways that govern flowering time in Arabidopsis thaliana. Temperature-dependent eviction of the histone variant H2A.Z from nucleosomes has been suggested to facilitate the expression of FT by PIF4 at elevated ambient temperatures. Here we show that, in addition to PIF4, PIF3 and PIF5, but not PIF1 and PIF6, can promote flowering when expressed specifically in phloem companion cells (PCC), where they can induce FT and its close paralog, TSF. However, despite their strong potential to promote flowering, genetic analyses suggest that the PIF genes seem to have only a minor role in adjusting flowering in response to photoperiod or high ambient temperature. In addition, loss of PIF function only partially suppressed the early flowering phenotype and FT expression of the arp6 mutant, which is defective in H2A.Z deposition. In contrast, the chemical inhibition of gibberellic acid (GA) biosynthesis resulted in a strong attenuation of early flowering and FT expression in arp6. Furthermore, GA was able to induce flowering at low temperature (15°C) independently of FT, TSF, and the PIF genes, probably directly at the shoot apical meristem. Together, our results suggest that the timing of the floral transition in response to ambient temperature is more complex than previously thought and that GA signaling might play a crucial role in this process. PMID:26466761

  10. A School Shooting Plot Foiled

    ERIC Educational Resources Information Center

    Swezey, James A.; Thorp, Kimberly A.

    2010-01-01

    Dinkes, Cataldi, and Lin-Kelly (2007) claims that 78% of public schools reported one or more violent incidents during the 2005/2006 school year. School shootings are a rare but real threat on school campuses. Shootings at private schools are even less frequent with only a few recorded examples in the United States. This case study examines how a…

  11. Shooting and Hunting: Instructor's Guide.

    ERIC Educational Resources Information Center

    Smith, Julian W., Comp.

    The shooting and hunting manual, part of a series of books and pamphlets on outdoor education, explains shooting skills, hunting, and proper gun handling on the range and in the field. This manual should be supplemented and enriched by available references, facilities, and resources. It may be included in the community's educational and…

  12. FAR-RED ELONGATED HYPOCOTYL3 activates SEPALLATA2 but inhibits CLAVATA3 to regulate meristem determinacy and maintenance in Arabidopsis.

    PubMed

    Li, Dongming; Fu, Xing; Guo, Lin; Huang, Zhigang; Li, Yongpeng; Liu, Yang; He, Zishan; Cao, Xiuwei; Ma, Xiaohan; Zhao, Meicheng; Zhu, Guohui; Xiao, Langtao; Wang, Haiyang; Chen, Xuemei; Liu, Renyi; Liu, Xigang

    2016-08-16

    Plant meristems are responsible for the generation of all plant tissues and organs. Here we show that the transcription factor (TF) FAR-RED ELONGATED HYPOCOTYL3 (FHY3) plays an important role in both floral meristem (FM) determinacy and shoot apical meristem maintenance in Arabidopsis, in addition to its well-known multifaceted roles in plant growth and development during the vegetative stage. Through genetic analyses, we show that WUSCHEL (WUS) and CLAVATA3 (CLV3), two central players in the establishment and maintenance of meristems, are epistatic to FHY3 Using genome-wide ChIP-seq and RNA-seq data, we identify hundreds of FHY3 target genes in flowers and find that FHY3 mainly acts as a transcriptional repressor in flower development, in contrast to its transcriptional activator role in seedlings. Binding motif-enrichment analyses indicate that FHY3 may coregulate flower development with three flower-specific MADS-domain TFs and four basic helix-loop-helix TFs that are involved in photomorphogenesis. We further demonstrate that CLV3, SEPALLATA1 (SEP1), and SEP2 are FHY3 target genes. In shoot apical meristem, FHY3 directly represses CLV3, which consequently regulates WUS to maintain the stem cell pool. Intriguingly, CLV3 expression did not change significantly in fhy3 and phytochrome B mutants before and after light treatment, indicating that FHY3 and phytochrome B are involved in light-regulated meristem activity. In FM, FHY3 directly represses CLV3, but activates SEP2, to ultimately promote FM determinacy. Taken together, our results reveal insights into the mechanisms of meristem maintenance and determinacy, and illustrate how the roles of a single TF may vary in different organs and developmental stages. PMID:27469166

  13. Specification of epidermal cell fate in plant shoots.

    PubMed

    Takada, Shinobu; Iida, Hiroyuki

    2014-01-01

    Land plants have evolved a single layer of epidermal cells, which are characterized by mostly anticlinal cell division patterns, formation of a waterproof coat called cuticle, and unique cell types such as stomatal guard cells and trichomes. The shoot epidermis plays important roles not only to protect plants from dehydration and pathogens but also to ensure their proper organogenesis and growth control. Extensive molecular genetic studies in Arabidopsis and maize have identified a number of genes that are required for epidermal cell differentiation. However, the mechanism that specifies shoot epidermal cell fate during plant organogenesis remains largely unknown. Particularly, little is known regarding positional information that should restrict epidermal cell fate to the outermost cell layer of the developing organs. Recent studies suggested that certain members of the HD-ZIP class IV homeobox genes are possible master regulators of shoot epidermal cell fate. Here, we summarize the roles of the regulatory genes that are involved in epidermal cell fate specification and discuss the possible mechanisms that limit the expression and/or activity of the master transcriptional regulators to the outermost cell layer in plant shoots. PMID:24616724

  14. Somatic embryogenesis in Arabidopsis thaliana is facilitated by mutations in genes repressing meristematic cell divisions.

    PubMed

    Mordhorst, A P; Voerman, K J; Hartog, M V; Meijer, E A; van Went, J; Koornneef, M; de Vries, S C

    1998-06-01

    Embryogenesis in plants can commence from cells other than the fertilized egg cell. Embryogenesis initiated from somatic cells in vitro is an attractive system for studying early embryonic stages when they are accessible to experimental manipulation. Somatic embryogenesis in Arabidopsis offers the additional advantage that many zygotic embryo mutants can be studied under in vitro conditions. Two systems are available. The first employs immature zygotic embryos as starting material, yielding continuously growing embryogenic cultures in liquid medium. This is possible in at least 11 ecotypes. A second, more efficient and reproducible system, employing the primordia timing mutant (pt allelic to hpt, cop2, and amp1), was established. A significant advantage of the pt mutant is that intact seeds, germinated in 2,4-dichlorophenoxyacetic acid (2, 4-D) containing liquid medium, give rise to stable embryonic cell cultures, circumventing tedious hand dissection of immature zygotic embryos. pt zygotic embryos are first distinguishable from wild type at early heart stage by a broader embryonic shoot apical meristem (SAM). In culture, embryogenic clusters originate from the enlarged SAMs. pt somatic embryos had all characteristic embryo pattern elements seen in zygotic embryos, but with higher and more variable numbers of cells. Embryogenic cell cultures were also established from seedling, of other mutants with enlarged SAMs, such as clavata (clv). pt clv double mutants showed additive effects on SAM size and an even higher frequency of seedlings producing embryogenic cell lines. pt clv double mutant plants had very short fasciated inflorescence stems and additive effects on the number of rosette leaves. This suggests that the PT and CLV genes act in independent pathways that control SAM size. An increased population of noncommitted SAM cells may be responsible for facilitated establishment of somatic embryogenesis in Arabidopsis. PMID:9611173

  15. Somatic embryogenesis in Arabidopsis thaliana is facilitated by mutations in genes repressing meristematic cell divisions.

    PubMed Central

    Mordhorst, A P; Voerman, K J; Hartog, M V; Meijer, E A; van Went, J; Koornneef, M; de Vries, S C

    1998-01-01

    Embryogenesis in plants can commence from cells other than the fertilized egg cell. Embryogenesis initiated from somatic cells in vitro is an attractive system for studying early embryonic stages when they are accessible to experimental manipulation. Somatic embryogenesis in Arabidopsis offers the additional advantage that many zygotic embryo mutants can be studied under in vitro conditions. Two systems are available. The first employs immature zygotic embryos as starting material, yielding continuously growing embryogenic cultures in liquid medium. This is possible in at least 11 ecotypes. A second, more efficient and reproducible system, employing the primordia timing mutant (pt allelic to hpt, cop2, and amp1), was established. A significant advantage of the pt mutant is that intact seeds, germinated in 2,4-dichlorophenoxyacetic acid (2, 4-D) containing liquid medium, give rise to stable embryonic cell cultures, circumventing tedious hand dissection of immature zygotic embryos. pt zygotic embryos are first distinguishable from wild type at early heart stage by a broader embryonic shoot apical meristem (SAM). In culture, embryogenic clusters originate from the enlarged SAMs. pt somatic embryos had all characteristic embryo pattern elements seen in zygotic embryos, but with higher and more variable numbers of cells. Embryogenic cell cultures were also established from seedling, of other mutants with enlarged SAMs, such as clavata (clv). pt clv double mutants showed additive effects on SAM size and an even higher frequency of seedlings producing embryogenic cell lines. pt clv double mutant plants had very short fasciated inflorescence stems and additive effects on the number of rosette leaves. This suggests that the PT and CLV genes act in independent pathways that control SAM size. An increased population of noncommitted SAM cells may be responsible for facilitated establishment of somatic embryogenesis in Arabidopsis. PMID:9611173

  16. A subgroup of MATE transporter genes regulates hypocotyl cell elongation in Arabidopsis.

    PubMed

    Wang, Rui; Liu, Xiayan; Liang, Shuang; Ge, Qing; Li, Yuanfeng; Shao, Jingxia; Qi, Yafei; An, Lijun; Yu, Fei

    2015-10-01

    The growth of higher plants is under complex regulation to ensure the elaboration of developmental programmes under a changing environment. To dissect these regulatory circuits, we carried out genetic screens for Arabidopsis abnormal shoot (abs) mutants with altered shoot development. Here, we report the isolation of two dominant mutants, abs3-1D and abs4-1D, through activation tagging. Both mutants showed a 'bushy' loss of apical dominance phenotype. ABS3 and ABS4 code for two closely related putative Multidrug and Toxic Compound Extrusion (MATE) family of efflux transporters, respectively. ABS3 and ABS4, as well as two related MATE genes, ABS3-Like1 (ABS3L1) and ABS3L2, showed diverse tissue expression profiles but their gene products all localized to the late endosome/prevacuole (LE/PVC) compartment. The over-expression of these four genes individually led to the inhibition of hypocotyl cell elongation in the light. On the other hand, the quadruple knockout mutant (mateq) showed the opposite phenotype of an enhanced hypocotyl cell elongation in the light. Hypocotyl cell elongation and de-etiolation processes in the dark were also affected by the mutations of these genes. Exogenously applied sucrose attenuated the inhibition of hypocotyl elongation caused by abs3-1D and abs4-1D in the dark, and enhanced the hypocotyl elongation of mateq under prolonged dark treatment. We determined that ABS3 genetically interacts with the photoreceptor gene PHYTOCHROME B (PHYB). Our results demonstrate that ABS3 and related MATE family transporters are potential negative regulators of hypocotyl cell elongation and support a functional link between the endomembrane system, particularly the LE/PVC, and the regulation of plant cell elongation. PMID:26160579

  17. Cell lineage patterns in the shoot meristem of the sunflower embryo in the dry seed

    SciTech Connect

    Jegla, D.E.; Sussex, I.M.

    1989-01-01

    We mapped the fate of cells in the shoot meristem of the dry-seed embryo of sunflower, Helianthus annuus L. cv. Peredovic, using irradiation-induced somatic sectors. We analyzed 249 chlorophyll-deficient or glabrous (hairless) sectors generated in 236 plants. Most sectors observed in the inflorescence extended into vegetative nodes. Thus cell lineages that ultimately gave rise to reproductive structures also contributed to vegetative structures. No single sector extended the entire length of the shoot. Thus the shoot is not derived from one or a few apical initials. Rather, the position, vertical extent, and width of the sectors at different levels of the shoot suggest that the shoot is derived from three to four circumferential populations of cells in each of three cell layers of the embryo meristem. Sectors had no common boundaries even in plants with two or three independent sectors, but varied in extent and overlapped along the length of the shoot. Thus individual cells in a single circumferential population behaved independently to contribute lineages of different vertical extents to the growing shoot. The predicted number of circumferential populations of cells as well as the apparent cell number in each population was consistent with the actual number of cells in the embryo meristem observed in histological sections.

  18. Gradual shifts in sites of free-auxin production during leaf-primordium development and their role in vascular differentiation and leaf morphogenesis in Arabidopsis.

    PubMed

    Aloni, Roni; Schwalm, Katja; Langhans, Markus; Ullrich, Cornelia I

    2003-03-01

    The major regulatory shoot signal is auxin, whose synthesis in young leaves has been a mystery. To test the leaf-venation hypothesis [R. Aloni (2001) J Plant Growth Regul 20: 22-34], the patterns of free-auxin production, movement and accumulation in developing leaf primordia of DR5::GUS-transformed Arabidopsis thaliana (L.) Heynh. were visualized. DR5::GUS expression was regarded to reflect sites of free auxin, while immunolocalization with specific monoclonal antibodies indicated total auxin distribution. The mRNA expression of key enzymes involved in the synthesis, conjugate hydrolysis, accumulation and basipetal transport of auxin, namely indole-3-glycerol-phosphate-synthase, nitrilase, IAA-amino acid hydrolase, chalcone synthase and PIN1 as an essential component of the basipetal IAA carrier, was investigated by reverse transcription-polymerase chain reaction. Near the shoot apex, stipules were the earliest sites of high free-auxin production. During early stages of primordium development, leaf apical dominance was evident from strong beta-glucuronidase activity in the elongating tip, possibly suppressing the production of free auxin in the leaf tissues below it. Hydathodes, which develop in the tip and later in the lobes, were apparently primary sites of high free-auxin production, the latter supported by auxin-conjugate hydrolysis, auxin retention by the chalcone synthase-dependent action of flavonoids and also by the PIN1-component of the carrier-mediated basipetal transport. Trichomes and mesophyll cells were secondary sites of free-auxin production. During primordium development there are gradual shifts in sites and concentrations of free-auxin production occurring first in the tip of a leaf primordium, then progressing basipetally along the margins, and finally appearing also in the central regions of the lamina. This developmental pattern of free-auxin production is suggested to control the basipetal maturation sequence of leaf development and vascular

  19. The CLAVATA signaling pathway mediating stem cell fate in shoot meristems requires Ca(2+) as a secondary cytosolic messenger.

    PubMed

    Chou, Hsuan; Zhu, Yingfang; Ma, Yi; Berkowitz, Gerald A

    2016-02-01

    CLAVATA1 (CLV1) is a receptor protein expressed in the shoot apical meristem (SAM) that translates perception of a non-cell-autonomous CLAVATA3 (CLV3) peptide signal into altered stem cell fate. CLV3 reduces expression of WUSCHEL (WUS) and FANTASTIC FOUR 2 (FAF2) in the SAM. Expression of WUS and FAF2 leads to maintenance of undifferentiated stem cells in the SAM. CLV3 binding to CLV1 inhibits expression of these genes and controls stem cell fate in the SAM through an unidentified signaling pathway. Cytosolic Ca(2+) elevations, cyclic nucleotide (cGMP)-activated Ca(2+) channels, and cGMP have been linked to signaling downstream of receptors similar to CLV1. Hence, we hypothesized that cytosolic Ca(2+) elevation mediates the CLV3 ligand/CLV1 receptor signaling that controls meristem stem cell fate. CLV3 application to Arabidopsis seedlings results in elevation of cytosolic Ca(2+) and cGMP. CLV3 control of WUS was prevented in a genotype lacking a functional cGMP-activated Ca(2+) channel. In wild-type plants, CLV3 inhibition of WUS and FAF2 expression was impaired by treatment with either a Ca(2+) channel blocker or a guanylyl cyclase inhibitor. When CLV3-dependent repression of WUS is blocked, altered control of stem cell fate leads to an increase in SAM size; we observed a larger SAM size in seedlings treated with the Ca(2+) channel blocker. These results suggest that the CLV3 ligand/CLV1 receptor system initiates a signaling cascade that elevates cytosolic Ca(2+) , and that this cytosolic secondary messenger is involved in the signal transduction cascade linking CLV3/CLV1 to control of gene expression and stem cell fate in the SAM. PMID:26756833

  20. Surgical treatments for vaginal apical prolapse.

    PubMed

    Kong, Mi Kyung; Bai, Sang Wook

    2016-07-01

    Pelvic organ prolapse is a common condition, occurring in up to 11% of women in the United States. Often, pelvic organ prolapse recurs after surgery; when it recurs after hysterectomy, it frequently presents as vaginal apical prolapse. There are many different surgical treatments for vaginal apical prolapse; among them, abdominal sacral colpopexy is considered the gold standard. However, recent data reveal that other surgical procedures also result in good outcome. This review discusses the various surgical treatments for vaginal apical prolapse including their risks and benefits. PMID:27462591

  1. Surgical treatments for vaginal apical prolapse

    PubMed Central

    Kong, Mi Kyung

    2016-01-01

    Pelvic organ prolapse is a common condition, occurring in up to 11% of women in the United States. Often, pelvic organ prolapse recurs after surgery; when it recurs after hysterectomy, it frequently presents as vaginal apical prolapse. There are many different surgical treatments for vaginal apical prolapse; among them, abdominal sacral colpopexy is considered the gold standard. However, recent data reveal that other surgical procedures also result in good outcome. This review discusses the various surgical treatments for vaginal apical prolapse including their risks and benefits. PMID:27462591

  2. High-frequency in vitro plantlet regeneration from apical bud as a novel explant of Carum copticum L.

    PubMed Central

    Salehi, Mansoureh; Hosseini, Bahman; Jabbarzadeh, Zohreh

    2014-01-01

    Objective To develop an in vitro regeneration system to increase the recovery of Carum copticum L. plantlets as a part of developing a metabolic engineering program. Methods The efficacy of different concentrations and combinations of 6-benzyladenine, indole-3-acetic acid and indole butyric acid on direct shoot regeneration and rooting of ajowan from apical bud explants were assessed. All explants were cultured on Murashige and Skoog (MS) medium supplemented with different combinations of 6-benzyl amino purine (BAP) (0, 2.2, 4.4, 8.8 µmol/L) and indole-3-acetic acid (IAA) (0, 0.5, 1.1, 2.2 µmol/L). Results The maximum shoot regeneration frequency (97.5%) and the highest number of shoots produced from apical buds (34 shoots per explant) were obtained on MS medium fortified with BAP (4.4 µmol/L) and IAA (0.5 µmol/L). Low shoot regeneration frequency was observed in BAP free treatments. The effects of different strengths of MS medium and various concentrations of IAA and indole-3- butyric acid on rooting rate, length and average number of roots were also investigated. Application of indole-3- butyric acid (6 µmol/L) in full-strength MS medium, was more effective than IAA and resulted in highest shoot regeneration frequency with the rooting rate of 100% and highest mean number of roots per shoot (41.8). The rooted plantlets were acclimatized successfully in greenhouse conditions with a survival rate of 90%. Conclusion In this study, a simple and reliable regeneration and acclimatization protocol for Carum copticum has been presented. This protocol can be found very advantageous for a variety of purposes, including mass multiplication of Carum species, medicinal plant breeding studies and transgenic plant production. PMID:25183122

  3. A current perspective on the role of AGCVIII kinases in PIN-mediated apical hook development

    PubMed Central

    Willige, Björn C.; Chory, Joanne

    2015-01-01

    Despite their sessile lifestyle, seed plants are able to utilize differential growth rates to move their organs in response to their environment. Asymmetrical growth is the cause for the formation and maintenance of the apical hook—a structure of dicotyledonous plants shaped by the bended hypocotyl that eases the penetration through the covering soil. As predicted by the Cholodny–Went theory, the cause for differential growth is the unequal distribution of the phytohormone auxin. The PIN-FORMED proteins transport auxin from cell-to-cell and control the distribution of auxin in the plant. Their localization and activity are regulated by two subfamilies of AGCVIII protein kinases: the D6 PROTEIN KINASEs as well as PINOID and its two closely related WAG kinases. This mini-review focuses on the regulatory mechanism of these AGCVIII kinases as well as their role in apical hook development of Arabidopsis thaliana. PMID:26500658

  4. Dichotomous branching: the plant form and integrity upon the apical meristem bifurcation

    PubMed Central

    Gola, Edyta M.

    2014-01-01

    The division of the apical meristem into two independently functioning axes is defined as dichotomous branching. This type of branching typically occurs in non-vascular and non-seed vascular plants, whereas in seed plants it presents a primary growth form only in several taxa. Dichotomy is a complex process, which requires a re-organization of the meristem structure and causes changes in the apex geometry and activity. However, the mechanisms governing the repetitive apex divisions are hardly known. Here, an overview of dichotomous branching is presented, occurring in structurally different apices of phylogenetically distant plants, and in various organs (e.g., shoots, roots, rhizophores). Additionally, morphogenetic effects of dichotomy are reviewed, including its impact on organogenesis and mechanical constraints. At the end, the hormonal and genetic regulation of the dichotomous branching is discussed. PMID:24936206

  5. Localized auxin peaks in concentration-based transport models of the shoot apical meristem

    PubMed Central

    Draelants, Delphine; Avitabile, Daniele; Vanroose, Wim

    2015-01-01

    We study the formation of auxin peaks in a generic class of concentration-based auxin transport models, posed on static plant tissues. Using standard asymptotic analysis, we prove that, on bounded domains, auxin peaks are not formed via a Turing instability in the active transport parameter, but via simple corrections to the homogeneous steady state. When the active transport is small, the geometry of the tissue encodes the peaks’ amplitude and location: peaks arise where cells have fewer neighbours, that is, at the boundary of the domain. We test our theory and perform numerical bifurcation analysis on two models that are known to generate auxin patterns for biologically plausible parameter values. In the same parameter regimes, we find that realistic tissues are capable of generating a multitude of stationary patterns, with a variable number of auxin peaks, that can be selected by different initial conditions or by quasi-static changes in the active transport parameter. The competition between active transport and production rate determines whether peaks remain localized or cover the entire domain. In particular, changes in the auxin production that are fast with respect to the cellular life cycle affect the auxin peak distribution, switching from localized spots to fully patterned states. We relate the occurrence of localized patterns to a snaking bifurcation structure, which is known to arise in a wide variety of nonlinear media, but has not yet been reported in plant models. PMID:25878130

  6. A Real Shooting Star

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Click on the image for movie of A Real Shooting Star

    This artist's animation illustrates a star flying through our galaxy at supersonic speeds, leaving a 13-light-year-long trail of glowing material in its wake. The star, named Mira (pronounced my-rah) after the latin word for 'wonderful,' sheds material that will be recycled into new stars, planets and possibly even life. NASA's Galaxy Evolution Explorer discovered the long trail of material behind Mira during its survey of the entire sky in ultraviolet light.

    The animation begins by showing a close-up of Mira -- a red-giant star near the end of its life. Red giants are red in color and extremely bloated; for example, if a red giant were to replace our sun, it would engulf everything out to the orbit of Mars. They constantly blow off gas and dust in the form of stellar winds, supplying the galaxy with molecules, such as oxygen and carbon, that will make their way into new solar systems. Our sun will mature into a red giant in about 5 billion years.

    As the animation pulls out, we can see the enormous trail of material deposited behind Mira as it hurls along between the stars. Like a boat traveling through water, a bow shock, or build up of gas, forms ahead of the star in the direction of its motion. Gas in the bow shock is heated and then mixes with the cool hydrogen gas in the wind that is blowing off Mira. This heated hydrogen gas then flows around behind the star, forming a turbulent wake.

    Why does the trailing hydrogen gas glow in ultraviolet light? When it is heated, it transitions into a higher-energy state, which then loses energy by emitting ultraviolet light - a process known as fluorescence.

    Finally, the artist's rendering gives way to the actual ultraviolet image taken by the Galaxy Evolution Explorer

    Mira is located 350 light-years from Earth in the constellation Cetus, otherwise known as the whale. Coincidentally, Mira

  7. In Vitro Culture of Subanguina picridis in Acroptilon repens Callus, Excised Roots, and Shoot Tissues

    PubMed Central

    Ou, X.; Watson, A. K.

    1992-01-01

    The knapweed nematode Subanguina picridis is a foliar parasite that is of interest as a biological weed control agent of Russian knapweed. Attempts were made to culture the nematode in callus, excised roots and in shoots derived from roots of Russian knapweed. In callus tissues, the nematode developed from second-stage juvenile to adult but failed to reproduce; it developed only to the fourth stage in excised roots. However, S. picridis was successfully cultured in vitro in shoots derived from roots. The nematode induced galls on the leaves, petioles, and shoot apices and developed and reproduced inside the galls. Gibberellic acid increased the development rate of the nematode and promoted the formation of males. This is the first gnotobiotic culture of a nematode used for biological weed control. PMID:19283224

  8. Arabidopsis COLD SHOCK DOMAIN PROTEIN2 is a RNA chaperone that is regulated by cold and developmental signals

    SciTech Connect

    Sasaki, Kentaro; Kim, Myung-Hee; Imai, Ryozo

    2007-12-21

    Bacterial cold shock proteins (CSPs) are RNA chaperones that unwind RNA secondary structures. Arabidopsis COLD SHOCK DOMAIN PROTEIN2 (AtCSP2) contains a domain that is shared with bacterial CSPs. Here we showed that AtCSP2 binds to RNA and unwinds nucleic acid duplex. Heterologous expression of AtCSP2 complemented cold sensitivity of an Escherichia coli csp quadruple mutant, indicating that AtCSP2 function as a RNA chaperone in E. coli. AtCSP2 mRNA and protein levels increased during cold acclimation, but the protein accumulation was most prominent after 10 days of cold treatment. AtCSP2 promoter::GUS transgenic plants revealed that AtCSP2 is expressed only in root and shoot apical regions during vegetative growth but is expressed in reproductive organs such as pollens, ovules and embryos. These data indicated that AtCSP2 is involved in developmental processes as well as cold adaptation. Localization of AtCSP2::GFP in nucleolus and cytoplasm suggested different nuclear and cytosolic RNA targets.

  9. Auxin Depletion from the Leaf Axil Conditions Competence for Axillary Meristem Formation in Arabidopsis and Tomato[W][OPEN

    PubMed Central

    Wang, Quan; Kohlen, Wouter; Rossmann, Susanne; Vernoux, Teva; Theres, Klaus

    2014-01-01

    The enormous variation in architecture of flowering plants is based to a large extent on their ability to form new axes of growth throughout their life span. Secondary growth is initiated from groups of pluripotent cells, called meristems, which are established in the axils of leaves. Such meristems form lateral organs and develop into a side shoot or a flower, depending on the developmental status of the plant and environmental conditions. The phytohormone auxin is well known to play an important role in inhibiting the outgrowth of axillary buds, a phenomenon known as apical dominance. However, the role of auxin in the process of axillary meristem formation is largely unknown. In this study, we show in the model species Arabidopsis thaliana and tomato (Solanum lycopersicum) that auxin is depleted from leaf axils during vegetative development. Disruption of polar auxin transport compromises auxin depletion from the leaf axil and axillary meristem initiation. Ectopic auxin biosynthesis in leaf axils interferes with axillary meristem formation, whereas repression of auxin signaling in polar auxin transport mutants can largely rescue their branching defects. These results strongly suggest that depletion of auxin from leaf axils is a prerequisite for axillary meristem formation during vegetative development. PMID:24850851

  10. Inactivation of Thioredoxin Reductases Reveals a Complex Interplay between Thioredoxin and Glutathione Pathways in Arabidopsis Development[W

    PubMed Central

    Reichheld, Jean-Philippe; Khafif, Mehdi; Riondet, Christophe; Droux, Michel; Bonnard, Géraldine; Meyer, Yves

    2007-01-01

    NADPH-dependent thioredoxin reductases (NTRs) are key regulatory enzymes determining the redox state of the thioredoxin system. The Arabidopsis thaliana genome has two genes coding for NTRs (NTRA and NTRB), both of which encode mitochondrial and cytosolic isoforms. Surprisingly, plants of the ntra ntrb knockout mutant are viable and fertile, although with a wrinkled seed phenotype, slower plant growth, and pollen with reduced fitness. Thus, in contrast with mammals, our data demonstrate that neither cytosolic nor mitochondrial NTRs are essential in plants. Nevertheless, in the double mutant, the cytosolic thioredoxin h3 is only partially oxidized, suggesting an alternative mechanism for thioredoxin reduction. Plant growth in ntra ntrb plants is hypersensitive to buthionine sulfoximine (BSO), a specific inhibitor of glutathione biosynthesis, and thioredoxin h3 is totally oxidized under this treatment. Interestingly, this BSO-mediated growth arrest is fully reversible, suggesting that BSO induces a growth arrest signal but not a toxic accumulation of activated oxygen species. Moreover, crossing ntra ntrb with rootmeristemless1, a mutant blocked in root growth due to strongly reduced glutathione synthesis, led to complete inhibition of both shoot and root growth, indicating that either the NTR or the glutathione pathway is required for postembryonic activity in the apical meristem. PMID:17586656

  11. SQUINT promotes stem cell homeostasis and floral meristem termination in Arabidopsis through APETALA2 and CLAVATA signalling.

    PubMed

    Prunet, Nathanaël; Morel, Patrice; Champelovier, Priscilla; Thierry, Anne-Marie; Negrutiu, Ioan; Jack, Thomas; Trehin, Christophe

    2015-11-01

    Plant meristems harbour stem cells, which allow for the continuous production of new organs. Here, an analysis of the role of SQUINT (SQN) in stem cell dynamics in Arabidopsis is reported. A close examination of sqn mutants reveals defects that are very similar to that of weak clavata (clv) mutants, both in the flower meristem (increased number of floral organs, occasional delay in stem cell termination) and in the shoot apical meristem (meristem and central zone enlargement, occasional fasciation). sqn has a very mild effect in a clv mutant background, suggesting that SQN and the CLV genes act in the same genetic pathway. Accordingly, a loss-of-function allele of SQN strongly rescues the meristem abortion phenotype of plants that overexpress CLV3. Altogether, these data suggest that SQN is necessary for proper CLV signalling. SQN was shown to be required for normal accumulation of various miRNAs, including miR172. One of the targets of miR172, APETALA2 (AP2), antagonizes CLV signalling. The ap2-2 mutation strongly suppresses the meristem phenotypes of sqn, indicating that the effect of SQN on stem cell dynamics is largely, but not fully, mediated by the miR172/AP2 tandem. This study refines understanding of the intricate genetic networks that control both stem cell homeostasis and floral stem cell termination, two processes that are critical for the proper development and fertility of the plant. PMID:26269626

  12. Analysis of knockout mutants reveals non-redundant functions of poly(ADP-ribose)polymerase isoforms in Arabidopsis.

    PubMed

    Pham, Phuong Anh; Wahl, Vanessa; Tohge, Takayuki; de Souza, Laise Rosado; Zhang, Youjun; Do, Phuc Thi; Olas, Justyna J; Stitt, Mark; Araújo, Wagner L; Fernie, Alisdair R

    2015-11-01

    The enzyme poly(ADP-ribose)polymerase (PARP) has a dual function being involved both in the poly(ADP-ribosyl)ation and being a constituent of the NAD(+) salvage pathway. To date most studies, both in plant and non-plant systems, have focused on the signaling role of PARP in poly(ADP-ribosyl)ation rather than any role that can be ascribed to its metabolic function. In order to address this question we here used a combination of expression, transcript and protein localization studies of all three PARP isoforms of Arabidopsis alongside physiological analysis of the corresponding mutants. Our analyses indicated that whilst all isoforms of PARP were localized to the nucleus they are also present in non-nuclear locations with parp1 and parp3 also localised in the cytosol, and parp2 also present in the mitochondria. We next isolated and characterized insertional knockout mutants of all three isoforms confirming a complete knockout in the full length transcript levels of the target genes as well as a reduced total leaf NAD hydrolase activity in the two isoforms (PARP1, PARP2) that are highly expressed in leaves. Physiological evaluation of the mutant lines revealed that they displayed distinctive metabolic and root growth characteristics albeit unaltered leaf morphology under optimal growth conditions. We therefore conclude that the PARP isoforms play non-redundant non-nuclear metabolic roles and that their function is highly important in rapidly growing tissues such as the shoot apical meristem, roots and seeds. PMID:26428915

  13. The Control of Apical Bud Growth and Senescence by Auxin and Gibberellin in Genetic Lines of Peas.

    PubMed Central

    Zhu, Y. X.; Davies, P. J.

    1997-01-01

    Pea (Pisum sativum L.) lines G2 (dwarf) and NGB1769 (tall) (Sn Hr) produce flowers and fruit under long (LD) or short (SD) days, but senesce only under LD. Endogenous gibberellin (GA) levels were inversely correlated with photoperiod (over 9-18 h) and senescence: GA20 was 3-fold and GA1 was 10- to 11-fold higher in flowering SD G2 shoots, and the vegetative tissues within the SD apical bud contained 4-fold higher levels of GA20, as compared with the LD tissues. Prefloral G2 plants under both photoperiods had GA1 and GA20 levels similar to the flowering plants under LD. Levels of indole-3-acetic acid (IAA) were similar in G2 shoots in LD or SD; SD apical bud vegetative tissues had a slightly higher IAA content. Young floral buds from LD plants had twice as much IAA as under SD. In NGB1769 shoots GA1 decreased after flower initiation only under LD, which correlated with the decreased growth potential. We suggest that the higher GA1 content of G2 and NGB1769 plants under SD conditions is responsible for the extended vegetative growth and continued meristematic activity in the shoot apex. This and the increased IAA level of LD floral buds may play a role in the regulation of nutrient partitioning, since more photosynthate partitions of reproductive tissue under LD conditions, and the rate of reproductive development in LD peas is faster than under SD. PMID:12223631

  14. The RON1/FRY1/SAL1 gene is required for leaf morphogenesis and venation patterning in Arabidopsis.

    PubMed

    Robles, Pedro; Fleury, Delphine; Candela, Héctor; Cnops, Gerda; Alonso-Peral, María Magdalena; Anami, Sylvester; Falcone, Andrea; Caldana, Camila; Willmitzer, Lothar; Ponce, María Rosa; Van Lijsebettens, Mieke; Micol, José Luis

    2010-03-01

    To identify genes involved in vascular patterning in Arabidopsis (Arabidopsis thaliana), we screened for abnormal venation patterns in a large collection of leaf shape mutants isolated in our laboratory. The rotunda1-1 (ron1-1) mutant, initially isolated because of its rounded leaves, exhibited an open venation pattern, which resulted from an increased number of free-ending veins. We positionally cloned the RON1 gene and found it to be identical to FRY1/SAL1, which encodes an enzyme with inositol polyphosphate 1-phosphatase and 3' (2'),5'-bisphosphate nucleotidase activities and has not, to our knowledge, previously been related to venation patterning. The ron1-1 mutant and mutants affected in auxin homeostasis share perturbations in venation patterning, lateral root formation, root hair length, shoot branching, and apical dominance. These similarities prompted us to monitor the auxin response using a DR5-GUS auxin-responsive reporter transgene, the expression levels of which were increased in roots and reduced in leaves in the ron1-1 background. To gain insight into the function of RON1/FRY1/SAL1 during vascular development, we generated double mutants for genes involved in vein patterning and found that ron1 synergistically interacts with auxin resistant1 and hemivenata-1 but not with cotyledon vascular pattern1 (cvp1) and cvp2. These results suggest a role for inositol metabolism in the regulation of auxin responses. Microarray analysis of gene expression revealed that several hundred genes are misexpressed in ron1-1, which may explain the pleiotropic phenotype of this mutant. Metabolomic profiling of the ron1-1 mutant revealed changes in the levels of 38 metabolites, including myoinositol and indole-3-acetonitrile, a precursor of auxin. PMID:20044451

  15. Detection of Spatial-Specific Phytochrome Responses Using Targeted Expression of Biliverdin Reductase in Arabidopsis1[OA

    PubMed Central

    Warnasooriya, Sankalpi N.; Montgomery, Beronda L.

    2009-01-01

    To regulate levels of holophytochrome in a spatial-specific manner and investigate the major sites of action of phytochromes during seedling development, we constructed transgenic Arabidopsis (Arabidopsis thaliana) plant lines expressing plastid-targeted mammalian biliverdin IXα reductase (pBVR) under regulatory control of CAB3 and MERI5 promoters. Comparative photobiological and phenotypic analyses indicated that spatial-specific expression of pBVR led to the disruption of distinct subsets of phytochrome-regulated responses for different promoters. pBVR expression in photosynthetic tissues (CAB3∷pBVR lines) had intermediate effects on chlorophyll accumulation, carotenoid production, anthocyanin synthesis, and leaf development responses in white-light conditions. CAB3∷pBVR expression, however, resulted in distinctive phenotypes in far-red (FR) conditions. A number of FR high irradiance responses were disrupted in CAB∷pBVR lines, including FR-dependent inhibition of hypocotyl elongation and stimulation of anthocyanin accumulation. By contrast, preferential expression of pBVR in the shoot apical meristem in MERI5∷pBVR lines resulted in a phytochrome-deficient, leaf development phenotype under short-day growth conditions. These results implicate leaf-localized phytochrome A as having a unique role in regulating FR-mediated hypocotyl elongation and meristem- and/or leaf primordia-localized phytochromes as having a novel role in phytochrome-dependent responses. Taken together, these studies demonstrate the efficacy of selectively inactivating distinct phytochrome-mediated responses by regulated expression of BVR in transgenic plants, a novel means to investigate the sites of phytochrome photoperception and to regulate specifically light-mediated plant growth and development. PMID:18971430

  16. Arabidopsis ROCK1 transports UDP-GlcNAc/UDP-GalNAc and regulates ER protein quality control and cytokinin activity

    PubMed Central

    Niemann, Michael C. E.; Bartrina, Isabel; Ashikov, Angel; Weber, Henriette; Spíchal, Lukáš; Strnad, Miroslav; Strasser, Richard; Bakker, Hans; Schmülling, Thomas; Werner, Tomáš

    2015-01-01

    The formation of glycoconjugates depends on nucleotide sugars, which serve as donor substrates for glycosyltransferases in the lumen of Golgi vesicles and the endoplasmic reticulum (ER). Import of nucleotide sugars from the cytosol is an important prerequisite for these reactions and is mediated by nucleotide sugar transporters. Here, we report the identification of REPRESSOR OF CYTOKININ DEFICIENCY 1 (ROCK1, At5g65000) as an ER-localized facilitator of UDP-N-acetylglucosamine (UDP-GlcNAc) and UDP-N-acetylgalactosamine (UDP-GalNAc) transport in Arabidopsis thaliana. Mutant alleles of ROCK1 suppress phenotypes inferred by a reduced concentration of the plant hormone cytokinin. This suppression is caused by the loss of activity of cytokinin-degrading enzymes, cytokinin oxidases/dehydrogenases (CKXs). Cytokinin plays an essential role in regulating shoot apical meristem (SAM) activity and shoot architecture. We show that rock1 enhances SAM activity and organ formation rate, demonstrating an important role of ROCK1 in regulating the cytokinin signal in the meristematic cells through modulating activity of CKX proteins. Intriguingly, genetic and molecular analysis indicated that N-glycosylation of CKX1 was not affected by the lack of ROCK1-mediated supply of UDP-GlcNAc. In contrast, we show that CKX1 stability is regulated in a proteasome-dependent manner and that ROCK1 regulates the CKX1 level. The increased unfolded protein response in rock1 plants and suppression of phenotypes caused by the defective brassinosteroid receptor bri1-9 strongly suggest that the ROCK1 activity is an important part of the ER quality control system, which determines the fate of aberrant proteins in the secretory pathway. PMID:25535363

  17. Investigating the Molecular Mechanism of TSO1 Function in Arabidopsis cell division and meristem development

    SciTech Connect

    Zhongchi Liu

    2004-10-01

    Unlike animals, plants are constantly exposed to environmental mutagens including ultraviolet light and reactive oxygen species. Further, plant cells are totipotent with highly plastic developmental programs. An understanding of molecular mechanisms underlying the ability of plants to monitor and repair its DNA and to eliminate damaged cells are of great importance. Previously we have identified two genes, TSO1 and TSO2, from a flowering plant Arabidopsis thaliana. Mutations in these two genes cause callus-like flowers, fasciated shoot apical meristems, and abnormal cell division, indicating that TSO1 and TSO2 may encode important cell cycle regulators. Previous funding from DOE led to the molecular cloning of TSO1, which was shown to encode a novel nuclear protein with two CXC domains suspected to bind DNA. This DOE grant has allowed us to characterize and isolate TSO2 that encodes the small subunit of the ribonucleotide reductase (RNR). RNR comprises two large subunits (R1) an d two small subunits (R2), catalyzes a rate-limiting step in the production of deoxyribonucleotides needed for DNA replication and repair. Previous studies in yeast and mammals indicated that defective RNR often led to cell cycle arrest, growth retardation and p53-dependent apoptosis while abnormally elevated RNR activities led to higher mutation rates. Subsequently, we identified two additional R2 genes, R2A and R2B in the Arabidopsis genome. Using reverse genetics, mutations in R2A and R2B were isolated, and double and triple mutants among the three R2 genes (TSO2, R2A and R2B) were constructed and analyzed. We showed that Arabidopsis tso2 mutants, with reduced dNTP levels, were more sensitive to UV-C. While r2a or r2b single mutants did not exhibit any phenotypes, tso2 r2b double mutants were embryonic lethal and tso2 r2a double mutants were seedling lethal indicating redundant functions among the three R2 genes. Furthermore, tso2 r2a double mutants exhibited increased DNA dam age

  18. Apical root resorption in orthodontically treated adults.

    PubMed

    Baumrind, S; Korn, E L; Boyd, R L

    1996-09-01

    This study analyzed the relationship in orthodontically treated adults between upper central incisor displacement measured on lateral cephalograms and apical root resorption measured on anterior periapical x-ray films. A multiple linear regression examined incisor displacements in four directions (retraction, advancement, intrusion, and extrusion) as independent variables, attempting to account for observed differences in the dependent variable, resorption. Mean apical resorption was 1.36 mm (sd +/- 1.46, n = 73). Mean horizontal displacement of the apex was -0.83 mm (sd +/- 1.74, n = 67); mean vertical displacement was 0.19 mm (sd +/- 1.48, n = 67). The regression coefficients for the intercept and for retraction were highly significant; those for extrusion, intrusion, and advancement were not. At the 95% confidence level, an average of 0.99 mm (se = +/- 0.34) of resorption was implied in the absence of root displacement and an average of 0.49 mm (se = +/- 0.14) of resorption was implied per millimeter of retraction. R2 for all four directional displacement variables (DDVs) taken together was only 0.20, which implied that only a relatively small portion of the observed apical resorption could be accounted for by tooth displacement alone. In a secondary set of univariate analyses, the associations between apical resorption and each of 14 additional treatment-related variables were examined. Only Gender, Elapsed Time, and Total Apical Displacement displayed statistically significant associations with apical resorption. Additional multiple regressions were then performed in which the data for each of these three statistically significant variables were considered separately, with the data for the four directional displacement variables. The addition of information on Elapsed Time or Total Apical Displacement did not explain a significant additional portion of the variability in apical resorption. On the other hand, the addition of information on Gender to the

  19. Sodium Influx and Accumulation in Arabidopsis1

    PubMed Central

    Essah, Pauline A.; Davenport, Romola; Tester, Mark

    2003-01-01

    Arabidopsis is frequently used as a genetic model in plant salt tolerance studies, however, its physiological responses to salinity remain poorly characterized. This study presents a characterization of initial Na+ entry and the effects of Ca2+ on plant growth and net Na+ accumulation in saline conditions. Unidirectional Na+ influx was measured carefully using very short influx times in roots of 12-d-old seedlings. Influx showed three components with distinct sensitivities to Ca2+, diethylpyrocarbonate, and osmotic pretreatment. Pharmacological agents and known mutants were used to test the contribution of different transport pathways to Na+ uptake. Influx was stimulated by 4-aminobutyric acid and glutamic acid; was inhibited by flufenamate, quinine, and cGMP; and was insensitive to modulators of K+ and Ca2+ channels. Influx did not differ from wild type in akt1 and hkt1 insertional mutants. These data suggested that influx was mediated by several different types of nonselective cation channels. Na+ accumulation in plants grown in 50 mm NaCl was strongly reduced by increasing Ca2+ activity (from 0.05-3.0 mm), and plant survival was improved. However, plant biomass was not affected by shoot Na+ concentration, suggesting that in Arabidopsis Na+ toxicity is not dependent on shoot Na+ accumulation. These data suggest that Arabidopsis is a good model for investigation of Na+ transport, but may be of limited utility as a model for the study of Na+ toxicity. PMID:12970496

  20. Microbiology and treatment of acute apical abscesses.

    PubMed

    Siqueira, José F; Rôças, Isabela N

    2013-04-01

    Acute apical abscess is the most common form of dental abscess and is caused by infection of the root canal of the tooth. It is usually localized intraorally, but in some cases the apical abscess may spread and result in severe complications or even mortality. The reasons why dental root canal infections can become symptomatic and evolve to severe spreading and sometimes life-threatening abscesses remain elusive. Studies using culture and advanced molecular microbiology methods for microbial identification in apical abscesses have demonstrated a multispecies community conspicuously dominated by anaerobic bacteria. Species/phylotypes commonly found in these infections belong to the genera Fusobacterium, Parvimonas, Prevotella, Porphyromonas, Dialister, Streptococcus, and Treponema. Advances in DNA sequencing technologies and computational biology have substantially enhanced the knowledge of the microbiota associated with acute apical abscesses and shed some light on the etiopathogeny of this disease. Species richness and abundance and the resulting network of interactions among community members may affect the collective pathogenicity and contribute to the development of acute infections. Disease modifiers, including transient or permanent host-related factors, may also influence the development and severity of acute abscesses. This review focuses on the current evidence about the etiology and treatment of acute apical abscesses and how the process is influenced by host-related factors and proposes future directions in research, diagnosis, and therapeutic approaches to deal with this disease. PMID:23554416

  1. Microbiology and Treatment of Acute Apical Abscesses

    PubMed Central

    Rôças, Isabela N.

    2013-01-01

    SUMMARY Acute apical abscess is the most common form of dental abscess and is caused by infection of the root canal of the tooth. It is usually localized intraorally, but in some cases the apical abscess may spread and result in severe complications or even mortality. The reasons why dental root canal infections can become symptomatic and evolve to severe spreading and sometimes life-threatening abscesses remain elusive. Studies using culture and advanced molecular microbiology methods for microbial identification in apical abscesses have demonstrated a multispecies community conspicuously dominated by anaerobic bacteria. Species/phylotypes commonly found in these infections belong to the genera Fusobacterium, Parvimonas, Prevotella, Porphyromonas, Dialister, Streptococcus, and Treponema. Advances in DNA sequencing technologies and computational biology have substantially enhanced the knowledge of the microbiota associated with acute apical abscesses and shed some light on the etiopathogeny of this disease. Species richness and abundance and the resulting network of interactions among community members may affect the collective pathogenicity and contribute to the development of acute infections. Disease modifiers, including transient or permanent host-related factors, may also influence the development and severity of acute abscesses. This review focuses on the current evidence about the etiology and treatment of acute apical abscesses and how the process is influenced by host-related factors and proposes future directions in research, diagnosis, and therapeutic approaches to deal with this disease. PMID:23554416

  2. Shoot-to-Root Mobile Transcription Factor HY5 Coordinates Plant Carbon and Nitrogen Acquisition.

    PubMed

    Chen, Xiangbin; Yao, Qinfang; Gao, Xiuhua; Jiang, Caifu; Harberd, Nicholas P; Fu, Xiangdong

    2016-03-01

    Coordination of shoot photosynthetic carbon fixation with root inorganic nitrogen uptake optimizes plant performance in a fluctuating environment [1]. However, the molecular basis of this long-distance shoot-root coordination is little understood. Here we show that Arabidopsis ELONGATED HYPOCOTYL5 (HY5), a bZIP transcription factor that regulates growth in response to light [2, 3], is a shoot-to-root mobile signal that mediates light promotion of root growth and nitrate uptake. Shoot-derived HY5 auto-activates root HY5 and also promotes root nitrate uptake by activating NRT2.1, a gene encoding a high-affinity nitrate transporter [4]. In the shoot, HY5 promotes carbon assimilation and translocation, whereas in the root, HY5 activation of NRT2.1 expression and nitrate uptake is potentiated by increased carbon photoassimilate (sucrose) levels. We further show that HY5 function is fluence-rate modulated and enables homeostatic maintenance of carbon-nitrogen balance in different light environments. Thus, mobile HY5 coordinates light-responsive carbon and nitrogen metabolism, and hence shoot and root growth, in a whole-organismal response to ambient light fluctuations. PMID:26877080

  3. Genetic analysis of the role of amyloplasts in shoot gravisensing

    NASA Astrophysics Data System (ADS)

    Tasaka, M.; Morita, M.

    Plant can change the growth direction after sensing the gravity orientation This response calls gravitropism and the initial step is the gravisensing We have isolated many Arabidopsis mutants shoot gravitropism sgr with reduced or no gravitropic response in inflorescence stems The analysis of sgr1 and sgr7 revealed that endoderm cells in the inflorescence stems were gravisensing sites zig zigzag sgr4 and sgr3 showed no or reduced gravitropism in shoot respectively and their amyloplasts thought to be statoliths did not sedimented to the orientation of gravity in the endoderm cells ZIG encoded a SNARE AtVTI11 and SGR3 encoded other SNARE AtVAM3 These two SNAREs made a complex in the shoot endoderm cells suggesting that the vesicle transport from trans-Golgi network TGN to prevacuolar compartment PVC and or vacuole was involved in the amyloplasts localization and movement The analysis to visualize amyloplasts and vacuolar membrane in living endoderm cells supported that the vacuole function was important for the amyloplasts movement Recently we have isolated many suppressor mutants of zig One of them named zig suppressor zip 1 had a point mutation in the gene encoded other SNARE of AtVTI12 This protein is a homologous to ZIG AtVTI11 and these two proteins have partially redundant functions Although wild type At VTI 12 could not rescued zig mutated AtVTI12 protein ZIP1 could almost completely play the part of ZIG In zigzip1 amyloplasts in endoderm cells sedimented normally and the shoots showed normal gravitropic response The other

  4. Three ancient hormonal cues co-ordinate shoot branching in a moss.

    PubMed

    Coudert, Yoan; Palubicki, Wojtek; Ljung, Karin; Novak, Ondrej; Leyser, Ottoline; Harrison, C Jill

    2015-01-01

    Shoot branching is a primary contributor to plant architecture, evolving independently in flowering plant sporophytes and moss gametophytes. Mechanistic understanding of branching is largely limited to flowering plants such as Arabidopsis, which have a recent evolutionary origin. We show that in gametophytic shoots of Physcomitrella, lateral branches arise by re-specification of epidermal cells into branch initials. A simple model co-ordinating the activity of leafy shoot tips can account for branching patterns, and three known and ancient hormonal regulators of sporophytic branching interact to generate the branching pattern- auxin, cytokinin and strigolactone. The mode of auxin transport required in branch patterning is a key divergence point from known sporophytic pathways. Although PIN-mediated basipetal auxin transport regulates branching patterns in flowering plants, this is not so in Physcomitrella, where bi-directional transport is required to generate realistic branching patterns. Experiments with callose synthesis inhibitors suggest plasmodesmal connectivity as a potential mechanism for transport. PMID:25806686

  5. Trouble Shooting Checklist-A.

    ERIC Educational Resources Information Center

    Manning, Brad A.

    The Trouble Shooting Checklist-A (TSC-A) is a predictive instrument to aid the educational change agent in defining variables within institutions or organizations which are concerned with adopting modules in deciding whether or not an institution is suited for a particular innovation. These five dimensions comprise the major scales: Organization…

  6. Trouble Shooting Checklist-B.

    ERIC Educational Resources Information Center

    Manning, Brad A.

    The Trouble Shooting Checklist-B (TSC-B) is a predictive instrument to aid the educational change agent in defining variables within institutions or organizations which are concerned with adopting a psychological assessment battery with some form of personal counseling orientation in deciding whether or not an institution is suited for a…

  7. Shootings Revive Debates on Security

    ERIC Educational Resources Information Center

    Shah, Nirvi

    2013-01-01

    By nearly all accounts, the staff and students at Sandy Hook Elementary School did everything right on Dec. 14--and with the security measures they took before that day--when a young man armed with powerful weapons blasted his way into the school. But the deadliest K-12 school shooting in American history, a day that President Barack Obama has…

  8. School Shootings and Critical Pedagogy

    ERIC Educational Resources Information Center

    Schiller, Juliet

    2013-01-01

    What has been left out of studying school violence and shootings is a comprehensive look at the culture that creates violence and the lack of support for those deemed "different" in an educational setting that promotes and rewards competition. If parents, teachers, and other adults associated with children were teaching the values of…

  9. School Shootings as Organizational Deviance.

    ERIC Educational Resources Information Center

    Fox, Cybelle; Harding, David J.

    2005-01-01

    This article argues that rampage school shootings in American public schools can be understood as instances of organizational deviance, which occurs when events created by or in organizations do not conform to an organization's goals or expectations and produce unanticipated and harmful outcomes. Drawing on data from qualitative case studies of…

  10. School Shootings in Policy Spotlight

    ERIC Educational Resources Information Center

    Maxwell, Lesli A.

    2006-01-01

    The three school shootings that left a principal and six students dead in less than a week have sparked a barrage of pledges from national and state political leaders to tighten campus security. School safety experts urged caution against overreacting to the horrific, but rare, incidents in rural schools in Colorado, Pennsylvania, and Wisconsin.…

  11. Apoplastic Diffusion Barriers in Arabidopsis

    PubMed Central

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  12. Control of Arabidopsis leaf morphogenesis through regulation of the YABBY and KNOX families of transcription factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The patterning of initiating organs along specific axes of polarity is critical for the proper development of all higher organisms. Plant lateral organs, such as leaves, are derived from the shoot apical meristems located at the growing tips. After initiation, the leaf primordia of species such as A...

  13. 50 CFR 20.23 - Shooting hours.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... PLANTS (CONTINUED) MIGRATORY BIRD HUNTING Taking § 20.23 Shooting hours. No person shall take migratory game birds except during the hours open to shooting as prescribed in subpart K of this part and...

  14. Tragedy and the meaning of school shootings.

    PubMed

    Warnick, Bryan R; Johnson, Benjamin A; Rocha, Samuel

    2010-01-01

    School shootings are traumatic events that cause a community to question itself, its values, and its educational systems. In this article Bryan Warnick, Benjamin Johnson, and Samuel Rocha explore the meanings of school shootings by examining three recent books on school violence. Topics that grow out of these books include (1) how school shootings might be seen as ceremonial rituals, (2) how schools come to be seen as appropriate places for shootings, and (3) how advice to educators relating to school shootings might change the practice of teaching. The authors present various ways of understanding school shootings that may eventually prove helpful, but they also highlight the problems, tensions, and contradictions associated with each position. In the end, the authors argue, the circumstances surrounding school shootings demonstrate the need for the "tragic sense" in education. This need for the tragic sense, while manifest in many different areas of schooling, is exemplified most clearly in targeted school shootings. PMID:20662173

  15. Clonal analysis of corn plant development. I. The development of the tassel and the ear shoot

    SciTech Connect

    Johri, M.M.; Coe, E.H. Jr.

    1983-05-01

    The development of the tassel and the ear shoot has been investigated in corn (Zea mays L.). X irradiation of dry kernels and seedlings heterozygous for anthocyanin markers or for factors altering tassel and ear morphology results in the formation of clones (sectors) from cells of the apical meristem. Most tassels develop from 4 +/- 1 cells of the mature embryo. The expression of ramosa-1, tunicate, tassel seed-6, and vestigial is cell autonomous in the tassel. These genes act late in development and modify the developmental fate or decision of an individual clone and not of the whole group of cells producing a tassel. The ear shoot develops from lineages of one to three cells derived each from the L-I (outmost cell layer) and L-II (second cell layer) of the apical meristem. Typically the clones start in the ear shoot (in the husks and possibly in the cob), extend upward in an internode, continue along the margin of the leaf sheath or leaf blade at the node above, and terminate in this or the next higher leaf. The separation of lineages for ear shoot and internode occurs in the period around 13 days after sowing. The analysis of clonal boundaries shows that a small number of embryonic cells become isolated in their developmental capacity. This commitment process appears to be analogous to the process of compartmentation in the imaginal disks of fruit flies. The extent of proliferation of individual cells within a group of highly flexible and any particular clone does not generate a specific part of a tassel or an ear shoot. There must be cellular communication between various clones so that the overall size and morphology of an organ remain normal and more or less fixed. Thus the process of development in plants is also highly regulative in nature and shares many features in common with development in fruit flies.

  16. Shoot growth in aseptically cultivated daylily and haplopappus plantlets after a 5-day spaceflight

    NASA Technical Reports Server (NTRS)

    Levine, H. G.; Krikorian, A. D.

    1992-01-01

    Plantlets of daylily (Hemerocallis cv. Autumn Blaze) regenerated from cell suspensions, and 4 clonal populations of Haplopappus gracilis were aseptically cultivated aboard the Shuttle "Discovery" during a 5-day mission within NASA's Plant Growth Unit (PGU) apparatus. Daylily was selected as a representative herbaceous perennial monocotyledon and the haplopappus clones represented an annual dicotyledon. The latter included 4 strains with different physiological and morphological characteristics: two aseptic seedling clones (each generated from a single seedling) and two tissue culture-derived lines. Mean daily growth rates for the primary shoots of all plantlets averaged 4.13 mm day-1 (SD = 2.20) for the flight experiment and 4.68 mm day-1 (SD = 2.59) for the ground control. Comparable growth rates calculated by summing both the primary and secondary shoots for all plantlets were 5.94 mm day-1 (SD = 2.89) for the flight experiment and 6.38 mm day-1 (SD = 3.71) for the control. Statistically significant differences existed between: (1) flight vs control primary shoot growth (the controls growing more than plantlets subjected to spaceflight conditions), (2) the different populations (the daylily gaining more shoot material than any of the haplopappus populations and the haplopappus seedling clones outperforming the tissue culture-derived haplopappus lines), and (3) the individual Plant Growth Chambers contained within the PGU. The data suggest that some spaceflight-associated factor(s) increased the tendency for primary shoot apices to degrade or senesce, resulting in the release of apical dominance and permitting the emergence of axillary branches, which subsequently partially compensated for the reduced primary axis growth. In addition to spaceflight-associated factors, the physiologically diverse nature of the experimental material as well as environmental heterogeneities within the culture apparatus contributed to the variation in growth results. The findings

  17. Training Visual Control in Wheelchair Basketball Shooting

    ERIC Educational Resources Information Center

    Oudejans, Raoul R. D.; Heubers, Sjoerd; Ruitenbeek, Jean-Rene J. A. C.; Janssen, Thomas W. J.

    2012-01-01

    We examined the effects of visual control training on expert wheelchair basketball shooting, a skill more difficult than in regular basketball, as players shoot from a seated position to the same rim height. The training consisted of shooting with a visual constraint that forced participants to use target information as late as possible.…

  18. 50 CFR 20.23 - Shooting hours.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 9 2014-10-01 2014-10-01 false Shooting hours. 20.23 Section 20.23... PLANTS (CONTINUED) MIGRATORY BIRD HUNTING Taking § 20.23 Shooting hours. No person shall take migratory game birds except during the hours open to shooting as prescribed in subpart K of this part and...

  19. 50 CFR 20.23 - Shooting hours.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 9 2013-10-01 2013-10-01 false Shooting hours. 20.23 Section 20.23... PLANTS (CONTINUED) MIGRATORY BIRD HUNTING Taking § 20.23 Shooting hours. No person shall take migratory game birds except during the hours open to shooting as prescribed in subpart K of this part and...

  20. 50 CFR 20.23 - Shooting hours.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 6 2010-10-01 2010-10-01 false Shooting hours. 20.23 Section 20.23... PLANTS (CONTINUED) MIGRATORY BIRD HUNTING Taking § 20.23 Shooting hours. No person shall take migratory game birds except during the hours open to shooting as prescribed in subpart K of this part and...

  1. 50 CFR 20.23 - Shooting hours.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 9 2012-10-01 2012-10-01 false Shooting hours. 20.23 Section 20.23... PLANTS (CONTINUED) MIGRATORY BIRD HUNTING Taking § 20.23 Shooting hours. No person shall take migratory game birds except during the hours open to shooting as prescribed in subpart K of this part and...

  2. Shoot regeneration and embryogenesis in lily shoot tips cryopreserved by droplet vitrification

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shoot regeneration and embryogenesis were, for the first time, achieved directly in shoot tips of Lilium Oriental hybrid ‘Siberia’ following cryopreservation by droplet-vitrification. Shoot tips (2 mm in length) including 2-3 leaf primordia were excised from 4-week-old adventitious shoots directly r...

  3. Pathogenesis of Apical Periodontitis: a Literature Review

    PubMed Central

    Lodiene, Greta; Maciulskiene, Vita

    2011-01-01

    ABSTRACT Objectives This review article discusses the host response in apical periodontitis with the main focus on cytokines, produced under this pathological condition and contributing to the degradation of periradicular tissues. The pace of research in this field has greatly accelerated in the last decade. Here we provide an analysis of studies published in this area during this period. Material and methods Literature was selected through a search of PubMed electronic database. The keywords used for search were pathogenesis of apical periodontitis cytokines, periapical granuloma cytokines, inflammatory infiltrate apical periodontitis. The search was restricted to English language articles, published from 1999 to December 2010. Additionally, a manual search in the cytokine production, cytokine functions and periapical tissue destruction in the journals and books was performed. Results In total, 97 literature sources were obtained and reviewed. The topics covered in this article include cellular composition of an inflammatory infiltrate in the periapical lesions, mechanisms of the formation of the innate and specific immune response. Studies which investigated cytokine secretion and functions were identified and cellular and molecular interactions in the course of apical periodontitis described. Conclusions The abundance and interactions of various inflammatory and anti-inflammatory molecules can influence and alter the state and progression of the disease. Therefore, periapical inflammatory response offers a model, suited for the study of many facets of pathogenesis, biocompatibility of different materials to periapical tissues and development of novel treatment methods, based on the regulation of cytokines expression PMID:24421998

  4. The Impact of Apical Patency in the Success of Endodontic Treatment of Necrotic Teeth with Apical Periodontitis: A Brief Review

    PubMed Central

    Machado, Ricardo; Ferrari, Carlos Henrique; Back, Eduardo; Comparin, Daniel; Tomazinho, Luiz Fernando; Vansan, Luiz Pascoal

    2016-01-01

    Accumulation of soft tissue or dentinal remnants in the apical region is a common event that can cause blockage of root canals. This event can be avoided if apical patency is performed during the root canal shaping procedures. However, there is no consensus on the role of apical patency in relation to the success of endodontic treatment of necrotic teeth with apical periodontitis. Therefore, the purpose of this paper was to conduct a brief review on the role of apical patency in guaranteeing the success of endodontic treatments of necrotic teeth with apical periodontitis considering two other key points; the root canal anatomy and microbiology. PMID:26843880

  5. Assessment of military shooting noise.

    PubMed

    Boegli, Hans; Wunderli, Jean Marc; Brink, Mark

    2008-05-01

    The assessment of the impact of noise exposure on the population is a fundamental step in noise abatement. It includes the establishing of an exposure-response relationship and the setting of an impact threshold that specifies the protection level for the population and triggers eventually mitigating measures to reduce noise exposure. In Switzerland, the impact thresholds should be set so that, in the light of current scientific knowledge and experience, noise exposure below these thresholds will not seriously disturb the well-being of the population. For most current noise sources such as roads, railways and airports there already exist impact thresholds as part of the noise abatement legislation. Yet, no impact thresholds for military shooting grounds have been specified so far. Therefore a study was carried out in order to assess the impact of military noise exposure. The research included the calculation of noise exposure of eight military shooting grounds ranging from small infantry shooting ranges to expanded artillery and tank training facilities and a survey at over 1000 residents in the neighbourhood of these installations. Preliminary results suggest that although the responses of the population to military noise are rather dispersed, data should be sufficiently consistent to establish an exposure-response relationship. PMID:18532285

  6. Multiple pathways regulate shoot branching

    PubMed Central

    Rameau, Catherine; Bertheloot, Jessica; Leduc, Nathalie; Andrieu, Bruno; Foucher, Fabrice; Sakr, Soulaiman

    2015-01-01

    Shoot branching patterns result from the spatio-temporal regulation of axillary bud outgrowth. Numerous endogenous, developmental and environmental factors are integrated at the bud and plant levels to determine numbers of growing shoots. Multiple pathways that converge to common integrators are most probably involved. We propose several pathways involving not only the classical hormones auxin, cytokinins and strigolactones, but also other signals with a strong influence on shoot branching such as gibberellins, sugars or molecular actors of plant phase transition. We also deal with recent findings about the molecular mechanisms and the pathway involved in the response to shade as an example of an environmental signal controlling branching. We propose the TEOSINTE BRANCHED1, CYCLOIDEA, PCF transcription factor TB1/BRC1 and the polar auxin transport stream in the stem as possible integrators of these pathways. We finally discuss how modeling can help to represent this highly dynamic system by articulating knowledges and hypothesis and calculating the phenotype properties they imply. PMID:25628627

  7. Inactivation of Plasma Membrane–Localized CDPK-RELATED KINASE5 Decelerates PIN2 Exocytosis and Root Gravitropic Response in Arabidopsis[C][W

    PubMed Central

    Rigó, Gábor; Ayaydin, Ferhan; Tietz, Olaf; Zsigmond, Laura; Kovács, Hajnalka; Páy, Anikó; Salchert, Klaus; Darula, Zsuzsanna; Medzihradszky, Katalin F.; Szabados, László; Palme, Klaus; Koncz, Csaba; Cséplő, Ágnes

    2013-01-01

    CRK5 is a member of the Arabidopsis thaliana Ca2+/calmodulin-dependent kinase-related kinase family. Here, we show that inactivation of CRK5 inhibits primary root elongation and delays gravitropic bending of shoots and roots. Reduced activity of the auxin-induced DR5–green fluorescent protein reporter suggests that auxin is depleted from crk5 root tips. However, no tip collapse is observed and the transcription of genes for auxin biosynthesis, AUXIN TRANSPORTER/AUXIN TRANSPORTER-LIKE PROTEIN (AUX/LAX) auxin influx, and PIN-FORMED (PIN) efflux carriers is unaffected by the crk5 mutation. Whereas AUX1, PIN1, PIN3, PIN4, and PIN7 display normal localization, PIN2 is depleted from apical membranes of epidermal cells and shows basal to apical relocalization in the cortex of the crk5 root transition zone. This, together with an increase in the number of crk5 lateral root primordia, suggests facilitated auxin efflux through the cortex toward the elongation zone. CRK5 is a plasma membrane–associated kinase that forms U-shaped patterns facing outer lateral walls of epidermis and cortex cells. Brefeldin inhibition of exocytosis stimulates CRK5 internalization into brefeldin bodies. CRK5 phosphorylates the hydrophilic loop of PIN2 in vitro, and PIN2 shows accelerated accumulation in brefeldin bodies in the crk5 mutant. Delayed gravitropic response of the crk5 mutant thus likely reflects defective phosphorylation of PIN2 and deceleration of its brefeldin-sensitive membrane recycling. PMID:23673979

  8. Organ specificity in the plant circadian system is explained by different light inputs to the shoot and root clocks.

    PubMed

    Bordage, Simon; Sullivan, Stuart; Laird, Janet; Millar, Andrew J; Nimmo, Hugh G

    2016-10-01

    Circadian clocks allow the temporal compartmentalization of biological processes. In Arabidopsis, circadian rhythms display organ specificity but the underlying molecular causes have not been identified. We investigated the mechanisms responsible for the similarities and differences between the clocks of mature shoots and roots in constant conditions and in light : dark cycles. We developed an imaging system to monitor clock gene expression in shoots and light- or dark-grown roots, modified a recent mathematical model of the Arabidopsis clock and used this to simulate our new data. We showed that the shoot and root circadian clocks have different rhythmic properties (period and amplitude) and respond differently to light quality. The root clock was entrained by direct exposure to low-intensity light, even in antiphase to the illumination of shoots. Differences between the clocks were more pronounced in conditions where light was present than in constant darkness, and persisted in the presence of sucrose. We simulated the data successfully by modifying those parameters of a clock model that are related to light inputs. We conclude that differences and similarities between the shoot and root clocks can largely be explained by organ-specific light inputs. This provides mechanistic insight into the developing field of organ-specific clocks. PMID:27240972

  9. [Daily temperature gradients and processes of organogenesis in apical meristem of Cucumis sativus L].

    PubMed

    Markovskaia, E F; Sysoeva, M I; Vasilevskaia, N V

    2007-01-01

    We studied the influence of daily temperature gradients on organogenesis in apical and axil shoot meristems at different developmental stages in Cucumis sativus L. The level of organogenic activity of meristems was determined according to the number of leaf primordia on the main and lateral shoots, number of 2nd order shoots, and rudiments of flowers of different levels of development. At the studied ontogenetic stages (mesotrophic seedling or juvenile state), plants were grown under the controlled conditions: photoperiod 12 h, light intensity 100 Wt/m2, range of mean daily temperatures 20 ... 30 degrees C, and daily temperature gradients -20 ... +20 degrees C. After the temperature treatment, some plants were returned to the optimal, for growth and development, conditions for two weeks (aftereffect). Three types of organogenic activity of meristems in response to the influence of variable daily temperatures were described: stimulation, inhibition, or absence of effect. The phenomenon of stimulation includes two subtypes: optimization, when a maximum effect, observed at other constant temperatures, was attained under the influence of variable temperatures and maximization, when maximum values markedly exceeded those at constant temperatures. The patterns described are preserved on the whole in the aftereffect of daily temperatures. PMID:17352290

  10. Natural genetic variation in Arabidopsis for responsiveness to plant growth-promoting rhizobacteria.

    PubMed

    Wintermans, Paul C A; Bakker, Peter A H M; Pieterse, Corné M J

    2016-04-01

    The plant growth-promoting rhizobacterium (PGPR) Pseudomonas simiae WCS417r stimulates lateral root formation and increases shoot growth in Arabidopsis thaliana (Arabidopsis). These plant growth-stimulating effects are partly caused by volatile organic compounds (VOCs) produced by the bacterium. Here, we performed a genome-wide association (GWA) study on natural genetic variation in Arabidopsis for the ability to profit from rhizobacteria-mediated plant growth-promotion. To this end, 302 Arabidopsis accessions were tested for root architecture characteristics and shoot fresh weight in response to exposure to WCS417r. Although virtually all Arabidopsis accessions tested responded positively to WCS417r, there was a large variation between accessions in the increase in shoot fresh weight, the extra number of lateral roots formed, and the effect on primary root length. Correlation analyses revealed that the bacterially-mediated increase in shoot fresh weight is related to alterations in root architecture. GWA mapping for WCS417r-stimulated changes in root and shoot growth characteristics revealed 10 genetic loci highly associated with the responsiveness of Arabidopsis to the plant growth-promoting activity of WCS417r. Several of the underlying candidate genes have been implicated in important plant growth-related processes. These results demonstrate that plants possess natural genetic variation for the capacity to profit from the plant growth-promoting function of a beneficial rhizobacterium in their rhizosphere. This knowledge is a promising starting point for sustainable breeding strategies for future crops that are better able to maximize profitable functions from their root microbiome. PMID:26830772

  11. BLADE-ON-PETIOLE1 Coordinates Organ Determinacy and Axial Polarity in Arabidopsis by Directly Activating ASYMMETRIC LEAVES2[C][W

    PubMed Central

    Jun, Ji Hyung; Ha, Chan Man; Fletcher, Jennifer C.

    2010-01-01

    Continuous organ formation is a hallmark of plant development that requires organ-specific gene activity to establish determinacy and axial patterning, yet the molecular mechanisms that coordinate these events remain poorly understood. Here, we show that the organ-specific BTB-POZ domain proteins BLADE-ON-PETIOLE1 (BOP1) and BOP2 function as transcriptional activators during Arabidopsis thaliana leaf formation. We identify as a direct target of BOP1 induction the ASYMMETRIC LEAVES2 (AS2) gene, which promotes leaf cell fate specification and adaxial polarity. We find that BOP1 associates with the AS2 promoter and that BOP1 and BOP2 are required for AS2 activation specifically in the proximal, adaxial region of the leaf, demonstrating a role for the BOP proteins as proximal-distal as well as adaxial-abaxial patterning determinants. Furthermore, repression of BOP1 and BOP2 expression by the indeterminacy-promoting KNOX gene SHOOTMERISTEMLESS is critical to establish a functional embryonic shoot apical meristem. Our data indicate that direct activation of AS2 transcription by BOP1 and BOP2 is vital for generating the conditions for KNOX repression at the leaf base and may represent a conserved mechanism for coordinating leaf morphogenesis with patterning along the adaxial-abaxial and the proximal-distal axes. PMID:20118228

  12. Reduced naphthylphthalamic acid binding in the tir3 mutant of Arabidopsis is associated with a reduction in polar auxin transport and diverse morphological defects

    NASA Technical Reports Server (NTRS)

    Ruegger, M.; Dewey, E.; Hobbie, L.; Brown, D.; Bernasconi, P.; Turner, J.; Muday, G.; Estelle, M.

    1997-01-01

    Polar auxin transport plays a key role in the regulation of plant growth and development. To identify genes involved in this process, we have developed a genetic procedure to screen for mutants of Arabidopsis that are altered in their response to auxin transport inhibitors. We recovered a total of 16 independent mutants that defined seven genes, called TRANSPORT INHIBITOR RESPONSE (TIR) genes. Recessive mutations in one of these genes, TIR3, result in altered responses to transport inhibitors, a reduction in polar auxin transport, and a variety of morphological defects that can be ascribed to changes in indole-3-acetic acid distribution. Most dramatically, tir3 seedlings are strongly deficient in lateral root production, a process that is known to depend on polar auxin transport from the shoot into the root. In addition, tir3 plants display a reduction in apical dominance as well as decreased elongation of siliques, pedicels, roots, and the inflorescence. Biochemical studies indicate that tir3 plants have a reduced number of N-1-naphthylphthalamic (NPA) binding sites, suggesting that the TIR3 gene is required for expression, localization, or stabilization of the NPA binding protein (NBP). Alternatively, the TIR3 gene may encode the NBP. Because the tir3 mutants have a substantial defect in NPA binding, their phenotype provides genetic evidence for a role for the NBP in plant growth and development.

  13. A genetic link between epigenetic repressor AS1-AS2 and a putative small subunit processome in leaf polarity establishment of Arabidopsis.

    PubMed

    Matsumura, Yoko; Ohbayashi, Iwai; Takahashi, Hiro; Kojima, Shoko; Ishibashi, Nanako; Keta, Sumie; Nakagawa, Ayami; Hayashi, Rika; Saéz-Vásquez, Julio; Echeverria, Manuel; Sugiyama, Munetaka; Nakamura, Kenzo; Machida, Chiyoko; Machida, Yasunori

    2016-01-01

    Although the DEAD-box RNA helicase family is ubiquitous in eukaryotes, its developmental role remains unelucidated. Here, we report that cooperative action between the Arabidopsis nucleolar protein RH10, an ortholog of human DEAD-box RNA helicase DDX47, and the epigenetic repressor complex of ASYMMETRIC-LEAVES1 (AS1) and AS2 (AS1-AS2) is critical to repress abaxial (ventral) genes ETT/ARF3 and ARF4, which leads to adaxial (dorsal) development in leaf primordia at shoot apices. Double mutations of rh10-1 and as2 (or as1) synergistically up-regulated the abaxial genes, which generated abaxialized filamentous leaves with loss of the adaxial domain. DDX47 is part of the small subunit processome (SSUP) that mediates rRNA biogenesis. In rh10-1 we found various defects in SSUP-related events, such as: accumulation of 35S/33S rRNA precursors; reduction in the 18S/25S ratio; and nucleolar hypertrophy. Double mutants of as2 with mutations of genes that encode other candidate SSUP-related components such as nucleolin and putative rRNA methyltransferase exhibited similar synergistic defects caused by up-regulation of ETT/ARF3 and ARF4 These results suggest a tight link between putative SSUP and AS1-AS2 in repression of the abaxial-determining genes for cell fate decisions for adaxial development. PMID:27334696

  14. Reduced naphthylphthalamic acid binding in the tir3 mutant of Arabidopsis is associated with a reduction in polar auxin transport and diverse morphological defects.

    PubMed Central

    Ruegger, M; Dewey, E; Hobbie, L; Brown, D; Bernasconi, P; Turner, J; Muday, G; Estelle, M

    1997-01-01

    Polar auxin transport plays a key role in the regulation of plant growth and development. To identify genes involved in this process, we have developed a genetic procedure to screen for mutants of Arabidopsis that are altered in their response to auxin transport inhibitors. We recovered a total of 16 independent mutants that defined seven genes, called TRANSPORT INHIBITOR RESPONSE (TIR) genes. Recessive mutations in one of these genes, TIR3, result in altered responses to transport inhibitors, a reduction in polar auxin transport, and a variety of morphological defects that can be ascribed to changes in indole-3-acetic acid distribution. Most dramatically, tir3 seedlings are strongly deficient in lateral root production, a process that is known to depend on polar auxin transport from the shoot into the root. In addition, tir3 plants display a reduction in apical dominance as well as decreased elongation of siliques, pedicels, roots, and the inflorescence. Biochemical studies indicate that tir3 plants have a reduced number of N-1-naphthylphthalamic (NPA) binding sites, suggesting that the TIR3 gene is required for expression, localization, or stabilization of the NPA binding protein (NBP). Alternatively, the TIR3 gene may encode the NBP. Because the tir3 mutants have a substantial defect in NPA binding, their phenotype provides genetic evidence for a role for the NBP in plant growth and development. PMID:9165751

  15. A genetic link between epigenetic repressor AS1-AS2 and a putative small subunit processome in leaf polarity establishment of Arabidopsis

    PubMed Central

    Matsumura, Yoko; Ohbayashi, Iwai; Takahashi, Hiro; Kojima, Shoko; Ishibashi, Nanako; Keta, Sumie; Nakagawa, Ayami; Hayashi, Rika; Saéz-Vásquez, Julio; Echeverria, Manuel; Sugiyama, Munetaka; Nakamura, Kenzo; Machida, Chiyoko

    2016-01-01

    ABSTRACT Although the DEAD-box RNA helicase family is ubiquitous in eukaryotes, its developmental role remains unelucidated. Here, we report that cooperative action between the Arabidopsis nucleolar protein RH10, an ortholog of human DEAD-box RNA helicase DDX47, and the epigenetic repressor complex of ASYMMETRIC-LEAVES1 (AS1) and AS2 (AS1-AS2) is critical to repress abaxial (ventral) genes ETT/ARF3 and ARF4, which leads to adaxial (dorsal) development in leaf primordia at shoot apices. Double mutations of rh10-1 and as2 (or as1) synergistically up-regulated the abaxial genes, which generated abaxialized filamentous leaves with loss of the adaxial domain. DDX47 is part of the small subunit processome (SSUP) that mediates rRNA biogenesis. In rh10-1 we found various defects in SSUP-related events, such as: accumulation of 35S/33S rRNA precursors; reduction in the 18S/25S ratio; and nucleolar hypertrophy. Double mutants of as2 with mutations of genes that encode other candidate SSUP-related components such as nucleolin and putative rRNA methyltransferase exhibited similar synergistic defects caused by up-regulation of ETT/ARF3 and ARF4. These results suggest a tight link between putative SSUP and AS1-AS2 in repression of the abaxial-determining genes for cell fate decisions for adaxial development. PMID:27334696

  16. Gibberellin Promotes Shoot Branching in the Perennial Woody Plant Jatropha curcas.

    PubMed

    Ni, Jun; Gao, Congcong; Chen, Mao-Sheng; Pan, Bang-Zhen; Ye, Kaiqin; Xu, Zeng-Fu

    2015-08-01

    Strigolactone (SL), auxin and cytokinin (CK) interact to regulate shoot branching. CK has long been considered to be the only key phytohormone to promote lateral bud outgrowth. Here we report that gibberellin also acts as a positive regulator in the control of shoot branching in the woody plant Jatropha curcas. We show that gibberellin and CK synergistically promote lateral bud outgrowth, and that both hormones influence the expression of putative branching regulators, J. curcas BRANCHED1 and BRANCHED2, which are key transcription factors maintaining bud dormancy. Moreover, treatment with paclobutrazol, an inhibitor of de novo gibberellin biosynthesis, significantly reduced the promotion of bud outgrowth by CK, suggesting that gibberellin is required for CK-mediated axillary bud outgrowth. In addition, SL, a plant hormone involved in the repression of shoot branching, acted antagonistically to both gibberellin and CK in the control of lateral bud outgrowth. Consistent with this, the expression of JcMAX2, a J. curcas homolog of Arabidopsis MORE AXILLARY GROWTH 2 encoding an F-box protein in the SL signaling pathway, was repressed by gibberellin and CK treatment. We also provide physiological evidence that gibberellin also induces shoot branching in many other trees, such as papaya, indicating that a more complicated regulatory network occurs in the control of shoot branching in some perennial woody plants. PMID:26076970

  17. Shoot Feeding as a Nutrient Acquisition Strategy in Free-Living Psylloids

    PubMed Central

    Steinbauer, Martin J.

    2013-01-01

    Shoot feeding by sucking insects is accepted as an adaptation to feeding where plant nutrients are most concentrated and/or of higher quality. Psylloids are an important hemipteran taxon, most of which are free-living and comprise many shoot feeding species, whose nutritional ecology has been largely ignored. I conducted a longitudinal study of Ctenarytaina eucalypti (Maskell) and C. bipartita Burckhardt et al. (Aphalaridae) feeding on eucalypts to document how within-plant (ontogenic) variation in nutritional quality, in particular of free amino acids, determines host suitability and hence the distribution and abundance of nymphs. Nymphs were most abundant within developing apical buds but were not more abundant on branchlets of greater vigour (indicated by rate of extension). Nymphs could be found up to two (C. bipartita) to three (C. eucalypti) alternate leaf pairs distant from apical buds but infrequently and in low numbers; they were never found on older, fully expanded leaves. The position of a leaf on a branchlet (indicative of age) determined its nutritional quality. Younger leaves had higher water contents, lower chlorophyll contents and differed in amino acid (essential and non-essential) composition compared to older leaves. The abundance of C. eucalypti nymphs on expanding leaves and in buds was positively correlated with the concentrations of methionine, valine and threonine in E. globulus leaves at the same or comparable position on a branchlet. The abundance of C. bipartita nymphs was positively correlated with foliar leucine concentrations. Shoot feeding by these two psyllids facilitates access to more concentrated, better quality plant nutrients but may not entirely explain the adaptive significance of their behaviour. The humid microclimate created by the architecture of the hosts’ apical buds protects eggs and nymphs from desiccation and is suggested to have had a significant influence on the evolution of host utilisation strategies of psyllids

  18. The RON1/FRY1/SAL1 Gene Is Required for Leaf Morphogenesis and Venation Patterning in Arabidopsis1[W][OA

    PubMed Central

    Robles, Pedro; Fleury, Delphine; Candela, Héctor; Cnops, Gerda; Alonso-Peral, María Magdalena; Anami, Sylvester; Falcone, Andrea; Caldana, Camila; Willmitzer, Lothar; Ponce, María Rosa; Van Lijsebettens, Mieke; Micol, José Luis

    2010-01-01

    To identify genes involved in vascular patterning in Arabidopsis (Arabidopsis thaliana), we screened for abnormal venation patterns in a large collection of leaf shape mutants isolated in our laboratory. The rotunda1-1 (ron1-1) mutant, initially isolated because of its rounded leaves, exhibited an open venation pattern, which resulted from an increased number of free-ending veins. We positionally cloned the RON1 gene and found it to be identical to FRY1/SAL1, which encodes an enzyme with inositol polyphosphate 1-phosphatase and 3′ (2′),5′-bisphosphate nucleotidase activities and has not, to our knowledge, previously been related to venation patterning. The ron1-1 mutant and mutants affected in auxin homeostasis share perturbations in venation patterning, lateral root formation, root hair length, shoot branching, and apical dominance. These similarities prompted us to monitor the auxin response using a DR5-GUS auxin-responsive reporter transgene, the expression levels of which were increased in roots and reduced in leaves in the ron1-1 background. To gain insight into the function of RON1/FRY1/SAL1 during vascular development, we generated double mutants for genes involved in vein patterning and found that ron1 synergistically interacts with auxin resistant1 and hemivenata-1 but not with cotyledon vascular pattern1 (cvp1) and cvp2. These results suggest a role for inositol metabolism in the regulation of auxin responses. Microarray analysis of gene expression revealed that several hundred genes are misexpressed in ron1-1, which may explain the pleiotropic phenotype of this mutant. Metabolomic profiling of the ron1-1 mutant revealed changes in the levels of 38 metabolites, including myoinositol and indole-3-acetonitrile, a precursor of auxin. PMID:20044451

  19. Down-regulation of multiple CDK inhibitor ICK/KRP genes promotes cell proliferation, callus induction and plant regeneration in Arabidopsis

    PubMed Central

    Cheng, Yan; Liu, Han; Cao, Ling; Wang, Sheng; Li, Yongpeng; Zhang, Yuanyuan; Jiang, Wei; Zhou, Yongming; Wang, Hong

    2015-01-01

    The ICK/KRP cyclin-dependent kinase (CDK) inhibitors are important plant cell cycle regulators sharing only limited similarity with the metazoan CIP/KIP family of CDK inhibitors. Information is still limited regarding the specific functions of different ICK/KRP genes in planta. We have shown previously that down-regulation of multiple CDK inhibitor ICK/KRP genes up-regulates the E2F pathway and increases cell proliferation, and organ and seed sizes in Arabidopsis. In this study, we observed that the quintuple ick1/2/5/6/7 mutant had more cells in the cortical layer of the root apical meristem (RAM) than the wild type (Wt) while its RAM length was similar to that of the Wt, suggesting a faster cell cycle rate in the quintuple mutant. We further investigated the effects of down-regulating ICK genes on tissue culture responses. The cotyledon explants of ick1/2/5/6/7 could form callus efficiently in the absence of cytokinin and also required a lower concentration of 2,4-D for callus induction compared to the Wt plants, suggesting increased competence for callus induction in the mutant. In addition, the quintuple ick mutant showed enhanced abilities to regenerate shoots and roots, suggesting that increased competence to enter the cell cycle in the quintuple mutant might make it possible for more cells to become proliferative and be utilized to form shoots or roots. These findings indicate that CDK activity is a major factor underlying callus induction and increased cell proliferation can enhance in vitro organogenesis. PMID:26528298

  20. [The technology of apical infection control].

    PubMed

    Qing, Yu; Yang, Yang; Bei, Chang

    2014-10-01

    Root canal therapy is the most efficient way to treat pulptitis and periapical inflammation, which can clear infections of root canal systems, fill the root canal firmly, and avoid reinfection. However, the variations in root canal morphology and complexity of infection confer difficulty in thoroughly eliminating microorganisms and their by-products in the root canal system, especially in the root apex area (including the top one-third of the root canal and periapical tissue), which is described as the hardest area to clean during endodontic treatment. Infection is difficult to remove entirely because the apex area is hard to approach using dental instruments and because of the existence of special morphological structures, such as apical ramification, intercanal anastomoses, and lateral branch of root canal. This review gives a brief introduction of the characteristics and difficulties of apical infection and knowledge on how to control such infections, including root apex preparation, irrigation and disinfection, and root canal filling. PMID:25490815

  1. Computational identification of 69 retroposons in Arabidopsis.

    PubMed

    Zhang, Yujun; Wu, Yongrui; Liu, Yilei; Han, Bin

    2005-06-01

    Retroposition is a shot-gun strategy of the genome to achieve evolutionary diversities by mixing and matching coding sequences with novel regulatory elements. We have identified 69 retroposons in the Arabidopsis (Arabidopsis thaliana) genome by a computational approach. Most of them were derivatives of mature mRNAs, and 20 genes contained relics of the reverse transcription process, such as truncations, deletions, and extra sequence additions. Of them, 22 are processed pseudogenes, and 52 genes are likely to be actively transcribed, especially in tissues from apical meristems (roots and flowers). Functional compositions of these retroposon parental genes imply that not the mRNA itself but its expression in gamete cells defines a suitable template for retroposition. The presence/absence patterns of retroposons can be used as cladistic markers for biogeographic research. Effects of human and the Mediterranean Pleistocene refugia in Arabidopsis biogeographic distributions were revealed based on two recent retroposons (At1g61410 and At5g52090). An evolutionary rate of new gene creation by retroposition was calculated as 0.6 genes per million years. Retroposons can also be used as molecular fossils of the parental gene expressions in ancient time. Extensions of 3' untranslated regions for those expressed parental genes are revealed as a possible trend of plant transcriptome evolution. In addition, we reported the first plant functional chimeric gene that adapts to intercompartmental transport by capturing two additional exons after retroposition. PMID:15923328

  2. Inflammatory Myofibroblastic Tumor Mimicking Apical Periodontitis.

    PubMed

    Adachi, Makoto; Kiho, Kazuki; Sekine, Genta; Ohta, Takahisa; Matsubara, Makoto; Yoshida, Takakazu; Katsumata, Akitoshi; Tanuma, Jun-ichi; Sumitomo, Shinichiro

    2015-12-01

    Inflammatory myofibroblastic tumors (IMTs) are rare. IMTs of the head and neck occur in all age groups, from neonates to old age, with the highest incidence occurring in childhood and early adulthood. An IMT has been defined as a histologically distinctive lesion of uncertain behavior. This article describes an unusual case of IMT mimicking apical periodontitis in the mandible of a 42-year-old man. At first presentation, the patient showed spontaneous pain and percussion pain at teeth #28 to 30, which continued after initial endodontic treatment. Panoramic radiography revealed a radiolucent lesion at the site. Cone-beam computed tomographic imaging showed osteolytic lesions, suggesting an aggressive neoplasm requiring incisional biopsy. Histopathological examination indicated an IMT. The lesion was removed en bloc under general anesthesia, and the patient manifested no clinical evidence of recurrence for 24 months. Lesions of nonendodontic origin should be included in the differential diagnosis of apical periodontitis. Every available diagnostic tool should be used to confirm the diagnosis. Cone-beam computed tomographic imaging is very helpful for differential diagnosis in IMTs mimicking apical periodontitis. PMID:26602450

  3. [School shooting in statu nascendi].

    PubMed

    Knecht, Thomas

    2012-01-01

    In the last few years, amok-like killings and especially so-called "school shootings" have received a great deal of public attention both in the Old and the New world. Meanwhile, criminal psychological research has gained a thorough insight into this dangerous development in young people. Thus, the possibility to assess the concrete threat of such a multiple killing before it is carried out has been considerably improved, as many prognostic criteria have been worked out in the meantime. The case report presented shows that it is possible to exercise a favourable influence on this critical negative trend. PMID:22448465

  4. Ammonium stress in Arabidopsis: signaling, genetic loci, and physiological targets.

    PubMed

    Li, Baohai; Li, Guangjie; Kronzucker, Herbert J; Baluška, František; Shi, Weiming

    2014-02-01

    Ammonium (NH4(+)) toxicity is a significant ecological and agricultural issue, and an important phenomenon in cell biology. As a result of increasing soil nitrogen input and atmospheric deposition, plants have to deal with unprecedented NH4(+) stress from sources below and above ground. In this review, we describe recent advances in elucidating the signaling pathways and identifying the main physiological targets and genetic loci involved in the effects of NH4(+) stress in the roots and shoots of Arabidopsis thaliana. We outline new experimental approaches that are being used to study NH4(+) toxicity in Arabidopsis and propose an integrated view of behavior and signaling in response to NH4(+) stress in the Arabidopsis system. PMID:24126103

  5. Final Scientific/Technical Report for DOE Award No. DE-FG02-03ER15426: Role of Arabidopsis PINHEAD gene in meristem function

    SciTech Connect

    Dr. M. Kathryn Barton

    2011-11-29

    The shoot apical meristems of land plants are small mounds of hundreds of cells located at the tips of branches. It is from these small clusters of cells that essentially all above ground plant biomass and therefore much of our energy supply originates. Several key genes have been discovered that are necessary for cells in the shoot apical meristem to take on stem cell properties. The goal of this project is to understand how the synthesis and accumulation of the mRNAs and proteins encoded by these genes is controlled. A thorough understanding of the molecules that control the growth of shoot apical meristems in plants will help us to manipulate food, fiber and biofuel crops to better feed, clothe and provide energy for humans.

  6. Amyloplast movement and gravityperception in Arabidopsis endoderm

    NASA Astrophysics Data System (ADS)

    Tasaka, M.; Saito, T.; Morita, M. T.

    Gravitropism of higher plant is a growth response regulating the orientation of organs elongation, which includes four sequential steps, the perception of gravistimulus, transduction of the physical stimulus to chemical signal, transmission of the signal, and differential cell elongation depending on the signal. To elucidate the molecular mechanism of these steps, we have isolated a number of Arabidopsis mutants with abnormal shoot gravitropic response. zig (zigzag)/sgr4(shoot gravitropism 4) shows little gravitropism in their shoots. Besides, their inflorescence stems elongate in a zigzag-fashion to bend at each node. ZIG encodes a SNARE, AtVTI11. sgr3 with reduced gravitropic response in inflorescence stems had a missense mutation in other SNARE, AtVAM3. These two SNAREs make a complex in the shoot endoderm cells that are gravity-sensing cells, suggesting that the vesicle transport from trans-Golgi network (TGN) to prevacuolar compartment (PVC) and/or vacuole is involved in gravitropism. Abnormal vesicular/vacuolar structures were observed in several tissues of both mutants. Moreover, SGR2 encodes phospholipase A1-like protein that resides in the vacuolar membrane. Endodermis-specific expression of these genes could complement gravitropism in each mutant. In addition, amyloplasts thought to be statoliths localized abnormally in their endoderm cells. These results strongly suggest that formation and function of vacuole in the endoderm cells are important for amyloplasts sedimentation, which is involved in the early process of shoot gravitropism. To reveal this, we constructed vertical stage microscope system to visualize the behavior of amyloplasts and vacuolar membrane in living endodermal cells. We hope to discuss the mechanism of gravity perception after showing their movements.

  7. The Ferroportin Metal Efflux Proteins Function in Iron and Cobalt Homeostasis in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Relatively little is known about how metals such as iron are effluxed from cells, a necessary step for transport from the root to the shoot. Ferroportin is the sole iron efflux transporter in animals, and there are two closely related orthologs in Arabidopsis, FPN1 and FPN2. FPN1 localizes to the pl...

  8. A Trihelix DNA Binding Protein Counterbalances Hypoxia-Responsive Transcriptional Activation in Arabidopsis

    PubMed Central

    Licausi, Francesco; Kosmacz, Monika; Oosumi, Teruko; van Dongen, Joost T.; Bailey-Serres, Julia; Perata, Pierdomenico

    2014-01-01

    Transcriptional activation in response to hypoxia in plants is orchestrated by ethylene-responsive factor group VII (ERF-VII) transcription factors, which are stable during hypoxia but destabilized during normoxia through their targeting to the N-end rule pathway of selective proteolysis. Whereas the conditionally expressed ERF-VII genes enable effective flooding survival strategies in rice, the constitutive accumulation of N-end-rule–insensitive versions of the Arabidopsis thaliana ERF-VII factor RAP2.12 is maladaptive. This suggests that transcriptional activation under hypoxia that leads to anaerobic metabolism may need to be fine-tuned. However, it is presently unknown whether a counterbalance of RAP2.12 exists. Genome-wide transcriptome analyses identified an uncharacterized trihelix transcription factor gene, which we named HYPOXIA RESPONSE ATTENUATOR1 (HRA1), as highly up-regulated by hypoxia. HRA1 counteracts the induction of core low oxygen-responsive genes and transcriptional activation of hypoxia-responsive promoters by RAP2.12. By yeast-two-hybrid assays and chromatin immunoprecipitation we demonstrated that HRA1 interacts with the RAP2.12 protein but with only a few genomic DNA regions from hypoxia-regulated genes, indicating that HRA1 modulates RAP2.12 through protein–protein interaction. Comparison of the low oxygen response of tissues characterized by different levels of metabolic hypoxia (i.e., the shoot apical zone versus mature rosette leaves) revealed that the antagonistic interplay between RAP2.12 and HRA1 enables a flexible response to fluctuating hypoxia and is of importance to stress survival. In Arabidopsis, an effective low oxygen-sensing response requires RAP2.12 stabilization followed by HRA1 induction to modulate the extent of the anaerobic response by negative feedback regulation of RAP2.12. This mechanism is crucial for plant survival under suboptimal oxygenation conditions. The discovery of the feedback loop regulating the oxygen

  9. A trihelix DNA binding protein counterbalances hypoxia-responsive transcriptional activation in Arabidopsis.

    PubMed

    Giuntoli, Beatrice; Lee, Seung Cho; Licausi, Francesco; Kosmacz, Monika; Oosumi, Teruko; van Dongen, Joost T; Bailey-Serres, Julia; Perata, Pierdomenico

    2014-09-01

    Transcriptional activation in response to hypoxia in plants is orchestrated by ethylene-responsive factor group VII (ERF-VII) transcription factors, which are stable during hypoxia but destabilized during normoxia through their targeting to the N-end rule pathway of selective proteolysis. Whereas the conditionally expressed ERF-VII genes enable effective flooding survival strategies in rice, the constitutive accumulation of N-end-rule-insensitive versions of the Arabidopsis thaliana ERF-VII factor RAP2.12 is maladaptive. This suggests that transcriptional activation under hypoxia that leads to anaerobic metabolism may need to be fine-tuned. However, it is presently unknown whether a counterbalance of RAP2.12 exists. Genome-wide transcriptome analyses identified an uncharacterized trihelix transcription factor gene, which we named HYPOXIA RESPONSE ATTENUATOR1 (HRA1), as highly up-regulated by hypoxia. HRA1 counteracts the induction of core low oxygen-responsive genes and transcriptional activation of hypoxia-responsive promoters by RAP2.12. By yeast-two-hybrid assays and chromatin immunoprecipitation we demonstrated that HRA1 interacts with the RAP2.12 protein but with only a few genomic DNA regions from hypoxia-regulated genes, indicating that HRA1 modulates RAP2.12 through protein-protein interaction. Comparison of the low oxygen response of tissues characterized by different levels of metabolic hypoxia (i.e., the shoot apical zone versus mature rosette leaves) revealed that the antagonistic interplay between RAP2.12 and HRA1 enables a flexible response to fluctuating hypoxia and is of importance to stress survival. In Arabidopsis, an effective low oxygen-sensing response requires RAP2.12 stabilization followed by HRA1 induction to modulate the extent of the anaerobic response by negative feedback regulation of RAP2.12. This mechanism is crucial for plant survival under suboptimal oxygenation conditions. The discovery of the feedback loop regulating the oxygen

  10. Minimal Apical Enlargement for Penetration of Irrigants to the Apical Third of Root Canal System: A Scanning Electron Microscope Study

    PubMed Central

    Srikanth, P; Krishna, Amaravadi Gopi; Srinivas, Siva; Reddy, E Sujayeendranatha; Battu, Someshwar; Aravelli, Swathi

    2015-01-01

    Background: The aim of this study was to determine minimal apical enlargement for irrigant penetration into apical third of root canal system using scanning electron microscope (SEM). Materials and Methods: Distobuccal canals of 40 freshly extracted human maxillary first molar teeth were instrumented using crown-down technique. The teeth were divided into four test groups according to size of their master apical file (MAF) (#20, #25, #30, #35 0.06% taper), and two control groups. After final irrigation, removal of debris and smear layer from the apical third of root canals was determined under a SEM. Data was analyzed using Kruskal–Wallis and Mann–Whitney tests. Results: Smear layer removal in apical third for MAF size #30 was comparable with that of the control group (size #40). Conclusion: Minimal apical enlargement for penetration of irrigants to the apical third of root canal system is #30 size. PMID:26124608

  11. Early flower development in Arabidopsis.

    PubMed Central

    Smyth, D R; Bowman, J L; Meyerowitz, E M

    1990-01-01

    The early development of the flower of Arabidopsis thaliana is described from initiation until the opening of the bud. The morphogenesis, growth rate, and surface structure of floral organs were recorded in detail using scanning electron microscopy. Flower development has been divided into 12 stages using a series of landmark events. Stage 1 begins with the initiation of a floral buttress on the flank of the apical meristem. Stage 2 commences when the flower primordium becomes separate from the meristem. Sepal primordia then arise (stage 3) and grow to overlie the primordium (stage 4). Petal and stamen primordia appear next (stage 5) and are soon enclosed by the sepals (stage 6). During stage 6, petal primordia grow slowly, whereas stamen primordia enlarge more rapidly. Stage 7 begins when the medial stamens become stalked. These soon develop locules (stage 8). A long stage 9 then commences with the petal primordia becoming stalked. During this stage all organs lengthen rapidly. This includes the gynoecium, which commences growth as an open-ended tube during stage 6. When the petals reach the length of the lateral stamens, stage 10 begins. Stigmatic papillae appear soon after (stage 11), and the petals rapidly reach the height of the medial stamens (stage 12). This final stage ends when the 1-millimeter-long bud opens. Under our growing conditions 1.9 buds were initiated per day on average, and they took 13.25 days to progress through the 12 stages from initiation until opening. PMID:2152125

  12. Cryopreservation of in vitro grown shoot tips

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter in Plant Cell Culture, Development and Biotechnology describes student laboratory exercises for cryopreservation of the growing shoot tips of plants in liquid nitrogen. It includes two exercises involving step by step protocols for use with shoot tips. Vitrification (fast freezing) an...

  13. Lockheed P-80A Shooting Star

    NASA Technical Reports Server (NTRS)

    1946-01-01

    Lockheed P-80A Shooting Star: The Lockheed P-80A Shooting Star was America's first fully operation jet fighter. This all-yellow example arrived at Langley in November 1946. The P-80 was used for air speed calibration and development of a tuned vibration damper.

  14. A shooting approach to suboptimal control

    NASA Technical Reports Server (NTRS)

    Hull, David G.; Sheen, Jyh-Jong

    1991-01-01

    The shooting method is used to solve the suboptimal control problem where the control history is assumed to be piecewise linear. Suboptimal solutions can be obtained without difficulty and can lead to accurate approximate controls and good starting multipliers for the regular shooting method by increasing the number of nodes. Optimal planar launch trajectories are presented for the advanced launch system.

  15. Tragedy and the Meaning of School Shootings

    ERIC Educational Resources Information Center

    Warnick, Bryan R.; Johnson, Benjamin A.; Rocha, Samuel

    2010-01-01

    School shootings are traumatic events that cause a community to question itself, its values, and its educational systems. In this article Bryan Warnick, Benjamin Johnson, and Samuel Rocha explore the meanings of school shootings by examining three recent books on school violence. Topics that grow out of these books include (1) how school shootings…

  16. 76 FR 77375 - Airworthiness Directives; Apical Industries, Inc., (Apical) Emergency Float Kits

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-13

    ... Register on December 7, 2010 (75 FR 75934). That action proposed to require, for certain model helicopters... Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 3. Will not affect intrastate aviation...-038-AD; Amendment 39-16877; AD 2011-25-01] RIN 2120-AA64 Airworthiness Directives; Apical...

  17. 75 FR 75934 - Airworthiness Directives; Apical Industries Inc. (Apical) Emergency Float Kits

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-07

    ... FR 19477-78). Examining the Docket You may examine the docket that contains the proposed AD, any... ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3... Federal Aviation Administration 14 CFR Part 39 RIN 2120-AA64 Airworthiness Directives; Apical...

  18. Apical hypertrophic cardiomyopathy presenting as acute coronary syndrome.

    PubMed

    Abdin, Amr; Eitel, Ingo; de Waha, Suzanne; Thiele, Holger

    2016-06-01

    Apical hypertrophic cardiomyopathy is a rare variant of hypertrophic cardiomyopathy. It is characterized by a local hypertrophy of the apical segments and displays typical electrocardiographic and imaging patterns. The clinical manifestations are variable and range from an asymptomatic course to sudden cardiac death. The most frequent symptom is chest pain and thus apical hypertrophic cardiomyopathy can mimic the symptoms and repolarization disturbances indicative of acute coronary syndrome. PMID:26628684

  19. Training visual control in wheelchair basketball shooting.

    PubMed

    Oudejans, Raôul R D; Heubers, Sjoerd; Ruitenbeek, Jean-René J A C; Janssen, Thomas W J

    2012-09-01

    We examined the effects of visual control training on expert wheelchair basketball shooting, a skill more difficult than in regular basketball, as players shoot from a seated position to the same rim height. The training consisted of shooting with a visual constraint that forced participants to use target information as late as possible. Participants drove under a large screen that initially blocked the basket. As soon as they saw the basket they shot. When training with the screen, shooting percentages increased. We conclude that visual control training is an effective method to improve wheelchair basketball shooting. The findings support the idea that perceptual-motor learning can be enhanced by manipulating relevant constraints in the training environment, even for expert athletes. PMID:22978196

  20. Arabidopsis hybrid speciation processes

    PubMed Central

    Schmickl, Roswitha; Koch, Marcus A.

    2011-01-01

    The genus Arabidopsis provides a unique opportunity to study fundamental biological questions in plant sciences using the diploid model species Arabidopsis thaliana and Arabidopsis lyrata. However, only a few studies have focused on introgression and hybrid speciation in Arabidopsis, although polyploidy is a common phenomenon within this genus. More recently, there is growing evidence of significant gene flow between the various Arabidopsis species. So far, we know Arabidopsis suecica and Arabidopsis kamchatica as fully stabilized allopolyploid species. Both species evolved during Pleistocene glaciation and deglaciation cycles in Fennoscandinavia and the amphi-Beringian region, respectively. These hybrid studies were conducted either on a phylogeographic scale or reconstructed experimentally in the laboratory. In our study we focus at a regional and population level. Our research area is located in the foothills of the eastern Austrian Alps, where two Arabidopsis species, Arabidopsis arenosa and A. lyrata ssp. petraea, are sympatrically distributed. Our hypothesis of genetic introgression, migration, and adaptation to the changing environment during the Pleistocene has been confirmed: We observed significant, mainly unidirectional gene flow between the two species, which has given rise to the tetraploid A. lyrata. This cytotype was able to escape from the narrow ecological niche occupied by diploid A. lyrata ssp. petraea on limestone outcrops by migrating northward into siliceous areas, leaving behind a trail of genetic differentiation. PMID:21825128

  1. Apical ballooning syndrome following exercise treadmill testing

    PubMed Central

    Irwin, RB; Mamas, MA; El-Omar, M

    2011-01-01

    Transient left ventricular apical ballooning syndrome is an increasingly recognized cause of acute coronary syndrome, particularly in postmenopausal women, and is the subject of increasing interest to both clinicians and researchers. Emotional and physical stressors are often implicated in its development and, while excess sympathetic drive appears to act as a primary trigger, the exact mechanism remains controversial. The clinical presentation is characterized by transient, often severe, left ventricular dysfunction affecting the mid and apical myocardium. By definition, no significant coronary artery lesions are present, although this may not be recognized at initial presentation. While recovery of function with evidence of limited myocardial necrosis is common, significant complications may manifest in the acute phase. A case involving an elderly patient who developed classical features of the syndrome following an exercise treadmill test is presented. To the authors’ knowledge, the present case is the only such report that meets the recently proposed diagnostic criteria. The present case serves to highlight a rare but important complication of exercise testing in an elderly patient. Recent large systematic reviews have provided valuable insights into the clinical features of this condition. The current article examines the data from these studies and others to provide a comprehensive clinical overview. PMID:21747667

  2. Apical leakage of four endodontic sealers.

    PubMed

    Pommel, Ludovic; About, Imad; Pashley, David; Camps, Jean

    2003-03-01

    The purpose of this study was to evaluate the sealing properties of four root canal sealers. Forty-eight maxillary central incisors were instrumented with Profile rotary instruments. They were randomly divided into four groups (n = 12) and filled using lateral condensation with one of the four sealers: Sealapex, Pulp Canal Sealer, AH 26, and Ketac-Endo. The apical leakage was measured with a fluid filtration method and expressed as L s(-1) KPa(-1). The teeth filled with Sealapex displayed a higher apical leakage (8.42 +/- 4.2 10(-11) L s(-1) KPa(-1)) than those filled with AH 26 (2.10 +/- 1.39 10(-11) L s(-1) KPa(-1)), Pulp Canal Sealer (0.17 +/- 0.09 10(-11) L s(-1) KPa(-1)) or Ketac-Endo (0.32 +/- 0.24 10(-1) L s(-1) KPa(-1)) (p < 0.01). No statistically significant difference was found among AH 26, Pulp Canal Sealer, and Ketac-Endo. No correlation was found between the sealing efficiency of the four sealers and their adhesive properties recorded in a previous study. PMID:12669883

  3. Assessing the response of indigenous loquat cultivar Mardan to phytohormones for in vitro shoot proliferation and rooting*

    PubMed Central

    Abbasi, Nadeem Akhtar; Pervaiz, Tariq; Hafiz, Ishfaq Ahmed; Yaseen, Mehwish; Hussain, Azhar

    2013-01-01

    In vitro cultures of loquat cultivar Mardan were established using shoot apices after treating with NaOCl (5%, 7%, 10%, 12%, 14% (v/v)) for 12 min and HgCl2 (0.01%, 0.05%, 0.10%, 0.20%, 0.25% (w/v)) for 2 min. A maximum survival rate of 70% was recorded after surface sterilization with 10% NaOCl. Caulogenic response was assessed on Murashige and Skoog (MS) medium fortified with assorted combinations of the cytokinins, benzylaminopurine (BAP), kinetin, and N6-(2-isopentyl)adenine (2iP). Treatment of BAP 1.5 mg/L combined with 2iP 9.0 mg/L and kinetin 1.5 mg/L was found to be optimum for shoot morphogenesis in terms of the number and subsequent growth of shoots, while the highest shoot length was yielded by the combination of BAP 0.5 mg/L, kinetin 0.5 mg/L, and 2iP 3 mg/L. Higher levels of cytokinins induced callogenesis, vitrification and stunted growth to some extent. For rhizogenesis, uniform sized micro-shoots were excised and transferred to half-strength MS medium containing auxins. The best rooting expression was observed with naphthaleneacetic acid (NAA) 1 mg/L combined with indole-3-butyric acid (IBA) 2 mg/L and paclobutrazol (PBZ) 1 mg/L. PMID:24009197

  4. A gain-of-function mutation in IAA8 alters Arabidopsis floral organ development by change of jasmonic acid level.

    PubMed

    Wang, Jing; Yan, Da-Wei; Yuan, Ting-Ting; Gao, Xiang; Lu, Ying-Tang

    2013-05-01

    Auxin regulates a variety of physiological processes via its downstream factors included Aux/IAAs. In this study, one of these Aux/IAAs, IAA8 is shown to play its role in Arabidopsis development with transgenic plants expressing GFP-mIAA8 under the control of IAA8 promoter, in which IAA8 protein was mutated by changing Pro170 to Leu170 in its conserved domain II. These transgenic dwarfed plants had more lateral branches, short primary inflorescence stems, decreased shoot apical dominance, curled leaves and abnormal flower organs (short petal and stamen, and bent stigmas). Further experiments revealed that IAA8::GFP-mIAA8 plants functioned as gain-of-function mutation to increase GFP-mIAA8 amount probably by stabilizing IAA8 protein against proteasome-mediated protein degradation with IAA8::GFP-IAA8 plants as control. The searching for its downstream factors indicated its interaction with both ARF6 and ARF8, suggesting that IAA8 may involve in flower organ development. This was further evidenced by analyzing the expression of jasmonic acid (JA) biosynthetic genes and JA levels because ARF6 and ARF8 are required for normal JA production. These results indicated that in IAA8::GFP-mIAA8 plants, JA biosynthetic genes including DAD1 (AT2G44810), AOS (AT5G42650) and ORP3 (AT2G06050) were dramatically down-regulated and JA level in the flowers was reduced to 70 % of that in wild-type. Furthermore, exogenous JA application can partially rescue short petal and stamen observed IAA8::GFP-mIAA8 plants. Thus, IAA8 plays its role in floral organ development by changes in JA levels probably via its interaction with ARF6/8 proteins. PMID:23483289

  5. Photoperiod-induced changes in gibberellin metabolism in relation to apical growth and senescence in genetic lines of peas (Pisum sativum L.).

    PubMed

    Proebsting, W M; Davies, P J; Marx, G A

    1978-01-01

    In an early-flowering line of pea (G2) apical senescence occurs only in long days (LD), while growth in short days (SD) is indeterminate. In SD, G2 plants are known to produce a graft-transmissible substance which delays apical senescence in related lines that are photoperiod-insensitive with regard to apical senescence. Gibberellic acid (GA3) applied to the apical bud of G2 plants in LD delayed apical senescence indefinitely, while N(6)-benzyladenine and α-naphthaleneacetic acid were ineffective. Of the gibberellins native to pea, GA9 had no effect whereas GA20 had a moderate senescence-delaying effect. [(3)H]GA9 metabolism in intact leaves of G2 plants was inhibited by LD and was restored by placing the plants back in SD. Leaves of photoperiod-insensitive lines (I-types) metabolized GA9 readily regardless of photoperiod, but the metabolites differed qualitatively from those in G2 leaves. A polar GA9 metabolite, GAE, was found only in G2 plants in SD. The level of GA-like substances in methanol extracts from G2 plants dropped about 10-fold after the plants were moved from SD to LD; it was restored by transferring the plants back to SD. A polar zone of these GA-like materials co-chromatographed with GAE. It is suggested that a polar gibberellin is synthesized by G2 plants in SD; this gibberellin promotes shoot growth and meristematic activity in the shoot apex, preventing senescence. PMID:24414866

  6. Value addition to bamboo shoots: a review.

    PubMed

    Choudhury, Debangana; Sahu, Jatindra K; Sharma, G D

    2012-08-01

    Bamboo shoot forms a traditional delicacy in many countries. Being low in fat content and high in potassium, carbohydrate, dietary fibres, Vitamins and active materials, bamboo shoots are consumed in raw, canned, boiled, marinated, fermented, frozen, liquid and medicinal forms. Although the fresh bamboo shoots of species like Dendraocalamus giganteus are healthier and nutritionally rich, the young shoots, after fortification, can be consumed by processing into a wide range of food products with longer shelf-life and better organoleptic qualities. However, the consumption pattern of bamboo shoots in most of the countries is traditional, non-standardized, seasonal and region-specific with little value addition. Therefore, there exists a great opportunity, especially for the organized food processing sectors to take up the processing of bamboo shoot-based food products in an organized manner. The present article gives an insight into the global scenario of bamboo shoot-based food products and their consumption pattern, the quality attributes, and the opportunities for value addition along with future prospects in view of international food safety, security and nutrition. PMID:23904649

  7. Redox regulation in shoot growth, SAM maintenance and flowering.

    PubMed

    Schippers, Jos Hm; Foyer, Christine H; van Dongen, Joost T

    2016-02-01

    Reactive oxygen species (ROS) and associated reduction/oxidation (redox) controls involving glutathione, glutaredoxins and thioredoxins play key roles in the regulation of plant growth and development. While many questions remain concerning redox functions in the shoot apical meristem (SAM), accumulating evidence suggests that redox master switches integrate major hormone signals and transcriptional networks in the SAM, and so regulate organ growth, polarity and floral development. Auxin-induced activation of plasma-membrane located NADPH-oxidases and mitochondrial respiratory bioenergetics are likely regulators of the ROS bursts that drive the cell cycle in proliferating regions, with other hormones such as jasmonic acid playing propagating or antagonistic roles in gene regulation. Moreover, the activation of oxygen production by photosynthesis and oxygen-dependent N-end rule controls are linked to the transition from cell proliferation to cell expansion and differentiation. While much remains to be understood, the nexus of available redox controls provides a key underpinning mechanism linking hormonal controls, energy metabolism and bioenergetics to plant growth and development. PMID:26799134

  8. Morphogenesis at the inflorescence shoot apex of Anagallis arvensis: surface geometry and growth in comparison with the vegetative shoot

    PubMed Central

    Kwiatkowska, Dorota; Routier-Kierzkowska, Anne-Lise

    2009-01-01

    Quantitative analysis of geometry and surface growth based on the sequential replica method is used to compare morphogenesis at the shoot apex of Anagallis arvensis in the reproductive and vegetative phases of development. Formation of three types of lateral organs takes place at the Anagallis shoot apical meristem (SAM): vegetative leaf primordia are formed during the vegetative phase and leaf-like bracts and flower primordia during the reproductive phase. Although the shapes of all the three types of primordia are very similar during their early developmental stages, areal growth rates and anisotropy of apex surface growth accompanying formation of leaf or bract primordia are profoundly different from those during formation of flower primordia. This provides an example of different modes of de novo formation of a given shape. Moreover, growth accompanying the formation of the boundary between the SAM and flower primordium is entirely different from growth at the adaxial leaf or bract primordium boundary. In the latter, areal growth rates at the future boundary are the lowest of all the apex surface, while in the former they are relatively very high. The direction of maximal growth rate is latitudinal (along the future boundary) in the case of leaf or bract primordium but meridional (across the boundary) in the case of flower. The replica method does not enable direct analysis of growth in the direction perpendicular to the apex surface (anticlinal direction). Nevertheless, the reconstructed surfaces of consecutive replicas taken from an individual apex allow general directions of SAM surface bulging accompanying primordium formation to be recognized. Precise alignment of consecutive reconstructions shows that the direction of initial bulging during the leaf or bract formation is nearly parallel to the shoot axis (upward bulging), while in the case of flower it is perpendicular to the axis (lateral bulging). In future, such 3D reconstructions can be used to assess

  9. The Arabidopsis Circadian System

    PubMed Central

    McClung, C. Robertson; Salomé, Patrice A.; Michael, Todd P.

    2002-01-01

    Rhythms with periods of approximately 24 hr are widespread in nature. Those that persist in constant conditions are termed circadian rhythms and reflect the activity of an endogenous biological clock. Plants, including Arabidopsis, are richly rhythmic. Expression analysis, most recently on a genomic scale, indicates that the Arabidopsis circadian clock regulates a number of key metabolic pathways and stress responses. A number of sensitive and high-throughput assays have been developed to monitor the Arabidopsis clock. These assays have facilitated the identification of components of plant circadian systems through genetic and molecular biological studies. Although much remains to be learned, the framework of the Arabidopsis circadian system is coming into focus. Dedication This review is dedicated to the memory of DeLill Nasser, a wonderful mentor and an unwavering advocate of both Arabidopsis and circadian rhythms research. PMID:22303209

  10. Diagnosis of apical hypertrophic cardiomyopathy: T-wave inversion and relative but not absolute apical left ventricular hypertrophy☆

    PubMed Central

    Flett, Andrew S.; Maestrini, Viviana; Milliken, Don; Fontana, Mariana; Treibel, Thomas A.; Harb, Rami; Sado, Daniel M.; Quarta, Giovanni; Herrey, Anna; Sneddon, James; Elliott, Perry; McKenna, William; Moon, James C.

    2015-01-01

    Background Diagnosis of apical HCM utilizes conventional wall thickness criteria. The normal left ventricular wall thins towards the apex such that normal values are lower in the apical versus the basal segments. The impact of this on the diagnosis of apical hypertrophic cardiomyopathy has not been evaluated. Methods We performed a retrospective review of 2662 consecutive CMR referrals, of which 75 patients were identified in whom there was abnormal T-wave inversion on ECG and a clinical suspicion of hypertrophic cardiomyopathy. These were retrospectively analyzed for imaging features consistent with cardiomyopathy, specifically: relative apical hypertrophy, left atrial dilatation, scar, apical cavity obliteration or apical aneurysm. For comparison, the same evaluation was performed in 60 healthy volunteers and 50 hypertensive patients. Results Of the 75 patients, 48 met conventional HCM diagnostic criteria and went on to act as another comparator group. Twenty-seven did not meet criteria for HCM and of these 5 had no relative apical hypertrophy and were not analyzed further. The remaining 22 patients had relative apical thickening with an apical:basal wall thickness ratio > 1 and a higher prevalence of features consistent with a cardiomyopathy than in the control groups with 54% having 2 or more of the 4 features. No individual in the healthy volunteer group had more than one feature and no hypertension patient had more than 2. Conclusion A cohort of individuals exist with T wave inversion, relative apical hypertrophy and additional imaging features of HCM suggesting an apical HCM phenotype not captured by existing diagnostic criteria. PMID:25666123

  11. Genetical and comparative genomics of Brassica under altered Ca supply identifies Arabidopsis Ca-transporter orthologs.

    PubMed

    Graham, Neil S; Hammond, John P; Lysenko, Artem; Mayes, Sean; O Lochlainn, Seosamh; Blasco, Bego; Bowen, Helen C; Rawlings, Chris J; Rios, Juan J; Welham, Susan; Carion, Pierre W C; Dupuy, Lionel X; King, Graham J; White, Philip J; Broadley, Martin R

    2014-07-01

    Although Ca transport in plants is highly complex, the overexpression of vacuolar Ca(2+) transporters in crops is a promising new technology to improve dietary Ca supplies through biofortification. Here, we sought to identify novel targets for increasing plant Ca accumulation using genetical and comparative genomics. Expression quantitative trait locus (eQTL) mapping to 1895 cis- and 8015 trans-loci were identified in shoots of an inbred mapping population of Brassica rapa (IMB211 × R500); 23 cis- and 948 trans-eQTLs responded specifically to altered Ca supply. eQTLs were screened for functional significance using a large database of shoot Ca concentration phenotypes of Arabidopsis thaliana. From 31 Arabidopsis gene identifiers tagged to robust shoot Ca concentration phenotypes, 21 mapped to 27 B. rapa eQTLs, including orthologs of the Ca(2+) transporters At-CAX1 and At-ACA8. Two of three independent missense mutants of BraA.cax1a, isolated previously by targeting induced local lesions in genomes, have allele-specific shoot Ca concentration phenotypes compared with their segregating wild types. BraA.CAX1a is a promising target for altering the Ca composition of Brassica, consistent with prior knowledge from Arabidopsis. We conclude that multiple-environment eQTL analysis of complex crop genomes combined with comparative genomics is a powerful technique for novel gene identification/prioritization. PMID:25082855

  12. A method to determine waterfowl shooting distances

    USGS Publications Warehouse

    Davenport, D.A.; Sherwood, G.A.; Murdy, H.W.

    1973-01-01

    Long-range shooting at ducks and geese frequently results in a high crippling loss, unretrieved birds and frustrated hunters. A principal problem has been the general inability of hunters or observers to properly judge distance of birds. This paper describes a reasonably accurate method developed to determine shooting distances to geese. Two observers utilized transit-mounted 4X hunting scopes to determine angles and elevations to goose hunters and birds. These data were used to set up a series of triangles by which a distance between hunter and birds could be calculated. Known-distance tests indicated an average measurement error of approximately two percent. An average shooting distance of 71 yards was calculated from 175 sightings. The maximum range was 240 yards and the minimum was 24 yards. The relationship of shooting to clean kills and crippling loss is also discussed.

  13. The growth and form of plant shoots

    NASA Astrophysics Data System (ADS)

    Chelakkot, Raghunath; Mahadevan, L.

    2015-03-01

    Growing plant stems and shoots exhibit a variety of shapes that embody growth in response to various stimuli. We provide a quantitative biophysical theory for these shapes by accounting for the inherent observed passive and active effects: (i) the passive elastic deflection of the shoot due to its own weight, and (ii) the active controllable growth response of the shoot in response to its orientation relative to gravity, and (iii) proprioception, the shoot's growth response to its own observable shape, which is itself determined by its elasticity and weight. A morphospace diagram in terms of two dimensionless parameters representing a scaled local active gravitropic sensitivity, and a scaled passive elastic sag shows how a variety of observed transient and steady morphologies with effective positive, negative and even oscillatory gravitropic behaviors arise in a sentient growing filament naturally, without the need for ad-hoc complex spatio-temporal control strategies.

  14. Trouble shooting system for an electric vehicle

    SciTech Connect

    Horiuchi, M.

    1986-01-14

    This patent describes a trouble shooting system for an electric vehicle. The electric vehicle contains a driving mechanism, a driving operation part and a control device. The driving mechanism includes a power source, an electric motor and a modality for controlling output level from the power supply to the electric motor in response to the driving operation part. The control device includes a microprocessor which receives commands from the driving operation part and supplies a control signal to the driving mechanism in response to a stored drive control program. The trouble shooting system consists of control device storage mechanisms for storing trouble shooting programs for various parts of the vehicle which are executed by the microprocessor. This system also includes a command generating modality responsive to manual operation for supplying a command to the microprocessor to initiate the execution and read out of a selected trouble shooting program and a method by which the microprocessor may display the program being processed.

  15. Cell walls as a stage for intercellular communication regulating shoot meristem development

    PubMed Central

    Tameshige, Toshiaki; Hirakawa, Yuki; Uchida, Naoyuki

    2015-01-01

    Aboveground organs of plants are ultimately derived/generated from the shoot apical meristem (SAM), which is a proliferative tissue located at the apex of the stem. The SAM contains a population of stem cells that provide new cells for organ/tissue formation. The SAM is composed of distinct cell layers and zones with different properties. Primordia of lateral organs develop at the periphery of the SAM. The shoot apex is a dynamic and complex tissue, and as such intercellular communications among cells, layers and zones play significant roles in the coordination of cell proliferation, growth and differentiation to achieve elaborate morphogenesis. Recent findings have highlighted the importance of a number of signaling molecules acting in the cell wall space for the intercellular communication, including classic phytohormones and secretory peptides. Moreover, accumulating evidence has revealed that cell wall properties and their modifying enzymes modulate hormone actions. In this review, we outline how behaviors of signaling molecules and changes of cell wall properties are integrated for the shoot meristem regulation. PMID:26029226

  16. Cell walls as a stage for intercellular communication regulating shoot meristem development.

    PubMed

    Tameshige, Toshiaki; Hirakawa, Yuki; Torii, Keiko U; Uchida, Naoyuki

    2015-01-01

    Aboveground organs of plants are ultimately derived/generated from the shoot apical meristem (SAM), which is a proliferative tissue located at the apex of the stem. The SAM contains a population of stem cells that provide new cells for organ/tissue formation. The SAM is composed of distinct cell layers and zones with different properties. Primordia of lateral organs develop at the periphery of the SAM. The shoot apex is a dynamic and complex tissue, and as such intercellular communications among cells, layers and zones play significant roles in the coordination of cell proliferation, growth and differentiation to achieve elaborate morphogenesis. Recent findings have highlighted the importance of a number of signaling molecules acting in the cell wall space for the intercellular communication, including classic phytohormones and secretory peptides. Moreover, accumulating evidence has revealed that cell wall properties and their modifying enzymes modulate hormone actions. In this review, we outline how behaviors of signaling molecules and changes of cell wall properties are integrated for the shoot meristem regulation. PMID:26029226

  17. Bacterial community profiling of cryogenically ground samples from the apical and coronal root segments of teeth with apical periodontitis.

    PubMed

    Alves, Flávio R F; Siqueira, José F; Carmo, Flávia L; Santos, Adriana L; Peixoto, Raquel S; Rôças, Isabela N; Rosado, Alexandre S

    2009-04-01

    Bacteria located at the apical part of infected root canals are arguably directly involved in the pathogenesis of apical periodontitis. This study was conducted to profile and further compare the bacterial communities established at the apical and middle/coronal segments of infected root canals. Extracted teeth with attached apical periodontitis lesions were sectioned so as to obtain two root fragments representing the apical third and the coronal two thirds. Root fragments were subjected to a cryogenic grinding approach. DNA was extracted from root powder samples and used as a template for bacterial community profiling using a 16S ribosomal RNA gene-based seminested polymerase chain reaction/denaturing gradient gel electrophoresis approach. The mean number of bands in apical samples from teeth with primary infections was 28, ranging from 18 to 48, whereas in the middle/coronal samples, it was also 28, ranging from 19 to 36. Findings showed that the profile of bacterial community colonizing the apical third of infected root canals is as diverse as that occurring at the middle/coronal thirds. A high variability was observed for both interindividual (samples from the same region but from different patients) and intraindividual (samples from different regions of the same tooth) comparisons. The methodology used to prepare and analyze samples was highly effective in disclosing a previously unanticipated broad diversity of endodontic bacterial communities, especially at the apical part of infected root canals. PMID:19345792

  18. Efficacy of Biodentine as an Apical Plug in Nonvital Permanent Teeth with Open Apices: An In Vitro Study

    PubMed Central

    Bani, Mehmet; Sungurtekin-Ekçi, Elif; Odabaş, Mesut Enes

    2015-01-01

    The aim of this study was to evaluate the apical microleakage of Biodentine and MTA orthograde apical plugs and to compare the effect of thickness of these biomaterials on their sealing ability. A total of eighty maxillary anterior teeth were used. The apices were removed by cutting with a diamond disc (Jota, Germany) 2 mm from the apical root end in an attempt to standardize the working length of all specimens to 15 ± 1 mm. Both materials were placed in 1–4 mm thickness as apical plugs root canal. Root canal leakage was evaluated by the fluid filtration technique. One-way ANOVA was used in order to determine normality of dispersal distribution of parameters; thereafter, results were analyzed by Kolmogorov-Smirnov test. Overall, between microleakage values of MTA and Biodentine regardless of apical plug thickness, no difference was observed. In terms of plug thickness, a statistically significant difference was observed between the subgroups of MTA and Biodentine (p < 0.05). The apical sealing ability of Biodentine was comparable to MTA at any apical plug thickness. PMID:26436090

  19. Efficacy of Biodentine as an Apical Plug in Nonvital Permanent Teeth with Open Apices: An In Vitro Study.

    PubMed

    Bani, Mehmet; Sungurtekin-Ekçi, Elif; Odabaş, Mesut Enes

    2015-01-01

    The aim of this study was to evaluate the apical microleakage of Biodentine and MTA orthograde apical plugs and to compare the effect of thickness of these biomaterials on their sealing ability. A total of eighty maxillary anterior teeth were used. The apices were removed by cutting with a diamond disc (Jota, Germany) 2 mm from the apical root end in an attempt to standardize the working length of all specimens to 15 ± 1 mm. Both materials were placed in 1-4 mm thickness as apical plugs root canal. Root canal leakage was evaluated by the fluid filtration technique. One-way ANOVA was used in order to determine normality of dispersal distribution of parameters; thereafter, results were analyzed by Kolmogorov-Smirnov test. Overall, between microleakage values of MTA and Biodentine regardless of apical plug thickness, no difference was observed. In terms of plug thickness, a statistically significant difference was observed between the subgroups of MTA and Biodentine (p < 0.05). The apical sealing ability of Biodentine was comparable to MTA at any apical plug thickness. PMID:26436090

  20. Early events in geotropism of seedling shoots

    NASA Technical Reports Server (NTRS)

    Pickard, B. G.

    1985-01-01

    Developments during the first ten minutes of geotropic stimulation in plant seedling shoots are reviewed. Topics include induction and curvature; early processes; the relationship between auxin, electric field, calcium, and differential growth; gravity reception leading to Went-Cholodny transport; and comparison of root and shoot. Early processes reviewed are sedimentation of amyloplasts, release of ethylene, rise of electrical and auxin asymmetry, redistribution of calcium, asymmetric vascular transport, increase in tendency to deposit callose, and simulation of putative exocytotic voltage transients.

  1. A tomato strigolactone-impaired mutant displays aberrant shoot morphology and plant interactions.

    PubMed

    Koltai, Hinanit; LekKala, Sivarama P; Bhattacharya, Chaitali; Mayzlish-Gati, Einav; Resnick, Nathalie; Wininger, Smadar; Dor, Evgenya; Yoneyama, Kaori; Yoneyama, Koichi; Hershenhorn, Joseph; Joel, Daniel M; Kapulnik, Yoram

    2010-06-01

    Strigolactones are considered a new group of plant hormones. Their role as modulators of plant growth and signalling molecules for plant interactions first became evident in Arabidopsis, pea, and rice mutants that were flawed in strigolactone production, release, or perception. The first evidence in tomato (Solanum lycopersicon) of strigolactone deficiency is presented here. Sl-ORT1, previously identified as resistant to the parasitic plant Orobanche, had lower levels of arbuscular mycorrhizal fungus (Glomus intraradices) colonization, possibly as a result of its reduced ability to induce mycorrhizal hyphal branching. Biochemical analysis of mutant root extracts suggested that it produces only minute amounts of two of the tomato strigolactones: solanacol and didehydro-orobanchol. Accordingly, the transcription level of a key enzyme (CCD7) putatively involved in strigolactone synthesis in tomato was reduced in Sl-ORT1 compared with the wild type (WT). Sl-ORT1 shoots exhibited increased lateral shoot branching, whereas exogenous application of the synthetic strigolactone GR24 to the mutant restored the WT phenotype by reducing the number of lateral branches. Reduced lateral shoot branching was also evident in grafted plants which included a WT interstock, which was grafted between the mutant rootstock and the scion. In roots of these grafted plants, the CCD7 transcription level was not significantly induced, nor was mycorrhizal sensitivity restored. Hence, WT-interstock grafting, which restores mutant shoot morphology to WT, does not restore mutant root properties to WT. Characterization of the first tomato strigolactone-deficient mutant supports the putative general role of strigolactones as messengers of suppression of lateral shoot branching in a diversity of plant species. PMID:20194924

  2. The growing story of (ARABIDOPSIS) CRINKLY 4.

    PubMed

    Czyzewicz, Nathan; Nikonorova, Natalia; Meyer, Matthew R; Sandal, Priyanka; Shah, Shweta; Vu, Lam Dai; Gevaert, Kris; Rao, A Gururaj; De Smet, Ive

    2016-08-01

    Receptor kinases play important roles in plant growth and development, but only few of them have been functionally characterized in depth. Over the past decade CRINKLY 4 (CR4)-related research has peaked as a result of a newly discovered role of ARABIDOPSIS CR4 (ACR4) in the root. Here, we comprehensively review the available (A)CR4 literature and describe its role in embryo, seed, shoot, and root development, but we also flag an unexpected role in plant defence. In addition, we discuss ACR4 domains and protein structure, describe known ACR4-interacting proteins and substrates, and elaborate on the transcriptional regulation of ACR4 Finally, we address the missing knowledge in our understanding of ACR4 signalling. PMID:27208540

  3. Stimulatory effect of cytokinins and interaction with IAA on the release of lateral buds of pea plants from apical dominance.

    PubMed

    Li, Chunjian; Bangerth, Fritz

    2003-09-01

    Lateral buds of pea plants can be released from apical dominance and even be transformed into dominant shoots when repeatedly treated with synthetic exogenous cytokinins (CKs). The mechanism of the effect of CKs, however, is not clear. The results in this work showed that the stimulatory effects of CKs on the growth of lateral buds and the increase in their fresh weights in pea plants depended on the structure and concentration of the CKs used. The effect of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) was stronger than that of 6-benzylaminopurine (6-BA). Indoleacetic acid (IAA) concentration in shoot, IAA export out of the treated apex and basipetal transport in stems were markedly increased after the application of CPPU or 6-BA to the apex or the second node of pea plant. This increase was positively correlated with the increased concentration of the applied CKs. These results suggest that the increased IAA synthesis and export induced by CKs application might be responsible for the growth of lateral shoots in intact pea plants. PMID:14593807

  4. Tomato Yield Heterosis Is Triggered by a Dosage Sensitivity of the Florigen Pathway That Fine-Tunes Shoot Architecture

    PubMed Central

    Jiang, Ke; Liberatore, Katie L.; Park, Soon Ju; Alvarez, John P.; Lippman, Zachary B.

    2013-01-01

    The superiority of hybrids has long been exploited in agriculture, and although many models explaining “heterosis” have been put forth, direct empirical support is limited. Particularly elusive have been cases of heterozygosity for single gene mutations causing heterosis under a genetic model known as overdominance. In tomato (Solanum lycopersicum), plants carrying mutations in SINGLE FLOWER TRUSS (SFT) encoding the flowering hormone florigen are severely delayed in flowering, become extremely large, and produce few flowers and fruits, but when heterozygous, yields are dramatically increased. Curiously, this overdominance is evident only in the background of “determinate” plants, in which the continuous production of side shoots and inflorescences gradually halts due to a defect in the flowering repressor SELF PRUNING (SP). How sp facilitates sft overdominance is unclear, but is thought to relate to the opposing functions these genes have on flowering time and shoot architecture. We show that sft mutant heterozygosity (sft/+) causes weak semi-dominant delays in flowering of both primary and side shoots. Using transcriptome sequencing of shoot meristems, we demonstrate that this delay begins before seedling meristems become reproductive, followed by delays in subsequent side shoot meristems that, in turn, postpone the arrest of shoot and inflorescence production. Reducing SFT levels in sp plants by artificial microRNAs recapitulates the dose-dependent modification of shoot and inflorescence production of sft/+ heterozygotes, confirming that fine-tuning levels of functional SFT transcripts provides a foundation for higher yields. Finally, we show that although flowering delays by florigen mutant heterozygosity are conserved in Arabidopsis, increased yield is not, likely because cyclical flowering is absent. We suggest sft heterozygosity triggers a yield improvement by optimizing plant architecture via its dosage response in the florigen pathway. Exploiting

  5. Apical surgery: A review of current techniques and outcome

    PubMed Central

    von Arx, Thomas

    2010-01-01

    Apical surgery is considered a standard oral surgical procedure. It is often a last resort to surgically maintain a tooth with a periapical lesion that cannot be managed with conventional endodontic (re-)treatment. The main goal of apical surgery is to prevent bacterial leakage from the root-canal system into the periradicular tissues by placing a tight root-end filling following root-end resection. Clinicians are advised to utilize a surgical microscope to perform apical surgery to benefit from magnification and illumination. In addition, the application of microsurgical techniques in apical surgery, i.e., gentle incision and flap elevation, production of a small osteotomy, and the use of sonic- or ultrasonic driven microtips, will result in less trauma to the patient and faster postsurgical healing. A major step in apical surgery is to identify possible leakage areas at the cut root face and subsequently to ensure adequate root-end filling. Only a tight and persistent apical obturation will allow periapical healing with good long-term prognosis. The present paper describes current indications, techniques and outcome of apical surgery. PMID:24151412

  6. Apical control of conidiation in Aspergillus nidulans.

    PubMed

    Oiartzabal-Arano, Elixabet; Perez-de-Nanclares-Arregi, Elixabet; Espeso, Eduardo A; Etxebeste, Oier

    2016-05-01

    The infection cycle of filamentous fungi consists of two main stages: invasion (growth) and dispersion (development). After the deposition of a spore on a host, germination, polar extension and branching of vegetative cells called hyphae allow a fast and efficient invasion. Under suboptimal conditions, genetic reprogramming of hyphae results in the generation of asexual spores, allowing dissemination to new hosts and the beginning of a new infection cycle. In the model filamentous fungus Aspergillus nidulans, asexual development or conidiation is induced by the upstream developmental activation (UDA) pathway. UDA proteins transduce signals from the tip, the polarity site of hyphae, to nuclei, where developmental programs are transcriptionally activated. The present review summarizes the current knowledge on this tip-to-nucleus communication mechanism, emphasizing its dependence on hyphal polarity. Future approaches to the topic will also be suggested, as stimulating elements contributing to the understanding of how apical signals are coupled with the transcriptional control of development and pathogenesis in filamentous fungi. PMID:26782172

  7. Hypercompliant Apical Membranes of Bladder Umbrella Cells

    PubMed Central

    Mathai, John C.; Zhou, Enhua H.; Yu, Weiqun; Kim, Jae Hun; Zhou, Ge; Liao, Yi; Sun, Tung-Tien; Fredberg, Jeffrey J.; Zeidel, Mark L.

    2014-01-01

    Urinary bladder undergoes dramatic volume changes during filling and voiding cycles. In the bladder the luminal surface of terminally differentiated urothelial umbrella cells is almost completely covered by plaques. These plaques (500 to 1000 nm) are made of a family of proteins called uroplakins that are known to form a tight barrier to prevent leakage of water and solutes. Electron micrographs from previous studies show these plaques to be interconnected by hinge regions to form structures that appear rigid, but these same structures must accommodate large changes in cell shape during voiding and filling cycles. To resolve this paradox, we measured the stiffness of the intact, living urothelial apical membrane and found it to be highly deformable, even more so than the red blood cell membrane. The intermediate cells underlying the umbrella cells do not have uroplakins but their membranes are an order of magnitude stiffer. Using uroplakin knockout mouse models we show that cell compliance is conferred by uroplakins. This hypercompliance may be essential for the maintenance of barrier function under dramatic cell deformation during filling and voiding of the bladder. PMID:25229135

  8. Development of marker genes for jasmonic acid signaling in shoots and roots of wheat.

    PubMed

    Liu, Hongwei; Carvalhais, Lilia Costa; Kazan, Kemal; Schenk, Peer M

    2016-05-01

    The jasmonic acid (JA) signaling pathway plays key roles in a diverse array of plant development, reproduction, and responses to biotic and abiotic stresses. Most of our understanding of the JA signaling pathway derives from the dicot model plant Arabidopsis thaliana, while corresponding knowledge in wheat is somewhat limited. In this study, the expression of 41 genes implicated in the JA signaling pathway has been assessed on 10 day-old bread wheat seedlings, 24 h, 48 h, and 72 h after methyl-jasmonate (MeJA) treatment using quantitative real-time PCR. The examined genes have been previously reported to be involved in JA biosynthesis and catabolism, JA perception and signaling, and pathogen defense in wheat shoots and roots. This study provides evidence to suggest that the effect of MeJA treatment is more prominent in shoots than roots of wheat seedlings, and substantial regulation of the JA pathway-dependent defense genes occurs at 72 h after MeJA treatment. Results show that the expression of 22 genes was significantly affected by MeJA treatment in wheat shoots. However, only PR1.1 and PR3 were significantly differentially expressed in wheat roots, both at 24 h post-MeJA treatment, with other genes showing large variation in their gene expression in roots. While providing marker genes on JA signaling in wheat, future work may focus on elucidating the regulatory function of JA-modulated transcription factors, some of which have well-studied potential orthologs in Arabidopsis. PMID:27115051

  9. Arabidopsis gene expression patterns are altered during spaceflight

    NASA Astrophysics Data System (ADS)

    Paul, Anna-Lisa; Popp, Michael P.; Gurley, William B.; Guy, Charles; Norwood, Kelly L.; Ferl, Robert J.

    The exposure of Arabidopsis thaliana (Arabidopsis) plants to spaceflight environments results in differential gene expression. A 5-day mission on orbiter Columbia in 1999 (STS-93) carried transgenic Arabidopsis plants engineered with a transgene composed of the alcohol dehydrogenase (Adh) gene promoter linked to the β-Glucuronidase (GUS) reporter gene. The plants were used to evaluate the effects of spaceflight on gene expression patterns initially by using the Adh/GUS transgene to address specifically the possibility that spaceflight induces a hypoxic stress response (Paul, A.L., Daugherty, C.J., Bihn, E.A., Chapman, D.K., Norwood, K.L., Ferl, R.J., 2001. Transgene expression patterns indicate that spaceflight affects stress signal perception and transduction in arabidopsis, Plant Physiol. 126, 613-621). As a follow-on to the reporter gene analysis, we report here the evaluation of genome-wide patterns of native gene expression within Arabidopsis shoots utilizing the Agilent DNA array of 21,000 Arabidopsis genes. As a control for the veracity of the array analyses, a selection of genes was further characterized with quantitative Real-Time RT PCR (ABI - Taqman®). Comparison of the patterns of expression for arrays probed with RNA isolated from plants exposed to spaceflight compared to RNA isolated from ground control plants revealed 182 genes that were differentially expressed in response to the spaceflight mission by more than 4-fold, and of those only 50 genes were expressed at levels chosen to support a conservative change call. None of the genes that are hallmarks of hypoxic stress were induced to this level. However, genes related to heat shock were dramatically induced - but in a pattern and under growth conditions that are not easily explained by elevated temperatures. These gene expression data are discussed in light of current models for plant responses to the spaceflight environment and with regard to potential future spaceflight experiment

  10. Detection of Treponema Denticola in Symptomatic Apical Periodontitis and in Symptomatic Apical Abscesses by Real-Time PCR

    PubMed Central

    Ozbek, Selcuk M.; Ozbek, Ahmet; Erdogan, Aziz S.

    2009-01-01

    Objectives: The aim of this study was to investigate the presence of Treponema denticola in symptomatic apical periodontitis and in symptomatic apical abscesses by real-time polymerase chain reaction (PCR) method. Methods: Microbial samples were collected from 60 single-rooted teeth having carious lesions and necrotic pulps. For each tooth, clinical data including patient symptoms were recorded. Teeth were categorized by diagnosis as having symptomatic apical periodontitis or symptomatic apical abscess. Aseptic microbial samples were collected using paper points from 30 infected root canals and from aspirates of 30 abscesses. DNA was extracted from the samples by using a QIAamp® DNA mini-kit and analyzed with real-time PCR. Results: T. denticola was detected in 24 of 30 cases diagnosed as symptomatic apical abscesses (80%), and 19 of 30 cases diagnosed as symptomatic apical periodontitis (63.3%). In general T. denticola was found in 43 of 60 cases (71.6%). Conclusions: Our findings suggest that T. denticola can participate in the pathogenesis of symptomatic apical abscesses. PMID:19421390

  11. Thermoinhibition uncovers a role for strigolactones in Arabidopsis seed germination.

    PubMed

    Toh, Shigeo; Kamiya, Yuji; Kawakami, Naoto; Nambara, Eiji; McCourt, Peter; Tsuchiya, Yuichiro

    2012-01-01

    Strigolactones are host factors that stimulate seed germination of parasitic plant species such as Striga and Orobanche. This hormone is also important in shoot branching architecture and photomorphogenic development. Strigolactone biosynthetic and signaling mutants in model systems, unlike parasitic plants, only show seed germination phenotypes under limited growth condition. To understand the roles of strigolactones in seed germination, it is necessary to develop a tractable experimental system using model plants such as Arabidopsis. Here, we report that thermoinhibition, which involves exposing seeds to high temperatures, uncovers a clear role for strigolactones in promoting Arabidopsis seed germination. Both strigolactone biosynthetic and signaling mutants showed increased sensitivity to seed thermoinhibition. The synthetic strigolactone GR24 rescued germination of thermoinbibited biosynthetic mutant seeds but not a signaling mutant. Hormone analysis revealed that strigolactones alleviate thermoinhibition by modulating levels of the two plant hormones, GA and ABA. We also showed that GR24 was able to counteract secondary dormancy in Arabidopsis ecotype Columbia (Col) and Cape Verde island (Cvi). Systematic hormone analysis of germinating Striga helmonthica seeds suggested a common mechanism between the parasitic and non-parasitic seeds with respect to how hormones regulate germination. Thus, our simple assay system using Arabidopsis thermoinhibition allows comparisons to determine similarities and differences between parasitic plants and model experimental systems for the use of strigolactones. PMID:22173099

  12. Three ancient hormonal cues co-ordinate shoot branching in a moss

    PubMed Central

    Coudert, Yoan; Palubicki, Wojtek; Ljung, Karin; Novak, Ondrej; Leyser, Ottoline; Harrison, C Jill

    2015-01-01

    Shoot branching is a primary contributor to plant architecture, evolving independently in flowering plant sporophytes and moss gametophytes. Mechanistic understanding of branching is largely limited to flowering plants such as Arabidopsis, which have a recent evolutionary origin. We show that in gametophytic shoots of Physcomitrella, lateral branches arise by re-specification of epidermal cells into branch initials. A simple model co-ordinating the activity of leafy shoot tips can account for branching patterns, and three known and ancient hormonal regulators of sporophytic branching interact to generate the branching pattern- auxin, cytokinin and strigolactone. The mode of auxin transport required in branch patterning is a key divergence point from known sporophytic pathways. Although PIN-mediated basipetal auxin transport regulates branching patterns in flowering plants, this is not so in Physcomitrella, where bi-directional transport is required to generate realistic branching patterns. Experiments with callose synthesis inhibitors suggest plasmodesmal connectivity as a potential mechanism for transport. DOI: http://dx.doi.org/10.7554/eLife.06808.001 PMID:25806686

  13. EXB1/WRKY71 transcription factor regulates both shoot branching and responses to abiotic stresses.

    PubMed

    Guo, Dongshu; Qin, Genji

    2016-03-01

    As the sessile organisms, plants evolve different strategies to survive in adverse environmental conditions. The elaborate regulation of shoot branching is an important strategy for plant morphological adaptation to various environments, while the regulation of reactive oxygen species (ROS), salicylic acid (SA) and jasmonic acid (JA) is pivotal for plant responses to biotic and abiotic stresses. Recently, we have demonstrated that Arabidopsis EXB1, a WRKY transcription factor, is a positive regulator of shoot branching as a cover story in Plant Cell. Here we show that WRKY23, an EXB1 close member, has a redundant role in control of shoot branching. We further show that EXB1 is induced by H2O2, ABA or mannitol treatments, suggesting that EXB1 may also play roles in plant responses to abiotic stresses. RNA-sequencing (RNA-seq) analysis using 4EnhpEXB1-EXB1GR inducible line indicates that the genes involved in oxidative stress, oxidation reduction, SA or JA signaling pathway are regulated by EXB1 induction in a short time. We suggest that EXB1/WRKY71 transcription factor may play pivotal roles in plant adaptation to environments by both morphological and physiological ways. PMID:26914912

  14. Photoperiodic flowering regulation in Arabidopsis thaliana

    PubMed Central

    Golembeski, Greg S.; Kinmonth-Schultz, Hannah A.; Song, Young Hun; Imaizumi, Takato

    2015-01-01

    Photoperiod, or the duration of light in a given day, is a critical cue that flowering plants utilize to effectively assess seasonal information and coordinate their reproductive development in synchrony with the external environment. The use of the model plant, Arabidopsis thaliana, has greatly improved our understanding of the molecular mechanisms that determine how plants process and utilize photoperiodic information to coordinate a flowering response. This mechanism is typified by the transcriptional activation of FLOWERING LOCUS T (FT) gene by the transcription factor CONSTANS (CO) under inductive long-day conditions in Arabidopsis. FT protein then moves from the leaves to the shoot apex, where floral meristem development can be initiated. As a point of integration from a variety of environmental factors in the context of a larger system of regulatory pathways that affect flowering, the importance of photoreceptors and the circadian clock in CO regulation throughout the day has been a key feature of the photoperiodic flowering pathway. In addition to these established mechanisms, the recent discovery of a photosynthate derivative trehalose-6-phosphate as an activator of FT in leaves has interesting implications for the involvement of photosynthesis in the photoperiodic flowering response that were suggested from previous physiological experiments in flowering induction. PMID:25684830

  15. Shooting Mechanisms in Nature: A Systematic Review

    PubMed Central

    Sakes, Aimée; van der Wiel, Marleen; Henselmans, Paul W. J.; van Leeuwen, Johan L.; Dodou, Dimitra; Breedveld, Paul

    2016-01-01

    Background In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill. Methods We systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting. Results Shooting mechanisms were identified with projectile masses ranging from 1·10−9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi), or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals), or water evaporation from the system (reaching up to −197 atmospheres; observed in plants and fungi). The generated energy is stored as elastic (potential) energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1) in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum) by compression of the spore and droplets and (2) in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5

  16. Polarized cytokinesis in vacuolate cells of Arabidopsis

    PubMed Central

    Cutler, Sean R.; Ehrhardt, David W.

    2002-01-01

    The view of plant-cell cytokinesis commonly depicted in textbooks is of a symmetrical process, with the phragmoplast initiating in the center of the cell and growing outward to the parental cell membrane. In contrast to this picture, we observe that cell-plate development in Arabidopsis shoot cells is highly polarized along the plane of division. Three-dimensional live-cell imaging reveals that the mitotic spindle and phragmoplast are laterally displaced, and that the growing cell plate anchors on one side of the cell at an early stage of cytokinesis. Growth of phragmoplast across the cell creates a new partition in its wake, giving the visual effect of a curtain being pulled across the cell. Throughout this process, the advancing front of the phragmoplast is in intimate contact with the parental wall, suggesting that short-range interactions between the phragmoplast and plasma membrane may play important roles in guiding the cell plate throughout much of its development. Polarized cytokinesis was observed in a wide variety of vacuolate shoot cells and in some small root cells, implying that it is not solely a function of cell size. This mode of cytokinesis may provide a mechanically robust mechanism for cell-plate formation in large cells and suggests a simple explanation for the occurrence of cell wall stubs observed upon drug treatment or in cytokinetic mutants. PMID:11880633

  17. A transcranial Doppler sonography study of shoot/don't-shoot responding.

    PubMed

    Schultz, Natasha B; Matthews, Gerald; Warm, Joel S; Washburn, David A

    2009-08-01

    The purpose of this study was to examine the relationship between changes in cerebral blood-flow velocity and performance on a speeded shoot/don't-shoot task. Brain activity as indicated by cerebral blood-flow velocity (hemovelocity) was recorded using the transcranial Doppler ultrasonography. A shoot/don't-shoot decision-making task presented participants with threat/nonthreat stimuli in the form of bull's-eye images of various colors. Participants were required to shoot threat targets using a laser-modified handgun. Results support a vigilance decrement in both the performance measures and hemovelocity. Performance, as measured by reaction time, number of hits, and marksmanship, decreased across the length of the vigil. Hemovelocity slowed across the left and right hemispheres as the task progressed, and hemovelocity was slower in the right hemisphere than in the left hemisphere. PMID:19587168

  18. Signal transduction regulating meristem development in Arabidopsis. Final report

    SciTech Connect

    Cark, Steven E.

    2003-09-10

    Research support by DE-FG02-96ER20227 focused on the CLV loci and their regulation of organ formation at the Arabidopsis shoot meristem. Shoot meristem function is central to plant development as all of the above-ground organs and tissues of the plant are derived post-embryonically from the shoot meristem. At the shoot meristem, stem cells are maintained, and progeny cells undergo a switch toward differentiation and organ formation. The CLV loci, represented by three genes CLV1, CLV2 and CLV3 are key regulators of meristem development. Each of the CLV loci encode a putative receptor-mediated signaling component. When this work began, virtually nothing was known about receptor-mediated signaling in plants. Thus, our goal was to both characterize these genes and the proteins they encode as regulators of meristem development, and to investigate how receptor-mediated signaling might function in plants. Our work lead to several major publications that were significant contributions to understanding this system.

  19. Cadmium uptake, translocation and tolerance in the hyperaccumulator Arabidopsis halleri.

    PubMed

    Zhao, F J; Jiang, R F; Dunham, S J; McGrath, S P

    2006-01-01

    Arabidopsis halleri is a well-known zinc (Zn) hyperaccumulator, but its status as a cadmium (Cd) hyperaccumulator is less certain. Here, we investigated whether A. halleri can hyperaccumulate Cd and whether Cd is transported via the Zn pathway. Growth and Cd and Zn uptake were determined in hydroponic experiments with different Cd and Zn concentrations. Short-term uptake and root-to-shoot transport were measured with radioactive 109Cd and 65Zn labelling. A. halleri accumulated > 1000 mg Cd kg(-1) in shoot dry weight at external Cd concentrations >or= 5 microm, but the short-term uptake rate of 109Cd was much lower than that of 65Zn. Zinc inhibited short-term 109Cd uptake kinetics and root-to-shoot translocation, as well as long-term Cd accumulation in shoots. Uptake of 109Cd and 65Zn were up-regulated, respectively, by low iron (Fe) or Zn status. A. halleri was much less tolerant to Cd than to Zn. We conclude that A. halleri is able to hyperaccumulate Cd partly, at least, through the Zn pathway, but the mechanisms responsible for cellular Zn tolerance cannot detoxify Cd effectively. PMID:17096791

  20. Auxin transport in an auxin-resistant mutant of arabidopsis thaliana

    SciTech Connect

    Lincoln, C.; Benning, C.; Estelle, M.

    1987-04-01

    The authors are studying a group of allelic recessive mutations in Arabidopsis called axr-1. Homozygous axr-1 plants are resistant to exogenously applied auxin. In addition, axr-1 mutations all confer a number of development abnormalities including an apparent reduction in apical dominance, loss of normal geotropic response, and a failure to self-fertilize due to a decrease in stamen elongation. In order to determine whether this pleiotropic phenotype is due to an alteration in auxin transport they have adapted the agar block transport assay for use in Arabidopsis stem segments. Their results indicate that as in other plant species, auxin transport is strongly polar in Arabidopsis stem segments. In addition transport is inhibited by the well characterized auxin transport inhibitor N-1-naphthylphthalamic acid and the artificial auxin 2,4-D. These results as well as the characterization of transport in axr-1 plants will be presented.

  1. Selective deactivation of gibberellins below the shoot apex is critical to flowering but not to stem elongation of Lolium.

    PubMed

    King, Rod W; Mander, Lewis N; Asp, Torben; MacMillan, Colleen P; Blundell, Cheryl A; Evans, Lloyd T

    2008-03-01

    Gibberellins (GAs) cause dramatic increases in plant height and a genetic block in the synthesis of GA(1) explains the dwarfing of Mendel's pea. For flowering, it is GA(5) which is important in the long-day (LD) responsive grass, Lolium. As we show here, GA(1) and GA(4) are restricted in their effectiveness for flowering because they are deactivated by C-2 hydroxylation below the shoot apex. In contrast, GA(5) is effective because of its structural protection at C-2. Excised vegetative shoot tips rapidly degrade [14C]GA(1), [14C]GA(4), and [14C]GA(20) (>80% in 6 h), but not [14C]GA(5). Coincidentally, genes encoding two 2beta-oxidases and a putative 16-17-epoxidase were most expressed just below the shoot apex (<3 mm). Further down the immature stem (>4 mm), expression of these GA deactivation genes is reduced, so allowing GA(1) and GA(4) to promote sub-apical stem elongation. Subsequently, GA degradation declines in florally induced shoot tips and these GAs can become active for floral development. Structural changes which stabilize GA(4) confirm the link between florigenicity and restricted GA 2beta-hydroxylation (e.g. 2alpha-hydroxylation and C-2 di-methylation). Additionally, a 2-oxidase inhibitor (Trinexapac Ethyl) enhanced the activity of applied GA(4), as did limiting C-16,17 epoxidation in 16,17-dihydro GAs or after C-13 hydroxylation. Overall, deactivation of GA(1) and GA(4) just below the shoot apex effectively restricts their florigenicity in Lolium and, conversely, with GA(5), C-2 and C-13 protection against deactivation allows its high florigenicity. Speculatively, such differences in GA access to the shoot apex of grasses may be important for separating floral induction from inflorescence emergence and thus could influence their survival under conditions of herbivore predation. PMID:19825541

  2. Long-Day Induction of Flowering in Lolium temulentum Involves Sequential Increases in Specific Gibberellins at the Shoot Apex1

    PubMed Central

    King, Rod W.; Moritz, Thomas; Evans, Lloyd T.; Junttila, Olavi; Herlt, Anthony J.

    2001-01-01

    One challenge for plant biology has been to identify floral stimuli at the shoot apex. Using sensitive and specific gas chromatography-mass spectrometry techniques, we have followed changes in gibberellins (GAs) at the shoot apex during long day (LD)-regulated induction of flowering in the grass Lolium temulentum. Two separate roles of GAs in flowering are indicated. First, within 8 h of an inductive LD, i.e. at the time of floral evocation, the GA5 content of the shoot apex doubled to about 120 ng g−1 dry weight. The concentration of applied GA5 required for floral induction of excised apices (R.W. King, C. Blundell, L.T. Evans [1993] Aust J Plant Physiol 20: 337–348) was similar to that in the shoot apex. Leaf-applied [2H4] GA5 was transported intact from the leaf to the shoot apex, flowering being proportional to the amount of GA5 imported. Thus, GA5 could be part of the LD stimulus for floral evocation of L. temulentum or, alternatively, its increase at the shoot apex could follow import of a primary floral stimulus. Later, during inflorescence differentiation and especially after exposure to additional LD, a second GA action was apparent. The content of GA1 and GA4 in the apex increased greatly, whereas GA5 decreased by up to 75%. GA4 applied during inflorescence differentiation strongly promoted flowering and stem elongation, whereas it was ineffective for earlier floral evocation although it caused stem growth at all times of application. Thus, we conclude that GA1 and GA4 are secondary, late-acting LD stimuli for inflorescence differentiation in L. temulentum. PMID:11598236

  3. BOREAS TE-12 SSA Shoot Geometry Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Walter-Shea, Elizabeth A.; Mesarch, Mark A.; Cheng, L.; Yang, Litao

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-12 (Terrestrial Ecology) team collected shoot geometry data in 1993 and 1994 from aspen, jack pine, and black spruce trees. Collections were made at the Southern Study Area Nipawin Fen Site (SSA FEN), Young Jack Pine (YJP), Old Jack Pine (OJP), Old Aspen (OA), Young Aspen (YA), Mixed Site (MIX), and Old Black Spruce (OBS) sites. A caliper was used to measure shoot and needle lengths and widths. A volume displacement procedure was used to measure the weight of the shoot or twig submerged in water. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  4. Sucrose amendment enhances phytoaccumulation of the herbicide atrazine in Arabidopsis thaliana.

    PubMed

    Sulmon, Cécile; Gouesbet, Gwenola; Binet, Françoise; Martin-Laurent, Fabrice; El Amrani, Abdelhak; Couée, Ivan

    2007-01-01

    Growth in the presence of sucrose was shown to confer to Arabidopsis thaliana (thale cress or mustard weed) seedlings, under conditions of in vitro culture, a high level of tolerance to the herbicide atrazine and to other photosynthesis inhibitors. This tolerance was associated with root-to-shoot transfer and accumulation of atrazine in shoots, which resulted in significant decrease of herbicide levels in the growth medium. In soil microcosms, application of exogenous sucrose was found to confer tolerance and capacity to accumulate atrazine in Arabidopsis thaliana plants grown on atrazine-contaminated soil, and resulted in enhanced decontamination of the soil. Application of sucrose to plants grown on herbicide-polluted soil, which increases plant tolerance and xenobiotic absorption, thus appears to be potentially useful for phytoremediation. PMID:16769161

  5. Contagion in Mass Killings and School Shootings

    PubMed Central

    Towers, Sherry; Gomez-Lievano, Andres; Khan, Maryam; Mubayi, Anuj; Castillo-Chavez, Carlos

    2015-01-01

    Background Several past studies have found that media reports of suicides and homicides appear to subsequently increase the incidence of similar events in the community, apparently due to the coverage planting the seeds of ideation in at-risk individuals to commit similar acts. Methods Here we explore whether or not contagion is evident in more high-profile incidents, such as school shootings and mass killings (incidents with four or more people killed). We fit a contagion model to recent data sets related to such incidents in the US, with terms that take into account the fact that a school shooting or mass murder may temporarily increase the probability of a similar event in the immediate future, by assuming an exponential decay in contagiousness after an event. Conclusions We find significant evidence that mass killings involving firearms are incented by similar events in the immediate past. On average, this temporary increase in probability lasts 13 days, and each incident incites at least 0.30 new incidents (p = 0.0015). We also find significant evidence of contagion in school shootings, for which an incident is contagious for an average of 13 days, and incites an average of at least 0.22 new incidents (p = 0.0001). All p-values are assessed based on a likelihood ratio test comparing the likelihood of a contagion model to that of a null model with no contagion. On average, mass killings involving firearms occur approximately every two weeks in the US, while school shootings occur on average monthly. We find that state prevalence of firearm ownership is significantly associated with the state incidence of mass killings with firearms, school shootings, and mass shootings. PMID:26135941

  6. Development of Apical Blebbing in the Boar Epididymis

    PubMed Central

    Hughes, Jennifer; Berger, Trish

    2015-01-01

    Microvesicles are of increasing interest in biology as part of normal function of numerous systems; from the immune system (T cell activation) to implantation of the embryo (invasion of the trophoblasts) and sperm maturation (protein transfer in the epididymis). Yet, the mechanisms involved in the appearance of apical blebbing from healthy cells as part of their normal function remain understudied. Microvesicles are produced via one of two pathways: exocytosis or apical blebbing also termed ectocytosis. This work quantifies the histological appearance of apical blebbing in the porcine epididymis during development and examines the role of endogenous estrogens in regulating this blebbing. Apical blebbing appears at puberty and increases in a linear manner into sexual maturity suggesting that this blebbing is a mature phenotype. Endogenous estrogen levels were reduced with an aromatase inhibitor but such a reduction did not affect apical blebbing in treated animals compared with their vehicle-treated littermates. Epididymal production of apical blebs is a secretion mechanism of functionally mature principal cells regulated by factors other than estradiol. PMID:25996942

  7. Haemostatic agents in apical surgery. A systematic review

    PubMed Central

    Clé-Ovejero, Adrià

    2016-01-01

    Background Blood presence in apical surgery can prevent the correct vision of the surgical field, change the physical properties of filling materials and reduce their sealing ability. Objetive To describe which are the most effective and safest haemostatic agents to control bleeding in patients undergoing apical surgery. Material and Methods TWe carried out a systematic review, using Medline and Cochrane Library databases, of human clinical studies published in the last 10 years. Results The agents that proved more effective in bleeding control were calcium sulphate (100%) and collagen plus epinephrine (92.9%) followed by ferric sulphate (60%), gauze packing (30%) and collagen (16.7%). When using aluminium chloride (Expasyl®), over 90% of the apical lesions improved, but this agent seemed to increase swelling. Epinephrine with collagen did not significantly raise either blood pressure or heart rate. Conclusions Despite the use of several haemostatic materials in apical surgery, there is little evidence on their effectiveness and safety. The most effective haemostatic agents were calcium sulphate and epinephrine plus collagen. Epinephrine plus collagen did not seem to significantly raise blood pressure or heart rate during surgery. Aluminium chloride did not increase postoperative pain but could slightly increase postoperative swelling. Randomized clinical trials are needed to assess the haemostatic effectiveness and adverse effects of haemostatic materials in apical surgery. Key words:Haemostasis, apical surgery. PMID:27475689

  8. Healing of apical rarefaction of three nonvital open apex anterior teeth using a white portland cement apical plug

    PubMed Central

    Chakraborty, Amitabha; Dey, Bibhas; Dhar, Reema; Sardar, Prabir

    2012-01-01

    The major challenge of performing root canal treatment in an open apex pulp-less tooth is to obtain a good apical seal. MTA has been successfully used to achieve a good apical seal, wherein the root canal obturation can be done immediately. MTA and White Portland Cement has been shown similarity in their physical, chemical and biological properties and has also shown similar outcome when used in animal studies and human trials. In our study, open apex of three non vital upper central incisors has been plugged using modified white Portland cement. 3 to 6 months follow up revealed absence of clinical symptoms and disappearance of peri-apical rarefactions. The positive clinical outcome may encourage the future use of white Portland cement as an apical plug material in case of non vital open apex tooth as much cheaper substitute of MTA. PMID:23230357

  9. Shoot or don't shoot? Why police officers are more inclined to shoot when they are anxious.

    PubMed

    Nieuwenhuys, Arne; Savelsbergh, Geert J P; Oudejans, Raôul R D

    2012-08-01

    We investigated the effect of anxiety on police officers' shooting decisions. Thirty-six police officers participated and executed a low- and high-anxiety video-based test that required them to shoot or not shoot at rapidly appearing suspects that either had a gun and "shot," or had no gun and "surrendered." Anxiety was manipulated by turning on (high anxiety) or turning off (low anxiety) a so-called "shootback canon" that could fire small plastic bullets at the participants. When performing under anxiety, police officers showed a response bias toward shooting, implying that they accidentally shot more often at suspects that surrendered. Furthermore, shot accuracy was lower under anxiety and officers responded faster when suspects had a gun. Finally, because gaze behavior appeared to be unaffected by anxiety, it is concluded that when they were anxious, officers were more inclined to respond on the basis of threat-related inferences and expectations rather than objective, task-relevant visual information. PMID:22023363

  10. Gravity response mechanisms of lateral organs and the control of plant architecture in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Mullen, J.; Hangarter, R.

    Most research on gravity responses in plants has focused on primary roots and shoots, which typically grow in a vertical orientation. However, the patterns of lateral organ formation and their growth orientation, which typically are not vertical, govern plant architecture. For example, in Arabidopsis, when lateral roots emerge from the primary root, they grow at a nearly horizontal orientation. As they elongate, the roots slowly curve until they eventually reach a vertical orientation. The regulation of this lateral root orientation is an important component affecting the overall root system architecture. We have found that this change in orientation is not simply due to the onset of gravitropic competence, as non-vertical lateral roots are capable of both positive and negative gravitropism. Thus, the horizontal growth of the new lateral roots is determined by what is called the gravitropic set-point angle (GSA). In Arabidopsis shoots, rosette leaves and inflorescence branches also display GSA-dependent developmental changes in their orientation. The developmental control of the GSA of lateral organs in Arabidopsis provides us with a useful system for investigating the components involved in regulating directionality of tropistic responses. We have identified several Arabidopsis mutants that have either altered lateral root orientations, altered orientation of lateral organs in the shoot, or both, but maintain normal primary organ orientation. The mgsa ({m}odified {g}ravitropic {s}et-point {a}ngle) mutants with both altered lateral root and shoot orientation show that there are common components in the regulation of growth orientation in the different organs. Rosette leaves and lateral roots also have in common a regulation of positioning by red light. Further molecular and physiological analyses of the GSA mutants will provide insight into the basis of GSA regulation and, thus, a better understanding of how gravity controls plant architecture. [This work was

  11. Differentiation of Apical Bud Cells in a Newly Developed Apical Bud Transplantation Model Using GFP Transgenic Mice as Donor

    PubMed Central

    Sakagami, Ryuji; Yoshinaga, Yasunori; Okamura, Kazuhiko

    2016-01-01

    Rodent mandibular incisors have a unique anatomical structure that allows teeth to grow throughout the lifetime of the rodent. This report presents a novel transplantation technique for studying the apical bud differentiation of rodent mandibular incisors. Incisal apical end tissue with green fluorescent protein from transgenic mouse was transplanted to wild type mice, and the development of the transplanted cells were immunohistologically observed for 12 weeks after the transplantation. Results indicate that the green fluorescent apical end tissue replaced the original tissue, and cells from the apical bud differentiated and extended toward the incisal edge direction. The immunostaining with podoplanin also showed that the characteristics of the green fluorescent tissue were identical to those of the original. The green fluorescent cells were only found in the labial side of the incisor up to 4 weeks. After 12 weeks, however, they were also found in the lingual side. Here the green fluorescent cementocyte-like cells were only present in the cementum close to the dentin surface. This study suggests that some of the cells that form the cellular cementum come from the apical tissue including the apical bud in rodent incisors. PMID:26978064

  12. Multiple Shoot Tip Cultures in Peas.

    ERIC Educational Resources Information Center

    Smith, Robert A.; And Others

    1997-01-01

    Describes an exercise used as a follow-up activity to a lecture presentation exploring the basic methodology and theory of shoot tip cultures. Utilizes a factorial experimental design which allows for the determination of the effects of each factor alone and in combination with each other. Other concepts emphasized include dependent and…

  13. Shooting Gallery Notes. Working Paper #22. Preliminary.

    ERIC Educational Resources Information Center

    Bourgois, Philippe

    This paper contains ethnographic participant-observation field notes taken on a one-night visit to a "shooting gallery" in East Harlem (New York City) along with background information and commentary. East Harlem, also referred to as "El Barrio" or Spanish Harlem, is a 200-square block neighborhood on the upper East Side of Manhattan in New York…

  14. School Shootings; Standards Kill Students and Society

    ERIC Educational Resources Information Center

    Angert, Betsy L.

    2008-01-01

    School shootings have been in the news of late. People ponder what occurs in classrooms today. Why would a young person wish to take a life? Within educational institutions, the killings are a concern. In our dire attempt to teach the children and ensure student success, it seems many of our offspring are lost. Some students feel separate from…

  15. Auditory risk estimates for youth target shooting

    PubMed Central

    Meinke, Deanna K.; Murphy, William J.; Finan, Donald S.; Lankford, James E.; Flamme, Gregory A.; Stewart, Michael; Soendergaard, Jacob; Jerome, Trevor W.

    2015-01-01

    Objective To characterize the impulse noise exposure and auditory risk for youth recreational firearm users engaged in outdoor target shooting events. The youth shooting positions are typically standing or sitting at a table, which places the firearm closer to the ground or reflective surface when compared to adult shooters. Design Acoustic characteristics were examined and the auditory risk estimates were evaluated using contemporary damage-risk criteria for unprotected adult listeners and the 120-dB peak limit suggested by the World Health Organization (1999) for children. Study sample Impulses were generated by 26 firearm/ammunition configurations representing rifles, shotguns, and pistols used by youth. Measurements were obtained relative to a youth shooter’s left ear. Results All firearms generated peak levels that exceeded the 120 dB peak limit suggested by the WHO for children. In general, shooting from the seated position over a tabletop increases the peak levels, LAeq8 and reduces the unprotected maximum permissible exposures (MPEs) for both rifles and pistols. Pistols pose the greatest auditory risk when fired over a tabletop. Conclusion Youth should utilize smaller caliber weapons, preferably from the standing position, and always wear hearing protection whenever engaging in shooting activities to reduce the risk for auditory damage. PMID:24564688

  16. GLUT2 Accumulation in Enterocyte Apical and Intracellular Membranes

    PubMed Central

    Ait-Omar, Amal; Monteiro-Sepulveda, Milena; Poitou, Christine; Le Gall, Maude; Cotillard, Aurélie; Gilet, Jules; Garbin, Kevin; Houllier, Anne; Château, Danièle; Lacombe, Amélie; Veyrie, Nicolas; Hugol, Danielle; Tordjman, Joan; Magnan, Christophe; Serradas, Patricia; Clément, Karine; Leturque, Armelle; Brot-Laroche, Edith

    2011-01-01

    OBJECTIVE In healthy rodents, intestinal sugar absorption in response to sugar-rich meals and insulin is regulated by GLUT2 in enterocyte plasma membranes. Loss of insulin action maintains apical GLUT2 location. In human enterocytes, apical GLUT2 location has not been reported but may be revealed under conditions of insulin resistance. RESEARCH DESIGN AND METHODS Subcellular location of GLUT2 in jejunal enterocytes was analyzed by confocal and electron microscopy imaging and Western blot in 62 well-phenotyped morbidly obese subjects and 7 lean human subjects. GLUT2 locations were assayed in ob/ob and ob/+ mice receiving oral metformin or in high-fat low-carbohydrate diet–fed C57Bl/6 mice. Glucose absorption and secretion were respectively estimated by oral glucose tolerance test and secretion of [U-14C]-3-O-methyl glucose into lumen. RESULTS In human enterocytes, GLUT2 was consistently located in basolateral membranes. Apical GLUT2 location was absent in lean subjects but was observed in 76% of obese subjects and correlated with insulin resistance and glycemia. In addition, intracellular accumulation of GLUT2 with early endosome antigen 1 (EEA1) was associated with reduced MGAT4a activity (glycosylation) in 39% of obese subjects on a low-carbohydrate/high-fat diet. Mice on a low-carbohydrate/high-fat diet for 12 months also exhibited endosomal GLUT2 accumulation and reduced glucose absorption. In ob/ob mice, metformin promoted apical GLUT2 and improved glucose homeostasis. Apical GLUT2 in fasting hyperglycemic ob/ob mice tripled glucose release into intestinal lumen. CONCLUSIONS In morbidly obese insulin-resistant subjects, GLUT2 was accumulated in apical and/or endosomal membranes of enterocytes. Functionally, apical GLUT2 favored and endosomal GLUT2 reduced glucose transepithelial exchanges. Thus, altered GLUT2 locations in enterocytes are a sign of intestinal adaptations to human metabolic pathology. PMID:21852673

  17. ClRTL1 Encodes a Chinese Fir RNase III–Like Protein Involved in Regulating Shoot Branching

    PubMed Central

    Li, Xia; Su, Qian; Zheng, Renhua; Liu, Guangxin; Lu, Ye; Bian, Liming; Chen, Jinhui; Shi, Jisen

    2015-01-01

    Identification of genes controlling shoot branching is crucial for improving plant architecture and increasing crop yield or biomass. A branching mutant of Chinese fir named “Dugansha” (Cunninghamia lanceolata var. dugan.) has been isolated in our laboratory. We chose the cDNA-AFLP technique and an effective strategy to screen genes that potentially regulate shoot branching in Chinese fir using this mutant. An RNase III-like1 cDNA fragment named ClRTL1 was identified as a potential positive regulator. To investigate the function of ClRTL1 in regulating shoot branching, we cloned the full-length cDNA sequence from C. lanceolata (Lamb.) Hook, deduced its secondary structure and function, and overexpressed the coding sequence in Arabidopsis. The ClRTL1 cDNA is 1045 bp and comprises an open reading frame of 705 bp. It encodes a protein of 235 amino acids. The deduced secondary structure of the ClRTL1 indicates that it is a mini-RNase III-like protein. The expression analysis and phenotypes of 35S: ClRTL1 in A. thaliana implies that ClRTL1 plays a role in promoting shoot branching in Chinese fir. PMID:26516842

  18. Somatic hybrids between Arabidopsis thaliana and cytoplasmic male-sterile radish (Raphanus sativus).

    PubMed

    Yamagishi, H; Glimelius, K

    2003-08-01

    Somatic hybrids were produced by protoplast fusion between Arabidopsis thaliana ecotype Columbia and a male-sterile radish line MS-Gensuke ( Raphanus sativus) with the Ogura cytoplasm. Forty-one shoots were differentiated from the regenerated calli and established as shoot cultures in vitro. About 20 of these shoots were judged to be hybrids based on growth characteristics and morphology. Molecular analyses of 11 shoots were performed, confirming the hybrid features. Of these 11 shoots, eight were established as rooted plants in the greenhouse. Polymerase chain reaction and randomly amplified polymorphic DNA analyses of the nuclear genomes of all analyzed shoots and plants confirmed that they contained hybrid DNA patterns. Their chromosome numbers also supported the hybrid nature of the plants. Investigations of the organelles in the hybrids revealed that the chloroplast (cp) genome was exclusively represented by radish cpDNA, while the mitochondrial DNA configuration showed a combination of both parental genomes as well as fragments unique to the hybrids. Hybrid plants that flowered were male-sterile independent of the presence of the Ogura CMS-gene orf138. PMID:12827437

  19. Genetical and Comparative Genomics of Brassica under Altered Ca Supply Identifies Arabidopsis Ca-Transporter Orthologs[W][OPEN

    PubMed Central

    Graham, Neil S.; Hammond, John P.; Lysenko, Artem; Mayes, Sean; Ó Lochlainn, Seosamh; Blasco, Bego; Bowen, Helen C.; Rawlings, Chris J.; Rios, Juan J.; Welham, Susan; Carion, Pierre W.C.; Dupuy, Lionel X.; King, Graham J.; White, Philip J.; Broadley, Martin R.

    2014-01-01

    Although Ca transport in plants is highly complex, the overexpression of vacuolar Ca2+ transporters in crops is a promising new technology to improve dietary Ca supplies through biofortification. Here, we sought to identify novel targets for increasing plant Ca accumulation using genetical and comparative genomics. Expression quantitative trait locus (eQTL) mapping to 1895 cis- and 8015 trans-loci were identified in shoots of an inbred mapping population of Brassica rapa (IMB211 × R500); 23 cis- and 948 trans-eQTLs responded specifically to altered Ca supply. eQTLs were screened for functional significance using a large database of shoot Ca concentration phenotypes of Arabidopsis thaliana. From 31 Arabidopsis gene identifiers tagged to robust shoot Ca concentration phenotypes, 21 mapped to 27 B. rapa eQTLs, including orthologs of the Ca2+ transporters At-CAX1 and At-ACA8. Two of three independent missense mutants of BraA.cax1a, isolated previously by targeting induced local lesions in genomes, have allele-specific shoot Ca concentration phenotypes compared with their segregating wild types. BraA.CAX1a is a promising target for altering the Ca composition of Brassica, consistent with prior knowledge from Arabidopsis. We conclude that multiple-environment eQTL analysis of complex crop genomes combined with comparative genomics is a powerful technique for novel gene identification/prioritization. PMID:25082855

  20. Basipetal auxin transport is required for gravitropism in roots of Arabidopsis

    NASA Technical Reports Server (NTRS)

    Rashotte, A. M.; Brady, S. R.; Reed, R. C.; Ante, S. J.; Muday, G. K.; Davies, E. (Principal Investigator)

    2000-01-01

    Auxin transport has been reported to occur in two distinct polarities, acropetally and basipetally, in two different root tissues. The goals of this study were to determine whether both polarities of indole-3-acetic acid (IAA) transport occur in roots of Arabidopsis and to determine which polarity controls the gravity response. Global application of the auxin transport inhibitor naphthylphthalamic acid (NPA) to roots blocked the gravity response, root waving, and root elongation. Immediately after the application of NPA, the root gravity response was completely blocked, as measured by an automated video digitizer. Basipetal [(3)H]IAA transport in Arabidopsis roots was inhibited by NPA, whereas the movement of [(14)C]benzoic acid was not affected. Inhibition of basipetal IAA transport by local application of NPA blocked the gravity response. Inhibition of acropetal IAA transport by application of NPA at the root-shoot junction only partially reduced the gravity response at high NPA concentrations. Excised root tips, which do not receive auxin from the shoot, exhibited a normal response to gravity. The Arabidopsis mutant eir1, which has agravitropic roots, exhibited reduced basipetal IAA transport but wild-type levels of acropetal IAA transport. These results support the hypothesis that basipetally transported IAA controls root gravitropism in Arabidopsis.

  1. Apical infection spreading to adjacent teeth: a case report.

    PubMed

    Komabayashi, Takashi; Jiang, Jin; Zhu, Qiang

    2011-06-01

    This case report describes apical infection on tooth number 24 that spread to adjacent teeth, resulting in devitalized teeth numbers 23 and 25. The 25-year-old Caucasian female patient was referred to the endodontic resident clinic because of uncontrolled apical infection. Root-end surgery and root-end filling of teeth numbers 23, 24, and 25 were performed. The histopathological diagnosis was a periapical cyst; however, the clinical surgical finding of a purulence-filled bone cavity also revealed a periapical abscess. After root-end surgery and regenerative therapy using Mineral Trioxide Aggregate, Bio-Oss xenograft material, and Bio-Gide resorbable collagen membrane, the patient had no symptoms. Radiographs showed the apical lesion had healed satisfactorily at the 6-month, 1-year, and 2-year follow-ups. The clinical implication of this rare case suggests the importance of standard endodontic diagnostic procedures for pulpal and apical diagnosis, prevention of apical periodontitis exacerbation by reducing bacterial factors, and the effectiveness of healing large bone defects using regenerative materials. PMID:21458327

  2. microRNA Expression in Rat Apical Periodontitis Bone Lesion

    PubMed Central

    Gao, Bo; Zheng, Liwei

    2013-01-01

    Apical periodontitis, dominated by dense inflammatory infiltrates and increased osteoclast activities, can lead to alveolar bone destruction and tooth loss. It is believed that miRNA participates in regulating various biological processes, osteoclastogenesis included. This study aims to investigate the differential expression of miRNAs in rat apical periodontitis and explore their functional target genes. Microarray analysis was used to identify differentially expressed miRNAs in apical periodontitis. Bioinformatics technique was applied for predicting the target genes of differentially expressed miRNAs and their biological functions. The result provided us with an insight into the potential biological effects of the differentially expressed miRNAs and showed particular enrichment of target genes involved in the MAPK signaling pathways. These findings may highlight the intricate and specific roles of miRNA in inflammation and osteoclastogenesis, both of which are key aspects of apical periodontitis, thus contributing to the future investigation into the etiology, underlying mechanism and treatment of apical periodontitis. PMID:26273501

  3. Arabidopsis AINTEGUMENTA mediates salt tolerance by trans-repressing SCABP8.

    PubMed

    Meng, Lai-Sheng; Wang, Yi-Bo; Yao, Shun-Qiao; Liu, Aizhong

    2015-08-01

    The Arabidopsis AINTEGUMENTA (ANT) gene, which encodes an APETALA2 (AP2)-like transcription factor, controls plant organ cell number and organ size throughout shoot development. ANT is thus a key factor in the development of plant shoots. Here, we have found that ANT plays an essential role in conferring salt tolerance in Arabidopsis. ant-knockout mutants presented a salt-tolerant phenotype, whereas transgenic plants expressing ANT under the 35S promoter (35S:ANT) exhibited more sensitive phenotypes under high salt stress. Further analysis indicated that ANT functions mainly in the shoot response to salt toxicity. Target gene analysis revealed that ANT bound to the promoter of SOS3-LIKE CALCIUM BINDING PROTEIN 8 (SCABP8), which encodes a putative Ca(2+) sensor, thereby inhibiting expression of SCABP8 (also known as CBL10). It has been reported that the salt sensitivity of scabp8 is more prominent in shoot tissues. Genetic experiments indicated that the mutation of SCABP8 suppresses the ant-knockout salt-tolerant phenotype, implying that ANT functions as a negative transcriptional regulator of SCABP8 upon salt stress. Taken together, the above results reveal that ANT is a novel regulator of salt stress and that ANT binds to the SCABP8 promoter, mediating salt tolerance. PMID:26054800

  4. Effects of long-term hypergravity on growth of Arabidopsis seedlings

    NASA Astrophysics Data System (ADS)

    Karahara, Ichirou; Ando, Naoko; Tamaoki, Daisuke; Kamisaka, Seiichiro

    Effects of altered gravity on growth of plant root are not yet well understood compared to that of shoot organ such as stem, epicotyl or hypocotyl. And besides, its effect on growth is not yet examined at cellular level either in the root or the shoot. In the present study, we examined effects of long-term hypergravity on growth not only of the root but also the shoot at cellular level. Seeds of Arabidopsis were sown on gelrite containing Murashige-Skoog medium and were started to be exposed to hypergravity before germination. Growth of the hypocotyl had been inhibited since 3 d after the onset of hypergravity treatment at both 100 and 300 G while that of the root was not at either gravity. Longitudinal length of epidermal cells in one cell file decreased in response to hypergravity at 300 G in 3 d old hypocotyls while the number of the epidermal cells did not.

  5. The iRoCS Toolbox--3D analysis of the plant root apical meristem at cellular resolution.

    PubMed

    Schmidt, Thorsten; Pasternak, Taras; Liu, Kun; Blein, Thomas; Aubry-Hivet, Dorothée; Dovzhenko, Alexander; Duerr, Jasmin; Teale, William; Ditengou, Franck A; Burkhardt, Hans; Ronneberger, Olaf; Palme, Klaus

    2014-03-01

    To achieve a detailed understanding of processes in biological systems, cellular features must be quantified in the three-dimensional (3D) context of cells and organs. We described use of the intrinsic root coordinate system (iRoCS) as a reference model for the root apical meristem of plants. iRoCS enables direct and quantitative comparison between the root tips of plant populations at single-cell resolution. The iRoCS Toolbox automatically fits standardized coordinates to raw 3D image data. It detects nuclei or segments cells, automatically fits the coordinate system, and groups the nuclei/cells into the root's tissue layers. The division status of each nucleus may also be determined. The only manual step required is to mark the quiescent centre. All intermediate outputs may be refined if necessary. The ability to learn the visual appearance of nuclei by example allows the iRoCS Toolbox to be easily adapted to various phenotypes. The iRoCS Toolbox is provided as an open-source software package, licensed under the GNU General Public License, to make it accessible to a broad community. To demonstrate the power of the technique, we measured subtle changes in cell division patterns caused by modified auxin flux within the Arabidopsis thaliana root apical meristem. PMID:24417645

  6. Salicylic acid antagonizes abscisic acid inhibition of shoot growth and cell cycle progression in rice

    NASA Astrophysics Data System (ADS)

    Meguro, Ayano; Sato, Yutaka

    2014-04-01

    We analysed effects of abscisic acid (ABA, a negative regulatory hormone), alone and in combination with positive or neutral hormones, including salicylic acid (SA), on rice growth and expression of cell cycle-related genes. ABA significantly inhibited shoot growth and induced expression of OsKRP4, OsKRP5, and OsKRP6. A yeast two-hybrid assay showed that OsKRP4, OsKRP5, and OsKRP6 interacted with OsCDKA;1 and/or OsCDKA;2. When SA was simultaneously supplied with ABA, the antagonistic effect of SA completely blocked ABA inhibition. SA also blocked ABA inhibition of DNA replication and thymidine incorporation in the shoot apical meristem. These results suggest that ABA arrests cell cycle progression by inducing expression of OsKRP4, OsKRP5, and OsKRP6, which inhibit the G1/S transition, and that SA antagonizes ABA by blocking expression of OsKRP genes.

  7. Phyllotaxis: from patterns of organogenesis at the meristem to shoot architecture.

    PubMed

    Galvan-Ampudia, Carlos S; Chaumeret, Anaïs M; Godin, Christophe; Vernoux, Teva

    2016-07-01

    The primary architecture of the aerial part of plants is controlled by the shoot apical meristem, a specialized tissue containing a stem cell niche. The iterative generation of new aerial organs, (leaves, lateral inflorescences, and flowers) at the meristem follows regular patterns, called phyllotaxis. Phyllotaxis has long been proposed to self-organize from the combined action of growth and of inhibitory fields blocking organogenesis in the vicinity of existing organs in the meristem. In this review, we will highlight how a combination of mathematical/computational modeling and experimental biology has demonstrated that the spatiotemporal distribution of the plant hormone auxin controls both organogenesis and the establishment of inhibitory fields. We will discuss recent advances showing that auxin likely acts through a combination of biochemical and mechanical regulatory mechanisms that control not only the pattern of organogenesis in the meristem but also postmeristematic growth, to shape the shoot. WIREs Dev Biol 2016, 5:460-473. doi: 10.1002/wdev.231 For further resources related to this article, please visit the WIREs website. PMID:27199252

  8. Causes and management of post-treatment apical periodontitis.

    PubMed

    Siqueira, J F; Rôças, I N; Ricucci, D; Hülsmann, M

    2014-03-01

    Endodontic treatment failure is usually characterised by the presence of post-treatment apical periodontitis, which may be persistent, emergent or recurrent. The major aetiology of post-treatment disease is persistent intraradicular infection, but in some cases a secondary intraradicular infection due to coronal leakage or an extraradicular infection may be the cause of failure. Understanding the causes of endodontic treatment failure is of paramount importance for the proper management of this condition. Teeth with post-treatment apical periodontitis can be managed by either nonsurgical endodontic retreatment or periradicular surgery, both of which have very high chances of restoring the health of the periradicular tissues and maintaining the tooth function in the oral cavity. This review article focuses on the aetiological factors of post-treatment apical periodontitis and discusses the indications and basics of the procedures for optimal clinical management of this condition. PMID:24651336

  9. Dental Apical Papilla as Therapy for Spinal Cord Injury.

    PubMed

    De Berdt, P; Vanacker, J; Ucakar, B; Elens, L; Diogenes, A; Leprince, J G; Deumens, R; des Rieux, A

    2015-11-01

    Stem cells of the apical papilla (SCAP) represent great promise regarding treatment of neural tissue damage, such as spinal cord injury (SCI). They derive from the neural crest, express numerous neurogenic markers, and mediate neurite outgrowth and axonal targeting. The goal of the present work was to investigate for the first time their potential to promote motor recovery after SCI in a rat hemisection model when delivered in their original stem cell niche-that is, by transplantation of the human apical papilla tissue itself into the lesion. Control groups consisted of animals subjected to laminectomy only (shams) and to lesion either untreated or injected with a fibrin hydrogel with or without human SCAP. Basso-Beattie-Bresnahan locomotor scores at 1 and 3 d postsurgery confirmed early functional decline in all SCI groups. This significant impairment was reversed, as seen in CatWalk analyses, after transplantation of apical papilla into the injured spinal cord wound, whereas the other groups demonstrated persistent functional impairment. Moreover, tactile allodynia did not develop as an unwanted side effect in any of the groups, even though the SCAP hydrogel group showed higher expression of the microglial marker Iba-1, which has been frequently associated with allodynia. Notably, the apical papilla transplant group presented with reduced Iba-1 expression level. Masson trichrome and human mitochondria staining showed the preservation of the apical papilla integrity and the presence of numerous human cells, while human cells could no longer be detected in the SCAP hydrogel group at the 6-wk postsurgery time point. Altogether, our data suggest that the transplantation of a human apical papilla at the lesion site improves gait in spinally injured rats and reduces glial reactivity. It also underlines the potential interest for the application of delivering SCAP in their original niche, as compared with use of a fibrin hydrogel. PMID:26341974

  10. Apical potassium channels in the rat connecting tubule.

    PubMed

    Frindt, Gustavo; Palmer, Lawrence G

    2004-11-01

    Apical membrane K channels in the rat connecting tubule (CNT) were studied using the patch-clamp technique. Tubules were isolated from the cortical labyrinth of the kidney and split open to provide access to the apical membrane. Cell-attached patches were formed on presumed principal and/or connecting tubule cells. The major channel type observed had a single-channel conductance of 52 pS, high open probability and kinetics that were only weakly dependent on voltage. These correspond closely to the "SK"-type channels in the cortical collecting duct, identified with the ROMK (Kir1.1) gene product. A second channel type, which was less frequently observed, mediated larger currents and was strongly activated by depolarization of the apical membrane voltage. These were identified as BK or maxi-K channels. The density of active SK channels revealed a high degree of clustering. Although heterogeneity of tubules or of cell types within a tubule could not be excluded, the major factor underlying the distribution appeared to be the presence of channel clusters on the membrane of individual cells. The overall density of channels was higher than that previously found in the cortical collecting tubule (CCT). In contrast to results in the CCT, we did not detect an increase in the overall density of SK channels in the apical membrane after feeding the animals a high-K diet. However, the activity of amiloride-sensitive Na channels was undetectable under control conditions but was increased after both 1 day (90 +/- 24 pA/cell) or 7 days (385 +/- 82 pA/cell) of K loading. Thus one important factor leading to an increased K secretion in the CNT in response to increased dietary K is an increased apical Na conductance, leading to depolarization of the apical membrane voltage and an increased driving force for K movement out into the tubular lumen. PMID:15280155

  11. Early Summer Drought Stress During the First Growing Year Stimulates Extra Shoot Growth in Oak Seedlings (Quercus petraea).

    PubMed

    Turcsán, Arion; Steppe, Kathy; Sárközi, Edit; Erdélyi, Éva; Missoorten, Marc; Mees, Ghislain; Mijnsbrugge, Kristine V

    2016-01-01

    More severe summer droughts are predicted for mid-latitudes in Europe. To evaluate the impact on forest ecosystems and more specifically on forest regeneration, we studied the response to summer drought in oak seedlings (Quercus petraea). Acorns were collected from different mother trees in three stands in Belgium, sown in pots and grown in non-heated greenhouse conditions. We imposed drought on the seedlings in early summer by first watering the pots to saturation and then stopping any watering. Weight of the pots and stomatal conductance were regularly measured. Re-watering followed this drought period of 5 weeks. Height of the seedlings and apical bud development were observed. Stomatal resistance increased toward the end of the experiment in the drought-treated group and was restored after re-watering. The seedlings from the drought treatment displayed a higher probability to produce additional shoot growth after re-watering (p ≤ 0.05). A higher competition for water (two plants per pot) increased this chance. Although this chance was also higher for smaller seedlings, the actual length of the extra growth after re-watering was higher for larger seedlings (p ≤ 0.01). Both in the drought-treated and in the control group the autochthonous provenance growing on a xeric site produced less extra shoots compared to the two other provenances. Finally, stressed plants showed less developed apical buds compared to the control group after re-watering, suggesting a phenological effect on the growth cycle of oaks (p ≤ 0.0001). The higher chance for an extra shoot growth after the drought period can be considered as a compensation for the induced growth arrest during the drought period. PMID:26941760

  12. Early Summer Drought Stress During the First Growing Year Stimulates Extra Shoot Growth in Oak Seedlings (Quercus petraea)

    PubMed Central

    Turcsán, Arion; Steppe, Kathy; Sárközi, Edit; Erdélyi, Éva; Missoorten, Marc; Mees, Ghislain; Mijnsbrugge, Kristine V.

    2016-01-01

    More severe summer droughts are predicted for mid-latitudes in Europe. To evaluate the impact on forest ecosystems and more specifically on forest regeneration, we studied the response to summer drought in oak seedlings (Quercus petraea). Acorns were collected from different mother trees in three stands in Belgium, sown in pots and grown in non-heated greenhouse conditions. We imposed drought on the seedlings in early summer by first watering the pots to saturation and then stopping any watering. Weight of the pots and stomatal conductance were regularly measured. Re-watering followed this drought period of 5 weeks. Height of the seedlings and apical bud development were observed. Stomatal resistance increased toward the end of the experiment in the drought-treated group and was restored after re-watering. The seedlings from the drought treatment displayed a higher probability to produce additional shoot growth after re-watering (p ≤ 0.05). A higher competition for water (two plants per pot) increased this chance. Although this chance was also higher for smaller seedlings, the actual length of the extra growth after re-watering was higher for larger seedlings (p ≤ 0.01). Both in the drought-treated and in the control group the autochthonous provenance growing on a xeric site produced less extra shoots compared to the two other provenances. Finally, stressed plants showed less developed apical buds compared to the control group after re-watering, suggesting a phenological effect on the growth cycle of oaks (p ≤ 0.0001). The higher chance for an extra shoot growth after the drought period can be considered as a compensation for the induced growth arrest during the drought period. PMID:26941760

  13. Effect of extending the photoperiod with low-intensity red or far-red light on the timing of shoot elongation and flower-bud formation of 1-year-old Japanese pear (Pyrus pyrifolia).

    PubMed

    Ito, Akiko; Saito, Takanori; Nishijima, Takaaki; Moriguchi, Takaya

    2014-05-01

    To investigate the effects of light quality (wavelength) on shoot elongation and flower-bud formation in Japanese pear (Pyrus pyrifolia (Burm. f.) Nakai), we treated 1-year-old trees with the following: (i) 8 h sunlight + 16 h dark (SD); (ii) 8 h sunlight + 16 h red light (LD(SD + R)); or (iii) 8 h sunlight + 16 h far-red (FR) light (LD(SD + FR)) daily for 4 months from early April (before the spring flush) until early August in 2009 and 2010. In both years, shoot elongation stopped earlier in the LD(SD + FR) treatment than in the SD and LD(SD + R) treatments. After 4 months of treatments, 21% (2009) or 40% (2010) of LD(SD + FR)-treated trees formed flower buds in the shoot apices, whereas all the shoot apices from SD or LD(SD + R)-treated plants remained vegetative. With an additional experiment conducted in 2012, we confirmed that FR light at 730 nm was the most efficacious wavelength to induce flower-bud formation. Reverse transcription-quantitative polymerase chain reaction revealed that the expression of two floral meristem identity gene orthologues, LEAFY (PpLFY2a) and APETALA1 (PpMADS2-1a), were up-regulated in the shoot apex of LD(SD + FR). In contrast, the expression of a flowering repressor gene, TERMINAL FLOWER 1 (PpTFL1-1a, PpTFL1-2a), was down-regulated. In addition, expression of an orthologue of the flower-promoting gene FLOWERING LOCUS T (PpFT1a) was positively correlated with flower-bud formation, although the expression of another orthologue, PpFT2a, was negatively correlated with shoot growth. Biologically active cytokinin and gibberellic acid concentrations in shoot apices were reduced with LD(SD + FR) treatment. Taken together, our results indicate that pear plants are able to regulate flowering in response to the R : FR ratio. Furthermore, LD(SD + FR) treatment terminated shoot elongation and subsequent flower-bud formation in the shoot apex at an earlier time, possibly by influencing the expression of flowering-related genes and modifying

  14. The origin of the sporophyte shoot in land plants: a bryological perspective

    PubMed Central

    Ligrone, Roberto; Duckett, Jeffrey G.; Renzaglia, Karen S.

    2012-01-01

    Background Land plants (embryophytes) are monophyletic and encompass four major clades: liverworts, mosses, hornworts and polysporangiophytes. The liverworts are resolved as the earliest divergent lineage and the mosses as sister to a crown clade formed by the hornworts and polysporangiophytes (lycophytes, monilophytes and seed plants). Alternative topologies resolving the hornworts as sister to mosses plus polysporangiophytes are less well supported. Sporophyte development in liverworts depends only on embryonic formative cell divisions. A transient basal meristem contributes part of the sporophyte in mosses. The sporophyte body in hornworts and polysporangiophytes develops predominantly by post-embryonic meristematic activity. Scope This paper explores the origin of the sporophyte shoot in terms of changes in embryo organization. Pressure towards amplification of the sporangium-associated photosynthetic apparatus was a major driver of sporophyte evolution. Starting from a putative ancestral condition in which a transient basal meristem produced a sporangium-supporting seta, we postulate that in the hornwort–polysporangiophyte lineage the basal meristem acquired indeterminate meristematic activity and ectopically expressed the sporangium morphogenetic programme. The resulting sporophyte body plan remained substantially unaltered in hornworts, whereas in polysporangiophytes the persistent meristem shifted from a mid-embryo to a superficial position and was converted into an ancestral shoot apical meristem with the evolution of sequential vegetative and reproductive growth. Conclusions The sporophyte shoot is interpreted as a sterilized sporangial axis interpolated between the embryo and the fertile sporangium. With reference to the putatively ancestral condition found in mosses, the sporophyte body plans in hornworts and polysporangiophytes are viewed as the product of opposite heterochronic events, i.e. an anticipation and a delay, respectively, in the

  15. Histocytological analysis of yam (Dioscorea alata) shoot tips cryopreserved by encapsulation-dehydration.

    PubMed

    Barraco, Giuseppe; Sylvestre, Isabelle; Collin, Myriam; Escoute, Jacques; Lartaud, Marc; Verdeil, Jean-Luc; Engelmann, Florent

    2014-01-01

    In this work, we performed qualitative and quantitative observations of the cytological changes occurring in cells of yam (Dioscorea alata) in vitro shoot tips cryopreserved using the encapsulation-dehydration (E-D) technique. Shoot tip osmoprotection for 24 h in 1.25 M sucrose medium induced drastic changes in cellular cytological features, including high plasmolysis in all three cellular areas studied, the external cell layer (L1), one to three (L1-3) and seven to nine (L7-9) cell layers from the surface of the meristematic dome, pyknotic nuclei in meristematic area cells and disappearance of nucleoli. Nucleus size decreased significantly in all cellular areas studied. Nucleocytoplasmic ratio decreased significantly in L1-3 and L7-9 cells. Nuclear protein content increased, particularly in L1 and L1-3 cells. After physical dehydration, plasma membrane of numerous basal part cells was broken and intracellular soluble protein leakage was observed. Nucleus area and nucleocytoplasmic ratio decreased significantly in L7-9 cells. One week after cryopreservation, shoot tips showed regrowth and living cells had recovered their original morphology. In all cellular areas studied, nuclei had retrieved their original staining and nucleoli were visible. Original nucleus area values were recovered in L1-3 and L1 cells. The nucleocytoplasmic ratio retrieved its initial value in L1 cells but remained at levels observed after osmoprotection for L1-3 and L7-9 cells. The nuclear protein content had retrieved its original level. This investigation provided new insights in changes occurring in D. alata apices throughout an E-D protocol. PMID:23926078

  16. Responses of Arabidopsis and Wheat to Rising CO2 Depend on Nitrogen Source and Nighttime CO2 Levels1[OPEN

    PubMed Central

    Rachmilevitch, Shimon

    2015-01-01

    A major contributor to the global carbon cycle is plant respiration. Elevated atmospheric CO2 concentrations may either accelerate or decelerate plant respiration for reasons that have been uncertain. We recently established that elevated CO2 during the daytime decreases plant mitochondrial respiration in the light and protein concentration because CO2 slows the daytime conversion of nitrate (NO3−) into protein. This derives in part from the inhibitory effect of CO2 on photorespiration and the dependence of shoot NO3− assimilation on photorespiration. Elevated CO2 also inhibits the translocation of nitrite into the chloroplast, a response that influences shoot NO3− assimilation during both day and night. Here, we exposed Arabidopsis (Arabidopsis thaliana) and wheat (Triticum aestivum) plants to daytime or nighttime elevated CO2 and supplied them with NO3− or ammonium as a sole nitrogen (N) source. Six independent measures (plant biomass, shoot NO3−, shoot organic N, 15N isotope fractionation, 15NO3− assimilation, and the ratio of shoot CO2 evolution to O2 consumption) indicated that elevated CO2 at night slowed NO3− assimilation and thus decreased dark respiration in the plants reliant on NO3−. These results provide a straightforward explanation for the diverse responses of plants to elevated CO2 at night and suggest that soil N source will have an increasing influence on the capacity of plants to mitigate human greenhouse gas emissions. PMID:25755253

  17. Responses of Arabidopsis and wheat to rising CO2 depend on nitrogen source and nighttime CO2 levels.

    PubMed

    Asensio, Jose Salvador Rubio; Rachmilevitch, Shimon; Bloom, Arnold J

    2015-05-01

    A major contributor to the global carbon cycle is plant respiration. Elevated atmospheric CO2 concentrations may either accelerate or decelerate plant respiration for reasons that have been uncertain. We recently established that elevated CO2 during the daytime decreases plant mitochondrial respiration in the light and protein concentration because CO2 slows the daytime conversion of nitrate (NO3 (-)) into protein. This derives in part from the inhibitory effect of CO2 on photorespiration and the dependence of shoot NO3 (-) assimilation on photorespiration. Elevated CO2 also inhibits the translocation of nitrite into the chloroplast, a response that influences shoot NO3 (-) assimilation during both day and night. Here, we exposed Arabidopsis (Arabidopsis thaliana) and wheat (Triticum aestivum) plants to daytime or nighttime elevated CO2 and supplied them with NO3 (-) or ammonium as a sole nitrogen (N) source. Six independent measures (plant biomass, shoot NO3 (-), shoot organic N, (15)N isotope fractionation, (15)NO3 (-) assimilation, and the ratio of shoot CO2 evolution to O2 consumption) indicated that elevated CO2 at night slowed NO3 (-) assimilation and thus decreased dark respiration in the plants reliant on NO3 (-). These results provide a straightforward explanation for the diverse responses of plants to elevated CO2 at night and suggest that soil N source will have an increasing influence on the capacity of plants to mitigate human greenhouse gas emissions. PMID:25755253

  18. Starch Metabolism in Arabidopsis

    PubMed Central

    Streb, Sebastian; Zeeman, Samuel C.

    2012-01-01

    Starch is the major non-structural carbohydrate in plants. It serves as an important store of carbon that fuels plant metabolism and growth when they are unable to photosynthesise. This storage can be in leaves and other green tissues, where it is degraded during the night, or in heterotrophic tissues such as roots, seeds and tubers, where it is stored over longer time periods. Arabidopsis accumulates starch in many of its tissues, but mostly in its leaves during the day. It has proven to be a powerful genetic system for discovering how starch is synthesised and degraded, and new proteins and processes have been discovered. Such work has major significance for our starch crops, whose yield and quality could be improved by the application of this knowledge. Research into Arabidopsis starch metabolism has begun to reveal how its daily turnover is integrated into the rest of metabolism and adapted to the environmental conditions. Furthermore, Arabidopsis mutant lines deficient in starch metabolism have been employed as tools to study other biological processes ranging from sugar sensing to gravitropism and flowering time control. This review gives a detailed account of the use of Arabidopsis to study starch metabolism. It describes the major discoveries made and presents an overview of our understanding today, together with some as-yet unresolved questions. PMID:23393426

  19. Shooting direction and crosswell seismic data acquisition

    SciTech Connect

    Liner, C.L.; Bozkurt, G.; Cox, V.D.

    1994-12-31

    At the Glenn Pool field in Northeastern Oklahoma, a series of crosswell seismic surveys have been acquired. The acquisition parameters and shooting geometry were careful developed using a test survey. The first full survey resulted in high quality data, but the second encountered high ambient noise. The noise levels were high enough to prohibit first-arrival picking over in much of the data. Analysis of the data from the second survey shows that tube waves are emanating from the perforated interval in the receiver well. This is interpreted to be fluid flow or circulation noise through the perforations, even though the well was not flowing fluid at the surface. Since this image plane was important for characterization of the reservoir, the survey was re-shot by reversing sources and receivers in the two wells. The resulting high-quality data indicates that shooting direction can be an important acquisition factor.

  20. The Effects of Different Media on Shoot Proliferation From the Shoot Tip of Aloe vera L.

    PubMed Central

    Daneshvar, Mohammad Hosein; Moallemi, Noorolah; Abdolah Zadeh, Nazanin

    2013-01-01

    Background Aloe vera L. is an important pharmaceutical plant from which several medicinal and cosmetic compounds are extracted. Aloe is naturally propagated through offset, which is a slow and expensive labor cost method with low economical income. Objectives In this study, the effect of different media on shoot proliferation of the shoot tip of Aloe vera L. was investigated. Materials and Methods In vitro techniques are some of the suggested methods for rapid propagation of Aloe. In this experiment, the shoot tips of mother plants were grown in a greenhouse. After surface sterilization of the explants, they were cultured on Murashige and Skoog (1962) (MS) medium containing different concentrations of kinetin and naphthaleneacetic acid (NAA). The experiment was carried out in the form of a randomized complete design with three replications. Results The results showed that MS media containing 1.5 mg/L kinetin along with 0.15 or 0.3 mg/L NAA produced the highest percentage of proliferated shoots. In addition, the percentage of proliferated shoots in MS medium containing 2.0 or 2.5 mg/L benzylaminopurine (BAP) + 0.15 mg/L NAA was significantly higher than the other treatments. Conclusions Analysis of the interactive effects of NAA, kinetin and BAP on shoot proliferation showed that most of the proliferated shoots produced in MS medium containing 1.0 mg/L BAP + 1.0 mg/L kinetin + 0.15 mg/L NAA were significantly different from other treatments. Rooting quality was greater in MS media containing 1.0 mg/L IBA than a 1.0 mg/L NAA treatment. PMID:24624195

  1. Vitrification of Gladiolus shoot tips from cormels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gladiolus shoot tips, 1-2 mm, were excised from in vitro and greenhouse-grown cormels of cultivars ‘Peter Pears,’ in vitro-grown cormels of ‘Jenny Lee,’ field-grown cormels of the breeding lines 02-943A, 02-900, 02-926, and field-grown cormels of the cultivar ‘Double Delight.’ The highest frequency...

  2. Timing of growth inhibition following shoot inversion in Pharbitis nil

    NASA Technical Reports Server (NTRS)

    Abdel-Rahman, A. M.; Cline, M. G.

    1989-01-01

    Shoot inversion in Pharbitis nil results in the enhancement of ethylene production and in the inhibition of elongation in the growth zone of the inverted shoot. The initial increase in ethylene production previously was detected within 2 to 2.75 hours after inversion. In the present study, the initial inhibition of shoot elongation was detected within 1.5 to 4 hours with a weighted mean of 2.4 hours. Ethylene treatment of upright shoots inhibited elongation in 1.5 hours. A cause and effect relationship between shoot inversion-enhanced ethylene production and inhibition of elongation cannot be excluded.

  3. Chlordecone Transfer and Distribution in Maize Shoots.

    PubMed

    Pascal-Lorber, Sophie; Létondor, Clarisse; Liber, Yohan; Jamin, Emilien L; Laurent, François

    2016-01-20

    Chlordecone (CLD) is a persistent organic pollutant (POP) that was mainly used as an insecticide against banana weevils in the French West Indies (1972-1993). Transfer of CLD via the food chain is now the major mechanism for exposure of the population to CLD. The uptake and the transfer of CLD were investigated in shoots of maize, a C4 model plant growing under tropical climates, to estimate the exposure of livestock via feed. Maize plants were grown on soils contaminated with [(14)C]CLD under controlled conditions. The greatest part of the radioactivity was associated with roots, nearly 95%, but CLD was detected in whole shoots, concentrations in old leaves being higher than those in young ones. CLD was thus transferred from the base toward the plant top, forming an acropetal gradient of contaminant. In contrast, results evidenced the existence of a basipetal gradient of CLD concentration within leaves whose extremities accumulated larger amounts of CLD because of evapotranspiration localization. Extractable residues accounted for two-thirds of total residues both in roots and in shoots. This study highlighted the fact that the distribution of CLD contamination within grasses resulted from a conjunction between the age and evapotranspiration rate of tissues. CLD accumulation in fodder may be the main route of exposure for livestock. PMID:26701746

  4. Gravity-regulated gene expression in Arabidopsis thaliana

    NASA Astrophysics Data System (ADS)

    Sederoff, Heike; Brown, Christopher S.; Heber, Steffen; Kajla, Jyoti D.; Kumar, Sandeep; Lomax, Terri L.; Wheeler, Benjamin; Yalamanchili, Roopa

    Plant growth and development is regulated by changes in environmental signals. Plants sense environmental changes and respond to them by modifying gene expression programs to ad-just cell growth, differentiation, and metabolism. Functional expression of genes comprises many different processes including transcription, translation, post-transcriptional and post-translational modifications, as well as the degradation of RNA and proteins. Recently, it was discovered that small RNAs (sRNA, 18-24 nucleotides long), which are heritable and systemic, are key elements in regulating gene expression in response to biotic and abiotic changes. Sev-eral different classes of sRNAs have been identified that are part of a non-cell autonomous and phloem-mobile network of regulators affecting transcript stability, translational kinetics, and DNA methylation patterns responsible for heritable transcriptional silencing (epigenetics). Our research has focused on gene expression changes in response to gravistimulation of Arabidopsis roots. Using high-throughput technologies including microarrays and 454 sequencing, we iden-tified rapid changes in transcript abundance of genes as well as differential expression of small RNA in Arabidopsis root apices after minutes of reorientation. Some of the differentially regu-lated transcripts are encoded by genes that are important for the bending response. Functional mutants of those genes respond faster to reorientation than the respective wild type plants, indicating that these proteins are repressors of differential cell elongation. We compared the gravity responsive sRNAs to the changes in transcript abundances of their putative targets and identified several potential miRNA: target pairs. Currently, we are using mutant and transgenic Arabidopsis plants to characterize the function of those miRNAs and their putative targets in gravitropic and phototropic responses in Arabidopsis.

  5. Immunolocalization of integrin-like proteins in Arabidopsis and Chara

    NASA Technical Reports Server (NTRS)

    Katembe, W. J.; Swatzell, L. J.; Makaroff, C. A.; Kiss, J. Z.

    1997-01-01

    Integrins are a large family of integral plasma membrane proteins that link the extracellular matrix to the cytoskeleton in animal cells. As a first step in determining if integrin-like proteins are involved in gravitropic signal transduction pathways, we have used a polyclonal antibody against the chicken beta1 integrin subunit in western blot analyses and immunofluorescence microscopy to gain information on the size and location of these proteins in plants. Several different polypeptides are recognized by the anti-integrin antibody in roots and shoots of Arabidopsis and in the internodal cells and rhizoids of Chara. These cross-reactive polypeptides are associated with cellular membranes, a feature which is consistent with the known location of integrins in animal systems. In immunofluorescence studies of Arabidopsis roots, a strong signal was obtained from labeling integrin-like proteins in root cap cells, and there was little or no immunolabel in other regions of the root tip. While the antibody stained throughout Chara rhizoids, the highest density of immunolabel was at the tip. Thus, in both Arabidopsis roots and Chara rhizoids, the sites of gravity perception/transduction appear to be enriched in integrin-like molecules.

  6. Inactivation of two newly identified tobacco heavy metal ATPases leads to reduced Zn and Cd accumulation in shoots and reduced pollen germination

    PubMed Central

    Hermand, Victor; Julio, Emilie; Dorlhac de Borne, François; Punshon, Tracy; Ricachenevsky, Felipe K; Bellec, Arnaud; Gosti, Françoise; Berthomieu, Pierre

    2015-01-01

    Cadmium (Cd) is a non-essential heavy metal, which is classified as a “known human carcinogen” by the International Agency for Research on Cancer (IARC). Understanding the mechanisms controlling Cd distribution in planta is essential to develop phytoremediation approaches as well as for food safety. Unlike most other plants, tobacco (Nicotiana tabacum) plants translocate most of the Cd taken up from the soil, out of the roots and into the shoots, leading to high Cd accumulation in tobacco shoots. Two orthologs to the Arabidopsis thaliana HMA2 and HMA4 Zn and Cd ATPases that are responsible for zinc (Zn) and Cd translocation from roots to shoots were identified in tobacco and sequenced. These genes, named NtHMAα and NtHMAβ, were more highly expressed in roots than in shoots. NtHMAα was expressed in the vascular tissues of both roots and leaves as well as in anthers. No visual difference was observed between wild-type plants and plants in which the NtHMAα and NtHMAβ genes were either mutated or silenced. These mutants showed reduced Zn and Cd accumulation in shoots as well as increased Cd tolerance. When both NtHMA genes were silenced, plant development was altered and pollen germination was severely impaired due to Zn deficiency. Interestingly, seeds from these lines also showed decreased Zn concentration but increased iron (Fe) concentration. PMID:24760325

  7. Inactivation of two newly identified tobacco heavy metal ATPases leads to reduced Zn and Cd accumulation in shoots and reduced pollen germination.

    PubMed

    Hermand, Victor; Julio, Emilie; Dorlhac de Borne, François; Punshon, Tracy; Ricachenevsky, Felipe K; Bellec, Arnaud; Gosti, Françoise; Berthomieu, Pierre

    2014-08-01

    Cadmium (Cd) is a non-essential heavy metal, which is classified as a "known human carcinogen" by the International Agency for Research on Cancer (IARC). Understanding the mechanisms controlling Cd distribution in planta is essential to develop phytoremediation approaches as well as for food safety. Unlike most other plants, tobacco (Nicotiana tabacum) plants translocate most of the Cd taken up from the soil, out of the roots and into the shoots, leading to high Cd accumulation in tobacco shoots. Two orthologs of the Arabidopsis thaliana HMA2 and HMA4 Zn and Cd ATPases that are responsible for zinc (Zn) and Cd translocation from roots to shoots were identified in tobacco and sequenced. These genes, named NtHMAα and NtHMAβ, were more highly expressed in roots than in shoots. NtHMAα was expressed in the vascular tissues of both roots and leaves as well as in anthers. No visual difference was observed between wild-type plants and plants in which the NtHMAα and NtHMAβ genes were either mutated or silenced. These mutants showed reduced Zn and Cd accumulation in shoots as well as increased Cd tolerance. When both NtHMA genes were silenced, plant development was altered and pollen germination was severely impaired due to Zn deficiency. Interestingly, seeds from these lines also showed decreased Zn concentration but increased iron (Fe) concentration. PMID:24760325

  8. [Nonsurgical retreatment in a case of a radiolucent apical lesion].

    PubMed

    Vicente Gómez, A; Rodríguez Ponce, A

    1989-01-01

    We present a case of failure that was helpful solved without surgical endodontic treatment. We don't achieve clinical success besides endodontic treatment was twice remade. Finally we decided to put a temporary filling with calcium hydroxide and wait until apical radiolucency disappear and complete our treatment with gutta-percha, sealer and lateral condensation. PMID:2640036

  9. Echocardiographic assessment of takotsubo cardiomyopathy: beyond apical ballooning.

    PubMed

    Okura, Hiroyuki

    2016-03-01

    It has been >25 years since the first report of the takotsubo cardiomyopathy (TC). Although left ventriculography was originally used to depict its typical and impressive wall motion abnormality mimicking "takotsubo", or octopus pot, echocardiography plays a pivotal role in detecting not only its left ventricular (LV) wall motion abnormality, apical ballooning, but also various other findings. First of all, apical ballooning is not an essential finding for TC anymore. Mid-ventricular LV asynergy with or without apical involvement is a basic pattern of the LV wall motion abnormality. Distribution and time course of the asynergy may be best detected by echocardiography and echo provides useful information to differentiate between TC and acute coronary syndrome or acute myocarditis. In addition to the wall motion assessment, echo detects complications of TC such as systolic anterior motion of the mitral leaflet with or without LV outflow obstruction, mitral regurgitation, LV thrombus, right ventricular (RV) involvement. In particular, RV involvement is not an uncommon finding and is associated with worse short-term as well as long-term prognosis. Finally, coronary flow measurements and speckle tracking by echo may offer additional and useful information about pathophysiology and prognosis of TC. In conclusion, echocardiography is a standard imaging modality for detecting various dynamic findings beyond apical ballooning in patients with TC. PMID:26694809

  10. Osmotic stress at the barley root affects expression of circadian clock genes in the shoot.

    PubMed

    Habte, Ermias; Müller, Lukas M; Shtaya, Munqez; Davis, Seth J; von Korff, Maria

    2014-06-01

    The circadian clock is an important timing system that controls physiological responses to abiotic stresses in plants. However, there is little information on the effects of the clock on stress adaptation in important crops, like barley. In addition, we do not know how osmotic stress perceived at the roots affect the shoot circadian clock. Barley genotypes, carrying natural variation at the photoperiod response and clock genes Ppd-H1 and HvELF3, were grown under control and osmotic stress conditions to record changes in the diurnal expression of clock and stress-response genes and in physiological traits. Variation at HvELF3 affected the expression phase and shape of clock and stress-response genes, while variation at Ppd-H1 only affected the expression levels of stress genes. Osmotic stress up-regulated expression of clock and stress-response genes and advanced their expression peaks. Clock genes controlled the expression of stress-response genes, but had minor effects on gas exchange and leaf transpiration. This study demonstrated that osmotic stress at the barley root altered clock gene expression in the shoot and acted as a spatial input signal into the clock. Unlike in Arabidopsis, barley primary assimilation was less controlled by the clock and more responsive to environmental perturbations, such as osmotic stress. PMID:24895755

  11. Hormonal relations of radiation-induced tumors of Arabidopsis thaliana

    SciTech Connect

    Campell, B.R.; Persinger, S.M.; Town, C.D. )

    1989-04-01

    When gamma-irradiated Arabidopsis seed was germinated, tumors appeared on hypocotyls and apical meristems of the resulting plants. Several tumors have been cultured on hormone free medium for over two years since excision from the plants. The tumor lines display a range of phenotypes suggestive of abnormal hormone balance. To determine whether hormone overproduction or hypersensitivity is involved in tumorigenesis, we are measuring hormone levels in the tumor lines and characterizing their response to exogenously supplied growth regulators. Growth of two tumor lines is stimulated by either NAA or BAP, one is stimulated by NAA only, two by BAP only, and one is stimulated by neither. Growth of all lines tested thus far is inhibited by gibberellic acid, ethephon and ACC. The tumor lines appear more sensitive to ACC than normal callus tissue. Most tumors studied to date appear unlikely to have arisen due to increased hormone sensitivity. Experiments are in progress to determine auxin and cytokinin levels in the tumor lines.

  12. Bamboo shoots: a novel source of nutrition and medicine.

    PubMed

    Singhal, Poonam; Bal, Lalit Mohan; Satya, Santosh; Sudhakar, P; Naik, S N

    2013-01-01

    Bamboos, a group of large woody grasses belonging to the family Poaceae and subfamily Bambusoideae, are much talked about for their contribution to the environment. However, the food potential of Bamboo shoot per se remains unexploited. Literature on the nutritional and medicinal potential of bamboo shoots is scarce. This paper therefore provides insight on bamboo shoot as a food resource. Various edible species and exotic food products (fermented shoots, pickle, etc.) and recipes of bamboo shoots (bamboo beer, bamboo cookies) are consumed worldwide. Change in nutritional composition of different species of bamboo shoots with processing has also been reviewed. Bamboo shoots possess high protein, moderate fiber, and less fat content. They are also endowed for having essential amino acids, selenium, a potent antioxidant, and potassium, a healthy heart mineral. Occurrence of taxiphyllin, a cyanogenic glycoside in raw shoots, and its side effect on human health calls for the demand to innovate processing ways using scientific input to eliminate the toxic compound without disturbing the nutrient reserve. Lastly, the paper also reviews the utilization of medicinal properties acquired by bamboo shoot. Using the traditional knowledge, pharmaceutical preparations of bamboo shoots like bamboo salt, bamboo vinegar, bamboo extracts for diabetes and cholesterol control, etc. are now gaining importance. Further investigation is required by the researchers to make novel nutraceutical products and benefit the society. PMID:23391018

  13. An Atypical Case of Apical Hypertrophic Cardiomyopathy: Absence of Giant T Waves in spite of Extreme Apical Wall Hypertrophy.

    PubMed

    Sanidas, Elias; Bonou, Maria; Anastasiadis, Georgios; Tzanis, Georgios; Barbetseas, John

    2015-01-01

    Apical hypertrophic cardiomyopathy is an uncommon variant of hypertrophic cardiomyopathy, with hypertrophy mainly affecting the apex of the left ventricle. We hereby describe a case of an octogenarian female patient who was randomly diagnosed with AHCM due to other comorbidities. PMID:26779351

  14. An Atypical Case of Apical Hypertrophic Cardiomyopathy: Absence of Giant T Waves in spite of Extreme Apical Wall Hypertrophy

    PubMed Central

    Sanidas, Elias; Bonou, Maria; Anastasiadis, Georgios; Tzanis, Georgios; Barbetseas, John

    2015-01-01

    Apical hypertrophic cardiomyopathy is an uncommon variant of hypertrophic cardiomyopathy, with hypertrophy mainly affecting the apex of the left ventricle. We hereby describe a case of an octogenarian female patient who was randomly diagnosed with AHCM due to other comorbidities. PMID:26779351

  15. The CUC1 and CUC2 genes promote carpel margin meristem formation during Arabidopsis gynoecium development

    PubMed Central

    Kamiuchi, Yuri; Yamamoto, Kayo; Furutani, Masahiko; Tasaka, Masao; Aida, Mitsuhiro

    2014-01-01

    Carpel margin meristems (CMMs), a pair of meristematic tissues present along the margins of two fused carpel primordia of Arabidopsis thaliana, are essential for the formation of ovules and the septum, two major internal structures of the gynoecium. Although a number of regulatory factors involved in shoot meristem activity are known to be required for the formation of these gynoecial structures, their direct roles in CMM development have yet to be addressed. Here we show that the CUP-SHAPED COTYLEDON genes CUC1 and CUC2, which are essential for shoot meristem initiation, are also required for formation and stable positioning of the CMMs. Early in CMM formation, CUC1 and CUC2 are also required for expression of the SHOOT MERISTEMLESS gene, a central regulator for stem cell maintenance in the shoot meristem. Moreover, plants carrying miR164-resistant forms of CUC1 and CUC2 resulted in extra CMM activity with altered positioning. Our results thus demonstrate that the two regulatory proteins controlling shoot meristem activity also play critical roles in elaboration of the female reproductive organ through the control of meristematic activity. PMID:24817871

  16. Phytochrome-Mediated Light Regulation of PHYA- and PHYB-GUS Transgenes in Arabidopsis thaliana Seedlings.

    PubMed Central

    Somers, D. E.; Quail, P. H.

    1995-01-01

    Phytochrome wild-type gene-[beta]-glucuronidase (PHY-GUS) gene fusions were used in transgenic Arabidopsis to compare the activity levels and light regulation of the PHYA and PHYB promoters and to identify the photoreceptors mediating this regulation. In dark-grown seedlings, both promoters are 4-fold more active in shoots than in roots,but the PHYA promoter is nearly 20-fold more active than that of PHYB in both organs. In shoots, white light represses the activities of the PHYA and PHYB promoters 10- and 2-fold, respectively, whereas in roots light has no effect on the PHYA promoter but increases PHYB promoter activity 2-fold. Consequently, PHYA promoter activity remains higher than that of PHYB in light in both shoots (5-fold) and roots (11-fold). Experiments with narrow-waveband light and photomorphogenic mutants suggest that no single photoreceptor is necessary for full white-light-directed PHYA repression in shoots, but that multiple, independent photoreceptor pathways are sufficient alone or in combination. In contrast, phytochrome B appears both necessary and sufficient for a light-mediated decrease in PHYB activity in shoots, and phytochrome A mediates a far-red-light-stimulated increase in PHYB promoter activity. Together, the data indicate that the PHYA and PHYB genes are regulated in divergent fashion at the transcriptional level, both developmentally and by the spectral distribution of the prevailing light, and that this regulation may be important to the photosensory function of the two photoreceptors. PMID:12228380

  17. Trichome morphogenesis in Arabidopsis.

    PubMed Central

    Schwab, B; Folkers, U; Ilgenfritz, H; Hülskamp, M

    2000-01-01

    Trichomes (plant hairs) in Arabidopsis thaliana are large non-secreting epidermal cells with a characteristic three-dimensional architecture. Because trichomes are easily accessible to a combination of genetic, cell biological and molecular methods they have become an ideal model system to study various aspects of plant cell morphogenesis. In this review we will summarize recent progress in the understanding of trichome morphogenesis. PMID:11128981

  18. Growth rate distribution in the forming lateral root of arabidopsis

    PubMed Central

    Szymanowska-Pułka, Joanna; Lipowczan, Marcin

    2014-01-01

    Background and Aims Microscopic observations of lateral roots (LRs) in Arabidopsis thaliana reveal that the cross-sectional shape of the organ changes from its basal to its apical region. The founder cells for LRs are elongated along the parent root axis, and thus from the site of initiation the base of LRs resemble an ellipse. The circumference of the apical part of LRs is usually a circle. The objective of this study was to analyse the characteristics of changes in the growth field of LRs possessing various shapes in their basal regions. Methods The LRs of the wild type (Col-0) and two transgenic arabidopsis lines were analysed. On the basis of measurements of the long and short diameters (DL and DS, respectively) of the ellipse-like figure representing the bases of particular LRs, their asymmetry ratios (DL/DS) were determined. Possible differences between accessions were analysed by applying statistical methods. Key Results No significant differences between accessions were detected. Comparisons were therefore made of the maximal, minimal and mean value of the ratio of all the LRs analysed. Taking into consideration the lack of circular symmetry of the basal part, rates of growth were determined at selected points on the surface of LRs by the application of the growth tensor method, a mathematical tool previously applied only to describe organs with rotational symmetry. Maps showing the distribution of growth rates were developed for surfaces of LRs of various asymmetry ratios. Conclusions The maps of growth rates on the surfaces of LRs having various shapes of the basal part show differences in both the geometry and the manner of growth, thus indicating that the manner of growth of the LR primordium is correlated to its shape. This is the first report of a description of growth of an asymmetric plant organ using the growth tensor method. The mathematical modelling adopted in the study provides new insights into plant organ formation and shape. PMID:25108392

  19. Maize LAZY1 Mediates Shoot Gravitropism and Inflorescence Development through Regulating Auxin Transport, Auxin Signaling, and Light Response1[C][W

    PubMed Central

    Dong, Zhaobin; Jiang, Chuan; Chen, Xiaoyang; Zhang, Tao; Ding, Lian; Song, Weibin; Luo, Hongbing; Lai, Jinsheng; Chen, Huabang; Liu, Renyi; Zhang, Xiaolan; Jin, Weiwei

    2013-01-01

    Auxin is a plant hormone that plays key roles in both shoot gravitropism and inflorescence development. However, these two processes appear to be parallel and to be regulated by distinct players. Here, we report that the maize (Zea mays) prostrate stem1 mutant, which is allelic to the classic mutant lazy plant1 (la1), displays prostrate growth with reduced shoot gravitropism and defective inflorescence development. Map-based cloning identified maize ZmLA1 as the functional ortholog of LAZY1 in rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana). It has a unique role in inflorescence development and displays enriched expression in reproductive organs such as tassels and ears. Transcription of ZmLA1 responds to auxin and is repressed by light. Furthermore, ZmLA1 physically interacts with a putative auxin transport regulator in the plasma membrane and a putative auxin signaling protein in the nucleus. RNA-SEQ data showed that dozens of auxin transport, auxin response, and light signaling genes were differentially expressed in la1 mutant stems. Therefore, ZmLA1 might mediate the cross talk between shoot gravitropism and inflorescence development by regulating auxin transport, auxin signaling, and probably light response in maize. PMID:24089437

  20. Apical organs in echinoderm larvae: insights into larval evolution in the Ambulacraria.

    PubMed

    Byrne, Maria; Nakajima, Yoko; Chee, Francis C; Burke, Robert D

    2007-01-01

    The anatomy and cellular organization of serotonergic neurons in the echinoderm apical organ exhibits class-specific features in dipleurula-type (auricularia, bipinnaria) and pluteus-type (ophiopluteus, echinopluteus) larvae. The apical organ forms in association with anterior ciliary structures. Apical organs in dipleurula-type larvae are more similar to each other than to those in either of the pluteus forms. In asteroid bipinnaria and holothuroid auricularia the apical organ spans ciliary band sectors that traverse the anterior-most end of the larvae. The asteroid apical organ also has prominent bilateral ganglia that connect with an apical network of neurites. The simple apical organ of the auricularia is similar to that in the hemichordate tornaria larva. Apical organs in pluteus forms differ markedly. The echinopluteus apical organ is a single structure on the oral hood between the larval arms comprised of two groups of cells joined by a commissure and its cell bodies do not reside in the ciliary band. Ophioplutei have a pair of lateral ganglia associated with the ciliary band of larval arms that may be the ophiuroid apical organ. Comparative anatomy of the serotonergic nervous systems in the dipleurula-type larvae of the Ambulacraria (Echinodermata+Hemichordata) suggests that the apical organ of this deuterostome clade originated as a simple bilaterally symmetric nerve plexus spanning ciliary band sectors at the anterior end of the larva. From this structure, the apical organ has been independently modified in association with the evolution of class-specific larval forms. PMID:17845515

  1. Qualitative inheritance of water-stress induced apical sterility in wheat (Triticum aestivum).

    PubMed

    Mohammady-D, Shahram; Moore, Keith; Ollerenshaw, John

    2003-01-01

    Grain number per unit area is an effective component of grain yield in bread wheat. Water-stress induced apical sterility (tip sterility) reduces the number of grains and, consequently, the grain yield in semi-arid regions with a shortage of available water during the pre-anthesis period. Crosses between apical sterile and apical fertile varieties and selection lines were made and F1, BC1, and F2 populations were subjected to moderate water-stress to study the inheritance of this character. The F2 and BC1 plants were qualitatively categorised into two phenotypes and tested for monohybrid and dihybrid segregation hypotheses. All the spikes of F1 plants obtained from crosses between apical fertile and apical sterile varieties were fully fertile indicating apical fertility is dominant to apical sterility. The F2 segregation Results from crosses between apical fertile lines and Y82187 suggested two complementary dominant genes segregating independently were involved in tolerance to water-stress induced apical sterility. In other words, two dominant genes determine apical fertility in these crosses and if one of these loci is homozygous, recessive waterstress will induce apical sterility. One F2 population segregated for both apical sterility and vernalisation response. Semi-winter plants had more sterile spikelets and the result of chi-square test confirmed monhybrid segregation for vernalisation response. PMID:14641489

  2. The molecular path to in vitro shoot regeneration.

    PubMed

    Motte, Hans; Vereecke, Danny; Geelen, Danny; Werbrouck, Stefaan

    2014-01-01

    Plant regeneration through de novo shoot organogenesis in tissue culture is a critical step in most plant transformation and micropropagation procedures. Establishing an efficient regeneration protocol is an empirical process and requires optimization of multiple factors that influence the regeneration capacity. Here, we review the molecular process of shoot induction in a two-step regeneration protocol and focus on the role of auxins and cytokinins. First, during incubation on an auxin-rich callus induction medium (CIM), organogenic callus is produced that exhibits characteristics of a root meristem. Subsequent incubation on a cytokinin-rich shoot induction medium (SIM) induces root to shoot conversion. Through a detailed analysis of the different aspects of shoot regeneration, we try to reveal hinge points and novel candidate genes that may be targeted to increase shoot regeneration capacity in order to improve transformation protocols. PMID:24355763

  3. Opposite metabolic responses of shoots and roots to drought

    NASA Astrophysics Data System (ADS)

    Gargallo-Garriga, Albert; Sardans, Jordi; Pérez-Trujillo, Míriam; Rivas-Ubach, Albert; Oravec, Michal; Vecerova, Kristyna; Urban, Otmar; Jentsch, Anke; Kreyling, Juergen; Beierkuhnlein, Carl; Parella, Teodor; Peñuelas, Josep

    2014-10-01

    Shoots and roots are autotrophic and heterotrophic organs of plants with different physiological functions. Do they have different metabolomes? Do their metabolisms respond differently to environmental changes such as drought? We used metabolomics and elemental analyses to answer these questions. First, we show that shoots and roots have different metabolomes and nutrient and elemental stoichiometries. Second, we show that the shoot metabolome is much more variable among species and seasons than is the root metabolome. Third, we show that the metabolic response of shoots to drought contrasts with that of roots; shoots decrease their growth metabolism (lower concentrations of sugars, amino acids, nucleosides, N, P, and K), and roots increase it in a mirrored response. Shoots are metabolically deactivated during drought to reduce the consumption of water and nutrients, whereas roots are metabolically activated to enhance the uptake of water and nutrients, together buffering the effects of drought, at least at the short term.

  4. Transgenic apple (Malus x domestica) shoot showing low browning potential.

    PubMed

    Murata, M; Haruta, M; Murai, N; Tanikawa, N; Nishimura, M; Homma, S; Itoh, Y

    2000-11-01

    Transgenic apple shoots were prepared from leaf disks by using Agrobacterium tumefaciens carrying the kanamycin (KM) resistance gene and antisense polyphenol oxidase (PPO) DNA. Four transgenic apple lines that grew on the medium containing 50 microgram/mL KM were obtained. They contained the KM resistance gene and grew stably on the medium for >3 years. Two transgenic shoot lines containing antisense PPO DNA in which PPO activity was repressed showed a lower browning potential than a control shoot. PMID:11087467

  5. Regulation of Meristem Morphogenesis by Cell Wall Synthases in Arabidopsis.

    PubMed

    Yang, Weibing; Schuster, Christoph; Beahan, Cherie T; Charoensawan, Varodom; Peaucelle, Alexis; Bacic, Antony; Doblin, Monika S; Wightman, Raymond; Meyerowitz, Elliot M

    2016-06-01

    The cell walls of the shoot apical meristem (SAM), containing the stem cell niche that gives rise to the above-ground tissues, are crucially involved in regulating differentiation. It is currently unknown how these walls are built and refined or their role, if any, in influencing meristem developmental dynamics. We have combined polysaccharide linkage analysis, immuno-labeling, and transcriptome profiling of the SAM to provide a spatiotemporal plan of the walls of this dynamic structure. We find that meristematic cells express only a core subset of 152 genes encoding cell wall glycosyltransferases (GTs). Systemic localization of all these GT mRNAs by in situ hybridization reveals members with either enrichment in or specificity to apical subdomains such as emerging flower primordia, and a large class with high expression in dividing cells. The highly localized and coordinated expression of GTs in the SAM suggests distinct wall properties of meristematic cells and specific differences between newly forming walls and their mature descendants. Functional analysis demonstrates that a subset of CSLD genes is essential for proper meristem maintenance, confirming the key role of walls in developmental pathways. PMID:27212401

  6. Shooting direction and crosswell seismic data acquisition

    SciTech Connect

    Liner, C.L.; Bozkurt, G.; Cox, V.D.

    1996-09-01

    Four crosswell seismic surveys were acquired in the Glenn Pool Field of northeastern Oklahoma as part of a multidisciplinary reservoir characterization project. The acquisition goal was to generate data suitable for tomographic traveltime inversion. Acquisition parameters and shooting geometry were selected by conducting a parameter test at the site. Following the parameter test, the first survey resulted in high quality data showing clear first arrivals, low ambient noise, some reflection events, and strong source-generated tube waves. The second survey involved a different receiver well and encountered high ambient noise levels. The noise was strong enough to prohibit first-arrival picking for much of the data. On-site analysis of the second survey revealed tube waves emanating from a perforated interval in the receiver well. This well was shut in and was not flowing fluid or gas at the surface. They interpret the source of ambient tube waves as borehole-to-formation fluid flow (circulation) associated with the perforations. Since this image plane was important for characterization of the reservoir, the survey was reshot (third survey) by reversing sources and receivers in the two wells. The resulting high-quality data indicates that shooting direction can be an important factor in crosswell seismic acquisition. This experience influenced acquisition of a previously planned fourth survey so that the ambient noise problem would be avoided.

  7. Defective apical extrusion signaling contributes to aggressive tumor hallmarks.

    PubMed

    Gu, Yapeng; Shea, Jill; Slattum, Gloria; Firpo, Matthew A; Alexander, Margaret; Mulvihill, Sean J; Golubovskaya, Vita M; Rosenblatt, Jody

    2015-01-01

    When epithelia become too crowded, some cells are extruded that later die. To extrude, a cell produces the lipid, Sphingosine 1-Phosphate (S1P), which activates S1P₂ receptors in neighboring cells that seamlessly squeeze the cell out of the epithelium. Here, we find that extrusion defects can contribute to carcinogenesis and tumor progression. Tumors or epithelia lacking S1P₂ cannot extrude cells apically and instead form apoptotic-resistant masses, possess poor barrier function, and shift extrusion basally beneath the epithelium, providing a potential mechanism for cell invasion. Exogenous S1P₂ expression is sufficient to rescue apical extrusion, cell death, and reduce orthotopic pancreatic tumors and their metastases. Focal Adhesion Kinase (FAK) inhibitor can bypass extrusion defects and could, therefore, target pancreatic, lung, and colon tumors that lack S1P₂ without affecting wild-type tissue. PMID:25621765

  8. Apical versus Basal Neurogenesis Directs Cortical Interneuron Subclass Fate.

    PubMed

    Petros, Timothy J; Bultje, Ronald S; Ross, M Elizabeth; Fishell, Gord; Anderson, Stewart A

    2015-11-10

    Fate determination in the mammalian telencephalon, with its diversity of neuronal subtypes and relevance to neuropsychiatric disease, remains a critical area of study in neuroscience. Most studies investigating this topic focus on the diversity of neural progenitors within spatial and temporal domains along the lateral ventricles. Often overlooked is whether the location of neurogenesis within a fate-restricted domain is associated with, or instructive for, distinct neuronal fates. Here, we use in vivo fate mapping and the manipulation of neurogenic location to demonstrate that apical versus basal neurogenesis influences the fate determination of major subgroups of cortical interneurons derived from the subcortical telencephalon. Somatostatin-expressing interneurons arise mainly from apical divisions along the ventricular surface, whereas parvalbumin-expressing interneurons originate predominantly from basal divisions in the subventricular zone. As manipulations that shift neurogenic location alter interneuron subclass fate, these results add an additional dimension to the spatial-temporal determinants of neuronal fate determination. PMID:26526999

  9. Modelling apical constriction in epithelia using elastic shell theory.

    PubMed

    Jones, Gareth Wyn; Chapman, S Jonathan

    2010-06-01

    Apical constriction is one of the fundamental mechanisms by which embryonic tissue is deformed, giving rise to the shape and form of the fully-developed organism. The mechanism involves a contraction of fibres embedded in the apical side of epithelial tissues, leading to an invagination or folding of the cell sheet. In this article the phenomenon is modelled mechanically by describing the epithelial sheet as an elastic shell, which contains a surface representing the continuous mesh formed from the embedded fibres. Allowing this mesh to contract, an enhanced shell theory is developed in which the stiffness and bending tensors of the shell are modified to include the fibres' stiffness, and in which the active effects of the contraction appear as body forces in the shell equilibrium equations. Numerical examples are presented at the end, including the bending of a plate and a cylindrical shell (modelling neurulation) and the invagination of a spherical shell (modelling simple gastrulation). PMID:19859751

  10. Transient apical dyskinesia with a pacemaker: Electrocardiographic features.

    PubMed

    Núñez-Gil, Iván J; Feltes, Gisela I; Mejía-Rentería, Hernán D; Biagioni, Corina; De Agustín, J Alberto; Vivas, David; Fernández-Ortiz, Antonio

    2015-04-01

    Transient apical dyskinesia syndromes present features similar to acute coronary syndromes, but with normal coronary arteries and rapid complete resolution of wall motion alterations. We report the case of a 73-year-old woman who was admitted to hospital because of typical chest pain at rest after her brother's death. She had had a pacemaker implanted in 2001. Troponin levels were elevated and apical hypokinesia was shown by ventriculography and echocardiography, with normal coronary arteries. Evolving ECG alterations were observed in spite of the continued pacing rhythm. All these alterations were fully resolved after discharge. This case shows that, even in the presence of a pacemaker, evolving ECG alterations can be observed in Takotsubo syndrome. PMID:25840647

  11. Apical pressures developed by needles for canal irrigation.

    PubMed

    Bradford, C E; Eleazer, P D; Downs, K E; Scheetz, J P

    2002-04-01

    Drying instrumented canals with pressurized air may result in patient morbidity or even fatality. Low pressure and side vent needles have been suggested to lessen the danger. This study observed apical pressures from different needles inserted deeply into small round and ovoid canals as instrumentation progressed. Low-pressure (5 psi) air was injected through the needles, and apical pressures were recorded after each instrument. Pressures varied greatly within each test group. Generalities that can be drawn are that binding the needle within the canal gives higher pressures than with the needle slightly short of binding and that pressures were higher with apexes instrumented to size 30 and higher. With the needle tightly bound, neither needle size, needle design, nor canal shape resulted in statistically significant mean pressure differences. With the needle slightly withdrawn, larger bore needles gave higher pressures than small diameter needles. Caution is advised with the clinical use of pressurized air in the drying of root canals. PMID:12043877

  12. Diurnal Changes in Mitochondrial Function Reveal Daily Optimization of Light and Dark Respiratory Metabolism in Arabidopsis*

    PubMed Central

    Lee, Chun Pong; Eubel, Holger; Millar, A. Harvey

    2010-01-01

    Biomass production by plants is often negatively correlated with respiratory rate, but the value of this rate changes dramatically during diurnal cycles, and hence, biomass is the cumulative result of complex environment-dependent metabolic processes. Mitochondria in photosynthetic plant tissues undertake substantially different metabolic roles during light and dark periods that are dictated by substrate availability and the functional capacity of mitochondria defined by their protein composition. We surveyed the heterogeneity of the mitochondrial proteome and its function during a typical night and day cycle in Arabidopsis shoots. This used a staged, quantitative analysis of the proteome across 10 time points covering 24 h of the life of 3-week-old Arabidopsis shoots grown under 12-h dark and 12-h light conditions. Detailed analysis of enzyme capacities and substrate-dependent respiratory processes of isolated mitochondria were also undertaken during the same time course. Together these data reveal a range of dynamic changes in mitochondrial capacity and uncover day- and night-enhanced protein components. Clear diurnal changes were evident in mitochondrial capacities to drive the TCA cycle and to undertake functions associated with nitrogen and sulfur metabolism, redox poise, and mitochondrial antioxidant defense. These data quantify the nature and nuances of a daily rhythm in Arabidopsis mitochondrial respiratory capacity. PMID:20601493

  13. Effects of long-term hypergravity treatment on the development of inflorescence stems of arabidopsis

    NASA Astrophysics Data System (ADS)

    Karahara, Ichirou; Tamaoki, Daisuke; Kamisaka, Seiichiro; Yamaguchi, Takashi; Shinohara, Hironori; Kume, Atsushi; Inoue, Hiroshi

    Hypergravity experiments with plants have been mostly performed using a commercial centrifuge in the dark. In order to see longer-term effect of hypergravity on the development of plant shoots, however, it is necessary to carry out the experiments in the light. In the present study, we have set up a centrifuge equipped with lighting system, which supports long-term plant growth under hypergravity condition, in order to see long-term effects of hypergravity on the development of vascular tissues of inflorescence stems. Arabidopsis plants (Arabidopsis thaliana (L.) Heynh., Col-0), which were grown under 1 G conditions for 20-23 days and having the first visible flower bud, i.e., at Arabidopsis growth stage number 5 (according to Boys et al., 2001), were selected as the plant material. These plants were exposed to hypergravity stimulus at 10 G in a direction from the shoot to root for 10 days in the continuous light. Effects of hypergravity on growth of inflorescence stems, lignin content, and morphometrical parameters of the stem tissues were examined. As a result, the length of the inflorescence stem was decreased. Cross sectional area as well as cell number, and lignin content in the stem were increased under hypergravity. The length of basal internodes of the stem was decreased under hypergravity. In conclusion, the inflorescence stem was suggested to be strengthened through changes in its morphological characteristics as well as lignin deposition under long-term hypergravity conditions.

  14. Flavonols Accumulate Asymmetrically and Affect Auxin Transport in Arabidopsis1[C][W][OA

    PubMed Central

    Kuhn, Benjamin M.; Geisler, Markus; Bigler, Laurent; Ringli, Christoph

    2011-01-01

    Flavonoids represent a class of secondary metabolites with diverse functions in plants including ultraviolet protection, pathogen defense, and interspecies communication. They are also known as modulators of signaling processes in plant and animal systems and therefore are considered to have beneficial effects as nutraceuticals. The rol1-2 (for repressor of lrx1) mutation of Arabidopsis (Arabidopsis thaliana) induces aberrant accumulation of flavonols and a cell-growth phenotype in the shoot. The hyponastic cotyledons, aberrant shape of pavement cells, and deformed trichomes in rol1-2 mutants are suppressed by blocking flavonoid biosynthesis, suggesting that the altered flavonol accumulation in these plants induces the shoot phenotype. Indeed, the identification of several transparent testa, myb, and fls1 (for flavonol synthase1) alleles in a rol1-2 suppressor screen provides genetic evidence that flavonols interfere with shoot development in rol1-2 seedlings. The increased accumulation of auxin in rol1-2 seedlings appears to be caused by a flavonol-induced modification of auxin transport. Quantification of auxin export from mesophyll protoplasts revealed that naphthalene-1-acetic acid but not indole-3-acetic acid transport is affected by the rol1-2 mutation. Inhibition of flavonol biosynthesis in rol1-2 fls1-3 restores naphthalene-1-acetic acid transport to wild-type levels, indicating a very specific mode of action of flavonols on the auxin transport machinery. PMID:21502189

  15. Apical ABC transporters and cancer chemotherapeutic drug disposition.

    PubMed

    Durmus, Selvi; Hendrikx, Jeroen J M A; Schinkel, Alfred H

    2015-01-01

    ATP-binding cassette (ABC) transporters are transmembrane efflux transporters that mediate cellular extrusion of a broad range of substrates ranging from amino acids, lipids, and ions to xenobiotics including many anticancer drugs. ABCB1 (P-GP) and ABCG2 (BCRP) are the most extensively studied apical ABC drug efflux transporters. They are highly expressed in apical membranes of many pharmacokinetically relevant tissues such as epithelial cells of the small intestine and endothelial cells of the blood capillaries in brain and testis, and in the placental maternal-fetal barrier. In these tissues, they have a protective function as they efflux their substrates back to the intestinal lumen or blood and thus restrict the intestinal uptake and tissue disposition of many compounds. This presents a major challenge for the use of many (anticancer) drugs, as most currently used anticancer drugs are substrates of these transporters. Herein, we review the latest findings on the role of apical ABC transporters in the disposition of anticancer drugs. We discuss that many new, rationally designed anticancer drugs are substrates of these transporters and that their oral availability and/or brain disposition are affected by this interaction. We also summarize studies that investigate the improvement of oral availability and brain disposition of many cytotoxic (e.g., taxanes) and rationally designed (e.g., tyrosine kinase inhibitor) anticancer drugs, using chemical inhibitors of these transporters. These findings provide a better understanding of the importance of apical ABC transporters in chemotherapy and may therefore advance translation of promising preclinical insights and approaches to clinical studies. PMID:25640265

  16. Apical transporters for neutral amino acids: physiology and pathophysiology.

    PubMed

    Bröer, Stefan

    2008-04-01

    Absorption of amino acids in kidney and intestine involves a variety of transporters for different groups of amino acids. This is illustrated by inherited disorders of amino acid absorption, such as Hartnup disorder, cystinuria, iminoglycinuria, dicarboxylic aminoaciduria, and lysinuric protein intolerance, affecting separate groups of amino acids. Recent advances in the molecular identification of apical neutral amino acid transporters has shed a light on the molecular basis of Hartnup disorder and iminoglycinuria. PMID:18400692

  17. Multiple shoot regeneration and effect of sugars on growth and nitidine accumulation in shoot cultures of Toddalia asiatica

    PubMed Central

    Praveena, Chinthala; Veeresham, Ciddi

    2014-01-01

    Background: Toddalia asiatica (Rutaceae) is an important medicinal plant in traditional medicinal system of India and China. Nitidine production from callus cultures of the plant had been investigated, but in vitro multiplication and secondary metabolite production from shoot cultures is not reported. Objective: The aim of the present work is to establish protocol for in vitro multiple shoot regeneration of T. asiatica and to investigate the secondary metabolite, nitidine production from the shoot cultures. Materials and Methods: Different explants were used for shoot regeneration on MS supplemented with benzyl adenine (BA) either alone or in combination with naphthalene acetic acid (NAA) in different combinations. Effect of different sugars and different concentrations of sucrose on biomass accumulation in shoot cultures in liquid medium was investigated. For in vitro rooting, shoots culture were inoculated to half strength MS medium supplemented with different concentrations of indole butyric acid. Quantitative analysis of shoot culture extracts was done for estimation of nitidine by HPTLC. Results: Shoot cultures were successfully initiated and established from nodal and shoot tip explants on MS medium supplemented with benzyl adenine and sucrose (3% w/v). Sucrose at a concentration of 3 % w/v was found to be optimum for growth and biomass accumulation. In vitro rooting of shoots was achieved on half strength MS medium supplemented with indole butyric acid 3 mg/l. Investigation of secondary metabolite production ability of the in vitro regenerated shoot cultures revealed their ability to biosynthesize nitidine. Conclusion: Shoot cultures were established and nitidine production has been observed. PMID:25298663

  18. Transcription Factor Arabidopsis Activating Factor1 Integrates Carbon Starvation Responses with Trehalose Metabolism1[OPEN

    PubMed Central

    Garapati, Prashanth; Feil, Regina; Lunn, John Edward; Van Dijck, Patrick; Balazadeh, Salma; Mueller-Roeber, Bernd

    2015-01-01

    Plants respond to low carbon supply by massive reprogramming of the transcriptome and metabolome. We show here that the carbon starvation-induced NAC (for NO APICAL MERISTEM/ARABIDOPSIS TRANSCRIPTION ACTIVATION FACTOR/CUP-SHAPED COTYLEDON) transcription factor Arabidopsis (Arabidopsis thaliana) Transcription Activation Factor1 (ATAF1) plays an important role in this physiological process. We identified TREHALASE1, the only trehalase-encoding gene in Arabidopsis, as a direct downstream target of ATAF1. Overexpression of ATAF1 activates TREHALASE1 expression and leads to reduced trehalose-6-phosphate levels and a sugar starvation metabolome. In accordance with changes in expression of starch biosynthesis- and breakdown-related genes, starch levels are generally reduced in ATAF1 overexpressors but elevated in ataf1 knockout plants. At the global transcriptome level, genes affected by ATAF1 are broadly associated with energy and carbon starvation responses. Furthermore, transcriptional responses triggered by ATAF1 largely overlap with expression patterns observed in plants starved for carbon or energy supply. Collectively, our data highlight the existence of a positively acting feedforward loop between ATAF1 expression, which is induced by carbon starvation, and the depletion of cellular carbon/energy pools that is triggered by the transcriptional regulation of downstream gene regulatory networks by ATAF1. PMID:26149570

  19. Transcription Factor Arabidopsis Activating Factor1 Integrates Carbon Starvation Responses with Trehalose Metabolism.

    PubMed

    Garapati, Prashanth; Feil, Regina; Lunn, John Edward; Van Dijck, Patrick; Balazadeh, Salma; Mueller-Roeber, Bernd

    2015-09-01

    Plants respond to low carbon supply by massive reprogramming of the transcriptome and metabolome. We show here that the carbon starvation-induced NAC (for NO APICAL MERISTEM/ARABIDOPSIS TRANSCRIPTION ACTIVATION FACTOR/CUP-SHAPED COTYLEDON) transcription factor Arabidopsis (Arabidopsis thaliana) Transcription Activation Factor1 (ATAF1) plays an important role in this physiological process. We identified TREHALASE1, the only trehalase-encoding gene in Arabidopsis, as a direct downstream target of ATAF1. Overexpression of ATAF1 activates TREHALASE1 expression and leads to reduced trehalose-6-phosphate levels and a sugar starvation metabolome. In accordance with changes in expression of starch biosynthesis- and breakdown-related genes, starch levels are generally reduced in ATAF1 overexpressors but elevated in ataf1 knockout plants. At the global transcriptome level, genes affected by ATAF1 are broadly associated with energy and carbon starvation responses. Furthermore, transcriptional responses triggered by ATAF1 largely overlap with expression patterns observed in plants starved for carbon or energy supply. Collectively, our data highlight the existence of a positively acting feedforward loop between ATAF1 expression, which is induced by carbon starvation, and the depletion of cellular carbon/energy pools that is triggered by the transcriptional regulation of downstream gene regulatory networks by ATAF1. PMID:26149570

  20. Ethylene Inhibits Cell Proliferation of the Arabidopsis Root Meristem.

    PubMed

    Street, Ian H; Aman, Sitwat; Zubo, Yan; Ramzan, Aleena; Wang, Xiaomin; Shakeel, Samina N; Kieber, Joseph J; Schaller, G Eric

    2015-09-01

    The root system of plants plays a critical role in plant growth and survival, with root growth being dependent on both cell proliferation and cell elongation. Multiple phytohormones interact to control root growth, including ethylene, which is primarily known for its role in controlling root cell elongation. We find that ethylene also negatively regulates cell proliferation at the root meristem of Arabidopsis (Arabidopsis thaliana). Genetic analysis indicates that the inhibition of cell proliferation involves two pathways operating downstream of the ethylene receptors. The major pathway is the canonical ethylene signal transduction pathway that incorporates CONSTITUTIVE TRIPLE RESPONSE1, ETHYLENE INSENSITIVE2, and the ETHYLENE INSENSITIVE3 family of transcription factors. The secondary pathway is a phosphorelay based on genetic analysis of receptor histidine kinase activity and mutants involving the type B response regulators. Analysis of ethylene-dependent gene expression and genetic analysis supports SHORT HYPOCOTYL2, a repressor of auxin signaling, as one mediator of the ethylene response and furthermore, indicates that SHORT HYPOCOTYL2 is a point of convergence for both ethylene and cytokinin in negatively regulating cell proliferation. Additional analysis indicates that ethylene signaling contributes but is not required for cytokinin to inhibit activity of the root meristem. These results identify key elements, along with points of cross talk with cytokinin and auxin, by which ethylene negatively regulates cell proliferation at the root apical meristem. PMID:26149574

  1. Root Canal Microbiota of Teeth with Chronic Apical Periodontitis▿ †

    PubMed Central

    Rôças, I. N.; Siqueira, J. F.

    2008-01-01

    Samples from infected root canals of 43 teeth with chronic apical periodontitis were analyzed for the presence and relative levels of 83 oral bacterial species and/or phylotypes using a reverse-capture checkerboard hybridization assay. Associations between the most frequently detected taxa were also recorded. The most prevalent taxa were Olsenella uli (74%), Eikenella corrodens (63%), Porphyromonas endodontalis (56%), Peptostreptococcus anaerobius (54%), and Bacteroidetes oral clone X083 (51%). When prevalence was considered only for bacteria present at levels >105, Bacteroidetes clone X083 was the most frequently isolated bacterium (37%), followed by Parvimonas micra (28%), E. corrodens (23%), and Tannerella forsythia (19%). The number of target taxa per canal was directly proportional to the size of the apical periodontitis lesion, with lesions >10 mm in diameter harboring a mean number of approximately 20 taxa. Several positive associations for the most prevalent taxa were disclosed for the first time and may have important ecological and pathogenic implications. In addition to strengthening the association of several cultivable named species with chronic apical periodontitis, the present findings using a large-scale analysis allowed the inclusion of some newly named species and as-yet-uncultivated phylotypes in the set of candidate pathogens associated with this disease. PMID:18768651

  2. Root canal microbiota of teeth with chronic apical periodontitis.

    PubMed

    Rôças, I N; Siqueira, J F

    2008-11-01

    Samples from infected root canals of 43 teeth with chronic apical periodontitis were analyzed for the presence and relative levels of 83 oral bacterial species and/or phylotypes using a reverse-capture checkerboard hybridization assay. Associations between the most frequently detected taxa were also recorded. The most prevalent taxa were Olsenella uli (74%), Eikenella corrodens (63%), Porphyromonas endodontalis (56%), Peptostreptococcus anaerobius (54%), and Bacteroidetes oral clone X083 (51%). When prevalence was considered only for bacteria present at levels >10(5), Bacteroidetes clone X083 was the most frequently isolated bacterium (37%), followed by Parvimonas micra (28%), E. corrodens (23%), and Tannerella forsythia (19%). The number of target taxa per canal was directly proportional to the size of the apical periodontitis lesion, with lesions >10 mm in diameter harboring a mean number of approximately 20 taxa. Several positive associations for the most prevalent taxa were disclosed for the first time and may have important ecological and pathogenic implications. In addition to strengthening the association of several cultivable named species with chronic apical periodontitis, the present findings using a large-scale analysis allowed the inclusion of some newly named species and as-yet-uncultivated phylotypes in the set of candidate pathogens associated with this disease. PMID:18768651

  3. An Apical-Membrane Chloride Channel in Human Tracheal Epithelium

    NASA Astrophysics Data System (ADS)

    Welsh, Michael J.

    1986-06-01

    The mechanism of chloride transport by airway epithelia has been of substantial interest because airway and sweat gland-duct epithelia are chloride-impermeable in cystic fibrosis. The decreased chloride permeability prevents normal secretion by the airway epithelium, thereby interfering with mucociliary clearance and contributing to the morbidity and mortality of the disease. Because chloride secretion depends on and is regulated by chloride conductance in the apical cell membrane, the patch-clamp technique was used to directly examine single-channel currents in primary cultures of human tracheal epithelium. The cells contained an anion-selective channel that was not strongly voltage-gated or regulated by calcium in cell-free patches. The channel was also blocked by analogs of carboxylic acid that decrease apical chloride conductance in intact epithelia. When attached to the cell, the channel was activated by isoproterenol, although the channel was also observed to open spontaneously. However, in some cases, the channel was only observed after the patch was excised from the cell. These results suggest that this channel is responsible for the apical chloride conductance in airway epithelia.

  4. Fatty Acids Inhibit Apical Membrane Chloride Channels in Airway Epithelia

    NASA Astrophysics Data System (ADS)

    Anderson, Matthew P.; Welsh, Michael J.

    1990-09-01

    Apical membrane Cl^- channels control the rate of transepithelial Cl^- secretion in airway epithelia. cAMP-dependent protein kinase and protein kinase C regulate Cl^- channels by phosphorylation; in cystic fibrosis cells, phosphorylation-dependent activation of Cl^- channels is defective. Another important signaling system involves arachidonic acid, which is released from cell membranes during receptor-mediated stimulation. Here we report that arachidonic acid reversibly inhibited apical membrane Cl^- channels in cell-free patches of membrane. Arachidonic acid itself inhibited the channel and not a cyclooxygenase or lipoxygenase metabolite because (i) inhibitors of these enzymes did not block the response, (ii) fatty acids that are not substrates for the enzymes had the same effect as arachidonic acid, and (iii) metabolites of arachidonic acid did not inhibit the channel. Inhibition occurred only when fatty acids were added to the cytosolic surface of the membrane patch. Unsaturated fatty acids were more potent than saturated fatty acids. Arachidonic acid inhibited Cl^- channels from both normal and cystic fibrosis cells. These results suggest that fatty acids directly inhibit apical membrane Cl^- channels in airway epithelial cells.

  5. Actin Turnover-Mediated Gravity Response in Maize Root Apices

    PubMed Central

    Mancuso, Stefano; Barlow, Peter W; Volkmann, Dieter

    2006-01-01

    The dynamic actin cytoskeleton has been proposed to be linked to gravity sensing in plants but the mechanistic understanding of these processes remains unknown. We have performed detailed pharmacological analyses of the role of the dynamic actin cytoskeleton in gravibending of maize (Zea mays) root apices. Depolymerization of actin filaments with two drugs having different mode of their actions, cytochalasin D and latrunculin B, stimulated root gravibending. By contrast, drug-induced stimulation of actin polymerization and inhibition of actin turnover, using two different agents phalloidin and jasplakinolide, compromised the root gravibending. Importantly, all these actin drugs inhibited root growth to similar extents suggesting that high actin turnover is essential for the gravity-related growth responses rather than for the general growth process. Both latrunculin B and cytochalasin D treatments inhibited root growth but restored gravibending of the decapped root apices, indicating that there is a strong potential for effective actin-mediated gravity sensing outside the cap. This elusive gravity sensing outside the root cap is dependent not only on the high rate of actin turnover but also on weakening of myosin activities, as general inhibition of myosin ATPases induced stimulation of gravibending of the decapped root apices. Collectively, these data provide evidence for the actin turnover-mediated gravity sensing outside the root cap. PMID:19521476

  6. Ontogenetic contingency of tolerance mechanisms in response to apical damage

    PubMed Central

    Gruntman, Michal; Novoplansky, Ariel

    2011-01-01

    Background and Aims Plants are able to tolerate tissue loss through vigorous branching which is often triggered by release from apical dominance and activation of lateral meristems. However, damage-induced branching might not be a mere physiological outcome of released apical dominance, but an adaptive response to environmental signals, such as damage timing and intensity. Here, branching responses to both factors were examined in the annual plant Medicago truncatula. Methods Branching patterns and allocation to reproductive traits were examined in response to variable clipping intensities and timings in M. truncatula plants from two populations that vary in the onset of reproduction. Phenotypic selection analysis was used to evaluate the strength and direction of selection on branching under the damage treatments. Key Results Plants of both populations exhibited an ontogenetic shift in tolerance mechanisms: while early damage induced greater meristem activation, late damage elicited investment in late-determined traits, including mean pod and seed biomass, and supported greater germination rates. Severe damage mostly elicited simultaneous development of multiple-order lateral branches, but this response was limited to early damage. Selection analyses revealed positive directional selection on branching in plants under early- compared with late- or no-damage treatments. Conclusions The results demonstrate that damage-induced meristem activation is an adaptive response that could be modified according to the plant's developmental stage, severity of tissue loss and their interaction, stressing the importance of considering these effects when studying plastic responses to apical damage. PMID:21873259

  7. Increased STM expression is associated with drought tolerance in Arabidopsis.

    PubMed

    Lee, Hong Gil; Choi, Yee-Ram; Seo, Pil Joon

    2016-08-20

    In higher plants, shoot apical meristem (SAM) maintains cell division activity in order to give rise to aerial plant organs. Several lines of evidence have suggested that plants ensure stem cell proliferation activity in response to various external stimuli, thereby contributing to plant adaptation and fitness. Here, we report that the abscisic acid (ABA)-inducible R2R3-type MYB96 transcription factor regulates transcript accumulation of SHOOT MERISTEMLESS (STM) possibly to contribute to plant adaptation to environmental stress. STM was up-regulated in MYB96-overexpressing activation-tagging myb96-ox plants, but down-regulated in MYB96-deficient myb96-1 mutant plants, even in the presence of ABA. Notably, the MYB96 transcription factor bound directly to the STM promoter. In addition, consistent with the role of MYB96 in drought tolerance, transgenic plants overexpressing STM (35S:STM-MYC) were more tolerant to drought stress. These observations suggest that the MYB96-STM module contributes to enhancing plant tolerance to drought stress. PMID:27448723

  8. Silent S-Type Anion Channel Subunit SLAH1 Gates SLAH3 Open for Chloride Root-to-Shoot Translocation.

    PubMed

    Cubero-Font, Paloma; Maierhofer, Tobias; Jaslan, Justyna; Rosales, Miguel A; Espartero, Joaquín; Díaz-Rueda, Pablo; Müller, Heike M; Hürter, Anna-Lena; Al-Rasheid, Khaled A S; Marten, Irene; Hedrich, Rainer; Colmenero-Flores, José M; Geiger, Dietmar

    2016-08-22

    Higher plants take up nutrients via the roots and load them into xylem vessels for translocation to the shoot. After uptake, anions have to be channeled toward the root xylem vessels. Thereby, xylem parenchyma and pericycle cells control the anion composition of the root-shoot xylem sap [1-6]. The fact that salt-tolerant genotypes possess lower xylem-sap Cl(-) contents compared to salt-sensitive genotypes [7-10] indicates that membrane transport proteins at the sites of xylem loading contribute to plant salinity tolerance via selective chloride exclusion. However, the molecular mechanism of xylem loading that lies behind the balance between NO3(-) and Cl(-) loading remains largely unknown. Here we identify two root anion channels in Arabidopsis, SLAH1 and SLAH3, that control the shoot NO3(-)/Cl(-) ratio. The AtSLAH1 gene is expressed in the root xylem-pole pericycle, where it co-localizes with AtSLAH3. Under high soil salinity, AtSLAH1 expression markedly declined and the chloride content of the xylem sap in AtSLAH1 loss-of-function mutants was half of the wild-type level only. SLAH3 anion channels are not active per se but require extracellular nitrate and phosphorylation by calcium-dependent kinases (CPKs) [11-13]. When co-expressed in Xenopus oocytes, however, the electrically silent SLAH1 subunit gates SLAH3 open even in the absence of nitrate- and calcium-dependent kinases. Apparently, SLAH1/SLAH3 heteromerization facilitates SLAH3-mediated chloride efflux from pericycle cells into the root xylem vessels. Our results indicate that under salt stress, plants adjust the distribution of NO3(-) and Cl(-) between root and shoot via differential expression and assembly of SLAH1/SLAH3 anion channel subunits. PMID:27397895

  9. Bud emergence and shoot growth from mature citrus nodal segments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bud emergence and shoot growth from adult phase citrus nodal cultures were studied using Citrus mitis (calamondin), Citrus paradisi (grapefruit), and Citrus sinensis (sweet orange). The effects of 6-benzylaminopurine (BA), indole 3-acetic acid (IAA), and citrus type on shoot quality and growth fro...

  10. Adventitious shoot regeneration of pear (Pyrus communis L.) cultivars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adventitious shoot regeneration of twenty-four pear clones was compared in a common in vitro shoot induction and development protocol. This study also compared cultures newly established from scionwood with cultures that have been in long-term cold storage. In vitro cultures of 13 Pyrus clones and...

  11. Determinants of elite-level air rifle shooting performance.

    PubMed

    Ihalainen, S; Kuitunen, S; Mononen, K; Linnamo, V

    2016-03-01

    This study focused on identifying the most important factors determining performance in elite-level air rifle shooting technique. Forty international- and national-level shooters completed a simulated air rifle shooting competition series. From a total of 13 795 shots in 319 tests, shooting score and 17 aiming point trajectory variables were measured with an optoelectronic device and six postural balance variables were measured with force platform. Principal component analysis revealed six components in the air rifle shooting technique: aiming time, stability of hold, measurement time, cleanness of triggering, aiming accuracy, and timing of triggering. Multiple regression analysis identified four of those, namely stability of hold, cleanness of triggering, aiming accuracy, and timing of triggering as the most important predictors of shooting performance, accounting for 81% of the variance in shooting score. The direct effect of postural balance on performance was small, accounting for less than 1% of the variance in shooting score. Indirectly, the effect can be greater through a more stable holding ability, to which postural balance was correlated significantly (R = 0.55, P < 0.001). The results of the present study can be used in assessing athletes' technical strengths and weaknesses and in directing training programs on distinct shooting technical components. PMID:25850700

  12. Revisiting the Virginia Tech Shootings: An Ecological Systems Analysis

    ERIC Educational Resources Information Center

    Hong, Jun Sung; Cho, Hyunkag; Lee, Alvin Shiulain

    2010-01-01

    School shooting cases since the late 1990s have prompted school officials and legislators to develop and implement programs and measures that would prevent violence in school. Despite the number of explanations by the media, politicians, organizations, and researchers about the etiology of school shootings, we are not united in our understanding…

  13. Advanced Hunter Education and Shooting Sports Responsibility. Bulletin 555A.

    ERIC Educational Resources Information Center

    Benson, Delwin E.; Richardson, Rodd E.

    This manual is designed as a compendium from which instructors can select materials and instructional aids for use in hunter education and shooting sports programs. Presented in the manual are 43 lessons and 34 laboratory activities that have been organized into units on the following topics: shooting sports responsibility, the learning process…

  14. The Ectomycorrhizal Fungus Laccaria bicolor Stimulates Lateral Root Formation in Poplar and Arabidopsis through Auxin Transport and Signaling1[W