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Hyung-taeg Cho - One of the best experts on this subject based on the ideXlab platform.
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auxin the organizer of the hormonal environmental signals for Root Hair growth
Frontiers in Plant Science, 2013Co-Authors: Richard Dong Wook Lee, Hyung-taeg ChoAbstract:The Root Hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating Root Hair development. These environmental factors affect the Root Hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate Root Hair development in which auxin appears to form the most intensive networks with the pathways from environmental factors and hormones. Moreover, auxin action for Root Hair development is genetically located immediately upstream of the Root Hair-morphogenetic genes. These observations suggest that auxin plays as an organizing node for environmental/hormonal pathways to modulate Root Hair growth.
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Auxin, the organizer of the hormonal/environmental signals for Root Hair growth.
Frontiers in Plant Science, 2013Co-Authors: Richard Dong Wook Lee, Hyung-taeg ChoAbstract:The Root Hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating Root Hair development. These environmental factors affect the Root Hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate Root Hair development in which auxin appears to form the most intensive networks with the pathways from environmental factors and hormones. Moreover, auxin action for Root Hair development is genetically located immediately upstream of the Root Hair-morphogenetic genes. These observations suggest that auxin plays as an organizing node for environmental/hormonal pathways to modulate Root Hair growth.
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differential auxin transporting activities of pin formed proteins in arabidopsis Root Hair cells
Plant Physiology, 2010Co-Authors: Anindya Ganguly, Sang Ho Lee, Misuk Cho, Ok Ran Lee, Heejin Yoo, Hyung-taeg ChoAbstract:The Arabidopsis (Arabidopsis thaliana) genome includes eight PIN-FORMED (PIN) members that are molecularly diverged. To comparatively examine their differences in auxin-transporting activity and subcellular behaviors, we expressed seven PIN proteins specifically in Arabidopsis Root Hairs and analyzed their activities in terms of the degree of PIN-mediated Root Hair inhibition or enhancement and determined their subcellular localization. Expression of six PINs (PIN1–PIN4, PIN7, and PIN8) in Root Hair cells greatly inhibited Root Hair growth, most likely by lowering auxin levels in the Root Hair cell by their auxin efflux activities. The auxin efflux activity of PIN8, which had not been previously demonstrated, was further confirmed using a tobacco (Nicotiana tabacum) cell assay system. In accordance with these results, those PINs were localized in the plasma membrane, where they likely export auxin to the apoplast and formed internal compartments in response to brefeldin A. These six PINs conferred different degrees of Root Hair inhibition and sensitivities to auxin or auxin transport inhibitors. Conversely, PIN5 mostly localized to internal compartments, and its expression in Root Hair cells rather slightly stimulated Hair growth, implying that PIN5 enhanced internal auxin availability. These results suggest that different PINs behave differentially in catalyzing auxin transport depending upon their molecular activity and subcellular localization in the Root Hair cell.
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cis element and transcriptome based screening of Root Hair specific genes and their functional characterization in arabidopsis
Plant Physiology, 2009Co-Authors: Sukyung Won, Misuk Cho, Yongju Lee, Hayeon Lee, Yoonkyung Heo, Hyung-taeg ChoAbstract:Understanding the cellular differentiation of multicellular organisms requires the characterization of genes whose expression is modulated in a cell type-specific manner. The Arabidopsis (Arabidopsis thaliana) Root Hair cell is one model for studying cellular differentiation. In this study, Root Hair cell-specific genes were screened by a series of in silico and experimental filtration procedures. This process included genome-wide screening for genes with a Root Hair-specific cis-element in their promoters, filtering Root-specific genes from the Root Hair-specific cis-element-containing genes, further filtering of genes that were suppressed in Root Hair-defective plant lines, and experimental confirmation by promoter assay. These procedures revealed 19 Root Hair-specific genes, including many protein kinases and cell wall-related genes, most of which have not been characterized thus far. Functional analyses of these Root Hair-specific genes with loss-of-function mutants and overexpressing transformants revealed that they play roles in Hair growth and morphogenesis. This study demonstrates that a defined cis-element can serve as a filter to screen certain cell type-specific genes and implicates many new Root Hair-specific genes in Root Hair development.
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Auxin and Root Hair Morphogenesis
Plant Cell Monographs, 2009Co-Authors: S. H. Lee, Hyung-taeg ChoAbstract:Auxin is a potent hormonal effector of Root Hair development. A plethora of genetic and pharmacological studies have revealed that aberrations in auxin availability or signaling can cause defects in Root Hair growth and morphology. Recently identified components of auxin signaling and auxin transport have been implicated in Root Hair morphogenesis. The alteration of Root Hair morphogenesis by auxin also enables this single cell system to serve as an in planta biological marker through which the action mechanism of auxin can be examined.
Liam Dolan - One of the best experts on this subject based on the ideXlab platform.
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PtdIns(3,5)P2 mediates Root Hair shank hardening in Arabidopsis
Nature plants, 2018Co-Authors: Tomoko Hirano, Liam Dolan, Takashi Aoyama, Seiji Takeda, Hiroki Konno, Mariko Kato, Takumi Higaki, Hisako Takigawa-imamura, Masa H. SatoAbstract:Root Hairs elongate by tip growth and simultaneously harden the shank by constructing the inner secondary cell wall layer. While much is known about the process of tip growth1, almost nothing is known about the mechanism by which Root Hairs harden the shank. Here we show that phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2), the enzymatic product of FORMATION OF APLOID AND BINUCLEATE CELLS 1 (FAB1), is involved in the hardening of the shank in Root Hairs in Arabidopsis. FAB1 and PtdIns(3,5)P2 localize to the plasma membrane along the shank of growing Root Hairs. By contrast, phosphatidylinositol 4-phosphate 5-kinase 3 (PIP5K3) and PtdIns(4,5)P2 localize to the apex of the Root Hair where they are required for tip growth. Reduction of FAB1 function results in the formation of wavy Root Hairs while those of the wild type are straight. The localization of FAB1 in the plasma membrane of the Root Hair shank requires the activity of Rho-related GTPases from plants 10 (ROP10) and localization of ROP10 requires FAB1 activity. Computational modelling of Root Hair morphogenesis successfully reproduces the wavy Root Hair phenotype. Taken together, these data demonstrate that Root Hair shank hardening requires PtdIns(3,5)P2/ROP10 signalling. Root Hairs are frequently used to study tip growth in plants. Most of the research was focused on the polarized tip region. Now, a mechanism involving PtdIns(4,5)P2 and a plant-specific Rho-GTPase is proposed to be required for hardening the shank of growing Root Hairs.
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Root Hair development in grasses and cereals (Poaceae).
Current Opinion in Genetics & Development, 2017Co-Authors: Liam DolanAbstract:Root Hairs are tubular, cellular outgrowths of epidermal cells that extend from the Root surface into the soil. Root Hairs tether Root systems to their growth substrate, take up inorganic nutrients and water, and interact with the soil microflora. At maturity, the Root epidermis comprises two cell types; cells with Root Hairs and Hairless epidermal cells. These two cell types alternate with each other along longitudinal files in grasses and cereals (Poaceae). While the mechanism by which this alternating pattern develops is unknown, the later stages of Root Hair differentiation are controlled by a conserved mechanism that promotes Root Hair development among angiosperms.
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Root Hair defective six like4 rsl4 promotes Root Hair elongation by transcriptionally regulating the expression of genes required for cell growth
New Phytologist, 2016Co-Authors: Priya Vijayakumar, Sourav Datta, Liam DolanAbstract:Root Hair DEFECTIVE SIX-LIKE4 (RSL4) is necessary and sufficient for Root Hair elongation in Arabidopsis thaliana. Root Hair length is determined by the duration for which RSL4 protein is present in the developing Root Hair. The aim of this research was to identify genes regulated by RSL4 that affect Root Hair growth. To identify genes regulated by RSL4, we identified genes whose expression was elevated by induction of RSL4 activity in the presence of an inhibitor of translation. Thirty-four genes were identified as putative targets of RSL transcriptional regulation, and the results suggest that the activities of SUPPRESSOR OF ACTIN (SAC1), EXOCSYT SUBUNIT 70A1 (EXO70A1), PEROXIDASE7 (PRX7) and CALCIUM-DEPENDENT PROTEIN KINASE11 (CPK11) are required for Root Hair elongation. These data indicate that RSL4 controls cell growth by controlling the expression of genes encoding proteins involved in cell signalling, cell wall modification and secretion.
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Root Hair DEFECTIVE SIX-LIKE Class I Genes Promote Root Hair Development in the Grass Brachypodium distachyon.
PLOS Genetics, 2016Co-Authors: Liam DolanAbstract:Genes encoding Root Hair DEFECTIVE SIX-LIKE (RSL) class I basic helix loop helix proteins are expressed in future Root Hair cells of the Arabidopsis thaliana Root meristem where they positively regulate Root Hair cell development. Here we show that there are three RSL class I protein coding genes in the Brachypodium distachyon genome, BdRSL1, BdRSL2 and BdRSL3, and each is expressed in developing Root Hair cells after the asymmetric cell division that forms Root Hair cells and Hairless epidermal cells. Expression of BdRSL class I genes is sufficient for Root Hair cell development: ectopic overexpression of any of the three RSL class I genes induces the development of Root Hairs in every cell of the Root epidermis. Expression of BdRSL class I genes in Root Hairless Arabidopsis thaliana Root Hair defective 6 (Atrhd6) Atrsl1 double mutants, devoid of RSL class I function, restores Root Hair development indicating that the function of these proteins has been conserved. However, neither AtRSL nor BdRSL class I genes is sufficient for Root Hair development in A. thaliana. These data demonstrate that the spatial pattern of class I RSL activity can account for the pattern of Root Hair cell differentiation in B. distachyon. However, the spatial pattern of class I RSL activity cannot account for the spatial pattern of Root Hair cells in A. thaliana. Taken together these data indicate that that the functions of RSL class I proteins have been conserved among most angiosperms—monocots and eudicots—despite the dramatically different patterns of Root Hair cell development.
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Root Hair DEFECTIVE SIX‐LIKE4 (RSL4) promotes Root Hair elongation by transcriptionally regulating the expression of genes required for cell growth
New Phytologist, 2016Co-Authors: Priya Vijayakumar, Sourav Datta, Liam DolanAbstract:Summary Root Hair DEFECTIVE SIX-LIKE4 (RSL4) is necessary and sufficient for Root Hair elongation in Arabidopsis thaliana. Root Hair length is determined by the duration for which RSL4 protein is present in the developing Root Hair. The aim of this research was to identify genes regulated by RSL4 that affect Root Hair growth. To identify genes regulated by RSL4, we identified genes whose expression was elevated by induction of RSL4 activity in the presence of an inhibitor of translation. Thirty-four genes were identified as putative targets of RSL transcriptional regulation, and the results suggest that the activities of SUPPRESSOR OF ACTIN (SAC1), EXOCSYT SUBUNIT 70A1 (EXO70A1), PEROXIDASE7 (PRX7) and CALCIUM-DEPENDENT PROTEIN KINASE11 (CPK11) are required for Root Hair elongation. These data indicate that RSL4 controls cell growth by controlling the expression of genes encoding proteins involved in cell signalling, cell wall modification and secretion.
J. Schiefelbein - One of the best experts on this subject based on the ideXlab platform.
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novel ttg1 mutants modify Root Hair pattern formation in arabidopsis
Frontiers in Plant Science, 2020Co-Authors: Yun Long, J. SchiefelbeinAbstract:The patterning of Root-Hair and non-Hair epidermal cells in the Arabidopsis Root is governed by a network of transcriptional regulators. The central MYB-bHLH-WD40 (MBW) transcriptional complex includes the WD40-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1). To clarify the role of TTG1, we describe the identification and analysis of two new ttg1 mutants. Each of these mutants contains a single nucleotide change in the TTG1 gene, which causes a single amino-acid substitution in the predicted TTG1 protein and alters Root-Hair pattern formation. Surprisingly, these new ttg1 mutants exhibit decreased Root-Hair formation, particularly in the caprice (cpc) mutant background, rather than increased Root-Hair formation as reported for strong ttg1 mutants. We show that the unique phenotype of these mutants is due to differential effects of the altered TTG1 proteins on target gene expression, associated with a weakened ability to interact with its GLABRA3 bHLH partner. These findings demonstrate the crucial role of TTG1 for the appropriate balance of target gene activation to achieve the proper pattern of epidermal cell types during Arabidopsis Root development.
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Diversification of Root Hair Development Genes in Vascular Plants
Plant Physiology, 2017Co-Authors: Ling Huang, Wenjia Wang, J. SchiefelbeinAbstract:The molecular genetic program for Root Hair development has been studied intensively in Arabidopsis (Arabidopsis thaliana). To understand the extent to which this program might operate in other plants, we conducted a large-scale comparative analysis of Root Hair development genes from diverse vascular plants, including eudicots, monocots, and a lycophyte. Combining phylogenetics and transcriptomics, we discovered conservation of a core set of Root Hair genes across all vascular plants, which may derive from an ancient program for unidirectional cell growth coopted for Root Hair development during vascular plant evolution. Interestingly, we also discovered preferential diversification in the structure and expression of Root Hair development genes, relative to other Root Hair- and Root-expressed genes, among these species. These differences enabled the definition of sets of genes and gene functions that were acquired or lost in specific lineages during vascular plant evolution. In particular, we found substantial divergence in the structure and expression of genes used for Root Hair patterning, suggesting that the Arabidopsis transcriptional regulatory mechanism is not shared by other species. To our knowledge, this study provides the first comprehensive view of gene expression in a single plant cell type across multiple species.
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multiple phytohormones promote Root Hair elongation by regulating a similar set of genes in the Root epidermis in arabidopsis
Journal of Experimental Botany, 2016Co-Authors: Shan Zhang, J. Schiefelbein, Linli Huang, An Yan, Yihua Liu, Bohan Liu, Aidong Zhang, Yinbo GanAbstract:Multiple phytohormones, including auxin, ethylene, and cytokinin, play vital roles in regulating cell development in the Root epidermis. However, their interactions in specific Root Hair cell developmental stages are largely unexplored. To bridge this gap, we employed genetic and pharmacological approaches as well as transcriptional analysis in order to dissect their distinct and overlapping roles in Root Hair initiation and elongation in Arabidopsis thaliana Our results show that among auxin, ethylene, and cytokinin, only ethylene induces ectopic Root Hair cells in wild-type plants, implying a special role of ethylene in the Hair initiation stage. In the subsequent elongation stage, however, auxin, ethylene, and cytokinin enhance Root Hair tip growth equally. Our data also suggest that the effect of cytokinin is independent from auxin and ethylene in this process. Exogenous cytokinin restores Root Hair elongation when the auxin and ethylene signal is defective, whereas auxin and ethylene also sustain elongation in the absence of the cytokinin signal. Notably, transcriptional analyses demonstrated that auxin, ethylene, and cytokinin regulate a similar set of Root Hair-specific genes. Together these analyses provide important clues regarding the mechanism of hormonal interactions and regulation in the formation of single-cell structures.
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Root Hair-specific disruption of cellulose and xyloglucan in AtCSLD3 mutants, and factors affecting the post-rupture resumption of mutant Root Hair growth
Planta, 2011Co-Authors: Moira E. Galway, J. Schiefelbein, Geoffrey O. WasteneysAbstract:The glycosyl transferase encoded by the cellulose synthase-like gene CSLD3/KJK/RHD7 (At3g03050) is required for cell wall integrity during Root Hair formation in Arabidopsis thaliana but it remains unclear whether it contributes to the synthesis of cellulose or hemicellulose. We identified two new alleles, Root Hair-defective (rhd) 7-1 and rhd7-4, which affect the C-terminal end of the encoded protein. Like Root Hairs in the previously characterized kjk-2 putative null mutant, rhd7-1 and rhd7-4 Hairs rupture before tip growth but, depending on the growth medium and temperature, Hairs are able to survive rupture and initiate tip growth, indicating that these alleles retain some function. At 21°C, the rhd7 tip-growing Root Hairs continued to rupture but at 5oC, rupture was inhibited, resulting in long, wild type-like Root Hairs. At both temperatures, the expression of another Root Hair-specific CSLD gene, CSLD2, was increased in the rhd7-4 mutant but reduced in the kjk-2 mutant, suggesting that CSLD2 expression is CSLD3-dependent, and that CSLD2 could partially compensate for CSLD3 defects to prevent rupture at 5°C. Using a fluorescent brightener (FB 28) to detect cell wall (1 → 4)-β-glucans (primarily cellulose) and CCRC-M1 antibody to detect fucosylated xyloglucans revealed a patchy distribution of both in the mutant Root Hair cell walls. Cell wall thickness varied, and immunogold electron microscopy indicated that xyloglucan distribution was altered throughout the Root Hair cell walls. These cell wall defects indicate that CSLD3 is required for the normal organization of both cellulose and xyloglucan in Root Hair cell walls.
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Genetics of Root Hair Formation
Plant Cell Monographs, 2009Co-Authors: C. Grierson, J. SchiefelbeinAbstract:There has been a great deal of recent progress in our understanding of the genetic control of Root Hair development, particularly in Arabidopsis thaliana. This chapter summarizes the genes and gene products that have been identified using forward and reverse genetic approaches. The involvement of these genes at various stages of Root Hair development is described, including the specification of the Root Hair cell type, the initiation of the Root Hair outgrowth, and the elongation (tip growth) of the Root Hair.
Takashi Aoyama - One of the best experts on this subject based on the ideXlab platform.
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PtdIns(3,5)P2 mediates Root Hair shank hardening in Arabidopsis
Nature plants, 2018Co-Authors: Tomoko Hirano, Liam Dolan, Takashi Aoyama, Seiji Takeda, Hiroki Konno, Mariko Kato, Takumi Higaki, Hisako Takigawa-imamura, Masa H. SatoAbstract:Root Hairs elongate by tip growth and simultaneously harden the shank by constructing the inner secondary cell wall layer. While much is known about the process of tip growth1, almost nothing is known about the mechanism by which Root Hairs harden the shank. Here we show that phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2), the enzymatic product of FORMATION OF APLOID AND BINUCLEATE CELLS 1 (FAB1), is involved in the hardening of the shank in Root Hairs in Arabidopsis. FAB1 and PtdIns(3,5)P2 localize to the plasma membrane along the shank of growing Root Hairs. By contrast, phosphatidylinositol 4-phosphate 5-kinase 3 (PIP5K3) and PtdIns(4,5)P2 localize to the apex of the Root Hair where they are required for tip growth. Reduction of FAB1 function results in the formation of wavy Root Hairs while those of the wild type are straight. The localization of FAB1 in the plasma membrane of the Root Hair shank requires the activity of Rho-related GTPases from plants 10 (ROP10) and localization of ROP10 requires FAB1 activity. Computational modelling of Root Hair morphogenesis successfully reproduces the wavy Root Hair phenotype. Taken together, these data demonstrate that Root Hair shank hardening requires PtdIns(3,5)P2/ROP10 signalling. Root Hairs are frequently used to study tip growth in plants. Most of the research was focused on the polarized tip region. Now, a mechanism involving PtdIns(4,5)P2 and a plant-specific Rho-GTPase is proposed to be required for hardening the shank of growing Root Hairs.
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glabra2 directly suppresses basic helix loop helix transcription factor genes with diverse functions in Root Hair development
The Plant Cell, 2015Co-Authors: Qing Lin, Yohei Ohashi, Mariko Kato, Tomohiko Tsuge, Takashi AoyamaAbstract:The Arabidopsis thaliana GLABRA2 (GL2) gene encodes a transcription factor involved in the cell differentiation of various epidermal tissues. During Root Hair pattern formation, GL2 suppresses Root Hair development in non-Hair cells, acting as a node between the gene regulatory networks for cell fate determination and cell differentiation. Despite the importance of GL2 function, its molecular basis remains obscure because the GL2 target genes leading to the network for cell differentiation are unknown. We identified five basic helix-loop-helix (bHLH) transcription factor genes (Root Hair DEFECTIVE6 [RHD6], RHD6-LIKE1 [RSL1], RSL2, Lj-RHL1-LIKE1 [LRL1], and LRL2) as GL2 direct targets using transcriptional and posttranslational induction systems. Chromatin immunoprecipitation analysis confirmed GL2 binding to upstream regions of these genes in planta. Reporter gene analyses showed that these genes are expressed in various stages of Root Hair development and are suppressed by GL2 in non-Hair cells. GL2 promoter-driven GFP fusions of LRL1 and LRL2, but not those of the other bHLH proteins, conferred Root Hair development on non-Hair cells. These results indicate that GL2 directly suppresses bHLH genes with diverse functions in Root Hair development.
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the arabidopsis phosphatidylinositol phosphate 5 kinase pip5k3 is a key regulator of Root Hair tip growth
The Plant Cell, 2008Co-Authors: Hiroaki Kusano, Atsuhiro Oka, Joop E.m. Vermeer, Tomohiko Tsuge, Christa Testerink, Hiroaki Shimada, Teun Munnik, Takashi AoyamaAbstract:Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] functions as a site-specific signal on membranes to promote cytoskeletal reorganization and membrane trafficking. Localization of PtdIns(4,5)P2 to apices of growing Root Hairs and pollen tubes suggests that it plays an important role in tip growth. However, its regulation and mode of action remain unclear. We found that Arabidopsis thaliana PIP5K3 (for Phosphatidylinositol Phosphate 5-Kinase 3) encodes a phosphatidylinositol 4-phosphate 5-kinase, a key enzyme producing PtdIns(4,5)P2, that is preferentially expressed in growing Root Hairs. T-DNA insertion mutations that substantially reduced the expression of PIP5K3 caused significantly shorter Root Hairs than in the wild type. By contrast, overexpression caused longer Root Hairs and multiple protruding sites on a single trichoblast. A yellow fluorescent protein (YFP) fusion of PIP5K3, driven by the PIP5K3 promoter, complemented the short-Root-Hair phenotype. PIP5K3-YFP localized to the plasma membrane and cytoplasmic space of elongating Root Hair apices, to growing Root Hair bulges, and, notably, to sites about to form Root Hair bulges. The signal was greatest in rapidly growing Root Hairs and quickly disappeared when elongation ceased. These results provide evidence that PIP5K3 is involved in localizing PtdIns(4,5)P2 to the elongating Root Hair apex and is a key regulator of the machinery that initiates and promotes Root Hair tip growth.
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Modulation of Phospholipid Signaling by GLABRA2 in Root-Hair Pattern Formation
Science, 2003Co-Authors: Yohei Ohashi, Renato A. Rodrigues-pousada, Marco Possenti, Ida Ruberti, Giorgio Morelli, Takashi AoyamaAbstract:The Root-Hair pattern of Arabidopsis is determined through a regulatory circuit composed of transcription factor genes. The homeobox gene GLABRA2 (GL2) has been considered a key component, acting farthest downstream in this regulation. GL2 modified to include a transactivating function caused epidermal cells to develop ectopic Root Hairs or Root Hair–like structures. With this system, the phospholipase Dζ1 gene (AtPLDζ1) was identified as a direct target of GL2. Inducible expression of AtPLDζ1 promoted ectopic Root-Hair initiation. We conclude that GL2 exerts its regulatory effect on Root-Hair development through modulation of phospholipid signaling.
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modulation of phospholipid signaling by glabra2 in Root Hair pattern formation
Science, 2003Co-Authors: Yohei Ohashi, Marco Possenti, Ida Ruberti, Giorgio Morelli, Atsuhiro Oka, Renato A Rodriguespousada, Takashi AoyamaAbstract:The Root-Hair pattern of Arabidopsis is determined through a regulatory circuit composed of transcription factor genes. The homeobox gene GLABRA2 (GL2) has been considered a key component, acting farthest downstream in this regulation. GL2 modified to include a transactivating function caused epidermal cells to develop ectopic Root Hairs or Root Hair-like structures. With this system, the phospholipase Dzeta1 gene (AtPLDzeta1) was identified as a direct target of GL2. Inducible expression of AtPLDzeta1 promoted ectopic Root-Hair initiation. We conclude that GL2 exerts its regulatory effect on Root-Hair development through modulation of phospholipid signaling.
C. Grierson - One of the best experts on this subject based on the ideXlab platform.
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Genetics of Root Hair Formation
Plant Cell Monographs, 2009Co-Authors: C. Grierson, J. SchiefelbeinAbstract:There has been a great deal of recent progress in our understanding of the genetic control of Root Hair development, particularly in Arabidopsis thaliana. This chapter summarizes the genes and gene products that have been identified using forward and reverse genetic approaches. The involvement of these genes at various stages of Root Hair development is described, including the specification of the Root Hair cell type, the initiation of the Root Hair outgrowth, and the elongation (tip growth) of the Root Hair.
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auxin transport through non Hair cells sustains Root Hair development
Nature Cell Biology, 2009Co-Authors: Angharad R Jones, Kirsten Knox, Eric M Kramer, Ranjan Swarup, Malcolm J Bennett, Colin M Lazarus, H Ottoline M Leyser, C. GriersonAbstract:As the Root develops, auxin transport through non-Hair cells sustains Root-Hair outgrowth. Mathematical modelling and experimental data reveal that auxin is transported through canals across the non-Hair cells. The plant hormone auxin controls Root epidermal cell development in a concentration-dependent manner1,2,3. Root Hairs are produced on a subset of epidermal cells as they increase in distance from the Root tip. Auxin is required for their initiation4,5,6,7 and continued growth8,9,10,11, but little is known about its distribution in this region of the Root. Contrary to the expectation that Hair cells might require active auxin influx to ensure auxin supply, we did not detect the auxin-influx transporter AUX1 in Root-Hair cells. A high level of AUX1 expression was detected in adjacent non-Hair cell files. Non-Hair cells were necessary to achieve wild-type Root-Hair length, although an auxin response was not required in these cells. Three-dimensional modelling of auxin flow in the Root tip suggests that AUX1-dependent transport through non-Hair cells maintains an auxin supply to developing Hair cells as they increase in distance from the Root tip, and sustains Root-Hair outgrowth. Experimental data support the hypothesis that instead of moving uniformly though the epidermal cell layer3,12, auxin is mainly transported through canals that extend longitudinally into the tissue.
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auxin transport through non Hair cells sustains Root Hair development
Nature Cell Biology, 2009Co-Authors: Angharad R Jones, Kirsten Knox, Eric M Kramer, Ranjan Swarup, Malcolm J Bennett, Colin M Lazarus, H Ottoline M Leyser, C. GriersonAbstract:The plant hormone auxin controls Root epidermal cell development in a concentration-dependent manner. Root Hairs are produced on a subset of epidermal cells as they increase in distance from the Root tip. Auxin is required for their initiation and continued growth, but little is known about its distribution in this region of the Root. Contrary to the expectation that Hair cells might require active auxin influx to ensure auxin supply, we did not detect the auxin-influx transporter AUX1 in Root-Hair cells. A high level of AUX1 expression was detected in adjacent non-Hair cell files. Non-Hair cells were necessary to achieve wild-type Root-Hair length, although an auxin response was not required in these cells. Three-dimensional modelling of auxin flow in the Root tip suggests that AUX1-dependent transport through non-Hair cells maintains an auxin supply to developing Hair cells as they increase in distance from the Root tip, and sustains Root-Hair outgrowth. Experimental data support the hypothesis that instead of moving uniformly though the epidermal cell layer, auxin is mainly transported through canals that extend longitudinally into the tissue.
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axr3 and shy2 interact to regulate Root Hair development
Development, 2003Co-Authors: Kirsten Knox, C. Grierson, Ottoline LeyserAbstract:Signal transduction of the plant hormone auxin centres on the regulation of the abundance of members of the Aux/IAA family of transcriptional regulators, of which there are 29 in Arabidopsis. Auxin can influence Aux/IAA abundance by promoting the transcription of Aux/IAA genes and by reducing the half-life of Aux/IAA proteins. Stabilising mutations, which render Aux/IAA proteins resistant to auxin-mediated degradation, confer a wide range of phenotypes consistent with disruptions in auxin response. Interestingly, similar mutations in different family members can confer opposite phenotypic effects. To understand the molecular basis for this functional specificity in the Aux/IAA family, we have studied a pair of Aux/IAAs, which have contrasting roles in Root Hair development. We have found that stabilising mutations in AXR3/IAA17 blocks Root Hair initiation and elongation, whereas similar mutations in SHY2/IAA3 result in early initiation of Root Hair development and prolonged Hair elongation, giving longer Root Hairs. The phenotypes resulting from double mutant combinations, the transient induction of expression of the proteins, and the pattern of transcription of the cognate genes suggest that Root Hair initiation is controlled by the relative abundance of SHY2 and AXR3 in a cell. These results suggest a general model for auxin signalling in which the modulation of the relative abundance of different Aux/IAA proteins can determine which down-stream responses are induced.
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the arabidopsis rop2 gtpase is a positive regulator of both Root Hair initiation and tip growth
The Plant Cell, 2002Co-Authors: Mark A. Jones, Junjiang Shen, Zhenbiao Yang, C. GriersonAbstract:Root Hairs provide a model system for the study of cell polarity. We examined the possibility that one or more members of the distinct plant subfamily of RHO monomeric GTPases, termed Rop, may function as molecular switches regulating Root Hair growth. Specific Rops are known to control polar growth in pollen tubes. Overexpressing Rop2 (Rop2 OX) resulted in a strong Root Hair phenotype, whereas overexpressing Rop7 appeared to inhibit Root Hair tip growth. Overexpressing Rops from other phylogenetic subgroups of Rop did not give a Root Hair phenotype. We confirmed that Rop2 was expressed throughout Hair development. Rop2 OX and constitutively active GTP-bound rop2 (CA-rop2) led to additional and misplaced Hairs on the cell surface as well as longer Hairs. Furthermore, CA-rop2 depolarized Root Hair tip growth, whereas Rop2 OX resulted in Hairs with multiple tips. Dominant negative GDP-bound Rop2 reduced the number of Hair-forming sites and led to shorter and wavy Hairs. Green fluorescent protein-Rop2 localized to the future site of Hair formation well before swelling formation and to the tip throughout Hair development. We conclude that the Arabidopsis Rop2 GTPase acts as a positive regulatory switch in the earliest visible stage in Hair development, swelling formation, and in tip growth.
