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Rudiger Simon - One of the best experts on this subject based on the ideXlab platform.

  • an acyl coa n acyltransferase regulates meristem phase change and plant architecture in barley
    Plant Physiology, 2020
    Co-Authors: Rudiger Simon, Agatha Walla, Wilma G Van Esse, Gwendolyn K Kirschner, Ganggang Guo, Annika Brunje, Iris Finkemeier, Maria Von Korff
    Abstract:

    The modification of Shoot architecture and increased investment into reproductive structures is key for crop improvement and is achieved through coordinated changes in the development and determinacy of different Shoot Meristems. A fundamental question is how the development of different Shoot Meristems is genetically coordinated to optimize the balance between vegetative and reproductive organs. Here we identify the MANY NODED DWARF1 (HvMND1) gene as a major regulator of plant architecture in barley (Hordeum vulgare). The mnd1.a mutant displayed an extended vegetative program with increased phytomer, leaf, and tiller production but a reduction in the number and size of grains. The induction of vegetative structures continued even after the transition to reproductive growth, resulting in a marked increase in longevity. Using mapping by RNA sequencing, we found that the HvMND1 gene encodes an acyl-CoA N-acyltransferase that is predominately expressed in developing axillary Meristems and young inflorescences. Exploration of the expression network modulated by HvMND1 revealed differential expression of the developmental microRNAs miR156 and miR172 and several key cell cycle and developmental genes. Our data suggest that HvMND1 plays a significant role in the coordinated regulation of reproductive phase transitions, thereby promoting reproductive growth and whole plant senescence in barley.

  • Interdomain signaling in stem cell maintenance of plant Shoot Meristems
    Molecules and Cells, 2009
    Co-Authors: Andrea Bleckmann, Rudiger Simon
    Abstract:

    The plant Shoot meristem maintains a group of stem cells that remain active throughout the plant life. They continuously generate new cells that are then recruited for organ initiation in the peripheral zone. Stem cell proliferation and daughter cell differentiation has to be integrated with overall growth and development of the diverse functional domains within the Shoot apex. Several studies have revealed extensive communication between these domains. The signaling mechanisms employed comprise diffusible peptides, directional transport of plant hormones, but also complex interactions between transcription factors, that together establish a panoply of regulatory inputs that fine-tune stem cell behavior in the Shoot meristem.

  • function of plant Shoot Meristems
    Seminars in Cell & Developmental Biology, 2001
    Co-Authors: Rudiger Simon
    Abstract:

    Growth and development of higher plants is directed by the continuous activity of Meristems, sites of sustained cell division. Organs are formed at the flanks of the Shoot meristem, while the central region contains pluripotent stem cells. The developmental programme of the meristem is coordinated by interactions between cells in separate regions of Meristems, and some of the genes involved have been studied. Transcription factors can be exchanged between meristem cell layers. The control of stem cell fate involves a ligand/receptor interaction that regulates the activity of a transcription factor, and genes expressed in organ primordia can feedback to restrict the activity of meristematic genes.

  • functional domains in plant Shoot Meristems
    BioEssays, 2001
    Co-Authors: Ulrike Brand, Martin Hobe, Rudiger Simon
    Abstract:

    Summary The development of higher plants depends on the activity of a Shoot apical meristem. Organs are formed on the flanks of the meristem, while pluripotent stem cells are found in a separate domain in the meristem centre. Further domains are distinguished by the expression patterns of genes that control the development of the Shoot meristem. Although most plant cells are immobile, their relative position within a meristem, and therefore also their function, can change after cell divisions. To maintain an active Shoot meristem throughout plant life, the cells in the meristem need constantly to assess their position, transmit this information to others, and readjust their gene expression profiles and their fate. Some of the genes that permit intercellular communication have been isolated. They enable the flow of information in and between meristem regions via ligands and receptor proteins to transcription factors, that ultimately control the fate of cells in the centre of the meristem. BioEssays 23:134‐141, 2001. fl 2001 John Wiley & Sons, Inc.

  • signaling of cell fate decisions by clavata3 in arabidopsis Shoot Meristems
    Science, 1999
    Co-Authors: Jennifer C Fletcher, Rudiger Simon, Ulrike Brand, Mark Running, Elliot M Meyerowitz
    Abstract:

    In higher plants, organogenesis occurs continuously from self-renewing apical Meristems. Arabidopsis thaliana plants with loss-of-function mutations in the CLAVATA (CLV1,2, and 3) genes have enlarged Meristems and generate extra floral organs. Genetic analysis indicates that CLV1, which encodes a receptor kinase, acts with CLV3 to control the balance between meristem cell proliferation and differentiation.CLV3 encodes a small, predicted extracellular protein.CLV3 acts nonautonomously in Meristems and is expressed at the meristem surface overlying the CLV1 domain. These proteins may act as a ligand-receptor pair in a signal transduction pathway, coordinating growth between adjacent meristematic regions.

Thomas Laux - One of the best experts on this subject based on the ideXlab platform.

  • expression dynamics of wox genes mark cell fate decisions during early embryonic patterning in arabidopsis thaliana
    Development, 2004
    Co-Authors: Achim Haecker, Ananda K Sarkar, Rita Groshardt, Bernd Geiges, Holger Breuninger, Marita Herrmann, Thomas Laux
    Abstract:

    During embryonic pattern formation, the main body axes are established and cells of different developmental fates are specified from a single-cell zygote. Despite the fundamental importance of this process, in plants, the underlying mechanisms are largely unknown. We show that expression dynamics of novel WOX (WUSCHEL related homeobox) gene family members reveal early embryonic patterning events in Arabidopsis . WOX2 and WOX8 are co-expressed in the egg cell and zygote and become confined to the apical and basal daughter cells of the zygote, respectively, by its asymmetric division. WOX2 not only marks apical descendants of the zygote, but is also functionally required for their correct development, suggesting that the asymmetric division of the plant zygote separates determinants of apical and basal cell fates. WOX9 expression is initiated in the basal daughter cell of the zygote and subsequently shifts into the descendants of the apical daughter apparently in response to signaling from the embryo proper. Expression of WOX5 shows that identity of the quiescent center is initiated very early in the hypophyseal cell, and highlights molecular and developmental similarities between the stem cell niches of root and Shoot Meristems. Together, our data suggest that during plant embryogenesis region-specific transcription programs are initiated very early in single precursor cells and that WOX genes play an important role in this process.

  • the stem cell population of arabidopsis Shoot Meristems is maintained by a regulatory loop between the clavata and wuschel genes
    Cell, 2000
    Co-Authors: Heiko Schoof, Michael Lenhard, Achim Haecker, Klaus F X Mayer, Gerd Jurgens, Thomas Laux
    Abstract:

    The higher-plant Shoot meristem is a dynamic structure whose maintenance depends on the coordination of two antagonistic processes, organ initiation and self-renewal of the stem cell population. In Arabidopsis Shoot and floral Meristems, the WUSCHEL (WUS) gene is required for stem cell identity, whereas the CLAVATA1, 2, and 3 (CLV) genes promote organ initiation. Our analysis of the interactions between these key regulators indicates that (1) the CLV genes repress WUS at the transcript level and that (2) WUS expression is sufficient to induce meristem cell identity and the expression of the stem cell marker CLV3. Our data suggest that the Shoot meristem has properties of a self-regulatory system in which WUS/CLV interactions establish a feedback loop between the stem cells and the underlying organizing center.

  • the stem cell population of arabidopsis Shoot Meristems is maintained by a regulatory loop between the clavata and wuschel genes
    Cell, 2000
    Co-Authors: Heiko Schoof, Michael Lenhard, Achim Haecker, Klaus F X Mayer, Gerd Jurgens, Thomas Laux
    Abstract:

    Summary that cells respond to signals from their neighbors. This suggests that maintaining the Shoot meristem organizaThe higher-plant Shoot meristem is a dynamic struc- tion requires regulation at two levels. First, distinct subture whose maintenance depends on the coordination populations must be delimited and second, different of two antagonistic processes, organ initiation and developmental programs must be specified within these self-renewal of the stem cell population. In Arabidopsis subpopulations. Recently, several key genes involved Shoot and floral Meristems, the WUSCHEL (WUS) in this regulation have been identified. gene is required for stem cell identity, whereas the The homeobox gene WUSCHEL is required for speciCLAVATA1, 2, and 3 (CLV) genes promote organ initia- fying stem cell identity. Mutations in WUS result in the tion. Our analysis of the interactions between these misspecification of stem cells and premature terminakey regulators indicates that (1) the CLV genes repress tion of Shoot and floral Meristems after a few organs WUS at the transcript level and that (2) WUS expres- have been formed (Laux et al., 1996). WUS expression sion is sufficient to induce meristem cell identity and is initiated at the 16-cell embryo stage, long before a the expression of the stem cell marker CLV3. Our data Shoot meristem is evident, and gradually becomes resuggest that the Shoot meristem has properties of a stricted to the center of the developing Shoot meristem self-regulatory system in which WUS/CLV interactions primordium by several asymmetric cell divisions (Mayer establish a feedback loop between the stem cells and et al., 1998). In the active Shoot meristem, WUS is ex

Ottoline Leyser - One of the best experts on this subject based on the ideXlab platform.

  • strigolactone can promote or inhibit Shoot branching by triggering rapid depletion of the auxin efflux protein pin1 from the plasma membrane
    PLOS Biology, 2013
    Co-Authors: Naoki Shinohara, Ottoline Leyser, Catherine Taylor
    Abstract:

    Plants continuously extend their root and Shoot systems through the action of Meristems at their growing tips. By regulating which Meristems are active, plants adjust their body plans to suit local environmental conditions. The transport network of the phytohormone auxin has been proposed to mediate this systemic growth coordination, due to its self-organising, environmentally sensitive properties. In particular, a positive feedback mechanism termed auxin transport canalization, which establishes auxin flow from active Shoot Meristems (auxin sources) to the roots (auxin sinks), has been proposed to mediate competition between Shoot Meristems and to balance Shoot and root growth. Here we provide strong support for this hypothesis by demonstrating that a second hormone, strigolactone, regulates growth redistribution in the Shoot by rapidly modulating auxin transport. A computational model in which strigolactone action is represented as an increase in the rate of removal of the auxin export protein, PIN1, from the plasma membrane can reproduce both the auxin transport and Shoot branching phenotypes observed in various mutant combinations and strigolactone treatments, including the counterintuitive ability of strigolactones either to promote or inhibit Shoot branching, depending on the auxin transport status of the plant. Consistent with this predicted mode of action, strigolactone signalling was found to trigger PIN1 depletion from the plasma membrane of xylem parenchyma cells in the stem. This effect could be detected within 10 minutes of strigolactone treatment and was independent of protein synthesis but dependent on clathrin-mediated membrane trafficking. Together these results support the hypothesis that growth across the plant Shoot system is balanced by competition between Shoot apices for a common auxin transport path to the root and that strigolactones regulate Shoot branching by modulating this competition.

  • the arabidopsis max pathway controls Shoot branching by regulating auxin transport
    Current Biology, 2006
    Co-Authors: Tom Bennett, Christian Luschnig, Tobias Sieberer, Barbara Willett, Jonathan Booker, Ottoline Leyser
    Abstract:

    Summary Background Plants achieve remarkable plasticity in Shoot system architecture by regulating the activity of secondary Shoot Meristems, laid down in the axil of each leaf. Axillary meristem activity, and hence Shoot branching, is regulated by a network of interacting hormonal signals that move through the plant. Among these, auxin, moving down the plant in the main stem, indirectly inhibits axillary bud outgrowth, and an as yet undefined hormone, the synthesis of which in Arabidopsis requires MAX1, MAX3 , and MAX4, moves up the plant and also inhibits Shoot branching. Since the axillary buds of max4 mutants are resistant to the inhibitory effects of apically supplied auxin, auxin and the MAX-dependent hormone must interact to inhibit branching. Results Here we show that the resistance of max mutant buds to apically supplied auxin is largely independent of the known, AXR1-mediated, auxin signal transduction pathway. Instead, it is caused by increased capacity for auxin transport in max primary stems, which show increased expression of PIN auxin efflux facilitators. The max phenotype is dependent on PIN1 activity, but it is independent of flavonoids, which are known regulators of PIN-dependent auxin transport. Conclusions The MAX-dependent hormone is a novel regulator of auxin transport. Modulation of auxin transport in the stem is sufficient to regulate bud outgrowth, independent of AXR1-mediated auxin signaling. We therefore propose an additional mechanism for long-range signaling by auxin in which bud growth is regulated by competition between auxin sources for auxin transport capacity in the primary stem.

Siobhan A Braybrook - One of the best experts on this subject based on the ideXlab platform.

  • anisotropic growth is achieved through the additive mechanical effect of material anisotropy and elastic asymmetry
    eLife, 2018
    Co-Authors: Firas Bou Daher, Yuanjie Chen, Behruz Bozorg, Jack Clough, Henrik Jonsson, Siobhan A Braybrook
    Abstract:

    Fast directional growth is a necessity for the young seedling; after germination, it needs to quickly penetrate the soil to begin its autotrophic life. In most dicot plants, this rapid escape is due to the anisotropic elongation of the hypocotyl, the columnar organ between the root and the Shoot Meristems. Anisotropic growth is common in plant organs and is canonically attributed to cell wall anisotropy produced by oriented cellulose fibers. Recently, a mechanism based on asymmetric pectin-based cell wall elasticity has been proposed. Here we present a harmonizing model for anisotropic growth control in the dark-grown Arabidopsis thaliana hypocotyl: basic anisotropic information is provided by cellulose orientation) and additive anisotropic information is provided by pectin-based elastic asymmetry in the epidermis. We quantitatively show that hypocotyl elongation is anisotropic starting at germination. We present experimental evidence for pectin biochemical differences and wall mechanics providing important growth regulation in the hypocotyl. Lastly, our in silico modelling experiments indicate an additive collaboration between pectin biochemistry and cellulose orientation in promoting anisotropic growth.

  • anisotropic growth is achieved through the additive mechanical effect of material anisotropy and elastic asymmetry
    bioRxiv, 2018
    Co-Authors: Firas Bou Daher, Yuanjie Chen, Behruz Bozorg, Jack Clough, Henrik Jonsson, Siobhan A Braybrook
    Abstract:

    Fast directional growth is a necessity for the young seedling: after germination, the seedling needs to quickly reach through the soil to begin its autotrophic life. In most dicot plants, this rapid escape is due to the anisotropic elongation of the hypocotyl, the columnar organ between the root and the Shoot Meristems. Anisotropic growth is common in plant organs and is canonically attributed to cell wall anisotropy produced by oriented cellulose fibers. Recently, a mechanism based on asymmetric pectin-based cell wall elasticity has been proposed. Here we present a harmonizing model for anisotropic growth control in the dark-grown Arabidopsis hypocotyl: basic anisotropic information is provided by cellulose orientation) and additive anisotropic information is provided by pectin-based elastic asymmetry in the epidermis. We quantitatively show that hypocotyl elongation is anisotropic from germination. We present experimental evidence for pectin biochemical differences and wall mechanics providing important growth regulation in the hypocotyl. Lastly, our in silico modelling experiments indicate an additive combination for pectin biochemistry and cellulose orientation in promoting anisotropic growth.

Elliot M Meyerowitz - One of the best experts on this subject based on the ideXlab platform.

  • the overlapping and distinct roles of ham family genes in arabidopsis Shoot Meristems
    Frontiers in Plant Science, 2020
    Co-Authors: Han Han, Elliot M Meyerowitz, An Yan, Yuan Geng, Lei Guo, Xing Liu, Yun Zhou
    Abstract:

    In Arabidopsis Shoot apical Meristems (SAMs), a well-characterized regulatory loop between WUSCHEL (WUS) and CLAVATA3 (CLV3) maintains stem cell homeostasis by regulating the balance between cell proliferation and cell differentiation. WUS proteins, translated in deep cell layers, move into the overlaying stem cells to activate CLV3. The secreted peptide CLV3 then regulates WUS levels through a ligand-receptor mediated signaling cascade. CLV3 is specifically expressed in the stem cells and repressed in the deep cell layers despite presence of the WUS activator, forming an apical-basal polarity along the axis of the SAM. Previously, we proposed and validated a hypothesis that the HAIRY MERISTEM (HAM) family genes regulate this polarity, keeping the expression of CLV3 off in interior cells of the SAM. However, the specific role of each individual member of the HAM family in this process remains to be elucidated. Combining live imaging and molecular genetics, we have dissected the conserved and distinct functions of different HAM family members in control of CLV3 patterning in the SAMs and in the de novo Shoot stem cell niches as well.

  • Nitrate modulates stem cell dynamics in Arabidopsis Shoot Meristems through cytokinins
    Proceedings of the National Academy of Sciences, 2018
    Co-Authors: Benoit Landrein, Elliot M Meyerowitz, Pau Formosa-jordan, Alice Malivert, Christoph Schuster, Charles W. Melnyk, Weibing Yang, Colin Turnbull, James C. W. Locke, Henrik Jonsson
    Abstract:

    The Shoot apical meristem (SAM) is responsible for the generation of all the aerial parts of plants. Given its critical role, dynamical changes in SAM activity should play a central role in the adaptation of plant architecture to the environment. Using quantitative microscopy, grafting experiments, and genetic perturbations, we connect the plant environment to the SAM by describing the molecular mechanism by which cytokinins signal the level of nutrient availability to the SAM. We show that a systemic signal of cytokinin precursors mediates the adaptation of SAM size and organogenesis rate to the availability of mineral nutrients by modulating the expression of WUSCHEL, a key regulator of stem cell homeostasis. In time-lapse experiments, we further show that this mechanism allows Meristems to adapt to rapid changes in nitrate concentration, and thereby modulate their rate of organ production to the availability of mineral nutrients within a few days. Our work sheds light on the role of the stem cell regulatory network by showing that it not only maintains meristem homeostasis but also allows plants to adapt to rapid changes in the environment.

  • pattern formation during de novo assembly of the arabidopsis Shoot meristem
    Development, 2007
    Co-Authors: Sean P Gordon, Pradeep Das, Marcus G Heisler, Venugopala G Reddy, Carolyn Ohno, Elliot M Meyerowitz
    Abstract:

    Most multicellular organisms have a capacity to regenerate tissue after wounding. Few, however, have the ability to regenerate an entire new body from adult tissue. Induction of new Shoot Meristems from cultured root explants is a widely used, but poorly understood, process in which apical plant tissues are regenerated from adult somatic tissue through the de novo formation of Shoot Meristems. We characterize early patterning during de novo development of the Arabidopsis Shoot meristem using fluorescent reporters of known gene and protein activities required for Shoot meristem development and maintenance. We find that a small number of progenitor cells initiate development of new Shoot Meristems through stereotypical stages of reporter expression and activity of CUP-SHAPED COTYLEDON 2 (CUC2), WUSCHEL (WUS), PIN-FORMED 1 (PIN1), Shoot-MERISTEMLESS (STM), FILAMENTOUS FLOWER (FIL, also known as AFO), REVOLUTA (REV), ARABIDOPSIS THALIANA MERISTEM L1 LAYER (ATML1) and CLAVATA 3 (CLV3). Furthermore, we demonstrate a functional requirement for WUS activity during de novo Shoot meristem initiation. We propose that de novo Shoot meristem induction is an easily accessible system for the study of patterning and self-organization in the well-studied model organism Arabidopsis.

  • signaling of cell fate decisions by clavata3 in arabidopsis Shoot Meristems
    Science, 1999
    Co-Authors: Jennifer C Fletcher, Rudiger Simon, Ulrike Brand, Mark Running, Elliot M Meyerowitz
    Abstract:

    In higher plants, organogenesis occurs continuously from self-renewing apical Meristems. Arabidopsis thaliana plants with loss-of-function mutations in the CLAVATA (CLV1,2, and 3) genes have enlarged Meristems and generate extra floral organs. Genetic analysis indicates that CLV1, which encodes a receptor kinase, acts with CLV3 to control the balance between meristem cell proliferation and differentiation.CLV3 encodes a small, predicted extracellular protein.CLV3 acts nonautonomously in Meristems and is expressed at the meristem surface overlying the CLV1 domain. These proteins may act as a ligand-receptor pair in a signal transduction pathway, coordinating growth between adjacent meristematic regions.