The Experts below are selected from a list of 8025 Experts worldwide ranked by ideXlab platform
Elliot M Meyerowitz - One of the best experts on this subject based on the ideXlab platform.
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calcium signals are necessary to establish auxin transporter polarity in a Plant Stem cell niche
Nature Communications, 2019Co-Authors: Ting Li, Paul T. Tarr, Marcus G Heisler, Neha Bhatia, Alphan Altinok, Eldad Afik, Pauline Durandsmet, Julian I Schroeder, Elliot M MeyerowitzAbstract:In Plants mechanical signals pattern morphogenesis through the polar transport of the hormone auxin and through regulation of interphase microtubule (MT) orientation. To date, the mechanisms by which such signals induce changes in cell polarity remain unknown. Through a combination of time-lapse imaging, and chemical and mechanical perturbations, we show that mechanical stimulation of the SAM causes transient changes in cytoplasmic calcium ion concentration (Ca2+) and that transient Ca2+ response is required for downstream changes in PIN-FORMED 1 (PIN1) polarity. We also find that dynamic changes in Ca2+ occur during development of the SAM and this Ca2+ response is required for changes in PIN1 polarity, though not sufficient. In contrast, we find that Ca2+ is not necessary for the response of MTs to mechanical perturbations revealing that Ca2+ specifically acts downstream of mechanics to regulate PIN1 polarity response.
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cell cycle control by nuclear sequestration of cdc20 and cdh1 mrna in Plant Stem cells
Molecular Cell, 2017Co-Authors: Weibing Yang, Elliot M Meyerowitz, Raymond WightmanAbstract:In eukaryotes, most RNA molecules are exported into the cytoplasm after transcription. Long noncoding RNAs (lncRNAs) reside and function primarily inside the nucleus, but nuclear localization of mRNAs has been considered rare in both animals and Plants. Here we show that Arabidopsis anaphase-promoting complex/cyclosome (APC/C) coactivator genes CDC20 and CCS52B (CDH1 ortholog) are co-expressed with their target cyclin B genes (CYCBs) during mitosis. CYCB transcripts can be exported and translated; however, CDC20 and CCS52B mRNAs are confined to the nucleus at prophase, and the cognate proteins are not translated until the redistribution of the mRNAs to the cytoplasm after nuclear envelope breakdown (NEBD) at prometaphase. The 5′ untranslated region (UTR) plays dual roles in CDC20 mRNA nuclear localization and translation. Mitotic accumulation of CDC20 and CCS52B transcripts enables the timely and rapid activation of APC/C, while the nuclear sequestration of these transcripts at prophase appears to protect cyclins from precocious degradation.
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cell cycle control by nuclear sequestration of cdc20 and cdh1 mrna in Plant Stem cells
bioRxiv, 2017Co-Authors: Weibing Yang, Raymond Wightman, Elliot M MeyerowitzAbstract:In eukaryotic cells, most RNA molecules are exported into the cytoplasm after being transcribed in the nucleus. Long noncoding RNAs (lncRNAs) have been found to reside and function primarily inside the nucleus, but nuclear localization of protein-coding messenger RNAs (mRNAs) has been considered rare in both animals and Plants. Here we show that two mRNAs, transcribed from the CDC20 and CCS52B (Plant orthologue of CDH1) genes, are specifically sequestered inside the nucleus during the cell cycle. CDC20 and CDH1 both function as coactivators of the anaphase-promoting complex or cyclosome (APC/C) E3 ligase to trigger cyclin B (C YCB) destruction. In the Arabidopsis thaliana shoot apical meriStem (SAM), we find CDC20 and CCS52B are co-expressed with CYCBs in mitotic cells. CYCB transcripts can be exported and translated, whereas CDC20 and CCS52B mRNAs are strictly confined to the nucleus at prophase and the cognate proteins are not translated until the redistribution of the mRNAs to the cytoplasm after nuclear envelope breakdown (NEBD) at prometaphase. The 59 untranslated region (UTR) is necessary and sufficient for CDC20 mRNA nuclear localization as well as protein translation. Mitotic enrichment of CDC20 and CCS52B transcripts enables the timely and rapid activation of APC/C, while their nuclear sequestration at prophase appears to protect cyclins from precocious degradation.
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An epidermis-driven mechanism positions and scales Stem cell niches in Plants.
Science Advances, 2016Co-Authors: Jérémy Gruel, Christoph Schuster, Benoit Landrein, Paul T. Tarr, Yassin Refahi, Arun Sampathkumar, Olivier Hamant, Elliot M Meyerowitz, Henrik JönssonAbstract:How molecular patterning scales to organ size is highly debated in developmental biology. We explore this question for the characteristic gene expression domains of the Plant Stem cell niche residing in the shoot apical meriStem. We show that a combination of signals originating from the epidermal cell layer can correctly pattern the key gene expression domains and notably leads to adaptive scaling of these domains to the size of the tissue. Using live imaging, we experimentally confirm this prediction. The identified mechanism is also sufficient to explain de novo Stem cell niches in emerging flowers. Our findings suggest that the deformation of the tissue transposes meriStem geometry into an instructive scaling and positional input for the apical Plant Stem cell niche.
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Plant Stem cell maintenance by transcriptional cross regulation of related receptor kinases
Development, 2015Co-Authors: Paul T. Tarr, Zachary L Nimchuk, Yun Zhou, Brenda A Peterson, Elliot M MeyerowitzAbstract:The CLAVATA3 (CLV3)-CLAVATA1 (CLV1) ligand-receptor kinase pair negatively regulates shoot Stem cell proliferation in Plants. clv1 null mutants are weaker in phenotype than clv3 mutants, but the clv1 null phenotype is enhanced by mutations in the related receptor kinases BARELY ANY MERIStem 1, 2 and 3 (BAM1, 2 and 3). The basis of this genetic redundancy is unknown. Here, we demonstrate that the apparent redundancy in the CLV1 clade is in fact due to the transcriptional repression of BAM genes by CLV1 signaling. CLV1 signaling in the rib meriStem (RM) of the shoot apical meriStem is necessary and sufficient for Stem cell regulation. CLV3-CLV1 signaling in the RM represses BAM expression in wild-type Arabidopsis Plants. In clv1 mutants, ectopic BAM expression in the RM partially complements the loss of CLV1. BAM regulation by CLV1 is distinct from CLV1 regulation of WUSCHEL, a proposed CLV1 target gene. In addition, quadruple receptor mutants are stronger in phenotype than clv3, pointing to the existence of additional CLV1/BAM ligands. These data provide an explanation for the genetic redundancy seen in the CLV1 clade and reveal a novel feedback operating in the control of Plant Stem cells.
Henrik Jönsson - One of the best experts on this subject based on the ideXlab platform.
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a model of protein interactions for regulating Plant Stem cells
bioRxiv, 2017Co-Authors: Jérémy Gruel, Benoit Landrein, Julia Deichmann, Thomas Hitchcock, Henrik JönssonAbstract:The Plant shoot apical meriStem holds a Stem cell niche from which all aerial organs originate. Using a computational approach we show that a mixture of monomers and heterodimers of the transcription factors WUSCHEL and HAIRY MERIStem is sufficient to pattern the Stem cell niche, and predict that immobile heterodimers form a regulatory pocket surrounding the Stem cells. The model achieves to reproduce an array of perturbations, including mutants and tissue size modifications. We also show its ability to reproduce the recently observed dynamical shift of the Stem cell niche during the development of an axillary meriStem. The work integrates recent experimental results to answer the longstanding question of how the asymmetry of expression between the Stem cell marker CLAVATA3 and its activator WUSCHEL is achieved, and recent findings of plasticity in the syStem.
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An epidermis-driven mechanism positions and scales Stem cell niches in Plants.
Science Advances, 2016Co-Authors: Jérémy Gruel, Christoph Schuster, Benoit Landrein, Paul T. Tarr, Yassin Refahi, Arun Sampathkumar, Olivier Hamant, Elliot M Meyerowitz, Henrik JönssonAbstract:How molecular patterning scales to organ size is highly debated in developmental biology. We explore this question for the characteristic gene expression domains of the Plant Stem cell niche residing in the shoot apical meriStem. We show that a combination of signals originating from the epidermal cell layer can correctly pattern the key gene expression domains and notably leads to adaptive scaling of these domains to the size of the tissue. Using live imaging, we experimentally confirm this prediction. The identified mechanism is also sufficient to explain de novo Stem cell niches in emerging flowers. Our findings suggest that the deformation of the tissue transposes meriStem geometry into an instructive scaling and positional input for the apical Plant Stem cell niche.
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Plant Stem cell maintenance involves direct transcriptional repression of differentiation program
Molecular Systems Biology, 2013Co-Authors: Jérémy Gruel, Henrik Jönsson, Carolyn Ohno, Ram Kishor Yadav, Mariano Perales, Marcus G Heisler, Thomas GirkeAbstract:In animal syStems, master regulatory transcription factors (TFs) mediate Stem cell maintenance through a direct transcriptional repression of differentiation promoting TFs. Whether similar mechanisms operate in Plants is not known. In Plants, shoot apical meriStems serve as reservoirs of Stem cells that provide cells for all above ground organs. WUSCHEL, a homeodomain TF produced in cells of the niche, migrates into adjacent cells where it specifies Stem cells. Through high-resolution genomic analysis, we show that WUSCHEL represses a large number of genes that are expressed in differentiating cells including a group of differentiation promoting TFs involved in leaf development. We show that WUS directly binds to the regulatory regions of differentiation promoting TFs; KANADI1, KANADI2, ASYMMETRICLEAVES2 and YABBY3 to repress their expression. Predictions from a computational model, supported by live imaging, reveal that WUS-mediated repression prevents premature differentiation of Stem cell progenitors, being part of a minimal regulatory network for meriStem maintenance. Our work shows that direct transcriptional repression of differentiation promoting TFs is an evolutionarily conserved logic for Stem cell regulation.
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wuschel protein movement mediates Stem cell homeostasis in the arabidopsis shoot apex
Genes & Development, 2011Co-Authors: Ram Kishor Yadav, Jérémy Gruel, Henrik Jönsson, Mariano Perales, Thomas Girke, G V ReddyAbstract:WUSCHEL (WUS) is a homeodomain transcription factor produced in cells of the niche/organizing center (OC) of shoot apical meriStems. WUS specifies Stem cell fate and also restricts its own levels by activating a negative regulator, CLAVATA3 (CLV3), in adjacent cells of the central zone (CZ). Here we show that the WUS protein, after being synthesized in cells of the OC, migrates into the CZ, where it activates CLV3 transcription by binding to its promoter elements. Using a computational model, we show that maintenance of the WUS gradient is essential to regulate Stem cell number. Migration of a Stem cell-inducing transcription factor into adjacent cells to activate a negative regulator, thereby restricting its own accumulation, is a theme that is unique to Plant Stem cell niches.
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Models of sequestration and receptor cross-talk for explaining multiple mutants in Plant Stem cell regulation
BMC Systems Biology, 2011Co-Authors: Patrik Sahlin, Pontus Melke, Henrik JönssonAbstract:Background Stem cells reside in a Plant's shoot meriStem throughout its life and are main regulators of above-ground Plant development. The Stem cell maintenance depends on a feedback network between the CLAVATA and WUSCHEL genes. The CLAVATA3 peptide binds to the CLAVATA1 receptor leading to WUSCHEL inhibition. WUSCHEL, on the other hand, activates CLAVATA3 expression. Recent experiments suggest a second pathway where CLAVATA3 inhibits WUSCHEL via the CORYNE receptor pathway. An interesting question, central for understanding the receptor signaling, is why the clavata1-11 null mutant has a weaker phenotype compared with the clavata1-1 non-null mutant. It has been suggested that this relies on interference from the mutated CLAVATA1 acting on the CORYNE pathway. Results We present two models for the CLAVATA-WUSCHEL feedback network including two receptor pathways for WUSCHEL repression and differing only by the hypothesized mechanisms for the clavata1-1 non-null mutant. The first model is an implementation of the previously suggested interference mechanism. The other model assumes an unaltered binding between CLAVATA3 and the mutated CLAVATA1 but with a loss of propagated signal into the cell. We optimize the models using data from wild type and four single receptor mutant experiments and use data from two receptor double mutant experiments in a validation step. Both models are able to explain all seven phenotypes and in addition qualitatively predict CLAVATA3 perturbations. The two models for the clavata1-1 mutant differ in the direct mechanism of the mutant, but they also predict other differences in the dynamics of the Stem cell regulating network. We show that the interference hypothesis leads to an abundance of receptors, while the loss-of-signal hypothesis leads to sequestration of CLAVATA3 and relies on degradation or internalization of the bound CLAVATA1 receptor. Conclusions Using computational modeling, we show that an interference hypothesis and a more parsimonious loss-of-signal hypothesis for a clavata1 non-null mutant both lead to behaviors predicting wild type and six receptor mutant experiments. Although the two models have identical implementations of the unperturbed feedback network for Stem cell regulation, we can point out model-predicted differences that may be resolved in future experiments.
Jan U Lohmann - One of the best experts on this subject based on the ideXlab platform.
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Structural basis for the complex DNA binding behavior of the Plant Stem cell regulator WUSCHEL
bioRxiv, 2020Co-Authors: Jeremy Sloan, Jana Hankenjos, Michael Gebert, Olga Ermakova, Andrea Gumiero, Gunter Stier, Klemens Wild, Irmgard Sinning, Jan U LohmannAbstract:Stem cells are one of the foundational evolutionary novelties that allowed the independent emergence of multicellularity in the Plant and animal lineages. In Plants, the homeodomain (HD) transcription factor WUSCHEL (WUS) is essential for the maintenance of Stem cells in the shoot apical meriStem. WUS has been reported to bind to diverse DNA motifs and to act as transcriptional activator and repressor. However, the mechanisms underlying this remarkable behavior have remained unclear. Here, we quantitatively delineate WUS binding to three divergent DNA motifs and resolve the relevant structural underpinnings. We show that WUS exhibits a strong binding preference for TGAA repeat sequences, while retaining the ability to weakly bind to TAAT elements. This behavior is attributable the formation of dimers through interactions of specific residues in the HD that stabilize WUS DNA interaction. Our results provide a mechanistic basis for dissecting WUS dependent regulatory networks in Plant Stem cell control.
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Plant Stem cells
Current Biology, 2016Co-Authors: Thomas Greb, Jan U LohmannAbstract:Among the trending topics in the life sciences, Stem cells have received a fair share of attention in the public debate — mostly in connection with their potential for biomedical application and therapies. While the promise of organ regeneration and the end of cancer have captured our imagination, it has gone almost unnoticed that Plant Stem cells represent the ultimate origin of much of the food we eat, the oxygen we breathe, as well the fuels we burn. Thus, Plant Stem cells may be ranked among the most important cells for human well-being. Research by many labs in the last decades has uncovered a set of independent Stem cell syStems that fulfill the specialized needs of Plant development and growth in four dimensions. Surprisingly, the cellular and molecular design of these syStems is remarkably similar, even across diverse species. In some long-lived Plants, such as trees, Plant Stem cells remain active over hundreds or even thousands of years, revealing the exquisite precision in the underlying control of proliferation, self-renewal and differentiation. In this minireview, we introduce the basic features of the three major Plant Stem cell syStems building on these facts, highlight their modular design at the level of cellular layout and regulatory underpinnings and briefly compare them with their animal counterparts.
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regulation of Plant Stem cell quiescence by a brassinosteroid signaling module
Developmental Cell, 2014Co-Authors: Josep Vilarrasablasi, Marypaz Gonzalezgarcia, David Frigola, Norma Fabregas, Konstantinos G Alexiou, Nuria Lopezbigas, Susana Rivas, Alain Jauneau, Jan U LohmannAbstract:Summary The quiescent center (QC) maintains the activity of the surrounding Stem cells within the root Stem cell niche, yet specific molecular players sustaining the low rate of QC cell division remain poorly understood. Here, we identified a R2R3-MYB transcription factor, BRAVO (BRASSINOSTEROIDS AT VASCULAR AND ORGANIZING CENTER), acting as a cell-specific repressor of QC divisions in the primary root of Arabidopsis . Ectopic BRAVO expression restricts overall root growth and ceases root regeneration upon damage of the Stem cells, demonstrating the role of BRAVO in counteracting Brassinosteroid (BR)-mediated cell division in the QC cells. Interestingly, BR-regulated transcription factor BES1 (BRI1-EMS SUPRESSOR 1) directly represses and physically interacts with BRAVO in vivo, creating a switch that modulates QC divisions at the root Stem cell niche. Together, our results define a mechanism for BR-mediated regulation of Stem cell quiescence in Plants.
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a quantitative and dynamic model for Plant Stem cell regulation
PLOS ONE, 2008Co-Authors: Florian Geier, Jan U Lohmann, Moritz Gerstung, Annette T Maier, Jens Timmer, Christian FleckAbstract:Plants maintain pools of totipotent Stem cells throughout their entire life. These Stem cells are embedded within specialized tissues called meriStems, which form the growing points of the organism. The shoot apical meriStem of the reference Plant Arabidopsis thaliana is subdivided into several distinct domains, which execute diverse biological functions, such as tissue organization, cell-proliferation and differentiation. The number of cells required for growth and organ formation changes over the course of a Plants life, while the structure of the meriStem remains remarkably constant. Thus, regulatory syStems must be in place, which allow for an adaptation of cell proliferation within the shoot apical meriStem, while maintaining the organization at the tissue level. To advance our understanding of this dynamic tissue behavior, we measured domain sizes as well as cell division rates of the shoot apical meriStem under various environmental conditions, which cause adaptations in meriStem size. Based on our results we developed a mathematical model to explain the observed changes by a cell pool size dependent regulation of cell proliferation and differentiation, which is able to correctly predict CLV3 and WUS over-expression phenotypes. While the model shows Stem cell homeostasis under constant growth conditions, it predicts a variation in Stem cell number under changing conditions. Consistent with our experimental data this behavior is correlated with variations in cell proliferation. Therefore, we investigate different signaling mechanisms, which could stabilize Stem cell number despite variations in cell proliferation. Our results shed light onto the dynamic constraints of Stem cell pool maintenance in the shoot apical meriStem of Arabidopsis in different environmental conditions and developmental states.
Robert Sablowski - One of the best experts on this subject based on the ideXlab platform.
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Plant Stem cell niches from signalling to execution
Current Opinion in Plant Biology, 2011Co-Authors: Robert SablowskiAbstract:The shoot and root meriStems contain small populations of Stem cells that constantly renew themselves while providing precursor cells to build all other Plant tissues and organs. Cell renewal, growth and differentiation in the meriStems are co-ordinated by networks of transcription factors and intercellular signals. The past two years have revealed how auxin and cytokinin signals are integrated with each other and with regulatory genes in the shoot and root meriStems. Small RNAs have also emerged as novel intercellular signals. Downstream of meriStem regulatory genes, links have been made to cell division control and chromatin function. Protection of genome integrity, partly through programmed cell death after DNA damage, has recently been revealed as a specialised function in Plant Stem cells.
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hypersensitivity to dna damage in Plant Stem cell niches
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Nick Fulcher, Robert SablowskiAbstract:The growing apices of Plants contain Stem cells that continually produce tissues, which, in the shoot, include the germline. These Stem cell populations remain active throughout the Plant's life, which can last for centuries, and are particularly exposed to environmental hazards that cause DNA damage and mutations. It is not known whether Plants have mechanisms to safeguard the genome specifically in these crucial cell populations. Here, we show that root and shoot Stem cells and their early descendants are selectively killed by mild treatment with radiomimetic drugs, x-rays, or mutations that disrupt DNA repair by nonhomologous end-joining. Stem cell death required transduction of DNA damage signals by the ATAXIA-TELANGIECTASIA MUTATED (ATM) kinase and, specifically in the root, also the ATM/RAD3-RELATED (ATR) kinase. Consistent with the absence of p53 and the core apoptotic machinery in Plants, death of the Stem cells did not show apoptotic but autolytic features as seen in other cases of Plant developmentally programmed cell death. We propose that Plants have independently evolved selective death as a stringent mechanism to safeguard genome integrity in their Stem cell populations.
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cytokinin and wuschel tie the knot around Plant Stem cells
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Robert SablowskiAbstract:Once upon a time, Plant development was all about hormones. Darwin (1) wrote nearly 130 years ago that “some influence,” later shown to be the phytohormone auxin, moved down the shoot to control the elongation of oat seedlings. In the 1950s, Skoog and Miller (2) showed that auxin and cytokinin control shoot regeneration in vitro, a technique that is extensively used to this day. With the rise of developmental genetics at the end of the 20th century, however, Plant development became focused on transcription factors and their exquisite expression patterns. More recently, both views have converged to explain how Plants develop intricate structures with precise expression patterns superimposed on cells that are constantly displaced by growth. This convergence was first exemplified by the role of auxin in patterning the growing root tip (3). In this issue of PNAS, Gordon et al. (4) shed light on the interplay of regulatory genes and cytokinin in the dynamic patterning of the opposite end of the Plant, the shoot meriStem.
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the dynamic Plant Stem cell niches
Current Opinion in Plant Biology, 2007Co-Authors: Robert SablowskiAbstract:Stem cells exist in specific locations called niches, where extracellular signals maintain Stem cell division and prevent differentiation. In Plants, the best characterised niches are within the shoot and root meriStems. Networks of regulatory genes and intercellular signals maintain meriStem structure in spite of constant cell displacement by division. Recent works have improved our understanding of how these networks function at the cellular and molecular levels, particularly in the control of the Stem cell population in the shoot meriStem. The meriStem regulatory genes have been found to function partly through localised control of widely used signals such as cytokinin and auxin. The retinoblastoma protein has also emerged as a key regulator of cell differentiation in the meriStems.
Sabrina Sabatini - One of the best experts on this subject based on the ideXlab platform.
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Plant and animal Stem cells similar yet different
Nature Reviews Molecular Cell Biology, 2014Co-Authors: Renze Heidstra, Sabrina SabatiniAbstract:The astonishingly long lives of Plants and their regeneration capacity depend on the activity of Plant Stem cells. As in animals, Stem cells reside in Stem cell niches, which produce signals that regulate the balance between self-renewal and the generation of daughter cells that differentiate into new tissues. Plant Stem cell niches are located within the meriStems, which are organized structures that are responsible for most post-embryonic development. The continuous organ production that is characteristic of Plant growth requires a robust regulatory network to keep the balance between pluripotent Stem cells and differentiating progeny. Components of this network have now been elucidated and provide a unique opportunity for comparing strategies that were developed in the animal and Plant kingdoms, which underlie the logic of Stem cell behaviour.
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Plant and animal Stem cells: similar yet different
Nature Reviews Molecular Cell Biology, 2014Co-Authors: Renze Heidstra, Sabrina SabatiniAbstract:As in animals, Plant Stem cells reside in Stem cell niches, which produce signals that regulate the balance between self-renewal and differentiation into new tissues. Continuous organ production that is characteristic of Plant growth requires a robust regulatory network to maintain this balance. Elucidating this network provides an opportunity to compare Plant and animal Stem cell strategies. The astonishingly long lives of Plants and their regeneration capacity depend on the activity of Plant Stem cells. As in animals, Stem cells reside in Stem cell niches, which produce signals that regulate the balance between self-renewal and the generation of daughter cells that differentiate into new tissues. Plant Stem cell niches are located within the meriStems, which are organized structures that are responsible for most post-embryonic development. The continuous organ production that is characteristic of Plant growth requires a robust regulatory network to keep the balance between pluripotent Stem cells and differentiating progeny. Components of this network have now been elucidated and provide a unique opportunity for comparing strategies that were developed in the animal and Plant kingdoms, which underlie the logic of Stem cell behaviour. Plant Stem cells, as in animals, are maintained in specialized microenvironments, which are known as Stem cell niches, where local signals from organizer cells act to prevent Stem cell differentiation. Interestingly, committed Stem cell progeny in Plants also provide versatile feedback signals to their Stem cell progenitors, thus becoming an indispensable component of the niche. Plant Stem cell niches are positioned within an organized group of dividing cells that are known as the meriStem. In the model Plant Arabidopsis thaliana , the shoot apical meriStem and the root meriStem are responsible for almost all the growth that occurs post-embryonically. Despite their similar organization, the RB protein is the only known protein involved in Stem cell function that is conserved between the animal and Plant kingdoms. Control of Stem cell differentiation in Plants involves a conserved module of peptide–receptor signalling that counteracts homeodomain transcription factor activity from the organizer cells. Both in Plants and animals the position of a functional Stem cell niche needs to be maintained within a dynamic structure. Also in Plants, in which the position of a Stem cell niche can be observed with cellular resolution from early embryonic stages onwards, several positional cues have been identified that involve crosstalk between hormone signalling, microRNAs and transcription factors. The root and shoot Stem cell niche organizers not only control the activity of surrounding Stem cells but also regulate differentiation of distant transit-amplifying cells that sustain coherent organ growth. As observed in several animal Stem cell niches the Plant organizers have the ability to replace (damaged) Stem cells. The A. thaliana shoot organizing cells consist of a constantly changing pool of cells that are apically replenished by Stem cell progeny, while shedding cells towards differentiation basally. The root organizing cells can act as long-term Stem cells by replacing damaged Stem cells, which ensures Stem cell niche longevity.