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Sarah Hake - One of the best experts on this subject based on the ideXlab platform.
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gene duplication at the fascicled ear1 locus controls the fate of inflorescence Meristem cells in maize
Proceedings of the National Academy of Sciences of the United States of America, 2021Co-Authors: China Lunde, Sarah Hake, David Jackson, Zuxin ZhangAbstract:Plant Meristems are self-renewing groups of pluripotent stem cells that produce lateral organs in a stereotypical pattern. Of interest is how the radially symmetrical Meristem produces laminar lateral organs. Both the male and female inflorescence Meristems of the dominant Fascicled ear (Fas1) mutant fail to grow as a single point and instead show deep branching. Positional cloning of two independent Fas1 alleles identified an ∼160 kb region containing two floral genes, the MADS-box gene, zmm8, and the YABBY gene, drooping leaf2 (drl2). Both genes are duplicated within the Fas1 locus and spatiotemporally misexpressed in the mutant inflorescence Meristems. Increased zmm8 expression alone does not affect inflorescence development; however, combined misexpression of zmm8, drl2, and their syntenic paralogs zmm14 and drl1, perturbs Meristem organization. We hypothesize that misexpression of the floral genes in the inflorescence and their potential interaction cause ectopic activation of a laminar program, thereby disrupting signaling necessary for maintenance of radially symmetrical inflorescence Meristems. Consistent with this hypothesis, RNA sequencing and in situ analysis reveal altered expression patterns of genes that define distinct zones of the Meristem and developing leaf. Our findings highlight the importance of strict spatiotemporal patterns of expression for both zmm8 and drl2 and provide an example of phenotypes arising from tandem gene duplications.
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the maize sbp box transcription factor encoded by tasselsheath4 regulates bract development and the establishment of Meristem boundaries
Development, 2010Co-Authors: George Chuck, David A Jackson, Clinton J Whipple, Sarah HakeAbstract:Plant architecture consists of repeating units called phytomers, each containing an internode, leaf and axillary Meristem. The formation of boundaries within the phytomer is necessary to differentiate and separate these three components, otherwise some will grow at the expense of others. The microRNA-targeted SBP-box transcription factor tasselsheath4 (tsh4) plays an essential role in establishing these boundaries within the inflorescence. tsh4 mutants display altered phyllotaxy, fewer lateral Meristems and ectopic leaves that grow at the expense of the Meristem. Double-mutant analyses of tsh4 and several highly branched mutants, such as ramosa1-3 and branched silkless1, demonstrated a requirement for tsh4 in branch Meristem initiation and maintenance. TSH4 protein, however, was localized throughout the inflorescence stem and at the base of lateral Meristems, but not within the Meristem itself. Double labeling of TSH4 with the ramosa2, branched silkless1 and knotted1 Meristem markers confirmed that TSH4 forms a boundary adjacent to all lateral Meristems. Indeed, double labeling of miR156 showed a Meristem-specific pattern complementary to that of TSH4, consistent with tsh4 being negatively regulated by this microRNA. Thus, downregulation of TSH4 by a combination of microRNAs and branching pathway genes allows the establishment of lateral Meristems and the repression of leaf initiation, thereby playing a major role in defining Meristem versus leaf boundaries.
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barren inflorescence2 encodes a co ortholog of the pinoid serine threonine kinase and is required for organogenesis during inflorescence and vegetative development in maize
Plant Physiology, 2007Co-Authors: Paula Mcsteen, China Lunde, Simon T Malcomber, Andrea L Skirpan, Elizabeth A Kellogg, Sarah HakeAbstract:Organogenesis in plants is controlled by Meristems. Axillary Meristems, which give rise to branches and flowers, play a critical role in plant architecture and reproduction. Maize (Zea mays) and rice (Oryza sativa) have additional types of axillary Meristems in the inflorescence compared to Arabidopsis (Arabidopsis thaliana) and thus provide an excellent model system to study axillary Meristem initiation. Previously, we characterized the barren inflorescence2 (bif2) mutant in maize and showed that bif2 plays a key role in axillary Meristem and lateral primordia initiation in the inflorescence. In this article, we cloned bif2 by transposon tagging. Isolation of bif2-like genes from seven other grasses, along with phylogenetic analysis, showed that bif2 is a co-ortholog of PINOID (PID), which regulates auxin transport in Arabidopsis. Expression analysis showed that bif2 is expressed in all axillary Meristems and lateral primordia during inflorescence and vegetative development in maize and rice. Further phenotypic analysis of bif2 mutants in maize illustrates additional roles of bif2 during vegetative development. We propose that bif2/PID sequence and expression are conserved between grasses and Arabidopsis, attesting to the important role they play in development. We provide further support that bif2, and by analogy PID, is required for initiation of both axillary Meristems and lateral primordia.
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the interaction of two homeobox genes brevipedicellus and pennywise regulates internode patterning in the arabidopsis inflorescence
The Plant Cell, 2003Co-Authors: Harley M S Smith, Sarah HakeAbstract:Plant architecture results from the activity of the shoot apical Meristem, which initiates leaves, internodes, and axillary Meristems. KNOTTED1-like homeobox (KNOX) genes are expressed in specific patterns in the shoot apical Meristem and play important roles in plant architecture. KNOX proteins interact with BEL1-like (BELL) homeodomain proteins and together bind a target sequence with high affinity. We have obtained a mutation in one of the Arabidopsis BELL genes, PENNYWISE (PNY), that appears phenotypically similar to the KNOX mutant brevipedicellus (bp). Both bp and pny have randomly shorter internodes and display a slight increase in the number of axillary branches. The double mutant shows a synergistic phenotype of extremely short internodes interspersed with long internodes and increased branching. PNY is expressed in inflorescence and floral Meristems and overlaps with BP in a discrete domain of the inflorescence Meristem where we propose the internode is patterned. The physical association of the PNY and BP proteins suggests that they participate in a complex that regulates early patterning events in the inflorescence Meristem.
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the control of maize spikelet Meristem fate by the apetala2 like gene indeterminate spikelet1
Genes & Development, 1998Co-Authors: George Chuck, Robert B Meeley, Sarah HakeAbstract:The orderly production of Meristems with specific fates is crucial for the proper elaboration of plant architecture. The maize inflorescence Meristem branches several times to produce lateral Meristems with determinate fates. The first Meristem formed, the spikelet pair Meristem, produces two spikelet Meristems, each of which produces two floral Meristems. We have identified a gene called indeterminate spikelet1 (ids1) that specifies a determinate spikelet Meristem fate and thereby limits the number of floral Meristems produced. In the absence of ids1 gene function, the spikelet Meristem becomes indeterminate and produces additional florets. Members of the grass family vary in the number of florets within their spikelets, suggesting that ids1 may play a role in inflorescence architecture in other grass species. ids1 is a member of the APETALA2 (AP2) gene family of transcription factors that has been implicated in a wide range of plant development roles. Expression of ids1 was detected in many types of lateral organ primordia as well as spikelet Meristems. Our analysis of the ids1 mutant phenotype and expression pattern indicates that ids1 specifies determinate fates by suppressing indeterminate growth within the spikelet Meristem.
Klaus Theres - One of the best experts on this subject based on the ideXlab platform.
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two step regulation of a Meristematic cell population acting in shoot branching in arabidopsis
PLOS Genetics, 2016Co-Authors: Bihai Shi, Robert Sablowski, Carolyn Ohno, Klaus Theres, Jin Wang, Quan Wang, Cui Zhang, Caihuan Tian, Marcus G Heisler, Ying WangAbstract: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.
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Lateral suppressor and Goblet act in hierarchical order to regulate ectopic Meristem formation at the base of tomato leaflets
Plant Journal, 2015Co-Authors: Susanne Rossmann, Wouter Kohlen, Alice Hasson, Klaus TheresAbstract:Summary In seed plants, new axes of growth are established by the formation of Meristems, groups of pluripotent cells that maintain themselves and initiate the formation of lateral organs. After embryonic development, secondary shoot Meristems form in the boundary zones between the shoot apical Meristem and leaf primordia, the leaf axils. In addition, many plant species develop ectopic Meristems at different positions of the plant body. In the compound tomato leaf, ectopic Meristems can initiate at the base of leaflets, which are delimited by two distinct boundary zones, referred to as the proximal (PLB) and distal (DLB) leaflet boundaries. We demonstrate that the two leaflet boundaries differ from each other and that ectopic Meristem formation is strictly limited to the DLB. Our data suggest that the DLB harbours a group of pluripotent cells that seems to be the launching pad for Meristem formation. Initiation of these Meristems is dependent on the activities of the transcriptional regulators Goblet (Gob) and Lateral suppressor (Ls), specifically expressed in the DLB. Gob and Ls act in hierarchical order, because Ls transcript accumulation is dependent on Gob activity, but not vice versa. Ectopic Meristem formation at the DLB is also observed in other seed plants, like Cardamine pratensis, indicating that it is part of a widespread developmental program. Ectopic Meristem formation leads to an increase in the number of buds, enhances the capacity for survival and opens the route to vegetative propagation.
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Auxin depletion from the leaf axil conditions competence for axillary Meristem formation in Arabidopsis and tomato
The Plant cell, 2014Co-Authors: Quan Wang, Wouter Kohlen, Susanne Rossmann, Teva Vernoux, Klaus TheresAbstract: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.
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lost Meristems genes regulate cell differentiation of central zone descendants in arabidopsis shoot Meristems
Plant Journal, 2010Co-Authors: Silke Schulze, Barbara Nicole Schafer, Eneida Abreu Parizotto, Olivier Voinnet, Klaus TheresAbstract:Meristems of seed plants continuously produce new cells for incorporation into maturing tissues. A tightly controlled balance between cell proliferation in the center and cell differentiation at the periphery of the shoot Meristem maintains its integrity. Here, we describe the role of three GRAS genes, named LOST MeristemS genes, in shoot apical Meristem maintenance and axillary Meristem formation. Under short photoperiods, the lom1 lom2 and lom1 lom2 lom3 mutants have arrested Meristems characterized by an over-proliferation of Meristematic cells and loss of polar organization. They also show early arrest of axillary Meristem development and formation of ectopic Meristematic cell clusters within the stem. LOM1 and LOM2 transcripts accumulate in the peripheral and basal zones of the SAM and in vascular strands. We show that LOM1 and LOM2 promote cell differentiation at the periphery of shoot Meristems and help to maintain their polar organization.
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interplay of mir164 cup shaped cotyledon genes and lateral suppressor controls axillary Meristem formation in arabidopsis thaliana
Plant Journal, 2008Co-Authors: Smita Raman, Thomas Greb, Thomas Blein, Alexis Peaucelle, Patrick Laufs, Klaus TheresAbstract:Aerial architecture in higher plants is established post-embryonically by the inception of new Meristems in the axils of leaves. These axillary Meristems develop into side shoots or flowers. In Arabidopsis, the NAC domain transcription factors CUP SHAPED COTYLEDON1 (CUC1), CUC2 and CUC3 function redundantly in initiating the shoot apical Meristem and establishing organ boundaries. Transcripts of CUC1 and CUC2 are targeted for degradation by miR164. In this study, we show that cuc3-2 mutants are impaired in axillary Meristem initiation. Overexpression of miR164 in the cuc3-2 mutant caused an almost complete block of axillary Meristem formation. Conversely, mir164 mutants and plants harbouring miR164-resistant alleles of CUC1 or CUC2 developed accessory buds in leaf axils. Collectively, these experiments reveal that, in addition to CUC3, redundant functions of CUC1 and CUC2 as well as miR164 regulation are required for the establishment of axillary Meristems. Studies on LAS transcript accumulation in mir164 triple mutants and cuc3-2 plants overexpressing miR164 suggest that regulation of axillary Meristem formation by miR164 is mediated through CUC1 and CUC2, which in turn regulate LAS.
David Jackson - One of the best experts on this subject based on the ideXlab platform.
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gene duplication at the fascicled ear1 locus controls the fate of inflorescence Meristem cells in maize
Proceedings of the National Academy of Sciences of the United States of America, 2021Co-Authors: China Lunde, Sarah Hake, David Jackson, Zuxin ZhangAbstract:Plant Meristems are self-renewing groups of pluripotent stem cells that produce lateral organs in a stereotypical pattern. Of interest is how the radially symmetrical Meristem produces laminar lateral organs. Both the male and female inflorescence Meristems of the dominant Fascicled ear (Fas1) mutant fail to grow as a single point and instead show deep branching. Positional cloning of two independent Fas1 alleles identified an ∼160 kb region containing two floral genes, the MADS-box gene, zmm8, and the YABBY gene, drooping leaf2 (drl2). Both genes are duplicated within the Fas1 locus and spatiotemporally misexpressed in the mutant inflorescence Meristems. Increased zmm8 expression alone does not affect inflorescence development; however, combined misexpression of zmm8, drl2, and their syntenic paralogs zmm14 and drl1, perturbs Meristem organization. We hypothesize that misexpression of the floral genes in the inflorescence and their potential interaction cause ectopic activation of a laminar program, thereby disrupting signaling necessary for maintenance of radially symmetrical inflorescence Meristems. Consistent with this hypothesis, RNA sequencing and in situ analysis reveal altered expression patterns of genes that define distinct zones of the Meristem and developing leaf. Our findings highlight the importance of strict spatiotemporal patterns of expression for both zmm8 and drl2 and provide an example of phenotypes arising from tandem gene duplications.
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The CLV3 Homolog in Setaria viridis Selectively Controls Inflorescence Meristem Size.
Frontiers in plant science, 2021Co-Authors: Chuanmei Zhu, Lei Liu, Olivia Crowell, Hui Zhao, David JacksonAbstract:The CLAVATA pathway controls Meristem size during inflorescence development in both eudicots and grasses, and is initiated by peptide ligands encoded by CLV3/ESR-related (CLE) genes. While CLV3 controls all shoot Meristems in Arabidopsis, evidence from cereal grasses indicates that different Meristem types are regulated by different CLE peptides. The rice peptide FON2 primarily controls the size of the floral Meristem, whereas the orthologous peptides CLE7 and CLE14 in maize have their most dramatic effects on inflorescence and branch Meristems, hinting at diversification among CLE responses in the grasses. Setaria viridis is more closely related to maize than to rice, so can be used to test whether the maize CLE network can be generalized to all members of subfamily Panicoideae. We used CRISPR-Cas9 in S. viridis to knock out the SvFON2 gene, the closest homolog to CLV3 and FON2. Svfon2 mutants developed larger inflorescence Meristems, as in maize, but had normal floral Meristems, unlike Osfon2, suggesting a panicoid-specific CLE network. Vegetative traits such as plant height, tiller number and leaf number were not significantly different between mutant and wild type plants, but time to heading was shorter in the mutants. In situ hybridization showed strong expression of Svfon2 in the inflorescence and branch Meristems, consistent with the mutant phenotype. Using bioinformatic analysis, we predicted the co-expression network of SvFON2 and its signaling components, which included genes known to control inflorescence architecture in maize as well as genes of unknown function. The similarity between SvFON2 function in Setaria and maize suggests that its developmental specialization in inflorescence Meristem control may be shared among panicoid grasses.
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grass Meristems ii inflorescence architecture flower development and Meristem fate
Plant and Cell Physiology, 2013Co-Authors: Wakana Tanaka, David Jackson, Michael Pautler, Hiroyuki HiranoAbstract:Plant development depends on the activity of various types of Meristems that generate organs such as leaves and floral organs throughout the life cycle. Grass species produce complex inflorescences and unique flowers. The grass inflorescence is composed of different types of branches, including a specialized branch called a spikelet. The spikelet is a special unit of the inflorescence and forms one to several florets, depending on the species. In the floret, floral organs such as perianth organs, carpels and stamens are formed. In Arabidopsis, because the inflorescence Meristem (IM) forms the floral Meristems (FMs) directly on its flanks, the change of Meristem fate is relatively simple. In contrast, in grasses, different types of Meristem, such as the IM, the branch Meristem (BM), the spikelet pair Meristem (SPM) in some grasses, the spikelet Meristem (SM) and the FM, are responsible for the elaboration of their complex inflorescences and flowers. Therefore, sequential changes of Meristem fate are required, and a number of genes involved in the specification of the fate of each Meristem have been identified. In this review, we focus on the following issues concerning the fate of the reproductive Meristems in two grass species, maize (Zea mays) and rice (Oryza sativa): (i) Meristem regulation during inflorescence development; (ii) specification and fate change of the BM and the SM; (iii) determinacy of the FM; and (iv) communication between the Meristem and lateral organs.
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the relationship between auxin transport and maize branching
Plant Physiology, 2008Co-Authors: Andrea Gallavotti, Robert Schmidt, Yan Yang, David JacksonAbstract:Maize (Zea mays) plants make different types of vegetative or reproductive branches during development. Branches develop from axillary Meristems produced on the flanks of the vegetative or inflorescence shoot apical Meristem. Among these branches are the spikelets, short grass-specific structures, produced by determinate axillary spikelet-pair and spikelet Meristems. We investigated the mechanism of branching in maize by making transgenic plants expressing a native expressed endogenous auxin efflux transporter (ZmPIN1a) fused to yellow fluorescent protein and a synthetic auxin-responsive promoter (DR5rev) driving red fluorescent protein. By imaging these plants, we found that all maize branching events during vegetative and reproductive development appear to be regulated by the creation of auxin response maxima through the activity of polar auxin transporters. We also found that the auxin transporter ZmPIN1a is functional, as it can rescue the polar auxin transport defects of the Arabidopsis (Arabidopsis thaliana) pin1-3 mutant. Based on this and on the groundbreaking analysis in Arabidopsis and other species, we conclude that branching mechanisms are conserved and can, in addition, explain the formation of axillary Meristems (spikelet-pair and spikelet Meristems) that are unique to grasses. We also found that BARREN STALK1 is required for the creation of auxin response maxima at the flanks of the inflorescence Meristem, suggesting a role in the initiation of polar auxin transport for axillary Meristem formation. Based on our results, we propose a general model for branching during maize inflorescence development.
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expression of maize knotted1 related homeobox genes in the shoot apical Meristem predicts patterns of morphogenesis in the vegetative shoot
Development, 1994Co-Authors: David Jackson, B Veit, Sarah HakeAbstract:In this paper we describe the expression patterns of a family of homeobox genes in maize and their relationship to organogenic domains in the vegetative shoot apical Meristem. These genes are related by sequence to KNOTTED1, a gene characterized by dominant neomorphic mutations which perturb specific aspects of maize leaf development. Four members of this gene family are expressed in shoot Meristems and the developing stem, but not in determinate lateral organs such as leaves or floral organs. The genes show distinct expression patterns in the vegetative shoot apical Meristem that together predict the site of leaf initiation and the basal limit of the vegetative ‘phytomer’ or segmentation unit of the shoot. These genes are also expressed in the inflorescence and floral Meristems, where their patterns of expression are more similar, and they are not expressed in root apical Meristems. These findings are discussed in relation to other studies of shoot apical Meristem organization as well as possible commonality of homeobox gene function in the animal and plant kingdoms.
Michael Pautler - One of the best experts on this subject based on the ideXlab platform.
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fasciated ear4 encodes a bzip transcription factor that regulates shoot Meristem size in maize
The Plant Cell, 2015Co-Authors: Michael Pautler, Mai Komatsu, Robert B Meeley, China Lunde, Andrea L Eveland, Therese Larue, Fang Yang, Rebecca Weeks, Erik Vollbrecht, Hajime SakaiAbstract: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.
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grass Meristems i shoot apical Meristem maintenance axillary Meristem determinacy and the floral transition
Plant and Cell Physiology, 2013Co-Authors: Michael Pautler, Wakana Tanaka, Hiroyuki Hirano, David A JacksonAbstract:The vegetative and reproductive shoot architectures displayed by members of the grass family are critical to reproductive success, and thus agronomic yield. Variation in shoot architecture is explained by the maintenance, activity and determinacy of Meristems, pools of pluripotent stem cells responsible for post-embryonic plant growth. This review summarizes recent progress in understanding the major properties of grass shoot Meristems, focusing on vegetative phase Meristems and the floral transition, primarily in rice and maize. Major areas of interest include: the control of Meristem homeostasis by the CLAVATA-WUSCHEL pathway and by hormones such as cytokinin; the initiation of axillary Meristems and the control of axillary Meristem dormancy; and the environmental and endogenous cues that regulate flowering time. In an accompanying paper, Tanaka et al. review subsequent stages of shoot development, including current knowledge of reproductive Meristem determinacy and the fate transitions associated with these Meristems. © 2013 The Author 2013.
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grass Meristems ii inflorescence architecture flower development and Meristem fate
Plant and Cell Physiology, 2013Co-Authors: Wakana Tanaka, David Jackson, Michael Pautler, Hiroyuki HiranoAbstract:Plant development depends on the activity of various types of Meristems that generate organs such as leaves and floral organs throughout the life cycle. Grass species produce complex inflorescences and unique flowers. The grass inflorescence is composed of different types of branches, including a specialized branch called a spikelet. The spikelet is a special unit of the inflorescence and forms one to several florets, depending on the species. In the floret, floral organs such as perianth organs, carpels and stamens are formed. In Arabidopsis, because the inflorescence Meristem (IM) forms the floral Meristems (FMs) directly on its flanks, the change of Meristem fate is relatively simple. In contrast, in grasses, different types of Meristem, such as the IM, the branch Meristem (BM), the spikelet pair Meristem (SPM) in some grasses, the spikelet Meristem (SM) and the FM, are responsible for the elaboration of their complex inflorescences and flowers. Therefore, sequential changes of Meristem fate are required, and a number of genes involved in the specification of the fate of each Meristem have been identified. In this review, we focus on the following issues concerning the fate of the reproductive Meristems in two grass species, maize (Zea mays) and rice (Oryza sativa): (i) Meristem regulation during inflorescence development; (ii) specification and fate change of the BM and the SM; (iii) determinacy of the FM; and (iv) communication between the Meristem and lateral organs.
Elliot M Meyerowitz - One of the best experts on this subject based on the ideXlab platform.
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the stem cell niche in leaf axils is established by auxin and cytokinin in arabidopsis
The Plant Cell, 2014Co-Authors: Elliot M Meyerowitz, Ying Wang, Jin Wang, Bihai Shi, Yuling JiaoAbstract:Plants differ from most animals in their ability to initiate new cycles of growth and development, which relies on the establishment and activity of branch Meristems harboring new stem cell niches. In seed plants, this is achieved by axillary Meristems, which are established in the axil of each leaf base and develop into lateral branches. Here, we describe the initial processes of Arabidopsis thaliana axillary Meristem initiation. Using reporter gene expression analysis, we find that axillary Meristems initiate from leaf axil cells with low auxin through stereotypical stages. Consistent with this, ectopic overproduction of auxin in the leaf axil efficiently inhibits axillary Meristem initiation. Furthermore, our results demonstrate that auxin efflux is required for the leaf axil auxin minimum and axillary Meristem initiation. After lowering of auxin levels, a subsequent cytokinin signaling pulse is observed prior to axillary Meristem initiation. Genetic analysis suggests that cytokinin perception and signaling are both required for axillary Meristem initiation. Finally, we show that cytokinin overproduction in the leaf axil partially rescue axillary Meristem initiation-deficient mutants. These results define a mechanistic framework for understanding axillary Meristem initiation.
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plant stem cell signaling involves ligand dependent trafficking of the clavata1 receptor kinase
Current Biology, 2011Co-Authors: Zachary L Nimchuk, Carolyn Ohno, Xiang Qu, Paul T. Tarr, Elliot M MeyerowitzAbstract:Background: Cell numbers in above-ground Meristems of plants are thought to be maintained by a feedback loop driven by perception of the glycopeptide ligand CLAVATA3 (CLV3) by the CLAVATA1 (CLV1) receptor kinase and the CLV2/CORYNE (CRN) receptor-like complex [1]. CLV3 produced in the stem cells at the Meristem apex limits the expression level of the stem cell-promoting homeodomain protein WUSCHEL (WUS) in the cells beneath, where CLV1 and WUS RNA are localized. WUS downregulation nonautonomously reduces stem cell proliferation. Overexpression of CLV3 eliminates the stem cells, causing Meristem termination [2], and loss of CLV3 function allows Meristem overproliferation [3]. There are many questions regarding the CLV3/CLV1 interaction, including where in the Meristem it occurs, how it is regulated, and how it is that a large range of CLV3 concentrations gives no Meristem size phenotype [4]. Results: Here we use genetics and live imaging to examine the cell biology of CLV1 in Arabidopsis Meristematic tissue. We demonstrate that plasma membrane-localized CLV1 is reduced in concentration by CLV3, which causes trafficking of CLV1 to lytic vacuoles. We find that changes in CLV2 activity have no detectable effects on CLV1 levels. We also find that CLV3 appears to diffuse broadly in Meristems, contrary to a recent sequestration model [5]. Conclusions: This study provides a new model for CLV1 function in plant stem cell maintenance and suggests that downregulation of plasma membrane-localized CLV1 by its CLV3 ligand can account for the buffering of CLV3 signaling in the maintenance of stem cell pools in plants.
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pattern formation during de novo assembly of the arabidopsis shoot Meristem
Development, 2007Co-Authors: Sean P Gordon, Carolyn Ohno, Marcus G Heisler, Pradeep Das, Venugopala G Reddy, Elliot M MeyerowitzAbstract: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.
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Repression of AGAMOUS-LIKE 24 is a crucial step in promoting flower development.
Nature genetics, 2004Co-Authors: Toshiro Ito, Frank Wellmer, Elliot M MeyerowitzAbstract:Flower development begins as floral Meristems arise in succession on the flank of the inflorescence Meristem. Floral Meristem identity genes LEAFY (LFY) and APETALA1 (AP1) promote establishment and maintenance of floral identity in newly formed floral primordia. Without their activity, the floral primordia develop with inflorescence characteristics. The underlying molecular-genetic mechanism is unknown. Here we show that these phenotypes are due in large part to the ectopic expression of AGAMOUS-LIKE 24 (AGL24), a central regulator of floral Meristem identity. We present evidence that AGL24 is an early target of transcriptional repression by LFY and AP1. Without such repression, continued AGL24 expression in floral Meristems is sufficient to cause floral reversion regardless of the activation of floral organ identity genes. This indicates that LFY and AP1 promote floral development not only by positively regulating genes activated in flower development, but also by repressing AGL24, a promoter of inflorescence fate.
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signaling of cell fate decisions by clavata3 in arabidopsis shoot Meristems
Science, 1999Co-Authors: Jennifer C Fletcher, Ulrike Brand, Rudiger Simon, Mark Running, Elliot M MeyerowitzAbstract: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.