Core pathways controlling shoot meristem maintenance

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Chunghee Lee, Steven E. Clark

Published Online: Feb 27 2013

DOI: 10.1002/wdev.110

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Abstract Essential to the function of shoot meristems in plants to act as sites of continuous organ and tissue formation is the ability of cells within the meristem to remain undifferentiated and proliferate indefinitely. These are characteristics of the stem cells within meristems that are critical for their growth properties. Stem cells are found in tight association with the stem cell niche—those cells that signal to maintain stem cells. Shoot meristems are unique among stem cell systems in that the stem cell niche is a constantly changing population of recent daughter stem cells. Recent progress from Arabidopsis and other systems have uncovered a large number of genes with defined roles in meristem structure and maintenance. This review will focus on well‐studied pathways that represent signaling between the stem cells and the niche, that prevent ectopic differentiation of stem cells, that regulate the chromatin status of stem cell factors, and that reveal intersection of hormone signaling and meristem maintenance. WIREs Dev Biol 2013, 2:671–684. doi: 10.1002/wdev.110 This article is categorized under: Gene Expression and Transcriptional Hierarchies > Cellular Differentiation Plant Development > Vegetative Development Plant Development > Inflorescence, Flower, and Fruit Development

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The shoot meristem. (a) A scanning electron micrograph of an Arabidopsis shoot apical meristem. Recently formed organ primordia are numbered from oldest to youngest. The CZ region, PZ region, and sites of nascent organ primordia are false‐colored yellow, blue, and dark blue, respectively. (b) Diagrammatic cross section of a shoot meristem. The L1, L2, and L3 layers of cells in the meristem center are indicated. The region of stem cells is indicated, and individual stem cells are shown (black cells) along with their predicted cell fates. Arrows indicate the fate of cells over developmental time, not the movement of cells.

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A model for CLAVATA (CLV) signaling. In the absence of CLV3 ligand, CLV1 and CLV2/CRN complexes are inactive, allowing POL/PLL1 to (likely indirectly) promote WUS transcription. Mature and processed CLV3 activates the receptor complexes, repressing POL/PLL1. In the absence of POL/PLL1 activity, WUS transcription is not maintained. The CLV1‐redundant BAM receptors are not included for clarity.

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