HAIRY MERISTEM with WUSCHEL confines CLAVATA3 expression to the outer apical meristem layers

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Science  03 Aug 2018:
Vol. 361, Issue 6401, pp. 502-506
DOI: 10.1126/science.aar8638

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Enough but not too many stem cells

In the shoot apical meristem of plants, just the right number of stem cells generates a steady supply of cells with which to build differentiated tissues. Too few stem cells, and the plant cannot grow. Too many, and growth runs amok. Zhou et al. analyzed the controls on stem cell proliferation. They found that the HAIRY MERISTEM proteins define a domain within which WUSCHEL (WUS) cannot work, but beyond which WUS is left free to promote stem cell proliferation.

Science, this issue p. 502


The control of the location and activity of stem cells depends on spatial regulation of gene activities in the stem cell niche. Using computational and experimental approaches, we have tested and found support for a hypothesis for gene interactions that specify the Arabidopsis apical stem cell population. The hypothesis explains how the WUSCHEL gene product, synthesized basally in the meristem, induces CLAVATA3-expressing stem cells in the meristem apex but, paradoxically, not in the basal domain where WUSCHEL itself is expressed. The answer involves the activity of the small family of HAIRY MERISTEM genes, which prevent the activation of CLAVATA3 and which are expressed basally in the shoot meristem.

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