Without CLV3 (bottom), stem cell niches overgrow and lineages are larger.

MEYEROWITZ/NAS

To maintain a stem cell niche at a fixed size, the niche exerts control over both cell differentiation (how many cells functionally leave the niche) and cell division. G. Venugopala Reddy and Elliot Meyerowitz (Caltech, Pasadena, CA) now show that, in the growing shoots of plants, these two control points are separable in both time and space.

Their model was the shoot apical meristem (SAM). The SAM has a central zone (CZ) of stem cells plus various surrounding cells that make the transcription factor WUSCHEL. Although WUSCHEL creates a signal that promotes stem cell identity back in the CZ, it also induces these stem cells to produce CLAVATA3 (CLV3), an extracellular ligand that keeps WUSCHEL repressed centrally. This forces the inducing ring to keep its distance from the induced stem cells.

Reddy and...

The Rockefeller University Press
2005
The Rockefeller University Press
2005
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