THE CLAVATA1 GENE ENCODES A PUTATIVE RECEPTOR KINASE THAT CONTROLS SHOOT AND FLORAL MERISTEM SIZE IN ARABIDOPSIS

The shoot apical meristem is responsible for aboveground organ initiat ion in higher plants, accomplishing continuous organogenesis by mainta ining a pool of undifferentiated cells and directing descendant cells toward organ formation. Normally, proliferation and differentiation ar e balanced, so that the structure and size of the shoot meristem is ma intained. However, Arabidopsis plants homozygous for mutations at the CLAVATA1 (CLV1) locus accumulate excess undifferentiated cells. We des cribe the molecular cloning and expression pattern of the CLV1 gene. I t encodes a putative receptor kinase, suggesting a role in signal tran sduction. The extracellular domain is composed of 21 tandem leucine-ri ch repeats that resemble leucine-rich repeats found in animal hormone receptors. We provide evidence that CLV1 expression in the inflorescen ce is specifically associated with meristematic activity.