XVI International Botanical Congess

The creation of cells in shoot apical meristems of flowering plants is precisely balanced against the departure of cells. To learn the mechanism of this control, my laboratory has isolated a series of mutants of Arabidopsis thaliana in which shoot apical meristems progressively enlarge. One such mutant is in the CLAVATA1 gene, this gene codes for a transmembrane receptor kinase with an extracellular protein-binding domain. The gene is expressed in the central core of the meristem. We have recently cloned CLAVATA3, a gene that acts in the same pathway as CLAVATA1. It appears to code for a small extracellular protein, whose RNA is found in the cells above those expressing CLAVATA1, in what is classically defined as the central zone. CLV3 may thus be the CLV1 ligand, and the central zone may control the growth of the region under it by a receptor kinase pathway.