CLAVATA3 IS A SPECIFIC REGULATOR OF SHOOT AND FLORAL MERISTEM DEVELOPMENT AFFECTING THE SAME PROCESSES AS CLAVATA1

We have previously described the phenotype of Arabidopsis thaliana pla nts with mutations at the CLAVATA1 (CLV1) locus (Clark, S. E., Running , M. P. and Meyerowitz, E. M. (1993) Development 119, 397-418). Our in vestigations demonstrated that clv1 plants develop enlarged vegetative and inflorescence apical meristems, and enlarged and indeterminate fl oral meristems. Here, we present an analysis of mutations at a separat e locus, CLAVATA3 (CLV3), that disrupt meristem development in a manne r similar to clv1 mutations, clv3 plants develop enlarged apical meris tems as early as the mature embryo stage, clv3 floral meristems are al so enlarged compared with wild type, and maintain a proliferating meri stem throughout flower development, clv3 root meristems are unaffected , indicating that CLV3 is a specific regulator of shoot and floral mer istem development, We demonstrate that the strong clv3-2 mutant is lar gely epistatic to clv1 mutants, and that the semi-dominance of clv1 al leles is enhanced by double heterozygosity with clv3 alleles, suggesti ng that these genes work in the same pathway to control meristem devel opment. We propose that CLV1 and CLV3 are required to promote the diff erentiation of cells at the shoot and floral meristem.