THE WIGGUM GENE IS REQUIRED FOR PROPER REGULATION OF FLORAL MERISTEM SIZE IN ARABIDOPSIS

The study of cell division control within developing tissues is centra l to understanding the processes of pattern formation. The floral meri stem of angiosperms gives rise to floral organs in a particular number and pattern. Despite its critical role, little is known about how cel l division is controlled in the floral meristem, and few genes involve d have been identified. We describe the phenotypic effects of mutation s in WIGGUM, a gene required for control of cell proliferation in the floral and apical meristem of Arabidopsis thaliana, wiggum flowers con tain more organs, especially sepals and petals, than found in wild-typ e flowers. This organ number phenotype correlates with specific size c hanges in the early floral meristem, preceding organ initiation. Genet ic studies suggest that WIGGUM acts on a similar process but in a sepa rate pathway than the CLAVATA1 and CLAVATA3 genes in meristem size reg ulation, and reveal interactions with other genes affecting meristem s tructure and identity. Analysis of double mutant phenotypes also revea ls a role for WIGGUM in apical meristem function. We propose that WIGG UM plays a role in restricting cell division relative to cellular diff erentiation in specific regions of the apical and floral meristems.