UFO - AN ARABIDOPSIS GENE INVOLVED IN BOTH FLORAL MERISTEM AND FLORALORGAN DEVELOPMENT

We describe the role of the UNUSUAL FLORAL ORGANS (UFO) gene in Arabid opsis floral development based on a genetic and molecular characteriza tion of the phenotypes of nine ufo alleles. UFO is required for the pr oper identity of the floral meristem and acts in three different aspec ts of the process that distinguishes flowers from shoots. UFO is invol ved in establishing the whorled pattern of floral organs, controlling the determinacy of the floral meristem, and activating the APETALA3 an d PISTILLATA genes required for petal and stamen identity. In many res pects, UFO acts in a manner similar to LEAFY, but the ufo mutant pheno type also suggests an additional role for UFO in defining boundaries w ithin the floral primordia or controlling cell proliferation during fl oral organ growth. Finally, genetic interactions that prevent flower f ormation and lead to the generation of filamentous structures implicat e UFO as a member of a new, large, and diverse class of genes in Arabi dopsis necessary for flower formation.