Transcriptional activator involved in the determination of floral organ number. Acts to determine floral organ patterning by establishing floral organ primordia in specific numbers and positions. Plays a role in regulating stem cell fate by directly controlling AG expression. Binds to the 5'-AAGAAT-3' cis-acting element found in AG promoter. Might represent a target for a post-translational modification by GRXC7/ROXY1. Interacts with GRXC7/ROXY1. Interacts with BOP1 and BOP2. Expressed in the apical meristem, the floral meristem, each whorl of organ primordia, and in ovule primordia during wild-type flower development. Mutant plants have extra floral organs. The modal numbers of organs in mutant flowers are 5 sepals, 5 petals, 5 stamens, and 2 carpels in contrast with the tetramerous pattern of the wild type. Belongs to the bZIP family.