SUPERMAN prevents class B gene expression and promotes stem cell termination in the fourth whorl of Arabidopsis thaliana flowers

Significance The Arabidopsis thaliana flower is a complex structure that consists of discrete floral organs (sepals, petals, stamens, and carpels) that are separated by regions lacking organ growth called boundaries. The SUPERMAN ( SUP ) gene functions to define the boundary between the male organs (stamens) and female organs (carpels) in the flower. Previous work on boundary formation in plants has focused on growth repression, rather than on identity separation. Using live confocal imaging, we demonstrate that SUP functions by keeping the male and female developmental programs spatially and temporally separate, which is critical for the fertility of the flower. In addition, we show a second role of SUP in the timely termination of floral stem cells.