We are interested in understanding how regulatory circuits interact to control floral development. The four major floral parts—sepals, petals, stamens (the male organs), and carpels (the female organs)—arise sequentially at the floral meristem. They occupy successive whorls from the outside to the inside, respectively, of a flower. Several major regulatory genes have been identified and their roles in floral development extensively studied by several laboratories. Our current effort is centered on understanding how the regulatory gene SUPERMAN from Arabidopsis controls the development of stamens and carpels. SUPERMAN is essential for carpel development as well as for defining the spatial domain for stamen development. In wild type Arabidopsis, SUPERMAN mRNA accumulates in the region of the stamen primordia adjacent to the emerging carpel primordia. Mutant plants defective in the SUPERMAN gene either lack or produce defective carpels, and produce excess number of stamens which occupy their normal position in a flower as well as invade the position which should be occupied by the carpels. These together suggest that SUPERMAN-expressing stamen cells send signals to trigger carpel differentiation in the central domain of the floral meristem as well as to delimit the expression of stamen differentiation program in the central domain. The mechanism underlying the function of SUPERMAN is being investigated using a combination of molecular, biochemical, cell culture, and transgenic approaches.