Figure 1.

Model of interaction of CYC, DIV, RAD, and DRIF proteins in Antirrhinum majus (modified from Raimundo et al., 2013). The DIV and DRIF proteins are expressed both in the dorsal and ventral parts of the flower. In the dorsal domain, the CYC protein interacts with the promoter and intron of the RAD gene, activating its expression. The RAD protein binds to DRIF and prevents the formation of the DIV/DRIF complex, thus inhibiting ventralization. In the ventral domain, the absence of RAD permits the formation of the DIV/DRIF complex that controls downstream genes involved in the ventralization.