Fig. 8. Genetic control of Antirrhinum floral meristem identity and prophyll initiation by INCO and SQUA. Arrows indicate promoting functions and bars show negative effects; neither of these is meant to be direct. Proteins are shown as ovals. For simplicity, we neglect the option that INCO and SQUA are likely to interact with other MADS-domain proteins. The control of prophyll development by SQUA and INCO is highlighted by grey on the left. The arrows merging in the FLO control show convergence of processes promoting flower formation. Green shows potential activation by preference for heterodimerisation of INCO with SQUA. Red (and thin lines) suggests a possible mechanism that can counteract the negative influence of the INCO homodimer on flowering in the wild type. Reinforced heterodimerisation of INCO with SQUA supersedes repression of flowering by INCO. This negative influence, therefore, is relevant only in the squa mutant background.