Breuil-Broyer et al. show that SUPERMAN is a flower developmental canalization and robustness factor. First, partial dissociation of sexual boundary and flower meristem termination control in the sup allelic series (superman, superwoman, and supersex) has facilitated characterization of the partial independence of SUP-mediated WUS repression on the AG and CLV pathways.
Setting a precise sexual boundary may have facilitated refinement of flower development, including co-option of the meristem patterning system for gynoecium development. Secondly, novel, late SUP functions in carpel patterning show that SUP operates in conjunction with KNUCKLES, a SUP-related placenta boundary gene. Lastly, combined understanding of both early and late SUP functions supports an evo-devo scenario reconciling the Mostly Male and Out of Male/Out of Female theories, and reveals the central role of class B/C homeotic gene balance modulation in the evolutionary change from uni- to bisexuality.