Probable transcriptional regulator considered as cadastral protein that acts indirectly to prevent the B class homeotic proteins APETALA3 and perhaps PISTILLATA from acting in the gynoecial whorl. Principal function is to balance cell proliferation in the third and fourth whorls of developing flowers thereby maintaining the boundary between stamens and carpels. May fulfill this role by repressing genes implicated in cell division. Plays equally a role in the determinacy of the floral meristem. Is also required for normal ovule development. Expressed early in the third whorl, and later becomes localized at the boundary between the stamen and carpel whorls. Also detected in developing ovule primordia. Repressed by KRYPTONITE/SUVH4, member of the histone H3-K9 methyltransferase family that contributes with other factors to the CpNpG methylation of the SUP gene resulting in its silencing. The alternative epigenetic states of the SUPERMAN locus have been called Clark Kent alleles. Positively regulated at an early stage of development by LEAFY and by B class homeotic proteins APETALA3 and PISTILLATA. Later expression is maintained by both the B class homeotic proteins and the C class homeotic protein AGAMOUS. These two steps of regulation require the intervention of additional factors. Contains two overlapping leucine-zipper-like motifs at the C-terminal region, which might serve as a site for protein-protein interaction. In this domain, a slightly degenerated ERF-associated amphiphilic repression (EAR) motif seems to be involved in the activity of transcriptional repression. Mutations in SUP cause the ectopic expression of APETALA3 leading to the development of extra stamens at the expense of the central carpels of the flower.