THE FLORAL HOMEOTIC GENE, APETALA1 (AP1) NEGATIVELY REGULATES PETAL-FATE IN ARABIDOPSIS THALIANA WITH CO-REPRESSOR, TOPLESS (TPL)

Proper development of an organism relies on a precise pattern of fate-specifying gene regulation. In the angiosperm plant, Arabidopsis thaliana, floral homeotic genes like APETALA1 (AP1) are determinants of this pattern to give rise to proper specification. This study demonstrated that mutating the EAR motif of AP1 caused misexpression of petal-specifying genes in sepals. The EAR motif of AP1 was shown to recruit the corepressor, TOPLESS (TPL) to form a complex that repressed petal genes in the outer whorl. Misexpression in the outer whorl organs implicates the EAR motif of AP1 as determining spatial restriction of B-class gene expression. This provides new information to characterize the role of AP1 and its molecular mechanism as a repressor, as well as its function in specifying sepal identity.