Regulation of floral patterning by flowering time genes.

Floral patterning in Arabidopsis requires activation of floral homeotic genes by the floral meristem identity gene, LEAFY (LFY). Here we show that precise activation of expression of class B and C homeotic genes in floral meristems is regulated by three flowering time genes, SHORT VEGETATIVE PHASE (SVP), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), and AGAMOUS-LIKE 24 (AGL24), through direct control of a LFY coregulator, SEPALLATA3 (SEP3). Orchestrated repression of SEP3 by SVP, AGL24, and SOC1 is mediated by recruiting two interacting chromatin regulators, TERMINAL FLOWER 2/LIKE HETEROCHROMATIN PROTEIN 1 and SAP18, a member of SIN3 histone deacetylase complex. Our finding of coordinated regulation of SEP3 by flowering time genes reveals a hitherto unknown genetic pathway that prevents premature differentiation of floral meristems and determines the appropriate timing of floral organ patterning.