Arabidopsis FLC clade members form flowering-repressor complexes coordinating responses to endogenous and environmental cues

The developmental transition to flowering is timed by endogenous and environmental signals through multiple genetic pathways. In Arabidopsis, the MADS-domain protein FLOWERING LOCUS C is a potent flowering repressor. Here, we report that the FLOWERING LOCUS C clade member MADS AFFECTING FLOWERING3 acts redundantly with another clade member to directly repress expression of the florigen FLOWERING LOCUS T and inhibit flowering. FLOWERING LOCUS C clade members act in partial redundancy in floral repression and mediate flowering responses to temperature, in addition to their participation in the flowering-time regulation by vernalization and photoperiod. We show that FLOWERING LOCUS C, MADS AFFECTING FLOWERING3 and three other clade members can directly interact with each other and form nuclear complexes, and that FLOWERING LOCUS C-dependent floral repression requires other clade members. Our results collectively suggest that the FLOWERING LOCUS C clade members act as part of several MADS-domain complexes with partial redundancy, which integrate responses to endogenous and environmental cues to control flowering.