MYC3 DETERMINES FLOWERING UNDER SHORT DAYS IN ARABIDOPSIS THALIANA

Abstract

As a facultative long days (LDs) plant, Arabidopsis flowers late under non-inductive short days (SDs) conditions. Although the gibberellin acid (GA) signaling pathway has been suggested to play a major role in regulating flowering under SDs, the detailed molecular mechanisms are by now largely unknown. Here we demonstrate that MYC3 is a key floral repressor that determines flowering under SDs, but not under LDs. We further show the evidence that MYC3 constitutively suppresses flowering through directly repressing FT. Meanwhile, physiological studies suggest that myc3 is GA-hyposensitive, consistent with genetic analysis showing that myc3 can rescue the non-flowering phenotype of the GA-deficient ga1 mutant under SDs. Besides, MYC3 protein abundance is regulated by the GA pathway in a DELLA-dependent manner. Together, our findings reveal a hitherto unknown major flowering pathway that determines Arabidopsis flowering through repressing FT downstream of GA signaling under SDs.