Melatonin mediates the stabilization of DELLA proteins to repress the floral transition in Arabidopsis

Abstract Precise floral transition from vegetative growth phase to reproductive growth phase is very important in plant life cycle. In flowering genetic pathways, DELLA proteins are master transcriptional regulators of gibberelic acid ( GA ) pathway, and FLOWERING LOCUS C ( FLC ) is a core repressor of vernalization pathway as well as downstream of DELLA s. As a crucial messenger in plants, the possible involvement of melatonin ( N ‐acetyl‐5‐methoxytryptamine) in flowering and underlying molecular mechanism are unknown in A rabidopsis . In this study, we found that exogenous melatonin treatment delayed floral transition in A rabidopsis . Exogenous melatonin treatment conferred protein stabilizations of DELLA s [ REPRESSOR of ga1‐3 ( RGA ) and RGA ‐ LIKE 3 ( RGL 3)], without regulating the transcripts of DELLA s and endogenous GA level. Notably, exogenous melatonin delayed plant flowering and DELLA ‐activated transcripts of FLC were alleviated in della mutants, and those were exacerbated in DELLA overexpressing plants. Taken together, this study provides direct link between melatonin and floral transition, and indicates the novel involvement of DELLA s‐activated FLC in melatonin‐mediated flowering in A rabidopsis .