Characterization of short vegetative phase (SVP)

Abstract

Floral transition is one of the most drastic changes occurring during Arabidopsis life cycle. Genetic analysis of flowering time mutants has led to a model describing four integrated flowering time pathways. Vernalization and photoperiod pathways mediate the response to environmental cues, while autonomous and gibberellin (GA) pathways mediate the internal signals. SHORT VEGETATIVE PHASE (SVP) is a MADS-box transcription factor acting as a floral repressor in flowering. In this study, we localized SVP in autonomous and GA pathways, and identified SOC1 and FT as its direct target genes in the control of flowering time. Notably, SVP protein associates with the promoter regions of SOC1 and FT where another potent repressor, FLOWERING LOCUS C (FLC), binds. We further show that the SVP protein consistently interacts with FLC in whole seedlings during vegetative growth, and their function in regulating flowering is mutually dependent. Our results demonstrate that SVP is a central flowering repressor, and that its interaction with FLC governs the expression of floral pathway integrators in response to developmental and environmental signals, thus determining the timing of floral transition.