VASCULAR PLANT ONE-ZINC FINGER1 (VOZ1) and VOZ2 Interact with CONSTANS and Promote Photoperiodic Flowering Transition

In plants, endogenous and environmental signals such as light control the timing of the transition to flowering. Two phytochrome B-interacting transcription factors, VASCULAR PLANT ONE-ZINC FINGER1 (VOZ1) and VOZ2, redundantly promote flowering in Arabidopsis (). In the mutant, the expression of () was up-regulated and that of () was down-regulated, which was proposed to be the cause of late flowering in However, the detailed mechanism by which the genes promote flowering is not well understood. Here, we show that neither the reduced expression nor the late-flowering phenotype of is suppressed in the triple mutant. Genetic interaction experiments between and () mutants reveal that the and work in the same genetic pathway. Using in vitro pull-down, electrophoretic mobility shift, and bimolecular fluorescence complementation assays, we show that VOZ1 and VOZ2 interact with CO. The ::: plants show suppression of the early-flowering phenotype induced by overexpression, suggesting that CO requires VOZ for the induction of flowering. Determination of the VOZ consensus-binding site followed by genome-wide sequence analysis failed to identify any VOZ-binding sites near known flowering time genes. Together, these results indicate that the genes regulate flowering primarily through the photoperiod pathway, independent of , and suggest that VOZs modulate CO function to promote flowering.