The molecular basis of vernalization: The central role of FLOWERING LOCUS C (FLC)

In Arabidopsis, the MADS-box protein encoded by FLOWERING LOCUS C (FLC) is a repressor of flowering. Vernalization, which promotes flowering in the la te-flowering ecotypes and many late-flowering mutants, decreases the level of FLC transcript and protein in the plant. This vernalization-induced redu ction in FLC transcript levels is mitotically stable and occurs in all tiss ues. FLC activity is restored in each generation, as is the requirement of a tow-temperature exposure for the promotion of flowering. The level of FLC determines the extent of the vernalization response in the promotion of fl owering, and there is a quantitative relationship between the duration of c old treatment and the extent of down-regulation of FLC activity. We conclud e that FLC is the central regulator of the induction of flowering by vernal ization. Other vernalization-responsive late-flowering mutants, which are d isrupted in genes that encode regulators of FLC, are late-flowering as a co nsequence of their elevated levels of FLC.