Vernalization and epigenetics: how plants remember winter.

One of the remarkable aspects of the promotion of flowering by vernalization is that plants have evolved the ability to measure a complete winter season of cold and to 'remember' this prior cold exposure in the spring. Recent work in Arabidopsis demonstrates the molecular basis of this memory of winter: vernalization causes changes in the chromatin structure of a flowering repressor gene, FLOWERING LOCUS C (FLC), that switch this gene into a repressed state that is mitotically stable. A key component of the vernalization pathway, VERNALIZATION INSENSITIVE3 (VIN3), which is a PHD-domain-containing protein, is induced only after a prolonged period of cold. VIN3 is involved in initiating the modification of FLC chromatin structure. The stable silencing of FLC also requires the DNA-binding protein VERNALIZATION1 (VRN1) and the polycomb-group protein VRN2.