At the molecular level, flowering is repressed by the protein "Flowering Locus C" ("FLC"), which binds to and represses genes that promote flowering, thus blocking flowering. Winter annual ecotypes of Arabidopsis have an active copy of the gene "FRIGIDA" ("FRI"), which promotes "FLC" expression, thus repression of flowering. Prolonged exposure to cold (vernalization) induces expression of "VERNALIZATION INSENSTIVE3", which interacts with the "VERNALIZATION2" ("VRN2") polycomb-like complex to reduce "FLC" expression through chromatin remodeling. Levels of VRN2 protein increase during long-term cold exposure as a result of inhibition of VRN2 turnover via its N-degron. The events of histone deacetylation at Lysine 9 and 14 followed by methylation at Lys 9 and 27 is associated with the vernalization response. The epigenetic silencing of "FLC" by chromatin remodeling is also thought to involve the cold-induced expression of antisense "FLC COOLAIR" or "COLDAIR" transcripts. Vernalization is registered by the plant by the stable silencing of individual "FLC" loci. The removal of silent chromatin marks at "FLC" during embryogenesis prevents the inheritance of the vernalized state.