(a) Prior to cold exposure, the FLC locus is expressed and enriched in H3K4me2, H3K4me3, H3K36me3 and histone acetylation. During the first weeks of cold exposure, COOLAIR transcripts are transiently expressed at a high level causing the down-regulation of FLC transcription. The binding of VAL1 (and possibly its homologue VAL2) at the nucleation region and their interactions with the histone deacetylase HDA19, the ASAP complex, involved in transcriptional regulation, and the PRC1, link the down-regulation of transcription to Polycomb silencing. VIN3 is induced by cold. (b) The ASAP complex associates with the PRC2 accessory proteins VIN3 and VRN5 and with the PRC2-SWN complex at the nucleation region establishing the metastably silenced state at FLC. This state is characterised by FLC not being transcribed and accumulation of H3K27me3 at the nucleation region. (c) Upon return to warm temperatures, H3K27me3 spreads across the locus, a process requiring the formation and spreading of the PRC2–CLF complex, LHP1 and the incorporation of the histone variant H3.1. This last phase establishes a long-term epigenetically silenced state that is maintained across multiple cell divisions until the state is reset during reproductive development.