Nat. Genet. http://doi.org/bs6v (2016)

Reproduction in many plants requires vernalization, which accelerates flowering by prolonged exposure to cold temperatures. The repression of FLOWERING LOCUS C (FLC) is essential to the vernalization mechanism. Recently, Yuehui He's group from the Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai, China, reported the identification of a cold memory DNA element and cognate reader proteins, which are essential for FLC silencing before and during vernalization.

Yuan et al. identified two Sph/RY DNA motifs in the nucleation region of FLC that are fundamental for FLC silencing, and investigated their importance in maintaining the silencing after cold exposure. A 47-bp element bearing Sph/RY motifs was designated the cold memory element (CME). Two trans-acting factors, VAL1 and VAL2, were characterized as FLC repressors. The VAL proteins read the CME as well as histone modification H3K27me3, marking a repressive state of FLC. Further, chromatin immunoprecipitation and quantitative polymerase chain reaction results suggest that the CME–VAL interaction mediates the induction and maintenance of FLC silencing during vernalization.

This study demonstrates an important epigenetic mechanism for how plants control when to flower in response to prolonged cold exposure.