Chromatin modification and reshaping have an instrumental role in regulating gene expression in eukaryotes. "Vernalization," or the "winter memory" of plants, is a paradigm of epigenetic regulation of environmental signal responses mediated by chromatin modification in plants. In the vernalization process of the model plant Arabidopsis thaliana, a long-term and consistent low temperature (cold winter) silences the expression of the flowering transition inhibitory gene FLC. With the advent of spring and increasing temperatures, this silent state is steadily maintained, endowing the plant with the "epigenetic memory of winter cold". This enables Arabidopsis to flower and produce seeds in the spring. Prior to cold treatment, the chromatin at the FLC locus is highly activated, enriched with transcriptionally active modifications such as trimethylation of lysine 4 (H3K4me3) and lysine 36 (H3K36me3) on histone H3. Long-term winter cold induces the formation of a Polycomb domain at this locus enriched with transcriptionally repressive H3K27me3 modification. However, the regulatory mechanism of the transition from the activated chromatin state to the silenced state remains unclear.

On March 14, 2023, the research group led by Yuehui He from the Peking University Institute of Advanced Agricultural Sciences and the Peking-Tsinghua Center for Life Sciences published a research paper in Molecular Cell, titled "A pair of readers of bivalent chromatin mediate formation of Polycomb-based 'memory of cold' in plants". The paper reports the molecular and epigenetic mechanisms underlying the "winter memory" formation in Arabidopsis driven by two plant-specific bivalent histone reader proteins that recognize the specific regulatory regions of the bivalent chromatin at the FLC locus.