Abstract

Long noncoding RNAs (lncRNAs) play important roles in chromatin regulation in higher eukaryotes. Studies analysing how lncRNAs influence Polycomb silencing suggested they specifically bind and recruit Polycomb Repressive Complex 2 (PRC2) to defined targets. However, the promiscuous binding of PRC2 to RNA has raised questions as to the mechanism by which lncRNA contributes to Polycomb silencing. We investigate the function of a set of cold-induced antisense transcripts in the Polycomb-dependent epigenetic silencing of a floral repressor gene in Arabidopsis. Through analysis of a transgene, in which antisense transcripts are no longer cold-induced, we show that these antisense transcripts are required for coordinated switching of opposing chromatin states. This mechanism links transcriptional shutdown by cold to long-term epigenetic silencing.