專題：Nature報導
「春化」是植物繼寒冬之後在春天獲得根據環境提示來開花的能力的過程，是植物的一個關鍵適應性特徵，對農業生產有較大影響。擬南芥開花抑制因子FLC在由Polycomb調控蛋白調節的一個過程中被「春化」關閉。
現在，FLC的非編碼反義RNA轉錄體被發現存在於冷處理的種子中，並對溫度變化有響應，這說明它們在低溫感應和FLC沉默中有可能扮演一個角兒。這種類型的反義轉錄事件（源自基因的3′端）也許是調控相應「正義」轉錄的一個普遍機制。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 462, 799-802 (10 December 2009) | doi:10.1038/nature08618
Cold-induced silencing by long antisense transcripts of an Arabidopsis Polycomb target
Szymon Swiezewski1, Fuquan Liu1, Andreas Magusin1 & Caroline Dean1
1 John Innes Centre, Colney, Norwich, NR4 7UH, UK
Correspondence to: Caroline Dean1 Correspondence and requests for materials should be addressed to C.D.
Transcription in eukaryotic genomes generates an extensive array of non-protein-coding RNA, the functional significance of which is mostly unknown1. We are investigating the link between non-coding RNA and chromatin regulation through analysis of FLC?—?a regulator of flowering time in Arabidopsis and a target of several chromatin pathways. Here we use an unbiased strategy to characterize non-coding transcripts of FLC and show that sense/antisense transcript levels correlate in a range of mutants and treatments, but change independently in cold-treated plants. Prolonged cold epigenetically silences FLC in a Polycomb-mediated process called vernalization2. Our data indicate that upregulation of long non-coding antisense transcripts covering the entire FLC locus may be part of the cold-sensing mechanism. Induction of these antisense transcripts occurs earlier than, and is independent of, other vernalization markers3 and coincides with a reduction in sense transcription. We show that addition of the FLC antisense promoter sequences to a reporter gene is sufficient to confer cold-induced silencing of the reporter. Our data indicate that cold-induced FLC antisense transcripts have an early role in the epigenetic silencing of FLC, acting to silence FLC transcription transiently. Recruitment of the Polycomb machinery then confers the epigenetic memory. Antisense transcription events originating from 3′ ends of genes might be a general mechanism to regulate the corresponding sense transcription in a condition/stage-dependent manner.