Cold-induced silencing by long antisense transcripts of an Arabidopsis Polycomb target

摘要

Transcription in eukaryotic genomes generates an extensive array of non-protein-coding RNA, the functional significance of which is mostly unknown. 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/anti-sense 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 vernalization. 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 markers 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.%“春化”是植物继寒冬之后在春天获得根据环rn境提示来开花的能力的过程，是植物的一个关rn键适应性特征，对农业生产有较大影响。拟南rn芥开花抑制因子FLC在由Polycomb调控蛋白调rn节的一个过程中被“春化”关闭。现在，FLC的rn非编码反义RNA转录体被发现存在于冷处理的rn种子中，并对温度变化有响应，这说明它们在rn低温感应和FLC沉默中有可能扮演一个角儿。rn这种类型的反义转录事件(源自基因的3’端)也rn许是调控相应“正义”转录的一个普遍机制。