Plants monitor many aspects of their fluctuating environments to help align their development with seasons. Molecular understanding of how noisy temperature cues are registered has emerged from dissection of vernalization in Arabidopsis, which involves a multiphase cold-dependent silencing of the floral repressor locus FLOWERING LOCUS C (FLC). Cold-induced transcriptional silencing precedes a low probability PRC2 epigenetic switching mechanism. The epigenetic switch requires the absence of warm temperatures as well as long-term cold exposure. However, the natural temperature inputs into the earlier transcriptional silencing phase are less well understood. Here, through investigation of Arabidopsis accessions in natural and climatically distinct field sites, we show that the first seasonal frost strongly induces expression of COOLAIR, the antisense transcripts at FLC. Chamber experiments delivering a constant mean temperature with different fluctuations showed the freezing induction of COOLAIR correlates with stronger repression of FLC mRNA. Identification of a mutant that ectopically activates COOLAIR revealed how COOLAIR up-regulation can directly reduce FLC expression. Consistent with this, transgenes designed to knockout COOLAIR perturbed the early phase of FLC silencing. However, all transgenes designed to remove COOLAIR resulted in increased production of novel convergent FLC antisense transcripts. Our study reveals how natural temperature fluctuations promote COOLAIR regulation of FLC, with the first autumn frost acting as a key indicator of autumn/winter arrival.

中文翻译：

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自然温度波动促进 FLC 的 COOLAIR 调节

植物监测其波动环境的许多方面，以帮助它们的发展与季节保持一致。对如何记录嘈杂的温度线索的分子理解来自拟南芥春化的解剖，这涉及花卉抑制基因座FLOWERING LOCUS C ( FLC )的多相冷依赖性沉默。冷诱导的转录沉默先于低概率的 PRC2 表观遗传转换机制。表观遗传开关需要没有温暖的温度以及长期的冷暴露。然而，对早期转录沉默阶段的自然温度输入不太了解。在这里，通过对拟南芥的调查在自然和气候不同的田地中加入，我们表明第一次季节性霜冻强烈诱导FLC的反义转录物COOLAIR的表达。提供具有不同波动的恒定平均温度的腔室实验表明，COOLAIR的冷冻诱导与FLC mRNA的更强抑制相关。异位激活COOLAIR的突变体的鉴定揭示了COOLAIR上调如何直接降低FLC表达。与此一致，旨在敲除COOLAIR的转基因扰乱了FLC的早期阶段沉默。然而，所有旨在去除COOLAIR的转基因都导致新的会聚FLC反义转录本的产量增加。我们的研究揭示了自然温度波动如何促进FLC的COOLAIR调节，第一次秋季霜冻是秋/冬到来的关键指标。