Abstract：
The circadian clock entrained by environmental light-dark cycles enables plants to fine-tune diurnal growth and developmental responses. Here, we show that physical interactions among evening clock components, including PSEUDO-RESPONSE REGULATOR 5 (PRR5), TIMING OF CAB EXPRESSION 1 (TOC1), and the Evening Complex (EC) component EARLY FLOWERING 3 (ELF3), define a diurnal repressive chromatin structure specifically at the PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) locus in Arabidopsis. These three clock components act interdependently as well as independently to repress nighttime hypocotyl elongation, as hypocotyl elongation rate dramatically increased specifically at nighttime in the prr5-1 toc1-21 elf3-1 mutant, concomitantly with a substantial increase in PIF4 expression. Transcriptional repression of PIF4 by ELF3, PRR5, and TOC1 is mediated by the SWI2/SNF2-RELATED (SWR1) chromatin remodeling complex, which incorporates histone H2A.Z at the PIF4 locus, facilitating robust epigenetic suppression of PIF4 during the evening. Overall, these findings demonstrate that the PRR-EC-SWR1 complex represses hypocotyl elongation at night through a distinctive chromatin domain covering PIF4 chromatin.
摘要：
环境明暗周期夹带的昼夜节律时钟使植物能够微调昼夜生长和发育反应。这里,我们展示了晚间时钟组件之间的物理相互作用，包括伪响应规则5(PRR5)，CAB表达式1（TOC1）的时间，和晚装复合物（EC）成分早花3（ELF3），在拟南芥中的植物铬相互作用因子4（PIF4）基因座上定义昼夜抑制染色质结构。这三个时钟成分相互独立地抑制夜间下胚轴伸长，由于prr5-1toc1-21elf3-1突变体的下胚轴伸长率在夜间特别显着增加，同时PIF4表达大幅增加。ELF3，PRR5和TOC1对PIF4的转录抑制是由SWI2/SNF2相关（SWR1）染色质重塑复合物介导的，其中包含组蛋白H2A。Z在PIF4位点，促进晚上对PIF4的强烈表观遗传抑制。总的来说,这些发现表明，PRR-EC-SWR1复合物在夜间通过覆盖PIF4染色质的独特染色质结构域抑制下胚轴伸长。
