Investigation of a potential function of COR27 and COR28 in phytochrome-mediated chromatin remodelling

光是控制植物生长发育几乎所有方面的最重要环境因子之一。植物拥有大量参与光感知和光信号转导的蛋白质，以感知和适应其环境中的光条件。此外，许多参与光信号传导的因子也在不同信号通路之间起串扰作用，整合内外刺激。植物的光信号开始于光感受器对光的质量和数量的感知。其中，光敏色素（phyys）主要负责红光和远红光依赖反应。利用冷调控基因27 （COR27）及其同系物COR28，我们发现了两种与phyA和phyB直接相互作用的蛋白，并在依赖光的下胚轴生长、诱导开花、调节昼夜节律和抗冻性中发挥作用。因此，它们可能参与光和温度信号的整合。COR27 -2 - COR28 -2双突变体以phyb依赖的方式对红光敏感，在长日照条件下开花较晚，而过表达COR27或COR28的幼苗对红光不敏感。此外，我们已经证明COR27和COR28是phyA-105 (COP1/SPA) E3泛素连接酶复合物的组成型光形态形成1/抑制因子的靶标，并且可能通过光感受器依赖的COP1/SPA失活而被光稳定。最近，研究显示COR27和COR28与参与光信号传导的中心转录因子伸长下cotyl 5 （HY5）结合，从而抑制HY5的转录活性。然而，RNAseq数据和表型分析显示，COR27和COR28对幼苗发育的影响在很大程度上与HY5无关。因此，COR27和COR28作用的主要途径尚不明确。在拟议的项目中，我们计划调查COR27和COR28与phyA和phyB直接关联的相关性，并检查我们最近通过AP-MS确定的潜在COR27/COR28相互作用伙伴，并指出COR27和COR28在染色质重塑中的作用。因此，我们的目标是分析COR27和COR28是否影响染色质密度和组蛋白修饰，我们希望使用ChIP-seq方法确定COR27和COR28的直接靶基因。总的来说，拟议项目的目的是了解光敏色素，COR27和COR28，以及参与调节染色质密度和组蛋白修饰的因素如何共同作用，以控制光调节基因的表达。

Light is one of the most important environmental factors controlling almost all aspect of plant growth and development. Plants possess a plethora of proteins involved in light perception and light signal transduction to sense and adapt to the light conditions in their environment. In addition, many factors involved in light signalling also have a function in crosstalk between different signalling pathways to integrate internal and external stimuli. Light signalling in plants begins with the perception of light quality and quantity by photoreceptors. Among them, phytochromes (phys) are mainly responsible for red- and far- red light-dependent responses. With COLD REGULATED GENE 27 (COR27), and its homologue COR28, we have identified two proteins that interact directly with phyA and phyB and play a role in light-dependent hypocotyl growth, induction of flowering, regulation of circadian rhythms, and freezing tolerance. Thus, they are likely involved in the integration of light and temperature signals. The cor27-2 cor28-2 double mutant is hypersensitive to red light in a phyB-dependent manner and flowers late under long-day conditions, while seedlings overexpressing COR27 or COR28 are hyposensitive to red light. Furthermore, we have shown that COR27 and COR28 are targets of the CONSTITUTIVELY PHOTOMORPHOGENIC 1/SUPPRESSOR OF phyA-105 (COP1/SPA) E3 ubiquitin ligase complex and stabilised by light, probably through photoreceptor-dependent inactivation of COP1/SPA. Recently, COR27 and COR28 were shown to bind to ELONGATED HYPOCOTYL 5 (HY5), a central transcription factor involved in light signalling, thereby repressing the transcriptional activity of HY5. However, RNAseq data and phenotypic analysis revealed that the effect of COR27 and COR28 on seedling development is largely independent of HY5. Therefore, the main pathways of COR27 and COR28 action remain elusive. In the proposed project, we plan to investigate the relevance of the direct association of COR27 and COR28 with phyA and phyB, and examine potential COR27/COR28 interaction partners that we recently identified by AP-MS and that point to a role of COR27 and COR28 in chromatin remodelling. Consequently, we aim to analyse whether COR27 and COR28 affect chromatin density and histone modifications, and we want to identify direct target genes of COR27 and COR28 using a ChIP-seq approach. Overall, the aim of the proposed project is to understand how phytochromes, COR27 and COR28, and factors involved in regulation of chromatin density and histone modifications act together to control light-regulated gene expression.