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

光是控制植物生长发育的最重要的环境因子之一。植物拥有过多的蛋白质，参与光感知和光信号转导，以感知和适应环境中的光条件。此外，参与光信号传递的许多因素也在不同信号通路之间的串扰中发挥作用，以整合内部和外部刺激。植物中的光信号始于光感受器对光质量和数量的感知。其中，光敏色素(Phys)主要负责红光和远红光依赖反应。利用冷调节基因27(COR27)及其同源基因COR28，我们已经鉴定了两个直接与PhyA和PhyB相互作用的蛋白质，它们在光依赖的下胚轴生长、开花诱导、昼夜节律调节和耐寒性方面发挥作用。因此，它们可能参与光和温度信号的整合。Co27-2 cor28-2双突变体对红光高度敏感，且在长日照条件下开花延迟，而高表达COR27或COR28的幼苗对红光不敏感。此外，我们已经证明COR27和COR28是组成光形态发生蛋白1/PhyA-105(COP1/SPA)E3泛素连接酶抑制物复合体的靶标，并且可能通过光感受器依赖的COP1/SPA失活来稳定光。最近，COR27和COR28被发现与光信号转导中的中心转录因子--细长的下胚轴5(HY5)结合，从而抑制HY5的转录活性。然而，RNAseq数据和表型分析表明，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的主要作用途径仍然难以捉摸。在拟议的项目中，我们计划调查COR27和COR28与PhyA和PhyB的直接关联，并研究我们最近通过AP-MS确定的潜在的COR27/COR28相互作用伙伴，这表明COR27和COR28在染色质重塑中发挥了作用。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，并希望使用CHIP-SEQ方法识别COR27和COR28的直接靶基因。总体而言，该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子如何共同作用来控制光调控基因的表达。

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.