Function of NOT9B and the CCR4-NOT complex in phytochrome A dependent light signalling

NOT9B 和 CCR4-NOT 复合物在光敏色素 A 依赖性光信号传导中的功能

• 批准号: 453030721
• 负责人: Professor Dr. Andreas Hiltbrunner
• 金额: --
• 依托单位: Institut für Biologie II
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/453030721?language=en
• 关键词: Function; NOT9B; CCR4; complex; phytochrome

Phytochromes (phys) are red/far-red photoreceptors in plants that play a critical role in adaptation of growth and development to changes in the environment. In most plants, phytochromes are represented by small gene families. PhyA and phyB are the main phytochromes in seed plants involved in regulation of growth and development, including seed germination, de-etiolation, induction of flowering, and responses to canopy shade. PhyB is the primary receptor for red light, while phyA is required for sensing far-red light and light of very low intensity.When activated by light, phytochromes translocate from the cytosol into the nucleus and regulate gene expression. There are two well-investigated signalling pathways downstream of phytochromes that inhibit light responses. The PHYTOCHROME INTERACTING FACTORs (PIFs), a subgroup of the bHLH transcription factors, negatively regulate light signalling. In parallel, the CONSTITUTIVELY PHOTOMORPHOGENIC 1/SUPPRESSOR OF PHYA-105 (COP1/SPA) E3 ubiquitin ligase complex targets positive regulators of light signalling for degradation by the proteasome. Light-activated phytochromes inhibit both PIFs and COP1/SPA and thereby induce responses to light.To identify novel signalling pathways downstream of phytochromes that are potentially independent of PIFs and COP1/SPA, we performed a yeast two hybrid screen for proteins that interact with light-activated phyA. In this screen we found NOT9B, a component of the CCR4-NOT complex. The CCR4-NOT complex is comparably well characterised in yeast, Drosophila, and mammals and plays a role in different aspects of RNA metabolism and regulation of gene expression. However, much less is known about the function of CCR4-NOT in plants. We show that NOT9B is a negative regulator of phyA-mediated light responses and we propose that NOT9B associated with CCR4-NOT represses light signalling. Preliminary data show that light-activated phyA binds NOT9B and thereby displaces NOT9B from CCR4-NOT to relieve repression of phyA-dependent light signalling. In the proposed project we want to further investigate the molecular mechanisms underlying regulation of CCR4-NOT by phyA and understand how CCR4-NOT modulates expression of light-controlled genes.

光敏色素(Phys)是植物中的红色/远红光感受器，在植物生长发育适应环境变化中起着至关重要的作用。在大多数植物中，光敏色素由小基因家族代表。PhyA和PhyB是种子植物中的主要光敏色素，参与调节种子的生长发育，包括种子萌发、脱黄化、开花诱导和对树冠遮荫的反应。PhyB是红光的主要受体，而PhyA是感知远红光和极弱光所必需的。当被光激活时，光敏色素从细胞质转移到细胞核，调节基因的表达。在光敏色素下游有两条经过充分研究的信号通路，它们抑制光反应。光敏色素相互作用因子(PIF)是bHLH转录因子的一个亚类，负向调节光信号。同时，组成光形态发生蛋白1/PhyA-105(COP1/SPA)E3泛素连接酶抑制子的复合体针对光信号的正调控因子，通过蛋白酶体进行降解。光激活的光敏色素抑制PIF和COP1/SPA，从而诱导对光的反应。为了确定光敏色素下游可能独立于PIF和COP1/SPA的新的信号通路，我们进行了酵母双杂交筛选与光激活的PhyA相互作用的蛋白质。在这个屏幕上，我们发现了NOT9B，这是CCR4的一个组件-并不复杂。CCR4-NOT复合体在酵母、果蝇和哺乳动物中具有较好的特性，并在RNA新陈代谢和基因表达调控的不同方面发挥作用。然而，人们对CCR4的功能知之甚少--更不用说在植物中了。我们发现NOT9B是PhyA介导的光反应的负调节因子，我们认为与CCR4-相关的NOT9B不抑制光信号。初步数据显示，光激活的PhyA与NOT9B结合，从而取代了CCR4中的NOT9B--而不是解除对依赖于PhyA的光信号的抑制。在拟议的项目中，我们希望进一步研究CCR4-而不是由PhyA调控的分子机制，并了解CCR4-Not如何调控光控制基因的表达。