Genetic and molecular characterization of the regulation of chloroplast protein import in Arabidopsis thaliana

拟南芥叶绿体蛋白输入调控的遗传和分子特征

• 批准号: 2107976
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2107976
• 关键词: Genetic; molecular; characterization; regulation; chloroplast

Plastids are a group of specialised organelles widely distributed through plants and algae. The most prototypical member of the group is undoubtedly the chloroplast, which is the site of photosynthesis and many other essential biosynthetic processes. Plastids derive from ancestral cyanobacteria through an endosymbiotic event, and as a result retain a eubacterial-type genome. Within the course of evolution, over 90% of the ancestral protein-coding genes have been transferred into the nuclear genome. The encoded plastid-bound proteins must therefore be transferred back into plastids after synthesis, and this is facilitated by a dedicated import apparatus (the TOC/TIC complexes). Over last few years a proteolytic system called the Ubiquitin-Proteasome System (UPS) has been recognized to target TOC proteins for degradation by tagging with ubiquitin. By regulating the import pathway, the plastid proteome can be altered to assist the acclimation under particular environment or developmental stage. Recently, a chloroplast-associated protein degradation (CHLORAD) system has been identified. In CHLORAD, SP1 (SUPPRESSOR OF ppi1 LOCUS 1) acts as the E3 ligase, SP2 (SUPPRESSOR OF ppi1 LOCUS 2) functions as an exit channel, and the ATPase Cdc48 provides the motor force for protein extraction. One important question is: how is the cytosolic Cdc48 tethered to chloroplasts? PUX10, which belongs to a UBX-domain-containing protein family functioning as Cdc48 cofactors, was identified to interact with Cdc48, SP1, SP2 and TOC proteins on the chloroplast membrane. I will carry on dissecting its functional link with CHLORAD by analysing its topology, the roles of its two specific domains (UBX and UBA), and its physiological significance in plastid biogenesis. In parallel, a larger scale genetic screen for suppressor mutations of ppi1 had identified a new suppressor of ppi1 locus called sp3. Preliminary characterization suggests that SP3 associates with a CUL4-based E3 ligase complex acting as a substrate receptor. To build on this, I aim to understand: what the substrates of SP3 are; the interaction between SP3 and TOC components; and what physiological roles SP3 has in chloroplast biogenesis and stress tolerance.The proposed project falls into the remit of cross-research council and BBSRC priority areas. As plastids contribute massively to crop productivity and quality, the knowledge gained from this project will facilitate our capability to sustainably enhance agriculture production and battle the issues relating to food, nutrition and health. Furthermore, understanding the predicted role of TOC degradation in responding to abiotic stress may contribute to coping with global food security and living with environment change.

质体是一组专门通过植物和藻类分布的专门细胞器。该组中最原型的成员无疑是叶绿体，叶绿体是光合作用和许多其他必要的生物合成过程的位置。通过内共生事件源自祖先蓝细菌的质体，因此保留了花生型基因组。在进化过程中，超过90％的祖先蛋白质编码基因已转移到核基因组中。因此，必须将编码的质体结合蛋白转移到合成后的质体中，这是由专用的导入设备（TOC/TIC复合物）促进的。在过去的几年中，一种称为泛素 - 蛋白酶体系统（UPS）的蛋白水解系统已被识别为通过用泛素标记来降解靶向TOC蛋白。通过调节进口途径，可以更改质体蛋白质组以在特定环境或发育阶段协助适应。最近，已经鉴定出叶绿体相关的蛋白质降解（氯拉德）系统。在氯拉德中，SP1（PPI1基因座的抑制剂1）充当E3连接酶，SP2（PPI1基因座2的抑制剂）用作出口通道，而ATPase CDC48为蛋白质提取的摩托力提供了摩托力。一个重要的问题是：胞质CDC48如何将叶绿体束缚在叶绿体上？属于含Cdc48辅因子的含UBX域的蛋白质家族的PUX10与叶绿体膜上的CDC48，SP1，SP2和TOC蛋白相互作用。我将通过分析其拓扑结构，其两个特定领域（UBX和UBA）的作用以及在质体生物发生中的生理意义来继续解剖其与氯拉德的功能联系。同时，PPI1抑制突变的较大规模的遗传筛选已经确定了一种称为SP3的PPI1基因座的新抑制剂。初步表征表明，SP3与基于CUL4的E3连接酶复合物相关联，该配合酶是底物受体。为了建立在此基础上，我的目标是了解：SP3的底物是什么？ SP3和TOC组件之间的相互作用； SP3在叶绿体生物发生和胁迫耐受性中具有什么生理作用。拟议的项目属于跨研究委员会和BBSRC优先领域的职责。随着质体为作物生产率和质量做出了极大的贡献，该项目所获得的知识将有助于我们可持续增强农业生产并与与食品，营养和健康有关的问题作斗争。此外，了解TOC退化在应对非生物压力中的预测作用可能有助于应对全球粮食安全和环境变化。