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.

质体是广泛分布于植物和藻类中的一类特殊细胞器。毫无疑问，这一组中最典型的成员是叶绿体，它是光合作用和许多其他重要生物合成过程的场所。质体通过内共生事件从祖先蓝藻中获得，因此保留了真细菌型基因组。在进化过程中，超过90%的祖先蛋白质编码基因已经转移到核基因组中。因此，编码的质体结合蛋白质必须在合成后转移回质体中，这通过专用的输入装置（TOC/TIC复合物）来促进。在过去的几年中，已经认识到称为泛素-蛋白酶体系统（UPS）的蛋白水解系统通过用泛素标记来靶向TOC蛋白以进行降解。通过调节输入途径，质体蛋白质组可以改变，以协助特定环境或发育阶段的驯化。最近，叶绿体相关蛋白降解（CHLORAD）系统已被确定。在CHLORAD中，SP1（ppi 1基因座1的供应商）作为E3连接酶，SP2（ppi 1基因座2的供应商）作为出口通道，ATP酶Cdc 48为蛋白质提取提供动力。一个重要的问题是：胞质Cdc 48是如何与叶绿体相连的？PUX 10是一个含有UBX结构域的蛋白质家族，作为Cdc 48的辅助因子，被鉴定为与叶绿体膜上的Cdc 48、SP1、SP2和TOC蛋白相互作用。通过分析其拓扑结构、两个特异性结构域（UBX和乌巴）的作用及其在质体生物发生中的生理意义，进一步剖析其与CHLORAD的功能联系。与此同时，一个更大规模的ppi 1抑制基因突变的遗传筛选已经确定了一个新的ppi 1基因座抑制基因sp3。初步表征表明，SP3与作为底物受体的基于CUL 4的E3连接酶复合物相关联。在此基础上，我的目标是了解：SP3的底物是什么; SP3和TOC成分之间的相互作用;以及SP3在叶绿体生物发生和胁迫耐受性中的生理作用。拟议的项目福尔斯属于交叉研究理事会和BBSRC优先领域的职权范围。由于质体对作物生产力和质量做出了巨大贡献，因此从该项目中获得的知识将有助于我们可持续地提高农业生产和解决与粮食、营养和健康有关的问题。此外，了解TOC降解在应对非生物胁迫方面的预测作用可能有助于应对全球粮食安全和适应环境变化。