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.

质体是一组广泛分布在植物和藻类中的特殊细胞器。该组中最具典型性的成员无疑是叶绿体，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源自祖先蓝细菌，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转移到核基因组中。因此，编码的质体结合蛋白必须在合成后转移回质体，这通过专用的导入装置（TOC/TIC 复合物）来促进。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认为可以通过泛素标记来靶向 TOC 蛋白进行降解。通过调节输入途径，可以改变质体蛋白质组以帮助适应特定环境或发育阶段。最近，叶绿体相关蛋白降解（CHLORAD）系统已被鉴定。在 CHLORAD 中，SP1（ppi1 位点 1 的抑制剂）充当 E3 连接酶，SP2（ppi1 位点 2 的抑制剂）充当退出通道，ATP 酶 Cdc48 提供蛋白质提取的动力。一个重要的问题是：胞质 Cdc48 是如何与叶绿体结合的？ PUX10 属于含有 UBX 结构域的蛋白家族，作为 Cdc48 辅助因子，被鉴定与叶绿体膜上的 Cdc48、SP1、SP2 和 TOC 蛋白相互作用。我将通过分析其拓扑结构、其两个特定结构域（UBX 和 UBA）的作用及其在质体生物发生中的生理意义，继续剖析其与 CHLORAD 的功能联系。与此同时，对 ppi1 抑制突变的更大规模遗传筛选发现了 ppi1 基因座的一个新抑制基因，称为 sp3。初步表征表明 SP3 与作为底物受体的基于 CUL4 的 E3 连接酶复合物结合。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；以及 SP3 在叶绿体生物发生和胁迫耐受中的生理作用。拟议项目属于交叉研究委员会和 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，从该项目中获得的知识将有助于我们可持续提高农业生产并解决与粮食、营养和健康有关的问题的能力。此外，了解 TOC 降解在应对非生物胁迫中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。