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.

质体是一组专门的细胞器，广泛分布于植物和藻类中。这个群体中最典型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。质体来自祖先蓝藻通过内共生事件，因此保留了一个真菌型基因组。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在合成后必须被转移回质体中，这是由专用的进口装置（TOC/TIC复合物）促进的。在过去的几年里，一种被称为泛素-蛋白酶体系统（UPS）的蛋白质水解系统被认为是通过泛素标记来降解TOC蛋白的。通过调节输入途径，可以改变质体蛋白质组，以帮助适应特定的环境或发育阶段。最近，一个叶绿体相关蛋白降解（CHLORAD）系统被发现。在CHLORAD中，SP1 （ppi1基因座1的抑制因子）作为E3连接酶，SP2 （ppi1基因座2的抑制因子）作为退出通道，而atp酶Cdc48为蛋白质提取提供动力。一个重要的问题是：细胞质Cdc48是如何与叶绿体相连的？PUX10属于含ubx结构域的蛋白家族，具有Cdc48辅助因子的功能，可与叶绿体膜上的Cdc48、SP1、SP2和TOC蛋白相互作用。我将通过分析它的拓扑结构，它的两个特定结构域（UBX和UBA）的作用，以及它在质体生物发生中的生理意义，来解剖它与CHLORAD的功能联系。与此同时，对ppi1的抑制基因突变进行了更大规模的基因筛选，发现了ppi1位点的一个新的抑制基因sp3。初步表征表明SP3与cul4为基础的E3连接酶复合物结合，作为底物受体。在此基础上，我的目标是理解：SP3的底物是什么；SP3与TOC组分的相互作用；SP3在叶绿体生物发生和胁迫耐受中的生理作用。拟议的项目属于跨研究委员会和BBSRC优先领域的职权范围。由于质体对作物产量和质量有巨大贡献，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，并解决与粮食、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中的预测作用，可能有助于应对全球粮食安全和环境变化。