Investigating how CDC48 Adapter Proteins NPL4 & UFD1 Function in Plastid Protein Regulation

叶绿体是植物和藻类细胞中发现的细胞器家族。这个群体的原型成员是光合作用的场所叶绿体。质体来自内共生细菌的祖先，因此保留了基因组。然而，它们的大部分祖先基因已经迁移到细胞核中；因此，大约3000个叶绿体结合蛋白通过被称为TOCs的膜包埋蛋白质复合体输入。最近的一项发现表明，TOC蛋白是泛素蛋白酶体系统(UPS)的靶标，它能降解蛋白质。通过降解输入器官，叶绿体蛋白质组可以改变；这可能是对环境或发育信号的反应，以促进适应。要将TOC蛋白从膜上移除，必须将它们反向移位。已鉴定的马达蛋白是广泛作用的CDC48，其活性由与其结合的接头蛋白决定。NPL4和UFD1是被认为在UPS内发挥作用的适配蛋白。在模式植物拟南芥中有两个NPL4和四个UFD1同源物。双分子荧光互补实验表明，它们确实参与了TOC的降解过程。在此基础上，我们的目标是了解：这些蛋白质的确切定位；它们如何与其他蛋白质相互作用；它们的底物的全部范围；以及这些蛋白质在应对环境压力方面具有什么生理作用。从这个项目中获得的知识将有助于我们可持续地提高农业生产，并解决与食物、营养和健康有关的问题，因为叶绿体对作物的产量和质量有很大贡献。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应对环境变化，因为全球变暖的影响对农业生产产生了持续更大的影响。

Plastids are a family of organelles found within cells of plants and algae. The prototypical member of the group is the chloroplast, the site of photosynthesis. Plastids derive from an endosymbiotic bacterial ancestor, and as such retain a genome. However, most of their ancestral genes have migrated into the nucleus; ~3000 plastid bound proteins are therefore imported through membrane embedded complexes of proteins called TOCs. A recent discovery demonstrated that TOC proteins were targeted by the ubiquitin proteasome system (UPS), which degrades proteins. By degrading the import apparatus, the chloroplast proteome can be altered; this may be in response to environmental or developmental signals to facilitate acclimation. To remove TOC proteins from the membrane, they must be retrotranslocated. The identified motor protein is the broad acting CDC48, the activity of which is determined by the adapter proteins bound to it. NPL4 and UFD1 are adapter proteins hypothesised to function within the UPS. There are two NPL4, and four UFD1 homologues in the model higher plant Arabidopsis. Bimolecular fluorescence complementation experiments suggest they do participate in this process of TOC degradation. To build on this, we aim to understand: exactly where these proteins localise; how they interact with other proteins; the full extent of their substrates; and what physiological role these proteins have in responding to environmental stress.The knowledge gained from this project will contribute to our ability to sustainably enhance agricultural production and combat issues relating to food, nutrition and health, as plastids contribute massively to crop productivity and quality. In addition, understanding the predicted role of TOC degradation in responding to abiotic stress may aid in dealing with global food security and living with environmental change as the impact of global warming exerts a continuingly greater impact on agricultural production.