拟南芥NBR1介导的叶绿体外膜蛋白选择性自噬降解的机理研究

叶绿体是植物进行光合作用和环境响应的重要细胞器，在植物发育和抗逆过程中起关键作用。负责叶绿体前体蛋白识别与转运的外膜TOC复合体直接调控着叶绿体内部蛋白组分, 因此外膜TOC蛋白的动态平衡对叶绿体功能的实施至关重要。前期研究结果表明叶绿体外膜TOC蛋白受到泛素-蛋白酶体的直接调控，同时逆境胁迫也可以导致整个叶绿体通过自噬降解。但TOC蛋白是否受到选择性自噬的调控并不清楚。本项目中，申请人首次确认了叶绿体外膜TOC蛋白可以通过选择性自噬途径进行降解，并利用免疫沉淀-质谱（IP-MS）技术获得了一个受体蛋白NBR1，在此基础上，本项目将系统的分析NBR1介导叶绿体选择性自噬的分子机理，揭示叶绿体选择性自噬对叶绿体生长发育、转运活性及逆境抗性方面的调控。另外，申请人将对IP-MS获得的其他受体蛋白进行验证，进一步丰富叶绿体蛋白稳态调控的分子网络，为下一步作物品质和逆境抗性的遗传改良提供理论依据。

Chloroplast is an important organelle for photosynthesis and environment response in plants, and plays vital role in plant development and stress tolerance. The chloroplast outer membrane TOC proteins, which are responsible for the recognition and transport of chloroplast precursor proteins, impact the internal chloroplast proteome. Previous studies have shown that TOC proteins are directly regulated by the ubiquitin-proteasome system, and that abiotic stress can also lead to autophagic degradation of whole chloroplasts. However, it is not clear whether TOC proteins are regulated by selective autophagy. In this project, we confirmed that TOC proteins could be degraded by selective autophagy, and identified a receptor protein NBR1 through IP-MS setting ATG8 as bait. Based on these studies, we will further explore the mechanism of the chloroplast selective autophagy mediated by NBR1. This will lay the foundations for understanding the function of autophagy in chloroplast growth and development, protein import efficiency and stress sresistance. In addition, we will verify other receptor proteins obtained from proteomics, to extend the molecular network of chloroplast protein homeostasis.This study will also provide a theoretical basis for the genetic improvement of crops regarding quality and stress resistance.