自噬基因ATG8对柑橘果实类胡萝卜素合成的影响及其上游转录调控机制

自噬是将细胞内受损细胞器和错误折叠蛋白降解的过程。自噬相关蛋白ATG8是自噬形成过程的限速步骤，在植物中ATG8有9个亚型（ATG8a-i）。不同ATG8亚型之间存在调控生长发育和应对逆境胁迫的功能分化，上游转录调控也具有特异性，但ATG8不同亚型参与代谢物质形成的机制尚未明晰，柑橘中ATG8的上游转录调控机理也未知。前期红光处理转色加快的柑橘果实代谢组和转录组数据分析，发现其中一个ATG8的转录水平与类胡萝卜素积累显著相关。并构建该ATG8在柑橘和番茄的过表达或RNAi的遗传材料，初步证实了该ATG8影响柑橘果实类胡萝卜素的生物合成。基于此，本项目将利用生化实验重点研究揭示该ATG8对柑橘果实类胡萝卜素代谢途径的作用机制，同时结合细胞生物学手段，阐明此ATG8参与类胡萝卜素品质形成的细胞过程。本研究将加深学界对自噬的生物学功能的认识，同时也为调控果实品质的形成提供了新视角。

Autophagy is an inner cellular process that degrades damaged organelles and proteins in cells. In plants, Autophagy-related protein (ATG8), contains 9 subtypes of ATG8 (ATG8a-i), which is the main rate-limiting step for autophagy process. Different ATG8 subtypes have functional differentiation that regulates growth, development and responsive to stresses, and specifically exert diverse upstream transcriptional regulation. However, whether ATG8 subtypes function on the metabolites accumulation in plants remains unclear. The upstream transcriptional regulation mechanism of ATG8 subtypes in citrus is also unknown. Our previous metabolomic and transcriptomic data revealed that the transcript levels of a ATG8 was significantly related to the accumulation of carotenoids in red-light-treated citrus fruits. We further confirmed that this ATG8 is indeed involved in carotenoid biosynthesis by overexpressing or knocking down (RNAi) this ATG8 in citrus. On this basis, this project will further perform biochemical experiments to explore the transcriptional regulation of this ATG8 in citrus. Moreover, we will also conduct cellular/autophagy-related experiments to further trace cellular autophagy process of this ATG8 during carotenoid biosynthesis process. Together, this study will provide a novel insight for autophagy function in this field, and open a new avenue to regulate fruit quality in horticultural plants.