逆境胁迫下线粒体交替氧化酶对光合作用调控机理的研究

Plants in their natural environment frequently face various abiotic stresses, such as drought, high salinity, and chilling.The mitochondrial electron transport chain includes an alternative oxidase (AOX) that is hypothesized to aid photosynthetic metabolism, perhaps by acting as an additional electron sink for photogenerated reductant or by dampening the generation of reactive oxygen species. AOX genes have been shown to be highly responsive to abiotic stresses.Using transgenic plants with varying levels of AOX expression, it has been confirmed that AOX is important for abiotic stress tolerance. But the molecular mechanism how AOX regulates photosynthesis during abiotic stress is not known. Our previous studies demonstrated AOX-derived plastidial NADPH/NADP+ changes function as a metabolic signal regulating plastidial protein import and chlorophyll biosynthesis. We will test whether AOX regulates photosynthetic capacity by maintaining balance of redox state between chloroplast and mitochondrial. We will also performed Chloroplast Proteomics and RNA sequence experiments using AOX overexpression transgenic plants and AOX RNAi plants to screen candidate targets. Then we will study how AOX regulates these chloroplast proteins import from cytoplasm into chloroplast under abiotic stress. Our results therefore will establish a new mechanism by which AOX functions to maintain photosynthetic capacity during abiotic stress in Arabidopsis.

逆境引起作物减产的一个重要原因就是破坏了光合作用的正常进行。因此，研究植物光合作用的保护机理，对于在农业生产中提高作物的抗逆能力具有重要的意义。交替氧化酶（AOX）是植物线粒体内的重要末端氧化酶，通过交替氧化支路传递电子而不产生ATP。胁迫条件下，AOX表达水平的提高和功能的正常发挥能够有效保护光合电子传递链，避免活性氧自由基的过量积累对植物的生理活动尤其是光合作用的破坏。我们研究发现在植物转绿期或者高光照情况下，AOX在线粒体与叶绿体之间的信号传导过程中具有重要作用。所以，深入探索逆境条件下AOX对光合作用的调控机制具有重要意义。本项目拟弄清逆境条件下，AOX介导的线粒体与叶绿体间的信号传导以及影响质体蛋白转运的分子机理，探讨AOX在植物逆境条件下对维持光合作用正常进行的作用。

逆境引起作物减产的一个重要原因就是破坏了光合作用的正常进行。因此，研究植物光合作用的保护机理，对于在农业生产中提高作物的抗逆能力具有重要的意义。交替氧化酶（AOX）是植物线粒体内的重要末端氧化酶，通过交替氧化支路传递电子而不产生ATP。胁迫条件下，AOX表达水平的提高和功能的正常发挥能够有效保护光合电子传递链，避免活性氧自由基的过量积累对植物的生理活动尤其是光合作用的破坏。我们研究发现在植物转绿期、高光照和干旱胁迫等情况下，AOX在线粒体与叶绿体之间的信号传导过程中具有重要作用。干旱胁迫等逆境条件下，AOX介导线粒体（NADH/NAD+）与叶绿体（NADPH/NADP+）间的氧化还原水平的改变，可以作为一种代谢信号调控质体蛋白的转运。并且我们的研究还发现依赖于AOX途径的细胞自噬参与乙烯诱导的植物耐旱性。我们的研究结果阐明了AOX在植物逆境条件下对维持光合作用正常进行的作用。