自噬调控拟南芥响应低氧胁迫的分子机理研究

In plants, autophagy is a conserved pathway involving degradation of cellular compenents and essential for regulation of leaf senescence and plant defense response, but the regulatory mechanism of autophagy in plant response to abiotic stresses is poorly understood. Our previous investigations on Arabidopsis thaliana acyl-CoA binding proteins (ACBPs) showed that the membrane-associated ACBP3 recombinant protein specifically binds phosphatidylethanolamine (PE) in vitro. The interaction of ACBP3-PE directly interfered with the lipidation of autophagy-related protein ATG8 with PE, and subsequently disrupted autophagosome formation and enhanced leaf senescence and plant defense. Our prelimilary results have shown that the expression of autophagy-related ATG genes and ACBP3, as well as the autophagosome formation are hypoxia inducible. Further functional analyses showed that the autophagy deficient mutants atg2, atg5, atg7 and ACBP3-Overexpressors are hypersensitive to submergence treatment, while ACBP3-RNAi and knockout mutants display enhanced hypoxic tolerance, suggesting the importance of autophagy in hypoxia response. By analyses of gene expression profiling and bioinformatics prediction, we hypothesize that the involvement of autophagy in hypoxia response may be modulated by salicylic acid and SnRK1 kinases. The aim of this proposed study is to explore the molecular mechanism of plant autophagy in hypoxia response by using genetics, molecular biology and biochemistry means. Findings from this study may further strengthen our understanding of the biological function of autophagy and regulatory mechanism of hypoxia response in plants.

自噬是植物体内高度保守的降解细胞组分的一种生物学途径，在调控植物衰老和抗病反应中起关键作用，但目前对自噬调控植物非生物逆境反应的分子机理了解很少。我们最近发现拟南芥膜相关蛋白ACBP3与磷脂酰乙醇胺（PE）特异性结合,ACBP3-PE复合体通过干扰自噬蛋白ATG8与PE的脂质化，进而影响自噬体稳定性、植物衰老与抗病反应等生理活动。前期研究表明，拟南芥自噬相关基因的表达和自噬体的形成受低氧胁迫所诱导。自噬缺失突变体atg2、atg5、atg7和ACBP3过表达植物等对低氧胁迫非常敏感，而ACBP3-RNAi和突变体则表现出增强的低氧耐受能力。基因表达谱分析和生物信息学预测表明,自噬参与响应低氧胁迫可能受水杨酸和SnRK1激酶的调节。本项目拟利用分子生物学、植物生理生化等技术，深入探索植物自噬调控低氧胁迫反应的分子机理，研究结果对于阐明植物自噬的生理功能和低氧胁迫的调控机制具有重要的科学意义。

自噬是真核生物中高度保守的降解细胞内组分的物质循环过程。以往对拟南芥的研究发现自噬能被许多环境胁迫所激活，且自噬对于植物响应多种环境胁迫是必须的，自噬缺失突变体通常会表现出对营养缺乏、高盐、干旱、氧化胁迫和病原菌侵染等胁迫非常敏感。但是目前还没有研究报道过植物自噬与低氧胁迫之间的联系。.本项目通过反向遗传学手段和生理生化技术，深入研究了拟南芥自噬作用在响应低氧胁迫的生物学功能及对自噬作用的上游调控机制进行了探索。研究发现，低氧胁迫诱导自噬相关基因的表达和自噬体的发生，而自噬缺失突变体完全丧失对低氧胁迫耐受性。进一步研究表明，自噬介导的低氧耐受性与活性氧ROS及水杨酸/乙烯信号链的关系密切，植物NADPH氧化酶和水杨酸信号对于植物的低氧耐受性、低氧反应基因表达和自噬的激活都是必需的。而且，低氧胁迫下无氧呼吸所产生的乙醇（ethanol）可以诱导自噬发生、低氧应答基因表达以及NADPH氧化酶催化的ROS积累，提示乙醇有可能作为一种新的信号分子，在调控自噬相关的低氧应答过程中扮演着重要的作用。对自噬发生的调控机制研究揭示，AMPK激酶KIN10通过影响自噬蛋白ATG1的磷酸化，调控自噬的起始及其相关的低氧耐受性。.该工作首次揭示了自噬参与调控植物细胞内低氧诱导的ROS的稳态平衡，从而影响植物低氧反应，进一步丰富了对自噬调控植物非生物逆境应答功能及作用机理的认识。