干旱条件下苹果树体的水分利用效率是影响我国旱区苹果高效生产的关键因子之一。项目组前期研究发现，苹果自噬基因MdATG8i显著响应干旱，其过表达植株提高了长期干旱下苹果的WUE。蛋白质组分析获得了与干旱下WUE相关的MdAGO4.1蛋白，并发现其与MdATG8i互作。在此基础上，本项目拟对干旱下MdATG8i调控苹果WUE的生物学功能进行深入研究；进一步鉴定MdATG8i与MdAGO4.1的互作关系，结合MdATG8i转基因植株自噬活性与MdAGO4.1蛋白水平间的相关分析，解析MdATG8i通过自噬途径调节MdAGO4.1蛋白积累的机理；通过RNA免疫沉淀测序，筛选与长期干旱下苹果WUE相关的MdAGO4.1靶标miRNAs。目的是阐明干旱下MdATG8i通过MdAGO4.1蛋白调节下游关键miRNAs的表达，从而调控苹果WUE的分子机理，为苹果WUE调控和遗传改良提供理论依据。

Water use efficiency (WUE) of apple tree under drought stress is one of the key factors affecting the efficient apple production in arid areas of China. Our previous study found that apple autophagy gene MdATG8i significantly responded to drought stress, and its overexpression increased WUE of apple tree under long-term drought condition. Through proteomic analysis, the protein MdAGO4.1 related to apple WUE under drought was obtained. Further studies showed that MdAGO4.1 could interact with MdATG8i. On this basis, this project intends to conduct an in-depth study on the biological function of MdATG8i in regulating apple WUE under drought. Combined with the further identification of protein interaction between MdATG8i and MdAGO4.1, and the correlation analysis between autophagy activity and MdAGO4.1 protein level in MdATG8i transgenic plants, the mechanism of MdATG8i in regulating MdAGO4.1 protein accumulation by autophagy pathway will be analyzed. In addition, MdAGO4.1 target miRNAs related to apple WUE under long-term drought will be screened by RNA immunoprecipitation sequencing. The purpose was to clarify the molecular mechanism of MdATG8i in regulating apple WUE under drought, by mediating the expression of downstream key miRNAs through MdAGO4.1 protein, so as to provide theoretical basis for WUE regulation and genetic improvement in apple.