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背景：Nitrogen (N) is a major nutrition element for tea plant. However, application of high levels of N negatively causes environmental problems. Therefore, improved N use efficiency (NUE) of tea plant will be highly desirable and crucial for sustainable tea cultivation. Autophagy plays a central role in N recycling and holds potential to improve N utilization, and many AuTophaGy-related genes (ATGs) are involved in the autophagy process. 结果：Here, CsATG3a was identified from Camellia sinensis, and the functions involved in N utilization was characterized in arabidopsis (Arabidopsis thaliana). The transcript level of CsATG3a in tea leaves increases with their maturity. Relative to the wild type (WT) arabidopsis, two CsATG3a-overexpressing (CsATG3a-OE) lines exhibited improved vegetative growth, delayed reproductive stage, and upregulated expression of AtATGs (AtATG3, AtATG5 and AtATG8b) in a low N (LN) hydroponic condition. The expression levels of AtNRT1.1, AtNRT2.1, AtNRT2.2, AtAMT1.1 and AtAMT1.3 for N uptake and transport in roots were all significantly higher in CsATG3a-OE lines compared with those in the WT under LN. Meanwhile, the overexpression of CsATG3a in arabidopsis also increased N and dry matter allocation into both rosette leaves and roots under LN. Additionally, compared with WT, improved HI (harvest index), NHI (N harvest index), NUtE (N utilization efficiency) and NUE (N use efficiency) of CsATG3a-OE lines were further confirmed in a low-N soil cultured experiment. 结论：Together, these results concluded that CsATG3a is involved in N recycling and enhances tolerance to LN, indicating that CsATG3a holds potential promise to improve NUE in tea plant.. 氮（N）是茶树的主要营养元素。然而，施用高水平的氮会造成环境问题。因此，提高茶树的氮利用效率（NUE）对于可持续的茶树栽培是非常重要的。自噬在氮循环中起着核心作用，并具有提高氮利用率的潜力，许多自噬相关基因（ATG）参与了自噬过程。在这里，CsATG3a从茶树中鉴定出来，并且在拟南芥中表征了N利用的功能。茶叶中CsATG3a的转录水平随着成熟度的增加而增加。相对于野生型（WT）拟南芥，在低氮（LN）水培条件下，两个CsATG3a过表达（CsATG3a-OE）系表现出改善的营养生长、延迟的生殖阶段和上调的AtATG（AtATG3、AtATG5和AtATG8b）表达。与LN下的WT相比，CsATG3a-OE系中根系中氮吸收和运输的AtNRT1.1、AtNRT2.1、AtNRT2.2、AtAMT1.1和AtAMT1.3的表达水平均显著升高。同时，CsATG3a在拟南芥中的过表达也增加了氮和干物质在LN下分配到莲座叶和根中。此外，与WT相比，在低氮土壤培养实验中，CsATG3a OE系的HI（收获指数）、NHI（N收获指数），NUtE（N利用效率）和NUE（N使用效率）得到了进一步证实。总之，这些结果得出结论，CsATG3a参与了氮的循环，并增强了对LN的耐受性，这表明CsATG3a具有改善茶树NUE的潜力。
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