茶树氨基酸转运基因CsAAP3优异等位基因挖掘及分子机制研究

氨基酸含量是茶叶的重要品质指标，为茶树品种选育倍受关注的生物学性状之一。氨基酸作为重要的氮库，其在茶树体内的转运涉及一系列的跨膜运输，其转运与分配模式决定了茶叶的产量和品质。前期研究发掘了在茶树根系及幼嫩芽叶中高丰度表达的氨基酸转运基因CsAAP3，该基因可转运茶氨酸等十余种氨基酸组分，推测该基因在茶树氨基酸的转运过程中扮演着重要角色。为深入解析CsAAP3介导茶叶氨基酸的吸收转运机理，本项目拟在茶树种质资源CsAAP3等位变异及表达分析的基础上，明确该基因的亚细胞定位与组织表达，阐明CsAAP3氨基酸吸收转运功能，鉴定其启动子、上游转录因子和互作蛋白响应不同氮处理表达模式，揭示CsAAP3参与氨基酸吸收、运输及分配等跨膜运输过程及氮利用效率建成的分子调控机制。本研究可为解析茶叶富含氨基酸提供重要理论依据，且为氮利用高效茶树种质培育和茶园氮高效栽培提供指导作用，具有重要理论价值与实践意义。

Free amino acid content in young buds is one of the most important biological traits for tea variety breeding. Amino acids are key nitrogen (N) sink components and their patterns of translocation and distribution within tea plants are pivotal for tea quality and yield. Our previous study pinpointed an amino acid candidate transporter, CsAAP3, presenting at high expression level both in root and shoot across different environmental N conditions. Furthermore, CsAAP3 was characterized in model plant Arabidopsis to mediate the acquisition and translocation of a broad spectrum of amino acids, including theanine and twelve others. Therefore, CsAAP3 is hypothesized to play a central role in uptake, translocation and allocation of free amino acids. The goal of this project is to fully understand the functions of CsAAP3 in tea and the underlying molecular mechanisms. The specific objectives, are (i) to investigate variations in CsAAP3 sequence and expression profiles in tea variety germplasm; (ii) to study subcellular localization and in situ expression in selected varieties identified in (i); (iii) to functionally characterize selected CsAAP3 variants for amino acid uptake, transport in Arabidopsis and yeast; (iv) to perform histochemical analyses of CsAAP3 under control of its own promoter in response to exposure to differing N regimes; (v) to identify upstream regulatory sequences of CsAAP3 and trans-interacting transcription factors and other proteins to reveal the regulation involved in amino acids uptake, transport and allocation responsible for N utilization efficiency in tea plants. The significance of this study is that it will provide important insight into the biological basis of variation in amino acid content in tea leaves, and contribute to germplasm innovation for optimal N utilization efficiency and N nutrient management in tea plants.