糖信号对茶树叶片黄酮醇苷合成积累的调节和作用机制

Flavonol glycosides are important secondary metabolites in tea plant, which contributes to the bitter and astringent taste of tea. Sugars are basic biomaterials for secondary metabolisms in plant, which regulate many life activities through sugar signal transduction. This project is to reveal the mechanism of sugar-mediated biosynthesis of flavonol glycosides in tea plant through determination of flavonol glycosides and soluble sugars, relevant gene expressions and enzymatic activities regarding sugar metabolism, transporting, sugar sensing and signal transduction. Branch cut-offs of tea plant are to be treated with different exogenous sugars so as to find out the most important sugar component closely related to the biosynthesis of flavonol glycosides and related sugar signaling pathway, as well as the differential responses of various tea cultivars to exogenous sugar. Inhibiter or blocker treatments are to testify the crucial step, critical gene and enzyme in relevant sugar signaling pathway. This study would give essential information to understand the regulation of flavonol glycosides biosynthesis from a viewpoint of glycobiology, and the promising results help to better understand the metabolism of flavonol glycosides and the regulatory network of tea secondary metabolism, and also provide scientific basis for future control techniques on biosynthesis of flavonol glycosides.

黄酮醇苷是茶树重要的次生代谢产物，是茶叶苦涩味物质之一。可溶性糖是植物次生代谢的基础合成原料，并通过信号通路调控植物多项生命活动。本项目拟通过检测不同茶树品种新梢生育中黄酮醇苷和可溶性糖组分及含量的变化，结合基因定量表达和关键酶活力检测从糖代谢、糖转运蛋白和糖信号通路的角度探讨糖信号调节黄酮醇苷合成积累的作用机制。采用不同外源糖诱导处理茶树离体枝条，揭示与茶树黄酮醇苷合成密切相关的关键糖组分及其糖信号转导机制，以及不同品种茶树黄酮醇苷合成途径对糖诱导的差异响应，进而通过抑制剂处理对糖信号转导的关键步骤、关键基因及酶进行功能验证。本项目从糖生物学的角度阐释糖作为信号因子对茶叶黄酮醇苷合成的调控和作用机制，研究结果有助于更深入地了解茶叶黄酮醇苷的代谢机理及茶树次生代谢调控网络，为开发相应的控制技术措施提供科学依据。

可溶性糖是茶叶涩味物质黄酮醇苷合成的直接前体和间接前体，同时可作为信号分子参与植物多项生理代谢调控。本研究通过检测茶树新梢自然生育状态下不同成熟度叶片黄酮醇苷和可溶性糖组成，结合基因表达、蛋白质丰度和关键酶活力研究黄酮醇苷合成的网络调控及其与初生代谢的关联，并采用茶树离体枝条外源糖和己糖激酶（HXK）抑制剂诱导处理实验进一步验证糖信号对黄酮醇苷合成的调节机制，研究不同品种茶树类黄酮合成途径对糖信号的差异响应。获得的主要结果包括：（1）自然生育状态下茶树叶片黄酮醇苷总含量尤其是槲皮素糖苷与蔗糖含量具有显著相关性。黄酮醇苷合成受到类黄酮合成上游基因和下游基因黄酮醇合成酶（FLS）、类黄酮-3-O-糖基转移酶（UFGT）的共同调节。茶树叶片蔗糖合成能力较弱时类黄酮合成较活跃。（2）离体实验证明蔗糖是调节茶树HXK表达的关键糖组分，糖信号可通过SPS/SPP介导的蔗糖合成和SUS-INV蔗糖代谢平衡调节黄酮醇苷合成。（3）不同品种茶树叶片HXK和类黄酮合成下游分支关键基因对糖信号的响应存在差异。本研究从糖生物学的角度阐释糖作为信号因子对茶叶黄酮醇苷合成的调控和作用机制，研究结果揭示了蔗糖合成代谢与类黄酮次生代谢存在直接作用，为后续开展茶树幼叶类黄酮物质富集与嫩梢光合作用及抗逆性互作机制的研究奠定了科学基础。项目资助发表SCI论文3篇，待发表2篇。资助期间1人由中级职称晋升副高级，培养/协助培养研究生7名，4人已获得学位，3人在读。