茶树萜烯及其糖苷化合物响应茶云纹叶枯病菌侵染反应的分子机制

The terpenes is the main defense compound of tea plant (Camellia sinensis (L) O. Kuntze) respond to pest attack, but its function and mechanism of action in tea plant response to pathogen are unclear. Tea brown blight (Colletotrichum camelliae Massee) is a fungal disease that seriously harms the tea leaves and affecting the normal growth of tea trees. Based on the previous research, the project used metabolomics method to analyze the different of composition and content of terpenes in normal tea leaves and tea seedlings infected with fungal, then KEGG pathway and enrichment of differential terpenes were are analyzed to clarify the metabolic pathways. Subsequently, the transcriptomics (RNA-Seq) used to analyze the differentially expressed genes in the terpene metabolic pathway of tea plant by different treatments, and then the GO function annotation and KEGG pathway analysis were performed to obtain key functional genes. Further, the differential gene and metabolism was correlated with analysis to construct a regulatory network. Finally, the biological function of key differential genes was verified by prokaryotic expression system and overexpression system. This study will clarify the molecular mechanism of the functional of terpenes and their glycosides in response to disease stress in tea trees, and will provide a basis for the use of molecular markers guide to disease resistance breeding and disease prevention and control.

茶树萜烯化合物是茶树遭遇害虫危害时产生或释放的主要防御化合物，但其在茶树应对病源菌胁迫过程中的功能及作用机制不清晰。茶云纹叶枯病是严重危害茶树叶部的真菌病害，是影响茶树正常生长的重要限制因素之一。申请人在前期研究基础上，本项目采用代谢组学方法，分析正常茶苗和茶云纹叶枯病菌侵染不同阶段茶苗的萜烯及其糖苷类化合物组成、含量的差异，并进行KEGG富集分析，明确差异化合物的代谢途径。随后采用RNA-Seq转录组学策略，分析不同处理后茶树萜烯代谢通路上的差异表达基因，并进行GO功能注释和KEGG通路分析获得关键功能基因。进一步将差异基因与差异代谢关联分析，构建功能基因与差异代谢物的调控网络。最后通过原核表达体系和过表达体系的构建验证关键差异基因的生物学功能。本研究将阐明茶树萜烯及其糖苷类物质在茶树响应病害胁迫中的功能及作用的分子机制，也将为利用分子标记进行茶树抗病性育种和病害防控提供研究基础。

茶云纹叶枯病是严重危害茶树叶部的真菌病害，影响茶叶的产量和品质。本研究发现茶树被致病菌侵染后，茶树叶片中萜类化合物含量显著增加，单萜代谢通路基因显著富集。通过关联分析，筛选并验证了2个增强茶树抗性的关键差异基因，茶树香叶醇合成基因和新薄荷醇合成基因。其中茶树香叶醇合成基因在茶树中被首次发现和鉴定。进一步研究发现，病原菌侵染茶树时，茶树香叶醇合成酶通过可变剪切形式调控香叶醇的合成，增强茶树对病原菌侵染的抵御。致病菌侵染茶树，茶树新薄荷醇合成基因被显著的诱导表达，把薄荷酮转化为新薄荷醇，提高茶树的抗病性。深入研究表明，香叶醇合成基因和新薄荷醇合成基因均是通过介导水杨酸下游的抗性基因的表达，调控茶树的抗病性。本研究证明了茶树萜烯类化合物合成酶在茶树抵御致病菌侵染过程中发挥重要的作用，并解析了其作用机制。该研究将为茶树抗性品种选育和茶树病害防控提供新思路和研究基础。