茶叶中儿茶素代谢途径调控相关的蛋白质组学研究

Catechins are the main secondary metabolites in tea with enormous implications to human health in being as anticarcinogenic, antioxidant and antibacterial. So far, in addition to non-galloylated catechins C and EC, the metabolic pathway of other kinds catechins, especially galloylated catechins, are still poorly understood. The point is the key enzymes and genes regulating the catechins metabolic pathway have not been confirmed. In previous studies, researches on catechins biosynthesis mainly focused on individual or several enzyme(s) and gene(s). However, the catechins biosynthesis looks more like a complex metabolic grid referring to many genes and proteins than a linear pathway. Therefore, the comprehensive and all-sided studies on catechins metabolic pathway are urgently to be carried out. Comparative proteomics analysis has become a basic method for the large-scale analysis of proteins in many fields of plant biology, which would give insight into the functional gene products and how their expression is modulated during important life processes. Based on a large number of genomic and transcriptome data obtained from our former studies, the project will combine the technologies of proteome, phytochemistry and physioecology to compare and analyze catechins diversities between different Camellia species, seasons, developmental stages and inducer light treatments. The differentially expression proteome of leaves and chloroplast were discussed with regard to the impact of different factors on catechins, especially galloylated catechins. Those important genes and enzymes participate in catechins biosynthesis and their interaction will be uncovered. To understand the gene and proteins regulatory network of catechins biosynthesis in tea would be helpful to provide a theoretical basis for directional breeding and planting of Camellia sinensis with high content of functional component.

茶叶中富含的儿茶素是一类具有重要保健功能的植物次生代谢产物。目前我们对大多数儿茶素的代谢途径还不十分清楚，其中对酯型儿茶素的代谢途径更是知之甚少。以往儿茶素代谢的研究主要集中在对某几个关键酶或基因进行分析研究。然而，事实上儿茶素代谢是个多基因和蛋白共同参与的调控网络，因此要了解儿茶素的代谢途径，必须在大尺度上全面系统地对儿茶素代谢途径进行深入研究。基于我们前期工作中已获得的大量茶树基因组和转录组数据的基础上，本项目拟采用蛋白质组学技术，辅助以植物化学和植物生理生态学的研究方法。通过对比不同山茶物种间儿茶素的显著差异；探讨不同茶树叶片中儿茶素的季节变化模式；比较茶树叶片不同发育阶段儿茶素的变化式样；结合不同光照处理下茶树儿茶素的差异。通过叶片和叶绿体差异蛋白质组的比较，确定儿茶素，特别是酯型儿茶素代谢途径中的关键酶和基因及它们的亚细胞定位和调控网络。为茶树的定向育种和栽种提供重要的理论支持。

茶叶中富含的儿茶素是一类具有重要保健功能的植物次生代谢产物。酯型儿茶素在茶树体内儿茶素类中占有明显优势份额，它是决定茶叶滋味与保健作用最重要的功能成分。因此，研究儿茶素，尤其是酯型儿茶素在茶树中的合成对改善茶叶滋味和提高茶叶保健功效具有非常重要的意义。本项目选取山茶属茶组植物云南大叶茶（Camellia.sinensis var.assamica）为主要研究对象，采用系统生物学研究技术，辅助以植物化学和生理生态学的研究方法，从多角度，多层面地探寻了儿茶素，尤其是酯型儿茶素的代谢途径中的关键酶和基因以及它们之间的调控网路。通过对比儿茶素含量和种类显著差异的云南山茶（C. reticulata）、小叶茶（C.sinensis var. sinensis）和云南大叶茶的转录组序列信息，发现儿茶素代谢通路中的全部相关基因在三种山茶属植物的转录组中均有发现，只是特定基因的数量和结构发生了变异。我们推测该结果可能与这三种山茶属植物儿茶素含量和种类的差异有关。在获得上述转录组数据的基础上，我们对不同光质影响茶树叶片中儿茶素含量变化的机理机制进行了研究，结果显示长波长的红光较短波长的蓝光有利于抑制茶叶儿茶素的积累，光质对酯型儿茶素含量变化影响显著。差异蛋白质组分析发现，除了儿茶素代谢途径中的看家基因外，一些参与能量生成与转化（Energy production and conversion），脂类代谢（Lipids metabolic process）,光合作用（Photosynthesis），细胞代谢过程（Cellular metabolic process）和转运过程（Transport）的蛋白质均与光质调控儿茶素合成代谢密切相关，例如谷胱甘肽巯基转移酶（GST）。这些差异蛋白中很多定位于叶绿体。此外，我们利用代谢组学和转录组学对氮营养元素对茶树儿茶素合成代谢的影响进行了深入细致的分析研究，发现不同形态的氮元素作用差异明显，其中一氧化氮能够显著增加酯型儿茶素的积累，与酯型儿茶素的合成代谢密切相关。依据实验结果我们认为在富集长波长光谱和氮肥适中的环境条件下生长的茶树适宜生产高品质茶叶；反之，则适宜栽培富含儿茶素茶叶的茶树。本项目不仅为我们揭示了与儿茶素，特别是酯型儿茶素代谢途径密切相关的关键基因和蛋白以及它们之间的调控网络，还提出了特种茶树的定向栽培方法。