Clarification of Molecular Basis of the Characteristic Aroma Formation in the Formosa Oolong Ted Produced from Tea leaves Infested by the Tea Green Leafhopper

东方丽人是一种味道浓郁的乌龙茶，由台湾茶绿叶蝉(Jacobiasca Formosana)为害的茶叶制成。我们通过天然产物化学、生物化学、分子生物学等多种方法对茶叶特有香气形成的分子基础进行了研究。乌龙茶样品是从感染/未感染虫害的茶叶中制备的。样品在制作过程的每一步都获得，并接受专业品茶师的评估测试和GC-MS分析。虫害茶树生产的茶叶在香气质量和香气量上均优于无虫害或虫害较少的茶叶。黄曲烯醇及其相关化合物2，6-二甲基-3.7-辛二烯-2，6-二醇被证实是造成这次害虫攻击的原因。通过基于Megasort分析的差异筛选，鉴定了诱导虫害的基因和茶叶的制作过程。其中，我们的兴趣主要集中在应激反应基因的编码上，并用高效液相色谱法对茶叶加工过程中每个步骤获得的茶叶样品中的应激反应化合物如棉籽糖和脱落酸的含量进行了定量分析。研究发现，这两种化合物在太阳枯萎阶段都显著增加，这与负责其生物合成的基因的表达有很好的相关性。这些结果表明，东方丽人的茶叶受虫害胁迫和日光凋萎、翻身等制茶工艺的影响很大，这些胁迫是增加这种特色乌龙茶特有香气化合物产量的重要因素。

Oriental Beauty is a flavor-rich oolong tea produced from tea leaves infested by the tea green leafhopper (Jacobiasca formosana) in Taiwan. We have studied to clarify the molecular basis of the characteristic aroma formation of the tea by various approaches such as natural product chemistry, biochemistry, and molecular biology. Oolong tea samples were prepared from tea leaves infeted/noninfested by the insects. Samples were obtained at each step of the manufacturing process and subjected to evaluation tests by professional tea tasters and to GC-MS analysis. The tea produced from tea leaves infested by the insects was found to be superior in the quality and quantity of aroma to that from tea leaves without or with much less the insect attack. Hotrienol and its related compound, 2,6-dimethyl-3.7-octadiene-2,6-diol, were confirmed to be responsible for the insect attack. Genes induced in response to the insect attack and the tea manufacturing processes were identified by the differential screening based on the Megasort analysis. Among them our interests were focused into the genes encoding the stress-responded ones and the amounts of the stress-responded compounds such as raffinose and abscisic acid in tea samples obtained at each step of the tea processing were quantitatively analyzed by HPLC. Both compounds were found to increase dramatically at the solar withering step in good correlation with the expression of the genes responsible for their biosynthesis at the step. These results have revealed that the tea leaves of Oriental Beauty are greatly affected by the stresses of the insect attack and the tea manufacturing processes such as solar withering and turning-over, and these stresses are important factors to increase the production of the aroma compounds characteristic to this characteristic oolong tea.