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

东方美人是一种风味丰富的乌龙茶，由台湾的茶叶绿色叶蝉（Jacobiasca formosana）制成。本研究从天然产物化学、生物化学、分子生物学等多个方面对茶叶特征香气形成的分子基础进行了研究。乌龙茶样品由被昆虫侵染/未被昆虫侵染的茶叶制备。在制造过程的每个步骤中获得样品，并由专业的品茶师进行评估测试和GC-MS分析。结果表明，经虫蛀处理的茶叶，其香气的质量和数量均优于无虫蛀或虫蛀少得多的茶叶，具有上级的特点。已证实，雌三烯酚及其相关化合物2，6-二甲基-3，7-辛烯-2，6-二醇是引起该昆虫攻击的原因。通过Megasort分析的差异筛选，鉴定了响应于昆虫攻击和茶叶制造过程诱导的基因。其中，我们的兴趣集中在编码胁迫响应的基因和胁迫响应的化合物，如棉子糖和脱落酸在茶叶加工的每个步骤中获得的样品中的含量进行了定量分析的HPLC。发现这两种化合物在日光萎凋步骤中显著增加，这与在该步骤中负责其生物合成的基因的表达具有良好的相关性。这些结果表明，东方美人茶的叶片受到虫害胁迫和茶叶加工过程如日光萎凋和翻炒的影响很大，这些胁迫是增加这种特色乌龙茶特有香气化合物产生的重要因素。

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.