采用原位杂交技术对茶树咖啡碱合成酶基因mRNA的表达进行了研究。结果表明，茶树叶片的表达主要在栅栏组织，该组织的细胞质、细胞核上均有表达，而液泡却没有；叶主脉表达分布在薄壁组织、韧皮部，但韧皮部表达稍弱；幼茎表达分布在韧皮部；不同品种之间的表达位置基本相似、表达信号却有差异。结果还显示，春梢第一片叶比秋梢第一片叶表达信号强；加工技术上绿茶摊青过程0.5 h、1 h、2 h有明显表达信号，而红茶萎凋6 h、8 h、10 h及乌龙茶摇青过程6 h、8 h、10 h的叶子则看不到。

The expression of caffeine synthase gene mRNA in tea plant by means of in situ hybridization was investigated. Results showed that the expressional sites is mainly located in the cell cytoplasm and nucleus of palisade tissue, but not in vacuole. The expressional sites of leaf vein are mainly in parenchyma and phloem, however, that in phloem is weaker. The expressional sites in young stalk are in phloem. The expressional sites in different cultivars are basically similar, but the expressional signal is different. Results also showed that the expressional signal of the first fresh leaf in spring is stronger than that in autumn. In terms of processing technique, the green teas which are spread 0.5 h、1 h、2 h showed apparent expressional signal, but the signal was not observed in the black teas withered for 6 h、8 h、10 h and Oolong teas shaken for 6 h、8 h、10 h.