LAUSR

Abstract In this study, ‘Zhongcha108′ (ZC) and its offspring cultivar ‘Zhongming7′ (ZM) were used to investigate the variation in characteristic compounds at different leaf positions. The results showed that there were differences between the two cultivars beyond the leaf position. The concentrations of theanine and caffeine were significantly higher in ZM, whereas more catechins accumulated in ZC. The expression levels of genes related to the theanine, caffeine and catechin pathways were determined by quantitative real time PCR. Compared with ZC, ZM showed higher expression levels of genes involved in theanine biosynthesis and transport, including GOGAT, GS(TS), AlaAT, AspAT, AS and AAP, suggesting that effective biosynthesis and translocation facilitate theanine accumulation in ZM. The caffeine content in ZC was positively correlated with the gene expression of TCS. However, such a correlation was not observed in ZM, which might be related to highly expressed genes involved in caffeine degradation, including CYP1A2, ALN and XO. Furthermore, catechin biosynthesis was regulated by different structural genes in the two cultivars. Higher catechins contents in ZC were related to higher genes expression levels, particularly for PAL, 4CL, F3H, FLS and LAR. A correlation analysis among key genes involved in theanine, caffeine, and catechin biosynthesis also showed consistent results. In ZC, catechins biosynthesis was more active, which inhibited the biosynthesis of nitrogen-rich metabolites, particularly for theanine. The balance of secondary metabolisms in ZM was shifted toward increasing the synthesis of nitrogen-containing compounds, i.e., theanine and caffeine. Taken together, these data reveal different regulatory mechanisms of theanine, caffeine, and catechins within two genetically similar tea cultivars. This work provides an important basis for further research on the characteristic metabolites of tea plants.