Flavonoids and caffeine are the major secondary metabolites with beneficial bioactivity for human health in tea plants, and their biosynthesis pathway and regulatory networks have been well-deciphered. However, the accumulation traits of flavonoids and caffeine in different tea cultivars was insufficient in investigation. In this study, metabolomic and transcriptomic analyses were performed to investigate the differences of flavonoids and caffeine accumulation and regulation between Chinese varieties, including the ‘BTSC’ group with green leaf, the ‘BTZY’ group with purple foliage, and the ‘MYC’ group comprising Assam varieties with green leaf. The results showed that most of the flavonoids were down-regulated in the ‘MYC’ group; however, the total anthocyanin contents were higher than that of the ‘BTSC’ group while lower than that of the ‘BTZY’ group. An ANS (Anthocyanin synthase) was significantly up-regulated and supposed to play a key role for anthocyanin accumulation in the ‘BTZY’ group. In addition, the results showed that esterified catechins were accumulated in the ‘BTSC’ and ‘BTZY’ groups with high abundance. In addition, SCPL1A (Type 1A serine carboxypeptidase-like acyltransferases gene) and UGGT (UDP glucose: galloyl-1-O-β-d-glucosyltransferase gene) potentially contributed to the up-accumulation of catechins esterified by gallic acid. Interestingly, the results found that much lower levels of caffeine accumulation were observed in the ‘MYC’ group. RT-qPCR analysis suggested that the expression deficiency of TCS1 (Tea caffeine synthase 1) was the key factor resulting in the insufficient accumulation of caffeine in the ‘MYC’ group. Multiple MYB/MYB-like elements were discovered in the promoter region of TCS1 and most of the MYB genes were found preferentially expressed in ‘MYC’ groups, indicating some of which potentially served as negative factor(s) for biosynthesis of caffeine in tea plants. The present study uncovers the characteristics of metabolite accumulation and the key regulatory network, which provide a research reference to the selection and breeding of tea varieties.

The Empoasca onukii (Hemiptera: Cicadellidae) female lays its eggs inside the epidermis of the tea plant shoots. This has led to speculation that shoot harvesting could represent a method of egg removal. To verify the validity of this hypothesis, we sought to determine which part of the shoot was used for the oviposition and how the value of the harvested shoot affects the cost of the egg removal. In this study, four tea cultivars were chosen to examine the preferences for the site of oviposition. In addition, a mathematical model was used to describe the correlation between the economic value of the selected shoot and eggs laid within the shoot. Our study revealed that the pest preferred the 3rd and 4th leaf order intervals of the shoot as the oviposition sites, and the oviposition preferences was dependent on the leaf order interval class across all tea cultivars. In addition, a significant negative exponential relationship was found between the economic value of the selected shoot and the percentage of the eggs laid within the shoot, indicating that egg removal through shoot harvesting was limited. The findings of this study could be used to better understand the role of shoot harvesting in egg removal and would provide new insights into the understanding of the incidence of this pest.

Several purple-leaf tea has been utilized around the world. Flavonoids accumulation is one of the reasons why purple-leaf tea has unique pharmacological value and flavor. Although abundant researches have focused on identification the key genes associated with flavonoids biosynthesis in purple-leaf tea cultivars, However, the accumulation pattern of flavonoids in purple-leaf tea is still worth investigation. Here, a group of local purple-leaf tea varieties (‘Baitangziyacha’, BTZY), which are derived from the natural mutant of green-leaf tea varieties (‘Baitangshancha’, BTSC), were found in China. To evaluate the available value of purple-leaf tea varieties, 11 ‘BTZY’ and 9 ‘BTSC’ varieties were used to analyze the accumulation of flavonoids by widely targeted metabolomic analyses. The results showed that 259 secondary metabolites were characterized, of which 250 metabolites were flavonoids. Principal component analysis (PCA) analysis indicated ‘BTZY’ and ‘BTSC’ varieties were not completely classified may be due to differences in the accumulation of a few metabolites. Furthermore, these results found that 6 types of anthocyanins 5 types of flavonols were significantly up-regulated in purple-leaf varieties. These metabolites potentially contributed to the unique color and flavor of purple-leaf tea. Our findings will be useful for the further breeding and processing of local purple-leaf tea varieties.