Metabolites and Transcriptional Profiling Analysis Reveal the Molecular Mechanisms of the Anthocyanin Metabolism in the “Zijuan” Tea Plant (Camellia sinensis var. assamica)

Anthocyanins are natural colorants that have attracted increasing attention because of their extensive range of antioxidant, antimutagenic, and health-promoting properties. The mechanism of anthocyanin synthesis has been studied in "Zijuan" tea, a representative anthocyanin-rich tea plant. However, the molecular basis underlying the transformation and degradation of anthocyanins is less-thoroughly understood. In this study, we compare "Zijuan" with a similar variety, "Yunkang 10", for transcriptome and metabolite analysis. In total, four glycosylated anthocyanins were identified in "Zijuan", including delphinidin-3-O-galactoside, cyanidin-3-O-galactoside, delphinidin 3-O-(6-O-p-coumaroyl) galactoside, and cyanidin 3-O-(6-O-p-coumaroyl) galactoside, and the glycosyl might determine the stable accumulation of anthocyanins. Several differentially expressed genes and transcription factors regulating the anthocyanin metabolism were identified, in which the significantly upregulated ANS, 3GT, 3AT, MYB, and WRKY were determined to be responsible for increasing and transforming anthocyanins. Moreover, by comparing the different positions of leaves in "Zijuan" and "Ziyan", we found that the pivotal genes regulating the biosynthesis of anthocyanins in "Zijuan" and "Ziyan" were different, and the degradation genes played different roles in the hydrolyzation of anthocyanins. These results provide further information on the molecular regulation of anthocyanin balance in tea plants.