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.花青素（Anthocyanins）是一类天然着色剂，因其广泛的抗氧化、抗诱变及促健康活性而受到越来越多的关注。富含花青素的代表性茶树品种紫娟茶（Zijuan tea）的花青素合成机制已得到深入研究，但关于花青素转化与降解的分子基础仍有待阐明。本研究以紫娟茶与近缘品种云抗10号（Yunkang 10）为材料开展转录组与代谢物分析。在紫娟茶中共鉴定出4种糖基化花青素，分别为飞燕草素-3-O-半乳糖苷、矢车菊素-3-O-半乳糖苷、飞燕草素3-O-(6-O-对香豆酰基)半乳糖苷以及矢车菊素3-O-(6-O-对香豆酰基)半乳糖苷，推测糖基化修饰可能决定花青素的稳定积累。研究团队还鉴定出多个调控花青素代谢的差异表达基因与转录因子，其中显著上调的ANS、3GT、3AT、MYB及WRKY被证实参与花青素的积累与转化过程。此外，通过对比紫娟茶与紫嫣茶（Ziyan）的不同叶位组织，本研究发现调控二者花青素生物合成的关键基因存在差异，且降解基因在花青素水解过程中发挥的作用各不相同。本研究结果为茶树体内花青素平衡的分子调控机制提供了新的理论依据。