Tea Research Institute, Yunnan Academy of Agricultural Sciences, Yunnan Provincial Key Laboratory of Tea Science, 2 Jingnan Road, Menghai, Yunnan, 666201, China.
Plant Sci. 2021 Oct;311:110997. doi: 10.1016/j.plantsci.2021.110997. Epub 2021 Jul 23.
Yunnan Province has a very wide diversity of tea germplasm resources. A variety of special tea germplasms with outstanding traits have been discovered, including tea germplasms with high anthocyanin content and low caffeine content. Albino tea cultivars generally have higher contents of theanine that contribute to the umami taste, and the quality of tea brewed from it is higher. The catechin index (CI), the ratio of dihydroxylated catechins (DIC) to trihydroxylated catechins (TRIC), is a crucial index of suitability for processing tea. In this study, the albino tea plant Menghai Huangye (MHHY) with yellow leaves was identified. Analysis of the biochemical components revealed that MHHY was enriched in theanine and the total catechins (TC) were lower than Yunkang 10 (YK10). In addition, the CI value of MHHY was extremely significantly higher than that of YK10. Metabolic profile of catechins and the related gene expression profile analysis found that the coordinated expression of the key branch genes F3'H and F3'5'Ha for the synthesis of DIC and TRIC in tea plant was closely related to the high CI and low TC of MHHY. Further analysis of the F3'H promoter showed that a 284-bp deletion mutation was present in the F3'H promoter of MHHY, containing the binding sites of the transcriptional repressor MYB4 involved in flavonoid metabolism, which might be an important reason for the up-regulated expression of F3'H in MHHY. Overall, this study provides a theoretical basis for understanding the characteristics of albino tea germplasm resources and efficiently utilizing high-CI tea germplasm resources.
云南省拥有非常丰富的茶树种质资源。已发现多种具有突出特性的特种茶树种质资源，包括高花青素含量、低咖啡因含量的茶树种质资源。白化茶树品种一般含有更高的茶氨酸，有助于增加鲜味，用其冲泡的茶叶品质更高。儿茶素指数（CI），即二羟基儿茶素（DIC）与三羟基儿茶素（TRIC）的比值，是茶叶加工适宜性的关键指标。本研究鉴定了黄叶白化茶树品种勐海黄叶（MHHY）。生化成分分析表明，MHHY 富含茶氨酸，总儿茶素（TC）低于云抗 10 号（YK10）。此外，MHHY 的 CI 值极显著高于 YK10。儿茶素代谢谱和相关基因表达谱分析发现，茶树中 DIC 和 TRIC 合成关键分支基因 F3'H 和 F3'5'Ha 的协调表达与 MHHY 高 CI 和低 TC 密切相关。进一步分析 F3'H 启动子发现，MHHY 的 F3'H 启动子存在 284bp 的缺失突变，包含参与类黄酮代谢的转录抑制因子 MYB4 的结合位点，这可能是 MHHY 中 F3'H 上调表达的重要原因。总体而言，本研究为了解白化茶树种质资源的特点和高效利用高 CI 茶树种质资源提供了理论依据。
