Zhang Gaoyang, Yang Jihong, Cui Dandan, Zhao Dandan, Benedito Vagner Augusto, Zhao Jian
State Key Laboratory of Tea Plant Biology and Utilization, College of Tea and Food Science and Technology, Anhui Agricultural University, Hefei 230036, China.
Division of Plant and Soil Sciences, West Virginia University, 3425 Agricultural Sciences Building, Morgantown, WV 26506-6108, USA.
Food Res Int. 2020 Nov;137:109677. doi: 10.1016/j.foodres.2020.109677. Epub 2020 Sep 17.
Plucked tea leaves can be processed into black tea (Camellia sinensis), which is rich in health-promoting molecules, including flavonoid antioxidants. During black tea processing, theaflavins (TFs) and thearubigins (TRs) are generated via the successive oxidation of catechins by endogenous polyphenol oxidase (PPO)- or peroxidase (POD)-mediated reactions. This process must be well controlled to achieve the proper TF/TR ratio, which is an important quality parameter of the tea beverage. However, little is known about the POD/PPO catalyzed TF formation process at the molecular genetic level. Here, we identified and characterized the POD genes responsible for TF production in tea. Genome-wide analysis of POD/PPO family genes, metabolite profiling, and expression analysis of PPO/POD genes in tea leaves enabled us to select several PPO/POD genes potentially involved in TF production. Differential gene expression in plant tissues and enzyme activity in several tea varieties traditionally used for processing of various beverage types indicate that black tea processing primarily depends on PPO/POD activity. Among these POD/PPO genes, the POD CsGPX3 is involved in the generation of TFs during black tea processing. The capacity of PPO/POD-catalysed TF production is potentially used for controlling catechin oxidation during black tea processing and could be used to create molecular markers for breeding of tea plant varieties suitable for the production of high-quality black tea beverages.
采摘的茶叶可以加工成红茶（茶树），红茶富含多种对健康有益的分子，包括类黄酮抗氧化剂。在红茶加工过程中，儿茶素通过内源性多酚氧化酶（PPO）或过氧化物酶（POD）介导的反应连续氧化生成茶黄素（TFs）和茶红素（TRs）。这个过程必须得到很好的控制，以实现合适的TF/TR比例，这是茶饮料的一个重要质量参数。然而，在分子遗传水平上，关于POD/PPO催化TF形成过程的了解还很少。在这里，我们鉴定并表征了茶叶中负责TF产生的POD基因。通过对POD/PPO家族基因进行全基因组分析、代谢物谱分析以及对茶叶中PPO/POD基因的表达分析，我们筛选出了几个可能参与TF产生的PPO/POD基因。对传统上用于加工各种茶饮料的几个茶树品种的植物组织中基因差异表达和酶活性分析表明，红茶加工主要依赖于PPO/POD活性。在这些POD/PPO基因中，POD CsGPX3参与了红茶加工过程中TFs的生成。PPO/POD催化TF产生的能力有可能用于控制红茶加工过程中儿茶素的氧化，并且可以用于创建分子标记，以培育适合生产高品质红茶饮料的茶树品种。
