State Key Laboratory of Tea Plant Biology and Utilization, and International Joint Laboratory on Tea Chemistry and Health Effects of Ministry of Education, Anhui Agricultural University, Hefei, Anhui, China.
School of Life Science, Anhui Agricultural University, Hefei, Anhui, China.
Plant Sci. 2020 Nov;300:110632. doi: 10.1016/j.plantsci.2020.110632. Epub 2020 Aug 6.
Flavonol derivatives are a group of flavonoids benefiting human health. Their abundant presence in tea is associated with astringent taste. To date, mechanism pertaining to the biosynthesis of flavonols in tea plants remains unknown. In this study, we used bioinformatic analysis mining the tea genome and obtained three cDNAs that were annotated to encode flavonol synthases (FLS). Three cDNAs, namely CsFLSa, b, and c, were heterogenously expressed in E. coli to induce recombinant proteins, which were further used to incubate with three substrates, dihydrokampferol (DHK), dihydroquercetin (DHQ), and dihydromyricetin (DHM). The resulting data showed that three rCsFLSs preferred to catalyze (DHK). Overexpression of each cDNA in tobacco led to the increase of kampferol and the reduction of anthocyanins in flowers. Further metabolic profiling of flavan-3-ols in young tea shoots characterized that kaempferol derivatives were the most abundant, followed by quercetin and then myricetin derivatives. Taken together, these data characterized the key step committed to the biosynthesis of flavonols in tea leaves. Moreover, these data enhance understanding the metabolic accumulation relevance between flavonols and other main flavonoids such as flavan-3-ols in tea leaves.
类黄酮衍生物是一类有益于人类健康的类黄酮。它们在茶中的丰富存在与涩味有关。迄今为止，茶树中类黄酮生物合成的机制尚不清楚。在这项研究中，我们使用生物信息学分析挖掘茶叶基因组，获得了三个被注释为编码类黄酮合酶（FLS）的 cDNA。三个 cDNA，即 CsFLSa、b 和 c，在大肠杆菌中异源表达诱导重组蛋白，然后用三种底物二氢山奈酚（DHK）、二氢槲皮素（DHQ）和二氢杨梅素（DHM）进一步孵育。结果表明，三种 rCsFLSs 优先催化（DHK）。每个 cDNA 在烟草中的过表达导致花中山奈酚的增加和花青素的减少。对幼嫩茶芽中黄烷-3-醇的代谢组学分析表明，山奈酚衍生物最为丰富，其次是槲皮素，然后是杨梅素衍生物。总之，这些数据描述了茶叶中类黄酮生物合成的关键步骤。此外，这些数据增强了对茶叶中类黄酮与其他主要类黄酮（如黄烷-3-醇）之间代谢积累相关性的理解。
