Chen Ziping, Lin Shijia, Chen Tingting, Han Mengxue, Yang Tianyuan, Wang Yan, Bao Shilai, Shen Zhougao, Wan Xiaochun, Zhang Zhaoliang
State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, China.
Anhui Promotion Center for Technology Achievements Transfer, Anhui Academy of Science and Technology, Hefei, 230031, China.
Hortic Res. 2022 Dec 2;10(2):uhac269. doi: 10.1093/hr/uhac269. eCollection 2023 Feb.
Theanine content is highly correlated with sensory quality and health benefits of tea infusion. The tender shoots of etiolated and albino tea plants contain higher theanine than the normal green tea plants and are valuable materials for high quality green tea processing. However, why these etiolated or albino tea plants can highly accumulate theanine is largely unknown. In this study, we observed an etiolated mutant (mutation in , ) that accumulated higher levels of glutamine (an analog of theanine). We therefore identified CsHO1 in tea plants and found CsHO1 is conserved in amino acid sequences and subcellular localization with its homologs in other plants. Importantly, expression in the new shoots was much lower in an etiolated tea plants 'Huangkui' and an albino tea plant 'Huangshan Baicha' than that in normal green tea plants. The expression levels of were negatively correlated with theanine contents in these green, etiolated and albino shoots. Moreover, expression levels in various organs and different time points were also negatively correlated with theanine accumulation. The was hypersensitive to high levels of theanine and accumulated more theanine under theanine feeding, and these phenotypes were rescued by the expression of in this mutant. Transient knockdown expression in the new shoots of tea plant using antisense oligonucleotides (asODN) increased theanine accumulation. Collectively, these results demonstrated CsHO1 negatively regulates theanine accumulation in tea plants, and that low expression likely contributes to the theanine accumulation in etiolated/albino tea plants.
茶氨酸含量与茶汤的感官品质和健康益处高度相关。黄化和白化茶树的嫩梢所含茶氨酸比正常绿茶树更高，是高品质绿茶加工的宝贵原料。然而，这些黄化或白化茶树为何能高度积累茶氨酸在很大程度上尚不清楚。在本研究中，我们观察到一个黄化突变体（ 、 发生突变）积累了较高水平的谷氨酰胺（茶氨酸的类似物）。因此，我们在茶树中鉴定出了CsHO1，并发现CsHO1在氨基酸序列和亚细胞定位上与其在其他植物中的同源物保守。重要的是，黄化茶树‘黄魁’和白化茶树‘黄山白茶’新梢中的 表达量远低于正常绿茶树。 基因的表达水平与这些绿色、黄化和白化嫩梢中的茶氨酸含量呈负相关。此外， 在各个器官和不同时间点的表达水平也与茶氨酸积累呈负相关。 对高水平茶氨酸高度敏感，在茶氨酸饲喂条件下积累更多茶氨酸，而该突变体中 的表达可挽救这些表型。使用反义寡核苷酸（asODN）瞬时敲低茶树新梢中的 表达可增加茶氨酸积累。总之，这些结果表明CsHO1负调控茶树中茶氨酸的积累，而低水平表达可能有助于黄化/白化茶树中茶氨酸的积累。
