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Article|25 Jul 2022|OPEN
Potential ‘accelerator’ and ‘brake’ regulation of theanine biosynthesis in tea plant (Camellia sinensis
Jiayi Guo1 ,† , Biying Zhu1 ,† , Ying Chen1 , Shijia Lin1 , Siming Qiao1 , Fuli Ma2 , Shihua Zhang3 , Tianyuan Yang1 , Qi Chen1 , Linlin Liu1 , Zhaoliang Zhang1 , and Xiaochun Wan,1 ,
1State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, Anhui 230036, China
2College of Horticulture, Anhui Agricultural University, Hefei, Anhui 230036, China
3School of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei 430072, China
*Corresponding author. E-mail:,
Both authors contributed equally to the study.

Horticulture Research 9,
Article number: uhac169 (2022)
Views: 81

Received: 20 Jun 2022
Accepted: 20 Jul 2022
Published online: 25 Jul 2022


Dear Editor,

Theanine, one of the most important tea quality components, confers the ‘umami’ taste and anti-stress benefits of tea infusion [1]. Theanine is a unique non-proteinaceous amino acid solely accumulating to a high level in tea plants, and is primarily synthesized in the roots from glutamate (Glu) and ethylamine (EA) by theanine synthetase (CsTSI) [12]. The high EA availability was suggested to be why only tea plants can synthesize large amounts of theanine [3]. Our recent study further indicated that EA contents in the roots of various tea plant cultivars were highly correlated with the theanine contents in the roots [4]. EA is synthesized from alanine by alanine decarboxylase CsAlaDC [45]. Further experiments suggested that the CsAlaDC and CsTSI work in tandem to determine theanine biosynthesis in tea plants [4]. Interestingly, the expression of CsTSI in the roots of different tea plant cultivars was not obviously correlated with the theanine contents; while the expression of CsAlaDC was shown to be highly correlated with both EA contents and theanine contents in the roots [4]. These results indicated that the regulation of CsAlaDC expression is critical for adjusting the activity of theanine synthesis in tea plants. However, the mechanism underlying the regulation of CsAlaDC expression is largely unknown in tea plants. Uncovering the mechanism will be critical for improving theanine biosynthesis in tea plants.