Dissection of the spatial dynamics of biosynthesis, transport, and turnover of major amino acids in tea plants (Camellia sinensis)

Abstract

High levels of free amino acids (AAs) in tea leaves are crucial for tea flavor and health function; however, the dynamic AA biosynthesis, transport, and turnover in tea plants remain elusive. Here we dissected whole tea plants for these dynamics by assessing AA profiles and transcriptomes of metabolic pathway genes in tea roots, stems, and leaves and revealing their distinctive features with regard to AA synthesis, transport, and degradation/recycling. Nitrogen assimilation dominated in the roots wherein glutamine (Gln), theanine, and arginine (Arg) were actively synthesized. Arg was transported into trunk roots and stems, together with Glu, Gln, and theanine as the major AAs in the xylem sap for long-distance root-to-leaf transport. Transcriptome analysis revealed that genes involved in Arg synthesis were highly expressed in roots, but those for Arg transport and degradation were highly expressed in stems and young leaves, respectively. CsGSIa transcripts were found in root meristem cells, root, stem and leaf vascular tissues, and leaf mesophyll where it appeared to participate in AA synthesis, transport, and recycling. Overexpression of CsGSIa in tea transgenic hairy roots and knockdown of CsGSIa in transgenic hairy roots and tea leaves produced higher and lower Gln and theanine than wild-type roots and leaves, respectively. This study provides comprehensive and new insights into AA metabolism and transport in the whole tea plant.

Acknowledgements

We thank the lab members in Zhao’s Lab at Anhui Agricultural University for assistance with tea seedling cultivation and treatment experiments and amino acid metabolite profiling. This work was supported by Natural Science Foundation of China (U23A20214), the funds from Hunan ‘Three Top’ Innovative Talents Project (2022RC1142).

Author contributions

J.Z. planned and designed the research. S.Y., M.Z., P.L., H.Z., Y.L., J.L., and A.P. performed experiments and analysed data. J.Z., A.R.F., J.H., and Z.L. wrote and revised the manuscript.

Data availability

The data of this article that support the findings of this study are available in the supplementary materials, including Tables S1-S2, Datasets S1-S9, and Tea Plant Information Archive (TPIA; http://tpia.teaplant.org), and are publicly accessible. Other materials and information will be available upon request from the corresponding author, who will be also responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors: Jian Zhao ([e-mail]; [e-mail]).

Conflict of interest statement

The authors declare no conflict of interest.

Supplementary data

Supplementary data is available at Horticulture Research online.

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