Haem Oxygenase 1 is a potential target for creating etiolated/albino tea plants (Camellia sinensis) with high theanine accumulation

Abstract

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 Arabidopsis etiolated mutant hy1–100 (mutation in Haem Oxygenase 1, HO1) 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, CsHO1 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 CsHO1 were negatively correlated with theanine contents in these green, etiolated and albino shoots. Moreover, CsHO1 expression levels in various organs and different time points were also negatively correlated with theanine accumulation. The hy1–100 was hypersensitive to high levels of theanine and accumulated more theanine under theanine feeding, and these phenotypes were rescued by the expression of CsHO1 in this mutant. Transient knockdown CsHO1 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 CsHO1 likely contributes to the theanine accumulation in etiolated/albino tea plants.

Acknowledgements

This work was supported by the National Key R&D Program of China (2021YFD1601101), grants from the National Natural Science Foundation of China (32072624), and Anhui Provincial Department of Human Resources and Social Security (2021LXC017). Thanks to Professors Wenbiao Shen and Yanjie Xie (College of Life Sciences, Nanjing Agricultural University, China) for providing the seeds of Arabidopsis hy1-100 mutant.

Author contributions

Z.Z., Z.C., S.B., and X.W. designed and refined the research; Z.C., S.L., T.C., and M.H. performed research; T.Y., Y.W., and Z.S. participated in the preparation of plant materials; Z.C., S.L., and T.C. analysed data; Z.C. and Z.Z. wrote the manuscript. All authors reviewed and approved the final manuscript.

Data availability

All relevant data in this study are provided in the article and its supplementary file.

Conflict of interests

The authors declare no conflict of interest.

Supplementary data

Supplementary data is available at Horticulture Research online.

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