The R2R3-MYB transcription factor CsMYB42 regulates theanine biosynthesis in albino tea leaves

Nianci Xie; Xiangxiang Huang; Jiaxin Zhou; Xiaofeng Song; Junming Lin; Meihong Yan; Mingzhi Zhu; Juan Li; Kunbo Wang

doi:10.1016/j.plantsci.2023.111850

The R2R3-MYB transcription factor CsMYB42 regulates theanine biosynthesis in albino tea leaves

Plant Sci. 2023 Nov:336:111850. doi: 10.1016/j.plantsci.2023.111850. Epub 2023 Aug 28.

Authors

Nianci Xie¹, Xiangxiang Huang¹, Jiaxin Zhou¹, Xiaofeng Song¹, Junming Lin¹, Meihong Yan¹, Mingzhi Zhu², Juan Li³, Kunbo Wang⁴

Affiliations

¹ National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients & Co-Innovation Center of Education Ministry for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha 410128, China; Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha 410128, China.
² National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients & Co-Innovation Center of Education Ministry for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha 410128, China; Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha 410128, China. Electronic address: mzzhucn@hotmail.com.
³ National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients & Co-Innovation Center of Education Ministry for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha 410128, China; Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha 410128, China. Electronic address: xixi_lj@126.com.
⁴ National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients & Co-Innovation Center of Education Ministry for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha 410128, China; Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha 410128, China; Key Laboratory for Evaluation and Utilization of Gene Resources of Horticultural Crops, Ministry of Agriculture and Rural Affairs of China, Hunan Agricultural University, Changsha 410128, China. Electronic address: wkboo163@163.com.

PMID: 37648117
DOI: 10.1016/j.plantsci.2023.111850

Abstract

Theanine is a unique secondary metabolite in tea plants and contributes to the umami taste and health benefits of tea. However, theanine biosynthesis in tea plants is not fully understood, and its mechanism of transcriptional regulation remains poorly reported. Theanine content was significantly correlated with the expression of theanine biosynthesis-related gene CsGS1c and transcription factor CsMYB42 in different leaf positions and picking times, but there was no significant correlation in different tissues of albino tea plant 'Anjibaicha'. This suggests that CsMYB42 may regulate CsGS1c to synthesize theanine in albino tea leaves, and the regulation is tissue specific. CsMYB42 is a nuclear-localized R2R3-MYB transcription factor gene with transcriptional activation activity. Yeast one-hybrid assay and electrophoretic mobility shift assay confirmed the direct binding of CsMYB42 to the promoter of CsGS1c. Luciferase assay showed that CsMYB42 activates the CsGS1c expression. Furthermore, the inhibition of CsMYB42 using an antisense oligonucleotide in tea leaves decreased CsGS1c expression and theanine content. These results indicate that CsMYB42 plays a crucial role in activating the expression of CsGS1c and may be involved in the biosynthesis of theanine in albino tea leaves. This study provides fresh insights into the tissue-specific regulation of theanine biosynthesis, which laid a foundation for breeding high-theanine tea plants.

Keywords: Camellia sinensis; Glutamine synthetase; MYB; Theanine biosynthesis.