Transcription factor CsHSFB2c suppresses CsTS1 and CsGS1 expression to reduce theanine biosynthesis in tea plants under heat stress

doi:10.1016/j.jia.2025.12.027

Journal of Integrative Agriculture

2026, Vol. 25

Issue (3): 1009-1019 DOI: 10.1016/j.jia.2025.12.027

Horticulture

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Transcription factor CsHSFB2c suppresses CsTS1 and CsGS1 expression to reduce theanine biosynthesis in tea plants under heat stress

Qihong Zou¹, Bokun Zhou², Yilan Hu², Ping Li², Qi Zhao², Hu Tang¹, Yujie Jiao¹, Xinzhuan Yao¹, Lin Chen², Litang Lü^{1, 2#}

¹College of Tea Science, Institute of Plant Health & Medicine, Guizhou University, Guiyang 550025, China

²The Key Laboratory of Plant Resources Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Science, Guizhou University, Guiyang 550025, China

Highlights
● Heat stress led to the unique accumulation patterns of theanine and catechins in tea plants: Theanine content decreased significantly with the increasing temperature (peaking at 20°C), while catechins levels increased with increasing temperature (peaking at 30°C).
● RNA-seq identified a class B heat shock transcription factor CsHSFB2c, whose expression was negatively correlated with theanine content.
● CsHSFB2c directly binds to the promoters of CsTS1 and CsGS1 and inhibits their transcription, thereby reducing theanine biosynthesis.

Abstract
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摘要

高温胁迫会降低茶树体内的茶氨酸含量，但其分子机制尚不明确。本研究通过设置温度梯度处理（20°C、25°C、30°C、35°C），旨在揭示高温胁迫对茶氨酸生物合成与积累的影响。研究发现，高温胁迫引发代谢重编程，其特征为茶氨酸含量降低而儿茶素含量升高。此外，高温胁迫上调了B类热休克转录因子基因CsHSFB2c的表达，同时显著抑制了茶氨酸生物合成关键基因CsTS1和CsGS1的转录。功能研究表明，沉默CsHSFB2c可提高茶氨酸含量，而过量表达该基因则显著降低茶氨酸水平。与上述结果一致，沉默CsHSFB2c会上调CsTS1和CsGS1的表达，而过表达CsHSFB2c则导致这两个基因的表达下调。酵母单杂交（Y1H）和双荧光素酶报告基因（Dual-LUC）实验表明，CsHSFB2c可直接结合CsTS1和CsGS1的启动子区域并抑制其表达。这些结果证明，CsHSFB2c通过直接抑制CsTS1和CsGS1的表达，介导了高温诱导的茶氨酸生物合成抑制。本研究为通过分子育种手段提高茶树抗热性及品质提供了理论依据。

Abstract

Heat stress reduces theanine content in tea plants, but the underlying molecular mechanism remains unclear. In this study, a temperature gradient treatment (20°C, 25°C, 30°C, and 35°C) was performed to unveil the effect of heat stress on biosynthesis and accumulation of theanine. We found that heat stress induced metabolic changes, characterized by decreased theanine content and increased catechin levels. In addition, heat stress up-regulated the expression of the class B heat shock transcription factor gene CsHSFB2c, while significantly suppressing the transcription of key theanine biosynthetic genes CsTS1 and CsGS1. Functional studies showed that silencing CsHSFB2c increased theanine content, while its overexpression significantly decreased theanine levels. Consistent with these changes, silencing CsHSFB2c upregulated the expression of CsTS1 and CsGS1, while overexpression of CsHSFB2c downregulated their expression. Yeast one-hybrid (Y1H) and dual-luciferase reporter gene (Dual-LUC) assays showed that CsHSFB2c directly binds to the promoters of CsTS1 and CsGS1 and inhibits their expression. These results demonstrate that CsHSFB2c mediates heat-induced suppression of theanine biosynthesis by directly inhibiting the expression of CsTS1 and CsGS1. This study provides a theoretical basis for improving the heat resistance and quality of tea plants via molecular breeding.

Keywords: tea plant high temperature HSF glutamine synthetase theanine synthetase

Received: 15 December 2024 Accepted: 16 December 2025 Online: 18 December 2025

Fund: This work was supported by the Major Project of Guizhou Provincial Science and Technology Program, China ([2024]027), the High-Level Innovative Talents Project of Guizhou Province, China (GCC[2023]014), the Guizhou Provincial Tea Industry Technology System, China (GZCYCYJSTX-03), and the Science and Technology Project of China Huaneng Group (HNKJ2022-H135).

About author: #Correspondence Litang Lü, E-mail: ltlv@gzu.edu.cn

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Qihong Zou, Bokun Zhou, Yilan Hu, Ping Li, Qi Zhao, Hu Tang, Yujie Jiao, Xinzhuan Yao, Lin Chen, Litang Lü. 2026. Transcription factor CsHSFB2c suppresses CsTS1 and CsGS1 expression to reduce theanine biosynthesis in tea plants under heat stress. Journal of Integrative Agriculture, 25(3): 1009-1019.

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