Heterologous Expression of CsAlaDC Enhances Thermotolerance through a Functional Ethylamine-Theanine-GABA Metabolic Network in Tomato.

Authors

Qianying Wang, Jingbo Yu, Peng Mao, Shibei Ge, Peixian Bai, Golam Jalal Ahammed, Zhengzhen Li, Fengshui Yang, Dongmiao Zhai, Kai Shi, Liyuan Wang, Xin Li

Published in

Plant physiology. Jul 27, 2026. Epub Jul 27, 2026.

Abstract

Theanine, a tea-enriched non-protein amino acid, plays key roles in plant metabolism and stress adaptation. To test whether theanine biosynthesis can be reconstructed in a non-tea crop and whether this metabolic network contributes to stress tolerance, we heterologously expressed the tea alanine decarboxylase gene CsAlaDC in tomato (Solanum lycopersicum cv. Micro-Tom). The resulting OE-CsAlaDC lines accumulated ethylamine and synthesized theanine without introducing a tea theanine synthase gene, demonstrating that endogenous tomato glutamine synthetase supports theanine formation. Transgenic plants exhibited distinct morphological changes, including dwarfism and dark-green leaves, while their fruits showed accelerated development, elevated levels of theanine and GABA, and improved quality-related traits such as enhanced lycopene accumulation. Under heat stress, OE-CsAlaDC plants maintained higher photosystem II efficiency, reduced membrane damage and reactive oxygen species accumulation, and stronger antioxidant enzyme activities than wild-type plants. Exogenous theanine further enhanced thermotolerance, promoted SlGAD1/2 expression, and increased GABA accumulation, whereas silencing SlGAD1 and SlGAD2 markedly diminished the protective effect of theanine. Exogenous ethylamine also conferred partial heat protection, but theanine showed a stronger association with GAD-dependent GABA biosynthesis. Collectively, these findings demonstrate that heterologous expression of CsAlaDC establishes a functional ethylamine-theanine metabolic branch in tomato and enhances thermotolerance through coordination with the GABA metabolic network, offering a promising strategy to improve both stress resilience and nutritional quality in crops.

PMID:
42507981
Bibliographic data and abstract were imported from PubMed on 28 Jul 2026.

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