Exogenous γ-aminobutyric acid (GABA) enhances quality and thermotolerance of pea (Pisum sativum L.) via regulation of ascorbic acid (AsA) synthesis.

Heat stress (HS), exacerbated by global climate change, severely limits crop productivity and quality. Although γ-aminobutyric acid (GABA) can alleviate heat stress, the mechanisms by which it maintains crop quality remain largely unclear. In this study, using pea (Pisum sativum L.), we demonstrated that exogenous GABA pretreatment significantly alleviated HS-induced inhibition of photosynthesis and growth, while effectively improving nutritional and edible quality by attenuating HS-mediated cellular damage. GABA enhanced plant thermotolerance by suppressing the heat-induced reactive oxygen species (ROS) burst and alleviating subsequent oxidative damage. This protective effect was accompanied by the maintenance of the ascorbic acid (AsA) pool and a high AsA/DHA redox ratio. Transcriptional analysis revealed that GABA pretreatment significantly upregulated key genes involved in AsA biosynthesis, particularly by activating the myo-inositol pathway. Moreover, pharmacological inhibition confirmed that the protective effects of GABA on photosynthesis, ROS scavenging, and cellular integrity were dependent on AsA synthesis. Taken together, these findings reveal a novel physiological and molecular mechanism by which exogenous GABA pretreatment may enhance heat tolerance and maintain quality through activation of the inositol biosynthesis pathway and modulation of ascorbic acid (AsA) metabolism. This work provides new insights into the function of GABA as a metabolic signal integrator in regulating stress responses, and also offers potential gene targets for the genetic improvement of heat-tolerant and high-quality crops.