Exogenous GABA improves tomato fruit quality by contributing to regulation of the metabolism of amino acids, organic acids and sugars

To better explore the impact of exogenous GABA on tomato fruit quality, we explored the effects of GABA (20 mM) on tomato fruits at different developmental stages. The results showed that spraying GABA 3 days before harvest improved the quality of fruits, primarily in terms of amino acid, organic acid, and soluble sugar content. Transcriptome and metabolome data indicated that exogenous GABA enters cells and mitochondria through GABA transporters, thereby simulating endogenous GABA metabolism and enhancing the activity of genes related to amino acids and organic acids metabolism, and elevating the levels of amino acids and organic acids. Moreover, the application of exogenous GABA promoted the contents of glucose, fructose, and sucrose by affecting the expression of genes related to sugar metabolism. It was found that the mechanism of exogenous GABA in increasing fruit sugar content involved promoting sucrose synthesis, partially inhibiting glycolysis, and increasing the content of trehalose 6-phosphate. This study also provides a new model for the mechanism through which exogenous GABA affects tomato quality.