Exogenous ?-aminobutyric acid strengthens phenylpropanoid and nitrogen metabolism to enhance the contents of flavonoids, amino acids, and the derivatives in edamame

gamma-aminobutyric acid (GABA) has been reported to improve stress resistance in plants. Nonetheless, little is known about the effects of GABA on the nutritional quality and regulatory mechanisms of edamame. Therefore, we analyzed the flavonoid and amino acid (AA) metabolism and the effects of GABA on the nutrient content of edamame seeds through physiological and metabolomic analyses. Exogenous GABA increased endogenous GABA metabolism and GABA transaminase activity and enhanced the oxoglutarate content, which entered into nitrogen metabolism and increased the activity and expression of nitrogen metabolism-related enzymes, to accumulate AAs and bioactive peptides. Meanwhile, exogenous GABA induced the metabolism of flavonoids, including total flavonoids, anthocyanins, 6 ''-o-malonyglycitin, glycitin, ononin, cyanin, and ginkgetin, by increasing the activity and expression of flavonoid biosynthetic enzymes. This is the first study to reveal that GABA effectively improves the nutritional quality of edamame through the accumulation of AAs, bioactive peptides, isoflavones, anthocy-anins, sugars, and organic acids.

Automated summary

This study reveals that GABA effectively improves the nutritional quality of edamame by accumulating amino acids, bioactive peptides, isoflavones, anthocyanins, sugars, and organic acids. Exogenous GABA increases the metabolism of endogenous GABA and enhances the activity and expression of nitrogen metabolism-related enzymes, leading to an accumulation of amino acids and bioactive peptides. Additionally, exogenous GABA induces the metabolism of flavonoids by increasing the activity and expression of flavonoid biosynthetic enzymes.