Integrated Metabolomic and Transcriptomic Analysis Reveals the Molecular Regulatory Mechanism of Gamma-Aminobutyric Acid Accumulation in White Quinoa ( Willd.) in Response to Dark and Ultrasound Stress.

Gamma-aminobutyric acid (GABA) is a nonprotein amino acid, which confers stress resistance to plants. Precise mechanisms underlying GABA accumulation in quinoa () subjected to dark and ultrasonic stresses have not been elucidated. We conducted transcriptome and metabolome analyses of quinoa samples exposed to various stress treatments to reveal molecular pathways leading to GABA accumulation. Through the comprehensive integration of metabolome and transcriptome data, an association was revealed between GABA accumulation, 9 differentially expressed metabolites, and 27 differentially expressed genes. Two pathways responsible for GABA synthesis were identified, involving glutamate decarboxylase and aldehyde dehydrogenases, respectively. These enzymes regulate the enrichment of GABA in quinoa under dark and ultrasonic stress conditions. We demonstrated that under ultrasonic stress, proline and alanine increased, whereas glutamate and arginine declined. Phenolic acid, flavonoids, and alkaloid metabolites increased. These findings provide novel insights into the mechanism by which darkness and ultrasound stress enhance GABA, supporting the development of targeted synthetic biology techniques.