Integrated Transcriptomics and Physiological Analysis Reveal the Mechanism of γ-Aminobutyric Acid Inhibiting Enzymatic Browning in Fresh-Cut Potatoes

Abstract

Enzymatic browning affects potato quality and commodity value during processing and storage. γ-Aminobutyric acid (GABA) was proved to enhance the tolerance to biological and abiotic stresses in plants. However, the mechanism by which GABA regulates enzymatic browning in potato remains largely unclear. Therewith, an integrated approach of transcriptomics and physiological analyses was utilized to investigate the mechanism of GABA-regulated browning. The findings showed that GABA significantly retarded the browning of fresh-cut potatoes. Transcriptome analysis indicated that the alteration of endogenous GABA content significantly changed the level of 3625 genes, observably enriched in phenylpropanoid biosynthesis, amino acid metabolism, and hormone signaling. Further studies showed that GABA increased the content of total phenols through changing the activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD), and the expression of genes related to phenol metabolism. Meanwhile, GABA application activated superoxide dismutase (SOD) and catalase (CAT), decreased the content of H₂O₂ and O₂⁻, and enhanced membrane integrity. Moreover, GABA increased the content of 11 amino acids including aspartic acid, threonine, glutamic acid, phenylalanine, isoleucine, cysteine, glycine, tyrosine, proline, serine, and arginine. Additionally, GABA negatively regulated the synthesis and signaling of ethylene, brassinosteroids, and gibberellin, while positively regulated the synthesis and signaling of auxin and abscisic acid at the level of transcription. Therefore, GABA can inhibit potato browning mainly through promoting the accumulation of total phenols and free amino acids and regulating reactive oxygen metabolism and hormone signaling, which provides a more comprehensive insight into the inhibitory mechanism of GABA on browning in fresh-cut potatoes.