?-Aminobutyric Acid (GABA) Mediated Stilbene Biosynthesis and Alleviated Oxidative Stress Induced by UV-C Radiation During Peanuts (arachis Hypogaea L.) Germination

Stilbenes are a series of phytoalexins produced in plants by adverse stresses featuring with various biological activities. Our previous researches showed UV-C radiation promoted stilbene biosynthesis effectively in peanut sprouts, while concurrently oxidative damages appeared. In this study, roles of ?-aminobutyric acid (GABA) in regulation of stilbene biosynthesis and oxidative stress in response to UV-C radiation were explored during peanut germination. Results showed GABA accumulation was significantly promoted by UV-C radiation through up-regulating the gene expressions and enzyme activities of GABA biosynthesis pathway. Exogenous GABA remarkably enhanced gene expressions and activities of enzymes in stilbene biosynthesis pathway to promote stilbene accumulations, while adverse results appeared in the GABA inhibited treatment, in which stilbene content decreased sharply. Besides, contents of total phenolics and flavonoids as well as the transcripts and activities of peroxidase and ascorbate peroxidase were increased by exogenous GABA, and oxidative stress-related parameters (H2O2, electrolyte leakage and malondialdehyde) decreased correspondingly. GABA also mediated nitric oxide (NO) accumulation. Overall, UV-C radiation promoted GABA biosynthesis. GABA mediated stilbene biosynthesis and increased antioxidant enzyme activities, phenolics and flavonoids accumulation to relieve oxidative stress. The mediation effect of GABA might be involved with NO.