GABA Enhances Thermotolerance of Seeds Germination by Attenuating the ROS Damage in Arabidopsis

Seeds germination is strictly controlled by environment factor such as high temperature(HT)through altering the balance between gibberellin acid(GA)and abscisic acid(ABA).Gama-aminobutyric acid(GABA)is a small molecule with four-carbon amino acid,which plays a crucial role during plant physiological process associated with pollination,wounding or abiotic stress,but its role in seeds germination under HT remains elusive.In this study we found that HT induced the overaccumulation of ROS,mainly H_(2)O_(2) and O_(2)^(-),to suppress seeds germination,meanwhile,HT also activated the enzyme activity of GAD for the rapid accumulation of GABA,hinting the regulatory function of GABA in con-trolling seeds germination against HT stress.Applying GABA directly attenuated HT-induced ROS accumulation,upregulated GA biosynthesis and downregulated ABA biosynthesis,ultimately enhanced seeds germination.Consistently,genetic analysis using the gad1/2 mutant defective in GABA biosynthesis,or pop2-5 mutant with high endogenous GABA content supported the potential function of GABA in improving seeds germination tolerance to HT through scavenging ROS overaccumulation.Based on these data,we propose that GABA acts as a novel signal to enhance thermotolerance of seeds germination through alleviating the ROS damage to seeds viability.