Alleviation of chilling-induced oxidative damage by salicylic acid pretreatment and related gene expression in eggplant seedlings

The effects of salicylic acid (SA) pretreatment on ascorbate-glutathione (GSH) cycle under chilling stress in eggplant seedlings were investigated. Salicylic acid pretreatment improved chilling resistance of eggplant seedlings with maximum efficiency at a concentration of 0.3%. The chilling injury index was decreased by 36.9% as compared to that of the control after 0.3% SA pretreatment. Under chilling stress, seedlings pretreated with SA displayed lower hydrogen peroxide (H2O2) content and higher ascorbate peroxidase (APX) activity than the untreated seedlings. Pretreatment with SA increased ascorbic acid and GSH content. Salicylic acid (0.3%) pretreatment enhanced the dehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) activity but not glutathione reductase (GR). Pretreatment with SA also enhanced the induced expression of stress-responsive genes under chilling stress. The highest transcript levels of GST1, GST2, GPX1, GPX2, GSH, MDHAR, GR and DHAR upon pretreatment with SA (0.3%) were 6.21, 6.24, 7.76, 5.99, 6.54, 6.44, 2.86 and 2.15 folds, respectively as compared to non-SA-treated seedlings. Taken together, SA pre-treatment could effectively protect eggplant seedlings from oxidative damage of chilling stress through enhancing antioxidant enzymes activities and related gene expression.