Amelioration of cold-induced oxidative stress by exogenous 24-epibrassinolide treatment in grapevine seedlings: Toward regulating the ascorbate-glutathione cycle

Ascorbate-glutathione (AsA-GSH) cycle plays a key role in tolerance of plant under biotic or abiotic stress. However, little is known regarding the role of brassinolide in AsA-GSH cycle in grape under chilling stress. In this study, a wine grape cultivar, Cabernet Sauvignon (Vitis vinifera), was subjected to chilling stress for different time points after treated by 24-Epibrassinolide (EBR). The result showed EBR plays a positive role in amelioration of leaf morphology and root growth under chilling stress. In terms of physiological aspect, EBR treatment reduce the O2− and H2O2 contents than that in the control. This is primarily related to the improved antioxidant system and the regulation of EBR to AsA-GSH cycle. There was an obvious increase in superoxide dismutase (SOD) activities in EBR treatment compared with in the control, and similar result also was observed in level of AsA, and AsA/DHA. Alleviation of EBR to chilling-stressed injury was also reflected in glutathione (GSH) and GSH/GSSG, as high levels of these parameters were observed in EBR treatment. Furthermore, ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbic acid reductase (DHAR) and monodehydroascorbate reductase (MDHAR) also showed elevated activities in the EBR treatment. Interestingly, the regulation of EBR to these components in AsA-GSH cycle showed a difference in time course, suggesting that the cycle might be affected by EBR at earlier and middle term of chilling stress. Our work will provide the information for understanding the role of EBR in AsA-GSH cycle.