LAUSR

Apple exocarp was used to investigate the effect of acibenzolar-S-methyl (ASM) and dehydroepiandrosterone (DHEA) treatments on reaction oxygen species (ROS) metabolism. The results indicated that ASM enhanced the hydrogen peroxide (H2O2) content, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PDH). ASM also increased the contents of ascorbic acid (AsA), reduced glutathione (GSH) and nicotinamide ademine dinucleotidephosphate (NADPH), MdSOD and MdAPX expression, but decreased MdMDHAR and dehydroascorbate reductase (MdDHAR) expression. DHEA suppressed H2O2 accumulation and POD, APX, MDHAR, G6PDH activities, but increased SOD, CAT and GR activities compared to the control. ASM and DHEA treatments suppressed the contents of AsA, GSH and NADPH, and expression of MdSOD, MdAPX and MdMDHAR. These results suggest that DHEA treatment prevented ROS metabolism induced by ASM which showed the important role of G6PDH in maintaining redox homeostasis in apple exocarp.