Effects of salt and drought stresses on antioxidant system and RbohC and RbohF genes expression in Brassica campestris.

To investigate the effects of salt stress and PEG-6000 simulating drought stress on the active oxygen and antioxidant enzyme activities, as well as the expression level of RbohC and RbohF genes, the seedlings of two Brassica campestris, Longyou 6 and Tianyou 2, were treated with U0126 (a MAPKK inhibitor), DMTU (a H2O2 scavenger), as well as DPI and IMD (NADPH oxidase inhibitors). The results showed that under both stresses, H2O2 accumulation as well as antioxidant enzyme (SOD, CAT, APX, GR) activities and the expression of RbohC and RbohF genes increased, while O2-· accumulation decreased. The O2-· accumulation, antioxidant enzyme activity and RbohC and RbohF genes expression in both varieties all significantly decreased. Compared to seedlings with on pretreatment before salt and PEG-6000 simulating drought stress, the accumulation of H2O2 decreased in seedlings pretreated with DMTU, DPI and IMD. However, the accumulation of H2O2 increased in those pretreated with U0126. Those results indicated that the NADPH oxidase, MAP kinase cascade and H2O2 were involved in the regulation of active oxygen production and antioxidant enzyme activity, as well as the expression of RbohC and RbohF under salt stress and drought stress.