Jasmonic acid-induced hydrogen peroxide activates MEK1/2 in upregulating the redox states of ascorbate and glutathione in wheat leaves

We studied the relationship between hydrogen peroxide (H2O2) and MEK1/2 in jasmonic acid (JA) signaling in regulating the redox states of ascorbate (AsA) and glutathione (GSH). JA increased H2O2 production, MEK1/2 phosphorylation, the transcription levels and activities of AsA and GSH metabolic enzymes (APX, GR, DHAR, MDHAR, GalLDH and gamma-ECS), AsA and GSH contents, and the redox states of AsA and GSH (ratios of AsA/DHA and GSH/GSSG). Above increases were inhibited by applications of H2O2 synthesis inhibitor DPI and scavenger DMTU. However, applications of MEK1/2 inhibitors PD98059 and U0126 had no significant effect on JA-induced H2O2 production. Treatments with exogenous H2O2 also increased MEK1/2 phosphorylation, the transcription levels and activities of AsA and GSH metabolic enzymes, AsA and GSH contents, and the redox states of AsA and GSH. Above increases except the transcription level and activity of gamma-ECS were all suppressed by pretreatments with PD98059 and U0126. Our results suggested that JA-induced H2O2 could trigger MEK1/2 phosphorylation and activation leading to the upregulation of AsA and GSH metabolic enzymes.