Nitric oxide acts downstream of hydrogen peroxide in the regulation of ascorbate and glutathione metabolism by jasmonic acid in Agropyron cristatum leaves

The relationship between hydrogen peroxide (H2O2) and nitric oxide (NO) in the regulation of ascorbate and glutathione metabolism by jasmonic acid (JA) in Agropyron cristatum leaves were studied. Results showed that JA increased the production of H2O2 and NO, the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), L-galactono-1,4-lactone dehydrogenase (GalLDH), and gamma-glutamylcysteine synthetase (gamma-ECS), as well as transcription of the respective genes and also the content of reduced ascorbate (AsA) and reduced glutathione (GSH). Above increases were suppressed by pre-treatments with H2O2 synthesis inhibitor diphenylene iodonium (DPI), H2O2 scavenger dimethylthiourea (DMTU), NO synthesis inhibitor N-G-nitro-L-Arg methyl ester (L-NAME), and NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO). Pre-treatments with DPI and DMTU reduced H2O2 and NO production. Pre-treatments with L-NAME and cPTIO reduced NO production, but did not reduce the H2O2 production induced by JA. Our results suggested that NO acted downstream of H2O2 in JA signalling in the up-regulation of ascorbate and glutathione metabolism in A. cristatum leaves.