Interaction between nitric oxide and hydrogen peroxide in postharvest tomato resistance response to Rhizopus nigricans

BACKGROUND: Nitric oxide (NO) and hydrogen peroxide (11202) are signal molecules involved in the disease response of plants, and there is a close relationship between them. To investigate the interaction of NO and H2O2 during disease resistance response in postharvest fruits and vegetables, tomato (Lycopersicon esculentum cv. Lichun) fruits were treated after harvest by vacuum infiltration with NO donor and H2O2 scavenger. RESULTS: The resistance of tomato fruits to Rhizopus nigricans Ehrenb. invasion and the activities of defensive enzymes phenylalanine ammonia-lyase, chitinase and glutathione S-transferase were enhanced by NO. However, these effects of NO on resistance were weakened by H2O2 scavenger, which showed that H2O2 was required in NO-mediated disease resistance in harvested tomato. Meanwhile, the endogenous H2O2 level was dual-regulated by NO. During the earlier period of storage the H2O2 peak was advanced by NO, but during the later period of storage, when the concentration of H2O2 was relatively higher, H2O2 accumulation was delayed by NO. The activities of superoxide dismutase, ascorbate peroxidase and catalase were involved in this regulation. CONCLUSION: The results imply that application of exogenous NO can enhance the disease resistance of postharvest tomato; NO may interact with H2O2 and exert its effect by modulating the endogenous H2O2 level. This result is useful for the further investigation and application of NO in postharvest disease control. (C) 2008 Society of Chemical Industry