Modulation of Enhanced Antioxidant Activity by Hydrogen Sulfide Antagonization of Ethylene in Tomato Fruit Ripening

Ethylene (C2H4) and hydrogen sulfide (H2S) play important physiological roles in regulating fruit ripening and senescence. The mechanism of H2S in ethylene-induced tomato fruit ripening and senescence is still unknown. Here, we show that exogenous H2S reduced the production of superoxide anion (·O2-), malondialdehyde (MDA), and H2O2 in tomato fruit. Further, additional H2S was found to induce the activities of guaiacol peroxidase, catalase, ascorbate peroxidase, and superoxide dismutase compared with C2H4 treatment alone, whereas the activities of lipoxygenase, polyphenol oxidase, and phenylalanine ammonia lyase were adversely affected. Moreover, the expression of the antioxidant-encoding genes SlAPX2, SlCAT1, SlPOD12, and SlCuZnSOD was generally up-regulated with C2H4-H2S cotreatment, compared with their expression after ethylene treatment. Thus, the present results suggest that exogenous H2S acts as a fruit-ripening regulator by antagonizing the effect of ethylene, thereby providing a potential application for H2S in the postharvest storage of fruit.