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

Ethylene (C ₂ H ₄ ) and hydrogen sulfide (H ₂ S) play important physiological roles in regulating fruit ripening and senescence. The mechanism of H ₂ S in ethylene-induced tomato fruit ripening and senescence is still unknown. Here, we show that exogenous H ₂ S reduced the production of superoxide anion (·O ₂ ^- ), malondialdehyde (MDA), and H ₂ O ₂ in tomato fruit. Further, additional H ₂ S was found to induce the activities of guaiacol peroxidase, catalase, ascorbate peroxidase, and superoxide dismutase compared with C ₂ H ₄ 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 C ₂ H ₄ -H ₂ S cotreatment, compared with their expression after ethylene treatment. Thus, the present results suggest that exogenous H ₂ S acts as a fruit-ripening regulator by antagonizing the effect of ethylene, thereby providing a potential application for H ₂ S in the postharvest storage of fruit.