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

Abstract

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.