Hydrogen Sulfide Alleviates Senescence of Fresh-cut Apple by Regulating Antioxidant Defense System and Senescence-related Gene Expression

Hydrogen sulfide (H2S) has been identified as a multifunctional signaling molecule in plants. Here, we show that H2S delayed postharvest senescence of fresh-cut apples (Malus xpumila) in a dose-dependent manner. Exogenous H2S application maintained significantly higher levels of ascorbic acid, flavonoids, total phenolics, reducing sugars and soluble proteins, and lower levels of free amino acids in apple slices compared with controls. Further investigations showed that H2S significantly reduced the accumulation of superoxide radicals, hydrogen peroxide (H2O2) and malondialdehyde (MDA). Apple fruits fumigated with H2S contained significantly higher activities of ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), guaiacol peroxidase (POD) and superoxide dismutase (SOD), and lower activities of lipoxygenase (LOX), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and protease relative to controls. H2S also upregulated MdDHAR expression and downregulated the expression of MdLOX2, MdPG1, MdPPO, MdACO1, MdERS1, and MdETR1 in post-harvest apple tissue. The present study indicates that H2S was involved in delaying postharvest senescence of apples by acting as an antioxidant and by regulating senescence-related gene expression.