Hydrogen sulfide (H₂S), the third gasotransmitter, has positive roles in animals and plants. Mitochondria are the source and the target of H₂S and the regulatory hub in metabolism, stress, and disease. Mitochondrial bioenergetics is a vital process that produces ATP and provides energy to support the physiological and biochemical processes. H₂S regulates mitochondrial bioenergetic functions and mitochondrial oxidative phosphorylation. The article summarizes the recent knowledge of the chemical and biological characteristics, the mitochondrial biosynthesis of H₂S, and the regulatory effects of H₂S on the tricarboxylic acid cycle and the mitochondrial respiratory chain complexes. The roles of H₂S on the tricarboxylic acid cycle and mitochondrial respiratory complexes in mammals have been widely studied. The biological function of H₂S is now a hot topic in plants. Mitochondria are also vital organelles regulating plant processes. The regulation of H₂S in plant mitochondrial functions is gaining more and more attention. This paper mainly summarizes the current knowledge on the regulatory effects of H₂S on the tricarboxylic acid cycle (TCA) and the mitochondrial respiratory chain. A study of the roles of H₂S in mitochondrial respiration in plants to elucidate the botanical function of H₂S in plants would be highly desirable.

Both nitric oxide (NO) and hydrogen sulfide (H₂S) have been shown to have positive effects on the maintenance of fruit quality during storage; however, the mechanisms by which NO regulates the endogenous H₂S metabolism remain unknown. In this experiment, peaches were immersed in solutions of NO, potassium 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO, as an NO scavenger), N-nitro-l-arginine methyl ester (l-NAME, as an inhibitor of nitric oxide synthase (NOS)-like activity), and sodium tungstate (as an inhibitor of nitrate reductase), and the resulting changes in the H₂S metabolism of peaches were studied. The results showed that exogenous NO reduced the contents of endogenous H₂S, Cys, and sulfite; decreased the activities of l-/d-cysteine desulfhydrase (l-/d-CD), O-acetylserine (thiol)lyase (OAS-TL), and sulfite reductase (SiR); and increased the activity of β-cyanoalanine synthase (β-CAS). Both c-PTIO and sodium tungstate had similar roles in increasing the H₂S content by sustaining the activities of l-/d-CDs, OAS-TL, and SiR. l-NAME increased the H₂S content, mainly by maintaining the d-CD activity. The results suggest that NO, c-PTIO, l-NAME, and sodium tungstate differently regulate the H₂S metabolism of peaches during storage.

Postharvest losses of grape berries caused by the pathogenic fungi Botrytis cinerea and Alternaria alternata have been widely reported, and nitric oxide (NO) as a plant signaling molecule to control postharvest diseases has recently become an active research topic. This study aimed to investigate the regulatory effect of NO on the interaction between grape berries and fungi. During interactions between grape berries and pathogenic fungi, treatment with 10 mM sodium nitroprusside (SNP, an NO donor) delayed the decline of the physiological quality of the grape berries and had positive effects on the weight loss rate, firmness, and respiration intensity. SNP treatment increased the activities of superoxide dismutase (SOD) and polyphenol oxidase (PPO) and inhibited the activities of peroxidase (POD) and catalase (CAT) of grape berries during the resistance to fungal pathogen infection. In addition, the increase in browning degree and the accumulation of hydrogen peroxide were inhibited by SNP treatment. In the phenylpropane metabolic pathway, the activities of phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumaric acid coenzyme A ligase (4CL) were increased during the activation of grape berries during the resistance to pathogen infection by SNP, and the intermediate metabolites lignin, flavonoids, and total phenols were accumulated. In addition, SNP treatment had a regulatory effect on the gene expression levels of SOD, POD, PPO, PAL, and 4CL. These results suggested that SNP treatment was effective for the preservation and disease reduction of grape berries.