Recent advancements in the mechanism of nitric oxide signaling associated with hydrogen sulfide and melatonin crosstalk during ethylene-induced fruit ripening in plants.

The current review focuses on the significant role of nitric oxide (NO) in modulating ethylene-induced fruit ripening responses in plants. In this context, hydrogen sulfide (H2S) and melatonin mediated crosstalk mechanisms have been discussed with recent updates. Physiological and biochemical events associated with climacteric fruit ripening involves a plethora of effects mediated by these biomolecules. In the last few years of progress in fruit ripening physiology, the involvement of hydrogen sulfide in relation to NO remains as a nascent field of research. The importance of nitric oxide as a freely diffusible and membrane permeable biomolecule leads to its applications in post-harvest fruit storage. The process of field to market transition of edible fruits involves various intermediate stages of post-harvest storage and transport. Fruits harvested in the pre-climacteric stage are intended to be stored and transported for longer durations. However, this does not confer proper development of aroma and flavor in the post-harvest stages. Nitric oxide and ethylene crosstalk is mediated by hydrogen sulfide and melatonin activity which regulate various metabolic pathways associated with fruit ripening. A surge in the reactive nitrogen species (RNS), sugar metabolism, and plastid biogenesis are the plausible effects of NO-ethylene crosstalk. NO-mediated regulations of carbon metabolism and phytohormone levels are essential components of fruit ripening process. Melatonin by the virtue of its functional group possesses strong anti-oxidative properties. Recent updates suggest crosstalk mechanisms associated with melatonin-ethylene and nitric oxide in plants. The present review briefly summarizes the current understandings of fruit ripening physiology manifested by the effects of NO, H2S and melatonin signaling. The agri-horticultural applications of exogenous NO/H2S donors and melatonin treatment impose major benefits for delaying postharvest fruit senescence.