Melatonin and Fruit Ripening Physiology: Crosstalk with Ethylene, Nitric Oxide, Hydrogen Peroxide and Hydrogen Sulphide

Ripening of fruit is a complex physiological process comprising a sequence of events that precipitates the signaling molecules, especially hydrogen peroxide (H2O2), ethylene, melatonin, nitric oxide (NO), auxin, hydrogen sulfide (H2S), and brassinosteroids at different levels of gene and protein expression to initiate activation and/or deactivation of various signaling pathways that ultimately lead to the ripening of the fruit. Although ethylene has been documented as a potent molecule capable of regulating fruit ripening, molecules such as phytomelatonin, NO, H2O2, and H2S have the potential of regulating fruit ripening. However, the interaction of ethylene and these new emerging signaling molecules particularly phytomelatonin, NO, H2O2, and H2S is not fully understood. Therefore, harnessing the phytohormonal functions of phytomelatonin in fruit ripening physiology via crosstalk with ethylene and NO as well as H2O2 and H2S is of biological importance in revealing the free radical scavenging role of phytomelatonin. In this chapter, the interaction of melatonin in fruit ripening in an ethylene-NO- H2O2-H2S -dependent manner via the various signaling pathways will be highlighted and presented.