Both AAT and ADH2 are involved in
the biosynthetic pathway leading to esters (such as hexanal) formation.
Synthesis of the volatiles that are up-regulated during
ripening is dependent upon ethylene, as there are no ripeningassociated
increases in the ethylene-insensitive Nr mutant (Zhu
et al., 2005; Klee and Giovannoni, 2011). Ethylene also affects the
essential enzymes involved in the volatile biosynthetic pathways to
influence the level of volatiles, such as lipoxygenase (LOX), alcohol
dehydrogenase (ADH), and alcohol acyltransferase (AAT)
(Zhu et al., 2005). Melatonin treatment up-regulated ADH2 and
AAT gene expression (Fig. 6B) and influenced ethylene biosynthesis,
ethylene perception, and ethylene signalling. Therefore, melatonin
may have a role in ethylene biosynthesis and signalling to
indirectly influence the level of volatiles.