Fruit ripening, the penultimate stage before senescence, is exclusively regulated by light, which signals and activates ripening-specific genes. Building on light's regulatory role in development, this review updates on signaling pathways, including phytochrome, cryptochrome, phototropins, and wavelength receptors, that are involved in gene activation during ripening. Understanding CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and ELONGATED HYPOCOTYL 5 (HY5) as the principal hub of light perception and downstream modulation for transcriptome, proteome, and metabolome activities, the synergism of hormonal influence is discussed. The precise wavelengths of light and their effects on major growth hormones, such as ethylene, abscisic acid (ABA), and auxin, are discussed in relation to the progression of ripening metabolism and the regulation of specific transcription factors. This review points out regulatory factors like ETHYLENE RESPONSE FACTOR E4 to alter auxin's promoter binding activity, allowing ethylene sensitivity. The major focus is on ethylene response factors, MADS-box genes, and bZIP proteins for the molecular regulation of ripening-induced fruit coat hydrolysis, aroma production, and respiratory burst. The genetic mutation was elucidated in the context of the RIPENING INHIBITOR (RIN) and NON-RIPENING (NOR) factors in tomato genotypes, which share similar sequences with other crops, such as strawberry. The review also highlights epigenetic control through chromatin remodeling, methylation/demethylation reactions, and histone modifications, providing further insight into the light's influence on the extra-transcriptome affair. Collectively, this review concludes that light is a major molecular switch in pathways of hormonal, genetic, and epigenetic functions, contributing to advances in postharvest preservation.
Pal et al. (Sun,) studied this question.