The CmPIF8-CmDof13-mediated lipoxygenase pathway modulates red light-induced ester biosynthesis in oriental melon

Light quality influences the flavor of oriental melon (Cucumis melo var. makuwa Makino) fruit, and aroma volatiles are important determinants of flavor quality. Here, we found red light (RL) enhances the total volatile compounds in melon fruit, especially acetate esters, by activating the expression of the key lipoxygenase (LOX) pathway genes CmLOX18 and CmAAT1. The RL-inducible transcription factor CmDof13 was identified as a positive regulator of CmLOX18 and CmAAT1 in melon fruit. We also showed that total volatile compounds, esters, and ethyl acetate significantly decreased in the Cmdof13 knockout mutant relative to wild-type melon fruit. Moreover, PHYTOCHROME-INTERACTING FACTOR 8 (PIF8), which is transcriptionally downregulated by RL, inhibited CmDof13 transcription. After transient CmPIF8 overexpression in melon fruit, several ester compounds decreased. Moreover, CmPIF8 interacted with CmDof13 to regulate RL-induced ester biosynthesis. Overall, this study reveals that the CmPIF8-CmDof13-LOX pathway modulates RL-induced ester biosynthesis in oriental melon, illustrates the regulatory pathways underlying the impact of light quality on flavor quality, and provides a basis for the high-quality cultivation of oriental melon fruit under low light in greenhouse cultivation.