Abstract

Cytochrome P450 monooxygenases (CYPs) are important for plant defense, yet their role in melon resistance to powdery mildew (PM) is poorly characterized. Here, we identified 195 CYP genes in the melon genome and analyzed their genomic features. Integrated transcriptomic and metabolomic analyses of PM-resistant (J152) and susceptible (J156) lines revealed that CmCYP genes are dynamically regulated during Podosphaera xanthii ( P. xanthii ) infection and significantly enriched in phenylpropanoid and flavonoid biosynthesis pathways. In J152, a temporally coordinated expression pattern of specific CmCYP genes was associated with a strategic metabolic reprogramming: early induction of core flavonoid structural genes, followed by a shift of phenylpropanoid flux toward lignin reinforcement via sustained up‑regulation of putative ferulate 5‑hydroxylase ( F5H ) genes. This resource allocation strategy enabled J152 to maintain flavonoid levels during early infection while reinforcing lignin deposition at later stages, reflecting an intra‑pathway metabolic trade‑off. In contrast, J156 lacked such temporal coordination, resulting in early flavonoid reduction without sufficient lignin accumulation. Our findings support a model in which CmCYP -mediated resource allocation contributes to PM resistance, providing insights into defense trade-off mechanisms and potential molecular targets for melon breeding.