NlCYP417A1 is a critical regulator of molting by governing ecdysone homeostasis in the brown planthopper.

BACKGROUND

The brown planthopper (BPH), Nilaparvata lugens, is a destructive rice pest across Asia. Suppressing insect development is enduring goals in insect pest management, underpinning the action of existing insecticides and guiding the design of new ones. Insect molting, which is tightly regulated by ecdysteroid signaling, is essential for insect growth and development. Cytochrome P450 (CYP) enzymes play critical roles in ecdysteroid biosynthesis, and identifying P450 genes involved in this process may provide new insights into insect developmental regulation and potential targets for pest control.

RESULTS

Here, we identify NlCYP417A1, a planthopper specific P450, as an essential regulator of molting and cuticle remodeling. NlCYP417A1 is predominantly expressed in the cuticle. RNA interference-mediated knockdown severely impairs ecdysis, leading to incomplete cuticle shedding, elongated body shape, and final lethality. Mechanistically, NlCYP417A1 silencing suppresses Halloween family gene expression, reducing 20-hydroxyecdysone (20E) titers and disrupting downstream 20E signaling, including ecdysone receptor (EcR)/ultraspiracle (USP), early response genes (E93, E75, E74A), HR3, and FTZ-F1. Finally, silencing NlCYP417A1 down-regulates chitinolytic enzyme genes and multiple cuticular protein genes, which provides a compelling explanation for the abnormal molting observed in the test insects.

CONCLUSION

Our study reveals an essential role of NlCYP417A1 in regulating ecdysteroid biosynthesis and nymphal molting, expanding our understanding of CYP450-mediated developmental regulation in insects. © 2026 Society of Chemical Industry.