Resistance characterization and potential resistance mechanism of cyromazine, a moulting disruptor, to Drosophila melanogaster.

BACKGROUND

Moulting is a crucial process in the growth and development of insects and is also a key focus in the development of insecticides. Cyromazine, a moulting disruptor, is widely used to control dipteran pests, yet its mechanism of action and the genetic basis of resistance remain unclear. This study aimed to systematically investigate the inheritance pattern, potential resistance mechanisms, and associated fitness costs by developing a cyromazine-resistant Drosophila melanogaster strain through continuous laboratory selection.

RESULTS

After long-term directional selection, we successfully established the cyromazine-resistance (Cyr-R) strain with a resistance ratio of 50.19-fold. Genetic analysis revealed that the resistance trait is autosomal, incompletely dominance and polygenic. The Cyr-R strain exhibited only a 4.64-fold low level cross-resistance to chlorfluazuron, with no cross-resistance to other tested insect growth regulators. Notably, the Cyr-R strain exhibited substantial fitness costs: the fecundity and egg hatch rate, pupation rate and eclosion rate had significantly reduced. RNA-sequencing and enzyme activity assays combined with synergism bioassays demonstrated that the cytochrome P450 enzymes play crucial roles in resistance to cyromazine. Quantitative real-time polymerase chain reaction (qRT-PCR) and molecular docking suggested the possibility that the binding affinities between cyromazine and four cytochrome P450 monooxygenase (P450) proteins.

CONCLUSION

Our study has provided comprehensive characterizations of cyromazine resistance in D. melanogaster, highlighting its slow resistance development, limited cross-resistance, and fitness costs. These findings offer valuable insights for resistance management strategies and further mechanistic studies. © 2026 Society of Chemical Industry.