Functional characterization of MsFE4 in the detoxification metabolism of Melanaphis sacchari to nitenpyram

Melanaphis sacchari is a highly polyphagous aphid species that inflicts substantial agricultural losses across various crops. Nitenpyram, a widely used neonicotinoid insecticide, remains a key chemical agent for aphid management. Esterases play a critical role in xenobiotic metabolism and insecticide detoxification in insects. In this study, synergist bioassays demonstrated that esterase activity significantly contributed to nitenpyram detoxification in M. sacchari, owing to triphenyl phosphate (TPP), a specific esterase inhibitor, which showed a tendency to enhance the toxicity of nitenpyram. Transcriptomic profiling and subsequent molecular characterization identified six esterase genes that are expressed throughout different developmental stages and in various tissues. Notably, MsEST2 and MsFE4 exhibited significant upregulation following exposure to nitenpyram, showing a clear concentration-dependent response. Functional validation through RNA interference confirmed that silencing of MsEST2 and MsFE4 reduced their transcript levels and consequently increased aphid mortality after nitenpyram treatment, probably supporting their essential role in nitenpyram metabolism. However, homology modeling and molecular docking revealed that only MsFE4 exhibits higher binding affinity for nitenpyram than other esterase proteins. Additionally, in vitro metabolism and fluorescent competitive binding experiments further indicated that MsFE4 exhibits noncatalytic nitenpyram sequestration capabilities. Collectively, these results demonstrated that esterase-mediated detoxification underlies nitenpyram metabolism in M. sacchari, and identifying MsFE4 as a promising molecular target for the development of novel resistance management strategies.