Dong_2026_Pestic.Biochem.Physiol_216_106826

Spodoptera litura (F.) is one of the most devastating insect pests in many Asian regions. Chlorpyrifos is a typical acetylcholinesterase (AChE) inhibitor organophosphate insecticide used globally for many Lepidopterous larvae chemical control. Insect chemosensory proteins (CSPs) are understood to be a class of small, compact, and soluble proteins that are involved in different tasks, such as chemical recognition, embryo development, and innate immunity. In this study, one upregulated chemosensory gene SlCSP5 was identified in S. litura when their 5th instar larvae were exposed to chlorpyrifos. Expression profiles analysis by qRT-PCR indicated the abundant expression SlCSP5 in the integument of the 5th S. litura instar larvae. Recombinant SlCSP5 protein was subsequently obtained using an Escherichia coli BL21(DE3) expression system. Molecular docking analysis revealed that there are three key residues (Asp12, Leu16, Arg71) potentially critical for ligand interaction. The purified SlCSP5 displayed a high binding affinity to chlorpyrifos and indoxacarb, while a moderate affinity to chlorfenapyr. Silencing of SlCSP5 by dsRNA injection significantly increased the sensitivity of S. litura larvae to chlorpyrifos. These findings will provide valuable insights that SlCSP5 contributes to the tolerance of S. litura to chlorpyrifos.