LmCYP3136A1: A cysteine-deficient P450 with dual roles in specific insecticide detoxification and olfaction in Locusta migratoria.

Cytochrome P450 monooxygenases (P450s) play pivotal roles in diverse insect physiology, including growth, development, xenobiotic detoxification, and olfaction. In the present study, we identified and characterized a novel P450, LmCYP3136A1, from Locusta migratoria, which lacks the conserved cysteine residue critical for canonical P450 activity in its heme-binding motif. Phylogenetic analyses indicated that LmCYP3136A1 clusters within the CYP3 clan. LmCYP3136A1 was predominantly expressed in the gastric caecum and midgut, with moderate expression in the antenna, and its transcript levels peaked in the 5th-instar nymphal stage. Its expression was significantly induced 6.22-fold by carbaryl and 9.44-time by chlorpyrifos and was also upregulated 1.51-fold by the aggregation pheromone 4-vinylanisole (4-VA) and 1.41-fold by the plant volatile 2-ethylpyrazine. RNAi-mediated silencing enhanced locust susceptibility to malathion and carbaryl, increasing mortality by 35% and 42%, respectively, but not to deltamethrin and chlorpyrifos. Furthermore, LmCYP3136A1 silencing significantly reduced electroantennogram (EAG) responses to eight volatiles, including 4-VA and decanal, with reductions of up to 83%. Molecular docking revealed ligand binding via hydrogen bonds and π-π stacking. Our findings demonstrate putative dual roles for LmCYP3136A1 in mediating specific insecticide detoxification and regulating olfactory sensitivity, expanding understanding of P450 functional diversity and structural plasticity in insects.