Binding Properties of the General Odorant-Binding Protein GOBP2 to Herbicides and Insecticides in Spodoptera litura

We previously reported that the general odorant-binding protein GOBP2 enhances chlorpyrifos tolerance in Spodoptera litura by perceiving the herbicides. However, the direct interaction between GOBP2 and pesticides remains unknown. Herein, we verified the effect of the direct binding of GOBP2 to pesticides on the herbicide-induced insecticide tolerance in S. litura. Fluorescence competitive binding assays indicated that GOBP2 exhibits high binding affinities to the herbicide trifluralin and the insecticides indoxacarb, chlorpyrifos, and fipronil, with K_i values ranging from 1.95 to 13.01 μM. Moreover, Ala136 and Thr30 were determined as the key binding sites of GOBP2 to the pesticides through molecular docking and site-directed mutagenesis. Finally, the knockdown of GOBP2 significantly increased the larval susceptibility to trifluralin and three types of insecticides. Our findings provide a valuable reference for the further exploration of the molecular mechanisms underlying herbicide-induced insecticide tolerance in S. litura, laying the foundation for innovative pest management strategies.