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

We previously reported that the general odorant-binding protein GOBP2 enhances chlorpyrifos tolerance in <i>Spodoptera litura</i> 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 <i>S. litura</i>. Fluorescence competitive binding assays indicated that GOBP2 exhibits high binding affinities to the herbicide trifluralin and the insecticides indoxacarb, chlorpyrifos, and fipronil, with <i>K</i>_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 <i>GOBP2</i> 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 <i>S. litura</i>, laying the foundation for innovative pest management strategies.