Interactions of two odorant-binding proteins influence insect chemoreception

It is well known that the odorant-binding proteins (OBPs) play crucial roles in insect olfactory detection. To explore if interactions of OBPs affect olfactory coding in the rice leaffolder Cnaphalocrocis medinalis ligand-binding experiments, molecular docking, RNA interference and electrophysiological recording were performed. The binding activity of two C. medinalis OBPs (CmedOBPs) to rice plant volatiles showed wide flexibility depending on the structure of ligands and interactions of CmedOBPs involved. The binding sites of CmedOBP2 and CmedOBP3 to rice plant volatiles were well predicted by three-dimensional structure modelling and molecular docking experiments. In addition, the interactions of these two CmedOBPs in the perception of rice volatiles were demonstrated by RNA interference experiments. When a single double-stranded RNA (dsRNA)-Cme-dOBP2 was injected, the expression of CmedOBP2 was significantly reduced and the expression of CmedOBP3 was significantly increased, and vice versa. When both dsRNA-CmedOBP2 and 3 were injected together, greater reduction of electroantennogram responses to rice plant volatiles was induced than that seen with individual injection of either dsRNA-CmedOBP2 or dsRNA-CmedOBP3. These results clearly indicate that the interactions of CmedOBP2 and CmedOBP3 have significant effects on C. medinalis during the detection of host plant volatiles.