AbstractHelicoverpa armigera utilizes (Z)-11-hexadecenal (Z11-16:Ald) as its major sex pheromone component. Three pheromone binding proteins (PBPs) and two general odorant binding proteins (GOBPs) are abundantly expressed in male antennae of H. armigera. However, their precise roles in the olfactory detection of Z11-16:Ald remain enigmatic. To answer this question, we first synthesized the antibody against HarmOR13, a pheromone receptor (PR) primarily responding to Z11-16:Ald and mapped the local associations between PBPs / GOBPs and HarmOR13. Immunostaining showed that HarmPBPs and HarmGOBPs were localized in the supporting cells of sensilla trichodea and sensilla basiconica respectively. In particular, HarmPBP1 and HarmPBP2 were colocalized in the cells surrounding the olfactory receptor neurons (ORNs) expressing HarmOR13. Next, using two noninterfering binary expression tools, we heterologously expressed HarmPBP1, HarmPBP2 and HarmOR13 in Drosophila T1 sensilla to validate the functional interplay between PBPs and HarmOR13. We found that the addition of HarmPBP1 or HarmPBP2 significantly increased the sensitivity of HarmOR13 to Z11-16:Ald. However, the presence of either HarmPBP1 or HarmPBP2 was ineffective to change the tuning breadth of HarmOR13. Taken together, our results support the idea that PBPs are contributors to the peripheral olfactory sensitivity but do not affect the selectivity. Lastly, we discovered that HarmOR13 and the Drosophila OR67d employed a similar coding mechanism to detect pheromones, suggesting that pheromone detection across different insect orders appears to co-opt a conserved molecular principle to recognize pheromone ligands.
Binding Properties of General Odorant Binding Proteins from the Oriental Fruit Moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae)
