Expression profiles and functional prediction of ionotropic receptors in Asian corn borer,Ostrinia furnacalis (Lepidoptera: Crambidae)

Genes involved in chemosensation are essential for odorant-mediated insect behaviors. Odorant receptors (ORs) bind and respond to pheromones and plant volatiles, regulating insect behaviors such as mating and host-plant selection, while ionotropic receptors (IRs), which are present at lower levels in insects than ORs, influence ion channels, especially in agricultural pests. Asian corn borer, Ostrinia furnacalis, is the main pest of maize that causes huge economic losses in Asia. Twenty-one OfurIRs have been identified, but none has been characterized. In this study, tissue-specific expression profiling, phylogenetic analysis, and electroantennography (EAG) analysis were applied to characterize the evolution, expression, and the potential function of OfurIRs. It was found that 20 OfurIRs were highly expressed in the antennae, except for OfurIR75p3, whereas 10 and nine OfurIRs were highly expressed in the proboscis and genitalia, respectively, indicating that these OfurIRs were functionally associated with feeding and oviposition. EAG results showed that seven acids elicited responses in the antennae of O. furnacalis and that 2-oxopentanoic acid displayed a significant female-biased response. Combined with the phylogenetic analysis, 10 OfurIRs in clade 4 were roughly predicted to be candidate receptors for 2-oxopentanoic acid and other tested acids. These results provide basic information about OfurIRs and may help advance the knolwedge on the olfactory system of O. furnacalis.