Comparative Genomics Provide Insights Into Function and Evolution of Odorant Binding Proteins in Cydia pomonella

Insect olfaction is vital for foraging, mating, host-seeking, and avoidance of predators/pathogens. In insects, odorant binding proteins (OBPs) are involved in transporting hydrophobic odor molecules from the external environment to receptor neurons. The codling moth,Cydia pomonella, one of the most destructive insect fruit pests, causes enormous economic losses. However, little is known about the number, variety, gains and losses, and evolution ofOBPgenes inC. pomonella. Here we report the identification of 40OBPsinC. pomonella, most (75%) of which are classicOBPs, using genomic and transcriptomic analyses. TwoOBPgenes were lost inC. pomonellarelative to possible distant ancestor in Lepidoptera lineage based on an analysis of gene gains and losses. The phylogenetic tree and chromosome location showed that the expansion ofOBPgenes mainly resulted from tandem duplications, as theCpomGOBP2gene was duplicated twice along with loss ofCpomPBPB. Two positive selection sites of theCpomGOBP1gene were identified while otherOBPgenes evolved under purifying selection. Our results provide fundamental knowledge ofOBPgenes allowing further study of their function inC. pomonella.