Bioinformatic and evolutionary analysis of chemoreceptors and related proteins in a grapevine pest

Drosophila suzukii is an invasive pest of fruits such as grapevine, berries and cherries. D. suzukii lays eggs on ripening, unwounded fruits, while most other Drosophila oviposit on rottening fruits. This switch in ecological behaviour is reflected by morphological adaptations such as a serrated ovipositor, but should also include adaptations for tracking the odor of fresh fruits. In Drosophila, like in all other insects, odor(chemo) reception is mediated by multi-gene families of olfactory and gustatory receptors (Ors, IRs and GRs) sometimes assisted by two diverse protein families, odorant binding and chemosensory proteins (OBPs and CSPs). Knowledge of these genes may not only help in developing agricultural controlling strategies, but also offer an interesting model for the study of evolution of behavioral innovation. We extensively blasted the newly sequenced genome of D. suzukii, identified its likely full set of chemosensory receptors, and conducted a comparative genomic analyses of these genes in various sister species. Results show that repertoire of chemosensory genes in D. suzukii is different to that of sister species, but that this variation follows a likely birth death process as in other Drosophilas. Exception is the OBP family where the gene loss is significantly higher in D. suzukii than in sister species. Our results reveal some specific gene gains and losses in D. suzukii that may be responsible for its innovative behavio