title: The Evolution of Olfactory Gene Families in Drosophila and the Genomic Basis of chemical-Ecological Adaptation in Drosophila suzukii.
abstract: How the evolution of olfactory genes correlates with adaption to new ecological niches is still a debated topic. We explored this issue in Drosophila suzukii, an emerging model that reproduces on fresh fruit rather than in fermenting substrates like most other Drosophila We first annotated the repertoire of odorant receptors (ORs), odorant binding proteins (OBPs), and antennal ionotropic receptors (aIRs) in the genomes of two strains of D. suzukii and of its close relative Drosophila biarmipes We then analyzed these genes on the phylogeny of 14 Drosophila species: whereas ORs and OBPs are characterized by higher turnover rates in some lineages including D. suzukii, aIRs are conserved throughout the genus. Drosophila suzukii is further characterized by a non-random distribution of OR turnover on the gene phylogeny, consistent with a change in selective pressures. In D. suzukii, we found duplications and signs of positive selection in ORs with affinity for short-chain esters, and loss of function of ORs with affinity for volatiles produced during fermentation. These receptors-Or85a and Or22a-are characterized by divergent alleles in the European and American genomes, and we hypothesize that they may have been replaced by some of the duplicated ORs in corresponding neurons, a hypothesis reciprocally confirmed by electrophysiological recordings. Our study quantifies the evolution of olfactory genes in Drosophila and reveals an array of genomic events that can be associated with the ecological adaptations of D. suzukii.
authors.affiliation: Agricultural Entomology Unit, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy Diparimento di Bioscienze, Università degli Studi di Milano, Milano, Italy.
authors.forename: Sukanya
authors.initials: S
authors.lastname: Ramasamy
authors.affiliation: Agricultural Entomology Unit, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy.
authors.forename: Lino
authors.initials: L
authors.lastname: Ometto
authors.affiliation: Agricultural Entomology Unit, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy.
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Crava
authors.affiliation: Agricultural Entomology Unit, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy Chemical Ecology Unit, Swedish University of Agricultural Sciences, Alnarp, Sweden.
authors.forename: Santosh
authors.initials: S
authors.lastname: Revadi
authors.affiliation: Agricultural Entomology Unit, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy.
authors.forename: Rupinder
authors.initials: R
authors.lastname: Kaur
authors.affiliation: Diparimento di Bioscienze, Università degli Studi di Milano, Milano, Italy.
authors.forename: David S
authors.initials: DS
authors.lastname: Horner
authors.affiliation: School of Biological Sciences and School of Earth Sciences, University of Bristol, Bristol, UK.
authors.forename: Davide
authors.initials: D
authors.lastname: Pisani
authors.affiliation: Chemical Ecology Unit, Swedish University of Agricultural Sciences, Alnarp, Sweden.
authors.forename: Teun
authors.initials: T
authors.lastname: Dekker
authors.affiliation: Agricultural Entomology Unit, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Anfora
authors.affiliation: Agricultural Entomology Unit, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy omar.rota@fmach.it.
authors.forename: Omar
authors.initials: O
authors.lastname: Rota-Stabelli
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D004330:Drosophila / Q000145:classification / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D049750:Genome, Insect; D005810:Multigene Family; D010802:Phylogeny; D018035:Receptors, Odorant / Q000235:genetics* / Q000378:metabolism; D012641:Selection, Genetic
chemical_list: D029721:Drosophila Proteins; C496847:OR22a protein, Drosophila; C000622902:Or85a protein, Drosophila; D018035:Receptors, Odorant
keywords: Drosophila suzukii; adaptation; comparative genomics; odorant receptors