title: Chemosensory adaptations of the mountain fly Drosophila nigrosparsa (Insecta: Diptera) through genomics' and structural biology's lenses.
abstract: Chemoreception is essential for survival. Some chemicals signal the presence of nutrients or toxins, others the proximity of mating partners, competitors, or predators. Chemical signal transduction has therefore been studied in multiple organisms. In Drosophila species, a number of odorant receptor genes and various other types of chemoreceptors were found. Three main gene families encode for membrane receptors and one for globular proteins that shuttle compounds with different degrees of affinity and specificity towards receptors. By sequencing the genome of Drosophila nigrosparsa, a habitat specialist restricted to montane/alpine environment, and combining genomics and structural biology techniques, we characterised odorant, gustatory, ionotropic receptors and odorant binding proteins, annotating 189 loci and modelling the protein structure of two ionotropic receptors and one odorant binding protein. We hypothesise that the D. nigrosparsa genome experienced gene loss and various evolutionary pressures (diversifying positive selection, relaxation, and pseudogenisation), as well as structural modification in the geometry and electrostatic potential of the two ionotropic receptor binding sites. We discuss possible trajectories in chemosensory adaptation processes, possibly enhancing compound affinity and mediating the evolution of more specialized food, and a fine-tuned mechanism of adaptation.
authors.affiliation: Institute of Ecology, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cicconardi
authors.affiliation: Department of Informatics, Institute of Computational Science, University of Italian Switzerland, Lugano, Switzerland.
authors.forename: Daniele
authors.initials: D
authors.lastname: Di Marino
authors.affiliation: Department of Physics, Sapienza University of Rome, Rome, Italy.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Olimpieri
authors.affiliation: Institute of Ecology, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Arthofer
authors.affiliation: Institute of Ecology, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria.
authors.forename: Birgit C
authors.initials: BC
authors.lastname: Schlick-Steiner
authors.affiliation: Institute of Ecology, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria.
authors.forename: Florian M
authors.initials: FM
authors.lastname: Steiner
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000145:classification / Q000235:genetics*; D015698:Genomic Library; D023281:Genomics / Q000379:methods*; D008958:Models, Molecular; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000145:classification / Q000235:genetics*; D058468:Receptors, Ionotropic Glutamate / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D018035:Receptors, Odorant / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D017422:Sequence Analysis, DNA / Q000379:methods
chemical_list: D029721:Drosophila Proteins; D011956:Receptors, Cell Surface; D058468:Receptors, Ionotropic Glutamate; D018035:Receptors, Odorant; C405956:gustatory receptor, Drosophila; C045648:odorant-binding protein