The evolution of olfactory gene families in Drosophila and the genomic basis of chemical-ecological adaptation in Drosophila suzukii

Sukanya Ramasamy, Lino Ometto, Cristina M Crava, Santosh Revadi, Rupinder Kaur, David Horner, Davide Pisani, Teun Dekker, Gianfranco Anfora, Omar Rota-Stabelli

Research output: Contribution to journalArticle (Academic Journal)peer-review

32 Citations (Scopus)
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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 (OR), odorant binding proteins (OBP), and antennal ionotropic receptors (aIR) in the genomes of two strains of D. suzukii and of its close relative Drosophila biarmipes. We then analysed these genes on the phylogeny of 14 Drosophila species: while ORs and OBPs are characterised by higher turnover rates in some lineages including D. suzukii, aIRs are conserved throughout the genus. D. suzukii is further characterised 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- are characterised by divergent alleles in the European and American genomes, and we hypothesise that they may have been replaced by some of the duplicated ORs in corresponding neurons, a hypothesis reciprocally confirmed by electrophysiological recordings.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.

Original languageEnglish
Pages (from-to)2297-2311
Number of pages15
JournalGenome Biology and Evolution
Volume8
Issue number8
Early online date19 Jul 2016
DOIs
Publication statusPublished - Aug 2016

Keywords

  • odorant receptors
  • adaptation
  • Drosophila suzuki
  • comparative genomics

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