Dataset Information

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characterized by divergent alleles in the European and American genomes, and we hypothesize that they may have been replaced by some of the duplicated ORs in corresponding neurons, a hypothesis reciprocally confirmed by electrophysiological recordings.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.

SUBMITTER: Ramasamy S

PROVIDER: S-EPMC5010897 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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The Evolution of Olfactory Gene Families in Drosophila and the Genomic Basis of chemical-Ecological Adaptation in Drosophila suzukii.

Ramasamy Sukanya S Ometto Lino L Crava Cristina M CM Revadi Santosh S Kaur Rupinder R Horner David S DS Pisani Davide D Dekker Teun T Anfora Gianfranco G Rota-Stabelli Omar O

Genome biology and evolution 20160816 8

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 W ...[more]

PMID: 27435796

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Project description:BACKGROUND:As our world becomes warmer, agriculture is increasingly impacted by rising soil salinity and understanding plant adaptation to salt stress can help enable effective crop breeding. Salt tolerance is a complex plant phenotype and we know little about the pathways utilized by naturally tolerant plants. Legumes are important species in agricultural and natural ecosystems, since they engage in symbiotic nitrogen-fixation, but are especially vulnerable to salinity stress. RESULTS:Our studies of the model legume Medicago truncatula in field and greenhouse settings demonstrate that Tunisian populations are locally adapted to saline soils at the metapopulation level and that saline origin genotypes are less impacted by salt than non-saline origin genotypes; these populations thus likely contain adaptively diverged alleles. Whole genome resequencing of 39 wild accessions reveals ongoing migration and candidate genomic regions that assort non-randomly with soil salinity. Consistent with natural selection acting at these sites, saline alleles are typically rare in the range-wide species' gene pool and are also typically derived relative to the sister species M. littoralis. Candidate regions for adaptation contain genes that regulate physiological acclimation to salt stress, such as abscisic acid and jasmonic acid signaling, including a novel salt-tolerance candidate orthologous to the uncharacterized gene AtCIPK21. Unexpectedly, these regions also contain biotic stress genes and flowering time pathway genes. We show that flowering time is differentiated between saline and non-saline populations and may allow salt stress escape. CONCLUSIONS:This work nominates multiple potential pathways of adaptation to naturally stressful environments in a model legume. These candidates point to the importance of both tolerance and avoidance in natural legume populations. We have uncovered several promising targets that could be used to breed for enhanced salt tolerance in crop legumes to enhance food security in an era of increasing soil salinization.

Project description:BackgroundDrosophila suzukii differs from other melanogaster group members in their proclivity for laying eggs in fresh fruit rather than in fermenting fruits. Olfaction and gustation play a critical role during insect niche formation, and these senses are largely mediated by two important receptor families: olfactory and gustatory receptors (Ors and Grs). Earlier work from our laboratory has revealed how the olfactory landscape of D. suzukii is dominated by volatiles derived from its unique niche. Signaling and reception evolve in synchrony, since the interaction of ligands and receptors together mediate the chemosensory behavior. Here, we manually annotated the Ors and Grs in D. suzukii and two close relatives, D. biarmipes and D. takahashii, and compared these repertoires to those in other melanogaster group drosophilids to identify candidate chemoreceptors associated with D. suzukii's unusual niche utilization.ResultsOur comprehensive annotations of the chemosensory genomes in three species, and comparative analysis with other melanogaster group members provide insights into the evolution of chemosensation in the pestiferous D. suzukii. We annotated a total of 71 Or genes in D. suzukii, with nine of those being pseudogenes (12.7 %). Alternative splicing of two genes brings the total to 62 genes encoding 66 Ors. Duplications of Or23a and Or67a expanded D. suzukii's Or repertoire, while pseudogenization of Or74a, Or85a, and Or98b reduced the number of functional Ors to roughly the same as other annotated species in the melanogaster group. Seventy-one intact Gr genes and three pseudogenes were annotated in D. suzukii. Alternative splicing in three genes brings the total number of Grs to 81. We identified signatures of positive selection in two Ors and three Grs at nodes leading to D. suzukii, while three copies in the largest expanded Or lineage, Or67a, also showed signs of positive selection at the external nodes.ConclusionOur analysis of D. suzukii's chemoreceptor repertoires in the context of nine melanogaster group drosophilids, including two of its closest relatives (D. biarmipes and D. takahashii), revealed several candidate receptors associated with the adaptation of D. suzukii to its unique ecological niche.

Dataset Information

The Evolution of Olfactory Gene Families in Drosophila and the Genomic Basis of chemical-Ecological Adaptation in Drosophila suzukii.

Publications

The Evolution of Olfactory Gene Families in Drosophila and the Genomic Basis of chemical-Ecological Adaptation in Drosophila suzukii.

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