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Genetic polymorphism at an odorant receptor gene (Or39) among mosquitoes of the Anopheles gambiae complex in Senegal (West Africa).

Arnal A, Kengne P, Brengues C, Dabire KR, Diabate A, Bassene H, Simard F - BMC Res Notes (2014)

Bottom Line: Throughout the whole dataset, there were 13 non-synonymous mutations resulting in aminoacid changes in the encoded protein.However, intraspecific polymorphisms in An. gambiae and An. arabiensis as well as species-specific mutations also occurred in the first extracellular domain.Although obtained from a limited number of specimens, our results point towards genetic differences between cryptic species within the An. gambiae complex in a gene of biological relevance that might be of evolutionary significance when exposed to disruptive selective forces.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Recherche pour le Développement (IRD), UMR IRD 224-CNRS 5290-UM1-UM2 MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Genetique, Evolution et Contrôle), team BEES (Biology, Ecology and Evolution of vector Systems), 911 Avenue Agropolis, BP 64501, Montpellier, cedex 5 34394, France. au.arnal@gmail.com.

ABSTRACT

Background: Olfaction plays a significant role in insect behavior during critical steps of their life-cycle, such as host-seeking during foraging or the search for a mate. Here, we explored genetic polymorphism within and divergence between sibling species of the African malaria mosquito, Anopheles gambiae sensu lato in the gene sequence and encoded peptides of an odorant receptor, Or39. This study included sympatric specimens of An. gambiae sensu stricto, An. coluzzii and An. arabiensis sampled together in the village of Dielmo, Senegal.

Results: A 1,601 bp genomic sequence composed of 6 exons and 5 introns was obtained for Or39 from 6-8 mosquitoes in each of the 3 species. DNA sequence analysis revealed a high level of molecular polymorphism (π = 0.0154; Haplotype diversity = 0.867) and high overall genetic differentiation between taxa (Fst > 0.92, P < 0.01). In total, 50 parsimony informative sites were recorded. Throughout the whole dataset, there were 13 non-synonymous mutations resulting in aminoacid changes in the encoded protein. Each of the 6 different identified peptides was species-specific and none was shared across species. Most aminoacid changes were located on the intracellular domains of the protein. However, intraspecific polymorphisms in An. gambiae and An. arabiensis as well as species-specific mutations also occurred in the first extracellular domain.

Conclusions: Although obtained from a limited number of specimens, our results point towards genetic differences between cryptic species within the An. gambiae complex in a gene of biological relevance that might be of evolutionary significance when exposed to disruptive selective forces.

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Summary sequence alignment of the different Or39 haplotypes detected in mosquito specimens collected in the locality of Dielmo in Senegal during the 2007 rainy season. Only parsimony informative sites are shown (N = 50). Nucleotides are numbered according to the published reference sequence from the PEST strain of An. gambiae (VectorBase, AGAP002639). Dots indicate identity to the reference sequence. The coding regions (exons) are shaded.
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Figure 1: Summary sequence alignment of the different Or39 haplotypes detected in mosquito specimens collected in the locality of Dielmo in Senegal during the 2007 rainy season. Only parsimony informative sites are shown (N = 50). Nucleotides are numbered according to the published reference sequence from the PEST strain of An. gambiae (VectorBase, AGAP002639). Dots indicate identity to the reference sequence. The coding regions (exons) are shaded.

Mentions: DNA polymorphism analysis identified 68 (4.25%) variable sites along the sequence, of which 50 were parsimony informative (Figure 1). Average nucleotide diversity was lowest in An. coluzzii (π = 0.00033) and one order of magnitude higher in An. gambiae and An. arabiensis (π = 0.0012 and 0.0025, respectively) (Table 1). However, haplotype diversity was lower in An. arabiensis (Hd = 0.464) than in An. gambiae and An. coluzzii (Hd = 0.533 and 0.714, respectively). Throughout the whole gene region, there were 33 SNPs differences between An. gambiae and An. arabiensis, and 35 between An. arabiensis and An. coluzzii. These mutations were located in both exon and intron domains (Figure 1). A total of 16 SNPs were observed between An. gambiae and An. coluzzii, including 11 in exons. Four of these were replacement mutations. Within the coding region (Total exon length = 1,224 bp), non-synonymous diversity (dN, π nonSyn = 0.005) was 6 times lower than synonymous diversity (dS, π Syn = 0.029), although the difference was not significant (P> > 0.05, two-sided Fisher test of neutral evolution available in MEGA6). There was no evidence for deviation from neutral expectations in any species (McDonald-Kreitman test, P > 0.39).


Genetic polymorphism at an odorant receptor gene (Or39) among mosquitoes of the Anopheles gambiae complex in Senegal (West Africa).

Arnal A, Kengne P, Brengues C, Dabire KR, Diabate A, Bassene H, Simard F - BMC Res Notes (2014)

Summary sequence alignment of the different Or39 haplotypes detected in mosquito specimens collected in the locality of Dielmo in Senegal during the 2007 rainy season. Only parsimony informative sites are shown (N = 50). Nucleotides are numbered according to the published reference sequence from the PEST strain of An. gambiae (VectorBase, AGAP002639). Dots indicate identity to the reference sequence. The coding regions (exons) are shaded.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4048261&req=5

Figure 1: Summary sequence alignment of the different Or39 haplotypes detected in mosquito specimens collected in the locality of Dielmo in Senegal during the 2007 rainy season. Only parsimony informative sites are shown (N = 50). Nucleotides are numbered according to the published reference sequence from the PEST strain of An. gambiae (VectorBase, AGAP002639). Dots indicate identity to the reference sequence. The coding regions (exons) are shaded.
Mentions: DNA polymorphism analysis identified 68 (4.25%) variable sites along the sequence, of which 50 were parsimony informative (Figure 1). Average nucleotide diversity was lowest in An. coluzzii (π = 0.00033) and one order of magnitude higher in An. gambiae and An. arabiensis (π = 0.0012 and 0.0025, respectively) (Table 1). However, haplotype diversity was lower in An. arabiensis (Hd = 0.464) than in An. gambiae and An. coluzzii (Hd = 0.533 and 0.714, respectively). Throughout the whole gene region, there were 33 SNPs differences between An. gambiae and An. arabiensis, and 35 between An. arabiensis and An. coluzzii. These mutations were located in both exon and intron domains (Figure 1). A total of 16 SNPs were observed between An. gambiae and An. coluzzii, including 11 in exons. Four of these were replacement mutations. Within the coding region (Total exon length = 1,224 bp), non-synonymous diversity (dN, π nonSyn = 0.005) was 6 times lower than synonymous diversity (dS, π Syn = 0.029), although the difference was not significant (P> > 0.05, two-sided Fisher test of neutral evolution available in MEGA6). There was no evidence for deviation from neutral expectations in any species (McDonald-Kreitman test, P > 0.39).

Bottom Line: Throughout the whole dataset, there were 13 non-synonymous mutations resulting in aminoacid changes in the encoded protein.However, intraspecific polymorphisms in An. gambiae and An. arabiensis as well as species-specific mutations also occurred in the first extracellular domain.Although obtained from a limited number of specimens, our results point towards genetic differences between cryptic species within the An. gambiae complex in a gene of biological relevance that might be of evolutionary significance when exposed to disruptive selective forces.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Recherche pour le Développement (IRD), UMR IRD 224-CNRS 5290-UM1-UM2 MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Genetique, Evolution et Contrôle), team BEES (Biology, Ecology and Evolution of vector Systems), 911 Avenue Agropolis, BP 64501, Montpellier, cedex 5 34394, France. au.arnal@gmail.com.

ABSTRACT

Background: Olfaction plays a significant role in insect behavior during critical steps of their life-cycle, such as host-seeking during foraging or the search for a mate. Here, we explored genetic polymorphism within and divergence between sibling species of the African malaria mosquito, Anopheles gambiae sensu lato in the gene sequence and encoded peptides of an odorant receptor, Or39. This study included sympatric specimens of An. gambiae sensu stricto, An. coluzzii and An. arabiensis sampled together in the village of Dielmo, Senegal.

Results: A 1,601 bp genomic sequence composed of 6 exons and 5 introns was obtained for Or39 from 6-8 mosquitoes in each of the 3 species. DNA sequence analysis revealed a high level of molecular polymorphism (π = 0.0154; Haplotype diversity = 0.867) and high overall genetic differentiation between taxa (Fst > 0.92, P < 0.01). In total, 50 parsimony informative sites were recorded. Throughout the whole dataset, there were 13 non-synonymous mutations resulting in aminoacid changes in the encoded protein. Each of the 6 different identified peptides was species-specific and none was shared across species. Most aminoacid changes were located on the intracellular domains of the protein. However, intraspecific polymorphisms in An. gambiae and An. arabiensis as well as species-specific mutations also occurred in the first extracellular domain.

Conclusions: Although obtained from a limited number of specimens, our results point towards genetic differences between cryptic species within the An. gambiae complex in a gene of biological relevance that might be of evolutionary significance when exposed to disruptive selective forces.

Show MeSH
Related in: MedlinePlus