Chemosensory gene expression in olfactory organs of the anthropophilic Anopheles coluzzii and zoophilic Anopheles quadriannulatus

Abstract

Background Anopheles (An.) coluzzii, one of Africa’s primary malaria vectors, is highly anthropophilic. This human host preference contributes greatly to its ability to transmit malaria. In contrast, the closely related An. quadriannulatus prefers to feed on bovids and is not thought to contribute to malaria transmission. The diverged preference for host odor profiles between these sibling species is likely reflected in chemosensory gene expression levels in the olfactory organs. Therefore, we compared the transcriptomes of the antennae and maxillary palps between An. coluzzii and An. quadriannulatus, focusing on the major chemosensory gene families.ResultsWhile chemosensory gene expression is strongly correlated between the two species, various chemosensory genes show significantly enhanced expression in one of the species. In the antennae of An. coluzzii the expression of six olfactory receptors (Ors) and seven ionotropic receptors (Irs) is considerably enhanced, whereas 11 Ors and 3 Irs are upregulated in An. quadriannulatus. In the maxillary palps, leaving aside Irs with very low level of expression, one Ir is strongly enhanced in each species. In addition, we find divergence in odorant binding protein (Obp) gene expression, with several highly expressed Obps being enhanced in the antennae and palps of An. coluzzii. Finally, the expression of several gustatory receptors (Grs) in the palps appears to be species-specific, including a homolog of a sugar-sensing Drosophila Gr. ConclusionsA considerable number of Ors and Irs are differentially expressed between these two closely related species with diverging host preference. These chemosensory genes could play a role in the human host preference of the malaria vector An. coluzzii. Additionally, divergence in Obp expression between the two species suggests a possible role of these odor carrier proteins in determining host preference. Finally, divergence in chemosensory expression in the palps may point towards a possible role for the maxillary palps in host differentiation.Electronic supplementary materialThe online version of this article (10.1186/s12864-017-4122-7) contains supplementary material, which is available to authorized users.

Has gene expression neofunctionalization in the fire ant antennae contributed to queen discrimination behavior?

“…The antennae are the main sensory organ of insects, and thus, the genes expressed there have a large effect on what insects can detect and consequently how they behave (Athrey et al, ; Chen et al, ; McBride et al, ; Zhao et al, ). Our analysis identified 81 DEGs in the antennae across three worker classes (monogyne SB/SB , polygyne SB/SB , and polygyne SB/Sb ).…”

Species and sex-specific chemosensory gene expression in Anopheles coluzzii and An. quadriannulatus antennae

“…The Illumina sequencing generated between 47.2 to 67.1 million reads per library for the male antennae samples. The total reads generated for the female antennae libraries ranged between 35.2 and 53.5 million [21]. For the male antennal samples, between 88.4 and 89.5% of the total reads mapped uniquely to exon features across the two species (Additional file 2: Table S2).…”

“…However, both these genes were expressed at < 5.5 TPM, quite a bit lower than in the antennae of female An. coluzzii [21].…”

“…coluzzii and zoophilic An. quadriannulatus have identified species-specific patterns of chemosensory gene expression, which may underlie diverging host preference [20,21].…”

“…coluzzii and An. quadriannulatus, and included previously published data [21] to identify sex-and species-specific patterns of chemosensory gene expression between An. coluzzii and An.…”