Abstract
BackgroundOlfactory cues drive mosquito behaviors such as host-seeking, locating sugar sources and oviposition. These behaviors can vary between sexes and closely related species. For example, the malaria vector Anopheles coluzzii is highly anthropophilic, whereas An. quadriannulatus is not. These behavioral differences may be reflected in chemosensory gene expression.MethodsThe expression of chemosensory genes in the antennae of both sexes of An. coluzzii and An. quadriannulatus was compared using RNA-seq. The sex-biased expression of several genes in An. coluzzii was also compared using qPCR.ResultsThe chemosensory expression is mostly similar in the male antennae of An. coluzzii and An. quadriannulatus, with only a few modest differences in expression. A handful of chemosensory genes are male-biased in both species; the highly expressed gustatory receptor AgGr33, odorant binding proteins AgObp25, AgObp26 and possibly AgObp10. Although the chemosensory gene repertoire is mostly shared between the sexes, several highly female-biased AgOrs, AgIrs, and one AgObp were identified, including several whose expression is biased towards the anthropophilic An. coluzzii. Additionally, the expression of several chemosensory genes is biased towards An. coluzzii in both sexes.ConclusionsChemosensory gene expression is broadly similar between species and sexes, but several sex- biased/specific genes were identified. These may modulate sex- and species-specific behaviors. Although the male behavior of these species remains poorly studied, the identification of sex- and species-specific chemosensory genes may provide fertile ground for future work.
Highlights
Olfactory cues drive mosquito behaviors such as host-seeking, locating sugar sources and oviposi‐ tion
Athrey et al Parasites Vectors (2020) 13:212 are covered densely with sensilla that house the olfactory sensory neurons which can express one of several classes of receptors: the olfactory receptors (ORs) or ionotropic receptors (IRs), and the gustatory receptor genes that encode the C O2 receptor (AgGr22, AgGr23 and AgGr24) that are expressed in the maxillary palps in mosquitoes [7]
After application of the filtering step to exclude genes with abundance lower than one Transcripts per million (TPM), we retained a final set of 12,329 genes out of a total of 13,796 genes found in the annotation set
Summary
Olfactory cues drive mosquito behaviors such as host-seeking, locating sugar sources and oviposi‐ tion. These behaviors can vary between sexes and closely related species. The malaria vector Anopheles coluzzii is highly anthropophilic, whereas An. quadriannulatus is not. These behavioral differences may be reflected in chemosensory gene expression. One of the primary vectors of malaria in sub-Saharan Africa, depend on olfactory cues for host-seeking, identifying sources for sugar meals, as well as locating oviposition sites [1]. The antennae and the maxillary palps comprise the primary olfactory tissues of An. coluzzii. While ORs function as ligand-gated ion channels, there are indications that they are modulated indirectly by G-protein signaling [12, 13]
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