Genome-wide identification and expression profiling of odorant receptor genes in the malaria vector Anopheles sinensis

Abstract

Background The olfactory system plays a crucial role in regulating insect behaviors. The detection of odorants is mainly mediated by various odorant receptors (ORs) that are expressed in the dendrites of olfactory neurons of chemosensilla. Anophelessinensis is a major malaria vector in Eastern Asia and its genome has recently been successfully sequenced and annotated. In this study, we present genome-wide identification and expression profiling of OR genes in different chemosensory tissues of An.sinensis. Methods The OR genes were identified using the available genome sequences of An.sinensis. A series of bioinformatics analyses were conducted to investigate the structure, genome distribution, selective pressure and phylogenetic relationships of OR genes, the conserved domains and specific functional sites in the OR amino acid sequences. The expression levels of OR genes were analyzed from transcriptomic data from An.sinensis antennae, proboscis and maxillary palps of both sexes. Results A total of 59 putative OR genes have been identified and characterized in An.sinensis. This number is significantly less than that in An.gambiae. Whether this difference is caused by the contraction or expansion of OR genes after divergence of the two species remains unknown. The RNA-seq analysis showed that AsORs have obvious tissue- and sex-specific expression patterns. Most AsORs are highly expressed in the antennae and the expression pattern and number of AsORs expressed in antennae are similar in males and females. However, the relative levels of AsOR transcripts are much higher in female antennae than in male antennae, which indicates that the odor sensitivity is likely to be increased in female mosquitoes. Based on the expression patterns and previous studies, we have speculated on the functions of some OR genes but this needs to be validated by further behavioral, molecular and electrophysiological studies. Further studies are necessary to compare the olfactory-driven behaviors and identify receptors that respond strongly to components of human odors that may act in the process of human recognition. Conclusions This is the first genome-wide analysis of the entire repertoire of OR genes in An.sinensis. Characterized features and profiled expression patterns of ORs suggest their involvement in the odorous reception of this species. Our findings provide a basis for further research on the functions of OR genes and additional genetic and behavioral targets for more sustainable management of An.sinensis in the future. Graphical Abstract

AsOBP1 is required for host seeking in the malaria vector mosquito, Anopheles sinensis

“…2A, D, E), whereas no uorescence was detected in any other tissues, including the proboscis and maxillary palps of both sexes (Fig. 2L-O), consistent with previous results (Qin et al 2014;He et al 2022). We did not detect GFP uorescence in the antennae of embryonic and pupal stages (Fig.…”

“…Our previous results showed that AsOBP1 is an antenna-speci c expression gene (Qin et al 2014;He et al 2022), which is corroborated by expression of AsOBP1 in a transgenic line of An. sinensis.…”

“…sinensis genome, > 60 putative OBP-encoding genes have been identi ed (He et al, 2016). Around 10 genes displayed a strong expression bias for female antennae (He et al 2022), and some members are regulated after a blood meal, indicating that the corresponding proteins might be involved in host recognition (Chen et al 2017). An.…”

“…sinensis genome (He et al 2016), and most OBP genes are highly expressed in the female antennae and are speculated to play canonical roles in olfaction (He et al 2022). Among the OBP genes, AsOBP1 is speci cally expressed in the antenna and downregulated by mouse odors and blood feeding (Qin et al 2014;He et al 2022). Therefore, we reasoned that AsOBP1 is likely involved in host seeking in An.…”

Effects of antennal segments defects on blood-sucking behavior in Aedes albopictus

“…An empty engineered neuron of the Drosophila melanogaster was used as well to express mosquito olfactory-related genes and the responses of this neuron to individual odors were assayed using SSR [72]. Over the past decade, real-time qPCR, transcriptome based on RNA sequencing, and genome-wide analysis of the entire repertoire of olfactory-related genes were widely used to explore a comprehensive expression atlas specific to blood meal, sex, tissue and mosquito species, several olfactory-related genes associated with blood-seeking behavior in mosquitoes have been screened, and the functions in the behavior of which remain to be clarified one by one [73][74][75][76][77][78]. For Ae.…”