Variation in vectorial capacity for human malaria among Anopheles mosquito species is determined by many factors, including behavior, immunity, and life history. To investigate the genomic basis of vectorial capacity and explore new avenues for vector control, we sequenced the genomes of 16 anopheline mosquito species from diverse locations spanning ~100 million years of evolution. Comparative analyses show faster rates of gene gain and loss, elevated gene shuffling on the X chromosome, and more intron losses, relative to Drosophila. Some determinants of vectorial capacity, such as chemosensory genes, do not show elevated turnover, but instead diversify through protein-sequence changes. This dynamism of anopheline genes and genomes may contribute to their flexible capacity to take advantage of new ecological niches, including adapting to humans as primary hosts.

Summary The mosquito Anopheles gambiae is the major vector of malaria in sub-Saharan Africa. It locates its human hosts primarily through olfaction, but little is known about the molecular basis of this process. Here we functionally characterize the Anopheles gambiae Odourant Receptor (AgOr) repertoire. We identify receptors that respond strongly to components of human odour and that may act in the process of human recognition. Some of these receptors are narrowly tuned, and some salient odourants elicit strong responses from only one or a few receptors, suggesting a central role for specific transmission channels in human host-seeking behavior. This analysis of the Anopheles gambiae receptors permits a comparison with the corresponding Drosophila melanogaster odourant receptor repertoire. We find that odourants are differentially encoded by the two species in ways consistent with their ecological needs. Our analysis of the Anopheles gambiae repertoire identifies receptors that may be useful targets for controlling the transmission of malaria.

We used bioinformatic approaches to identify a total of 276 G protein-coupled receptors (GPCRs) from the Anopheles gambiae genome. These include GPCRs that are likely to play roles in pathways affecting almost every aspect of the mosquito's life cycle. Seventy-nine candidate odorant receptors were characterized for tissue expression and, along with 76 putative gustatory receptors, for their molecular evolution relative to Drosophila melanogaster. Examples of lineage-specific gene expansions were observed as well as a single instance of unusually high sequence conservation.

A systematic functional analysis across much of the conventional Anopheles gambiae odorant receptor (AgOR) repertoire was carried out in Xenopus oocytes using two-electrode, voltage-clamp electrophysiology. The resulting data indicate that each AgOR manifests a distinct odor-response profile and tuning breadth. The large diversity of tuning responses ranges from AgORs that are responsive to a single or small number of odorants (specialists) to more broadly tuned receptors (generalists). Several AgORs were identified that respond robustly to a range of human volatiles that may play a critical role in anopheline host selection. AgOR responses were analyzed further by constructing a multidimensional odor space representing the relationships between odorants and AgOR responses. Within this space, the distance between odorants is related to both chemical class and concentration and may correlate with olfactory discrimination. This study provides a comprehensive overview of olfactory coding mechanisms of An. gambiae that ultimately may aid in fostering the design and development of olfactory-based strategies for reducing the transmission of malaria and other mosquito-borne diseases.odorant receptor | olfaction

Our results describe a complete and highly concordant map of both the molecular and cellular olfactory components on the maxillary palp of the adult female An. gambiae mosquito. These results also facilitate the understanding of how An. gambiae mosquitoes sense olfactory cues that might be exploited to compromise their ability to transmit malaria.

The period gene (per) is required for Drosophila melanogaster to manifest circadian (congruent to 24 hr) rhythms. We report here that per protein (PER) undergoes daily oscillations in apparent molecular mass as well as abundance. The mobility changes are largely or exclusively due to multiple phosphorylation events. The temporal profile of the classic short-period form of PER (PERS) is altered in a manner consistent with the mutant strain's behavioral phenotype. As changes in abundance and phosphorylation persist under constant environmental conditions, they reflect or contribute to a free-running rhythm. We suggest that the phosphorylation status of PER is an important determinant in the Drosophila clock's time-keeping mechanism.

Ants are a highly successful family of insects that thrive in a variety of habitats across the world. Perhaps their best-known features are complex social organization and strict division of labor, separating reproduction from the day-to-day maintenance and care of the colony, as well as strict discrimination against foreign individuals. Since these social characteristics in ants are thought to be mediated by semiochemicals, a thorough analysis of these signals, and the receptors that detect them, is critical in revealing mechanisms that lead to stereotypic behaviors. To address these questions, we have defined and characterized the major chemoreceptor families in a pair of behaviorally and evolutionarily distinct ant species, Camponotus floridanus and Harpegnathos saltator. Through comprehensive re-annotation, we show that these ant species harbor some of the largest yet known repertoires of odorant receptors (Ors) among insects, as well as a more modest number of gustatory receptors (Grs) and variant ionotropic glutamate receptors (Irs). Our phylogenetic analyses further demonstrate remarkably rapid gains and losses of ant Ors, while Grs and Irs have also experienced birth-and-death evolution to different degrees. In addition, comparisons of antennal transcriptomes between sexes identify many chemoreceptors that are differentially expressed between males and females and between species. We have also revealed an agonist for a worker-enriched OR from C. floridanus, representing the first case of a heterologously characterized ant tuning Or. Collectively, our analysis reveals a large number of ant chemoreceptors exhibiting patterns of differential expression and evolution consistent with sex/species-specific functions. These differentially expressed genes are likely associated with sex-based differences, as well as the radically different social lifestyles observed between C. floridanus and H. saltator, and thus are targets for further functional characterization. Our findings represent an important advance toward understanding the molecular basis of social interactions and the differential chemical ecologies among ant species.

BackgroundChemosensory signal transduction guides the behavior of many insects, including Anopheles gambiae, the major vector for human malaria in sub-Saharan Africa. To better understand the molecular basis of mosquito chemosensation we have used whole transcriptome RNA sequencing (RNA-seq) to compare transcript expression profiles between the two major chemosensory tissues, the antennae and maxillary palps, of adult female and male An. gambiae.ResultsWe compared chemosensory tissue transcriptomes to whole body transcriptomes of each sex to identify chemosensory enhanced genes. In the six data sets analyzed, we detected expression of nearly all known chemosensory genes and found them to be highly enriched in both olfactory tissues of males and females. While the maxillary palps of both sexes demonstrated strict chemosensory gene expression overlap, we observed acute differences in sensory specialization between male and female antennae. The relatively high expression levels of chemosensory genes in the female antennae reveal its role as an organ predominately assigned to chemosensation. Remarkably, the expression of these genes was highly conserved in the male antennae, but at much lower relative levels. Alternatively, consistent with a role in mating, the male antennae displayed significant enhancement of genes involved in audition, while the female enhancement of these genes was observed, but to a lesser degree.ConclusionsThese findings suggest that the chemoreceptive spectrum, as defined by gene expression profiles, is largely similar in female and male An. gambiae. However, assuming sensory receptor expression levels are correlated with sensitivity in each case, we posit that male and female antennae are perceptive to the same stimuli, but possess inverse receptive prioritizations and sensitivities. Here we have demonstrated the use of RNA-seq to characterize the sensory specializations of an important disease vector and grounded future studies investigating chemosensory processes.