Sharon R. Hill

Bio: Sharon R. Hill is an academic researcher from Swedish University of Agricultural Sciences. The author has contributed to research in topics: Aedes aegypti & Malaria. The author has an hindex of 21, co-authored 55 publications receiving 1375 citations. Previous affiliations of Sharon R. Hill include Max Planck Society & University of Agricultural Sciences, Dharwad.

Sequencing of Culex quinquefasciatus Establishes a Platform for Mosquito Comparative Genomics

Abstract: Culex quinquefasciatus (the southern house mosquito) is an important mosquito vector of viruses such as West Nile virus and St. Louis encephalitis virus, as well as of nematodes that cause lymphatic filariasis. C. quinquefasciatus is one species within the Culex pipiens species complex and can be found throughout tropical and temperate climates of the world. The ability of C. quinquefasciatus to take blood meals from birds, livestock, and humans contributes to its ability to vector pathogens between species. Here, we describe the genomic sequence of C. quinquefasciatus: Its repertoire of 18,883 protein-coding genes is 22% larger than that of Aedes aegypti and 52% larger than that of Anopheles gambiae with multiple gene-family expansions, including olfactory and gustatory receptors, salivary gland genes, and genes associated with xenobiotic detoxification.

A key malaria metabolite modulates vector blood seeking, feeding, and susceptibility to infection

Abstract: Malaria infection renders humans more attractive to Anopheles gambiae sensu lato mosquitoes than uninfected people. The mechanisms remain unknown. We found that an isoprenoid precursor produced by ...

Characterization of Antennal Trichoid Sensilla from Female Southern House Mosquito, Culex quinquefasciatus Say

Abstract: Culex quinquefasciatus, the southern house mosquito, is highly dependent on its olfactory system for vector-related activities such as host seeking and oviposition. The antennae are the primary olfactory organs in mosquitoes. We describe 5 morphological types of sensilla on the antenna of C. quinquefasciatus: 1) a pair of sensilla coeloconica located at the distal tip, 2) long and short sensilla chaetica present on all 13 antennal flagella, 3) sensilla ampullacea found on the 2 proximal-most flagella, 4) 2 morphological types of grooved pegs dispersed throughout the flagella, and 5) 5 morphological subtypes of sensilla trichodea distributed among all flagella. Antennal trichoid and grooved peg sensilla of mosquitoes have been demonstrated to house the olfactory receptor neurons (ORNs) that detect many of the odors involved in eliciting vector-related behaviors. In order to initiate the functional characterization of the peripheral olfactory system in female C. quinquefasciatus, we mapped the physiological responses of all 5 morphological subtypes of sensilla trichodea to an odor panel of 44 behaviorally relevant odor compounds. We identified 17 functional classes of sensilla trichodea: 3 short sharp-tipped, 9 short blunt-tipped type I, and 5 short blunt-tipped type II sensilla. One morphological subtype remains unclassified as the long sharp-tipped sensilla did not respond to any of the volatiles tested. The functional classes of the ORNs were analyzed with respect to stimulus response profiles, stimuli sensitivity, and temporal coding patterns. Comparisons with other functionally classified mosquito antennal sensilla trichodea are discussed.

What Reaches the Antenna? How to Calibrate Odor Flux and Ligand-Receptor Affinities

Abstract: Physiological studies on olfaction frequently ignore the airborne quantities of stimuli reaching the sensory organ. We used a gas chromatography-calibrated photoionization detector to estimate quantities released from standard Pasteur pipette stimulus cartridges during repeated puffing of 27 compounds and verified how lack of quantification could obscure olfactory sensory neuron (OSN) affinities. Chemical structure of the stimulus, solvent, dose, storage condition, puff interval, and puff number all influenced airborne quantities. A model including boiling point and lipophilicity, but excluding vapor pressure, predicted airborne quantities from stimuli in paraffin oil on filter paper. We recorded OSN responses of Drosophila melanogaster, Ips typographus, and Culex quinquefasciatus, to known quantities of airborne stimuli. These demonstrate that inferred OSN tuning width, ligand affinity, and classification can be confounded and require stimulus quantification. Additionally, proper dose-response analysis shows that Drosophila AB3A OSNs are not promiscuous, but highly specific for ethyl hexanoate, with other earlier proposed ligands 10- to 10 000-fold less potent. Finally, we reanalyzed published Drosophila OSN data (DoOR) and demonstrate substantial shifts in affinities after compensation for quantity and puff number. We conclude that consistent experimental protocols are necessary for correct OSN classification and present some simple rules that make calibration, even retroactively, readily possible.

De novo assembly of the Aedes aegypti genome using Hi-C yields chromosome-length scaffolds

Abstract: The Zika outbreak, spread by the Aedes aegypti mosquito, highlights the need to create high-quality assemblies of large genomes in a rapid and cost-effective way. Here we combine Hi-C data with existing draft assemblies to generate chromosome-length scaffolds. We validate this method by assembling a human genome, de novo, from short reads alone (67× coverage). We then combine our method with draft sequences to create genome assemblies of the mosquito disease vectors Ae. aegypti and Culex quinquefasciatus, each consisting of three scaffolds corresponding to the three chromosomes in each species. These assemblies indicate that almost all genomic rearrangements among these species occur within, rather than between, chromosome arms. The genome assembly procedure we describe is fast, inexpensive, and accurate, and can be applied to many species.

Insecticide Resistance in Mosquitoes: Impact, Mechanisms, and Research Directions

Abstract: Mosquito-borne diseases, the most well known of which is malaria, are among the leading causes of human deaths worldwide. Vector control is a very important part of the global strategy for management of mosquito-associated diseases, and insecticide application is the most important component in this effort. However, mosquito-borne diseases are now resurgent, largely because of the insecticide resistance that has developed in mosquito vectors and the drug resistance of pathogens. A large number of studies have shown that multiple, complex resistance mechanisms—in particular, increased metabolic detoxification of insecticides and decreased sensitivity of the target proteins—or genes are likely responsible for insecticide resistance. Gene overexpression and amplification, and mutations in protein-coding-gene regions, have frequently been implicated as well. However, no comprehensive understanding of the resistance mechanisms or regulation involved has yet been developed. This article reviews current knowledg...