An Odorant Receptor from the Southern House Mosquito Culex pipiens quinquefasciatus Sensitive to Oviposition Attractants

Abstract

BackgroundInsect odorant receptors (ORs) are heteromers comprised of highly variable odorant-binding subunits associated with one conserved co-receptor. They are potential molecular targets for the development of novel mosquito attractants and repellents. ORs have been identified in the malaria mosquito, Anopheles gambiae, and in the yellow fever mosquito, Aedes aegypti. However, they are still unknown in the Southern house mosquito, Culex quinquefasciatus, which transmits pathogens that cause human diseases throughout the world, including West Nile Virus in the United States.MethodologyWe have employed a combination of bioinformatics, molecular cloning and electrophysiology approaches to identify and characterize the response profile of an OR in Cx. quinquefasciatus. First, we have unveiled a large multigenic family of one-hundred-fifty-eight putative ORs in this species, including a subgroup of conserved ORs in three mosquito species. Using the Xenopus oocytes expression system, we have determined the response profile of CquiOR2, an antennae-specific OR, which shares high identity with putative orthologs in Anopheles gambiae (AgamOR2) and Aedes aegypti (AaegOR2).ConclusionWe show that CquiOR2 is highly sensitive to indole, an oviposition attractant for Cx. quinquefasciatus. The response profile of CquiOR2 expressed in Xenopus oocytes resembles that of an olfactory receptor neuron housed in the antennal short blunt-tipped sensilla (A2) of Cx. quinquefasciatus, which are natural detectors for oviposition attractants. This first Culex OR de-orphanized is, therefore, a potential molecular target for screening oviposition attractants.

Mosquito odorant receptor for DEET and methyl jasmonate

“…We cloned the other seven putative ORs, CquiOR55, CquiOR64, CquiOR93, CquiOR125, CquiOR132, CquiOR136, and CquiOR151. We screened them for a DEET receptor by using the Xenopus oocyte recording system, as previously done to deorphanize multiple Culex ORs (9,(14)(15)(16)(17). CquiOR136•CquiOrco-expressing oocytes were mainly activated by DEET, PMD, IR3535, picaridin, and two other repellents, γ-octalactone and 3-octanol ( Fig.…”

Differential expression of olfactory genes in the southern house mosquito and insights into unique odorant receptor gene isoforms

“…We now know that the major peripheral olfactory proteins involved in the reception of odorants in insects are the odorant-binding proteins (OBPs), chemosensory proteins (CSPs), odorant-degrading enzymes (ODEs), odorant receptors (ORs), ionotropic receptors (IRs), and sensory neuron membrane proteins (SNMPs) (4). The southern house mosquito may possess one of the most, if not the most, acute olfactory system in mosquitoes (3) and has the largest repertoire of putative odorant receptors (ORs) of all dipteran species whose genomes have been hitherto sequenced (5)(6)(7). Given the diversity of olfactory genes involved in reception of semiochemicals, our understanding of the molecular basis of olfaction heavily depends on genomic data.…”

Crystal and solution structures of an odorant-binding protein from the southern house mosquito complexed with an oviposition pheromone

“…Effective management of Culex mosquito populations may be achieved with oviposition attractants and other kairomones (3,4), because larval development is a particularly vulnerable point in their life cycle. These semiochemicals are detected by the antennae of female adults with sensilla housing odorant receptors (ORs) (5,6) and odorant-binding proteins (OBPs) (7)(8)(9), and these molecular targets can be used in reverse chemical ecology approaches (10) for the development of green chemistry-based strategies for insect vector management (8). Previously, we have isolated an OBP from the antennae of C. quinquefasciatus, CquiOBP1, which is highly expressed in trichoid sensilla involved in the detection of a mosquito oviposition pheromone (8), (5R,6S)-6-acetoxy-5-hexadecanolide (11) (hereafter referred to as MOP).…”