ARS | Publication request: Molecular characterization and immunolocalization of the olfactory co-recepter Orco from two blood-feeding muscid flies, the stable fly (Stomoxys calcitrans, L.) and the horn fly (Haematobia irritans irritans, L.)

Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 7, 2012
Publication Date: N/A

Interpretive Summary: Biting flies are economically important, blood-feeding pests of medical and veterinary significance both in the United States and worldwide. Chemosensory-based biting fly behaviors, such as host/nutrient source localization and ovipositional site selection, are intriguing targets for the development of supplemental control strategies that can be utilized in an integrated pest management program. In insects, odors are perceived and converted from a blend of chemicals into an electrical signal to the brain center by way of a complex consisting of a ligand-selective odorant receptor (Or) and a conserved odorant co-receptor (Orco). Many studies in insects have demonstrated that "knocking out" Orco directly affects odor-based behavior, emphasizing how critical Orco is to insect olfaction. In an effort to expand our understanding of biting fly chemosensory pathways, the highly conserved insect odorant co-receptor (Orco) was isolated from two model, biting fly species, the stable fly and the horn fly. This finding lays the foundation to study the functional role of Or-Orco complexes, an approach that may enhance our understanding of how repellents/bait attractants alter the stable fly and horn fly olfactory response.

Technical Abstract: Biting flies are economically important, blood-feeding pests of medical and veterinary significance in the United States and worldwide. Chemosensory-based biting fly behaviors, such as host/nutrient source localization and ovipositional site selection, are intriguing targets for the development of supplemental control strategies that can be utilized in an integrated pest management program. In an effort to expand our understanding of biting fly chemosensory pathways, transcripts encoding the highly conserved insect odorant co-receptor (Orco) were isolated from two representative biting fly species, the stable fly (Scal\Orco) and the horn fly (Hirr\Orco); Orco plays an essential role in formation of a functional insect odorant receptor channel. The biting fly transcripts were predicted to encode proteins with 87% – 94% amino acid similarity to published insect Orco sequences and were detected in various immature stages as well as in adult structures associated with olfaction, i.e., antennae and maxillary palps, and gustation. Further, the relevant proteins were immunolocalized to specific antennal sensilla using anti-serum raised against a peptide sequence conserved between the two fly species. Results from this study provide a basis for functional evaluation of repellent/attractant effects on as yet uncharacterized stable fly and horn fly conventional odorant receptors.