Identification and functional characterization of olfactory indolergic receptors in Musca domestica

In mosquitoes, indolic compounds are detected by a group of olfactory indolergic Odorant Receptors (indolORs). The ancient origin of indole and 3-methylindole as chemical signals suggest that they may be detected by insects outside the Culicidae clade. To test this hypothesis, we have identified potential indolOR genes in brachyceran flies based on sequence homology. Because of the crucial roles of indolic compounds in oviposition and foraging, we have focused our attention on the housefly Musca domestica. Using a heterologous expression system, we have identified indolOR transcript expression in the female antennae, and have characterized MdomOR30a and MdomOR49b as 3-methylindole and indole receptors, respectively. We have identified a set of 92 putative indolOR genes encoded in the genomes of Culicoidea, Psychodidae and brachycera, described their phylogenetic relationships, and exon/intron structures. Further characterization of indolORs will impact our understanding of insect chemical ecology and will provide targets for the development of novel odor-based tools that can be integrated into existing vector surveillance and control programs.