The cornerstone of the reverse chemical ecology approach is the identification of
odorant receptors (OR) sensitive to compounds in a large panel of odorants. In this approach, we de-orphanize
ORs and, subsequently, measure behaviors elicited by these
semiochemicals. After that, we evaluate behaviorally active compounds for applications in insect vector management. Intriguingly, multiple
ORs encoded by genes highly expressed in mosquito antennae do not respond to any test odorant. One such case is CquiOR125 from the southern house mosquito, Culex quinquefasciatus Say. To better understand CquiOR125's role in Culex mosquito olfaction, we have cloned a CquiOR125 orthologue in the genome of the
yellow fever mosquito, Aedes aegypti (L.), AaegOR11. Unlike the unresponsive nature of the orthologue in Cx. quinquefasciatus, oocytes co-expressing AaegOR11 and AaegOrco elicited robust responses when challenged with
fenchone,
2,3-dimethylphenol,
3,4-dimethylphenol, 4-methycyclohexanol, and
acetophenone. Interestingly, AaegOR11 responded strongly and equally to (+)- and (-)-
fenchone, with no chiral discrimination. Contrary to reports in the literature,
fenchone did not show any repellency activity against Ae. aegypti or Cx. quinquefasciatus. Laboratory and field tests did not show significant increases in egg captures in cups filled with
fenchone solutions compared to control cups. The second most potent
ligand,
2,3-dimethylphenol, showed repellency activity stronger than that elicited by
DEET at the same dose. We, therefore, concluded that AaegOR11 is a mosquito repellent sensor. It is feasible that CquiOR125 responds to repellents that remain elusive.