The localization of Culex quinquefascuatus odorant binding protein-1 (CquiOBP1)

Culex quinquefasciatus odorant binding protein-1 (CquiOBP1) is the first odorant binding protein identified from antennae of mosquito Cx. quinquefasciatus, a major vector of human diseases such as filariasis, encephalitis, and West Nile virus. CquiOBP1 binds to mosquito oviposition pheromone (MOP), 6-acetoxy-5-hexadecanolide leading to the assumption that CquiOBP1 plays an important role in the detection of MOP in adult females. However, the distribution of CquiOBP1 in mosquito olfactory organs is still unknown. In this study, recombinant CquiOBP1 was expressed in Escherichia coli and purified by Fast Protein Liquid Chromatography (FPLC) with ion-exchange as well as gel-filtration columns. The purified protein was subsequently used to produce an antibody, which was used to localize the expression of CquiOBP1 by Western blot and immunohistochemistry (IHC). The results showed that CquiOBP1 is expressed in the antennae but not the maxillary palps. At least three types of morphologically distinct trichoid sensilla on the antennae express CquiOBP1 but not grooved pegs. This is the first study to reveal the expression pattern of any OBP in a mosquito species at sensilla level.