Differential expression of antennal chemosensory genes related to host preference of Culex pipiens biotypes

The northern house mosquito, Culex pipiens, is a noted arboviral disease vector commonly found throughout Europe and North America. Two morphologically identical biotypes of this species, Culex pipiens pipiens and Culex pipiens molestus, display differential host preference to birds and humans, respectively; however, little is known about the genetic mechanisms regulating this behavior.

Using a Y-tube olfactometer, the host preference of the host-seeking female mosquitoes of both biotypes was tested by providing a choice between synthetic chicken and human odor blends, across 2 days of testing. Antennal transcriptomes, from the mosquitoes that demonstrated a clear and consistent preference to either of the odor blends, were created to observe differences in antennal chemosensory gene expression.

In the host preference experiments, Cx. pipiens pipiens and Cx. pipiens molestus demonstrated a weak, but significant, preference to the synthetic chicken and human odor blends, respectively, when tested across multiple days. The transcriptome created from the antennae of mosquitoes that made a consistent choice over 2 days of testing identified 9 odorant receptors, 3 ionotropic receptors, and 12 odorant binding proteins, and other chemosensory genes, that were differentially expressed between the two biotypes, which correlate with the observed differential host preference.

This study identified a set of chemosensory genes that are putatively correlated with the differential host preference of the two biotypes. Future research is required to increase the understanding of the function of the identified chemosensory receptors, and how they can be used as genetic markers of host preference of wild mosquitoes.