Research Overview: Rhodopsin Expression in Mosquitoes

Rhodopsins are the G-protein coupled receptors initiating visual transduction. Animal genomes typically contain multiple rhodopsin genes with different spectral properties such that the expression of different rhodopsins in distinct classes of photoreceptor cells provides the basis for color vision. There are 10 predicted rhodopsin genes in both Ae. aegypti and An. gambiae genomes. These are classified into five different groups on the basis of comparison to Drosophila and other invertebrate rhodopsins. These are a long wavelength group (most sensitive to to blue/green light) of five members, the short wavelength (most sensitive to UV/blue light) Aaop9, the UV sensitive Aaop8, and the two poorly characterized groups represented by Aaop10 and the pteropsin Aaop12. This large family of rhodopsins is also present in Culex genomes, suggesting a common use of visual information in the disease-related mosquitoes.

The identification of the photoreceptor cell type expressing each of these rhodopsins is key to understanding the organization of the mosquito retina and the mechanisms involved in the processing of visual information. In the Drosophila retina, there are two major classes of ommatidia distinguished by the pairing of rhodopsin expression in the R7 and R8 cell types. We recently showed that the UV sensitive Aaop8 rhodopsin and a long wavelength sensitive Aaop2-type rhodopsin are expressed in non-overlapping subsets of the Ae. aegypti R7 photoreceptor cells. We followed this work with a second report showing that other rhodopsins are coexpressed in these R7 cells. These studies as well as other unpublished work in the laboratory show the overall pattern of rhodopsin expression in mosquitoes is not as predicted from the Drosophila model. We will use this information to determine the basis of visually mediated behaviors of these insects.