Effect of light and dark adaptation on Op1 rhodopsin movement of Aedes aegypti

Dengue and yellow fever are diseases transmitted by Aedes aegypti.  Rhodopsins, key mediators in visual perception, will broaden our knowledge on mosquito behavior. Our laboratory determined that Opsin1 is the major rhodopsin expressed in all the R1-R6 photoreceptor cells of the retina. My study investigates the movement of Op1 under light and dark conditions.  Mosquitoes were treated to different hourly cycles of alternating dark and light conditions. The localization of Op1 was studied in whole mounts where the retinas were stained with an antibody to the C-terminus of Op1. Results indicate that Op1 is generally localized to the fused rhabdom in dark conditions and in cytoplasmic vesicles and multivesicular bodies in the light. This pattern is not always consistent because we sometimes find cytoplasmic localization of Op1 in dark samples. A protein blot comparing A. aegypti heads at several of the five cycle light-dark treatments revealed that the amount of Op1 protein is not dramatically different at each time point. When probed with an anti-ubiquitin antibody, however, a higher concentration of a 60kD complex known to be the opsin-ubiquitin complex was found in the light samples in which Op1 is present in the cytoplasm. These data suggest that there is a mechanism that alters the movement of Op1 and the sensitivity of the photoreceptors to different light conditions. These results show that even though A. aegypti is classified as diurnal with respect to their host seeking activity, their Op1 photoreceptors are highly sensitized for performance in dim light.