Chemosensory receptor annotation and characterization in Aedes albopictus

Chemoreception in insects is modulated by receptors expressed in sensory neurons that detect chemical cues in the environment, allowing insects to make sense of the world around them. The chemosensory machinery of the Asian tiger mosquito, Aedes albopictus, has been relatively understudied when considering its role as a competent disease vector and incredibly potent invasive species. Some of the greatest gaps in our current knowledge of Ae. albopictus chemosensation consist of the protein sequence for chemoreceptors, which of these receptors are expressed in different tissues, and what chemicals activate these receptors to modulate mosquito behavior. The present studies attempt to fill in these gaps. The first study consists of a complete manual reannotation of the Ae. albopictus chemosensory genome, including odorant receptors, ionotropic receptors, gustatory receptors and odorant binding proteins. In addition, this study attempts to quantify expression of genes in the tarsal segments and labellum of Ae. albopictus through an RNA sequencing experiment. These appendages appear to specialize in contact chemosensation due to the high concentrations of gustatory receptor transcripts present in our RNA sequencing dataset. The second study presented here is the deorphanization of an ionotropic carboxylic acid receptor using an odorant response assay in a heterologous cell system. This receptor, AalbIR75e, is potently activated by nonanoic acid in a concentration-dependent manner. The role of carboxylic acids in mosquito host-seeking behavior is well documented, therefore AalbIR75e may play a role in modulating blood feeding. The reannotation of the Ae. albopictus genome and deorphanization of AalbIR75e should serve as a foundation for future functional and behavioral studies of Ae. albopictus chemosensation.