Comparative Genomics of Odorant Binding Proteins in Anopheles gambiae, Aedes aegypti, and Culex quinquefasciatus

About 1 million people in the world die each year from diseases spread by mosquitoes, and understanding the mechanism of host identification by the mosquitoes through olfaction is at stake. The role of odorant binding proteins (OBPs) in the primary molecular events of olfaction in mosquitoes is becoming an important focus of biological research in this area. Here, we present a comprehensive comparative genomics study of OBPs in the three disease-transmitting mosquito species Anopheles gambiae, Aedes aegypti, and Culex quinquefasciatus starting with the identification of 110 new OBPs in these three genomes. We have characterized their genomic distribution and orthologous and phylogenetic relationships. The diversity and expansion observed with respect to the Aedes and Culex genomes suggests that the OBP gene family acquired functional diversity concurrently with functional constraints posed on these two species. Sequences with unique features have been characterized such as the "two-domain OBPs" (previously known as Atypical OBPs) and "MinusC OBPs" in mosquito genomes. The extensive comparative genomics featured in this work hence provides useful primary insights into the role of OBPs in the molecular adaptations of mosquito olfactory system and could provide more clues for the identification of potential targets for insect repellants and attractants.