Evolution of the Gr family of gustatory and odorant receptors in mosquitoes

The ability to detect chemical information from the environment is of critical importance to insects, whose ecological and evolutionary boundaries typically revolve around taste and smell. Of the receptors involved in chemoperception, the gustatory receptor (Gr) protein family comprises most of the diversity in the insect chemoreceptor superfamily, including within it not only taste receptors, but select olfactory receptors as well. Manual annotation of the Gr family in the genome sequence of the yellow fever mosquito, Aedes aegypti Linnaeus, yielded a total of 114 potential proteins encoded by 79 genes. In the sequenced genome, 23 of these genes and protein isoforms are pseudogenic, leaving 91 putatively functional Grs. Comparison with the set of 76 Grs encoded by 52 genes in the distantly related Anopheles gambiae Giles mosquito revealed 13 new AgGrs encoded by eight genes. Phylogenetic analysis reveals the conservation of carbon dioxide, sugar and several orphan receptors in these two mosquitoes and Drosophila flies. Despite these similarities, most of these Grs are unique to mosquitoes and many are specific to the Aedes or Anopheles lineages, indicating their involvement in mosquito-specific aspects of both gustatory and olfactory perception. In particular, most instances of alternative splicing in orthologous loci appear to have evolved after the culicine-anopheline split ±150 million years ago. Within the Gr family, it has been shown that Gr21a and Gr63 in Drosophila melanogaster Meigen combine to form a functional heterodimer for the perception of carbon dioxide. These genes are highly conserved, along with a paralog of Gr21a, in mosquitoes. We examined the presence of these genes in other insect lineages, and although highly conserved in some lineages (three mosquito species, silk moth and red flour beetle), the data suggest that arthropods likely evolved multiple strategies to confer recognition of carbon dioxide. The forthcoming mosquito Gr gene models will help serve as a necessary starting place for further research, as we expect the continued deorphanization of receptors to lead to novel methods for repelling pests and consequently slowing the spread of vector-borne disease.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Entomology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2012

Author dc:creator

• Kent, Lauren

Contributors dc:contributor

• Robertson, Hugh M.
• Berlocher, Stewart H.
• Berenbaum, May R.
• Hanks, Lawrence M.
• Nardi, James B.

• chemoreceptors
• molecular evolution
• gustatory receptors (Grs)
• mosquito taste

Statement dc:rights

• Copyright 2012 Lauren Bettine Kent

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/31058

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/31058