title: Divergent and conserved elements comprise the chemoreceptive repertoire of the nonblood-feeding mosquito Toxorhynchites amboinensis.
abstract: Many mosquito species serve as vectors of diseases such as malaria and yellow fever, wherein pathogen transmission is tightly associated with the reproductive requirement of taking vertebrate blood meals. Toxorhynchites is one of only three known mosquito genera that does not host-seek and initiates egg development in the absence of a blood-derived protein bolus. These remarkable differences make Toxorhynchites an attractive comparative reference for understanding mosquito chemosensation as it pertains to host-seeking. We performed deep transcriptome profiling of adult female Toxorhynchites amboinensis bodies, antennae and maxillary palps, and identified 25,084 protein-coding "genes" in the de novo assembly. Phylogenomic analysis of 4,266 single-copy "genes" from T. amboinensis, Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus robustly supported Ae. aegypti as the closest relative of T. amboinensis, with the two species diverged approximately 40 Ma. We identified a large number of T. amboinensis chemosensory "genes," the majority of which have orthologs in other mosquitoes. Finally, cross-species expression analyses indicated that patterns of chemoreceptor transcript abundance were very similar for chemoreceptors that are conserved between T. amboinensis and Ae. aegypti, whereas T. amboinensis appeared deficient in the variety of expressed, lineage-specific chemoreceptors. Our transcriptome assembly of T. amboinensis represents the first comprehensive genomic resource for a nonblood-feeding mosquito and establishes a foundation for future comparative studies of blood-feeding and nonblood-feeding mosquitoes. We hypothesize that chemosensory genes that display discrete patterns of evolution and abundance between T. amboinensis and blood-feeding mosquitoes are likely to play critical roles in host-seeking and hence the vectorial capacity.
authors.affiliation: Department of Biological Sciences, Vanderbilt University.
authors.forename: Xiaofan
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Center for Human Genetics Research, Vanderbilt University Medical Center, Nashville, Tennessee.
authors.forename: David C
authors.initials: DC
authors.lastname: Rinker
authors.affiliation: Department of Biological Sciences, Vanderbilt University Vanderbilt Institute for Global Health, Vanderbilt University Medical Center, Nashville, Tennessee.
authors.forename: Ronald Jason
authors.initials: RJ
authors.lastname: Pitts
authors.affiliation: Department of Biological Sciences, Vanderbilt University Center for Human Genetics Research, Vanderbilt University Medical Center, Nashville, Tennessee.
authors.forename: Antonis
authors.initials: A
authors.lastname: Rokas
authors.affiliation: Department of Biological Sciences, Vanderbilt University Center for Human Genetics Research, Vanderbilt University Medical Center, Nashville, Tennessee Vanderbilt Institute for Global Health, Vanderbilt University Medical Center, Nashville, Tennessee Department of Pharmacology, Vanderbilt Brain Institute, Program in Developmental Biology and Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, Tennessee l.zwiebel@vanderbilt.edu.
authors.forename: Laurence J
authors.initials: LJ
authors.lastname: Zwiebel
mesh_terms: D000818:Animals; D009033:Culicidae / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D059467:Transcriptome / Q000235:genetics
keywords: RNA-seq; Toxorhynchites; blood feeding; chemical ecology; chemosensation; chemosensory receptor; disease vector; host-seeking; mosquito; transcriptome