An insight into the sialotranscriptome of the West Nile mosquito vector, Culex tarsalis.
BACKGROUND
Saliva of adult female mosquitoes help sugar and blood feeding by providing enzymes and polypeptides that help sugar digestion, control microbial growth and counteract their vertebrate host hemostasis and inflammation. Mosquito saliva also potentiates the transmission of vector borne pathogens, including arboviruses. Culex tarsalis is a bird feeding mosquito vector of West Nile Virus closely related to C. quinquefasciatus, a mosquito relatively recently adapted to feed on humans, and the only mosquito of the genus Culex to have its sialotranscriptome so far described.


RESULTS
A total of 1,753 clones randomly selected from an adult female C. tarsalis salivary glands (SG) cDNA library were sequenced and used to assemble a database that yielded 809 clusters of related sequences, 675 of which were singletons. Primer extension experiments were performed in selected clones to further extend sequence coverage, allowing for the identification of 283 protein sequences, 80 of which code for putative secreted proteins.


CONCLUSIONS
Comparison of the C. tarsalis sialotranscriptome with that of C. quinquefasciatus reveals accelerated evolution of salivary proteins as compared to housekeeping proteins. The average amino acid identity among salivary proteins is 70.1%, while that for housekeeping proteins is 91.2% (P < 0.05), and the codon volatility of secreted proteins is significantly higher than those of housekeeping proteins. Several protein families previously found exclusive of mosquitoes, including only in the Aedes genus have been identified in C. tarsalis. Interestingly, a protein family so far unique to C. quinquefasciatus, with 30 genes, is also found in C. tarsalis, indicating it was not a specific C. quinquefasciatus acquisition in its evolution to optimize mammal blood feeding.
Calvo
Eric
E
Section of Vector Biology, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
Sanchez-Vargas
Irma
I
Favreau
Amanda J
AJ
Barbian
Kent D
KD
Pham
Van M
VM
Olson
Kenneth E
KE
Ribeiro
José Mc
JM
D000595:Amino Acid Sequence; D000818:Animals; D019295:Computational Biology; D003465:Culex / Q000235:genetics*; D019143:Evolution, Molecular; D020224:Expressed Sequence Tags; D005260:Female; D020869:Gene Expression Profiling; D015723:Gene Library; D017344:Genes, Insect; D008969:Molecular Sequence Data; D012469:Salivary Glands / Q000378:metabolism; D012471:Salivary Proteins and Peptides / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D012471:Salivary Proteins and Peptides