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An insight into the sialotranscriptome of the West Nile mosquito vector, Culex tarsalis.

Calvo E, Sanchez-Vargas I, Favreau AJ, Barbian KD, Pham VM, Olson KE, Ribeiro JM - BMC Genomics (2010)

Bottom Line: Comparison of the C. tarsalis sialotranscriptome with that of C. quinquefasciatus reveals accelerated evolution of salivary proteins as compared to 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: 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.

ABSTRACT

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.

Conclusion: 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.

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Phylogram of the 30 kD/GE rich/Aegyptin protein family of mosquitoes. The numbers on the tree nodes represent the percent bootstrap support in 10,000 trials. The bar at the bottom indicates 20% amino acid divergence. The Culex tarsalis sequences are named Ctar-XXX where the XXX represents the cluster number that originated it. The remaining sequences are named in a five letter followed by number format where the 3 first letters represent the 3 first letters of the genus, followed by the first 2 letters of the species binomial name. The number represents the NCBI gi/ access. For more details, see text.
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Figure 3: Phylogram of the 30 kD/GE rich/Aegyptin protein family of mosquitoes. The numbers on the tree nodes represent the percent bootstrap support in 10,000 trials. The bar at the bottom indicates 20% amino acid divergence. The Culex tarsalis sequences are named Ctar-XXX where the XXX represents the cluster number that originated it. The remaining sequences are named in a five letter followed by number format where the 3 first letters represent the 3 first letters of the genus, followed by the first 2 letters of the species binomial name. The number represents the NCBI gi/ access. For more details, see text.

Mentions: The sialotranscriptome of C. tarsalis allowed the identification of 8 protein sequences from the 30 kDa antigen/Aegyptin family (Additional file 2, Table S2), all represented by 1-10 ESTs found in the library. Blast searches against the NR database retrieved closely related sequences. Those that were more than 95% identical and of the same species were excluded to avoid inclusion of alleles or very closely related genes. Clustal alignment of this subset was used to produce a bootstrapped phylogram (Fig 3) that allows the following inferences: The 8 proteins from C. tarsalis most probably derive from 3 genes, Ctar-49, Ctar-50 and Ctar-51 being probable alleles of a gene closely related to a C. quinquefasciatus salivary gene shown in Clade I. Clade I includes Aedes aegypti salivary proteins that are short versions of the canonical 30 kDa protein, as are all Culex proteins in this clade. A second C. tarsalis gene possibly codes for Ctar-103, Ctar-104 and Ctar-105, and a third gene for Ctar-55 and Ctar-57. These two gene products groups with strong bootstrap support to their C. quinquefasciatus homologs, and these in turn group relatively weakly (48% bootstrap support) in Clade II as shown in Fig 3. Fig 3 also shows the uniquely Aedes containing proteins in clade III, represented by pairs of homologs between Ae. aegypti and Ae. albopictus, and the uniquely anopheline clade IV, with one sequence each of 5 different mosquito species. This phylogram suggests the single gene status of this family in the Anopheles genus, and the multi gene character in Culicines. At least 3 genes for canonical 30 kDa Ag/Aegyptin exists in the Aedes genus, and at least one more gene for the shorter protein shown in Clade I. Culex also have the shorter version gene, plus at least 2 genes of the canonical type.


An insight into the sialotranscriptome of the West Nile mosquito vector, Culex tarsalis.

Calvo E, Sanchez-Vargas I, Favreau AJ, Barbian KD, Pham VM, Olson KE, Ribeiro JM - BMC Genomics (2010)

Phylogram of the 30 kD/GE rich/Aegyptin protein family of mosquitoes. The numbers on the tree nodes represent the percent bootstrap support in 10,000 trials. The bar at the bottom indicates 20% amino acid divergence. The Culex tarsalis sequences are named Ctar-XXX where the XXX represents the cluster number that originated it. The remaining sequences are named in a five letter followed by number format where the 3 first letters represent the 3 first letters of the genus, followed by the first 2 letters of the species binomial name. The number represents the NCBI gi/ access. For more details, see text.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2823692&req=5

Figure 3: Phylogram of the 30 kD/GE rich/Aegyptin protein family of mosquitoes. The numbers on the tree nodes represent the percent bootstrap support in 10,000 trials. The bar at the bottom indicates 20% amino acid divergence. The Culex tarsalis sequences are named Ctar-XXX where the XXX represents the cluster number that originated it. The remaining sequences are named in a five letter followed by number format where the 3 first letters represent the 3 first letters of the genus, followed by the first 2 letters of the species binomial name. The number represents the NCBI gi/ access. For more details, see text.
Mentions: The sialotranscriptome of C. tarsalis allowed the identification of 8 protein sequences from the 30 kDa antigen/Aegyptin family (Additional file 2, Table S2), all represented by 1-10 ESTs found in the library. Blast searches against the NR database retrieved closely related sequences. Those that were more than 95% identical and of the same species were excluded to avoid inclusion of alleles or very closely related genes. Clustal alignment of this subset was used to produce a bootstrapped phylogram (Fig 3) that allows the following inferences: The 8 proteins from C. tarsalis most probably derive from 3 genes, Ctar-49, Ctar-50 and Ctar-51 being probable alleles of a gene closely related to a C. quinquefasciatus salivary gene shown in Clade I. Clade I includes Aedes aegypti salivary proteins that are short versions of the canonical 30 kDa protein, as are all Culex proteins in this clade. A second C. tarsalis gene possibly codes for Ctar-103, Ctar-104 and Ctar-105, and a third gene for Ctar-55 and Ctar-57. These two gene products groups with strong bootstrap support to their C. quinquefasciatus homologs, and these in turn group relatively weakly (48% bootstrap support) in Clade II as shown in Fig 3. Fig 3 also shows the uniquely Aedes containing proteins in clade III, represented by pairs of homologs between Ae. aegypti and Ae. albopictus, and the uniquely anopheline clade IV, with one sequence each of 5 different mosquito species. This phylogram suggests the single gene status of this family in the Anopheles genus, and the multi gene character in Culicines. At least 3 genes for canonical 30 kDa Ag/Aegyptin exists in the Aedes genus, and at least one more gene for the shorter protein shown in Clade I. Culex also have the shorter version gene, plus at least 2 genes of the canonical type.

Bottom Line: Comparison of the C. tarsalis sialotranscriptome with that of C. quinquefasciatus reveals accelerated evolution of salivary proteins as compared to 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: 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.

ABSTRACT

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.

Conclusion: 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.

Show MeSH
Related in: MedlinePlus