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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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The 7.8 kDa family of culicine peptides. A) Clustal alignment. The Culex tarsalis proteins are identified by the square symbol and their Ctar-prefix. The remaining sequences are named with the first three letters from the genus name followed by two letters from the species name and by their NCBI protein accession number. Notice conserved cysteine framework in black background and identical amino acids in yellow or gray background. B) Neighbor Joining bootstrapped phylogram of the alignment in A. The numbers on the branches represent the percent bootstrap support. The bar in the bottom represents 10% amino acid divergence. For more details, see text.
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Figure 5: The 7.8 kDa family of culicine peptides. A) Clustal alignment. The Culex tarsalis proteins are identified by the square symbol and their Ctar-prefix. The remaining sequences are named with the first three letters from the genus name followed by two letters from the species name and by their NCBI protein accession number. Notice conserved cysteine framework in black background and identical amino acids in yellow or gray background. B) Neighbor Joining bootstrapped phylogram of the alignment in A. The numbers on the branches represent the percent bootstrap support. The bar in the bottom represents 10% amino acid divergence. For more details, see text.

Mentions: Ctar-761 codes for a mature peptide of predicted MW = 11.7 kDa and pI = 8.8. It is similar to previously described salivary peptides found in sialotranscriptomes of Ae. aegypti and Ae. albopictus, but not Culex. Psiblast using an inclusion e value of 0.1 (relatively high to compensate for the small size of the sequences) against the NR protein database additionally identifies a salivary peptide previously found in C. quinquefasciatus, annotated as 9.7 kDa salivary peptide. Inclusion of this peptide with the previous to generate the reverse position search model [32] additionally identifies other salivary peptides from C. quinquefasciatus, with convergence of the search and identification of the 6 non redundant peptides with an e value of 8 e-16 or smaller. Alignment of these 6 peptides with Ctar-761 shows that the Aedes sequences are more compact than those from Culex, containing a conserved framework of 6 cysteines, while those of Culex have 2 additional Cys residues (Fig 5a). Only 3 other residues are identical in all sequences, indicating a high evolutionary rate of this peptide family, if they indeed share a common ancestor. The bootstrapped phylogram (Fig 5B) shows 2 robust clades, clade I containing only Aedes sequences in two subclades, each containing a pair of Ae. aegypti or Ae. albopictus sequences. Clade II has 2 sequences from C. quinquefasciatus. Ctar-761 does not cluster with either of the clades, indicating again the possible fast evolutionary rate of this peptide family.


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)

The 7.8 kDa family of culicine peptides. A) Clustal alignment. The Culex tarsalis proteins are identified by the square symbol and their Ctar-prefix. The remaining sequences are named with the first three letters from the genus name followed by two letters from the species name and by their NCBI protein accession number. Notice conserved cysteine framework in black background and identical amino acids in yellow or gray background. B) Neighbor Joining bootstrapped phylogram of the alignment in A. The numbers on the branches represent the percent bootstrap support. The bar in the bottom represents 10% amino acid divergence. For more details, see text.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: The 7.8 kDa family of culicine peptides. A) Clustal alignment. The Culex tarsalis proteins are identified by the square symbol and their Ctar-prefix. The remaining sequences are named with the first three letters from the genus name followed by two letters from the species name and by their NCBI protein accession number. Notice conserved cysteine framework in black background and identical amino acids in yellow or gray background. B) Neighbor Joining bootstrapped phylogram of the alignment in A. The numbers on the branches represent the percent bootstrap support. The bar in the bottom represents 10% amino acid divergence. For more details, see text.
Mentions: Ctar-761 codes for a mature peptide of predicted MW = 11.7 kDa and pI = 8.8. It is similar to previously described salivary peptides found in sialotranscriptomes of Ae. aegypti and Ae. albopictus, but not Culex. Psiblast using an inclusion e value of 0.1 (relatively high to compensate for the small size of the sequences) against the NR protein database additionally identifies a salivary peptide previously found in C. quinquefasciatus, annotated as 9.7 kDa salivary peptide. Inclusion of this peptide with the previous to generate the reverse position search model [32] additionally identifies other salivary peptides from C. quinquefasciatus, with convergence of the search and identification of the 6 non redundant peptides with an e value of 8 e-16 or smaller. Alignment of these 6 peptides with Ctar-761 shows that the Aedes sequences are more compact than those from Culex, containing a conserved framework of 6 cysteines, while those of Culex have 2 additional Cys residues (Fig 5a). Only 3 other residues are identical in all sequences, indicating a high evolutionary rate of this peptide family, if they indeed share a common ancestor. The bootstrapped phylogram (Fig 5B) shows 2 robust clades, clade I containing only Aedes sequences in two subclades, each containing a pair of Ae. aegypti or Ae. albopictus sequences. Clade II has 2 sequences from C. quinquefasciatus. Ctar-761 does not cluster with either of the clades, indicating again the possible fast evolutionary rate of this peptide family.

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