Identification of Avian Toll-Like Receptor 3 and 7 and Analysis of Gene Variation Sites

ABSTRACT

Toll-like receptors 3 and 7 (TLR3 and 7) mediate immune responses through the recognition of viral single-stranded RNA and double-stranded RNA and therefore play important roles in host defense. Differences in TLR3 or 7 may affect host resistance to RNA viral infection. To illuminate these differences, the partial coding sequence (CDS) of TLR3 and 7 genes were cloned and amplified from the Phasianus colchicus and Numida meleagris, total 64 avian species of TLR3 and 7 sequences were later analyzed. Based on the results, 315 non-synonymous mutation sites and 202 synonymous mutation sites were also observed in the avian TLR3, and 227 non-synonymous mutation sites and 174 synonymous mutation sites were observed in the avian TLR7. Among these sites, 44 and 45 sites were observed in functional regions of TLR3 and 7, used common variation of amino acids in most avian species. A number of these different sites appeared to affect the recognition and were also visualized. H59Y, E60K, G64R, E93K, L112S, K117E, N118K, R120H, V123M, L163F, R443Q, R459K, E460D, C485H, and F511L for TLR3, and I432V, M437V, and T732S for TLR7 were considered. It is possible that these sites bind to ligands and play crucial roles in viral recognition. These data indicated that the positive selection has occurred in the avian TLR3 and 7 genes.

Keywords:
Avian, Evolution; Numida Meleagris; Phasianus colchicus; Toll-Like Receptor (TLR)