No abstract

Toll-like receptors mediate immune responses via recognition of pathogen-associated molecular patterns. Polymorphisms of toll-like receptors may affect their recognition of pathogen-associated molecular patterns, leading to varied host resistance to pathogenic infections. However, little is known about the polymorphisms of chicken toll-like receptors (ChTLR) among breeds. In this study, we cloned ChTLR2 type 1 and type 2 genes from 7 chicken breeds and analyzed their sequences. It was found that there were 10 amino acid polymorphism sites in ChTLR2 type 1 and type 2, among which 6 sites were in type 1 (5 sites in the extracellular domain and 1 site in the cytoplasmic domain) and 4 sites were in type 2 (all 4 sites in the extracellular domain). These results demonstrate that ChTLR2 type 1 and type 2 genes are polymorphic among chicken breeds, suggesting a varied resistance among breeds of chicken. We found that Laiwu Black chicken breeds have distinctive polymorphic sites at I699T in the type 1 and H561R in the type 2 ChTLR2 gene. Beijing Fatty chickens have distinctive sites at Q45R in type 1 and V66L in type 2. Nongda No.3 Chickens have distinctive sites at L115P, H232Y, and T494A in type 1. Hy-Line variety brown chickens have distinctive sites at I311V in type 2. Beijing White 939 chickens have distinctive sites at E284G in type 1 and A22V in type 2. These findings may provide some clues toward understanding the resistance of lighter chickens to salmonellosis.

Toll-like receptors (TLRs) mediate immune responses via the recognition of pathogen-associated molecular patterns (PAMPs), thus playing important roles in host defense. Among the chicken (Ch) TLR family, ChTLR3 and 7 have been shown to recognize viral RNA. In our earlier studies, we have reported polymorphisms of TLR1, 2, 4, 5, 15 and 21. In the present study, we amplified TLR3 and 7 genes from different chicken breeds and analyzed their sequences. We identified 7 amino acid polymorphism sites in ChTLR3 with 6 outer part sites and 1 inner part site, and 4 amino acid polymorphism sites in ChTLR7 with 3 outer part sites and 1 inner part site. These results demonstrate that ChTLR genes are polymorphic among different chicken breeds, suggesting a varied resistance across numerous chicken breeds. This information might help improve chicken health by breeding and vaccination.

Toll-like receptors (TLR) mediate immune responses via the recognition of pathogen-associated molecular patterns, thus playing important roles in host defense. Among the chicken (Ch) TLR family, ChTLR1, 2, 4, 15, and 21 were shown to recognize bacterial components. In our earlier study, we reported polymorphisms of TLR1, 2, and 5. In the present study, we cloned TLR4, 15, and 21 genes from different chicken breeds and analyzed their sequences. We identified 9 amino acid polymorphism sites in ChTLR4 with 8 extracellular domain sites and 1 site in the cytoplasmic domain, 15 amino acid polymorphism sites in ChTLR15 with 14 extracellular domain sites and 1 site in the cytoplasmic domain, and 7 amino acid polymorphism sites in ChTLR21 with 5 extracellular domain sites and 2 sites in the cytoplasmic domain. These results demonstrate that ChTLR genes are polymorphic among different avian breeds, suggesting a varied resistance across numerous chicken breeds. This information might help improve chicken health by breeding and vaccination.

Toll-like receptors (TLRs) mediate immune response via recognition of pathogen-associated molecular patterns (PAMPs), thus play important roles in host defense. Polymorphisms of TLR5 may affect their recognition of bacterial flagellin, leading to varied host resistance to pathogenic infections. Here, we cloned TLR5 genes from Common Pheasant, Guinea fowl and 9 Chicken breeds and analyzed their sequences. The open reading frames of TLR5 were sequenced. Amino acid analysis indicated that TLR5 from Chicken breeds shared 99.4-99.9% homology. The amino acid homology of TLR5 ranged from 92.1 to 92.5% between Chickens and Guinea fowl, 95.7-96.1% between Chickens and Turkey, 94.3-94.7% between Chickens and Common Pheasant, and 79.9-80.1% between Chickens and Zebra-finch. Different genetic patterns were determined among Chickens, Common Pheasant, Guinea fowl, Turkey and Zebra-finch. It was found that there were 92 amino acid polymorphic sites, among which 5 sites in chicken TLR5, 63 sites in Guinea fowl TLR5 and 44 sites in Common Pheasant TLR5. Our data indicate that the positive Darwinian selection occurred in avian TLR5 genes since frequency of non-synonymous (d ( N )) > frequency of synonymous (d ( S )). These results also demonstrate that avian TLR5 genes are polymorphic among avian breeds, suggesting a varied resistance among breeds of avian. This information might be of help to improve the health of avian by breeding and vaccination.