The Toll-like receptor 5 (TLR5) recognizes flagellin of Gram-positive and -negative bacteria and plays an important role in the host defense system. Here, we surveyed single nucleotide polymorphisms (SNPs) in the coding sequence of the porcine TLR5 gene in 83 individuals from five pig breeds, these including Chinese local populations and Western commercial pig breeds. A total of 19 medium polymorphic SNPs (0.25 < PIC < 0.5) were identified, three of which were missense mutations that clustered within the extracellular domain of TLR5. One of the non-synonymous SNPs fell within a 228-amino acid region which has been shown to be important for flagellin recognition. Four SNPs were only found with high frequencies in Oriental pig breeds. The 19 SNPs were found in 30 haplotypes, one of which segregated at high frequency in all samples. Compared with Western pig breeds, Chinese local populations had higher genetic diversity and more haplotypes. Tajima’s test showed no evidence for deviation from neutrality. The data provide useful information for future genetic marker characterization by means of disease association analysis and/or stimulating the mutation carrier with relevant ligands.

Toll-like receptor 4 (TLR4) plays an important role in immune response and the polymorphism in it might affect protein signaling and host resistance/susceptibility to disease. This study was designed to characterize the functional relevance of 3 nonsynonymous single nucleotide polymorphisms (SNPs), c.611 T>A (p.Leu204His), c.1027 C>A (p.Gln343Lys), and c.1605 G>T (p.Leu535Phe), which were selected based on our previous studies. RT-PCR method was used to clone the complete coding sequence of porcine TLR4 gene and the PCR-based method was used to introduce the point mutation. The effects of 3 SNPs on the ligand recognition and signaling of porcine TLR4 were investigated in transiently transfected PK-15 cells using dual-luciferase reporter system and Western blotting method. At the same time, the distribution of c.1605 G>T among pig populations composed of Min pig, Yorkshire, Landrace, and Wild boar from northeastern China was studied by created restriction site PCR-RFLP method. The complete coding sequence of TLR4 gene in Min pig and 3 variants with single point mutations were obtained. Eukaryotic expression vectors containing different alleles of porcine TLR4 were constructed. SNP c.1605 G>T significantly decreased the TLR4 signaling (P<0.01) and the polymorphism only existed in Min pig and Wild boar from northeastern China with high frequencies. SNP c.1605 G>T in porcine TLR4 might affect the receptor function and host resistance/susceptibility to diseases.