Molecular Characterization Of DRA, TLR1, TLR2 And TLR5-9 Genes Of Yak In Gansu

To establish and provide baseline information for marker-assisted selection and breeding to enhance disease-resistance of yak, a few genes belong to MHC and TLR families including DRA, TLR1, TLR2 and TLR5-9 were studied in both Gannan yak and Tianzhu White yak in Gansu province of China. These genes are vital for immune response and immunological recognition. Different nucletic acid sequences and predicted amino acid sequences were analysed and characterized using direct sequencing, comparative genomics and bioinformatics methods and tools. The major conclusions are as follows:1. In this study, five Bogr-DRA alleles were identified: BoLA-DRA*01011, BoLA-DRA*01013, BoLA-DRA*01014, Bogr-DRA*01015 and Bogr-DRA*01021. Bogr-DRA*01015 was a noval allele, but the remaining four alleles were shared among bovine species.2. BoLA-DRA*01011 was predominant in both Gannan yak and Tianzhu White yak with frequencies at 0.64 and 0.68, respectively. BoLA-DRA*01014 and Bogr-DRA*01015 were found in Gannan yak, whereas the remaining two alleles were present in both breeds at very low frequencies.3. DRA gene was polymorphic within the yak but highly conserved across different bovine species.4. In a total of 23,198 bp long sequences of the seven TLR genes in Gannan yak and Tianzhu White yak, 39 single-nucleotide polymorphisms (SNPs) were identified at an average of 1 SNP in every 591 bp, of which 29 were transitions and 10 transvertions with a transition to transvertion ratio as 2.9.5. Six different haplotypes determined by four SNPs were identified in TLR1, seven haplotypes determined by four SNPs in TLR2, eleven haplotypes determined by six SNPs in TLR5, three haplotypes determined by two SNPs in TLR6, eight haplotypes determined by seven SNPs in TLR7, four haplotypes determined by three SNPs in TLR8, and five haplotypes determined by five SNPs in TLR9.6. TLR1, TLR2, TLR5, TLR7, TLR8 and TLR9 proteins'secondary structures consist of major alpha helix and random coil plus minor beta strand and beta turn.7. TLR1, TLR2, TLR5, TLR7, TLR8 and TLR9 proteins have signal peptides including amino acid residues ranging from 20 to 34.8. TLR1, TLR2, TLR5, TLR7, TLR8 and TLR9 proteins are trans-membrane proteins and rich in LRR in the extracellular regions.