Purpose To clarify the genetic polymorphisms of gayal and yak gastric LYZ c gene and their adaptive evolution to digestion in the acid environment of stomach.
Methods The variations in the complete coding region of gastric LYZ c gene were detected in 35 gayal and 33 yak samples by adopting the technique of PCR product direct sequencing in this study. Combined with published homologous sequences of some bovine species, the adaptive analysis of digestive function was further conducted by the methods of comparative genomics and bioinformatics.
Results A total of 6 SNP sites were found in gayal, namely c.196G>A, c.267T>C, c.270C>T, c.396C>T, c.423C>T and c.438C>G, respectively. And 10 SNP sites were found in yak. Except 6 of which were shared with gayal, others viz. c.336G>C, c.348T>G, c.351T>C and c.375A>C were only found for yak. The SNP sites found in gayal were all shared with that of yak. The SNP196 and SNP328 were non-synonymous substitution, which result in p.G66S and p.H116Q amino acid changes. These two substitutions were presumed to have no effect on the function of stomach LYZ c. Based on the variations in gayal and yak gastricLYZ c gene, 6 haplotypes were defined in gayal from which 2 protein variants were identified in gayal, namly Gayal 1 and Gayal 2. And 12 haplotypes were defined in yak from which 3 protein variants were identified in yak, namly Yak 1−Yak 3. Among them, variant Gayal 1 and Yak 3, Gayal 2 and Yak 1 were identical, and Yak 3 is unique to yak. The amino acid compositions, physiochemical properties and structures of the gayal, yak and cattle variants are basically the same. The above characteristics of gayal and yak gastric LYZ c are very similar to those of cattle, but the isoelectric points of gayal and yak gastric LYZ c are lower than that of cattle S3.
Conclusion The results of this study indicate that gayal and yak gastric LYZ c is more suitable for the acid environment of the stomach, and it has the function of breaking down the microbes in the stomach.
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