Sequence variation of TYR exon 1 and origin of pigs

To investigate the origin and genetic diversity of domestic pigs, the porcine TYR exon 1 in 36 individuals from 12 Chinese indigenous breeds, three European breeds, eight Chinese wild boars and two Vietnamese wild boars was sequenced. Sequence analysis revealed six synonymous mutations, and all the sequences could be sorted into 4 haplotypes. Combining with the published sequences, we constructed a reduced median network (RM network), in which TYR*2 was a haplotype dominated by European domestic pigs and wild boars, plus only three chromosomes from Asian pigs. Most Asian domestic pigs and wild boars shared haplotype TYR*1,demonstrating that TYR*1 was an Asian specific haplotype. Meanwhile, some European domestic pigs and wild boars carried the haplotype TYR*1. TYR*3 and TYR*4 were two haplotypes with low frequencies, containing mainly Chinese indigenous pigs and Asian wild boars, plus some European domestic pigs. Independent domestication of pigs from Asia and Europe was supported by the pattern of RM network. The European commercial breeds had been suffered from introgression from Chinese pigs, and a few Chinese indigenous breeds and Japanese wild boars were also suffered from introgression from European pigs as well.