5'-AMP-activated protein kinase plays an important role in regulating the level of ATP in the presence of metabolic stress. Previous studies revealed that polymorphisms in 5'-AMP-activated protein kinase gamma 3 subunit (PRKAG3) gene are associated with meat quality in pigs. In the present study, single-nucleotide polymorphisms (SNPs) in the 5'-end and exons of chicken PRKAG3 gene were identified with the method of single-strand conformation polymorphism in Hubbard ISA White broiler, Leghorn layer, and three Chinese indigenous chicken breeds, Tibet Chicken, Shouguang Chicken and Beijing Yellow Chicken. Two SNPs in the 5'-end of the gene and 10 SNPs in exons 3, 4, 9 and 11, of which three caused amino acid substitutions, were identified in the PRKAG3 gene of the five chicken breeds. The results will facilitate further study on the association between the mutations of PRKAG3 and chicken meat quality.

ABSTRACT. The mannan-binding lectin gene (MBL) participates as an opsonin in the innate immune system of mammals, and single nucleotide polymorphisms (SNPs) in MBL cause various immune dysfunctions. In this study, we detected SNPs in MBL2 at exon 1 using polymerase chain reaction single-strand conformation polymorphism analysis and DNA sequencing techniques in 825 Chinese Holstein cows. Four new SNPs with various allele frequencies were also found. The g.1164 G>A SNP was predicted to substitute arginine with glutamine at the N-terminus of the cysteine-rich domain. In the collagen-like domain, SNPs g.1197 C>A and g.1198 G>A changed proline to glutamine, whereas SNP g.1207 T>C was identified as a synonymous mutation. Correlation analysis showed that the g.1197 C>A marker was significantly correlated to somatic cell score (SCS), and the g.1164 G>A locus had significant effects on SCS, fat content, and protein content (P < 0.05), suggesting possible roles of these SNPs in the host response against mastitis. Nine haplotypes and nine MBL2 polymorphism and mastitis resistance haplotype pairs corresponding to the loci of the 4 novel SNPs were found in Chinese Holsteins. Haplotype pairs MM, MN, and BQ were correlated with the lowest SCS; MN with the highest protein yield; MM with the highest protein rate, and MN with the highest 305-day milk yield. Thus, MM, MN, and BQ are possible candidates for marker-assisted selection in dairy cattle breeding programs.