| This study aimed to investigate SNPs (Single Nucleotide Polymorphisms) of SST, SSTR2, RETN gene and evaluate their effects on growth traits and carcass traits in 6 Chinese indigenous cattle breeds, including Qinchuan (QC, n=369 ), Luxi (LX, n=64 ), Luxi×Simental (LS, n=53 ),Nanyang (NY, n=68) and Jiaxianred (JXR, n=73) breeds. PCR–SSCP technology and gene sequencing method was used in order to provide definite theoretic foundation for excellent beef breeding. The main results were as follows: One SNP was detected in SST gene exon 1, none was found in exon 2 and intron 3. One SNP existed in SSTR2 gene exon 1 and none was found in the other sites. In RETN gene one SNP existed in exon 2, no SNP was found in the other exons. The association analysis of different genotypes and growth traits and carcass traits were showed as follows:1. The association between polymorphism of SST gene exon 1 and growth traitsPCR products of SST gene fragment was 234bp, A SNP in the exon 1 region of the SST gene was detected. Three genotypes AA, AG and GG were identified in Luxi breed after PCR-SSCP, but only two genotypes AA and AG were found in the other five brees. Sequencing analysis showed that it's a transversion of G→A at 126-bp, which is a synonymous mutations of glutamine (Gln). Theχ2-test showed that all populations of SST gene locus were at Hardy-Weinberg equilibrium (P > 0.05). Correlation analysis showed that, in Qinchuan breed, individuals with genotype AA had lower body length, hip width, and hucklebone width values compared to AG at 1.5 and 2.5 years old (P<0.05), and also had lower body length, chest circumference and hucklebone width compared to AG at 2 years old (P<0.05), significant difference was found on body length (P<0.01). At 1.5 years old, populations with genotype AA had significantly lower body height than AG individuals (P<0.01). No significant difference was detected in other indexes. In Luxi breed, the index of individuals with genotypes GG was higher than those of AA on body length(P<0.05); While the indexes of individuals with genotypes AG were higher than those of AA on body length and body height in LS cattle(P<0.05). The other indexes between the individuals of the three cattle breeds had no significant difference. 2. Study on the polymorphism and its association with growth traits of SSTR2 gene exon 1Three genotypes GG,GC and CC were identified after PCR-SSCP in exon 1 region of SSTR2 gene in all cattle breeds except Xianan, which has only GG and GC two genotypes. The sequencing results showed that the mutation was in position 339 G>C, which Leads to the change of amino acids from methionine to isoleucine. Correlation analysis showed that, in Qinchuan breed, the index of individuals with genotypes GG were higher than those of GC on body height(P<0.05), genotypes GC were higher than those of CC on hucklebone width (P<0.05). While in Nanyang breed, on body height the individuals with genotypes GG was higher than those of CC(P<0.05). The individuals with genotypes GC was higher than those of CC, which showed a significant difference(P<0.01); The index of individuals with genotypes GG were higher than those of CC on hip width (P<0.05). Differences between the individuals of the other indexes are not observed.3. The polymorphism of RETN gene exon 2 and its association with growth and carcass traits of cattle breedsThrough PCR-SSCP methods, two genotypes TT and TC were identified in exon 2 of RETN gene in Luxi and Luxi×Simmental breeds, three genotypes TT, TC and CC were identified in the other four cattle breeds; Sequencing results showed that one mutation T2528C was existed, which caused the amino acids change from isoleucine to threonine. Allele frequencies, gene heterozygosity, effective allele number and polymorphism information content (PIC) of the bovine RETN SNP in six populations were investigated and calculated by theχ2 test. The distribution of the polymorphism from the studied six bos taurus breeds was not uniform. Our results suggested that all cattle breeds were in Hardy-Weinberg equilibrium. Association analysis showed that, in Qinchuan breed, the individuals with TT genotype were heigher than TC on intramuscular fat content (P<0.05); TT and CC genotypes were associated with a heighten marbling score when compared with the TC genotype (P<0.05), the individuals of TT genotype were heigher than of CC (P<0.05). In Nanyang breed, individuals of TT genotypes were significantly heigher than of CC and TC on waist height (P<0.01), TT genotypes were heigher than CC and TC on rump length (P<0.05). Such associations were not observed on the other breeds and other indexes. |
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