Detection And Analysis Of Candidate Genes Polymorphisms For Prolificacy In Fine-wool Sheep

The breeding of Prolific fine-wool sheep is the key direction of fine-wool sheep industry development in China.Enhancing the prolificacy of fine-wool sheep is the most important point in the breeding at present,but the genes that control Prolific traits of fine-wool sheep are still unclear.In this study,Alpine Merino sheep,Chinese Merino sheep,Qinghai fine-wool sheep and Aohan fine-wool sheep were selected as the research objects.BMPR-IB,BMP15,GDF9,FSHR,FSH?,INHA,INHBA,GnRHR and GnRH were selected as candidate genes for prolificacy of fine-wool sheep.Based on genome-wide sequencing results,single nucleotide polymorphisms of exons were screened,and the effects of single nucleotide polymorphisms on the secondary structure of candidate genes were predicted by RNAfold and NPS@ software.The amino acid mutation site of the candidate gene of Alpine Merino sheep was selected as the specific candidate site of the gene,the polymorphism of Alpine Merino sheep was detected by direct sequencing method,and the correlation between candidate genes polymorphisms and litter size was analyzed,and the genes affecting prolificacy were screened.The main results were as follows:1.Five SNPs(A753G,T1020 C,C1035T,C1269 A,C1626A)were detected in the exons of BMPRIB gene.No SNP sites were detected on the exon of BMP15 gene.A total of 7 SNPs(G260A,C471 T,G477A,G721 A,G750A,A978 G,G994A)were detected in the exons of GDF9 gene.Seven SNPs(G149A,G813 A,T817C,T904 G,C975T,T1234 C,G1572A)were detected in FSHR exons.Three SNPs(C64T,C142 G,C202T)were detected on the exon of FSH gene.Three SNPs(T206A,T387 A and G900A)were detected on the exon of INHA gene.Four SNPs(C107A,G405 A,C411T,A1245G)were detected on the exon of INHBA gene.Five SNPs(C22T,C289 T,C411T,C720 G,T814C)were detected on the exon of GnRHR gene.Two SNPs(C1631T and A1632G)were detected on the exon of GnRH gene.In this study,the genotype frequency,gene frequency and population polymorphism information content of candidate gene mutation sites were analyzed,which provided reference materials for the subsequent breeding to improve the accumulation of mutants and the elimination of unfavorable genes.2.Bioinformatics analysis of SNPs loci of 9 prolific trait genes in four sheep breeds revealed that all SNPs in BMPR-IB,GDF9,FSH? and INHA genes,the C107 A mutation in INHBA gene,3 SNPs in GnRHR gene(C22T,C720 G,T814C),and the C1631 T mutation in GnRH gene can change the RNA secondary structure of the candidate genes,while the rest of the SNPs found in these genes do not change that of the candidate genes.9 candidate gene-encoded proteins were all alpha-proteins,and all missense mutations resulted in changes in the secondary structure of the encoded proteins.3.Correlation analysis between different genotypes of Prolific trait candidate genes mutation loci and litter size in Alpine Merino sheep,the results showed that there was no significant difference in the lambing number among the three SNPs of FSHR gene(T904G,C975 T and G1572A),C107 A of INHBA gene,C720 G of GnRHR gene,C1631 T of GnRH gene and A1632 G of mutation site among different genotypes(p>0.05).The lambing Numbers of BMPR-IB gene T1020 C and INHA gene T206 A were significantly different between different genotypes(p<0.05),and the mean lambing Numbers of heterozygous and mutant homozygous were higher than those of wild type.It was predicted that BMPRIB gene T1020 C and INHA gene T206 A mutant genotypes were the main genes or a closely linked genetic marker controlling multiparous performance of alpine merino sheep.It is predicted that T1020 C and T206 A mutant genotypes of BMPR-IB gene and INHA gene of Alpine Merino sheep are the main genes controlling the prolificacy of alpine Merino sheep or a closely linked genetic marker.Whether SNP loci in exons of candidate genes for Prolific trait affect litter size in other fine-wool sheep needs further experimental verification.This study provides a reference for further exploring the effect of candidate genes for Prolific trait on litter size and breeding to improve reproductive capacity of fine-wool sheep.