Study On The Association Of Three Keratin Associated Protein Genes In Sheep With Wool Traits

Wool is favored by people for its excellent properties such as softness,elasticity,heat insulation,flame retardancy and good air permeability.As is known to all,Merino sheep is a famous fine wool sheep breed.In order to better apply the characteristics of Merino sheep to practical production practices,we can understand the genes that really affect wool traits through the study of woo]molecular breeding.Tan sheep is a native sheep breed of China and it is known for skin.Among them,the "string flower"flower spike type with the tightest bending of the wool stock is the most popular.However,the molecular mechanism of the formation of wool traits in the ’Er-mao’ stage is still unclear,and its genetic basis is poorly understood.Keratin-associated proteins(KAPs)are important proteins,and the expression and variation of their corresponding keratin-associated protein genes(KRTAPs)are related to wool traits.To understand the effect of this gene family on wool traits,MerinoxSouthdown-cross lambs and Tan sheep were used in this study.DNA single-strand conformation polymorphism(SSCP)was used to study the gene variations of KRTAP20-2 sheep,KRTAP28-1 sheep and KRTAP8-1 Tan sheep.The study detected a single nucleotide polymorphism(SNP)c.160 A/T in the sheep KRTAP20-2 coding region.The mutation resulted in a stop codon premature,with 9 amino acid residues missing at the c-terminus of the coding peptide.It was found that the wool fiber of AA sheep had higher mean fiber curvature(MFC)than that of BB sheep by using the General Linear Models(GLMs)analysis.KRTAP28-1 sheep has six alleles of A-F.The A and D allele are associated with a decrease in Mean fiber diameter(MFD),and the C allele is associated with an increase in MFD.Among them,the wool MFD of the AB and BD genotypes is lower than that of the BC genotype.This suggests that KRTAP28-1 affects wool fiber diameter,and the variation of this gene may have the potential to be used as a genetic marker to improve wool fiber diameter.Three(A,D and E)previously identified sheep variations of KRTAP8-1 were detected,but other two(B and C)previously identified variations were not found in Tan sheep.The effects of three genotypes(AA,AE and EE)with genotype frequencies greater than 5%on wool traits were analyzed in six genotypes(AA,AD,AE,DD,DE and EE).The coefficient of variation of fibre diameter(CVFD)of EE genotype was significantly higher than that of AA and AE genotypes.Therefore,changes in KRTAP8-1 affect the fiber uniformity of Tan sheep wool.This study confirmed the potential of the KAP gene as an ideal wool trait gene marker.