Genotyping of ALDH7A1 and EDNRB2 Genes and Their Association with Skin Blackness in Black-bone Chickens
[Objective]In order to further verify the role of ALDH7A1 and EDNRB2 in melanin deposition in Black-bone chickens,single nucleotide polymorphisms(SNPs)of ALDH7A1 and EDNRB2 genes were genotyped,and the association between polymorphic loci and skin blackness was analyzed,to find out SNP markers that had significant effects on skin blackness.It would provide reference for marker assisted selection breeding of slaughtered Black-bone chickens with higher blackness.[Method]Genotyping of SNPs of ALDH7A1 and EDNRB2 genes in 192 individuals of Silky fowls using time-of-flight mass spectrometry analysis technology.the degree of linkage disequilibrium(LD)of these SNPs were analyzed by HaploView 4.1 software,and the association between different genotypes and haplotypes with skin brightness(L*)values was analyzed.[Result]The mass spectrometry detection rate of two SNPs in ALDH7A1(rs317018616 C＞A(SNP1)and rs15992676 T＞C(SNP2))and two SNPs in EDNRB2 genes(rs739725493 G＞A(SNP3)and rs316614064 C＞T(SNP4))were 100％.There were only two homozygous genotypes at the two SNPs of ALDH7A1 gene,while there were three genotypes at both SNPs of EDNRB2 gene.Chi-square test showed that the two SNPs of ALDH7A1 gene deviated from Hardy-Weinberg equilibrium(P＜0.05),while the two SNPs of EDNRB2 gene were in Hardy-Weinberg equilibrium(P＞0.05).The genetic diversity of SNP1 was low(PIC＜0.25),and the other three SNPs were moderately polymorphic(0.25＜PIC＜0.5).Association analysis showed that there was no significant difference in L*values of the back skin and breast skin among different genotypes of the four SNPs(P＞0.05).The thigh skin L*value of TT genotype at SNP2 was significantly lower than that of CC genotype(P＜0.05).The thigh skin L*values of CC and CT genotypes at SNP4 were significantly lower than that of TT genotype(P＜0.05).There was no significant difference in thigh skin L*values between different genotypes at SNP1 and SNP3(P＞0.05).The analysis of linkage disequilibrium indicated that SNP1 and SNP2 of ALDH7A1 gene were in a strong linkage imbalance state,three haplotypes were generated after SNP1-SNP2 linkage.The thigh skin L*values of AATT and CCTT haplotypes of Black-bone chickens were significantly lower than that of CCCC haplotype(P＜0.05),but there was no significant difference in L* values of the back skin and breast skin among the three haplotypes(P＞0.05).[Conclusion]The ALDH7A1 and EDNRB2 gene were closely related to the thigh skin blackness.The AATT and CCTT haplotypes of ALDH7A1 gene and TT genotype of EDNRB2 gene could be used as a candidate molecular marker for studying the thigh skin blackness in Silky fowls.It would provide a theoretical reference for using molecular marker assisted breeding to accelerate the cultivation of new Silky fowls with higher blackness.
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