Analysis Of Genetic Diversity And Association With Skin Color Of3SNPs In BCDO2Gene For Chinese Indigenous Chicken

Yellow skin and leg are common phenotype in domestic chickens. It is caused by the recessive alleles, which can makes the deposition of beta-carotene in skin, while white skinned chickens carry the dominant allele. β-carotene dioxygenase-2(BCD02) gene is a candidate gene for yellow skin, which encodes an enzyme, β-carotene dioxygenase-2, that asymmetricaly cleaves β-carotene to create colourless apocarotenoids. The study has also reported that yellow skin is caused by one or more cis-acting and tissue-specific regulatory mutations that inhibit epression of BCDO2in skin. And in addition, the study has reported that carotenoids are taken up from the circulation in both genotypes but are degraded by BCDO2in skin from animals carrying the white skin allele (W*W). In our study, choosing the chicken with3kinds of skin color in Chinese as the research objects, we tested the the three SNPs (chr24:6,264,085G<A, named SNP A; chr24:6,273,428A<G, named SNP B; chr24:6,287,900G<A, named SNP C) in BCD02gene which have been reported previously by direct sequencing, and we analyzed the association between the different genotypes, different haplotypes and traits with different skin color. The main results show that:there were obvious differences of the three reported SNPs in3kinds of skin color in its genotype distribution. In white skin and yellow skin, the frequency of the homozygouss was widely distributed, far more than heterozygous genotype frequency, while in black skin chicken, it performanced that the heterozygous genotype frequency were high (except the chr24:6,287,900(G<A)). By the chi-square test, the results showed that the chr24:6,264,085(G<A) and chr24:6,287,900(G<A) were associated with3kinds skin color, but it was not with the chr24:6,273,428(A<G) in black skin chicken. The haplotype analysis showed that there were five haplotyped of the three SNPs. Haplotype Zl, Z2and Z4only existed in white skin chicken, Z1and Z2only existed in yellow skin chicken, and there are distrution of5haplotypes in black skin chicken. The frequency of Z2and Z4were the largest, account for44.86%and38.15%respectively, and others were less than or equal to10%. Z2for yellow skin chicken, Z2and Z4for black skin chicken were the advantage haplotype, and Z1and Z2for white skin chicken. Through the relevance analysis indicated that the Zl and Z2were significantly associated with white skin chicken characters (P<0.05), Z2were with yellow skin and black skin chicken (P<0.05). This showed that the three SNPs in BCDO2genes have different characteristics with different skin color type, and which has the genetic distribution difference.Therefore, this study provided some guidance for BCDO2genes to further study the genetic diversity and variation in chicken.