The Relationship Between MC1R Mutation And Plumage Colour Variation In Duck

Plumage color is an important economic trait.It plays an important role in determining breed purity and phylogenesis.Melanocortin Receptor 1(MC 1R) Gene is one of the candidate genes for plumage/coat color in animal.Cloning-sequencing and PCR-SSCP methods were used to analyze the MC1R gene polymorphisms for five variation plumage color of 9 breeds in domestic duck and two variation plumage color in Muscovy duck(146 individuals).Based on the detection of polymorphisms,the effect of different genotypes between breeds and plumage color traits were analyzed.We can draw some conclusion as follow:The length of the Chinese domestic duck and Muscovy duck partly coding sequence of MC1R gene were 817bp,the percent of A+T was 38.4%and G+C was 61.6%,respectively.The content of A+T was obviously lower than that of G+C.The sequences identities of MC 1R gene fragment between duck and other avian available from GenBank were compared.The percent of nucleotide homology was 93%-98.5%,we found the melanocortin-1-receptor(MC1R) is a G protein-coupled seven transmembrane helic receptor after we analyzed membrane spaning domain. The results suggested that MC1R gene is highly conserved during species evolution.Two mutations,Ala137Thr and Arg217Cys,were found in partly coding sequence of MCIR gene in domestic duck of this study.Hardy-Weinberg test found that heterozygous A/a(68.310%) was far higher than homozygous A/A or A/a in 137 position,on the other hand,the homozygous b/b(68.310%) is higher than homozygous B/B or heterozygous B/b in 217 position.In population genetics analysis,the results showed that there were significant association(P＜0.05) between the Arg217Cys,Ala137Thr mutations and domestic duck plumage color.In A locus,the black plumage Putian duck(100%) individuals belong to bb homozygous genotype,whereas the Bb heterozygous genotype presented in the remaining plumage color morph.While in B locus,In black plumage color morph (Putian duck),15 homozygotes(78.9%,15/19) were observed,whereas we found 23 heterozygotes(69.6%,23/33) in white morph(Beijing duck and Cherry valley duck),and this difference is statistically significant.The results indicated that MC1R gene is the candidate gene that regulates melanin traits in domestic duck or the domestic duck plumage color is linkage with candidate gene.Chi-Square test showed that the relationship between the single-nucleotides polymorphism locus of genotype distribution and breeds were significant correlation (P＜0.05) in domestic duck.The x~2-test was performed to examine the Hardy-Weinberg equilibrium.The 217R＞C significantly deviated from Hardy-Weinberg equilibrium,except for in population Ji-an,and 137A＞T in populations Xihu,Pekin,Cherry valley,Weishan and Guangdong-maya.The results indicated that high intensity in selective breeding,evolution process might actually be responsible for phenotypic diversity in domestic duck.The studies of the amino acid variation among the MC1R gene could reveal the Glu92Lys is correspondence with the black phenotype of Muscovy duck.it is likely that this is the causative mutation of melanic phenotype.