Association Of Five Genes Including MITF And FOXP1 With Colors Of Beak,Foot-web And Plumage In Ducks

The color traits of poultry refer to the various colors of its skin and derivatives,including feather color,skin color,beak color and shank color etc..They are important phenotypic markers of different breeds,and can also be used in breeding and product marketing as important appearances of products.The study of genes controlling color traits in poultry is not only helpful to understand the mechanism of color formation on skin and its derivatives,but can improve breeding efficiency through marker-assisted selection in breeding.There are some studies on the inheritance and controlling genes of plumage color in duck,but few study on beak color and webbed color have been done.The purpose of this study was to search genes controlling the beak and web colors in ducks.For this purpose,the F2 population(Population A)previously constructed by our group was used as the research material,the relationship between five genes including MITF,FOXP1 and beak and web color in ducks was studied by SNP screening and association analysis,and the results were validated by another populations(population B).The main results were as follows:The HE staining sections of different color feather quills showed that there were indeed different distributions of melanin in black feathers,hemp feathers and white feathers.Family information record in Population A showed that separation of beak color was consistent with that of feather color.Correlation analysis showed that there was a strong correlation between feather color and beak color,the correlation coefficient was0.902,beak color and foot-web color,the correlation coefficient was 0.803,and feather color and foot-web color,the correlation coefficient was 0.779.In Population A,the correlation between four SNPs(g.808002C>T,g.808890C>T,g.820188C>T and g.8479G>A)on MITF and duck beak color,foot-web color and feather color was analyzed and validated by PCR-RFLP and chi-square contingency table test.The results showed that when beak color and foot-web color were divided into non-yellow and yellow phenotypes,the genotypes of all mutations were significantly associated with phenotypes(P < 0.001),and feather color was also significantly correlated with the four loci(P < 0.001).In Population B,the genotyping and chi-square results of these four loci also showed significant correlation with beak color(P < 0.001),web color(P < 0.001)and feather color(P < 0.001)of ducks.The expression of MITF gene in different feather bulbs showed that the expression level in black feather bulb wassignificantly higher than that in white,but the expression level in Ma duck was not significantly different from that in other two kinds duck.In addition,recent studies have shown that an 6.6KB insertion in intron of MITF gene causes the whitening of Peking duck feathers.However,in our Population A,some individuals with white feathers could not detect the insertion fragment,which indicates that there may be mutations in other loci besides the insertion sequence that cause duck white feather in Population A.Our study also showed that this fragment was associated with the beak color phenotype(yellow and non-yellow)and foot-web color phenotype(yellow and non-yellow).There are several single nucleotide polymorphisms(SNPs)associated with melanin deposition in FOXP1 gene.We validated 12 SNPs on FOXP1 gene in Population A,six of them were highly associated not only with the beak color(P < 0.001)and foot-web color(P < 0.001)of ducks,but also with the feather color of ducks(P < 0.001)(g.350510T>C,g.350550A>G,g.350677A>G,g.351116A>G,g.351629C>T and g.351769C>T).Preliminary test results of g.350209T>C locus also showed that it was associated not only with beak color(P < 0.05)and foot-web color(P < 0.05),but also with feather color(P <0.05).Although RT-PCR results showed no significant difference in FOXP1 expression between white and black feather bulbs,SNPs correlation results showed that FOXP1 gene was a marker gene of duck beak,webbed and feather color.Three SNPs related to pigmentation were found in FMNL2 gene.Among them,g.771957G>A was only associated to feather color(P < 0.05)in ducks,g.767494G>A was only associated to foot-web color(P < 0.05)in ducks,but g.764720A>T was not significantly related to duck feather color(P > 0.05),beak color(P > 0.05)and foot-web color(P > 0.05).These indicated that FMNL2 may be associated with melanin deposition in domestic ducks.Preliminary confirmation of g.506985T>C locus on the candidate gene Nocth2 showed no significant correlation with beak color(P > 0.05)and foot-web color(P > 0.05)of ducks,nor with the feather color(P > 0.05).SNPs were found in AARS genes associated with foot-web pigmentation.Preliminary test results showed these sites were not associated with pigmentation.In addition,only g.755429C>G(KB742527.1)was found to be highly associated with beak color(P < 0.001),(P < 0.001)and feather color(P < 0.001).