Abstract：Myocyte enhancer factor 2D (MEF2D) is a member of the myocyte enhancer factor 2 (MEF2), a supergene family, and thought to be related to skeletal muscle growth and development. To investigate the effects of polymorphism of MEF2D gene on slaughter traits of Xingyi ducks (Anas platyrhynchos domestica), this study used PCR and DNA sequencing methods to find SNP loci and analyzed their correlation with slaughter traits. Meanwhile, the expression profile of MEF2D gene was investigated by qRT-PCR of different stages Xingyi ducks. Finally, the results showed 6 SNPs in exons, respectively, C3894T, G3957A, T16236C, A16305C, G16359C and A21071G. All of the six sites were synonymous mutation, and those did not cause a change of amino acid encoding. By population genetics analysis, the results showed that 6 loci were at moderately polymorphic status (0.25＜PIC＜0.5). The χ2 tests showed that the loci were all in Hardy-Weinberg equilibrium status (P＞0.05). Analysis of matching chain disequilibrium and haplotype analysis show that there was a strong chain of balance between the six loci. Analysis of association of polymorphism with slaughter traits at all mutation loci showed that T16236C locus and A16305C locus were significant effects on live weight, carcass weight, semi-eviscerated weight, eviscerated weight, and breast muscle weight (P＜0.05 or P＜0.01); G16359C locus was significant effects on semi-eviscerated weight and eviscerated weight (P＜0.05); A21071G locus was significant effects on carcass weight, eviscerated weight, leg muscle weight, dressing percentage and eviscerated weight rate (P＜0.05 or P＜0.01). Seven haplotype combinations were found in 52 Xingyi ducks, the CGCCCG haplotype have significant effects on semi-eviscerated weight and semi-eviscerated weight rate (P＜0.05 or P＜0.01); TACCCA (TATAGA) haplotype have significant effects on leg muscle weight (eviscerated weight rate) (P ＜ 0.05). The results of qRT-PCR showed that MEF2D was expressed in all 10 involved tissues, which illustrated that the expression of this gene was of broad spectrum, and exists significant difference between ducks and drakes. In all of the duck tissues, the highest expression of leg muscle was the highest, the expression level of heart, liver, lung, kidney, brain, muscle duodenum and glandular stomach were relatively higher. And in all of the drake issues, the expression level of cardiac muscle and liver were the highest, duodenum, brain, muscle, leg muscle and glands in the stomach were relatively high. The results suggested that the variation trend of mRNA expression level of MEF2D in most issues of ducks at different age stages was first increased and then decreased and then increased; drakes showed the trend of decrease- increase- decrease. The results suggested that four SNPs and three haplotype combinations might have potential effects on slaughter traits in the above mentioned duck populations and could be used for marker-assisted selection. This study could provide a theoretical basis for the follow-up analysis of structure and function of MEF2D gene in ducks, further enrich the research results of MEF2D.
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