Research On Fitting The Growth Curve And Correlations Between Accumulation Of Intramuscular Fat With MC4R And PPARγ Gene In Duck

Melanocortin receptor-4(MC4R) and peroxisome proliferator activated receptor y (PPARy) are two important genes which regulate fat metabolism, so the mRNA expression level and gene polymorphism of them may be closely related to the intramuscular fat content. Jinling White Duck, Liancheng white duck, Cherry Valley duck and Putian black duck were used as test materials, combined intramuscular fat phenotypic and molecular information for associated analysis by using the number of molecular genetics candidate gene approach.Determinated the intramuscular fat content in breast muscle and leg muscle at the age of4th,6th,8th,10th week by improved Soxhlet extraction method. MC4R and PPARy affect duck intramuscular fat content are treated as candidate genes. By determining MC4R and PPARy expression level in duck breast muscle and leg muscle, the correlation between mRNA expression level and intramuscular fat content are analyzed. By determination of the PCR-PFLP to some parts of sequences of MC4R and PPARy, it aims to explore gene polymorphism of MC4R and PPARy, to build correlation among these polymorphic loci and intramuscular fat and to make sure the theoretical basis of detected polymorphic loci as molecular-assisted selection marker.The main results showed that:1) Weight growth curve of Jinling White Duck, Liancheng white duck, Cherry Valley duck, Putian black duck from0to10weeks age were fitted according to three nonlinear mathematical models:Gompertz, Logistic, and von Bertalanffy. It showed that, all of the three curves can fit the four ducks weight growth process well, fitting degrees (R2) were above0.98. Then I picked out the best curve from different flock ducks and established reasonable weight-gain fitting equation, which provide people with theoretical basis of improving breeding and conservation quality.2) The intramuscular fat content in breast muscle and leg muscle of the4kinds of duck were determined by improved Soxhlet method. Comparing the intramuscular fat content of the four kinds of duck at different growing point, it indicated that there was significant difference of the intramuscular fat level in the four species on the basis of the same dietary levels. It mainly showed that, the intramuscular fat in local species was much higher than that in hybrid species, and the instramuschlar in the hybrid was higher than exotic species. In addition, the intramuscular fat in the leg muscle was significantly higher than the pectoral muscle (P<0.05).3) By determination of relative expression of MC4R and PPAR genes in breast muscle and leg muscle that was found at the same stage of growth, the expression level of the same gene had significant difference (P<0.05) among different species. The MC4R expression level in breast muscle of four duck species was significantly higher than in leg muscle at the latter three growth stages (P<0.05), but the difference was not significant in the fourth week(P>0.05). The PPARy expression level was significantly higher in pectoral muscle than the leg muscle at two observation points of beginning (P<0.05), and PPARy expression level was significantly higher in leg muscles than the pectoral muscles at the points of ending (P<0.05). By comparative analysis intramuscular fat content with relative tissue, I found that relative expression level of MC4R and PPARy negatively correlated with the intramuscular fat content, which could provide marker-assisted selection reference for future poultry breeding.4) Genomic DNA was extracted from muscle tissue of the four duck species.7pairs of primers to colony the CDS region of MC4R and PPARy were designed and amplified. It showed that, there was one polymorphic loci in the fragment that amplified with MC4R-S1primers:there was T-A single point mutation at the197th of MC4R CDS region, led to the66th amino acid valine into glutamic, which was missense mutation.3genotypes:TT, TA, AA were detected, S1amplified segment was analyzed by PCR-RFLP. The polymorphic information content (PIC) in the polymorphic loci ranged from0.25to0.5, which belonged to moderate polymorphism with high genetic development potential. By comparative analysis of intramuscular fat content in three genotype groups, I found that intramuscular fat content of AA genotype was slightly higher than that of TT and TA genotype, and in the breast muscle of4-week-old Jinling White Duck had significant difference (P<0.05), as well as in the leg muscle of10-week-old of it.