| Leptin gene is a peptide hormone which is secreted by the hypothalamus, and effecting the receptors on the target cell membrane by regulating the hypothalamus; at the same time, convey a obesity and other signals to the brain by negative feedback methods, in this way, it plays a physiological role in the process of endocrine, angiogenesis, immune function, reproduction, bone formation, aspects of feed conversion and growth, etc. This study selected 42 healthy adult Xinjiang Brown Cattle on the basis of previous studies, and PCR-SSCP and PCR-RFLP methods were adopted to analyze the polymorphisms of Leptin gene Ⅱ E2JW and E2FB exons of longissimus dorsi muscle in Xinjiang Brown cattle. Analyzed the association of different genotypes of II E2JW and E2FB locus with body size traits (Body weight, Withers height Hip height, body steep length. Chest circumference. Hind legs around.Hip angle, Ischium Width, Hip width), carcass traits (eye muscle area. Back fat thickness. Eye height,12-13QIB, BPI), slaughter traits (carcass weight, dressing percentage, carcass length. Carcass depth, Carcass chest depth, Waist flesh. The rib thickness. Meat quality level) and meet quality traits (pH, Water holding capacity, protein, fat, moisture, color of rawMeatL, a, b, Cooking loss) of differnt Beef cuts (Blade Oyster, Chuck Tender, Cube Roll, Tenderlion, Striploin, Knuckle, Inside) by using ANOVA procedure of SPSS software to screening important candidate genes for the carcass and meat quality traits of Xinjiang Brown cattle, and also laid the foundation for the guidance of new type of selection of Xinjiang Brown beef and the molecular marker-assisted breeding work.The results are as follows:1. Ⅱ E2JW and E2FB exons of Leptin gene showed polymorphism in Xinjiang Brown cattle population. Three unique SSCP genotypes were observed (named as AA, BB and AB, respectively), the frequencies of genotypes AA, BB and AB were 0.1908,0.2857 and 0.5238, respectively. Correspondingly, frequencies of allele A and B were 0.4782 and 0.5217, respectively, and B is the dominant allele. Sequencing results showed that T103C, C113T, C126G and T252A in this site happened mutation. Groups polymorphism information content (PIC) was 0.3456, analyzed population possessed moderate genetic diversity, genetic heterozygosity was 0.4444. 2. The polymorphism of exon Ⅱ E2JW and E2FB locus of Leptin gene have significantly affect on body size traits in Xinjiang Brown cattle. The individuals with AA genotype of E2JW locus showed significantly (P<0.05) higher body size and Hip height than those with genotypes BB; the individuals with BB genotype showed significantly (P<0.05) higher Hind legs around than those with genotypes AB. There was a significant difference (P<0.05) between CC, CT and TT genotypes of E2FB in Withers height, Hip width, Ischium Width, Hip width; the individuals with CC genotype showed significantly (P<0.05) higher Withers height, Hip height than those with genotypes TT; the individuals with TT genotype showed significantly (P<0.05) higher Ischium Width, Hip angle than those with genotypes CC.3. The individuals with BB genotype of II E2JW locus in Leptin gene showed significantly (P<0.05) lower Inside Cooking loss than those with genotypes AA and AB. The individuals with CC genotype of E2FB locus showed significantly (P<0.05) lower eye muscle area than those with genotypes CT and TT; but there was no significant difference (P>0.05) between different genotypes of E2JW of the carcass traits, slaughter traits. The results of this study showed that the polymorphism of Leptin gene (IIE2JW and E2FB exons) significantly affect the body size traits and carcass traits of Xinjiang Brown cattle, and the correlation of Beef cuts still needs a further validation studies on the basis of large sample. |
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