Study On The Polymorphisms Of Chicken IGFs/LYZ Gene, EAV-HP Sequence And Relationship With Economic Traits Of Jinghai Yellow Chicken

Use of three growth curve models and four egg production curve modles analysed Jinghai yellow chicken growth and laying traits laws. In the first part of the present study, we chose IGF1, IGF2, LYZ genes and EAV-HP DNA sequence as candidate genes for economic traits in Jinghai yellow chicken. To explore the relationship between these genes with economic traits in chicken, single strand conformation (SSCP) analysis and sequencing reactions were performed to screen single nucleotide polymorphisms (SNPs) in Jinghai yellow chicken. In the second part, we analyzed the effects of combined genotypes of different genes involved in IGF1*IGF2 and LYZ*gag-env interaction modes. The main results were as follows:⑴The cululative weight curve of Jinghai yellow chicken was like an"S"line. Logistic, Bertalanfy and Gompertz models well fitted the growth curve of Jinghai yellow chicken, and the Gompertz model fitted best. Yang Ning and McMillan models fitted well in Jinghai yellow chicken egg production curve, and Yang Ning model better.⑵No mutations were detected in exon 1, 2 and 4 of Chicken IGF1gene. Mutations were found in exon 3 and 5'non-coding regions. The mutation in exon 3 was silent mutation, didn't cause changes in amino aci sequence. Genotype ditributions of IGF1 gene were in Hardy-Weinberg equilibrium, indicating the genetic nature of Jinghai yellow chicken population was relatively stable. The species still had great patential for breeding.⑶The chicken IGF1 gene had a major impact on growth traits of Jinghai yellow chicken, which could be used as a genetic marker in molecular marker-assisted selection on ralated traits. IGF1 gene may be linked with reproductive QTL to a certain distance, thus the relationship with reproductive traits may change with different species, strains and families.⑷Mutations were detected in exon 1, 2 and 3 of chicken IGF2 gene. The mutations of exon 1 and 2 changed amino acid seqence, excluding exon 3 silent. Distribution of genotypes produced by two pairs of primers was in Hardy-Weinberg equilibrium, while by one pair of primers was extremely uneven. This indicated that the seletion process of certain traits affected random genetic of the gene in Jinghai yellow chiken.⑸The effect of IGF2 gene on growth traits differ at different growth stages in different strains of chicken. To be concluded that chicken IGF2 gene might not be the major gene controlling reproductive traits, but might be in a certain linkage with reproductive traits. The chicken IGF2 gene effected sexual maturity, egg producton and egg weight in Jinghai yellow chicken.⑹By SNPs scanning in exon region of chicken LYZ gene, synonymous mutations were detected in exon 1 and 2, excluding in exon 3 and 4. The distribution of genotypes in exon 1 changed from imbalance to balance might be related to artificial selection, which indicated that the chicken LYZ gene had great relevance to important economic traits. Five genotypes were found in exon 2, revealing the genetic diversity was very rich.⑺The chicken LYZ gene did not significantly associated with lysozyme content and enzyme activity in egg white, indicating that the gene had no significant effect on lysozyme expression in egg. The gene was found in significantly relationship with some economic traits of chicken for the first time by study on Jinghai yellow chicken J+ and J- lines. We initially infered that the LYZ gene might be a major gene or closely linked with major gene regulating chicken'growth and development.⑻To provide a feasible, easy, reliable and stable way, a standard method for determining poultry egg white lysozyme content and enzyme activity was established.⑼By scanning for the first time in part of the chicken EAV-HP DNA sequence, SNPs were found in more than seven polymorphic sites, of which two sites as silent mutations, five mutations caused changes in amino acid sequence. Amino acid changes might make protein be different in structure and biological function, and directly of indirectly affected the growth of animal body. The J+ and J- lines of Jinghai yellow chicken were bred by multiple artificial selection process. The location of the gene might be in the target QTL genetic region or adjacent area. Artificial selection pressure imposed on the two different strains inadvertently changed the random inheritance of the gene, so that the distribution of genotypes in the population was extremly uneven.⑽By correlation analysis of genotype&haplotype and growth traits of two strains of Jinghai yellow chicken, We concluded that the gag-env fusion gene of EAV-HP significantly related with chicken growth traits, and the direction of effects differred in J+ and J- strains.⑾Chicken IGF1 and IGF2 genes had interaction on 0-week, 12-week BW and age of first egg in Jinghai yellow chicken. The economic traits of chicken with different genotype combinations were significantly different. Chicken LYZ and gag-env genes had interaction on 8-week, 12-week and 16-week BW in Jinghai yellow chicken.⑿The analysis of single-gene genotype combiantion and two genes with growth traits were not exactly the same. Using SNPs of two genes or more genes for marker-assisted breeding had less risk than using SNPs of a single gene. On Jinghai yellow chicken breeding, selecting I3*IG1 AA/CC individuals could improve birth weight, choosing I6*IG1 CC/BB chicken could increase 12-week BW, excluding I6*IG1 DD/BB individuals could lead to early age of fist egg, saving L1*EA6 GA/AC and GA/CC chicken could increas 12-week and 16-week BW, reserving L2*EA3 TN/AC and L2*EA6 CC/AA, CC/BB, CC/CC, CT/AC individuals could increase 8-week BW.