Polymorphism,Genetic Effect And Breeding Application Of -868 Locus Of FSHR Gene In Langya Chicken

As a local breed,Langya chicken has been severely impacted by foreign chicken breeds and is decreasing day by day.It is very important to improve the egg-laying performance of Langya chicken to protect the resources of this local breed.As the main hormone to promote follicle development,FSH needs to be realized through the FSHR-mediated c AMP pathway,and in the process of follicle selection,the small yellow follicles in the pre-hierarchal follicles will be selected to enter the hierarchal follicles when the FSHR expression level is higher than that of other small yellow follicles.Therefore,FSHR is very important for follicle selection and poultry egg laying process.At the same time,there are multiple SNPs in FSHR,and exploring the relationship between them and laying traits is also a method to improve the laying performance of local poultry breeds.In this study,the polymorphism characteristics of the-868locus in the 5′regulatory region of Langya chicken FSHR were analyzed,and then the association analysis of the polymorphism of this locus and egg-laying traits was carried out,and the relative expression levels of FSHR m RNA and FSHR protein in pre-hierarchal follicles,hierarchal follicles and ovaries of different genotypes at this locus were further compared,so as to provide a theoretical basis for the application of Langya chicken breeding.The results are as follows:（1）Polymorphism analysis of-868 locus in the 5′regulatory region of FSHR in Langya chickens.For the FSHR 5′regulatory region-868 locus polymorphism,G^-is the dominant allele in this Langya chicken flock,and its allele frequency is 0.7002.Among the three gene frequencies,G^-G^-is the most（0.5131）,and the population deviates from the Hardy-Weinberg equilibrium（P<0.05）.The-868 locus polymorphism has no significant effect on AFE,E32and ACL,but the AFE of G^-G^-has a tendency to be earlier than G⁺G⁺;it has a significant effect on E47（P<0.05）,and G^-G^-is significantly lower than G⁺G^-;The effect on LCS is extremely significant（P<0.01）and G^-G^-is significantly lower than G⁺G^-and G⁺G⁺.（2）Expression analysis of different genotypes at the-868 locus in the 5′regulatory region of FSHR in Langya chickens.By q RT-PCR method,the m RNA expression of FSHR was compared between genotypes at the FSHR 5′regulatory region-868 locus polymorphism.The relative expression of FSHR m RNA in G⁺G⁺was the highest in pre-hierarchal follicles,and G^-G^-was significantly lower than G⁺G⁺（P<0.05）.A significant effect was not reached in hierarchal follicles and ovaries but G^-G^-was the lowest in comparison;By Western blotting method,the protein expression of FSHR was compared between genotypes at the FSHR 5′regulatory region-868 locus polymorphism.The relative expression level of FSHR protein did not reach a significant effect in pre-hierarchal follicles and hierarchal follicles;Individuals of G^-G^-genotype was significantly lower in ovaries than that of G⁺G^-（P<0.05）.（3）Breeding application analysis of-868 locus in the 5′regulatory region of FSHR in Langya chickens.The-868 locus polymorphism in the 5′regulatory region of FSHR had a significant effect on the egg production of the original Langya chickens at 134 days after moulting（P<0.05）,and G^-G^-was significantly lower than G⁺G^-,which was consistent with the results of E47,further indicating G^-G^-of deficiencies in egg production.In terms of hybridization and utilization of Langya chickens,combined with the production performance measurement,G^-G^-is suggested to be gradually eliminated in the chicken flock to increase the frequency of the G⁺gene,which can improve the overall egg-laying performance of Langya chickens,so as to breed a new line of Langya chicken with good egg-laying performance;in terms of the demand for species conservation of Langya chickens,in order to protect the genetic diversity,G^-G^-will not be eliminated,the G⁺G⁺of high egg-laying traits and the G^-G^-of early-laying traits are mated to obtain G⁺G^-individuals that own their respective advantages.To sum up,the polymorphism of the-868 locus in the 5′regulatory region of FSHR in Langya chickens affects egg laying traits:The age of the first egg of G^-G^-is earlier than G⁺G⁺,but in general,G⁺G⁺is better than G^-G^-,While G⁺G^-combines the respective advantages of the two genotypes;in terms of the relative expression of FSHR m RNA and FSHR protein:G^-G^-was at the lowest level.The above research shows that the three genotypes at-868 locus in the5′regulatory region of the FSHR gene are associated with the egg-laying traits of Langya chickens,which provides a theoretical basis for the conservation and breeding application of Langya chickens.