Characterization Of Chicken Skin Yellowness And Identification Of Related Molecular Markers

Poultry skin has the ability to deposit pigments,which affects skin color.Broiler skin color is one of the main reasons affecting consumer selection.Due to the complexity of the factors that affect the skin color,the color of the carcass of broilers varies greatly,and some individuals may have white or pale-yellow skin.The dark and light skin color affects the uniformity of the flock and is not good for the sale of chilled meat.In this study,Ma-Huang chickens were used as experimental objects.Our purpose in this study was to analyzed the measuring method of skin yellowness in broilers under intensive culture condition,and study the genetic characteristic of skin yellowness of broilers.Breeding methods related to skin yellowness of broilers would also be explored.The main results are as follows:1.Measuring method,genetic characteristic,and selection methods of skin yellowness in chickenIn order to analyze the variation of the skin yellowness value in broiler chicken more accurately,we conducted a correlation analysis between the yellowness values from different skin position obtained by colorimeter and the overall skin yellowness value obtained by MATLAB.Results showed that before and after slaughter,the yellowness value from different skin position was significantly correlated with overall skin color value.Analysis of single trait animal model of DMU showed that heritability of skin yellowness value was low,and skin yellowness value was positively correlated with meat quality traits.Correlation analysis between serum carotenoid concentration,which was obtained by HPLC,and yellowness value showed that carotenoid concentration was closely related to skin yellowness.These results are beneficial for evaluation and breeding of broiler skin color without fuzzing and slaughtering.2.The yellow skin gene BCO2 does not affect the yellowness value of Ma-Huang chickenBCO2 is an important gene affecting chicken yellow skin traits.300 Ma-Huang chickens were selected to carry out association analysis between 3 classic SNPs(chr24: 6264085,chr24: 6273428,chr24: 6287900)of BCO2 and skin yellowness.The genotypes of the three classic SNPs of BCO2 in Ma-Huang chicken were showed as followed: Genotypes of A site chr24: 6264085 were all AA,genotypes of C site chr24: 6287900 were all GG,and there were three genotypes at B site chr24: 6273428,GG,GA,and AA.In addition,we found two novel SNPs located near B site.Correlation analysis of genotype and skin color data showed that these three SNPs were not related to skin yellowness of Ma-Huang chicken(P > 0.05).The haplotype GGTTAA has significantly higher chest yellowness values ??than the haplotypes GACTGG,AATTGG,and GACTGA(P <0.05).3.Screening of genes related to skin yellowness deposition in Ma-Huang chickenBy analyzing RNA sequencing data of two-tail skin and fat samples from high yellowness skin and low yellowness skin chickens,we found some candidate genes and regulatory networks involved in the yellow pigment deposition in chicken.Analysis of protein interaction networks showed that the interaction among carotenoids,melanin,and immune processes affect skin pigmentation in chicken.4.Four SNPs in ALDH1A3 were significantly associated with the skin color of Ma-Huang chickenBoth RNA-seq and q RT-PCR results showed that the ALDH1A3 gene was highly differentially expressed between skin tissues.ALDH1A3 is one of the carotenoid metabolite retinoic acid synthase,which is involved in the carotenoid metabolism in cells.In this experiment,the 3 ’non-coding region sequence of ALDH1A3 was amplified to find SNP,and the association analysis of skin color was used to detect the effect of ALDH1A3 SNP on the skin color of Ma-Huang chicken.The results showed that there were 4 SNPs in the sequence of the 3 ’non-coding region of ALDH1A3 gene:g.117 T> C,g.170 A>,g.196 A> T,g.703 T> C.These four SNPs are significantly associated with the skin color of Ma-Huang chickens,as well as body traits and carcass traits.These SNPs can be used as new molecular markers.By determining the genotype of these SNP sites in chickens,early selection of chicken skin color,body size traits,and carcass traits can save production costs and accelerate genetic progress.In breeding,it has great economic application value and scientific research value.In summary,by establishing a new skin yellowness measuring method for Ma-Huang chicken,this study found that the skin color of cloaca before slaughter was significantly related to the color after slaughter.Chicken skin yellowness has low heritability,and there was genetic positive correlation between the skin yellowness and meat quality traits.Serum carotenoid concentrations were related to skin yellowness.The three classic SNPs of BCO2 did not affect the skin yellowness of Ma-Huang chickens.Through RNA-seq analysis,we found that some genes may be involved in the formation of skin color in Ma-Huang chickens.Four SNPs were found in the 3’non-coding sequence of the ALDH1A3 gene.These four SNPs were related to the skin color traits of chickens and have potential for breeding applications.The above results not only beneficial for improvement of measuring method and selection of skin yellowness in chickens,but also provided important reference data to improve the skin color consistency during broiler breeding.