Studies On Genetic Variation And Correlation Analysis Of PRL Gene Coding Region In Xupu White Geese

This study took PRL gene as a candidate which strongly relates to the broodiness, through designing seven pairs of primers to clone and sequence the PRL coding regions of Xupu white goose and Zi goose. PCR-SSCP technique was used to check the polymorphism in the amplification fragments by the primers to find out the correlation between the PRL coding region and laying performance, and finally some SNPs were detected.The analysis of PCR-SSCP showed that there were no SNPs in Exonl, 2, 3, and 5 of PRL gene, the alleles tested were fixed in the population. There was one SNP in Exon4 (G/A), but the amino acid was not changed as an silent mutation. The frequency of alleles of wild type (A) was 0.8837 and that of the mutant type (B) was 0.1163. There were two genotypes detected in the population, the frequency of AA is 0.7647, BB is 0, and AB is 0.2326. There. was also one SNP in Exon2 (T/C), and two genotypes were detected. The frequency of genotype C was 0.907, D was 0.093, CC was 0.814, CD was 0.186, and DD was 0.χ2 test showed that there was no significant difference (P>0.05) between distributions of genotypes and theoretical proportion in the test population, occupying Hardy-Weinberg equilibrium. SPSS was used to analyse the correlation between the SNPs and laying performance, the results showed that different genotypes had no significant influence to the laying performance (P＜0.05).Compared the PRL coding region sequence of Xupu white goose with other birds, the homology between Xupu white goose and Wanxi White goose, Zi goose, Rhin goose, and Magang goose was 99.7%, 99.7%, 99.6%,98.8%, and with Beijing duck was 98.4%, with chicken was 92.0%.Compared with Wanxi White goose, the analysis of amino acid sequences showed that there was a mutation (69Leu to Phe), and with Rhin goose, there was also a mutation (56His to Arg), but the hydrophilicity, polarity and the charge did not change, only small changes happened in molecular weight which located in the first a-helix. Compared with Magang goose, there were three mutations (6Ala to Asp, 105Asp to His, 205Arg to His), and the first mutation happened on the signal peptide sequence and the characteristic of amino acid changed, the second mutation located in the fourth a-helix, but the hydrophilicity, polarity and the charge did not change, only small changes happened in molecular weight. These mutations may be important to the secretion and transportation of PRL gene, but whether they influence the function ofPRL gene is still to be investigated.Through the results analyzed by bioinformatics, it was showed that T/C transversion in Intron 2 of PRL gene may lead the appearance of SRY factor, and the change of Tst-1 factor into Nkx-2 factor. Using codon usage frequency to analyze the G/A mutation in Exon 4 of PRL gene, there was a change of CUG into CUA, and they both coded leucine, but the usage frequency of the former was 6 times more than the latter, so the mutation in Exon 4 may influence the synthesis efficiency of protein, so as to cause the difference in PRL expression quantity.