Polymorphisms Of Glycogen Metabolism Enzyme Gene And Their Association With Growth Performance And Glycogen Content In The Pacific Oyster Crassostrea Gigas

Glycogen is the prominent nutrient of oysters for growth and development, and ithas impact on texture and flavor of the flesh of the Pacific oyster (Crassostrea gigas).Glycogen synthase and glycogen phosphorylase are one pair of the key enzymesinvolved in glycogen metabolism. Short term regulation of glycogen metabolismrefers to the enzymatic regulation controls by feedback inhibition, while theexpression of genes encoding enzymes implicated in glycogen pathway is long termregulation. The expression levels of glycogen synthase gene and glycogenphosphorylase gene were found to be consistent with seasonal changes of glycogencontent in glycogen metabolism in C.gigas, corresponding to the need of glycogen forgametogenic development and germ cell maturation, which is natural physiologicalphenomenon of oysters.Numerous single nucleotide polymorphisms (SNPs) provide rich materials forassociation analysis between polymorphisms of candidate genes and economic traitsin C.gigas. Haplotype is a linear arrangement of nucleotide bases of the multipleSNPs on the same chromosome. Association analysis based on a haplotype as themolecular genetic markers is more efficient than one based on a single SNP marker.In the present study,322oysters were selected from five full-sib familiesrandomly. The glycogen synthase gene (Cg-GYS) and glycogen phosphorylase gene(Cg-GPH) of C.gigas were as candidate genes for association analysis of glycogenmetabolism. SNPs in coding regions of the gene and their association with growthperformance (shell height, shell length, shell depth, total weight and soft-tissue weight)and glycogen content (%dry weight) were investigated.1. Polymorphisms of the glycogen synthase gene (Cg-GYS) and their associationwith growth performance and glycogen content in C.gigasA total of41SNPs located in exon region were revealed in1420bp of theCg-GYS gene. The average density of SNPs reached one every35bp in coding region.Six SNPs found in coding regions were significantly associated with glycogen content(P <0.01), and from which we constructed four main haplotypes due to linkage disequilibrium. Haplotype-trait analysis based on the SNPs associated with growthperformance was not carried out due to the few numbers of the SNPs. Furthermore,individuals with H2possessed the extremely significant (P <0.0001) high glycogencontent compared with ones with H3. As a result, H2was likely to be the mosteffective haplotype associated with high glycogen content.2. Polymorphisms of the glycogen phosphorylase gene (Cg-GPH) and theirassociation with growth performance and glycogen content in C.gigasA total of82SNPs were revealed in1940bp of the Cg-GPH gene, including63SNPs in exon region,1SNP site located in5’-UTR and18SNPs in3’-UTR. Theaverage density of SNPs reached one every25bp in coding region. A total of fiveSNPs were found to be significantly associated with growth performance (P <0.05),whereas no association between SNPs and glycogen content was detected.Furthermore, among the six SNP haplotypes constructed by the five SNPs above, totalweight of the individuals with the haplotype H6(CTGAT) of Cg-GPH wassignificantly higher than those with the other five haplotypes (P <0.05), suggestingthe haplotype H6(CTGAT) may be the most advantageous haplotype of weight gainin C. gigas.