Polymorphism in the Ras andβ-Glucosidase Genes and Their Association with Growth Traits in the Pacific Oyster Crassostrea gigas

The Ras gene,a conserved member of the insulin pathway,andβ-glucosidase gene,an important cellulase,are two important growth-related genes.However,there is no study on the association between mutations of these two genes and growth traits in bivalves.Here,the polymorphism of these two genes in Crassostrea gigas were revealed.Their association with growth traits was evaluated in 290 oysters from five families,and was further confirmed in another 186 oysters from three fast-growing strains.Seventeen and twelve SNPs were identified in the Ras gene andβ-glucosidase gene,respectively.Among these SNPs,four SNPs in each gene(Ras:C.86C>A,C.90T>C,C.112A>G and C.118G>A;β-glucosidase:C.247G>A,C.284C>T,C.1260C>T and C.1293T>C)were significantly(P<0.05)associated with the growth of these oysters.Furthermore,eight and nine haplotypes were constructed in the Ras gene andβ-glucosidase gene,respectively.Oysters with both haplotypes R-Hap5(CCAA)andβ-Hap7(ACCT),or with both R-Hap 6(ATGG)andβ-Hap 6(ACTC),or with both R-Hap 6 andβ-Hap 9(ACTT),or with both R-Hap 7(ATAA)andβ-Hap 7,showed the highest growth performances.These results provide candidate markers for selecting C.gigas with fast growth.