Polymorphisms in the FOXO gene are associated with growth traits in the Sanmen breeding population of the razor clam Sinonovacula constricta

We identified the FOXO gene and five single-nucleotide polymorphisms(SNPs)in its coding region in the Sanmen breeding population of the razor clam Sinonovacula constricta.The ScFOXO gene encodes a protein of 625 amino acids in length that contains a conserved DNA-binding domain.Real-time polymerase chain reaction analysis showed that ScFOXO mRNA is widely expressed in adult tissues,with higher expression in the siphons and gills.Of the SNPs,c.879G>C(Val293Val)and c.1725A>G(Ser575Ser)are synonymous mutations,and c.543C>T(Phe181Leu),c.848A>G(Tyr283Cys),and c.1625G>C(Gly542Phe)are non-synonymous mutations.The SNPs all show significant associations with total body weight,shell length,shell width,and shell height(SH)in this population.Polymorphic parameter analysis showed that all SNPs except c.848A>G(Tyr283Cys)exhibit complete linkage.The SNP c.1625G>C(Gly542Phe)was used for genetic linkage mapping and demonstrates the strongest linkage(logarithm of the odds[LOD]value:41.46)with the marker 96616(37.02 cM)in the linkage group 9.The LOD value of this marker in relation to growth traits ranges from 1.04 to 1.53;only markers with a LOD value
3 were considered to be linked with growth traits in the razor clam linkage map.In summary,ScFOXO may be a growth trait-related gene and may represent a marker for Sanmen breeding group selection.