Association of α-amylase gene with growth traits in the razor clam Sinonovacula constricta

The razor clam Sinonovacula constricta is a commercially and ecologically important benthic mollusk. In the present study, we investigated the full-length cDNA sequence of the S. constricta alpha-amylase gene (Scamy) using expressed sequence tags and rapid amplification of cDNA ends. The genomic DNA sequence of Scamy is 5086 bp, which contains 6 exons and 5 introns. The full-length Scamy cDNA was 2196 bp, with a 2085 bp open reading frame encoding 694 amino acids. Scamy expression was very low before the D-shaped larvae stage, with the highest expression levels in juvenile clams. Expression levels of Scamy were significantly higher in the digestive gland compared with other tissues in adults (p < 0.01). Analysis of the Scamy gene in the digestive gland in starved clams indicated that both gene expression and enzyme activity increased before decreasing, reaching its highest expression on the second day. Gene expression and amylase activity both increased gradually after refeeding. These results demonstrated that starvation and refeeding increased amylase activity in razor clams. Association analysis identified one shared single nucleotide polymorphism, C1503T, for which individuals with genotypes TT and CT had significantly higher growth traits than those with genotype CC (p < 0.05). This study suggests the potential value of amylase markers in selective breeding to improve clam growth.