Characteristics of α-Amylase gene and its association with growth traits in Meretrix meretrix

α-Amylase is a major digestive enzyme in phytophagous animals that catalyzes the hydrolysis of starch into sugars so that it affects the carbohydrate metabolism and growth of many species. In the present study, the full-length cDNA and intron sequences of α-amylase (MmAmy) were investigated by rapid amplification of cDNA ends (RACE) method. The genomic DNA sequence of MmAmy is 6689 bp, which contains 7 exons and 6 introns. The cDNA of MmAmy is 1783 bp, with a 1569 bp of open reading frame (ORF) encoding 522 amino acids. No expression was detected in the early stages of unfertilized mature eggs, fertilized eggs, 4-cell embryo, blastula, gastrulae, trochophore, whereas it was detected after D-shaped larva showing the highest expression in umbo larvae. The quantitative expression of six different tissues in adults showed that expression of MmAmy was enriched in visceral mass, while no expression was detected in other tissues. Furthermore, gene expression and enzyme activity of MmAmy in visceral mass were highly correlated with the growth rates of four shell color strains. The positive correlation between MmAmy and growth traits suggested that α-amylase gene could be used as a candidate gene in the molecular breeding programs to improve clam growth.