Mechanistic target of rapamycin in common carp: cDNA cloning, characterization, and tissue expression.

The mechanistic target of rapamycin (mTOR) plays a key role in growth and development. In the present study, a cDNA encoding mTOR protein was identified from common carp Cyprinus carpio muscle. The open reading frame of this cDNA encodes 2515 deduced amino acid residues that showed high sequence similarity with its zebrafish Danio rerio counterparts. Bioinformatic analysis showed that the protein belongs to the PI-3 kinase family. The putative protein has FAT, FRB, PI3Kc, and FATC domains, which are highly conserved among the vertebrate orthologs. Real-time quantitative PCR analysis revealed that the abundance of mTOR mRNA was the highest in the heart at 18-31 g and muscle at 31-75g of common carp. As the common carp grew (18-40 g), the mTOR expression gradually decreased in the hepatopancreas and heart, but increased in the muscle, hind kidney, spleen, gill, head kidney, foregut, midgut, and hindgut. Then the mTOR expression kept a constant in all examined tissues during the common carp grew (40-75g). The present study identified the mTOR gene and determined its gene expression profile in various tissues of the common carp with body weight increased. These findings will help better understand the biological role of mTOR in the juvenile fish.