Molecular cloning of liver angiotensinogen gene in ayu (Plecoglossus altivelis) and mRNA expression changes upon Aeromonas hydrophila infection

Angiotensinogen (AGT) is thought to be an acute phase protein, because in mammals its plasma concentrations increase during inflammation induced by lipopolysaccharides (LPS). A full-length cDNA clone of the AGT gene, 1828 bp in size, was isolated from the fish ayu (Plecoglossus altivelis). Its deduced amino acid sequence of 462 residues had 57.7–68.6%, 30.2% and 23.3–27.4% identity to those sequenced from other fish, chicken and mammals, respectively. Ayu-AGT is most closely related to that of silver sea bream and the phylogenetic tree largely reflects the currently accepted animal relationships. In healthy control fish, AGT transcripts were found to be present in a number of tissues including brain, spleen, liver, kidney and intestine. The amplification was found to be the highest in the liver. In Aeromonas hydrophila-infected ayu, AGT transcripts significantly increased in various tissues, suggesting a possible relationship between AGT mRNA expression and the vascular inflammation caused by bacterial infection. AGT transcripts could be detected in the heart and gill of bacteria-infected ayu that were not detected in control fish, but still not in the muscle. This is the first report of changes in fish AGT transcripts upon bacterial infection.