Molecular cloning and expression analysis of peptidase genes in the fish-pathogenic scuticociliate Miamiensis avidus

The 17 genes encoding peptidases, including seven cathepsin-like cysteine peptidases, four serine carboxypeptidases, a eukaryotic aspartyl protease family protein, an ATP-dependent metalloprotease FtsH family protein, three leishmanolysin family proteins and a peptidase family M49 protein were identified from a Miamiensis avidus cDNA library by BLAST X search. Expression of genes encoding two cysteine peptidases, three leishmanolysin-like peptidases and a peptidase family M49 protein was up-regulated in the cell-fed ciliates compared to the starved ciliates. Especially, one cysteine peptidase (MaPro 4) and one leishmanolysin-like peptidase (MaPro 14) were transcribed more than 100-folds in the cell-fed ciliates.The genetic information and transcriptional characteristics of the peptidases in the present results would be helpful to elucidate the role of peptidases in the invasion of scuticociliates into their hosts.