Molecular cloning of trypsin cDNAs and trypsin gene expression in the salmon louse Lepeophtheirus salmonis (Copepoda: Caligidae)

Abstract

The salmon louse, Lepeophtheirus salmonis, is a marine ectoparasitic copepod that infects salmonid fishes. We are studying the interactions between this parasite and its salmonid hosts, as it is a common cause of disease in both wild and farmed stocks of salmon. In this paper, we report on the cloning and sequencing of seven trypsin-like enzymes from a cDNA library prepared from whole body preadult female and male L. salmonis. The predicted trypsin activation peptides are 23 or 24 residues in length, considerably longer than previously reported activation peptides of other animals. Differences in the putative signal and activation peptide sequences of the trypsin isoforms suggest that these forms differ in their regulation and function. The calculated molecular weights of the trypsins range from 23.6 to 23.7 kDa. There are eight cysteine residues, which suggest the presence of four disulfide bridges. These trypsins are very similar (>or=46% aa identity) to other crustacean trypsins and insect hypodermins. Using in situ hybridization techniques trypsinogen expression could be identified in all three cell types of the midgut.

Salmon immunological defence and interplay with the modulatory capabilities of its ectoparasite Lepeophtheirus salmonis

“…The chalimus can attach to scales feeding on host mucus and epithelium (inset left) and commonly fins (micrograph) where erosion of epidermis can extend to the basal membrane but with no / limited inflammatory responses occurring around the periphery of the feeding site (micrograph -H&E) (C-D); Secreted proteins can inhibit coagulation, prevent wound healing, facilitate digestion and immune evasion/suppression, and may be anti-microbial. For example trypsins are highly expressed in the larger more aggressive feeding adult stages(159,160). (Fluorescent micrographs of in situ hybridisation (ISH)-labelled L sal trypsin.…”