Caligus rogercresseyi serine proteases: Transcriptomic analysis in response to delousing drugs treatments

Trypsin and chymotrypsin are the most abundant serine proteases in crustaceans, and these typically fulfill roles in dietary protein digestion and the immune response. However, recent evidence has demonstrated that serine proteases are also capable of catalyzing the degradation of non-protein molecules, such as pyrethroid insecticides. The present study identified trypsin and chymotrypsin in the salmon louse Caligus rogercresseyi and evaluated the transcriptional modulation of these after exposure to the delousing compounds deltamethrin and azamethiphos. High-throughput transcriptome sequencing identified 44 putative trypsin-like and 7 putative chymotrypsin-like transcripts in C. rogercresseyi that showed differentiated transcriptional modulation after drug exposure. Overall, deltamethrin exposure modulated the transcriptional response greater than azamethiphos. A sex-biased transcriptional response was evidenced for Cr-Tryp1-6-10-36 and 41 under exposure to either antiparasitic agent, with upregulation 100-fold greater than the control group. Together, these results suggest that trypsin-like transcripts in C. rogercresseyi might play a role in metabolizing delousing drugs. The identification of trypsin-like transcripts, together with functional validations, is a valuable strategy for pinpointing target molecules that could be used in developing new management strategies for C. rogercresseyi. Statement of relevance: The current manuscript describes the variety of trypsin and chemotrypsins in the sea lice Caligus rogercresseyi. Our findings suggest that trypsin-like transcripts in C. rogercresseyi might play a role in metabolizing delousing drugs. The identification of trypsin-like transcripts, is a valuable strategy for developing new management strategies against C. rogercresseyi. (C) 2016 Elsevier B.V. All rights reserved.