A Survey of the ATP-Binding Cassette (ABC) Gene Superfamily in the Salmon Louse (Lepeophtheirus salmonis)

Abstract

Salmon lice, Lepeophtheirus salmonis (Krøyer, 1837), are fish ectoparasites causing significant economic damage in the mariculture of Atlantic salmon, Salmo salar Linnaeus, 1758. The control of L. salmonis at fish farms relies to a large extent on treatment with anti-parasitic drugs. A problem related to chemical control is the potential for development of resistance, which in L. salmonis is documented for a number of drug classes including organophosphates, pyrethroids and avermectins. The ATP-binding cassette (ABC) gene superfamily is found in all biota and includes a range of drug efflux transporters that can confer drug resistance to cancers and pathogens. Furthermore, some ABC transporters are recognised to be involved in conferral of insecticide resistance. While a number of studies have investigated ABC transporters in L. salmonis, no systematic analysis of the ABC gene family exists for this species. This study presents a genome-wide survey of ABC genes in L. salmonis for which, ABC superfamily members were identified through homology searching of the L. salmonis genome. In addition, ABC proteins were identified in a reference transcriptome of the parasite generated by high-throughput RNA sequencing (RNA-seq) of a multi-stage RNA library. Searches of both genome and transcriptome allowed the identification of a total of 33 genes / transcripts coding for ABC proteins, of which 3 were represented only in the genome and 4 only in the transcriptome. Eighteen sequences were assigned to ABC subfamilies known to contain drug transporters, i.e. subfamilies B (4 sequences), C (11) and G (2). The results suggest that the ABC gene family of L. salmonis possesses fewer members than recorded for other arthropods. The present survey of the L. salmonis ABC gene superfamily will provide the basis for further research into potential roles of ABC transporters in the toxicity of salmon delousing agents and as potential mechanisms of drug resistance.

Mutations in voltage‐gated sodium channels from pyrethroid resistant salmon lice (Lepeophtheirus salmonis)

“…Genomic screening of voltage‐gated sodium channels identified three L. salmonis Na v 1 homologues (Supporting information, Table S1), referred to in this study as LsNa v 1.1 , LsNa v 1.2 and LsNa v 1.3 , following to the accepted nomenclature for Na v channels . Transcript sequences of the three channels identified in a multi‐stage transcriptome of L. salmonis yielded cDNA sequences covering the whole open reading frame (ORF) for LsNa v 1.1 and LsNa v 1.3 and a partial sequence for LsNa v 1.2 (Supporting information, Table S1). The deduced amino acid sequences of the identified channels contain typical features present in all Na v 1, such as four homologous domains (I‐IV), the sodium sensing amino acids ‘DEKA’, and the inactivation gate motif (‘IFM’ in rat Na v 1.2; ‘MFM’ or ‘AFM’ in L. salmonis Na v 1 homologues) (Supporting information, Fig.…”

Deltamethrin resistance in the salmon louse, Lepeophtheirus salmonis (Krøyer): Maternal inheritance and reduced apoptosis

“…Carmona-Antoñanzas et al . found 33 genes/transcripts for ATP-binding cassette (ABC) genes 30 , from which 18 could be assigned to ABC subfamilies known to contain drug transporters, in L . salmonis .…”

High level efficacy of lufenuron against sea lice (Lepeophtheirus salmonis) linked to rapid impact on moulting processes

“…Benzoylurea binding to the sulfonylurea transporter ( SUR ) was suggested as the mechanism causing vesicle inhibition ( Abo-Elghar et al, 2004 ), although this remains ambiguous ( Meyer and Moussian, 2013 ). Probes corresponding to the L. salmonis SUR (described by Carmona-Antoñanzas et al, 2015 ) were not differentially expressed by lufenuron despite passing QC filters for all groups ( Additional File 1 ). Therefore, translocation of chitin from epithelia might be disrupted by lufenuron and other BPUs, however, the mechanism controlling this inhibition remains unresolved.…”