Salmon lice (Lepeophtheirus salmonis) showing varying emamectin benzoate susceptibilities differ in neuronal acetylcholine receptor and GABA-gated chloride channel mRNA expression

BMC Genomics

Research Article

Jacqueline H Ireland¹  Stephen N Carmichael¹  John B Taggart¹  James E Bron¹  Michaël Bekaert¹  Armin Sturm¹  Philip J Skuce²  Stewart TG Burgess²  Alasdair J Nisbet²  Karim Gharbi³ 

[1] Institute of Aquaculture, School of Natural Sciences, University of Stirling, FK9 4LA, Stirling, UK;Moredun Research Institute, Pentlands Science Park, Bush Loan, EH26 0PZ, Penicuik, Midlothian, UK;The GenePool, School of Biological Sciences, The University of Edinburgh, EH9 3JT, Edinburgh, UK;

关键词: Drug resistance;    Sea lice;    Avermectin;    Ligand-gated chloride channel;    Cys-loop receptor;   

DOI  :  10.1186/1471-2164-14-408

 received in 2013-03-12, accepted in 2013-06-13,  发布年份 2013

来源: Springer

【 摘 要 】

BackgroundCaligid copepods, also called sea lice, are fish ectoparasites, some species of which cause significant problems in the mariculture of salmon, where the annual cost of infection is in excess of €300 million globally. At present, caligid control on farms is mainly achieved using medicinal treatments. However, the continued use of a restricted number of medicine actives potentially favours the development of drug resistance. Here, we report transcriptional changes in a laboratory strain of the caligid Lepeophtheirus salmonis (Krøyer, 1837) that is moderately (~7-fold) resistant to the avermectin compound emamectin benzoate (EMB), a component of the anti-salmon louse agent SLICE® (Merck Animal Health).ResultsSuppression subtractive hybridisation (SSH) was used to enrich transcripts differentially expressed between EMB-resistant (PT) and drug-susceptible (S) laboratory strains of L. salmonis. SSH libraries were subjected to 454 sequencing. Further L. salmonis transcript sequences were available as expressed sequence tags (EST) from GenBank. Contiguous sequences were generated from both SSH and EST sequences and annotated. Transcriptional responses in PT and S salmon lice were investigated using custom 15 K oligonucleotide microarrays designed using the above sequence resources. In the absence of EMB exposure, 359 targets differed in transcript abundance between the two strains, these genes being enriched for functions such as calcium ion binding, chitin metabolism and muscle structure. γ-aminobutyric acid (GABA)-gated chloride channel (GABA-Cl) and neuronal acetylcholine receptor (nAChR) subunits showed significantly lower transcript levels in PT lice compared to S lice. Using RT-qPCR, the decrease in mRNA levels was estimated at ~1.4-fold for GABA-Cl and ~2.8-fold for nAChR. Salmon lice from the PT strain showed few transcriptional responses following acute exposure (1 or 3 h) to 200 μg L-1 of EMB, a drug concentration tolerated by PT lice, but toxic for S lice.ConclusionsAvermectins are believed to exert their toxicity to invertebrates through interaction with glutamate-gated and GABA-gated chloride channels. Further potential drug targets include other Cys-loop ion channels such as nAChR. The present study demonstrates decreased transcript abundances of GABA-Cl and nAChR subunits in EMB-resistant salmon lice, suggesting their involvement in avermectin toxicity in caligids.

【 授权许可】

CC BY   
© Carmichael et al.; licensee BioMed Central Ltd. 2013