Sturm Armin, Carmona-Antoñanzas Greta, Humble Joseph L, Croton Claudia, Boyd Sally, Mphuti Rapule, Taggart John B, Bassett David I, Houston Ross D, Gharbi Karim, Bron James E, Bekaert Michaël
Institute of Aquaculture, University of Stirling, Stirling, Scotland, UK.
University of Glasgow, Glasgow, Scotland, UK.
BMC Genomics. 2024 Dec 18;25(1):1212. doi: 10.1186/s12864-024-11096-2.
The salmon louse (Lepeophtheirus salmonis) is a parasite of wild and farmed salmonid fish, causing huge economic damage to the commercial farming of Atlantic salmon (Salmo salar) in the northern hemisphere. The avermectin emamectin benzoate (EMB) is widely used for salmon delousing. While resistance to EMB is widespread in Atlantic populations of L. salmonis, the molecular mechanisms of resistance remain to be elucidated. The aim of the present work was to obtain insights into potential EMB resistance mechanisms by identifying genetic and transcriptomic markers associated with EMB resistance.
Crosses were performed between EMB-susceptible and -resistant L. salmonis, sourced from two parental strains isolated in Scotland, producing fully pedigreed families. The EMB susceptibility of individual parasites was characterised using time-to-response bioassays. Parasites of two families were subjected to double digest restriction site-associated DNA sequencing (ddRAD-seq) for simultaneous discovery of single nucleotide polymorphisms (SNPs) and genotyping. Data analysis revealed that EMB resistance is associated with one quantitative trait locus (QTL) region on L. salmonis chromosome 5. Marker-trait association was confirmed by genotyping assays for 7 SNPs in two additional families. Furthermore, the transcriptome of male parasites of the EMB-susceptible and -resistant L. salmonis parental strains was assessed. Among eighteen sequences showing higher transcript expression in EMB-resistant as compared to drug-susceptible lice, the most strongly up-regulated gene is located in the above QTL region and shows high homology to β spectrin, a cytoskeleton protein that has roles in neuron architecture and function. Further genes differentially regulated in EMB-resistant lice include a glutathione S-transferase (GST), and genes coding for proteins with predicted roles in mitochondrial function, intracellular signalling or transcription.
Major determinants of EMB resistance in L. salmonis are located on Chromosome 5. Resistance can be predicted using a limited number of genetic markers. Genes transcriptionally up-regulated in EMB resistant parasites include a β spectrin, a cytoskeletal protein with still incompletely understood roles in neuron structure and function, as well as glutathione S-transferase, an enzyme with potential roles in the biochemical defence against toxicants.
鲑虱（Lepeophtheirus salmonis）是野生和养殖鲑科鱼类的寄生虫，对北半球大西洋鲑（Salmo salar）的商业养殖造成巨大经济损失。阿维菌素类的苯甲酸盐伊维菌素（EMB）被广泛用于鲑鱼除虱。虽然在大西洋鲑虱种群中对EMB的抗性普遍存在，但其抗性的分子机制仍有待阐明。本研究的目的是通过鉴定与EMB抗性相关的遗传和转录组标记，深入了解潜在的EMB抗性机制。
从在苏格兰分离的两个亲本菌株中获取对EMB敏感和抗性的鲑虱进行杂交，产生了完全系谱的家族。使用反应时间生物测定法对单个寄生虫的EMB敏感性进行了表征。对两个家族的寄生虫进行了双酶切限制性位点相关DNA测序（ddRAD-seq），以同时发现单核苷酸多态性（SNP）并进行基因分型。数据分析表明，EMB抗性与鲑虱5号染色体上的一个数量性状位点（QTL）区域相关。通过对另外两个家族中的7个SNP进行基因分型分析，证实了标记-性状关联。此外，还评估了对EMB敏感和抗性的鲑虱亲本菌株雄性寄生虫的转录组。在18个与药物敏感虱子相比在EMB抗性中表现出更高转录表达的序列中，上调最强烈的基因位于上述QTL区域，并且与β血影蛋白具有高度同源性，β血影蛋白是一种细胞骨架蛋白，在神经元结构和功能中起作用。在EMB抗性虱子中差异调节的其他基因包括一种谷胱甘肽S-转移酶（GST），以及编码在预测的线粒体功能、细胞内信号传导或转录中起作用的蛋白质的基因。
鲑虱中EMB抗性的主要决定因素位于5号染色体上。可以使用有限数量的遗传标记预测抗性。在EMB抗性寄生虫中转录上调的基因包括β血影蛋白，一种在神经元结构和功能中作用仍未完全了解的细胞骨架蛋白，以及谷胱甘肽S-转移酶，一种在对毒物的生化防御中可能起作用的酶。
