Crossman Aleksandra H, Ignatz Eric H, Hall Jennifer R, Kumar Surendra, Fast Mark D, Eslamloo Khalil, Rise Matthew L
Memorial University, Department of Ocean Sciences, 0 Marine Lab Road, St. John's, NL, A1C 5S7, Canada.
Memorial University, Aquatic Research Cluster, CREAIT Network, Ocean Sciences Centre, 0 Marine Lab Road, St. John's, NL, A1C 5S7, Canada.
Dev Comp Immunol. 2023 Jun;143:104689. doi: 10.1016/j.dci.2023.104689. Epub 2023 Mar 18.
Atlantic salmon (Salmo salar) is one of the most economically important aquaculture species globally. However, disease has become a prevalent threat to this industry. A thorough understanding of the genes and molecular pathways involved in the immune responses of Atlantic salmon is imperative for selective breeding of disease-resistant broodstock, as well as developing new diets and vaccines to mitigate the impact of disease. Members of the interferon regulatory factor (IRF) family of transcription factors play roles in the induction of interferons and other cytokines involved in host immune responses to intracellular and parasitic pathogens. IRF family members also play diverse roles in other biological processes, such as stress response, reproduction and development. The current study focused on one member of the IRF family: interferon regulatory factor 2 (irf2). As previously shown, due to the genome duplication that occurred ∼80 million years ago in the salmonid lineage, there are two irf2 paralogues in the Atlantic salmon genome. In silico analyses at the cDNA and deduced amino acid levels were conducted followed by phylogenetic tree construction with IRF2 amino acid sequences from various ray-finned fishes, cartilaginous fish and tetrapods. qPCR was then used to analyze paralogue-specific irf2 constitutive expression across 17 adult tissues, as well as responses to the viral mimic pIC (i.e., synthetic double-stranded RNA analog) in cultured macrophage-like cells (in vitro) and to infection with the Gram-negative bacterium Moritella viscosa in skin samples (in vivo). The qPCR studies showed sex- and paralogue-specific differences in expression across tissues. For example, expression of both paralogues was higher in ovary than in testes; expression (considering both sexes together) was highest for irf2-1 in gonad and for irf2-2 in hindgut. Both irf2 paralogues were responsive to pIC stimulation, but varied in their induction level, with irf2-1 having an overall stronger response than irf2-2. Only one paralogue, irf2-2, was significantly responsive to M. viscosa infection. Differences in irf2-1 and irf2-2 transcript expression levels constitutively across tissues, and in response to pIC and M. viscosa, may suggest neo- or subfunctionalization of the duplicated genes. This novel information expands current knowledge and provides insight into how genome duplication events may impact host regulation of important immune markers.
大西洋鲑（Salmo salar）是全球经济上最重要的水产养殖物种之一。然而，疾病已成为该行业普遍存在的威胁。深入了解参与大西洋鲑免疫反应的基因和分子途径，对于抗病亲鱼的选择性育种以及开发新的饲料和疫苗以减轻疾病影响至关重要。干扰素调节因子（IRF）家族的转录因子成员在诱导干扰素和其他参与宿主对细胞内和寄生性病原体免疫反应的细胞因子中发挥作用。IRF家族成员在其他生物过程中也发挥着多种作用，如应激反应、繁殖和发育。当前的研究聚焦于IRF家族的一个成员：干扰素调节因子2（irf2）。如先前所示，由于约8000万年前鲑科谱系中发生的基因组复制，大西洋鲑基因组中有两个irf2旁系同源物。在cDNA和推导的氨基酸水平上进行了计算机分析，随后用各种硬骨鱼、软骨鱼和四足动物的IRF2氨基酸序列构建了系统发育树。然后使用qPCR分析17种成年组织中旁系同源物特异性的irf2组成型表达，以及在培养的巨噬细胞样细胞（体外）中对病毒模拟物pIC（即合成双链RNA类似物）的反应和在皮肤样本（体内）中对革兰氏阴性菌粘质莫拉菌感染的反应。qPCR研究显示，各组织中的表达存在性别和旁系同源物特异性差异。例如，两个旁系同源物在卵巢中的表达均高于睾丸；性腺中irf2 - 1的表达（综合考虑两性）最高，后肠中irf2 - 2的表达最高。两个irf2旁系同源物均对pIC刺激有反应，但诱导水平不同，irf2 - 1的总体反应比irf2 - 2更强。只有一个旁系同源物irf2 - 2对粘质莫拉菌感染有显著反应。irf2 - 1和irf2 - 2转录本表达水平在各组织中的组成型差异以及对pIC和粘质莫拉菌的反应差异，可能表明重复基因的新功能化或亚功能化。这些新信息扩展了当前的知识，并为基因组复制事件如何影响宿主对重要免疫标志物的调节提供了见解。
