The Roslin Institute and Royal (Dick) School of Veterinary Sciences, The University of Edinburgh, Edinburgh, UK.
Faculty of Veterinary and Livestock Sciences, University of Chile, Santiago, Chile.
BMC Genomics. 2021 Mar 6;22(1):156. doi: 10.1186/s12864-021-07443-2.
Salmon Rickettsial Syndrome (SRS), caused by Piscirickettsia salmonis, is one of the primary causes of morbidity and mortality in Atlantic salmon aquaculture, particularly in Chile. Host resistance is a heritable trait, and functional genomic studies have highlighted genes and pathways important in the response of salmon to the bacteria. However, the functional mechanisms underpinning genetic resistance are not yet well understood. In the current study, a large population of salmon pre-smolts were challenged with P. salmonis, with mortality levels recorded and samples taken for genotyping. In parallel, head kidney and liver samples were taken from animals of the same population with high and low genomic breeding values for resistance, and used for RNA-Sequencing to compare their transcriptome profile both pre and post infection.
A significant and moderate heritability (h = 0.43) was shown for the trait of binary survival. Genome-wide association analyses using 38 K imputed SNP genotypes across 2265 animals highlighted that resistance is a polygenic trait. Several thousand genes were identified as differentially expressed between controls and infected samples, and enriched pathways related to the host immune response were highlighted. In addition, several networks with significant correlation with SRS resistance breeding values were identified, suggesting their involvement in mediating genetic resistance. These included apoptosis, cytoskeletal organisation, and the inflammasome.
While resistance to SRS is a polygenic trait, this study has highlighted several relevant networks and genes that are likely to play a role in mediating genetic resistance. These genes may be future targets for functional studies, including genome editing, to further elucidate their role underpinning genetic variation in host resistance.
鲑鱼立克次氏体病（SRS）由鲑鱼鱼立克次氏体引起，是大西洋鲑鱼养殖业，尤其是智利主要发病率和死亡率的原因之一。宿主抗性是一种可遗传的特征，功能基因组研究突出了在鲑鱼对细菌的反应中重要的基因和途径。然而，遗传抗性的功能机制尚未得到很好的理解。在本研究中，大量鲑鱼幼鱼前体受到鲑鱼鱼立克次氏体的挑战，记录死亡率并取样进行基因分型。同时，从具有高和低抗性基因组育种值的同一群体的动物中取出头肾和肝脏样本，并用于 RNA-Seq 测序，以比较其感染前后的转录组谱。
二元存活性状表现出显著的中等遗传力（h=0.43）。使用 2265 只动物中的 38K 个已导入 SNP 基因型进行全基因组关联分析，突出表明抗性是一种多基因性状。在对照和感染样本之间鉴定出数千个差异表达的基因，并强调了与宿主免疫反应相关的富集途径。此外，还鉴定出与 SRS 抗性育种值具有显著相关性的几个网络，表明它们参与了介导遗传抗性。其中包括细胞凋亡、细胞骨架组织和炎症小体。
尽管对 SRS 的抗性是一种多基因性状，但本研究突出了几个可能在介导遗传抗性中起作用的相关网络和基因。这些基因可能是未来功能研究的目标，包括基因组编辑，以进一步阐明它们在宿主抗性遗传变异中的作用。
