Transcriptome analysis of the spleen provides insight into the immunoregulation of Cyprinus carpio koi under Aeromonas veronii infection

Koi carp (Cyprinus carpio koi) is an important cultured freshwater ornamental fish. It has a rich color and high economic value. However, owing to epidemic infectious diseases in recent years, its cultivation has been restricted. Information about the interaction between koi carp and Aeromonas veronii is limited. To better understand the immune response of koi carp to A. veronii infection, we performed transcriptome sequencing of the spleen of koi carp after artificial A. veronii infection. Consequently, a total of 72,694 unigenes with a N50 length of 2011 bp were obtained. Differential expression analysis showed that there were 373 significantly differentially expressed genes (DEGs) 24 h after infection, of which 240 genes were upregulated and 133 genes were downregulated. The expression levels of NLRP3, CD11b, CD11c, ASC, and IL-1β, which are closely related to inflammasomes, were significantly upregulated. Further annotation and enrichment analysis indicated that DEGs were principally enriched in the phagosome, cell adhesion molecules, IL-17 signaling pathway, and antigen processing and presentation. The above mentioned molecules and signaling pathways may play an important role in the elimination of foreign, invading pathogens. To verify the accuracy of RNA-seq data, 10 genes related to immune function were selected for RT-qPCR experiments, and the results showed that their expression is highly consistent with the RNA-seq data. Additionally, the expression patterns of five differentially expressed inflammasome-related genes were also verified by RT-qPCR. A splenic transcriptome of koi carp between the control group and the A. veronii-immunized group was obtained, which provided new clues to the molecular mechanism of host–A. veronii interactions and provided a basis for further study on the gene expression and functional genomics of koi carp. •The first transcriptome analysis of koi carp's response to A.veronii.•72,694 high-quality unigenes and 373 differentially expressed genes were identified.•DEGs were enriched in phagosome, cell adhesion molecules, and IL-17 signaling.