Liver transcriptome analysis and identification of differentially expressed immune gene response to Aeromonas veronii infection in Channa argus

The Channa argus ( C. argus ), an important cultured freshwater species, is widely distributed in China, which possesses the characteristic of high disease resistance. However, the information on genomic and transcriptomic studies on disease resistance of this species is not available at present. To address the shortfall and to better understand snakehead immune response to pathogen infection at molecular level, the C. argus were challenged with potent Aeromonas veronii ( A. veronii ) for 24 h and the high-throughput RNA sequencing (RNA-seq) technology was employed to produce transcriptomes from the liver. Firstly, the serum parameters were significantly changed after Aeromonas veronii infection for 24 h compared with the control group. Thus, an average of 326,557,262 clean reads obtained were de novo assembled into 157,766 unigenes with most of the unigenes between 201 and 500 bp. All of unigenes were annotated to six public databases (Nr, Swiss-Prot, COG, GO, KEGG, and Pfam). A total of 21,217 differentially expressed unigenes (DEGs) were identified. The 21,217 DEGs were significantly enriched in 16 pathways related to the immune or disease. Finally, the expression levels of six selected immune-related DEGs were scrutinized. Three genes encoding TNF-α, IL-1β, and Bcl2 were significantly upregulated, whereas the gene encoding MyD88, NOD-1, and NOD-2 was significantly downregulated. In summary, this study provides valuable transcriptome resource for understanding the defense mechanisms of C. argus in resistance to pathogens from the gene expression viewpoint, which also open up the possibility to study the immune complexity and to better comprehend the interrelationships between some immune pathways in C. argus .