Time-resolved and multi-tissue RNAseq provides new insights on the immune responses of European eels following infection with Aeromonas hydrophila

No studies have systematically compared time-resolved and multi-tissue innate immune responses for European eels(Anguilla anguilla)with Aeromonas hydrophila infection by a high throughput method.Here,we challenged European eels with A.hydrophila(infected)or PBS(control).A low fatality rate(16.1%)was observed for the infected group at 2 d post-infection(dpi).Then we examined transcriptional profiles of intestines,livers and spleens from 12 European eels with/without infection by A.hydrophila at 6,18 and 36 h post-infection(hpi).The results showed that the most differentially expressed genes(DEGs)were found in the spleen at 6 hpi(7569 DEGs),followed by the intestine at 6 hpi(3129 DEGs)and the liver at 18 hpi(2722 DEGs).Only 540,41 and 130 DEGs were found in the spleen,liver,and intestine at 36 hpi,respectively.The comparison of DEG numbers and enriched KEGG pathways suggested a consistent time-course immune response in these tissues.A similar enrichment of pattern recognition receptors-related pathways including Toll-like receptors,NOD-like receptors and RIG-I-like receptors was found in the liver and spleen,but not in the intestine.Among immune-related DEGs,62 paralogue pairs were found,and the expression trends of most paralogues were consistent.Some paralogues of immune-related DEGs had unique domains.Furthermore,large clusters representing similar tissue were shown for the intestine and spleen.A different co-expression network involved in cytokine signal transduction and interaction existed between the liver and spleen.This study has provided time-resolved and multi-tissue transcriptome characteristics of A.anguilla in response to A.hydrophila infection.