Transcriptome Analysis Reveals the Mechanism Of Teleost Macrophages Respond to Bacterial Infection in Vivo

Abstract

Sebastes schlegelii is an economically significant marine fish that faces serious threats from various pathogens. Edwardsiella piscicida is a pathogenic bacterium that primarily affects fish, including S. schlegelii, leading to severe disease. Although numerous reports have documented the transcriptome sequencing of various fish tissues in response to E. piscicida infection, studies focusing on specific cells remain scarce. In this study, S. schlegelii were infected by intraperitoneal injection of E. piscicida. The external clinical signs observed in E. piscicida-infected S. schlegelii included hemorrhagic superficial ulcers on the skin and visceral congestion. Histopathological examination of the head kidney in E. piscicida-infected S. schlegelii revealed a loose tissue structure, renal tubular epithelial cell edema, and cell necrosis. Furthermore, macrophages were isolated from the head kidneys of both the control and E. piscicida-infected groups for RNA sequencing (RNA-seq). A total of 1,151 differentially expressed genes (DEGs) were identified, with 853 up-regulated and 298 down-regulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the DEGs were closely associated with immune response and oxidative stress. Additionally, Weighted Gene Co-expression Network Analysis (WGCNA) was performed based on the data from this study and RNA-seq files of macrophages infected with E. piscicida in vitro, revealing that immune responses, oxidative stress, and mitochondrial damage were involved in the macrophage response to E. piscicida infection both in vivo and in vitro. This study provides a reference for understanding the mechanisms by which teleost immune cells respond to pathogen invasion and enhances our comprehension of teleost innate immunity.

Keywords: Edwardsiella piscicida, macrophage, immune response, RNA-seq