The versatile fish pathogen Edwardsiella tarda is an intracellular pathogen with the ability to invade and replicate in host phagocytes. However, the mechanism mediating the uptake of E. tarda in fish monocytes/macrophages (MO/MΦ) is not yet understood. Generating mudskipper kidney-derived MO/MФ transcriptomic resources from mudskipper challenged by E. tarda is crucial for understanding the molecular mechanisms underlying the mudskipper invasion process. In the present study, a total of 1185 up-regulated and 885 down-regulated differentially expressed genes (DEGs) were identified using RNA-seq. Enrichment and pathway analysis of DEGs revealed the centrality of the phagosome and regulation of actin cytoskeleton pathways in pathogen entry. The progress of phagosome formation was observed by transmission electron microscopy. Eight conserved integrin (ITG) subunit genes, belonging to the phagocytic receptors, were found in the transcriptomic sequence data. Additionally, quantitative real-time PCR showed that the mRNA expressions of most ITG subunit genes were related to the different infection times of E. tarda and the different bacterial pathogens. Further assays demonstrated that phagocytosis of FITC-labeled E. tarda by mudskipper MO/MФ was significantly reduced by the tetrapeptide Asp-Gly-Arg-Ser (RGDS). In summary, phagocytosis is one of the entry pathways into mudskipper MO/MΦ, and RGD-binding ITGs are involved in the phagosome formation process.

多用途鱼类病原体Edwardsiella tarda是一种细胞内病原体，具有侵入宿主吞噬细胞并在其中复制的能力。然而，目前尚不清楚在鱼单核细胞/巨噬细胞 (MO/MΦ)中介导E. tarda摄取的机制。从受到E. tarda挑战的弹涂鱼中生成弹涂鱼肾脏衍生的 MO/MФ 转录组资源对于理解弹涂鱼入侵过程的分子机制至关重要。在本研究中，使用 RNA-seq 共鉴定了 1185 个上调和 885 个下调的差异表达基因 (DEG)。DEGs 的富集和通路分析揭示了吞噬体在病原体进入中的中心地位和肌动蛋白细胞骨架通路的调节。通过透射电子显微镜观察吞噬体形成的进程。在转录组序列数据中发现了八个属于吞噬受体的保守整合素 (ITG) 亚基基因。此外，实时定量 PCR 显示，大多数 ITG 亚基基因的 mRNA 表达与迟发性大肠杆菌的不同感染时间有关。以及不同的细菌病原体。进一步的测定表明，四肽 Asp-Gly-Arg-Ser (RGDS) 显着降低了弹涂鱼 MO/MФ对 FITC 标记的迟缓大肠杆菌的吞噬作用。综上所述，吞噬作用是弹涂鱼 MO/MΦ 的进入途径之一，结合 RGD 的 ITG 参与了吞噬体的形成过程。