Abstract Fish blood contains RBCs (Red blood cells) as the major cells. Unlike the absence of nucleus in mammalian RBC, fish RBC contains a nucleus. Previous researches have indicated that fish RBCs have a significant function in immune responses. However, the mechanism underlying the immune responses against bacterial infection of teleost RBCs remains enigmatic. To decipher the mechanisms, after the infection of Aeromonas hydrophila, transcriptomic profiling of grass carp RBCs was analyzed. Outcomes demonstrated that there were 2144 altogether DEGs (Differently Expressed Genes) between the A. hydrophila-infected and non-infected groups, which includes 817 up-regulated and 1327 down-regulated DEGs. Differently Expressed Genes were allocated to 45 GO terms, including 20 natural procedure terms, 14 cell related element, and 11 terms related to molecular functions. In addition, to validate our transcriptomic data, the expression levels of cytokines by Quantitative Reverse Transcription Polymerase Chain Reaction showed that they (e.g. CCL4, CCL11, CCL20, IL-4, IL-12, and IFNα) were significantly increased after A. hydrophila infection, which was identical to the expression patterns of transcriptomic data. The infection could cause the apoptosis of RBCs which was confirmed by annexin V/PI assay. To further elucidate the apoptosis pathway, the expression levels of genes by mRNA included in cellular apoptosis were monitored. The outcomes indicated that the expressions of mRNA of p53, Fas, Leucine-rich repeats, death domain-containing (LRDD) and caspase 8 were all significantly increased, respectively. Our results support the notion that A. hydrophila infection could activate Fas-related death receptor apoptosis pathway in grass carp RBCs, which will reveal another insight on the mechanisms underlying the antibacterial immunity of teleost fish RBCs.

中文翻译：

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嗜水气单胞菌感染激活草鱼红细胞死亡受体凋亡通路

摘要 鱼血以RBCs（红血细胞）为主要细胞。与哺乳动物红细胞中没有细胞核不同，鱼类红细胞含有细胞核。先前的研究表明，鱼类红细胞在免疫反应中具有重要作用。然而，针对硬骨红细胞细菌感染的免疫反应的机制仍然是个谜。为了破译其机制，在感染嗜水气单胞菌后，分析了草鱼红细胞的转录组学分析。结果表明，嗜水链球菌感染组和未感染组之间共有2144个DEG（不同表达基因），其中上调817个DEG和下调1327个。差异表达基因被分配到 45 个 GO 术语，包括 20 个自然过程术语，14 个细胞相关元素，和 11 个与分子功能相关的术语。此外，为了验证我们的转录组数据，定量逆转录聚合酶链式反应的细胞因子表达水平表明，它们（例如 CCL4、CCL11、CCL20、IL-4、IL-12 和 IFNα）在 A.hydrophila 后显着增加感染，这与转录组数据的表达模式相同。感染可引起红细胞凋亡，膜联蛋白V/PI试验证实了这一点。为了进一步阐明细胞凋亡途径，监测了细胞凋亡中包含的 mRNA 基因的表达水平。结果表明，p53、Fas、富含亮氨酸重复序列、死亡域（LRDD）和半胱天冬酶8的mRNA表达均显着增加。我们的结果支持 A.