Fish nocardiosis is a chronic systemic granulomatous disease, and Nocardia seriolae is the main pathogen. The pathogenesis and virulence factors of N. seriolae are not fully understood. Secreted superoxide dismutase (SOD) may be a virulence factor found by a comparative bioinformatics analysis of the whole genome sequence of N. seriolae and the virulence factor database (VFDB). In order to determine the subcellular localization and study the preliminary function of SOD from N. seriolae (NsSOD), gene cloning, secreted protein identification, subcellular localization in fish cells, and apoptosis detection of NsSOD were carried out in this study. Subcellular localization research revealed that NsSOD‐GFP fusion proteins were evenly distributed in the cytoplasm. Furthermore, apoptotic bodies were observed in the transfected FHM cells by the overexpression of protein NsSOD. Then, assays of mitochondrial membrane potential (ΔΨm) value, caspase‐3 activity and apoptosis‐related genes (Bax, Bid, Bad and Bcl‐2) mRNA expression were conducted. The results showed that ΔΨm was decreased, and caspase‐3 was significantly activated. The mRNA expression of the Bad gene showed significant up‐regulated expression at 24 h.p.t., while Bid and Bax genes showed significant up‐regulated expression at 72 and 96 h.p.t. and anti‐apoptotic gene (Bcl‐2) was down‐regulated in NsSOD overexpressed cells. Taken together, the results indicated that the protein NsSOD might be involved in apoptosis regulation. This study may lay the foundations for further studies on the function of NsSOD and promote the understanding of the virulence factors and the pathogenic mechanisms of N. seriolae.

中文翻译：

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从诺卡氏菌的分泌超氧化物歧化酶（SOD）的鉴定，该超氧化物歧化酶可诱导黑头now鱼（FHM）细胞凋亡。

鱼类诺卡氏病是一种慢性全身性肉芽肿性疾病，而诺卡氏丝虫是主要病原体。猪笼草的发病机理和毒力因子尚未完全了解。分泌的超氧化物歧化酶（SOD）可能是通过对猪笼草的全基因组序列进行比较的生物信息学分析和毒力因子数据库（VFDB）发现的毒力因子。为了确定亚细胞定位，并研究S. ola的SOD的初步功能本研究进行了NsSOD（NsSOD），基因克隆，分泌蛋白鉴定，亚细胞定位以及鱼细胞凋亡检测。亚细胞定位研究表明，NsSOD-GFP融合蛋白均匀分布在细胞质中。此外，通过蛋白NsSOD的过表达在转染的FHM细胞中观察到凋亡小体。然后进行线粒体膜电位（ΔΨm）值，caspase-3活性和凋亡相关基因（Bax，Bid，Bad和Bcl-2）mRNA表达的测定。结果表明，ΔΨm降低，而caspase-3明显活化。Bad基因的mRNA表达在24 hpt时表达显着上调，而Bid和BaxNsSOD过表达的细胞中，这些基因在72和96 hpt处表达显着上调，而抗凋亡基因（Bcl-2）则下调。两者合计，结果表明蛋白NsSOD可能参与细胞凋亡的调控。这项研究可能躺在NsSOD的功能进一步研究的基础，促进了毒力因子和致病机制的了解N.黄尾脾脏。