Abstract: Nocardia seriolae,a facultative intracellular bacterium,is the main pathogen of fish nocardiosis. Bioinformatics analysis showed that the DmpA gene of N. seriolae encoded a secreted protein,and may be co-located with mitochondria of the host cell. In this study,the recombinant plasmids pEGFP-DmpA and pcDNA-DmpA were constructed,extracellular product of N. seriolae was identified,and the subcellular localization and over-expression of DmpA were carried out. The results showed that the protein DmpA was identified in the extracellular products of N. seriolae,and confirmed as a secreted protein. Subcellular localization of DmpA-GFP fusion proteins were evenly distributed in the whole cell of FHM cells,and were not coincided with the distribution of mitochondria,indicating that the protein DmpA was not co-localized with the mitochondria. The expression of DmpA changed the distribution of mitochondria into lumps in the FHM cell. The over-expression of DmpA in FHM cells had no significant effect on the nucleus,revealing that the gene had no function on inducing cell apoptosis. The cloning,subcellular localization and over-expression of DmpA from N. seriolae laid the foundation for further studying the function of the gene and promoting the understanding of the pathogenic mechanism of N. seriolae.

Key words: Nocardia seriolae, gene DmpA, secreted protein, subcellular localization