Abstract: [Objective] To clone and express the DnaJ gene in Mycoplasma ovipneumoniae, and to assess the immunogenicity of its expression product. [Method] Using genomic DNA extracted from Mycoplasma ovipneumoniae NM03-MO strain isolated from Inner Mongolia as template, DnaJ gene was cloned. The DnaJ protein sequence was analyzed and its three-dimensional structure was predicted. A pColdⅠ-DnaJ prokaryotic expression vector was constructed with the cloned DnaJ gene fragment being connected to pColdⅠ vector to express the recombinant DnaJ protein. The obtained DnaJ protein was purified, and its binding activity to Mycoplasma antibody positive serum was evaluated by Western blot. [Result] The NM03-MO strain′s DnaJ protein had the highest homology to Mycoplasma ovipneumoniae, while there were minor differences in the three-dimensional structure. The recombinant DnaJ protein displayed high binding activity to Mycoplasma ovipneumoniae positive serum, indicating that it was a immunogenic protein. [Conclusion] For the first time, the DnaJ protein of Mycoplasma ovipneumoniae was successfully cloned and expressed and had good immunogenicity. This research lays the groundwork for the further molecular pathogenesis research and the development of novel vaccines.

Key words: Mycoplasma ovipneumoniae, DnaJ protein, sequence analysis, molecular cloning, immunogenicity