| Summary: | The environmental bacterium <i>Pseudomonas mosselii</i> produces antagonistic secondary metabolites with inhibitory effects on multiple plant pathogens, including <i>Ralstonia solanacearum,</i> the causal agent of bacterial wilt. In this study, an engineered <i>P. mosselii</i> strain was generated to express <i>R. solanacearum ripAA</i>, which determines the incompatible interactions with tobacco plants. The <i>ripAA</i> gene, together with its native promoter, was integrated into the <i>P. mosselii</i> chromosome. The resulting strain showed no difference in antimicrobial activity against <i>R. solanacearum</i>. Promoter-LacZ fusion and RT-PCR experiments demonstrated that the <i>ripAA</i> gene was transcribed in culture media. Compared with that of the wild type, the engineered strain reduced the disease index by 9.1% for bacterial wilt on tobacco plants. A transcriptome analysis was performed to identify differentially expressed genes in tobacco plants, and the results revealed that ethylene- and jasmonate-dependent defense signaling pathways were induced. These data demonstrates that the engineered <i>P. mosselii</i> expressing <i>ripAA</i> can improve biological control against tobacco bacterial wilt by the activation of host defense responses.
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