IcmF and DotU are required for the virulence of Acidovorax oryzae strain RS-1.

Acidovorax oryzae (Ao) cause bacterial brown stripe in rice that result in great economic loss. However, the pathogenic mechanism of this rice bacterial pathogen still remains unclear. Interestingly, transcriptomic and proteomic analysis of in vivo infection indicate that the pathogenicity of Ao strain RS-1 may be associated with the type six secretion system (T6SS), which was identified by in silico comparative genomic analysis in our previous studies. This makes it necessary to further examine the role of each core component of T6SS in the pathogenicity of Ao strain RS-1 to rice plants. Results from this study highlight the mutual interaction between IcmF and DotU, which was determined by bacterial two-hybrid and bimolecular fluorescence complementation assays. Furthermore, a difference was observed in bacterial pathogenicity, biofilm formation, secreted proteins identified by LC-MS/MS analysis and the expression of T6SS other genes examined by quantitative real-time PCR between the wild-type and both single-gene knockout mutants, which were respectively constructed based on the insertional mutagenesis of Ao strain RS-1 in this study. Overall, our results clearly revealed the importance of T6SS icmF and dotU in pathogenicity of Ao strain RS-1 to rice plants.