Objective  The bacterial canker of Populus euramericana is caused by the Gram-negative bacterium Lonsdalea populi. The rapid spread of the disease has seriously threatened the growth and development of P. euramericana and has caused great economic losses to the plantation. Two-component system (TCS) is the important signal transduction mechanism of Lonsdalea populi. Now, how the two-component system of poplar bacterial canker regulates the pathogenic process is still lack of systematic research. Therefore, the large-scale deletion mutation and mutant phenotype analysis of TCS in this study will provide genetic materials for further study on the pathogenic mechanism of poplar bacterial canker.

  Method  In this study, 28 two-component gene deletion mutants of poplar canker pathogen strain L. populi N-5-1 were constructed by parental association, the differences in pathogenicity, growth, motility, biofilm formation and resistance of these mutants were analyzed by phenotypic analysis, and the regulation of two-component system coding genes on the pathogenicity of these mutants was studied.

  Result  In this study, 36 recombinant vectors of two-component coding genes were constructed and 28 deletion mutants were obtained. Phenotypic analysis showed that 18 genes encoding TCS were involved in virulence of L. populi N-5-1. Among them, the pathogenicity of 8 mutants had obviously disappeared. In addition, the deletion mutants regulating motility and biofilm-forming ability and those deficient in stress response (metal ions, salt ions, antibiotic stress, etc.) were also screened.

  Conclusion  In this study, five two-component genes significantly affecting the pathogenicity of L. populi were obtained, providing genetic material for future studies on the pathogenic mechanism of L. populi.