Investigation of the Role of a Zinc Uptake Regulator (Zur) in the Virulence of .

spp. infect many horticultural crops worldwide and lead to serious crop losses. Zinc-uptake-regulator (Zur) proteins are present widely in prokaryotes and play an important role in pathogenicity. To uncover the role of Zur in . , we constructed mutant () and overexpression [Po ()] strains of a , and a virulence assay showed that the Po () was of significantly lower virulence, while the displayed significantly increased virulence on Chinese cabbage compared to their respective control strains, wild-type . (Po WT) and . harboring an empty vector (Po (EV)) ( < 0.05). The growth curves of the and Po () showed no obvious differences from those of the control strains. Comparative transcriptome analysis showed that overexpression in . induced differentially expressed genes (DEGs) related to flagellum and cell motility, while mutating resulted in DEGs mainly corresponding to divalent-metal-ion transport and membrane transport. Phenotypic experiments on the Po () showed that flagellum numbers and cell motility were reduced in comparison with the control, while those of the did not change. Collectively, these results show that the Zur negatively regulates the virulence of . and might function via a dual mechanism dependent on dose.