Transposon mutagenesis reveals pv. optimizes its virulence factors for pathogenicity on different hosts.

pv. (), which causes bacterial blight disease of Brassicaceae, is an economically important pathogen worldwide. To identify genes involved in pathogenesis, we conducted a screen for 1,040 individual KB211 Tn mutants with reduced virulence on cabbage plants using a dip-inoculation method. We isolated 53 reduced virulence mutants and identified several potential virulence factors involved in virulence mechanisms such as the type III secretion system, membrane transporters, transcription factors, and amino acid metabolism. Importantly, is pathogenic on a range of monocotyledonous and dicotyledonous plants. Therefore, we also carried out the inoculation test on oat plants, which are cultivated after cabbage cultivation as green manure crops. Interestingly among the 53 mutants, 31 mutants also exhibited reduced virulence on oat seedlings, indicating that optimizes its virulence factors for pathogenicity on different host plants. Our results highlight the importance of revealing the virulence factors for each plant host-bacterial interaction, and will provide new insights into virulence mechanisms.