An Integrated Gene Mapping Database “HyperGenome System”

Tn5 was inserted into the genome of Pseudomonas glumae, the plant pathogenic bacterium causing grain rot and seedling rot of rice, by conjugation with an Escherichia coli strain carrying pJB4J1, the plasmid vector for Tn5. Kanamycin resistant transconjugants appeared at the frequency of 2.73 X 10⁻⁵ per recipient. Of 250 Tn5 mutant strains obtained, 3 strains completely lost their pathogenicity to rice seedlings and 28 strains were attenuated in virulence. The inserted Tn5 element was detected in the chromosome of the avirulent transconjugants by Southern blot analysis. Avirulent transconjugants multiplied similarly to the virulent original strain in media, while the virulent strain multiplied to reach about 10 times higher level as compared to the avirulent transconjugants on/in the grains of the inoculated seedlings. The original strain could decompose all kinds of the four substrates, pectin, pectic acid, carboxymethylcellulose (CMC) and casein, while most of the avirulent and attenuated strains could not decompose some of them. These results suggests that the degrading enzymes are playing some important roles in the expression of pathogenicity.