PtaGI-1, identified in Pseudomonas syringae pv. tabaci 6605, is a genomic island containing some virulence genes and is necessary for virulence to tobacco.

Pseudomonas syringae pv.tabaci (Pta) 6605, a causal agent of wildfire disease, has 2 genomic islands (GI) as mobile genetic region.Two GIs of Pta6605, named as PtaGI-1 and PtaGI-2, are over 100 kb and have intact and truncated tRNA Lys on each border.PCR analysis showed PtaGI-1 and -2 are excised from chromosome and circularized in the wild type strain.PtaGI-1 has tabtoxin biosynthetic gene cluster, and 3 type III effector genes.The PtaGI-1 mutant has lost the ability to cause disease and to biosynthesize tabtoxin but not PtaGI-2.These results indicate that PtaGI-1 is pathogenicity island involved in virulence.Tabtoxin-producing P. syringae other than Pta6605 had the tabtoxin biosynthetic genes in the GI-1-like sequence.The analysis of genome information has suggested tabtoxin biosynthetic ability is acquired by horizontal gene transfer. Pta6605 have partially identical 2GIs (PtaGI-1, PtaGI-2) on the chromosome. Two GIs are ICE that excised and circularized in subpopulation. PtaGI-1 that contains 3 type III effectors and tabtoxin biosynthetic gene cluster contribute their virulence. It is suggested tabtoxin are transfer horizontally because some strain have tabtoxin gene cluster with GI like region. SummaryPtaGI-1 and PtaGI-2 are homologous to known Pseudomonas 4 ICEs Two PtaGI are excised from chromosome and circularized PtaGI-2 WT PtaGI-1 Tabtoxin bioassay used E. coli as indicator Black arrow show that inhibition zone of E. coli exist around the filter paper with Pta6605 strain