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Poster

Session: Session 1 Presenting Authors at Posters (Odds)

P-207 - PtaGI-1, identified in Pseudomonas syringae pv. tabaci 6605, is a genomic island containing some virulence genes and is necessary for virulence to tobacco.

Monday, July 14, 2025
13:30 - 15:15  
Location: Confex Hall 3
Microbial infection strategies (pathogens & non-pathogens)

Genomic islands (GIs) are 20–500 kb DNA regions that are thought to be acquired by horizontal gene transfer (HGT) on chromosome. Integrative and conjugative element (ICE), a category of GIs, are known to be transferred by conjugation. We identified two GIs, PtaGI-1 and PtaGI-2, in Pseudomonas syringae pv. tabaci 6605 (Pta6605) that causes wildfire disease in tobacco. PtaGI-1 and PtaGI-2 are approximately 110 kb and 103 kb, respectively, and homologous to ICEs in Pseudomonas species. Both GIs have intact and truncated tRNALys on each border. PCR analysis showed PtaGI-1 and -2 are excised from chromosome and circularized in the subpopulation of the colony of wild type strain. PtaGI-1 has tabtoxin biosynthetic gene cluster, and 3 type III effector genes. On the other hand, PtaGI-2 has homologous genes to hsvABC, virulence genes in Erwinia amylovola. To assess the function of two PtaGIs, we constructed the deletion mutants of each PtaGI and analyzed their phenotypes. The ∆PtaGI-1 mutant lost the ability to biosynthesize tabtoxin and to cause disease but not ∆PtaGI-2. These results indicate that PtaGI-1 is pathogenicity island involved in virulence. Some strains of P. syringae other than Pta6605 had the tabtoxin biosynthetic genes in the PtaGI-1-like sequence. The analysis of genome information has suggested tabtoxin biosynthetic genes are acquired by HGT.