Submitted to: Journal of Antibiotics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/11/2005
Publication Date: 12/1/2005
Citation: Kinscherf, T.G., Willis, D.K. 2005. The biosynthetic gene cluster for the beta-lactam antibiotic tabtoxin in Pseudomonas syringae. Journal of Antibiotics. 58:817-821. Interpretive Summary: Tabtoxin in a potent toxin produced by some members of the bacterial species Pseudomonas syringae. When making tabtoxin, these bacteria can cause devastating losses to agricultural crops such as tobacco and succulent beans. Our paper describes the DNA sequencing of the genes responsible for tabtoxin production. This knowledge not only informs us of the mechanism by which bacteria make this potent toxin, but it provides us with markers that we can use to identify these plant pathogens using modern technology. We also identified genes that make the bacteria immune to the toxin, providing a potential novel source for toxin resistance.
Technical Abstract: DNA sequence analysis revealed that the tabtoxin biosynthetic genes of P. syringae BR2 reside at the att site adjacent to the lysC tRNA gene. Subcloning experiments indicated that tabtoxin production correlated to an 18kb section of the region. Gene expression appears to be bidirectional, and occurs from at least four transcriptional units. ORFs similar to two proteins associated with clavulanic acid synthesis were present. Tabtoxin resistance was associated with a fragment containing a major facilitator superfamily (MFS) exporter. Hypersensitivity to tabtoxin was exhibited by bacteria containing part of the biosynthetic region in the absence of the portion conferring resistance. The regions flanking the tabtoxin biosynthetic genes contained gene clusters associated with gene islands from a variety of plant and animal pathogens.