title: A mutation in an exbD gene reduces tagetitoxin production by Pseudomonas syringae pv. tagetis.
abstract: A mutant of Pseudomonas syringae pv. tagetis EB037 with limited ability to produce tagetitoxin was isolated after transposon mutagenesis and the mutation was characterized. The mutation occurred in a gene with a high degree of sequence identity to exbD. exbD is contiguous with tonB and exbB upstream and with a gene for a TonB-dependent receptor downstream. Using reverse transcription - polymerase chain reaction with RNA from the wild-type and exbD mutant strains, we demonstrated that the mutation in exbD did not have a polar affect on the expression of downstream genes. The exbD mutant was able to grow well in conditions where iron is not freely available. Siderophore production by the exbD mutant was similar to that of the wild-type strain. We conclude that the mutation in exbD disrupts tagetitoxin production without compromising iron metabolism. The results indicate that tagetitoxin export by P. syringae pv. tagetis involves an efflux pump that requires a functional TonB system that is not essential for normal iron metabolism.
authors.affiliation: US Department of Agriculture, Agricultural Research Service, Sustainable Agricultural Systems Laboratory, Beltsville, MD 20705, USA.
authors.forename: Hyesuk
authors.initials: H
authors.lastname: Kong
authors.forename: Cheryl D
authors.initials: CD
authors.lastname: Patterson
authors.forename: Robin E
authors.initials: RE
authors.lastname: Mitchell
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Buyer
authors.forename: M Catherine
authors.initials: MC
authors.lastname: Aime
authors.forename: John
authors.initials: J
authors.lastname: Lydon
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D003998:Dicarboxylic Acids / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009943:Organophosphorus Compounds / Q000378:metabolism*; D010802:Phylogeny; D044224:Pseudomonas syringae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017262:Siderophores / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003998:Dicarboxylic Acids; D008565:Membrane Proteins; D009943:Organophosphorus Compounds; D017262:Siderophores; C057616:tonB protein, Bacteria; C062221:tagetitoxin; D007501:Iron