title: Negative regulation of pathogenesis in Pseudomonas syringae pv. tabaci 11528 by ATP-dependent Lon protease.
abstract: Pseudomonas syringae pv. tabaci causes wildfire disease in tobacco plants. The hrp pathogenicity island (hrp PAI) of P. syringae pv. tabaci encodes a type III secretion system (TTSS) and its regulatory system, which are required for pathogenesis in plants. Three important regulatory proteins-HrpR, HrpS, and HrpL-have been identified to activate hrp PAI gene expression. The bacterial Lon protease regulates the expression of various genes. To investigate the regulatory mechanism of the Lon protease in P. syringae pv. tabaci 11528, we cloned the lon gene, and then a Δlon mutant was generated by allelic exchange. lon mutants showed increased UV sensitivity, which is a typical feature of such mutants. The Δlon mutant produced higher levels of tabtoxin than the wild-type. The lacZ gene was fused with hrpA promoter and activity of β-galactosidase was measured in hrp-repressing and hrp-inducing media. The Lon protease functioned as a negative regulator of hrp PAI under hrp-repressing conditions. We found that strains with lon disruption elicited the host defense system more rapidly and strongly than the wild-type strain, suggesting that the Lon protease is essential for systemic pathogenesis.
authors: Department of Microbiology, College of Natural Science, Pusan National University, Busan 609-735, Korea.
authors: Hyun Ju
authors: HJ
authors: Yang
authors: Jun Seung
authors: JS
authors: Lee
authors: Ji Young
authors: JY
authors: Cha
authors: Hyung Suk
authors: HS
authors: Baik
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D049070:Protease La / Q000235:genetics / Q000378:metabolism*; D015202:Protein Engineering; D011552:Pseudomonas Infections / Q000235:genetics / Q000378:metabolism*; D044224:Pseudomonas syringae / Q000235:genetics* / Q000472:pathogenicity; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000382:microbiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C085855:HrpL protein, Pseudomonas syringae; C085856:HrpR protein, Pseudomonas syringae; D012097:Repressor Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C060789:hrpS protein, Pseudomonas syringae; D049070:Protease La