Negative Regulation of Pathogenesis in Pseudomonas syringae pv. tabaci 11528 by ATP-Dependent Lon Protease

• Published in: Molecules and cells 2011-10, Vol.32 (4), p.317-324
• Main Authors: Yang, H.J., Pusan National University, Busan, Republic of Korea, Lee, J.S., Pusan National University, Busan, Republic of Korea, Cha, J.Y., Pusan National University, Busan, Republic of Korea, Baik, H.S., Pusan National University, Busan, Republic of Korea
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biochemistry; Biomedical and Life Sciences; Biomedicine; Biotechnology; Cell Biology; Cells, Cultured; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Down-Regulation - genetics; Gene Expression Regulation, Bacterial; gene regulation; hrp pathogenicity island; Life Sciences; lon mutant; Lon protease; Mutation - genetics; Nicotiana - microbiology; Promoter Regions, Genetic - genetics; Protease La - genetics; Protease La - metabolism; Protein Engineering; Pseudomonas Infections - genetics; Pseudomonas Infections - metabolism; PSEUDOMONAS SYRINGAE; Pseudomonas syringae - genetics; Pseudomonas syringae - pathogenicity; Repressor Proteins - genetics; Repressor Proteins - metabolism; Sigma Factor - genetics; Sigma Factor - metabolism; Transcription Factors - genetics; Transcription Factors - metabolism; Virulence
• ISSN: 1016-8478; 0219-1032
• DOI: 10.1007/s10059-011-1017-3

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.