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.

Pseudomonas aeruginosa Lon and ClpXP proteases: roles in linking carbon catabolite repression system with quorum-sensing system

“…However, the roles of ATP-dependent proteases are only starting to be understood in P. aeruginosa. There is an increasing body of evidence showing that ATPdependent proteases such as Lon and ClpXP play crucial roles in the regulation of virulence-associated traits and the virulence of Pseudomonas species (Breidenstein and Hancock 2013;Takeuchi et al 2014;Yang et al 2015;Lan et al 2007;Breidenstein et al 2012;Fernandez et al 2012;Yang et al 2011;Losada and Hutcheson 2005;Bretz et al 2002). In this regard, ATP-dependent proteases may be good entry points to explore the mechanisms that make P. aeruginosa a successful pathogen, which will contribute to the development of new therapeutics against P. aeruginosa.…”

Protein Export According to Schedule: Architecture, Assembly, and Regulation of Type III Secretion Systems from Plant- and Animal-Pathogenic Bacteria

“…The Lon protease is an ATP-dependent serine protease that is involved in the degradation of unstable or misfolded proteins and can contribute to the regulation of T3S genes (464,551). In P. syringae, the Lon protease acts as a negative regulator by degrading HrpR, specifically under T3S-repressing conditions (54,303,420,612). Notably, the Lon protease is also involved in the degradation of effector proteins from P. syringae.…”

Exogenous N‐acyl‐homoserine lactones enhance the expression of flagella of Pseudomonas syringae and activate defence responses in plants

“…For strain construction and virulence tests, P. syringae 11528 was grown at 30 ºC in King's B medium (KB) (Cha et al ., ) and Escherichia coli was grown in Luria–Bertani (LB) broth, supplemented with antibiotics, when appropriate, at the following concentrations: ampicillin, 50 µg/mL; spectinomycin, 50 µg/mL. For transcript profiling, P. syringae 11528 was grown in M9MM supplemented with 5 m m mannitol (Yang et al ., ), and synthetic AHLs were added to the medium at final concentrations of 2 μ m for C6‐HSL and 2 μ m for 3OC6‐HSL or both AHLs before inoculation. The optical density at inoculation was OD 600 = 0.05 (Chugani et al ., ).…”