Pseudomonas syringaedual‐function protein Lon switches between virulence and metabolism by acting as bothDNA‐binding transcriptional regulator and protease in different environments

Abstract

Summary Lon, a member of the AAA+ protease family, plays vital roles in Type III secretion systems (T3SS), agglutination and colony shape in the model plant pathogen Pseudomonas syringae. Lon also functions as a transcriptional regulator in other bacterial species such as Escherichia coli and Brevibacillus thermoruber. To reveal the molecular mechanisms of Lon as a dual‐function protein in P. syringae, we studied Lon‐regulated genes by using RNA sequencing (RNA‐seq), chromatin immunoprecipitation sequencing (ChIP‐seq) and liquid chromatography–tandem mass spectrometry. As a transcriptional regulator, Lon directly regulated a group of genes (PSPPH_4788, gacA, fur, gntR, clpS, lon and glyA) and consequently regulated their functions, such as 1‐dodecanol oxidation activity, motility, pyoverdine production, glucokinase activity, N‐end rule pathway, lon expression and serine hydroxymethyltransferase activity. Mass spectrometry results revealed that the expression levels of five T3SS proteins (such as HrcV, HrpW1) were higher in the ∆lon strain than the wild‐type (WT) strain in KB. In MM, 12 metabolic proteins (such as AcdS and NuoI) showed lower levels in the ∆lon strain than the WT strain. Taken together, these data demonstrate that the dual‐function protein Lon sophisticatedly regulates virulence and metabolism in P. syringae.

Integrated regulatory network in Pseudomonas syringae reveals dynamics of virulence

“…Lon functions as a suppressor of DrhpS (Zhou et al, 2016). Lon also regulates virulence and metabolism by acting as both transcription factor (TF) and protease in different environments (Hua et al, 2020). In addition, our previous study shows that HrpS directly regulates the expression of T3SS genes independent of the HrpL pathway and non-T3SS genes (Wang et al, 2018).…”

Signal transduction schemes in Pseudomonas syringae

“…When acting as a protease, Lon cuts several T3SS effectors (including AvrB2, HrpW1 and HrcV) in KB but degrades metabolic factors (including NuoI and NoxB) in MM. [113] , [114] , [115] , [116] , [117] HrpR and HrpS Intracellular surveillance system Unknown HrpR and HrpS form a heterodimer to directly activates the transcription of hrpL . HrpS alone regulates T3SS, motility and biofilm formation.…”

“…By using multi-omic approaches, including ChIP-seq, RNA-seq and liquid chromatography-tandem mass spectrometry, our recent study demonstrates the different roles of Lon in response to different external signals [117] . As a DNA-binding transcriptional regulator, Lon directly mediates several metabolic pathways, including 1-dodecanol oxidation, glucokinase activity and pyoverdine production [117] .…”

“…By using multi-omic approaches, including ChIP-seq, RNA-seq and liquid chromatography-tandem mass spectrometry, our recent study demonstrates the different roles of Lon in response to different external signals [117] . As a DNA-binding transcriptional regulator, Lon directly mediates several metabolic pathways, including 1-dodecanol oxidation, glucokinase activity and pyoverdine production [117] . When acting as a protease, Lon proteolyses a group of T3SS effectors (including AvrB2, HrpW1 and HrcV) in KB but degrades metabolic factors (including NuoI and NoxB) in MM, suggesting that its protease activity depends on the extracellular environment [117] .…”

“…As a DNA-binding transcriptional regulator, Lon directly mediates several metabolic pathways, including 1-dodecanol oxidation, glucokinase activity and pyoverdine production [117] . When acting as a protease, Lon proteolyses a group of T3SS effectors (including AvrB2, HrpW1 and HrcV) in KB but degrades metabolic factors (including NuoI and NoxB) in MM, suggesting that its protease activity depends on the extracellular environment [117] .…”