Pseudomonas syringae dual‐function protein Lon switches between virulence and metabolism by acting as both DNA‐binding transcriptional regulator and protease in different environments

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 . syringa e.