title: Global regulators ExpA (GacA) and KdgR modulate extracellular enzyme gene expression through the RsmA-rsmB system in Erwinia carotovora subsp. carotovora.
abstract: The production of the main virulence determinants, the extracellular plant cell wall-degrading enzymes, and hence virulence of Erwinia carotovora subsp. carotovora is controlled by a complex regulatory network. One of the global regulators, the response regulator ExpA, a GacA homolog, is required for transcriptional activation of the extracellular enzyme genes of this soft-rot pathogen. To elucidate the mechanism of ExpA control as well as interactions with other regulatory systems, we isolated second-site transposon mutants that would suppress the enzyme-negative phenotype of an expA (gacA) mutant. Inactivation of kdgR resulted in partial restoration of extracellular enzyme production and virulence to the expA mutant, suggesting an interaction between the two regulatory pathways. This interaction was mediated by the RsmA-rsmB system. Northern analysis was used to show that the regulatory rsmB RNA was under positive control of ExpA. Conversely, the expression of rsmA encoding a global repressor was under negative control of ExpA and positive control of KdgR. This study indicates a central role for the RsmA-rsmB regulatory system during pathogenesis, integrating signals from the ExpA (GacA) and KdgR global regulators of extracellular enzyme production in E. carotovora subsp. carotovora.
authors.affiliation: Department of Biosciences, University of Helsinki, Finland.
authors.forename: H
authors.initials: H
authors.lastname: Hyytiäinen
authors.forename: M
authors.initials: M
authors.lastname: Montesano
authors.forename: E T
authors.initials: ET
authors.lastname: Palva
mesh_terms: D001426:Bacterial Proteins; D010450:Endopeptidases / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D016254:Mutagenesis, Insertional; D016973:Pectobacterium carotovorum / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity*; D010935:Plant Diseases / Q000382:microbiology*; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D011198:Solanum tuberosum / Q000382:microbiology; D014157:Transcription Factors
chemical_list: D001426:Bacterial Proteins; C113708:ExpA protein, Erwinia carotovora; C098628:KdgR protein, Erwinia chrysanthemi; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C095468:RsmA protein, Erwinia carotovora; D014157:Transcription Factors; C115187:rsmb protein, Erwinia carotovora; D010450:Endopeptidases