title: Role of RpoS in virulence and stress tolerance of the plant pathogen Erwinia carotovora subsp. carotovora.
abstract: The plant-pathogenic bacterium Erwinia carotovora subsp. carotovora causes plant disease mainly through a number of extracellular plant-cell-wall-degrading enzymes. In this study, the ability of an rpoS mutant of the Er. carotovora subsp. carotovora strain SCC3193 to infect plants and withstand environmental stress was characterized. This mutant was found to be sensitive to osmotic and oxidative stresses in vitro and to be deficient in glycogen accumulation. The production of extracellular enzymes in vitro was similar in the mutant and in the wild-type strains. However, the rpoS mutant caused more severe symptoms than the wild-type strain on tobacco plants and also produced more extracellular enzymes in planta, but did not grow to higher cell density in planta compared to the wild-type strain. When tested on plants with reduced catalase activities, which show higher levels of reactive oxygen species, the rpoS mutant was found to cause lower symptom levels and to have impaired growth. In addition, the mutant was unable to compete with the wild-type strain in planta and in vitro. These results suggest that a functional rpoS gene is needed mainly for survival in a competitive environment and during stress conditions, and not for effective infection of plants.
authors.affiliation: Department of Plant Biology, Swedish University of Agricultural Sciences (SLU), PO Box 7080,SE-75007 Uppsala, Sweden 1.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Andersson
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, EE 2400 Tartu, Republic of Estonia2.
authors.forename: Viia
authors.initials: V
authors.lastname: Kõiv
authors.affiliation: Department of Plant Biology, Swedish University of Agricultural Sciences (SLU), PO Box 7080,SE-75007 Uppsala, Sweden 1.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Norman-Setterblad
authors.affiliation: Department of Plant Biology, Swedish University of Agricultural Sciences (SLU), PO Box 7080,SE-75007 Uppsala, Sweden 1.
authors.forename: Minna
authors.initials: M
authors.lastname: Pirhonen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009997:Osmotic Pressure; D018384:Oxidative Stress; D016973:Pectobacterium carotovorum / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*; D030821:Plants, Genetically Modified / Q000382:microbiology; D010947:Plants, Toxic; D010957:Plasmids / Q000235:genetics; D017422:Sequence Analysis, DNA; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism*; D014026:Nicotiana / Q000382:microbiology; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D006003:Glycogen; D002374:Catalase