title: The Erwinia chrysanthemi phoP-phoQ operon plays an important role in growth at low pH, virulence and bacterial survival in plant tissue.
abstract: We have studied the role of acidic pH as a barrier for the colonization of the plant apoplast by Erwinia chrysanthemi. A minitransposon containing a promoterless reporter gene, gus, was used for random mutagenesis of the bacterial genome. An acid-sensitive mutant, named BT119, was isolated and had the following differential features with respect to the wild-type strain: (i) inability to grow at pH </= 5.5; (ii) decreased survival at acid pH and in plant tissues; (iii) increased susceptibility to antimicrobial peptides; (iv) decreased virulence in chicory leaves and pear fruits; (v) reduced polygalacturonase production; and (vi) reduced ability to alkalinize chicory tissues after infection. The sequence of the interrupted gene was highly similar to the phoQ gene, which is involved in environmental sensing in several bacteria, such as Yersinia pseudotuberculosis, Erwinia carotovora, Salmonella typhimurium and Escherichia coli and thus, this designation was used for the E. chrysanthemi system. This gene was induced at low Mg(2+) concentrations and in planta. These results suggest that E. chrysanthemi PhoP-PhoQ system plays an important role in bacterial survival in plant tissues during the initial infection stages.
authors.affiliation: Departamento de Biotecnología-UPM, E. T. S. Ingenieros Agrónomos, E-28040 Madrid, Spain.
authors.forename: Arancha
authors.initials: A
authors.lastname: Llama-Palacios
authors.forename: Emilia
authors.initials: E
authors.lastname: López-Solanilla
authors.forename: César
authors.initials: C
authors.lastname: Poza-Carrión
authors.forename: Francisco
authors.initials: F
authors.lastname: García-Olmedo
authors.forename: Pablo
authors.initials: P
authors.lastname: Rodríguez-Palenzuela
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology*; D016974:Dickeya chrysanthemi / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D010944:Plants / Q000033:anatomy & histology / Q000382:microbiology*; D011096:Polygalacturonase / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; C079792:PhoQ protein, Bacteria; C061064:PhoP protein, Bacteria; D011096:Polygalacturonase; D008274:Magnesium; D002118:Calcium