title: Quorum sensing in the plant pathogen Erwinia carotovora subsp. carotovora: the role of expR(Ecc).
abstract: The production of the main virulence determinants of the plant pathogen Erwinia carotovora subsp. carotovora, the extracellular cell wall-degrading enzymes, is partly controlled by the diffusible signal molecule N-(3-oxohexanoyl)-L-homoserine lactone (OHHL). OHHL is synthesized by the product of the expI/carI gene. Linked to expI we found a gene encoding a putative transcriptional regulator of the LuxR-family. This gene, expR(Ecc), is transcribed convergently to the expI gene and the two open reading frames are partially overlapping. The ExpR(Ecc) protein showed extensive amino acid sequence similarity to the repressor EsaR from Pantoea stewartii subsp. stewartii (formerly Erwinia stewartii subsp. stewartii) and to the ExpR(Ech) protein of Erwinia chrysanthemi. Inactivation of the E. carotovora subsp. carotovora expR(Ecc) gene caused no decrease in virulence or production of virulence determinants in vitro. In contrast, there was a slight increase in the maceration capacity of the mutant strain. The effects of ExpR(Ecc) were probably mediated by changes in OHHL levels. Inactivation of expR(Ecc) resulted in increased OHHL levels during early logarithmic growth. In addition, overexpression of expR(Ecc) caused a clear decrease in the production of virulence determinants and part of this effect was likely to be caused by OHHL binding to ExpR(Ecc). ExpR(Ecc) did not appear to exhibit transcriptional regulation of expI, but the effect on OHHL was apparently due to other mechanisms.
authors.affiliation: Department of Plant Biology, Uppsala Genetic Center, Swedish University of Agricultural Sciences.
authors.forename: R A
authors.initials: RA
authors.lastname: Andersson
authors.forename: A R
authors.initials: AR
authors.lastname: Eriksson
authors.forename: R
authors.initials: R
authors.lastname: Heikinheimo
authors.forename: A
authors.initials: A
authors.lastname: Mäe
authors.forename: M
authors.initials: M
authors.lastname: Pirhonen
authors.forename: V
authors.initials: V
authors.lastname: Kõiv
authors.forename: H
authors.initials: H
authors.lastname: Hyytiäinen
authors.forename: A
authors.initials: A
authors.lastname: Tuikkala
authors.forename: E T
authors.initials: ET
authors.lastname: Palva
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016973:Pectobacterium carotovorum / Q000235:genetics* / Q000472:pathogenicity; D010944:Plants / Q000382:microbiology*; D010947:Plants, Toxic; D011485:Protein Binding; D016415:Sequence Alignment; D011198:Solanum tuberosum / Q000382:microbiology; D014026:Nicotiana / Q000382:microbiology; D015534:Trans-Activators; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C115748:ExpR protein, Erwinia; D015534:Trans-Activators; C081685:expI protein, Erwinia