Autoinduction in Erwinia amylovora: evidence of an acyl-homoserine lactone signal in the fire blight pathogen.
Erwinia amylovora causes fire blight disease of apple, pear, and other members of the Rosaceae. Here we present the first evidence for autoinduction in E. amylovora and a role for an N-acyl-homoserine lactone (AHL)-type signal. Two major plant virulence traits, production of extracellular polysaccharides (amylovoran and levan) and tolerance to free oxygen radicals, were controlled in a bacterial-cell-density-dependent manner. Two standard autoinducer biosensors, Agrobacterium tumefaciens NTL4 and Vibrio harveyi BB886, detected AHL in stationary-phase cultures of E. amylovora. A putative AHL synthase gene, eamI, was partially sequenced, which revealed homology with autoinducer genes from other bacterial pathogens (e.g., carI, esaI, expI, hsII, yenI, and luxI). E. amylovora was also found to carry eamR, a convergently transcribed gene with homology to luxR AHL activator genes in pathogens such as Erwinia carotovora. Heterologous expression of the Bacillus sp. strain A24 acyl-homoserine lactonase gene aiiA in E. amylovora abolished induction of AHL biosensors, impaired extracellular polysaccharide production and tolerance to hydrogen peroxide, and reduced virulence on apple leaves.
Molina
Lázaro
L
Swiss Federal Institute of Technology (ETHZ), Institute for Plant Sciences, Phytopathology Group, Zürich, Switzerland. molina@staff.uni-marburg.de
Rezzonico
Fabio
F
Défago
Geneviève
G
Duffy
Brion
B
D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D013437:Carbon-Sulfur Lyases; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D024881:Drug Resistance, Bacterial; D044084:Erwinia amylovora / Q000235:genetics* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006714:Homoserine / Q000031:analogs & derivatives* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007783:Lactones / Q000378:metabolism*; D027845:Malus / Q000382:microbiology; D008666:Metalloendopeptidases / Q000235:genetics / Q000502:physiology; D008752:Methylene Chloride / Q000494:pharmacology; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017385:Sequence Homology; D015398:Signal Transduction
D001426:Bacterial Proteins; D007783:Lactones; D011994:Recombinant Proteins; D008752:Methylene Chloride; D006714:Homoserine; D006861:Hydrogen Peroxide; D002265:Carboxylic Ester Hydrolases; C432003:N-acyl homoserine lactonase; C406735:AiiA protein, Bacillus; D008666:Metalloendopeptidases; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria