title: Induction of systemic resistance in tomato by N-acyl-L-homoserine lactone-producing rhizosphere bacteria.
abstract: N-acyl-L-homoserine lactone (AHL) signal molecules are utilized by Gram-negative bacteria to monitor their population density (quorum sensing) and to regulate gene expression in a density-dependent manner. We show that Serratia liquefaciens MG1 and Pseudomonas putida IsoF colonize tomato roots, produce AHL in the rhizosphere and increase systemic resistance of tomato plants against the fungal leaf pathogen, Alternaria alternata. The AHL-negative mutant S. liquefaciens MG44 was less effective in reducing symptoms and A. alternata growth as compared to the wild type. Salicylic acid (SA) levels were increased in leaves when AHL-producing bacteria colonized the rhizosphere. No effects were observed when isogenic AHL-negative mutant derivatives were used in these experiments. Furthermore, macroarray and Northern blot analysis revealed that AHL molecules systemically induce SA- and ethylene-dependent defence genes (i.e. PR1a, 26 kDa acidic and 30 kDa basic chitinase). Together, these data support the view that AHL molecules play a role in the biocontrol activity of rhizobacteria through the induction of systemic resistance to pathogens.
authors.affiliation: Institute of Biochemical Plant Pathology, GSF National Research Center for Environment and Health, Ingolstädter Landstr. 1, D-85764 Neuherberg, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Schuhegger
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ihring
authors.forename: Stephan
authors.initials: S
authors.lastname: Gantner
authors.forename: Günther
authors.initials: G
authors.lastname: Bahnweg
authors.forename: Claudia
authors.initials: C
authors.lastname: Knappe
authors.forename: Gerd
authors.initials: G
authors.lastname: Vogg
authors.forename: Peter
authors.initials: P
authors.lastname: Hutzler
authors.forename: Michael
authors.initials: M
authors.lastname: Schmid
authors.forename: Frank
authors.initials: F
authors.lastname: Van Breusegem
authors.forename: Leo
authors.initials: L
authors.lastname: Eberl
authors.forename: Anton
authors.initials: A
authors.lastname: Hartmann
authors.forename: Christian
authors.initials: C
authors.lastname: Langebartels
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000096:biosynthesis; D000528:Alternaria / Q000502:physiology*; D001483:Base Sequence; D015152:Blotting, Northern; D017931:DNA Primers; D018551:Solanum lycopersicum / Q000382:microbiology / Q000502:physiology*; D018613:Microscopy, Confocal; D016958:Pseudomonas putida / Q000502:physiology*; D053038:Quorum Sensing; D044090:Serratia liquefaciens / Q000502:physiology*
chemical_list: D017931:DNA Primers; C088386:homoserine lactone; D015107:4-Butyrolactone