Induction of systemic resistance in tomato by N-acyl-L-homoserine lactone-producing rhizosphere bacteria.
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.
Schuhegger
Regina
R
Institute of Biochemical Plant Pathology, GSF National Research Center for Environment and Health, Ingolstädter Landstr. 1, D-85764 Neuherberg, Germany.
Ihring
Alexandra
A
Gantner
Stephan
S
Bahnweg
Günther
G
Knappe
Claudia
C
Vogg
Gerd
G
Hutzler
Peter
P
Schmid
Michael
M
Van Breusegem
Frank
F
Eberl
Leo
L
Hartmann
Anton
A
Langebartels
Christian
C
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*
D017931:DNA Primers; C088386:homoserine lactone; D015107:4-Butyrolactone