Innate immunity in Arabidopsis thaliana: lipopolysaccharides activate nitric oxide synthase (NOS) and induce defense genes.
Lipopolysaccharides (LPS) are cell-surface components of Gram-negative bacteria and are microbe-/pathogen-associated molecular patterns in animal pathosystems. As for plants, the molecular mechanisms of signal transduction in response to LPS are not known. Here, we show that Arabidopsis thaliana reacts to LPS with a rapid burst of NO, a hallmark of innate immunity in animals. Fifteen LPS preparations (among them Burkholderia cepacia, Pseudomonas aeruginosa, and Erwinia carotovora) as well as lipoteichoic acid from Gram-positive Staphylococcus aureus were found to trigger NO production in suspension-cultured Arabidopsis cells as well as in leaves. NO was detected by confocal laser-scanning microscopy in conjunction with the fluorophore 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate, by electron paramagnetic resonance, and by a NO synthase (NOS) assay. The source of NO was addressed by using T-DNA insertion lines. Interestingly, LPS did not activate the pathogen-inducible varP NOS, but AtNOS1, a distinct NOS previously associated with hormonal signaling in plants. A prominent feature of LPS treatment was activation of defense genes, which proved to be mediated by NO. Northern analyses and transcription profiling by using DNA microarrays revealed induction of defense-associated genes both locally and systemically. Finally, AtNOS1 mutants showed dramatic susceptibility to the pathogen Pseudomonas syringae pv. tomato DC3000. In sum, perception of LPS and induction of NOS contribute toward the activation of plant defense responses.
Zeidler
Dana
D
Institute of Biochemical Plant Pathology, GSF-National Research Center for Environment and Health, D-85764 Neuherberg, Germany.
Zähringer
Ulrich
U
Gerber
Isak
I
Dubery
Ian
I
Hartung
Thomas
T
Bors
Wolf
W
Hutzler
Peter
P
Durner
Jörg
J
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D020869:Gene Expression Profiling; D017343:Genes, Plant / Q000187:drug effects; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D044224:Pseudomonas syringae / Q000472:pathogenicity
D008070:Lipopolysaccharides; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase