Phytotoxicity and innate immune responses induced by Nep1-like proteins.
We show that oomycete-derived Nep1 (for necrosis and ethylene-inducing peptide1)-like proteins (NLPs) trigger a comprehensive immune response in Arabidopsis thaliana, comprising posttranslational activation of mitogen-activated protein kinase activity, deposition of callose, production of nitric oxide, reactive oxygen intermediates, ethylene, and the phytoalexin camalexin, as well as cell death. Transcript profiling experiments revealed that NLPs trigger extensive reprogramming of the Arabidopsis transcriptome closely resembling that evoked by bacteria-derived flagellin. NLP-induced cell death is an active, light-dependent process requiring HSP90 but not caspase activity, salicylic acid, jasmonic acid, ethylene, or functional SGT1a/SGT1b. Studies on animal, yeast, moss, and plant cells revealed that sensitivity to NLPs is not a general characteristic of phospholipid bilayer systems but appears to be restricted to dicot plants. NLP-induced cell death does not require an intact plant cell wall, and ectopic expression of NLP in dicot plants resulted in cell death only when the protein was delivered to the apoplast. Our findings strongly suggest that NLP-induced necrosis requires interaction with a target site that is unique to the extracytoplasmic side of dicot plant plasma membranes. We propose that NLPs play dual roles in plant pathogen interactions as toxin-like virulence factors and as triggers of plant innate immune responses.
Qutob
Dinah
D
Agriculture and Agri-Food Canada, London ON N5V 4T3, Canada.
Kemmerling
Birgit
B
Brunner
Frédéric
F
Küfner
Isabell
I
Engelhardt
Stefan
S
Gust
Andrea A
AA
Luberacki
Borries
B
Seitz
Hanns Ulrich
HU
Stahl
Dietmar
D
Rauhut
Thomas
T
Glawischnig
Erich
E
Schween
Gabriele
G
Lacombe
Benoit
B
Watanabe
Naohide
N
Lam
Eric
E
Schlichting
Rita
R
Scheel
Dierk
D
Nau
Katja
K
Dodt
Gabriele
G
Hubert
David
D
Gijzen
Mark
M
Nürnberger
Thorsten
T
D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000382:microbiology* / Q000528:radiation effects; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002462:Cell Membrane / Q000187:drug effects; D003593:Cytoplasm / Q000187:drug effects; D005656:Fungal Proteins / Q000378:metabolism* / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D014644:Genetic Variation; D018525:Germination / Q000187:drug effects / Q000528:radiation effects; D007113:Immunity, Innate / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D008051:Lipid Bilayers / Q000378:metabolism; D010802:Phylogeny; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000382:microbiology / Q000528:radiation effects; D011485:Protein Binding / Q000187:drug effects / Q000528:radiation effects; D036226:Seedlings / Q000187:drug effects / Q000382:microbiology / Q000528:radiation effects; D014026:Nicotiana / Q000187:drug effects / Q000382:microbiology / Q000528:radiation effects
D005656:Fungal Proteins; D008051:Lipid Bilayers