MAPKKKalpha is a positive regulator of cell death associated with both plant immunity and disease.
Many plant pathogens cause disease symptoms that manifest over days as regions of localized cell death. Localized cell death (the hypersensitive response; HR) also occurs in disease-resistant plants, but this response appears within hours of attempted infection and may restrict further pathogen growth. We identified a MAP kinase kinase kinase gene (MAPKKKalpha) that is required for the HR and resistance against Pseudomonas syringae. Significantly, we found that MAPKKKalpha also regulates cell death in susceptible leaves undergoing P. syringae infection. Overexpression of MAPKKKalpha in leaves activated MAPKs and caused pathogen-independent cell death. By overexpressing MAPKKKalpha in leaves and suppressing expression of various MAPKK and MAPK genes by virus-induced gene silencing, we identified two distinct MAPK cascades that act downstream of MAPKKKalpha. These results demonstrate that signal transduction pathways associated with both plant immunity and disease susceptibility share a common molecular switch.
Boyce Thompson Institute for Plant Research, Ithaca, NY, USA.
Olga
O
del Pozo
Kerry F
KF
Pedley
Gregory B
GB
Martin
D000595:Amino Acid Sequence; D016923:Cell Death; D004198:Disease Susceptibility; D004789:Enzyme Activation; D018506:Gene Expression Regulation, Plant; D020930:MAP Kinase Kinase Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D044224:Pseudomonas syringae / Q000502:physiology; D016415:Sequence Alignment; D014026:Nicotiana / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology
D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases