The MAP kinase substrate MKS1 is a regulator of plant defense responses.
Arabidopsis MAP kinase 4 (MPK4) functions as a regulator of pathogen defense responses, because it is required for both repression of salicylic acid (SA)-dependent resistance and for activation of jasmonate (JA)-dependent defense gene expression. To understand MPK4 signaling mechanisms, we used yeast two-hybrid screening to identify the MPK4 substrate MKS1. Analyses of transgenic plants and genome-wide transcript profiling indicated that MKS1 is required for full SA-dependent resistance in mpk4 mutants, and that overexpression of MKS1 in wild-type plants is sufficient to activate SA-dependent resistance, but does not interfere with induction of a defense gene by JA. Further yeast two-hybrid screening revealed that MKS1 interacts with the WRKY transcription factors WRKY25 and WRKY33. WRKY25 and WRKY33 were shown to be in vitro substrates of MPK4, and a wrky33 knockout mutant was found to exhibit increased expression of the SA-related defense gene PR1. MKS1 may therefore contribute to MPK4-regulated defense activation by coupling the kinase to specific WRKY transcription factors.
Molecular Biology Institute, University of Copenhagen, Copenhagen, Denmark.
Erik
E
Andreasson
Thomas
T
Jenkins
Peter
P
Brodersen
Stephan
S
Thorgrimsen
Nikolaj H T
NH
Petersen
Shijiang
S
Zhu
Jin-Long
JL
Qiu
Pernille
P
Micheelsen
Anne
A
Rocher
Morten
M
Petersen
Mari-Anne
MA
Newman
Henrik
H
Bjørn Nielsen
Heribert
H
Hirt
Imre
I
Somssich
Ole
O
Mattsson
John
J
Mundy
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D020869:Gene Expression Profiling; D007113:Immunity, Innate; D007150:Immunohistochemistry; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010944:Plants / Q000201:enzymology* / Q000276:immunology; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013379:Substrate Specificity; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; C503586:MKS1 protein, Arabidopsis; D009687:Nuclear Proteins; D010750:Phosphoproteins; C436292:AtMPK4 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases