The Arabidopsis thaliana mitogen-activated protein kinases MPK3 and MPK6 target a subclass of 'VQ-motif'-containing proteins to regulate immune responses.
Mitogen-activated protein kinase (MAPK) cascades play key roles in plant immune signalling, and elucidating their regulatory functions requires the identification of the pathway-specific substrates. We used yeast two-hybrid interaction screens, in vitro kinase assays and mass spectrometry-based phosphosite mapping to study a family of MAPK substrates. Site-directed mutagenesis and promoter-reporter fusion studies were performed to evaluate the impact of substrate phosphorylation on downstream signalling. A subset of the Arabidopsis thaliana VQ-motif-containing proteins (VQPs) were phosphorylated by the MAPKs MPK3 and MPK6, and renamed MPK3/6-targeted VQPs (MVQs). When plant protoplasts (expressing these MVQs) were treated with the flagellin-derived peptide flg22, several MVQs were destabilized in vivo. The MVQs interact with specific WRKY transcription factors. Detailed analysis of a representative member of the MVQ subset, MVQ1, indicated a negative role in WRKY-mediated defence gene expression - with mutation of the VQ-motif abrogating WRKY binding and causing mis-regulation of defence gene expression. We postulate the existence of a variety of WRKY-VQP-containing transcriptional regulatory protein complexes that depend on spatio-temporal VQP and WRKY expression patterns. Defence gene transcription can be modulated by changing the composition of these complexes - in part - through MAPK-mediated VQP degradation.
['Pecher|Pascal|P|', 'Eschen-Lippold|Lennart|L|', 'Herklotz|Siska|S|', 'Kuhle|Katja|K|', 'Naumann|Kai|K|', 'Bethke|Gerit|G|', 'Uhrig|Joachim|J|', 'Weyhe|Martin|M|', 'Scheel|Dierk|D|', 'Lee|Justin|J|']
D020816:Amino Acid Motifs D000595:Amino Acid Sequence D017360:Arabidopsis D029681:Arabidopsis Proteins D005408:Flagellin D018506:Gene Expression Regulation, Plant D020929:Mitogen-Activated Protein Kinase Kinases D020928:Mitogen-Activated Protein Kinases D008969:Molecular Sequence Data D016297:Mutagenesis, Site-Directed D010766:Phosphorylation D010935:Plant Diseases D030821:Plants, Genetically Modified D055550:Protein Stability D014157:Transcription Factors
immunity mitogen-activated protein kinase (MAPK) signalling phosphorylation defence VQ-motif pathogen-associated molecular pattern (PAMP)