Abstract
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.
Original language | English (US) |
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Pages (from-to) | 592-606 |
Number of pages | 15 |
Journal | New Phytologist |
Volume | 203 |
Issue number | 2 |
DOIs | |
State | Published - Jul 2014 |
Keywords
- Defence
- Immunity
- Mitogen-activated protein kinase (MAPK)
- Pathogen-associated molecular pattern (PAMP)
- Phosphorylation
- Signalling
- VQ-motif