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Publications - Stress and Develop Biology

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Publications

Mönchgesang, S.; Strehmel, N.; Schmidt, S.; Westphal, L.; Taruttis, F.; Müller, E.; Herklotz, S.; Neumann, S.; Scheel, D.; Natural variation of root exudates in Arabidopsis thaliana-linking metabolomic and genomic data Sci. Rep. 6, 29033, (2016) DOI: 10.1038/srep29033

Many metabolomics studies focus on aboveground parts of the plant, while metabolism within roots and the chemical composition of the rhizosphere, as influenced by exudation, are not deeply investigated. In this study, we analysed exudate metabolic patterns of Arabidopsis thaliana and their variation in genetically diverse accessions. For this project, we used the 19 parental accessions of the Arabidopsis MAGIC collection. Plants were grown in a hydroponic system, their exudates were harvested before bolting and subjected to UPLC/ESI-QTOF-MS analysis. Metabolite profiles were analysed together with the genome sequence information. Our study uncovered distinct metabolite profiles for root exudates of the 19 accessions. Hierarchical clustering revealed similarities in the exudate metabolite profiles, which were partly reflected by the genetic distances. An association of metabolite absence with nonsense mutations was detected for the biosynthetic pathways of an indolic glucosinolate hydrolysis product, a hydroxycinnamic acid amine and a flavonoid triglycoside. Consequently, a direct link between metabolic phenotype and genotype was detected without using segregating populations. Moreover, genomics can help to identify biosynthetic enzymes in metabolomics experiments. Our study elucidates the chemical composition of the rhizosphere and its natural variation in A. thaliana, which is important for the attraction and shaping of microbial communities.
Publications

Pecher, P.; Eschen-Lippold, L.; Herklotz, S.; Kuhle, K.; Naumann, K.; Bethke, G.; Uhrig, J.; Weyhe, M.; Scheel, D.; Lee, J.; The Arabidopsis thaliana mitogen-activated protein kinases MPK3 and MPK6 target a subclass of ‘VQ-motif’-containing proteins to regulate immune responses New Phytol. 203, 592-606, (2014) DOI: 10.1111/nph.12817

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.
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