jump to searchjump to navigationjump to content

Publications - Stress and Develop Biology

Sort by: Year Type of publication

Displaying results 1 to 8 of 8.

Publications

Sheikh, A. H.; Eschen-Lippold, L.; Pecher, P.; Hoehenwarter, W.; Sinha, A. K.; Scheel, D.; Lee, J.; Regulation of WRKY46 Transcription Factor Function by Mitogen-Activated Protein Kinases in Arabidopsis thaliana Front. Plant Sci. 7, 61, (2016) DOI: 10.3389/fpls.2016.00061

Mitogen-activated protein kinase (MAPK) cascades are central signaling pathways activated in plants after sensing internal developmental and external stress cues. Knowledge about the downstream substrate proteins of MAPKs is still limited in plants. We screened Arabidopsis WRKY transcription factors as potential targets downstream of MAPKs, and concentrated on characterizing WRKY46 as a substrate of the MAPK, MPK3. Mass spectrometry revealed in vitro phosphorylation of WRKY46 at amino acid position S168 by MPK3. However, mutagenesis studies showed that a second phosphosite, S250, can also be phosphorylated. Elicitation with pathogen-associated molecular patterns (PAMPs), such as the bacterial flagellin-derived flg22 peptide led to in vivo destabilization of WRKY46 in Arabidopsis protoplasts. Mutation of either phosphorylation site reduced the PAMP-induced degradation of WRKY46. Furthermore, the protein for the double phosphosite mutant is expressed at higher levels compared to wild-type proteins or single phosphosite mutants. In line with its nuclear localization and predicted function as a transcriptional activator, overexpression of WRKY46 in protoplasts raised basal plant defense as reflected by the increase in promoter activity of the PAMP-responsive gene, NHL10, in a MAPK-dependent manner. Thus, MAPK-mediated regulation of WRKY46 is a mechanism to control plant defense.
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.
Publications

Weyhe, M.; Eschen-Lippold, L.; Pecher, P.; Scheel, D.; Lee, J.; Ménage à trois: The complex relationships between mitogen-activated protein kinases, WRKY transcription factors, and VQ-motif-containing proteins Plant Signal Behav. 9, e29519, (2014) DOI: 10.4161/psb.29519

Out of the 34 members of the VQ-motif-containing protein (VQP) family, 10 are phosphorylated by the mitogen-activated protein kinases (MAPKs), MPK3 and MPK6. Most of these MPK3/6-targeted VQPs (MVQs) interacted with specific sub-groups of WRKY transcription factors in a VQ-motif-dependent manner. In some cases, the MAPK appears to phosphorylate either the MVQ or the WRKY, while in other cases, both proteins have been reported to act as MAPK substrates. We propose a network of dynamic interactions between members from the MAPK, MVQ and WRKY families – either as binary or as tripartite interactions. The compositions of the WRKY-MVQ transcriptional protein complexes may change – for instance, through MPK3/6-mediated modulation of protein stability – and therefore control defense gene transcription.
Publications

Vogel, M. O.; Moore, M.; König, K.; Pecher, P.; Alsharafa, K.; Lee, J.; Dietz, K.-J.; Fast Retrograde Signaling in Response to High Light Involves Metabolite Export, MITOGEN-ACTIVATED PROTEIN KINASE6, and AP2/ERF Transcription Factors in Arabidopsis Plant Cell 26, 1151-1165, (2014) DOI: 10.1105/tpc.113.121061

Regulation of the expression of nuclear genes encoding chloroplast proteins allows for metabolic adjustment in response to changing environmental conditions. This regulation is linked to retrograde signals that transmit information on the metabolic state of the chloroplast to the nucleus. Transcripts of several APETALA2/ETHYLENE RESPONSE FACTOR transcription factors (AP2/ERF-TFs) were found to respond within 10 min after transfer of low-light-acclimated Arabidopsis thaliana plants to high light. Initiation of this transcriptional response was completed within 1 min after transfer to high light. The fast responses of four AP2/ERF genes, ERF6, RRTF1, ERF104, and ERF105, were entirely deregulated in triose phosphate/phosphate translocator (tpt) mutants. Similarly, activation of MITOGEN-ACTIVATED PROTEIN KINASE6 (MPK6) was upregulated after 1 min in the wild type but not in the tpt mutant. Based on this, together with altered transcript regulation in mpk6 and erf6 mutants, a retrograde signal transmission model is proposed starting with metabolite export through the triose phosphate/phosphate translocator with subsequent MPK6 activation leading to initiation of AP2/ERF-TF gene expression and other downstream gene targets. The results show that operational retrograde signaling in response to high light involves a metabolite-linked pathway in addition to previously described redox and hormonal pathways.
Publications

Bethke, G.; Pecher, P.; Eschen-Lippold, L.; Tsuda, K.; Katagiri, F.; Glazebrook, J.; Scheel, D.; Lee, J.; Activation of the Arabidopsis thaliana Mitogen-Activated Protein Kinase MPK11 by the Flagellin-Derived Elicitor Peptide, flg22 Mol. Plant Microbe Interact. 25, 471-480, (2012) DOI: 10.1094/MPMI-11-11-0281

Mitogen-activated protein kinases (MAPK) mediate cellular signal transduction during stress responses, as well as diverse growth and developmental processes in eukaryotes. Pathogen infection or treatments with conserved pathogen-associated molecular patterns (PAMPs) such as the bacterial flagellin-derived flg22 peptide are known to activate three Arabidopsis thaliana MAPK: MPK3, MPK4, and MPK6. Several stresses, including flg22 treatment, are known to increase MPK11 expression but activation of MPK11 has not been shown. Here, we show that MPK11 activity can, indeed, be increased through flg22 elicitation. A small-scale microarray for profiling defense-related genes revealed that cinnamyl alcohol dehyrogenase 5 requires MPK11 for full flg22-induced expression. An mpk11 mutant showed increased flg22-mediated growth inhibition but no altered susceptibility to Pseudomonas syringae, Botrytis cinerea, or Alternaria brassicicola. In mpk3, mpk6, or mpk4 backgrounds, MPK11 is required for embryo or seed development or general viability. Although this developmental deficiency in double mutants and the lack of or only subtle mpk11 phenotypes suggest functional MAPK redundancies, comparison with the paralogous MPK4 reveals distinct functions. Taken together, future investigations of MAPK roles in stress signaling should include MPK11 as a fourth PAMP-activated MAPK.
Publications

Ranf, S.; Grimmer, J.; Pöschl, Y.; Pecher, P.; Chinchilla, D.; Scheel, D.; Lee, J.; Defense-Related Calcium Signaling Mutants Uncovered via a Quantitative High-Throughput Screen in Arabidopsis thaliana Mol. Plant 5, 115-130, (2012) DOI: 10.1093/mp/ssr064

Calcium acts as a second messenger for signaling to a variety of stimuli including MAMPs (Microbe-Associated Molecular Patterns), such as flg22 and elf18 that are derived from bacterial flagellin and elongation factor Tu, respectively. Here, Arabidopsis thaliana mutants with changed calcium elevation (cce) in response to flg22 treatment were isolated and characterized. Besides novel mutant alleles of the flg22 receptor, FLS2 (Flagellin-Sensitive 2), and the receptor-associated kinase, BAK1 (Brassinosteroid receptor 1-Associated Kinase 1), the new cce mutants can be categorized into two main groups—those with a reduced or an enhanced calcium elevation. Moreover, cce mutants from both groups show differential phenotypes to different sets of MAMPs. Thus, these mutants will facilitate the discovery of novel components in early MAMP signaling and bridge the gaps in current knowledge of calcium signaling during plant–microbe interactions. Last but not least, the screening method is optimized for speed (covering 384 plants in 3 or 10 h) and can be adapted to genetically dissect any other stimuli that induce a change in calcium levels.
Publications

Eschen-Lippold, L.; Bethke, G.; Palm-Forster, M. A. T.; Pecher, P.; Bauer, N.; Glazebrook, J.; Scheel, D.; Lee, J.; MPK11—a fourth elicitor-responsive mitogen-activated protein kinase in Arabidopsis thaliana Plant Signal Behav. 7, 1203-1205, (2012) DOI: 10.4161/psb.21323

Recognition of pathogen attack or elicitation with pathogen-associated molecular patterns (PAMPs) leads to defense signaling that includes activation of the three mitogen-activated protein kinases (MPKs), MPK3, MPK4 and MPK6 in Arabidopsis. Recently, we demonstrated the activation of a fourth MPK, MPK11, after treatment with flg22, a 22 amino acid PAMP derived from bacterial flagellin. Here, we extended the study by examining elicitation with two other PAMPs, elf18 (derived from bacterial elongation factor EF-Tu) and ch8 (N-acetylchitooctaose derived from fungal chitin). Both PAMPs led to rapid MPK11 transcript accumulation and increased MPK11 kinase activity, suggesting that multiple PAMPs (or stresses) can activate MPK11. However, probably due to functional redundancies, bacteria-induced phytoalexin accumulation does not absolutely require MPK11.
Publications

Ranf, S.; Eschen-Lippold, L.; Pecher, P.; Lee, J.; Scheel, D.; Interplay between calcium signalling and early signalling elements during defence responses to microbe- or damage-associated molecular patterns Plant J. 68, 100-113, (2011) DOI: 10.1111/j.1365-313X.2011.04671.x

While diverse microbe‐ or damage‐associated molecular patterns (MAMPs/DAMPs) typically trigger a common set of intracellular signalling events, comparative analysis between the MAMPs flg22 and elf18 revealed MAMP‐specific differences in Ca2+ signalling, defence gene expression and MAMP‐mediated growth arrest in Arabidopsis thaliana. Such MAMP‐specific differences are, in part, controlled by BAK1, a kinase associated with several receptors. Whereas defence gene expression and growth inhibition mediated by flg22 were reduced in bak1 mutants, BAK1 had no or minor effects on the same responses elicited by elf18. As the residual Ca2+ elevations induced by diverse MAMPs/DAMPs (flg22, elf18 and Pep1) were virtually identical in bak1 mutants, a differential BAK1‐mediated signal amplification to attain MAMP/DAMP‐specific Ca2+ amplitudes in wild‐type plants may be hypothesized. Furthermore, abrogation of reactive oxygen species (ROS) accumulation, either in the rbohD mutant or through inhibitor application, led to loss of a second Ca2+ peak, demonstrating a feedback effect of ROS on Ca2+ signalling. Conversely, mpk3 mutants showed a prolonged accumulation of ROS but this did not significantly impinge on the overall Ca2+ response. Thus, fine‐tuning of MAMP/DAMP responses involves interplay between diverse signalling elements functioning both up‐ or downstream of Ca2+ signalling.
IPB Mainnav Search