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Publications - Stress and Develop Biology

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Displaying results 1 to 8 of 8.

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

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

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

Widjaja, I.; Lassowskat, I.; Bethke, G.; Eschen-Lippold, L.; Long, H.-H.; Naumann, K.; Dangl, J. L.; Scheel, D.; Lee, J.; A protein phosphatase 2C, responsive to the bacterial effector AvrRpm1 but not to the AvrB effector, regulates defense responses in Arabidopsis Plant J. 61, 249-258, (2010) DOI: 10.1111/j.1365-313X.2009.04047.x

Using a proteomics approach, a PP2C‐type phosphatase (renamed PIA1, for PP2C induced by AvrRpm1) was identified that accumulates following infection by Pseudomonas syringae expressing the type III effector AvrRpm1, and subsequent activation of the corresponding plant NB‐LRR disease resistance protein RPM1. No accumulation of PIA1 protein was seen following infection with P. syringae expressing AvrB, another type III effector that also activates RPM1, although PIA transcripts were observed. Accordingly, mutation of PIA1 resulted in enhanced RPM1 function in response to P. syringae pathover tomato (Pto) DC3000 (avrRpm1) but not to Pto DC3000 (avrB). Thus, PIA1 is a protein marker that distinguishes AvrRpm1‐ and AvrB‐dependent activation of RPM1. AvrRpm1‐induced expression of the pathogenesis‐related genes PR1, PR2 and PR3, and salicylic acid accumulation were reduced in two pia1 mutants. By contrast, expression of other defense‐related genes, including PR5 and PDF1.2 (plant defensin), was elevated in unchallenged pia1 mutants. Hence, PIA1 is required for AvrRpm1‐induced responses, and confers dual (both positive and negative) regulation of defense gene expression.
Publications

Camehl, I.; Sherameti, I.; Venus, Y.; Bethke, G.; Varma, A.; Lee, J.; Oelmüller, R.; Ethylene signalling and ethylene-targeted transcription factors are required to balance beneficial and nonbeneficial traits in the symbiosis between the endophytic fungus Piriformospora indica and Arabidopsis thaliana New Phytol. 185, 1062-1073, (2010) DOI: 10.1111/j.1469-8137.2009.03149.x

The endophytic fungus Piriformospora indica colonizes the roots of the model plant Arabidopsis thaliana and promotes its growth and seed production. The fungus can be cultivated in axenic culture without a host, and therefore this is an excellent system to investigate plant–fungus symbiosis.The growth of etr1, ein2 and ein3/eil1 mutant plants was not promoted or even inhibited by the fungus; the plants produced less seeds and the roots were more colonized compared with the wild‐type. This correlates with a mild activation of defence responses. The overexpression of ETHYLENE RESPONSE FACTOR1 constitutively activated defence responses, strongly reduced root colonization and abolished the benefits for the plants.Piriformospora indica‐mediated stimulation of growth and seed yield was not affected by jasmonic acid, and jasmonic acid‐responsive promoter β‐glucuronidase gene constructs did not respond to the fungus in Arabidopsis roots.We propose that ethylene signalling components and ethylene‐targeted transcription factors are required to balance beneficial and nonbeneficial traits in the symbiosis. The results show that the restriction of fungal growth by ethylene signalling components is required for the beneficial interaction between the two symbionts.
Publications

Brock, A. K.; Willmann, R.; Kolb, D.; Grefen, L.; Lajunen, H. M.; Bethke, G.; Lee, J.; Nürnberger, T.; Gust, A. A.; The Arabidopsis Mitogen-Activated Protein Kinase Phosphatase PP2C5 Affects Seed Germination, Stomatal Aperture, and Abscisic Acid-Inducible Gene Expression Plant Physiol. 153, 1098-1111, (2010) DOI: 10.1104/pp.110.156109

Abscisic acid (ABA) is an important phytohormone regulating various cellular processes in plants, including stomatal opening and seed germination. Although protein phosphorylation via mitogen-activated protein kinases (MAPKs) has been suggested to be important in ABA signaling, the corresponding phosphatases are largely unknown. Here, we show that a member of the Protein Phosphatase 2C (PP2C) family in Arabidopsis (Arabidopsis thaliana), PP2C5, is acting as a MAPK phosphatase. The PP2C5 protein colocalizes and directly interacts with stress-induced MPK3, MPK4, and MPK6, predominantly in the nucleus. Importantly, altered PP2C5 levels affect MAPK activation. Whereas Arabidopsis plants depleted of PP2C5 show an enhanced ABA-induced activation of MPK3 and MPK6, ectopic expression of PP2C5 in tobacco (Nicotiana benthamiana) resulted in the opposite effect, with the two MAPKs salicylic acid-induced protein kinase and wound-induced protein kinase not being activated any longer after ABA treatment. Moreover, depletion of PP2C5, whose gene expression itself is affected by ABA treatment, resulted in altered ABA responses. Loss-of-function mutation in PP2C5 or AP2C1, a close PP2C5 homolog, resulted in an increased stomatal aperture under normal growth conditions and a partial ABA-insensitive phenotype in seed germination that was most prominent in the pp2c5 ap2c1 double mutant line. In addition, the response of ABA-inducible genes such as ABI1, ABI2, RD29A, and Erd10 was reduced in the mutant plants. Thus, we suggest that PP2C5 acts as a MAPK phosphatase that positively regulates seed germination, stomatal closure, and ABA-inducible gene expression.
Publications

Bethke, G.; Scheel, D.; Lee, J.; Sometimes new results raise new questions: the question marks between mitogen-activated protein kinase and ethylene signaling Plant Signal Behav. 4, 672-674, (2009) DOI: 10.4161/psb.4.7.9039

In Arabidopsis thaliana, mitogen activated protein kinase (MAPK) signaling cascades that contain MPK3, MPK4 and MPK6 have been implicated in various aspects of developmental processes and stress responses. We identified an ethylene response factor (ERF104), which controls innate immunity, to be a specific substrate of MPK6 and showed that ethylene signaling regulates the release of the ERF104 substrate from its kinase. Implications and questions that arise from our findings are addressed. To promote discussions, previously unpublished data, that are rather confounding, are presented and possible explanation provided on how these may fit into our current model.
Publications

Bethke, G.; Unthan, T.; Uhrig, J. F.; Pöschl, Y.; Gust, A. A.; Scheel, D.; Lee, J.; Flg22 regulates the release of an ethylene response factor substrate from MAP kinase 6 in Arabidopsis thaliana via ethylene signaling Proc. Natl. Acad. Sci. U.S.A. 106, 8067-8072, (2009) DOI: 10.1073/pnas.0810206106

Mitogen-activated protein kinase (MAPK)–mediated responses are in part regulated by the repertoire of MAPK substrates, which is still poorly elucidated in plants. Here, the in vivo enzyme–substrate interaction of the Arabidopsis thaliana MAP kinase, MPK6, with an ethylene response factor (ERF104) is shown by fluorescence resonance energy transfer. The interaction was rapidly lost in response to flagellin-derived flg22 peptide. This complex disruption requires not only MPK6 activity, which also affects ERF104 stability via phosphorylation, but also ethylene signaling. The latter points to a novel role of ethylene in substrate release, presumably allowing the liberated ERF104 to access target genes. Microarray data show enrichment of GCC motifs in the promoters of ERF104–up-regulated genes, many of which are stress related. ERF104 is a vital regulator of basal immunity, as altered expression in both erf104 and overexpressors led to more growth inhibition by flg22 and enhanced susceptibility to a non-adapted bacterial pathogen.
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