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Publications - Stress and Develop Biology

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Publications

Henze, M.; Kreye, O.; Brauch, S.; Nitsche, C.; Naumann, K.; Wessjohann, L. A.; Westermann, B.; Photoaffinity-Labeled Peptoids and Depsipeptides by Multicomponent Reactions Synthesis 2010, 2997-3003, (2010) DOI: 10.1055/s-0030-1258182

Photoaffinity tags can be incorporated easily into peptoids and congeners by the Ugi and Passerini multicomponent reactions. Products related to photo-methionine and photo-leucine can be accomplished by diazirine-containing building blocks. The same protocols can be used to synthesize derivatives with benzophenone photo cross-linkers.
Publications

Eschen-Lippold, L.; Altmann, S.; Gebhardt, C.; Göbel, C.; Feussner, I.; Rosahl, S.; Oxylipins are not required for R gene-mediated resistance in potato Eur. J. Plant Pathol. 127, 437-442, (2010) DOI: 10.1007/s10658-010-9621-1

The role of 9- and 13-lipoxygenase-derived oxylipins for race-cultivar-specific resistance in potato was analyzed by expressing RNA interference constructs against oxylipin biosynthetic genes in transgenic potato plants carrying the resistance gene R1 against Phytophthora infestans. Down-regulation of 9-lipoxygenase expression resulted in highly reduced levels of 9-hydroxyoctadecatrienoic acid after treatment with the pathogen-associated molecular pattern Pep-13. However, neither 9-lipoxygenase nor 9-divinyl ether synthase RNAi plants exhibited alterations in their resistance to P. infestans. Similarly, successful down-regulation of transcript accumulation of the 13-lipoxygenase pathway genes encoding allene oxide cyclase, 12-oxophytodienoic acid reductase 3 and the jasmonic acid receptor coronatine-insensitive 1 resulted in highly reduced levels of jasmonic acid after Pep-13 treatment. Race-cultivar-specific resistance, however, was not lost in these plants. Our results suggest that neither 9-lipoxygenase-derived oxylipins nor jasmonic acid are required for R-gene-mediated resistance in potato. Importantly, in tobacco, the silencing of 9-lipoxygenase expression was previously demonstrated to suppress race-cultivar-specific resistance. Thus, we conclude a differential requirement of oxylipins for R-gene-mediated resistance in different solanaceous plants.
Publications

Eschen-Lippold, L.; Altmann, S.; Rosahl, S.; DL-β-Aminobutyric Acid–Induced Resistance of Potato Against Phytophthora infestans Requires Salicylic Acid but Not Oxylipins Mol. Plant Microbe Interact. 23, 585-592, (2010) DOI: 10.1094/MPMI-23-5-0585

Inducing systemic resistance responses in crop plants is a promising alternative way of disease management. To understand the underlying signaling events leading to induced resistance, functional analyses of plants defective in defined signaling pathway steps are required. We used potato, one of the economically most-important crop plants worldwide, to examine systemic resistance against the devastating late blight pathogen Phytophthora infestans, induced by treatment with dl-β-aminobutyric acid (BABA). Transgenic plants impaired in either the 9-lipoxygenase pathway, which produces defense-related compounds, or the 13-lipoxygenase pathway, which generates jasmonic acid–derived signals, expressed wild-type levels of BABA-induced resistance. Plants incapable of accumulating salicylic acid (SA), on the other hand, failed to mount this type of induced resistance. Consistently, treatment of these plants with the SA analog 2,6-dichloroisonicotinic acid restored BABA-induced resistance. Together, these results demonstrate the indispensability of a functional SA pathway for systemic resistance in potato induced by BABA.
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

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

Noehringer, C.; Scheel, D.; Blée, E.; Lipoxygenase isoforms in elicitor-treated parsley cell suspension cultures Biochem. Soc. Trans. 28, 827-829, (2000) DOI: 10.1042/bst0280827

Treatment of parsley cell cultures with a fungal elicitor triggered the induction of a lipoxygenase isoform which may be involved in the de novo synthesis of defence-response inducers, such as jasmonic acid or 12-oxo-phytodienoic acid.
Publications

Hornung, E.; Rosahl, S.; Kühn, H.; Feussner, I.; Creating lipoxygenases with new positional specificities by site-directed mutagenesis Biochem. Soc. Trans. 28, 825-826, (2000) DOI: 10.1042/bst0280825

In order to analyse the amino acid determinants which alter the positional specificity of plant lipoxygenases (LOXs), multiple LOX sequence alignments and structural modelling of the enzyme-substrate interactions were carried out. These alignments suggested three amino acid residues as the primary determinants of positional specificity. Here we show the generation of two plant LOXs with new positional specificities, a Δ-linoleneate 6-LOX and an arachidonate 11-LOX, by altering only one of these determinants within the active site of two plant LOXs. In the past, site-directed-mutagenesis studies have mainly been carried out with mammalian lipoxygenases (LOXs) [1]. In these experiments two regions have been identified in the primary structure containing sequence determinants for positional specificity. Amino acids aligning with the Sloane determinants [2] are highly conserved among plant LOXs. In contrast, there is amino acid hetero-geneity among plant LOXs at the position that aligns with P353 of the rabbit reticulocyte 15-LOX (Borngräber determinants) [3].
Publications

Blume, B.; Nürnberger, T.; Nass, N.; Scheel, D.; Receptor-Mediated Increase in Cytoplasmic Free Calcium Required for Activation of Pathogen Defense in Parsley Plant Cell 12, 1425-1440, (2000) DOI: 10.1105/tpc.12.8.1425

Transient influx of Ca2+ constitutes an early element of signaling cascades triggering pathogen defense responses in plant cells. Treatment with the Phytophthora sojae–derived oligopeptide elicitor, Pep-13, of parsley cells stably expressing apoaequorin revealed a rapid increase in cytoplasmic free calcium ([Ca2+]cyt), which peaked at ∼1 μM and subsequently declined to sustained values of 300 nM. Activation of this biphasic [Ca2+]cyt signature was achieved by elicitor concentrations sufficient to stimulate Ca2+ influx across the plasma membrane, oxidative burst, and phytoalexin production. Sustained concentrations of [Ca2+]cyt but not the rapidly induced [Ca2+]cyt transient peak are required for activation of defense-associated responses. Modulation by pharmacological effectors of Ca2+ influx across the plasma membrane or of Ca2+ release from internal stores suggests that the elicitor-induced sustained increase of [Ca2+]cyt predominantly results from the influx of extracellular Ca2+. Identical structural features of Pep-13 were found to be essential for receptor binding, increases in [Ca2+]cyt, and activation of defense-associated responses. Thus, a receptor-mediated increase in [Ca2+]cyt is causally involved in signaling the activation of pathogen defense in parsley.
Publications

Abel, S.; Nürnberger, T.; Ahnert, V.; Krauss, G.-J.; Glund, K.; Induction of an Extracellular Cyclic Nucleotide Phosphodiesterase as an Accessory Ribonucleolytic Activity during Phosphate Starvation of Cultured Tomato Cells Plant Physiol. 122, 543-552, (2000) DOI: 10.1104/pp.122.2.543

During growth under conditions of phosphate limitation, suspension-cultured cells of tomato (Lycopersicon esculentum Mill.) secrete phosphodiesterase activity in a similar fashion to phosphate starvation-inducible ribonuclease (RNase LE), a cyclizing endoribonuclease that generates 2′:3′-cyclic nucleoside monophosphates (NMP) as its major monomeric products (T. Nürnberger, S. Abel, W. Jost, K. Glund [1990] Plant Physiol 92: 970–976). Tomato extracellular phosphodiesterase was purified to homogeneity from the spent culture medium of phosphate-starved cells and was characterized as a cyclic nucleotide phosphodiesterase. The purified enzyme has a molecular mass of 70 kD, a pH optimum of 6.2, and an isoelectric point of 8.1. The phosphodiesterase preparation is free of any detectable deoxyribonuclease, ribonuclease, and nucleotidase activity. Tomato extracellular phosphodiesterase is insensitive to EDTA and hydrolyzes with no apparent base specificity 2′:3′-cyclic NMP to 3′-NMP and the 3′:5′-cyclic isomers to a mixture of 3′-NMP and 5′-NMP. Specific activities of the enzyme are 2-fold higher for 2′:3′-cyclic NMP than for 3′:5′-cyclic isomers. Analysis of monomeric products of sequential RNA hydrolysis with purified RNase LE, purified extracellular phosphodiesterase, and cleared −Pi culture medium as a source of 3′-nucleotidase activity indicates that cyclic nucleotide phosphodiesterase functions as an accessory ribonucleolytic activity that effectively hydrolyzes primary products of RNase LE to substrates for phosphate-starvation-inducible phosphomonoesterases. Biosynthetical labeling of cyclic nucleotide phopshodiesterase upon phosphate starvation suggests de novo synthesis and secretion of a set of nucleolytic enzymes for scavenging phosphate from extracellular RNA substrates.
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