zur Suche springenzur Navigation springenzum Inhalt springen

Publikationen - Stress- und Entwicklungsbiologie

Sortieren nach: Erscheinungsjahr Typ der Publikation

Zeige Ergebnisse 1 bis 10 von 14.

Publikation

Qutob, D.; Kemmerling, B.; Brunner, F.; Küfner, I.; Engelhardt, S.; Gust, A. A.; Luberacki, B.; Seitz, H. U.; Stahl, D.; Rauhut, T.; Glawischnig, E.; Schween, G.; Lacombe, B.; Watanabe, N.; Lam, E.; Schlichting, R.; Scheel, D.; Nau, K.; Dodt, G.; Hubert, D.; Gijzen, M.; Nürnberger, T.; Phytotoxicity and Innate Immune Responses Induced by Nep1-Like Proteins Plant Cell 18, 3721-3744, (2006) DOI: 10.1105/tpc.106.044180

We show that oomycete-derived Nep1 (for necrosis and ethylene-inducing peptide1)–like proteins (NLPs) trigger a comprehensive immune response in Arabidopsis thaliana, comprising posttranslational activation of mitogen-activated protein kinase activity, deposition of callose, production of nitric oxide, reactive oxygen intermediates, ethylene, and the phytoalexin camalexin, as well as cell death. Transcript profiling experiments revealed that NLPs trigger extensive reprogramming of the Arabidopsis transcriptome closely resembling that evoked by bacteria-derived flagellin. NLP-induced cell death is an active, light-dependent process requiring HSP90 but not caspase activity, salicylic acid, jasmonic acid, ethylene, or functional SGT1a/SGT1b. Studies on animal, yeast, moss, and plant cells revealed that sensitivity to NLPs is not a general characteristic of phospholipid bilayer systems but appears to be restricted to dicot plants. NLP-induced cell death does not require an intact plant cell wall, and ectopic expression of NLP in dicot plants resulted in cell death only when the protein was delivered to the apoplast. Our findings strongly suggest that NLP-induced necrosis requires interaction with a target site that is unique to the extracytoplasmic side of dicot plant plasma membranes. We propose that NLPs play dual roles in plant pathogen interactions as toxin-like virulence factors and as triggers of plant innate immune responses.
Publikation

Knogge, W.; Scheel, D.; LysM receptors recognize friend and foe Proc. Natl. Acad. Sci. U.S.A. 103, 10829-10830, (2006) DOI: 10.1073/pnas.0604601103

0
Publikation

Hamel, L.-P.; Nicole, M.-C.; Sritubtim, S.; Morency, M.-J.; Ellis, M.; Ehlting, J.; Beaudoin, N.; Barbazuk, B.; Klessig, D.; Lee, J.; Martin, G.; Mundy, J.; Ohashi, Y.; Scheel, D.; Sheen, J.; Xing, T.; Zhang, S.; Seguin, A.; Ellis, B. E.; Ancient signals: comparative genomics of plant MAPK and MAPKK gene families Trends Plant Sci. 11, 192-198, (2006) DOI: 10.1016/j.tplants.2006.02.007

MAPK signal transduction modules play crucial roles in regulating many biological processes in plants, and their components are encoded by highly conserved genes. The recent availability of genome sequences for rice and poplar now makes it possible to examine how well the previously described Arabidopsis MAPK and MAPKK gene family structures represent the broader evolutionary situation in plants, and analysis of gene expression data for MPK and MKK genes in all three species allows further refinement of those families, based on functionality. The Arabidopsis MAPK nomenclature appears sufficiently robust to allow it to be usefully extended to other well-characterized plant systems.
Publikation

Halim, V. A.; Vess, A.; Scheel, D.; Rosahl, S.; The Role of Salicylic Acid and Jasmonic Acid in Pathogen Defence Plant Biol. 8, 307-313, (2006) DOI: 10.1055/s-2006-924025

Phytohormones are not only instrumental in regulating developmental processes in plants but also play important roles for the plant's responses to biotic and abiotic stresses. In particular, abscisic acid, ethylene, jasmonic acid, and salicylic acid have been shown to possess crucial functions in mediating or orchestrating stress responses in plants. Here, we review the role of salicylic acid and jasmonic acid in pathogen defence responses with special emphasis on their function in the solanaceous plant potato.
Publikation

Grzam, A.; Tennstedt, P.; Clemens, S.; Hell, R.; Meyer, A. J.; Vacuolar sequestration of glutathione S-conjugates outcompetes a possible degradation of the glutathione moiety by phytochelatin synthase FEBS Lett. 580, 6384-6390, (2006) DOI: 10.1016/j.febslet.2006.10.050

Monochlorobimane was used as a model xenobiotic for Arabidopsis to directly monitor the compartmentation of glutathione‐bimane conjugates in situ and to quantify degradation intermediates in vitro. Vacuolar sequestration of the conjugate was very fast and outcompeted carboxypeptidation to the γ‐glutamylcysteine‐bimane intermediate (γ‐EC‐B) by phytochelatin synthase (PCS) in the cytosol. Following vacuolar sequestration, degradation proceeded to cysteine‐bimane without intermediate. Only co‐infiltration of monochlorobimane with Cd2+ and Cu2+ increased γ‐EC‐B formation to 4% and 25%, respectively, within 60 min. The role of PCS under simultaneous heavy metal stress was confirmed by investigation of different pcs1 null‐mutants. In the absence of elevated heavy metal concentrations glutathione‐conjugates are therefore first sequestered to the vacuole and subsequently degraded with the initial breakdown step being rate‐limiting.
Publikation

Consonni, C.; Humphry, M. E.; Hartmann, H. A.; Livaja, M.; Durner, J.; Westphal, L.; Vogel, J.; Lipka, V.; Kemmerling, B.; Schulze-Lefert, P.; Somerville, S. C.; Panstruga, R.; Conserved requirement for a plant host cell protein in powdery mildew pathogenesis Nat. Genet. 38, 716-720, (2006) DOI: 10.1038/ng1806

In the fungal phylum Ascomycota, the ability to cause disease in plants and animals has been gained and lost repeatedly during phylogenesis1. In monocotyledonous barley, loss-of-function mlo alleles result in effective immunity against the Ascomycete Blumeria graminis f. sp. hordei, the causal agent of powdery mildew disease2,3. However, mlo-based disease resistance has been considered a barley-specific phenomenon to date. Here, we demonstrate a conserved requirement for MLO proteins in powdery mildew pathogenesis in the dicotyledonous plant species Arabidopsis thaliana. Epistasis analysis showed that mlo resistance in A. thaliana does not involve the signaling molecules ethylene, jasmonic acid or salicylic acid, but requires a syntaxin, glycosyl hydrolase and ABC transporter4,5,6. These findings imply that a common host cell entry mechanism of powdery mildew fungi evolved once and at least 200 million years ago, suggesting that within the Erysiphales (powdery mildews) the ability to cause disease has been a stable trait throughout phylogenesis.
Publikation

Clemens, S.; Toxic metal accumulation, responses to exposure and mechanisms of tolerance in plants Biochimie 88, 1707-1719, (2006) DOI: 10.1016/j.biochi.2006.07.003

Over the past 200 years emissions of toxic heavy metals have risen tremendously and significantly exceed those from natural sources for practically all metals. Uptake and accumulation by crop plants represents the main entry pathway for potentially health-threatening toxic metals into human and animal food. Of major concern are the metalloids arsenic (As) and selenium (Se), and the metals cadmium (Cd), mercury (Hg), and lead (Pb). This review discusses the molecular mechanisms of toxic metal accumulation in plants and algae, the responses to metal exposure, as well as our understanding of metal tolerance and its evolution. The main emphasis will be on cadmium, which is by far the most widely studied of the non-essential toxic metals/metalloids. Entry via Zn2+, Fe2+, and Ca2+ transporters is the molecular basis of Cd2+ uptake into plant cells. Much less is known about the partitioning of non-essential metals and about the genes underlying the enormous diversity among plants with respect to Cd accumulation in different tissues. Numerous studies have described symptoms and responses of plants upon toxic metal exposure. Mysterious are primary targets of toxicity, the degree of specificity of responses, the sensing and the signaling events that lead to transcriptional activation. All plants apparently possess a basal tolerance of toxic non-essential metals. For Cd and As, this is largely dependent on the phytochelatin pathway. Not understood is the molecular biology of Cd hypertolerance in certain plant species such as the metallophytes Arabidopsis halleri or Thlaspi caerulescens.
Publikation

Clemens, S.; Evolution and function of phytochelatin synthases J. Plant Physiol. 163, 319-332, (2006) DOI: 10.1016/j.jplph.2005.11.010

Both essential and non-essential transition metal ions can easily be toxic to cells. The physiological range for essential metals between deficiency and toxicity is therefore extremely narrow and a tightly controlled metal homeostasis network to adjust to fluctuations in micronutrient availability is a necessity for all organisms. One protective strategy against metal excess is the expression of high-affinity binding sites to suppress uncontrolled binding of metal ions to physiologically important functional groups. The synthesis of phytochelatins, glutathione-derived metal binding peptides, represents the major detoxification mechanism for cadmium and arsenic in plants and an unknown range of other organisms. A few years ago genes encoding phytochelatin synthases (PCS) were cloned from plants, fungi and nematodes. Since then it has become apparent that PCS genes are far more widespread than ever anticipated. Searches in sequence databases indicate PCS expression in representatives of all eukaryotic kingdoms and the presence of PCS-like proteins in several prokaryotes. The almost ubiquitous presence in the plant kingdom and beyond as well as the constitutive expression of PCS genes and PCS activity in all major plant tissues are still mysterious. It is unclear, how the extremely rare need to cope with an excess of cadmium or arsenic ions could explain the evolution and distribution of PCS genes. Possible answers to this question are discussed. Also, the molecular characterization of phytochelatin synthases and our current knowledge about the enzymology of phytochelatin synthesis are reviewed.
Publikation

Birschwilks, M.; Haupt, S.; Hofius, D.; Neumann, S.; Transfer of phloem-mobile substances from the host plants to the holoparasite Cuscuta sp. J. Exp. Bot. 57, 911-921, (2006) DOI: 10.1093/jxb/erj076

During the development of the haustorium, searching hyphae of the parasite and the host parenchyma cells are connected by plasmodesmata. Using transgenic tobacco plants expressing a GFP-labelled movement protein of the tobacco mosaic virus, it was demonstrated that the interspecific plasmodesmata are open. The transfer of substances in the phloem from host to the parasite is not selective. After simultaneous application of 3H-sucrose and 14C-labelled phloem-mobile amino acids, phytohormones, and xenobiotica to the host, corresponding percentages of the translocated compounds are found in the parasite. An open continuity between the host phloem and the Cuscuta phloem via the haustorium was demonstrated in CLSM pictures after application of the phloem-mobile fluorescent probes, carboxyfluorescein (CF) and hydroxypyrene trisulphonic acid (HPTS), to the host. Using a Cuscuta bridge 14C-sucrose and the virus PVYN were transferred from one host plant to the another. The results of translocation experiments with labelled compounds, phloem-mobile dyes and the virus should be considered as unequivocal evidence for a symplastic transfer of phloem solutes between Cuscuta species and their compatible hosts.
Publikation

Weber, M.; Trampczynska, A.; Clemens, S.; Comparative transcriptome analysis of toxic metal responses in Arabidopsis thaliana and the Cd2+-hypertolerant facultative metallophyte Arabidopsis halleri Plant Cell Environ. 29, 950-963, (2006) DOI: 10.1111/j.1365-3040.2005.01479.x

Toxic effects of both essential and non‐essential heavy metals are well documented in plants. Very little is known, however, about their modes of toxicity, about tolerance mechanisms and the signalling cascades involved in mediating transcriptional responses to toxic metal excess. We analysed transcriptome changes upon Cd2+ and Cu2+ exposure in roots of Arabidopsis thaliana and the Cd2+‐hypertolerant metallophyte Arabidopsis halleri . Particularly, three categories of genes were identified with the help of this comparative approach: (1) common responses, which might indicate stable and functionally relevant changes conserved across plant species; (2) metallophyte‐specific responses as well as transcripts differentially regulated between the two species, representing candidate genes for Cd2+ hypertolerance; and (3) those specifically responsive to Cd2+ and therefore indicative of toxicity mechanisms or potentially involved in signalling cascades. Our data define, for instance, Arabidopsis core responses to Cd2+ and Cu2+. In addition, they suggest that Cd2+ exposure very rapidly results in apparent Zn deficiency, and they show the existence of highly specific Cd2+ responses and distinct signalling cascades. Array results were independently confirmed by real‐time quantitative PCR, thereby further validating cross‐species transcriptome analysis with oligonucleotide microarrays.
  • Die Leibniz-Gemeinschaft
  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
IPB Mainnav Search