zur Suche springenzur Navigation springenzum Inhalt springen

Publikationen - Stress- und Entwicklungsbiologie

Sortieren nach: Erscheinungsjahr sort ascending Typ der Publikation

Zeige Ergebnisse 31 bis 40 von 279.

Publikation

Lee, J.; Klessig, D. F.; Nürnberger, T.; A Harpin Binding Site in Tobacco Plasma Membranes Mediates Activation of the Pathogenesis-Related Gene HIN1 Independent of Extracellular Calcium but Dependent on Mitogen-Activated Protein Kinase Activity Plant Cell 13, 1079-1093, (2001) DOI: 10.1105/tpc.13.5.1079

Harpin from the bean halo-blight pathogen Pseudomonas syringae pv phaseolicola (harpinPsph) elicits the hypersensitive response and the accumulation of pathogenesis-related gene transcripts in the nonhost plant tobacco. Here, we report the characterization of a nonproteinaceous binding site for harpinPsph in tobacco plasma membranes, which is assumed to mediate the activation of plant defense responses in a receptor-like manner. Binding of 125I-harpinPsph to tobacco microsomal membranes (dissociation constant = 425 nM) and protoplasts (dissociation constant = 380 nM) was specific, reversible, and saturable. A close correlation was found between the abilities of harpinPsph fragments to elicit the transcript accumulation of the pathogenesis-related tobacco gene HIN1 and to compete for binding of 125I-harpinPsph to its binding site. Another elicitor of the hypersensitive response and HIN1 induction in tobacco, the Phytophthora megasperma–derived β-elicitin β-megaspermin, failed to bind to the putative harpinPsph receptor. In contrast to activation by β-megaspermin, harpinPsph-induced activation of the 48-kD salicylic acid–responsive mitogen-activated protein kinase (MAPK) and HIN1 transcript accumulation were independent of extracellular calcium. Moreover, use of the MAPK kinase inhibitor U0126 revealed that MAPK activity was essential for pathogenesis-related gene expression in harpinPsph-treated tobacco cells. Thus, a receptor-mediated MAPK-dependent signaling pathway may mediate the activation of plant defense responses induced by harpinPsph.
Publikation

Göbel, C.; Feussner, I.; Schmidt, A.; Scheel, D.; Sanchez-Serrano, J.; Hamberg, M.; Rosahl, S.; Oxylipin Profiling Reveals the Preferential Stimulation of the 9-Lipoxygenase Pathway in Elicitor-treated Potato Cells J. Biol. Chem. 276, 6267-6273, (2001) DOI: 10.1074/jbc.M008606200

Lipoxygenases are key enzymes in the synthesis of oxylipins and play an important role in the response of plants to wounding and pathogen attack. In cultured potato cells treated with elicitor from Phytophthora infestans, the causal agent of late blight disease, transcripts encoding a linoleate 9-lipoxygenase and a linoleate 13-lipoxygenase accumulate. However, lipoxygenase activity assays and oxylipin profiling revealed only increased 9-lipoxygenase activity and formation of products derived therefrom, such as 9-hydroxy octadecadienoic acid and colneleic acid. Furthermore, the 9-lipoxygenase products 9(S),10(S),11(R)-trihydroxy-12(Z)-octadecenoic and 9(S),10(S),11(R)-trihydroxy-12(Z),15(Z)-octadecadienoic acid were identified as novel, elicitor-inducible oxylipins in potato, suggesting a role of these compounds in the defense response against pathogen attack. Neither 13-lipoxygenase activity nor 13-lipoxygenase products were detected in higher amounts in potato cells after elicitation. Thus, formation of products by the 9-lipoxygenase pathway, including the enzymes hydroperoxide reductase, divinyl ether synthase, and epoxy alcohol synthase, is preferentially stimulated in cultured potato cells in response to treatment with P. infestanselicitor. Moreover, elicitor-induced accumulation of desaturase transcripts and increased phospholipase A2 activity after elicitor treatment suggest that substrates for the lipoxygenase pathway might be provided by de novo synthesis and subsequent release from lipids of the endomembrane system.
Publikation

Clemens, S.; Molecular mechanisms of plant metal tolerance and homeostasis Planta 212, 475-486, (2001) DOI: 10.1007/s004250000458

Transition metals such as copper are essential for many physiological processes yet can be toxic at elevated levels. Other metals (e.g. lead) are nonessential and potentially highly toxic. Plants – like all other organisms – possess homeostatic mechanisms to maintain the correct concentrations of essential metal ions in different cellular compartments and to minimize the damage from exposure to nonessential metal ions. A regulated network of metal transport, chelation, trafficking and sequestration activities functions to provide the uptake, distribution and detoxification of metal ions. Some of the components of this network have now been identified: a number of uptake transporters have been cloned as well as candidate transporters for the vacuolar sequestration of metals. Chelators and chaperones are known, and evidence for intracellular metal trafficking is emerging. This recent progress in the molecular understanding of plant metal homeostasis and tolerance is reviewed.
Publikation

Clemens, S.; Developing tools for phytoremediation:towards a molecular understanding of plant metal tolerance and accumulation Int. J. Occup. Med. Environ. Health 14, 235-239, (2001)

Certain plant species and genotypes are able to accumulate large quantities of heavy metals in their shoots. Based on this trait the concept of phytoremediation was developed, i.e. the use of metal hyperaccumulating plants for the cleansing of contaminated soils and water. In order to more efficiently use this capacity, an engineering of plants might be needed. However, very little is known about the underlying molecular mechanisms. Our work is focussing on the identification and characterization of plant genes involved in plant metal uptake, tolerance and accumulation. Phytochelatins are small glutathione-derived metal-binding peptides which are part of the plant metal detoxification system. Genes encoding phytochelatin synthases have been cloned and are now being studied with regard to their regulation, biochemistry and biotechnological potential. Another project aimes at the dissection of metal responses in the metallophyte Arabidopsis halleri. This plant, a close relative to the model plant Arabidopsis thaliana, is Cd hypertolerant and Zn hyperaccumulating. It grows,for instance, on medieval mining sites in the Harz mountains in Germany and in many other metal-contaminated sites in Central Europe. We have isolated metal-regulated genes from A.halleri and molecularly analyzed interesting candidate genes with regard to their function and involvement in metal accumulation and tolerance.
Publikation

Clemens, S.; Schroeder, J. I.; Degenkolb, T.; Caenorhabditis elegans expresses a functional phytochelatin synthase Eur. J. Biochem. 268, 3640-3643, (2001) DOI: 10.1046/j.1432-1327.2001.02293.x

The formation of phytochelatins, small metal‐binding glutathione‐derived peptides, is one of the well‐studied responses of plants to toxic metal exposure. Phytochelatins have also been detected in some fungi and some marine diatoms. Genes encoding phytochelatin synthases (PCS) have recently been cloned from Arabidopsis , wheat and Schizosaccharomyces pombe . Surprisingly, database searches revealed the presence of a homologous gene in the Caenorhabditis elegans genome, DDBJ/EMBL/GenBank accession no. 266513. Here we show that C. elegans indeed expresses a gene coding for a functional phytochelatin synthase. CePCS complements the Cd2+ sensitivity of a Schizosaccharomyces pombe PCS knock‐out strain and confers phytochelatin synthase activity to these cells. Thus, phytochelatins may play a role for metal homeostasis also in certain animals.
Publikation

Cazalé, A.-C.; Clemens, S.; Arabidopsis thaliana expresses a second functional phytochelatin synthase FEBS Lett. 507, 215-219, (2001) DOI: 10.1016/S0014-5793(01)02976-3

Phytochelatins represent a major detoxifying pathway for heavy metals in plants and many other organisms. The Arabidopsis thaliana CAD1 (=AtPCS1 ) gene encodes a phytochelatin synthase and cad1 mutants are phytochelatin deficient and cadmium hypersensitive. The Arabidopsis genome contains a highly homologous gene, AtPCS2 , of which expression and function were studied in order to understand the apparent non‐redundancy of the two genes. Low constitutive AtPCS2 expression is detected in all plant organs analyzed. The AtPCS2 gene encodes a functional phytochelatin synthase as shown by expression in Saccharomyces cerevisiae and the complementation of a Schizosaccharomyces pombe phytochelatin synthase knockout strain.
Publikation

Ichimura, K.; Shinozaki, K.; Tena, G.; Sheen, J.; Henry, Y.; Champion, A.; Kreis, M.; Zhang, S.; Hirt, H.; Wilson, C.; Heberle-Bors, E.; Ellis, B. E.; Morris, P. C.; Innes, R. W.; Ecker, J. R.; Scheel, D.; Klessig, D. F.; Machida, Y.; Mundy, J.; Ohashi, Y.; Walker, J. C.; Mitogen-activated protein kinase cascades in plants: a new nomenclature Trends Plant Sci. 7, 301-308, (2002) DOI: 10.1016/S1360-1385(02)02302-6

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules in eukaryotes, including yeasts, animals and plants. These protein phosphorylation cascades link extracellular stimuli to a wide range of cellular responses. In plants, MAPK cascades are involved in responses to various biotic and abiotic stresses, hormones, cell division and developmental processes. Completion of the Arabidopsis genome-sequencing project has revealed the existence of 20 MAPKs, 10 MAPK kinases and 60 MAPK kinase kinases. Here, we propose a simplified nomenclature for Arabidopsis MAPKs and MAPK kinases that might also serve as a basis for standard annotation of these gene families in all plants.
Publikation

Göbel, C.; Feussner, I.; Hamberg, M.; Rosahl, S.; Oxylipin profiling in pathogen-infected potato leaves BBA-Mol. Cell Biol. Lipids 1584, 55-64, (2002) DOI: 10.1016/S1388-1981(02)00268-8

Plants respond to pathogen attack with a multicomponent defense response. Synthesis of oxylipins via the lipoxygenase (LOX) pathway appears to be an important factor for establishment of resistance in a number of pathosystems. In potato cells, pathogen-derived elicitors preferentially stimulate the 9-LOX-dependent metabolism of polyunsaturated fatty acids (PUFAs). Here we show by oxylipin profiling that potato plants react to pathogen infection with increases in the amounts of the 9-LOX-derived 9,10,11- and 9,12,13-trihydroxy derivatives of linolenic acid (LnA), the divinyl ethers colnelenic acid (CnA) and colneleic acid (CA) as well as 9-hydroxy linolenic acid. Accumulation of these compounds is faster and more pronounced during the interaction of potato with the phytopathogenic bacterium Pseudomonas syringae pv. maculicola, which does not lead to disease, compared to the infection of potato with Phytophthora infestans, the causal agent of late blight disease. Jasmonic acid (JA), a 13-LOX-derived oxylipin, accumulates in potato leaves after infiltration with P. syringae pv. maculicola, but not after infection with P. infestans.
Publikation

Fiegen, M.; Knogge, W.; Amino acid alterations in isoforms of the effector protein NIP1 from Rhynchosporium secalis have similar effects on its avirulence- and virulence-associated activities on barley Physiol. Mol. Plant Pathol. 61, 299-302, (2002) DOI: 10.1006/pmpp.2002.0442

The secreted effector protein NIP1 from the barley pathogen Rhynchosporium secalis is a specific elicitor of defense reactions in host plants carrying the resistance gene Rrs1. In addition, it has activities associated with fungal virulence; independent of the plant genotype it stimulates the plant plasma membrane H+-ATPase and induces leaf necrosis. Four NIP1 isoforms differing in single amino acid residues were isolated from various naturally occurring fungal strains. All three activities of the protein (race specificity, H+-ATPase stimulation, necrosis induction) were affected by the amino acid alterations in a similar way suggesting that they are mediated through a single plant receptor.
Publikation

Clemens, S.; Bloss, T.; Vess, C.; Neumann, D.; Nies, D. H.; zur Nieden, U.; A Transporter in the Endoplasmic Reticulum of Schizosaccharomyces pombe Cells Mediates Zinc Storage and Differentially Affects Transition Metal Tolerance J. Biol. Chem. 277, 18215-18221, (2002) DOI: 10.1074/jbc.M201031200

The cation diffusion facilitator (CDF) family represents a class of ubiquitous metal transporters. Inactivation of a CDF in Schizosaccharomyces pombe, Zhf, causes drastically different effects on the tolerance toward various metals. A deletion mutant is Zn2+/Co2+-hypersensitive yet displays significantly enhanced Cd2+ and Ni2+ tolerance. Accumulation of zinc, cobalt, and cadmium is reduced in mutant cells. Non-vacuolar zinc content, as measured by analytical electron microscopy, is lower in zhf− cells compared with wild-type cells in the presence of elevated Zn2+concentrations. The protective effect against cadmium toxicity is independent of the phytochelatin detoxification pathway. Phytochelatin synthase-deficient cells show extremely enhanced (about 200-fold) cadmium tolerance when zhf is disrupted. Immunogold labeling indicates endoplasmic reticulum (ER) localization of Zhf. Electron spectroscopic imaging shows that accumulation of zinc coincides with Zhf localization, demonstrating a major role of the ER for metal storage and the involvement of Zhf in cellular zinc homeostasis. Also, these observations indicate that Cd2+ions exert their toxic effects on cellular metabolism in the ER rather than in the cytosol.
  • Die Leibniz-Gemeinschaft
  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
IPB Mainnav Search