Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
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Wollgiehn, R.; Neumann, D.;Metal Stress Response and Tolerance of Cultured Cells from Silene vulgaris and Lycopersicon peruvianum: Role of Heat Stress ProteinsJ. Plant Physiol.154547-553(1999)DOI: 10.1016/S0176-1617(99)80296-X
The influence of the heavy metal ions Hg++, Cu++, Cd++ and Zn++ and of arsenite on growth, amino acid uptake, protein- and heat shock protein synthesis was investigated in cell cultures of a heavy metal tolerant Silene vulgaris and the sensitive Lycopersicon peruvianum.A distinct tolerance of Silene cell growth in comparison to tomato cells against Cu, Cd and Zn was observed. Synthesis of the small heat stress proteins was induced in both species, however, with quantitative differences depending on species and metal ion. While in tomato cells all metals induce HSP synthesis, in Silene the induction by Cu and Cd was found to be significantly lower in comparison to Hg and arsenite, and Zn did not induce HSP. Therefore, generally a lower tolerance of the cells against a metal is connected with a higher HSP synthesis. From comparison of cell growth and HSP accumulation in the presence of metal ions it was further concluded that HSP synthesis is a part of HM stress response of tolerant and non tolerant cells as under heat shock, but HSPs are not responsible for the heritable metal tolerance of Silene.In contrast to heat shock, metal stress does not inhibit the cell protein synthesis directly. In cultured tomato and Silene cells the inhibition of protein synthesis under metal stress was found to be a consequence of the inhibition of amino acid uptake. Zn has no effect on amino acid uptake of Silene cells. It is concluded that only Zn tolerance of Silene seems to be related with membrane stability.
Publikation
Hause, B.; Vörös, K.; Kogel, K.-H.; Besser, K.; Wasternack, C.;A Jasmonate-responsive Lipoxygenase of Barley Leaves is Induced by Plant Activators but not by PathogensJ. Plant Physiol.154459-462(1999)DOI: 10.1016/S0176-1617(99)80283-1
Using the recently isolated eDNA clone LOX2 : Hv : 1 which codes for the most abundant jasmonateinducible lipoxygenase (LOX) in barley leaves (Vörös et al., 1998), we analysed the capability of different activators of systemic activated resistance (SAR) to induce the expression of that LOX. Upon treatment of barley leaves with salicylate, 2,6-dichloroisonicotinic acid and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester, all these compounds were able to induce the expression of the LOX2 : Hv : 1 gene, whereas upon infection with the powdery mildew fungus (Blumeria graminis f. sp. hordei) mRNA accumulation was not detectable in compatible or in incompatible interactions. The induction of the LOX2 : Hv : 1 protein by SAR activators and the expression of different sets of genes induced by jasmonate and salicylate, respectively, are discussed in relation to defense responses against pathogenic fungi.
Publikation
Clemens, S.; Kim, E. J.; Neumann, D.; Schroeder, J. I.;Tolerance to toxic metals by a gene family of phytochelatin synthases from plants and yeastEMBO J.183325-3333(1999)DOI: 10.1093/emboj/18.12.3325
Phytochelatins play major roles in metal detoxification in plants and fungi. However, genes encoding phytochelatin synthases have not yet been identified. By screening for plant genes mediating metal tolerance we identified a wheat cDNA, TaPCS1 , whose expression in Saccharomyces cerevisiae results in a dramatic increase in cadmium tolerance. TaPCS1 encodes a protein of ∼55 kDa with no similarity to proteins of known function. We identified homologs of this new gene family from Arabidopsis thaliana , Schizosaccharomyces pombe , and interestingly also Caenorhabditis elegans . The Arabidopsis and S.pombe genes were also demonstrated to confer substantial increases in metal tolerance in yeast. PCS‐expressing cells accumulate more Cd2+ than controls. PCS expression mediates Cd2+ tolerance even in yeast mutants that are either deficient in vacuolar acidification or impaired in vacuolar biogenesis. PCS‐induced metal resistance is lost upon exposure to an inhibitor of glutathione biosynthesis, a process necessary for phytochelatin formation. Schizosaccharomyces pombe cells disrupted in the PCS gene exhibit hypersensitivity to Cd2+ and Cu2+ and are unable to synthesize phytochelatins upon Cd2+ exposure as determined by HPLC analysis. Saccharomyces cerevisiae cells expressing PCS produce phytochelatins. Moreover, the recombinant purified S.pombe PCS protein displays phytochelatin synthase activity. These data demonstrate that PCS genes encode phytochelatin synthases and mediate metal detoxification in eukaryotes.
Publikation
Bringezu, K.; Lichtenberger, O.; Leopold, I.; Neumann, D.;Heavy Metal Tolerance of Silene vulgarisJ. Plant Physiol.154536-546(1999)DOI: 10.1016/S0176-1617(99)80295-8
Silene vulgaris ssp. humilis, a heavy metal tolerant plant growing on the polluted soil of a medieval copper mining dump, accumulates considerable amounts of heavy metals (HM) in its roots and shoots. The intracellular distribution of HMs in the leaves was investigated by conventional and analytical (EDX, ESI, EELS) electron microscopy. Part of the HMs, Fe, Cu, and Zn occur as crystalline compounds on the surface of the leaves. The epidermal cell walls accumulate Fe, Ni, Cu, AI, Sn, and Zn. Cu within the cell walls is tightly bound to a protein with oxalate oxidase activity, evidencing a high homology to germin. Zn and Sn are accumulated in the cell walls as silicate. Cytoplasm and organelles contain only traces of Cu and Sn, while in the vacuoles no HMs are detected. In the epidermal cell walls, intercellular spaces, and in vacuoles there are high concentrations of Si, forming crystal-like structures. EELS and quantum-chemical calculations reveal these structures as SiO2. The role of Si in the HM-tolerance of Silene is discussed.