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Publications - Stress and Develop Biology

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Publications

Mittasch, J.; Böttcher, C.; Frolov, A.; Strack, D.; Milkowski, C.; Reprogramming the Phenylpropanoid Metabolism in Seeds of Oilseed Rape by Suppressing the Orthologs of REDUCED EPIDERMAL FLUORESCENCE1 J. Plant Physiol. 161, 1656-1669, (2013) DOI: 10.1104/pp.113.215491

As a result of the phenylpropanoid pathway, many Brassicaceae produce considerable amounts of soluble hydroxycinnamate conjugates, mainly sinapate esters. From oilseed rape (Brassica napus), we cloned two orthologs of the Arabidopsis (Arabidopsis thaliana) gene REDUCED EPIDERMAL FLUORESCENCE1 (REF1) encoding a coniferaldehyde/sinapaldehyde dehydrogenase. The enzyme is involved in the formation of ferulate and sinapate from the corresponding aldehydes, thereby linking lignin and hydroxycinnamate biosynthesis as a potential branch-point enzyme. We used RNA interference to silence REF1 genes in seeds of oilseed rape. Nontargeted metabolite profiling showed that BnREF1-suppressing seeds produced a novel chemotype characterized by reduced levels of sinapate esters, the appearance of conjugated monolignols, dilignols, and trilignols, altered accumulation patterns of kaempferol glycosides, and changes in minor conjugates of caffeate, ferulate, and 5-hydroxyferulate. BnREF1 suppression affected the level of minor sinapate conjugates more severely than that of the major component sinapine. Mapping of the changed metabolites onto the phenylpropanoid metabolic network revealed partial redirection of metabolic sequences as a major impact of BnREF1 suppression.
Publications

Horbach, R.; Navarro-Quesada, A. R.; Knogge, W.; Deising, H. B.; When and how to kill a plant cell: Infection strategies of plant pathogenic fungi J. Plant Physiol. 168, 51-62, (2011) DOI: 10.1016/j.jplph.2010.06.014

Fungi cause severe diseases on a broad range of crop and ornamental plants, leading to significant economical losses. Plant pathogenic fungi exhibit a huge variability in their mode of infection, differentiation and function of infection structures and nutritional strategy. In this review, advances in understanding mechanisms of biotrophy, necrotrophy and hemibiotrophic lifestyles are described. Special emphasis is given to the biotrophy-necrotrophy switch of hemibiotrophic pathogens, and to biosynthesis, chemical diversity and mode of action of various fungal toxins produced during the infection process.
Publications

Baum, T.; Navarro-Quezada, A.; Knogge, W.; Douchkov, D.; Schweizer, P.; Seiffert, U.; HyphArea—Automated analysis of spatiotemporal fungal patterns J. Plant Physiol. 168, 72-78, (2011) DOI: 10.1016/j.jplph.2010.08.004

In phytopathology quantitative measurements are rarely used to assess crop plant disease symptoms. Instead, a qualitative valuation by eye is often the method of choice. In order to close the gap between subjective human inspection and objective quantitative results, the development of an automated analysis system that is capable of recognizing and characterizing the growth patterns of fungal hyphae in micrograph images was developed. This system should enable the efficient screening of different host–pathogen combinations (e.g., barley—Blumeria graminis, barley—Rhynchosporium secalis) using different microscopy technologies (e.g., bright field, fluorescence). An image segmentation algorithm was developed for gray-scale image data that achieved good results with several microscope imaging protocols. Furthermore, adaptability towards different host–pathogen systems was obtained by using a classification that is based on a genetic algorithm. The developed software system was named HyphArea, since the quantification of the area covered by a hyphal colony is the basic task and prerequisite for all further morphological and statistical analyses in this context. By means of a typical use case the utilization and basic properties of HyphArea could be demonstrated. It was possible to detect statistically significant differences between the growth of an R. secalis wild-type strain and a virulence mutant.
Publications

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.
Publications

Bringezu, K.; Lichtenberger, O.; Leopold, I.; Neumann, D.; Heavy Metal Tolerance of Silene vulgaris J. Plant Physiol. 154, 536-546, (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.
Publications

Wollgiehn, R.; Neumann, D.; Metal Stress Response and Tolerance of Cultured Cells from Silene vulgaris and Lycopersicon peruvianum: Role of Heat Stress Proteins J. Plant Physiol. 154, 547-553, (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.
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