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Publications - Stress and Develop Biology

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Displaying results 1 to 10 of 14.

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.
Books and chapters

Clemens, S.; Simm, C.; Maier, T.; Heavy Metal‐binding Proteins and Peptides (2005) DOI: 10.1002/3527600035.bpol8010

IntroductionHistorical OutlineChemical StructuresNomenclature and Structure of MetallothioneinsPhytochelatins and Phytochelatin–Metal ComplexesStructural Properties of MetallochaperonesChemical Analysis and DetectionMetallothioneinsPhytochelatinsOccurrenceMetallothioneinsPhytochelatinsMetallochaperonesFunctionsMetal Homeostasis and the Role of MetallochaperonesBuffering and DetoxificationPhytochelatin FunctionsMetallothionein FunctionsPhysiologyMetallothionein Localization and IsoformsLocalization and Compartmentation of Phytochelatin SynthesisBiochemistryMetal‐binding Characteristics of MetallothioneinsBiochemistry of Phytochelatin SynthesisMolecular GeneticsMetallothionein Genes and Their RegulationPhytochelatin Synthase GenesBiotechnological ApplicationsPatentsOutlook and Perspectives
Books and chapters

Scheel, D.; Nuernberger, T.; Signal Transduction in Plant Defense Responses to Fungal Infection 1-30, (2004)

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Books and chapters

Rosahl, S.; Feussner, I.; Oxylipins 329-354, (2004)

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Books and chapters

Lee, J.; Nürnberger, T.; Is Pore Formation Activity of HrpZ Required for Defence Activation in Plant Cells? 165-173, (2003) DOI: 10.1007/978-94-017-0133-4_18

The HrpZ gene product, harpin, is an export substrate of the type III secretion system of phytopathogenic Pseudomonas syringae. The role of this protein in pathogenesis is largely unknown. We previously determined that HrpZ binds to lipids and can form cation pores in synthetic lipid bilayers. Such pore-forming activity may allow nutrient release during bacterial colonisation of host plants. In addition. HrpZ is known to trigger plant defence responses in a variety of plants, such as tobacco. We have previously also characterised a binding site in tobacco plasma membranes that likely mediates HrpZ-induced defence responses. In order to reconcile these findings, we pose the question as to whether the activation of plant defence responses by HrpZ is mediated through a “classical” receptor perception mode or if plant membrane perturbation through the inherent pore-forming activity of HrpZ may induce defence responses. As defence in parsley cells can be induced both in a receptor-mediated manner or through ionophores these cells served as an ideal system for our analysis. We first performed ligand binding studies to characterise the presence of a binding site/receptor. We further digested HrpZ with endopeptidases and used subfragments of HrpZ to assess the elicitor-active domain of HrpZ. A C-terminal region of HrpZ appears to be sufficient to elicit plant defence responses. A novel assay involving dye-loaded liposomes was developed to validate previous electrophysiological findings on HrpZ-mediated cation pore formation. More importantly, this assay was used to establish if the elicitor-active C-terminal fragment of HrpZ could form pores. Our findings suggest that the structural requirements for ion pore formation and activation of plant defence responses by HrpZ are different. Thus, ion pore formation alone may not explain the activation of plant defence by HrpZ.
Books and chapters

Scheel, D.; Oxidative burst and the role of reactive oxygen species in plant-pathogen interactions (Inzé, D. & van Montagu, M., eds.). 137-153, (2002)

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Books and chapters

Clemens, S.; Thomine, S.; Schroeder, J. I.; Molecular mechanisms that control plant tolerance to heavy metals and possible roles towards manipulating metal accumulation 665-691, (2002)

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