Current projects include:
- Isolation of differentially expressed genes during development of the clubroot disease
- Signaling between plants and pathogens or endophytes
- Plant hormones and secondary plant metabolites during the development of pathogenic and symbiotic interactions
- Biosynthesis and metabolism of plant hormones and their role during plant development and evolution
- Secondary plant metabolites: improvement or reduction of production and generation of novel compounts
- Secondary plant metabolites and their bioactivity
Control of the clubroot disease by an endophytic fungus of the genus Acremonium
Untersuchungen zur Kontrolle der Kohlhernie durch einen endophytischen Pilz
The clubroot disease caused by Plasmodiophora brassicae infects economically important crop species such as canola and causes high yield losses. The disease is difficult to control by chemical and cultural means. In a previous study from our laboratory Acremonium alternatum, a soilborne endopyhtic fungus and known biological control agent in other countries, showed a promising antagonistic effect in clubroot infected plants. The means by which Acremonium controls pathogens is not known so far. Presumably the fungus induces resistance mechanisms in the host plant and thus delays the development of the pathogen. We want to test this theory in the model plant Arabidopsis thaliana as well as the economically important crop species canola (Brassica napus) and Chinese cabbage (B. rapa). To monitor the development of the infection within plants we will use molecular methods as well as phytopathological techniques. The following questions will be addressed: (A) How does Acremonium induce tolerance / resistance in Arabidopsis? (B) In which plant parts can the endophyte be found at different time points after inoculation? (C) Where does the interaction between Acremonium and P. brassicae take place? (D) Which plant signals are involved? The long-term goal is to develop an inocolum from Acremonium spores or spore parts which can be applied easily and constitutes an environmentally friendly and lasting method for the reduction of clubroot infections.
Role of auxin in tomato flower organs and fruit during development under high temperature conditions (Doctoral thesis)
Die Rolle von Auxinen in Tomatenblüten und Früchten während der Entwicklung unter hohen Temperaturen (AUXTOM)
Tomatoes are major horticultural crops. Their yield is maximized in moderate climates, whereas exposure to high temperatures often limits tomato flower development, fruit set and thus productivity. Recent findings in the model plant Arabidopsis have shown that the plant hormone auxin plays a role in such processes. The project deals with auxin biology in tomato fruit development and productivity. In collaboration with Hagai Yasuar (Volcani Center) and Asaph Aharoni (Weizmann Institute) in Israel the physiology of stressed tomatoes will be studied.
The project is funded by:
Enhancing production of the antitumor compound astin by a novel fungal endophyte of Aster tataricus (ASTINPROD)
Erhöhte Produktion der Antitumorverbindung Astin durch einen neuen endophytischen Pilz aus Aster tataricus
Extracts of dried roots of the plant Aster tataricus are successfully used in traditional Chinese medicine as cough remedy. Astins, secondary metabolites isolated from these root extracts, show promising antitumor activities. Astins are cyclic pentapeptides and ca 20 different astins have been now isolated from aster roots. For antitumor activity, cyclization and a rarely observed dichlorinated proline residue are necessary. In a collaborative project with partners from Germany (Karl-Heinz van Pee), The Netherlands (Willem van Berkel) and Belgium (Philippe Jacques, Luc Willems, Diagenode, Lipofabrik) we want to produce astins at large scales and test the possible bioactivities.
Characterization of genes / proteins from the obligate biotrophic plant pathogenic protist Plasmodiophora brassicae, causal agent of the clubroot disease
Untersuchung von Genen / Proteinen aus dem obligat biotrophen Pflanzenpathogen Plasmodiophora brassicae, dem Erreger der Pflanzenkrankheit Kohlhernie
The obligate biotrophic plant pathogen Plasmodiophora brassicae causes the clubroot disease within the family of Brassicaceae that include many commercially important agricultural crops like cabbage, radish and oilseed rape. Plant hormones are important signals during the infection and colonization of plants by P. brassicae. Auxins and cytokinins act in the regulation of cell elongation and cell division to create the space in the host tissue that is needed for the propagation of the pathogen. Moreover cytokinins are involved in the generation of a metabolic sink to ensure the nutrition of the pathogen. Salicylic acid ant its methyl ester play a very different role and act in plant defense. The finely tuned regulation of these hormone levels seems to be the key for the efficient colonization of the host plant. Until now only a few proteins from P. brassicae are functionally characterized. Based on yet unpublished sequence date we have chosen some P. brassicae genes possibly involved in hormone metabolism for further characterization.
Sabine Jülke / Kenny Rabe
Novel production system for secondary plant metabolites on the basis of cell free catalysis in a compartmented bioreactor
Neues Produktionssystem für pflanzliche Sekundärmetabolite auf Basis zellfreier Biokatalyse in einem kaskadierten, kompartimentierten Hairy-Root-Reaktor
The production of secndary plant metabolites in vitro is challenging. Hairy root cultures can solve some problems since they are a good background for the expression of plant genes. However, they need adapted closed reactor systems due to their root structure and so far the yields are very low. The strategy in this project uses Hairy roots as producert of key enzymes for a stepwise extracellular biocatalysis of secondary metabolites. The process is implemented in a modular bioreactor, in which the modules can be separated by membranes from each other. In every module another transgenic root line would be able to secreted the key enzyme for one partial reaction. The project is carried out together with the Department of Bioenineering at the TU Dresden.
The role of the plant hormone auxin during abiotic stress responses of plants (Doctoral thesis)
Die Rolle des Pflanzenhormons Auxin in abiotischen Stressantworten von Pflanzen
The moss Physcomitrella patens is an important species which is used as model organism to investigate different types of stress and their influence on cellular processes and molecular pathways. The gametophytic tissue of this plant consists of one native auxin indole-3-acetic acid (IAA). In order to investigate the effects caused by the salt as abiotic factor mutant lines in auxin conjugating proteins and auxin responsive promoter GUS lines will be investigated.
Bioactive secondary metabolites from comfrey (Symphytum officinale) (Doctoral thesis)
Bioaktive Pflanzen-Inhaltsstoffe aus dem Beinwell (Symphytum officinale)
Comfrey (Symphytum officinale) is a long known medical plant with analgetic and antiinflammatory effects that enhances tissue regeneration. Allantoin and rosmarinic acid are regarded as main active compounds. They are accompanied by other phenole carboxylic acids, tanning agents, triterpenes and polysaccharides working as adjuvants. Beside these useful substances, toxic pyrrolizidine alkaloids are found in comfrey. After ingestion, they are metabolised and form toxic derivatives which can harm human liver, capillaries and lung. Mutagenous and probably carcinogenous effects have also been shown. This limits the use of comfrey to the application on intact skin. Hairy roots, induced by Agrobacterium rhizogenes, can be used as tissue culture system for the production of plant metabolites. They do not need light or phytohormones for growth and often produce more complex metabolite patterns than callus cultures. This project aims at generating Hairy roots of Symphytum officinale with downregulated alkaloid biosynthesis to exclude the toxic components from the otherwise beneficial metabolite pattern.
see also: Weisse Biotechnologie mit Pflanzenzellen
Analysis of expansin expression in relation to auxin homeostasis during the clubroot disease (Doctoral thesis)
Analyse der Expansin-Expression und der Auxin-Homöostase während der Kohlhernie
Description: Expansins are proteins that induce cell enlargement by loosening the matrix of the cell wall. They are regulated by symbionts and various pathogens as well as by auxin and mediate the ‘acid-growth’. Expansins are common in all land plants – from moss to flowering plants. In Arabidopsis there are 36 members of the expansin gene family (AtExp), in rice there are even 58. In this study we analysed whether expansins are specifically regulated during clubroot disease of Arabidopsis thaliana. Clubroot is caused by the protist Plasmodiophora brassicae and only affects Brassicaceae. Symptoms are galls on the roots and wilted and stunted shoots. In semiquantitative RT-PCR expression analysis it was shown that most expansins are strongly up- or downregulated in infected plants compared to healthy controls. In expansin promoter::GUS lines a direct connection of expansin-expression and infection structures is clearly to be seen. Homozygous T-DNA mutants of various expansins were studied in infection test. First results show some candidates with much more tolerance towards P. brassicae than wild type plants. These studies potentially contribute to the development of highly tolerant or even resistant plants.
Generation and characterization of halogenated compounds in hairy roots of Brassica by transformation with bacterial halogenases (Doctoral thesis)
Herstellung und Charakterisierung halogenierter Substanzen in transgenen Organkulturen von Brassica durch Transformation mit bakteriellen Halogenasen
The introduction of a halogen into a natural product has frequently been demonstrated to improve bioactivity and bioavailability. Furthermore, the incorporation of chlorine or bromine into a natural product provides a reactive handle that may be utilised for further site-specific functionalisation. Using flavin-dependent halogenases regioselective incorporation of halogen atoms can be achieved. Flavin-dependent halogenases are two-component systems consisting of a flavin reductase producing FADH2 and the halogenase. The huge advantage of these halogenases over chemical halogenation is that they have 100% regioselectivity and thus produce no unwanted by-products. Tryptophan halogenases are especially suited for this purpose since they use free tryptophan as the substrate. Already available tryptophan halogenases and variants from the project will be used to transform plants producing tryptophan-containing secondary metabolites or indole derivatives to obtain new halogenated compounds produced in vivo. We have chosen a plant species with a highly diverse range of indole derived metabolites to analyze furthermore their bioactive potential. A collaborative project with Karl-Heinz van Pee (TU Dresden), Sarah O'Connor (John Innes Centre), Rebecca Goss (University of St. Andrews), Alfredo Aires (Universidade de Tras-os-Montes e Alto Douro), Vita34 AG (Bioplanta Leipzig).
Bioactive metabolites from modified cell and tissue cultures of sunflower (Helianthus annuus) (Doctoral thesis)
Bioaktive Pflanzeninhaltsstoffe aus modifizierten Zell- und Gewebekulturen der Sonnenblume (Helianthus annuus)
Alpha-tocopherol is a secondary metabolite produced in almost every plastid containing tissue of plants. It has anti-oxidative properties and is considered as essential vitamin in humans. Thus, it is used as an additive in food, cosmetics and pharmaceutical products. The aim of this work is to produce large amounts of all-R-α-tocopherol (fig. 1) by using genetically-engineered sunflower (Helianthus) in vitro cultures in bioreactors. Only biological systems can produce this enantiomer exclusively . Subsequent downstream processing of the plant cell culture (callus or hairy roots) will yield the metabolite.
see also: Weisse Biotechnologie mit Pflanzenzellen
Transformation of Arabidopsis thaliana with bacterial halogenases to produce novel halogenated indole metabolites (Doctoral thesis)
Transformation von Arabidopsis thaliana mit bakteriellen Halogenasen zur Erzeugung neuer halogenierter Metabolite
Over the last decades natural products became more important for many areas of medicine, pharmacology and agriculture. Many important antibiotics and anticancer agents are based on such secondary metabolites from different organisms. The introduction of a halogen (halogenation) into a structure can improve the bioactivity and bioavailability. The introduction of a halogen in the metabolism of medically important plants could lead to a variety of novel plant metabolic products with improved properties. A regioselective incorporation of a halogen atom (chloride or bromide) can be achieved by using flavin-dependet halogenases. In this project three well characterised flavin-dependent halogenases will be introduced and overexpressed in Arabidopsis thaliana as a model plant. The project aim is to analyse changes in the metabolic profile of possible modified biosynthetic compounds in these plants. Furthermore, the growth of these transgenic plants will be analyzed.
partially funded by:
Sächsisches Staatsministerium für Wissenschaft und Kunst