1. Biotic Interactions
Cancer on e.g. apple trees and beeches
- Neonectria ditissima
The biological interaction between organisms within an ecosystem is determined by various factors. We study such processes using the example of the plant disease of fruit tree cancer caused by the pathogen Neonectria ditissima. More precisely, we identify secondary metabolites that contribute to pathogenity-associated, mutualistic, or antagonistic chemical communication within the host plant. First, we isolate endophytic organisms from healthy plant material of the host plant and test their antagonistic activity against the vegetative growth of N. ditissima. In this context, we identify phytotoxic substances of the phytopathogenic within an apple test system. Based on genome sequence data of N. ditissima and the establishment of genetic manipulation, we are able to investigate the biosynthetic pathways involved.
Grapevine pathogenic fungi
- Esca
Esca, Eutypa Dieback and Botryosphaeria Dieback are three economically relevant diseases of vine plants in which one or more xylem fungi are involved. Phaeomoniella chlamydospora, Phaeoacremonium minimum, Eutypa lata, Fomitiporia mediterranea and several members of the Botryosphaeriaceae belong to the most important species associated with these diseases worldwide. We study the interactions between pathogenic fungi and their host plant. Furthermore, we aim to identify antagonistic fungi as putative biological control agents (e.g. fungicides) to contribute to integrated pest management solutions (http://www.ibwf.de/index.php/fields-of-competence/plant-protection-research-development/pathogens-in-grapevine ).
- Guignardia (black rot)
Guignardia bidwellii is the phytophatogenic cause of black rot on vines, which is a massive threat to organic viticulture. In the 19th century, black rot was introduced into Europe from North America and has spread to Germany since 2002, favoured by climate change. The understanding of the molecular mechanisms of host-pathogen interaction is currently limited, and molecular gene manipulations in G. bidwellii have not yet successfully been established. We identified the phytotoxic dioxolanones phenguignardic acid and guignardic acid as potential virulence factors and we elucidate the biosynthesis of phenguignardic acid.
- Roesleria
Roesleria subterranea is a phytopathogenic fungus causing significant harvest losses in viticulture due to root rot. To date, our knowledge concerning the molecular basis of host-pathogen interaction is limited. Therefore, our group is mainly investigating the secondary metabolism of the vine pathogenic fungus in order to gain insight into the infection process. The genome of R. subterranea has already been sequenced and annotated. The establishment of a suitable transformation system for this fungus is currently under progress in order to elucidate the secondary metabolite biosynthetic pathways and in particular to identify putative pathogenicity factors.
Grapevine-associated yeasts
Non-Saccharomyces yeasts are gaining increasing importance in the production of wines with a special sensory note. In this context, we investigate yeasts such as Metschnikowia or Wickerhamomyces for the formation of enzymes of oenological interest. In addition to must fermentation, however, such "wild yeasts" also play an important ecological role. They colonize plant surfaces (leaves, fruits) and thus form a natural barrier against pathogenic fungi such as Botrytis cinerea. We are therefore evaluating the suitability of non-Saccharomyces yeasts as biological components within the framework of integrated plant protection. Our research focuses on the clarification of the antagonistic principles of action (enzymes, killer toxins, secondary metabolites).
Cereal pathogenic fungi
- Magnaporthe oryzae (Rice blast disease)
Magnaporthe oryzae (Rice Blast Disease) is one of the most important plant pathogens in agriculture worldwide. The fungus is a model organism in our laboratory for investigations concerning the molecular basis pathogen/host interactions. We are interested in the pathogenicity relevant differentiation and the underlying physiological processes as well as a strain collection of over 350 genetically manipulated M. oryzae strains (http://www.ibwf.de/index.php/fields-of-competence/plant-protection-research-development/molecular-basis-of-plant-microbe-interaction ).
- Zymoseptoria tritici (Septoria Leaf Blotch)
Another model organism in our group is Zymoseptoria tritici (teleomorph Mycosphaerella graminicola), one of the most important harmful fungi in cereal cultivation. This pathogen causes leaf drought, which results in massive crop failures every year. We use a combination of transcriptome-based (RNA-Seq), genomic (NGS), molecular biological (reverse and forward gentetics), cell biological and bioinformatic methods (clustering, coexpression and coregulation analysis) to understand the molecular mechanisms of dimorphic transition from yeast-like growth to mycelial growth in Z. tritici.
2. Networks and Communication
A major challenge in cell biology is to understand how cells process and integrate information from their environment to adapt their physiology. It is particularly important that metabolism, growth and cell division are coordinated. Using the High Osmolarity Glycerol (HOG) signalling pathway in the model organism Magnaporthe oryzae, we are investigating how a cell can perceive signals from its environment, process them and consequently adapt its metabolism and growth (http://www.ibwf.de/index.php/fields-of-competence/plant-protection-research-development/molecular-basis-of-plant-microbe-interaction ).
3. Gene Regulation & evolution
Rapid evolution of signalling networks
A fundamental question in biology is how signalling networks have developed over the course of evolution. We discovered that M. oryzae mutants with inactivated osmoregulation lead to growth under constant osmotic stress within only a few weeks, resulting in "adapted" individuals with the ability to react to osmotic stress independent of the original signalling system, respectively by a re-wired signalling system. We investigate the basis of this phenomenon in the DFG-funded project "Rapid evolution of signalling networks in the pathogenic fungus Magnaporthe oryzae" (DFG priority programme 1819: https://dfg-spp1819.uni-hohenheim.de/131115 ).
4. Biology of aging and differentiation
Alternative splicing
From one DNA sequence and accordingly one and the same pre-mRNA, several different mature mRNA molecules are formed by alternative splicing and several different proteins are also formed by their translation. Misregulations are a frequent cause of different (also age-related) disease patterns. We investigate molecular mechanisms of alternative splicing using the example of the phosphotransfer protein MoYpd1p in the phosphorus relay system of the HOG signaling pathway of M. oryzae in order to improve our knowledge of such processes. (DFG project https://gepris.dfg.de/gepris/projekt/426554840 )
Genomic instability
We investigate the genome variability and chromosome stability of Zymoseptoria tritici. The wheat pathogen possesses a set of non-essential chromosomes, the number of which is variable among the different field isolates. These chromosomes are unstable during meiosis, transcriptionally inactive and have an accumulation of repetitive elements and heterochromatin-associated histone modifications. Their functional role and why these chromosomes were obtained in the course of evolution is not yet known. We use comparative and population genomic approaches based on computer-based comparative genomics methods and reverse genetics techniques to generate chromosome-deficient mutant strains.
5. Secondary Metabolism and Synthetic Biology
Biosynthesis and Regulation
The identification of secondary metabolites which are able to affect biological processes, e.g. respiration or fungal spore germination is a further focus of our research. Natural products with bioactivity often become candidates for agricultural or pharmaceutical applications (e.g. penicillin, strobilurin) but also serve as probes for basic research (e.g. physiological studies). To investigate and isolate bioactive secondary metabolites, we use diverse assay systems to address target organisms or molecular targets. (http://www.ibwf.de/index.php/fields-of-competence/natural-product-research)
We investigate the molecular regulation mechanisms for the biosynthesis of secondary metabolites e.g. the phytotoxic secondary metabolite pyriculol, which plays a role in the pathogen/host interaction of the phytopathogenic fungus Magnaporthe oryzae and its host plant rice. (http://www.ibwf.de/index.php/fields-of-competence/genetics-of-biosynthetic-pathways ).
We also identify secondary metabolites produced by Z. tritici that are important for pathogenic development. Biosynthetic (cluster) genes and their transcriptional and epigenetic regulatory mechanisms are investigated to gain knowledge about the molecular basis of plant/pathogen interactions. Furthermore, we investigate metabolic conversion processes of Z. tritici that contribute to the detoxification of induced plant defense agents.