Dr. Tobias Köllner

One of the strategies of plants to defend themselves is by producing complex volatile blends. Volatiles can function as direct or indirect defenses e.g. repelling herbivores or attracting natural enemies of the herbivores. Furthermore, volatiles can protect the plants from pathogen attack. In our group we are investigating the biosynthesis and function of volatile compounds released after above- and below-ground herbivory in woody plants and grasses. We are using microarrays and large-scale cDNA sequencing to identify genes involved in these defense reactions. Candidate genes are heterologously expressed and characterized. The construction of knock-out plants and overexpressing plants and their use in biological assays will help us to elucidate the role of volatiles in plant-insect interactions. more>>>


Dr. Sybille Unsicker

The application of genetic, molecular, and analytical tools to study the chemical ecology of woody plants is still in its infancy. We chose Populus nigra L. as a model species due to the published genome of the closely related species P. trichocarpa and the large base of knowledge on poplar secondary metabolism and poplar-insect interactions. To study the chemical defenses of P. nigra under natural conditions, an old-growth population was chosen growing on a floodplain in northeastern Germany. Mature trees from this population contain a diverse array of potential defensive metabolites, including phenolic glycosides, condensed tannins, and other flavonoids. Volatile terpenoids and green leaf volatiles were also detected. This phytochemical complexity in combination with the genomic sequence makes poplar an ideal model organism to study the chemical bases of plant-herbivore interactions. We are especially interested in the herbivore-inducible metabolites of poplar and their role in direct and indirect tree defense. more >>>


Dr. Grit Kunert

Herbivores are known to have a huge impact on plants and plant communities. To protect themselves, plants have evolved a wide range of defenses including morphological structures like thorns, trichomes, mechanical reinforcements, and the accumulation of defensive compounds. These defense compounds are either produced constitutively or induced by herbivory and can affect the attacking herbivore directly or via multitrophic interactions. Plant defense is closely linked to other plant processes since resources are inherently limited and can only be allocated to growth, reproduction, storage or defense. Our group uses aphids, a widespread group of sucking herbivores, to investigate the influence of plant chemicals on aphid life history traits. We would like to know how plant chemistry might affect aphid performance as well as plant fitness. more >>>


Dr. Axel Schmidt

Since their divergence 300 million years ago, gymnosperms and angiosperms have evolved different strategies to cope with changing environmental conditions. As a result of their early divergence, gymnosperms have acquired unique traits that distinguish them from herbaceous and woody angiosperms. For example, defense mechanisms have been described in conifer trees such as Norway spruce (Picea abies) and Scotch pine (Pinus sylvestris) which can be constitutive or induced in response to biotic and abiotic stress and lead to the formation of physical barriers (i.e. formation of terpenoid-based oleoresin filled traumatic resin ducts), and/or the synthesis of phenolic compounds, volatile and nonvolatile terpenoid compounds. Several genes and proteins related to these responses have been identified and characterized. To investigate the ecological function in conifer defense and the mode of action of terpenes and phenolics, we are using transgenic spruce and phloem-feeding insects like bark beetles (Ips typographus) in association with the blue stain fungus (Ceratocytis polinca) or the large pine weevil (Hylobius abietis). more >>>


Dr. Almuth Hammerbacher

Plants synthesize many different toxic secondary metabolites as an immune response against fungal and bacterial pathogens. Although this defense strategy is often successful in avoiding plant disease, some pathogens have special adaptations enabling them to overcome the toxic effects of secondary metabolites. Tree species produce an impressive array of polyphenolics to defend themselves against pathogen attack. These complex aromatic compounds are thought to inhibit microorganism development in many different ways. However, despite increased biosynthesis of some of these toxic defense compounds in response to infection by pathogens, trees are often colonized by disease-causing organisms which seem well adapted to polyphenols. Our study system focuses on the adaptations of blue stain fungi (order Ophiostomatales) infecting woody hosts. We have already shown that some of these fungi have special metabolic pathways for the degradation of polyphenols produced by their hosts as defense compounds. more>>>


Dr. Daniel Giddings Vassao

Plants defend themselves against herbivory using many strategies, one of them being a large arsenal of chemicals. While we find many of these compounds harmless or even pleasantly spicy, most small herbivores tend to suffer noticeable negative effects on growth and development when they eat such well-defended plant tissues. Therefore, many herbivores employ more or less well-adapted biochemical mechanisms to avoid the toxicity of some of these plant compounds. The main aims of the research in our group are a) to investigate the adaptive biochemical strategies used by herbivores to disarm or cope with these toxins as a part of their diet, and b) to identify what effects these compounds have on the herbivores’ physiology and metabolism leading to their in vivo toxicities. more >>>