Research Group: Plant Metabolic Plasticity
Plants have a unique ability to adapt to changes in their environment. An important factor in this plasticity is the production of a multitude of complex and species-specific metabolites, allowing plants to defend themselves against herbivores and pathogens, attract pollinators or symbionts, mitigate abiotic stresses and coordinate internal processes by signaling. We study how plants fine-tune their allocation of resources between molecules of different functions according to their physiological state or in response to environmental challenges, with a key interest in the plant glutathione transferase (GST) enzyme family in cereals, mainly sorghum and oat.
This enzyme family is also known to be involved in detoxification reactions and plant resilience against abiotic as well as biotic stress. However, the plant GSTs are poorly understood and very few functions are described. Our group combines biochemistry, enzymology, molecular biology and state-of-the-art metabolomics approaches to solve the mysteries of plant specialized metabolism and glutathione transferase functions in cereals.
In the facility PlantMSI, headed by Nanna Bjarnholt, we pioneer advances in the novel spatial metabolomics technology mass spectrometry imaging for plant science. In collaboration with plant scientists across the globe, we develop specialized workflows for a broad range of plant species and tissues to visualize localized metabolic changes in growth and development, stress responses, infection processes etc. If you want to know how we may help your research project, get in touch at PlantMSI@plen.ku.dk
Plant Glutathione Transferases (GSTs)
Plant glutathione transferases (GSTs) constitute a large plant enzyme family involved in numerous functions, such as defense, stress response and specialized metabolism. Despite GSTs being abundantly present in the entire plant kingdom, most of the enzyme functions remain unelucidated. In our group, we investigate GST functions in cereal crops such as sorghum and oat, with a focus on disease resistance, stress resilience and metabolic partitioning. We apply multiple methods in our search such as bioinformatics, transcriptomics, metabolomics, gene knock-out, heterologous expression, and enzyme assays.
Fungal Disease Resistance in Cereals
We are interested in discovering enzymes that contribute to Fusarium resistance in cereal crops, e.g. oat (Avena sativa). Fusarium infection causes immense yield losses in agriculture each year due to accumulation of mycotoxins, mainly the trichothecene deoxynivalenol (DON). However, well characterized routes for in planta DON detoxification lead to production of so-called masked mycotoxins, that can be re-activated in the human and animal intestines upon ingestion of contaminated grain. It is therefore attractive to identify genes that lead to irreversible detoxification. Recent advances have identified new enzymes that can confer such detoxification, and our research points to oat as a potential source of genes that encode particularly efficient DON detoxifying enzymes as well as additional novel routes for degradation of the harmful DON.
Mass Spectrometry Imaging for Plant Science
Mass spectrometry imaging (MSI) is an analytical technique that enables mapping of the localization of metabolites in different plant tissues. Combined with other methods such as transcriptomics, laser-capture microdissection, liquid chromatography-mass spectrometry etc., MSI is a strong tool for understanding and elucidating pathways in plant metabolism, the biological functions of small molecules, and plant-microbe interactions. We host the first and currently only strictly plant-focused MSI platform in the world (est. 2023), equipped with a state-of-the-art MSI instrument, the timsTOF-fleX-MALDI-2 from Bruker (with microgrid, i.e. 5 µm resolution) and matrix sprayer and sublimator from HTX. With MSI still lacking development for plant science, we focus on development and optimization of new methods for sample preparation and analysis through our own and collaborative projects, working across plant science and with in-house as well as international collaborations. If you are interested in collaborating with us, get in touch at PlantMSI@plen.ku.dk
Sorghum
This tropical cereal is known for its high drought tolerance and nitrogen use efficiency, and celebrated for its potential as a crop of the future in a hotter, drier world, including Europe. We investigate the involvement of GSTs in drought response and nutrient use and homeostasis, and use it as a model system for a range of metabolic systems we investigate in other cereals.
Herbicide Safener
Induction of plant natural defenses are currently used in integrated weed management, such as use of herbicide safeners which prepare crops for herbicide application. Application of these agrochemicals work by upregulating expression of detoxifying enzymes, e.g. GST-encoding genes in crops, but not in weeds. As an understudied area of plant science, elucidating the underlying molecular mechanisms will allow for future development of means to prime and increase plant natural defenses, and further the understanding of the roles plant GSTs play in such mechanisms.
Oat
Avena sativa is an increasingly important cereal crop in Northern America and Europe, appreciated for its hardiness, nutritional profile and usage as an important ingredient in several dairy substitute products. In our group, we investigate how GSTs are involved in stress responses, such as drought or fungal infections.
For students wishing to work within these topics, Projects in Practice, M.Sc. and B.Sc. projects are currently available. Please contact the group leader Nanna Bjarnholt at nnb@plen.ku.dk
- LAMBDA glutathione transferases (GSTs), mystery enzymes in plant drought response (DFF research project 1, 2026-2028)
- CerealGSTs - Glutathione transferases for fungal disease resistance and increased food safety of cereal crops (NNF – Ascending Investigator project, 2022-2027)
- PlantMSI – Visualizing the metabolic life of plants and in plant-microbe interactions by Mass Spectrometry Imaging (NNF– Infrastructure grant 2023-2029)
Glutathione transferases (GSTs) - Mysterious enzymes in plant resilience against abiotic and biotic stress factors
Global food security is increasingly challenged by adverse growing conditions resulting from climate change. Understanding mechanisms in stress resilience of major crops is therefore of great importance to mitigate the increasing stress.
Plant glutathione transferases (GSTs) constitute a large and diverse enzyme family, found in high numbers across the entire plant kingdom. Gene expression of GSTs are commonly upregulated in response to various biotic and abiotic stresses, such as salt, drought, agrochemicals and pathogen infections. Several examples in literature show that overexpression of crop GSTs in model plants confer stress tolerance and that GSTs mitigate the effects of both abiotic and biotic stresses in plants. The archetypical role of GSTs is in detoxification of xenobiotics, where GSTs function by catalyzing conjugation of the tripeptide glutathione, onto small molecules, reducing the toxicity and increasing the solubility of toxic compounds. However, the large number of GSTs in plants implies that GSTs may also partake in other types of reactions in addition to detoxification. There are indeed examples of GSTs being involved in transport of anthocyanins, as well as nitrogen-recovery and antioxidant recycling. The roles of the large majority of plant GSTs remain unelucidated however, and our group investigates several different potential functions across cereal crops and different metabolic pathways and stress response systems.
The project could involve a number of different exciting experimental procedures using state-of-the-art approaches at the forefront of plant biochemistry research, such as:
- Heterologous expression of plant GSTs in for instance coli or N. benthamiana (tobacco)
- Cloning of native plant GSTs from multiploidal crops, which is complex due to high similarity between genes
- Metabolomics
- Mass Spectrometry Imaging of plants, e.g. infected wiht pathogens or under abiotic stress
- Interactions of key global crops with agrochemicals and pathogens
- Phenotyping of gst knock-out lines in Sorghum bicolor and Arabidopsis thaliana in response to biotic and abiotic stresses
Plant Mass Spectrometry Imaging for plant science
The workflow for mass spectrometry imaging is complex and involves sample embedding, freezing, cryo-sectioning and freeze drying, followed by application of matrix for Matrix Assisted Laser Desorption Ionization-MSI analyses, the imaging analysis itself and finally data analysis. We optimize all steps and use the technology in our own research projects too. Student projects can be either biological with focus on using the technology on plant samples, more technical with e.g. focus on optimized workflows for matrix application or development of quantification procedures, or focused on developing workflows for data analysis, e.g. compound identification.
We are situated in PLEN on the Frederiksberg campus at Thorvaldsensvej 40.
For more information contact Nanna Bjarnholt at nnb@plen.ku.dk
- Associate Professor Christian Janfelt, The Health Faculty, University of Copenhagen, Denmark
- Professor Robert Edwards, Newcastle University, UK
- Professor Ian Godwin, University of Queensland, Australia
- Professor Anders Meibom, University of Lausanne, Switzerland
- Assistant Professor Tiffany Porta/Post doc Lucia Montini. M4I, Maastricht University, Netherlands
- Senior Scientist Ilka Braumann. Carlsberg Research Laboratory, Denmark
Group members
| Navn | Titel | Telefon | |
|---|---|---|---|
| Asta Holmelund Rønager | Videnskabelig assistent | +4535333903 | |
| Nanna Bjarnholt | Lektor - forfremmelsesprogrammet | +4535331136 | |
| Nanna Weise Havshøi | Postdoc | +4535325140 | |
| Nikola Micic | Specialkonsulent | +4535332348 |
