Judith Lundberg-Felten

In boreal and temperate forests, the majority of trees live in symbiosis with ectomycorrhizal soil fungi via their root system. This symbiosis is abundant and forms spontaneously. A root system may interact with many species of fungi at the same time, and a mycelium can connect several trees. During the formation of ectomycorrhizal symbiosis, fungal hyphae surround the root in a structure called "mantle" and make their way into the apoplastic space between root cells. This results in a labyrinthine network of hyphae in the root called the "Hartig Net". Plant and fungus express transporters in the Hartig Net that allow the transfer of phosphorous and nitrogen, absorbed from the forest soil by the fungus, to the plant. The plant provides photosynthetic carbohydrates to the fungus. The regulation of the exchange rate is a complex process, that is determined not at least by the availability of nutrients in the soil.

The establishment of the symbiosis requires a modulation of plant cell-to-cell adhesion, to accomodate fungal hyphae inside the root, and a decrease of plant defense responses during the invasion phase. I study cell wall remodelling and the associated defense responses using molecular methods. Symbiosis establishment does not only affect the plant locally in the root system. It also acts on distal plant organs, such as aboveground tissues. I study this effect with regards to how the symbiosis modulates overall plant resistance to biotic and abiotic stresses and aim to identify the molecular mechanisms behind these benefits of the symbiosis. 

• Courseleader in the forestry undergraduate program at SLU Umeå for the course Plant Biology for Future Forestry (2018-2021) and Treebiology, Genetics and Evolution (2021-2023)
• From 2020 to 2022 I have coordinated PhD courses at Umeå Plant Science Centre for the Department of Forest Genetics and Plant Physiology and organized a PhD course on sample preparation, sectioning and microscopy.
• January 2022 till May 2023 appointment as Assistant Head of Department responsible for undergraduate education at the Department of Forest Genetics and Plant Physiology, SLU Umeå.

In my research I aim to understand the factors determining ectomycorrhizal symbiosis establishment, such as cell wall remodelling during Hartig Net formation and defense response regulation. I also study modulation of plant resistance to biotic and abiotic stress through ectomycorrhizal symbiosis.

Cell wall remodelling during Hartig Net formation

We have identified that pectin remodelling is an important process for Hartig Net formation. Through gene-expression analysis and gene-modification in the ectomycorrhizal fungus Laccaria bicolor, we were able to identify L. bicolor Pectin-Methylesterase 1 (LbPME1). This enzyme is involved in pectin remodelling which leads to cell-to-cell loosening during Hartig Net establishment (Chowdhury et al. 2022, New Phytologist). 

Tannins and symbiosis establishment

Tannins are secondary metabolites mostly known as herbivore deterrents in plant leaves. We have developed a method for fluorescent localization of tannins (Chowdhury et al. 2022, Frontiers in Plant Science) that has allowed us to detect tannins even in root tissues, where their presence co-localizes with pectin in the middle-lamella. Studying tannin dynamics during ectomycorrhiza formation in different host-tree species has allowed us to identify that tannin levels change during ectomycorrhiza formation. We are now studying the molecular mechanisms and biological significance behind this phenomenon and how ectomycorrhizal symbiosis influence overall tannin dynamics in below- and aboveground tissues in trees.

Ectomycorrhizal symbiosis and drought resistance

Ectomycorrhizal symbiosis with soil fungi can protect roots physically from drought, can increase nitrogen use efficiency and convey drought resistance through systemic mechanisms in the plant. Today the exact nature of these mechanisms is not clearly understood and whether the effects are general or species specific needs further investigation. There is a great potential of using ectomycorrhizal symbiosis already in tree nurseries to make trees more resistant to drought after outplanting into the forest. We are aiming in the coming years to uncover ectomycorrhizal fungi local to Sweden that can bring such benefits to trees in nurseries.

Want to lern more? Watch my popular science lecture about how we study fungus-plant communication in ectomycorrhizal symbiosis (from 2017).

I have ongoing collaborations with Benedicte R. Albrectsen and Nathaniel Street at Umeå Plant Science Centre, Umeå University, Sandra Jämtgård at SLU Umeå, Claire Veneault-Fourrey and Aurélie Deveau at INRA Nancy, IAM Research unit (France), Minna Kemppainen at the National University of Quilmes (Argentina) as well as the C. Peter Constabel at the University of Victory (Canada).

I am associated to Umeå Plant Science Centre.

My background is in plant molecular biology where I have carried out research on ectomycorrhizal symbiosis and wood development mainly in hybrid aspen trees. In these areas, my focus has been on the molecular mechanisms, phytohormone signaling and cell wall remodelling. I have expertise in target gene identification through transcriptome analysis (RNASeq and RT-qPCR), molecular cloning and gene-modification in Arabidopsis, Populus and L. bicolor , phenotyping and chemotyping (Fourrier-transform infrared spectroscopy and Raman microscopy), sample preparation, sectioning, histology and a wide range of microscopy techniques (widefield, confocal laser scanning and multiphoton microscopy) as well as working with diverse culture systems for Populus, Arabidopsis and ectomycorrhizal fungi.

Current employements

• Since June 2023: Senior Lecturer (part time) at the Department of Forest Mycology and Plant Pathology; Division of Forest Microbiology, SLU Uppsala
• Since August 2022: Project coordinator (part time) Climate Change Leadership at Department of Earth Sciences, Uppsala University

Previous employments

• May 2020 - May 2023: Senior Lecturer at the Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, SLU Umeå
• November 2016-April 2020: Associate senior lecturer (Biträdande lektor) at the Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, SLU Umeå
• 2014-2016 Researcher at the Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, SLU Umeå
• 2010-2013 Postdoc, Swedish University of Agricultural Sciences, Umeå Plant Science Centre, SLU Umeå

Education

• 2020 - Appointed Docent in Plant Biology by SLU Umeå
• 2006-2009 German-French PhD in Plant Biology, Université Henri Poincaré Nancy, France and Albert Ludwigs Universität Freiburg, Germany
• 2006 MSc Molecular and Cell Biology, Ecole Normale Supérieure de Lyon, France
• 2004 BSc Biochemistry, Ruhr-Universität Bochum, Germany

I have so far supervised seven postdocs, one PhD student, two Master and two Bachelor students in my research group. I have furthermore worked with student groups in courses as a supervisor.

My full list of publications is available on Google scholar.

Popular science lecture on the molecular mechanisms in ectomycorrhizal symbiosis (2017).