Potsdam researcher investigates underground relationships

Top researcher from Potsdam receives €2 million for research into an underground relationship between plants and fungi.

December 12, 2023

Prof. Dr. Caroline Gutjahr, Director at the Max Planck Institute of Molecular Plant Physiology in Potsdam, has been awarded one of the highly prestigious Consolidator Grants from the European Research Council (ERC). In her project "SymbioticExchange", she will investigate how the close coexistence of plants and friendly fungi in the soil works and how the exchange of nutrients between the symbiotic partners is regulated. Her findings could contribute to a new form of agriculture that considers fungi and plants in tandem.

A hidden world

It may sound trivial, but hardly anyone thinks about plant roots. It is understandable. They are underground - out of sight, out of mind! But right under our feet, an intimate relationship unfolds. Almost all plants live in symbiosis with one or more species of fungi. Under the ground, fungi don't look like mushrooms. They form fine threads (hyphae), which can sometimes grow into kilometer-long fungal webs. As fungi are not plants, they have to take up energy-rich organic compounds in order to grow. Many fungi therefore grow their thin hyphae through the soil and digest organic residues. The fungi being researched by Caroline Gutjahr, on the other hand, are not able to do this. They are dependent on a supply of sugar and lipids provided by living plants.

A perfect match

A network of fungal filaments (hyphae) with fungal spores on culture medium.

© Maike Zürn (Gutjahr Laboratory)

A network of fungal filaments (hyphae) with fungal spores on culture medium.

© Maike Zürn (Gutjahr Laboratory)

Plants get their energy in excess from sunlight and use photosynthesis to store it in the form of sugars and other organic compounds produced from CO2. They need their roots to absorb water and vital minerals from the soil. This makes plants and fungi perfect trading partners. Plants feed the symbiotic fungi via their roots with energy-containing substances from photosynthesis. Fungi in turn supply the roots of the plants with water and minerals from the soil, which they acquire with the help of their huge network of hyphae. The fungus and plant thus feed each other. This interaction, known as arbuscular mycorrhiza, is so successful for both symbiotic partners that it has existed for hundreds of millions of years and is found in the majority of land plants worldwide.

An intimate relationship with promising prospects

A root of the grass Brachypodium distachyon under the microscope. The fungal hyphae (colored blue) grow into the root cells and form branched structures, the arbuscules, which can almost completely fill the cells. — A root of the grass *Brachypodium distachyon* under the microscope. The fungal hyphae (colored blue) grow into the root cells and form branched structures, the arbuscules, which can almost completely fill the cells.

© Kartikye Varshney (Gutjahr laboratory)

A root of the grass *Brachypodium distachyon* under the microscope. The fungal hyphae (colored blue) grow into the root cells and form branched structures, the arbuscules, which can almost completely fill the cells.

© Kartikye Varshney (Gutjahr laboratory)

Over millions of years, this relationship between plants and their fungal partners, has developed into one of the most intimate interactions between living organisms. The plant even allows the hyphae of the fungi (gr. myces) to grow directly into the cells of its root (gr. rhiza). This is an unusual process, as the immune system of plants normally prevents this at all costs. In the root cells, both partners then form highly branched structures where substances are exchanged between the fungal and plant cells, the so-called arbuscules (see photo, Latin arbuscula = little tree). How lipids, sugars and minerals are transported from one organism to another, which genes and proteins of the plants and fungi are used for transport and which are used for the perception of the partner, and how these are controlled depending on environmental conditions is the research focus of "SymbioticExchange". "If we understand how plants determine which and what quantities of substances they exchange with the fungi, then we may be able to breed crops that cooperate more efficiently with arbuscular mycorrhizal fungi. If we then introduce the fungi to the fields together with the plants, plants could potentially access the nutrients in the soil much better. This could help to save on fertilizers and protect the environment and climate," says Caroline Gutjahr.

Caroline Gutjahr is Director at the Max Planck Institute of Molecular Plant Physiology in the Potsdam Science Park. She heads the Department of Root Biology and Symbiosis and specializes in researching the interactions between plants and fungi.

With its Consolidator Grants, the European Research Council - ERC supports research projects by top researchers at a mid-career stage who want to boldly advance into visionary new fields of research and who have the potential to open up new scientific fields. The award procedure is highly competitive and the success rate is less than 15%. Together with „SymbioticExchange“, 321 Consolidator research projects with a total volume of €657 million were funded across Europe.