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"Curiosity is the driving force behind my research"

Mette Vestergård Madsen is a trained biologist. Today, she studies plant self-defence, keeps track of soil microorganisms and the interactions between plants and life in the soil at the Department of Agroecology at Aarhus University.

Photo: Mette Vestergård Madsen

It is curiosity that makes Mette Vestergård Madsen drive to Flakkebjerg, a village close to Slagelse in Denmark, every day. This is the home of Aarhus University's department called AU Flakkebjerg, where Mette Vestergård Madsen works as a senior researcher in her fifth year. But her curiosity started when she was studying biology at the University of Copenhagen.

"I hadn't been studying for very long before I realised that the biology of soil and its organisms was the way forward for me," she says.

Curious and newly qualified biologist

In 2003, she was a newly qualified biologist and had to find the right way forth. The choice was not difficult, because her curiosity was strong, and a PhD at the University of Copenhagen on interactions between plants and life around plant roots was the next step. But as is the case with curiosity, it can change shape and, not least, subject matter, and it did for Mette Vestergård Madsen. After submitting her PhD thesis, she applied for a Carlsberg scholarship for a postdoc position.

"Back then, you could apply for grants where you didn't have to leave the country, and I was lucky enough to get a three-year project," she says.

For three years, she worked on investigating and describing ancient communities of nematodes, the very organisms that occupy much of her time today.

Fact box - Nematodes

Nematodes are roundworms. They are one of the most widespread animals on Earth, with an estimated 1 million species. Nematodes are found in a wide range of environments, from soil and freshwater to marine environments and even inside other organisms. They vary greatly in size, from just a few micrometres to several metres in length.

Nematodes play important roles in ecosystems, both as decomposers and as predators or parasites of other organisms. Some nematodes function as pests of crops and animals, where they can cause significant economic damage. Others are used for various purposes, such as biological control and compost production.

"We extracted nematode DNA from permafrost sediments up to 40,000 years old, and in this way, we were able to map which nematodes lived in exactly those areas so many years ago. It was very fascinating," says Mette Vestergård Madsen.

PhD with a focus on nematodes

When the three years were up, Mette Vestergård Madsen returned to the same research group were she had written her PhD thesis, but this time as a postdoc and later as an assistant professor. Here she worked on how climate change affects life, processes and metabolism in the soil.

"I also worked on other projects, but all my work was centred around life in the soil, what it means for plant growth and, not least, how it responds to human impact," she says.

Six years ago, while buried in her research, she came across a job advert that contained a keyword that once again sparked her curiosity. This time it was a tenure track assistant professor position at Aarhus University, and the job advert focused on nematodes, among other things.

"I had never before seen a job advert that mentioned nematodes. My curiosity was piqued, and I simply had to apply for the job," says Mette Vestergård Madsen, who at the time was not entirely sure if she would get the job:

"The position was in plant pathology, and I wasn't a plant pathologist. On the other hand, I was involved in a GUDP project where Per Kudsk was the project coordinator, so in that way, I had been a bit involved, so to speak, in the world of plant pathology."

Pairing up on interactions between plants and the soil microbiome

Five years later, Mette Vestergård Madsen is sitting in her office at AU Flakkebjerg with a view of a large flowering magnolia tree and can talk about five years of research at the Department of Agroecology.

"My focus is on interactions between plants and the soil microbiome, and in addition, I have my very own niche that deals with nematodes. It's not only the nematodes themselves that make me curious, but also their interaction with plants. It's exciting to investigate and uncover how the plants affect the nematodes and vice versa, and how the nematodes interact with soil microorganisms," says Mette Vestergård Madsen, who is currently - in partnership with Professor Mogens Nicolaisen also from Aarhus University  - playing an important role in a new and large EU project called BarleyMicroBreed.

"We study the genome of barley plants and investigate whether there are specific genes in the barley plant that help control which microorganisms are selected on the roots. In addition, we are investigating whether these particular microorganisms can help strengthen the plant's resistance to drought," she explains.

Basic research that connects to reality

Basic research has been an important element of Mette Vestergård Madsen's research, and one of the things that has been consistent throughout her career, whether it has been about nematodes or not, is a focus on the mechanisms plants use to control the composition of microorganisms around their roots.

"Among other things, we study metabolites. These are, for example, signalling and defence substances found in the plant that can attract or inhibit microorganisms in the soil. Among other things, we will look at this in the EU project," she explains.

Applicability is also important to the senior researcher, who hopes that her research will contribute to a better understanding of the mechanisms in the interaction between plants and microorganisms in the soil.

We must learn from nature

According to Mette Vestergård Madsen, it is precisely these mechanisms that are important to understand. In collaboration with Professor Inge Fomsgaard from the Department of Agroecology, she is therefore working on co-cultivation of different plant species. It seems that plants can help each other and together create a strengthened defence system, and this could perhaps be used to design future cultivation systems where the total load from pests is less.

"We can learn from natural systems. We may have missed something in the cropping systems we have today, where monoculture is dominant. In the future, we can focus more on the interaction between plant genes and the selection of microorganisms around the roots. For example, there are plenty of microorganisms in the soil that can promote plant growth or protect plants from pests, and if you breed plants that are able to optimally co-operate with the organisms that already exist, I believe that this will be far more sustainable than, for example, adding growth-promoting bacteria to the soil or plants," she explains.

The curiosity is a constant

Back to curiosity, it's still there, and it's greater than ever before. As Mette Vestergård Madsen herself puts it, what researcher doesn't dream of making a major scientific discovery, or at least of moving things in a purely scientific sense?

"You want to make a difference in the world," she says, and explains that the unique facilities at AU Flakkebjerg, where she can grow plants in a petri dish, a growth chamber or greenhouse, or even just step out the door and take her experiments into the field, help to support her research and, not least, feed her curiosity. There are plenty of opportunities here for research to continue at the highest level, and who knows, maybe that curiosity will eventually lead to a discovery that truly changes the world.

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