The bountiful fungi saving forests

 By Eniday Staff

While we may be perfectly familiar with words like ‘microbe’, ‘germ’ and ‘bacterium’ when used in a negative sense, almost synonymous with disease, ‘fungus’ has a certain ambiguity to it…

It could be the fungal disease mycosis, or it could be the wonderfully tasty (for those who are not allergic to them) porcini that Italians harvest from under chestnut trees once the late-August rain has passed. Fungus can be a poison that can deceive and even kill us, or it can be the microscopic organism that causes grape must and beer to ferment. Essentially, then, there are good fungi and bad fungi, and they all have one thing in common: they are parasites that need to feed off another organism in order to exist. In fact, even in this respect, there are bad fungi and good fungi, the former, for example, including those that make a plant so ill that it dies, such as Oidium, the white powdery mildews that suffocate leaves, and Peronospora, the downy mildews that cause grapes to go mouldy and turn tomatoes black. The latter, meanwhile, are those varieties that cause a plant to undergo a symbiotic change whereby the fungus takes some of the nutrients from the plant in return for giving it resistance to unfavourable or even, in extreme cases, fatal environmental conditions. This means that whilst there may still be some large forest areas in the world, despite the all too often harmful effects of human activity, it is often thanks to certain fungal species, which do, of course, take certain things away from the host plant, but also, in return, help safeguard its very existence.

Fungi and trees

It was, in fact, based on this observation that a number of essential and abundant fungi were discovered in the laboratories of INRA (the French National Institute for Agricultural Research). A prime example of this is the black pine, which is used in many alpine areas for reforestation and has adapted well to calcareous soils thanks to a particular species of fungus that works together with the roots of conifer trees to protect them against the toxicity of calcium. That said, highlighting this phenomenon and many other similar ones was no easy feat and would certainly take time. Researchers from the INRA laboratories in Nancy, led by Francis Martin, have dedicated decades of their work to doing so. It all began back in the 1980s, when the magnetic resonance spectrometer was used in agronomy for the first time. This tool made it possible to explore the biosynthesis of molecules in plant cells in vivo and see, for the first time, how the various types of tissue that made up certain fungi that targeted the roots of plants behaved, thus gaining an overview of how mycorrhizal symbiosis worked.

One of several mycorrhizal fungal species, Gamarada debralockiae, isolated from Woollsia pungens (MidgleyDJ, Wikimedia)

This is a mutually beneficial mechanism involving the exchange of nutrients, whereby the fungus stimulates the tree’s absorption of the vital mineral components it needs in order to grow and the plant, in return, provides the fungus with the sugars it needs to survive, using up to 25% of what it produces through photosynthesis. What we needed to understand, however, and what were still unclear at that time, were the molecular mechanisms involved in this transfer and why it worked with certain fungus-plant combinations but not others.

The research continues

It was with a view to attempting to answer this question that the current partnership between the French INRA laboratories and the University of California was formed, their common goal being to identify the genes that govern such phenomena. This, at the time, was no mean feat, and the partners sought the involvement of the Oak Ridge laboratories in Tennessee, which were the first to successfully sequence the genome of a tree, the black poplar. The first internationally renowned article on plant genetics and their impact in terms of improving tree yields was consequently published in Science in 2006, although there was still one piece of the puzzle missing in that we still needed to know more about the other side of the symbiotic coin: the fungal aspect. French researchers later succeeded in identifying a number of fungi, including Laccaria bicolor, an extremely common fungus that is edible but not very practical to eat due to its extremely high water content and its lack of consistency.

Laccaria bicolor mushroom (US Department of Energy)

With the help of the American laboratories, they succeeded in sequencing a fungal genome for the first time and even highlighting a particular molecule with the ability to invade the nuclei of the cells of the poplar tree, allowing the fungus to take control of its host, causing the latter to react to certain favourable environmental conditions and gaining nutrients in return. The first scientific articles representing new avenues of research into how mycorrhizal phenomena worked were published in 2008, unearthing hundreds of fungi that could help trees in forests to grow abundantly. The challenge now, of course, is to pinpoint the symbiotic phenomena that could continuously increase the strength of our trees and consequently their role in tackling climate change.

READ MORE: The secret of mushrooms at Fuorisalone by Eniday Staff

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Eniday Staff