Scientists from INRA and Lorraine University in France unraveled a key mechanism in the symbiosis between fungi and trees. During this mutually beneficial interaction, the fungus takes control of its host plant by injecting a small protein that neutralizes its immune defenses thereby allowing the fungus to colonize the plant. This finding is a major advance in our understanding of the evolution and functioning of symbiotic interactions between fungi and plants – relationships that play a significant role in supporting the health and sustainability of our natural ecosystems.
In the complex world of the rhizosphere – the soil surrounding plant roots – thousands of species of bacteria and fungi compete for resources released by plants. Some fungi, such as truffles and boletus, are able to live in symbiosis with plants through their roots, by-passing their competitors to obtain sugars directly from their host. In return, symbiotic fungi allow plant roots to absorb mineral nutrients; this improves the plant’s health, vigor and productivity. Mycorrhizal fungi are one class of symbiotic fungi that make their way to plant roots where they negotiate for housing and all-you-can-eat sugar services. But how does this negotiation play out? Is the host plant able to distinguish between beneficial and parasitic fungi? How does the fungus avoid the plant’s immune defenses during the interaction?