The term “symbiosis” comes from the Greek word “Symbioun,” meaning “to live together.”
Parasitism, commensalism, and mutualism are the three main types of symbiosis. They govern the relationship between two or more different species of organisms living closely in the same environment.
When the symbiotic association benefits only one partner, while the other gets no harm nor benefit, that’s commensalism. If the two parties benefit from each other, it’s a mutualist relationship. The most unfair symbiotic relationship is parasitism, where one partner benefits while the host suffers.
But this is just like scratching the surface because there’s a lot more to be uncovered about the mechanisms underlying some symbioses. One good example is the intimate interaction between plants and soil fungi.
The Molecular Secrets of Symbiosis
What would we get from knowing the minute details of plant–microbial symbiosis?
Here’s Jessy Labbe, a molecular geneticist at Oak Ridge National Laboratory (ORNL), explaining:
“If we can understand the molecular mechanism that controls the relationship between plants and beneficial fungi, then we can start using this symbiosis to acquire specific conditions in plants such as resistance to drought, pathogens, improving nitrogen and nutrition uptake and more. The resulting plants would grow larger and need less water and fertilizer, for instance.”
Labbe led the team of researchers at ORNL who identified the specific gene that controls the symbiotic relationship between plants and soil fungi.
Symbioses with mycorrhizal fungi have supported plants in the distant past to colonize the land. They do this by forming vast forests and prairies. According to the researchers, around 80% of all the plant species rely on mycorrhizal symbioses, and this is how it works.
Mycorrhizal fungi cover the roots of plants and form like a sheath extending far deeper than the plants’ roots. This way, the host plant increases its nutrient uptake and “even communicating with other plants to “warn” of spreading pathogens and pests. In return, plants feed carbon to the fungus, which encourages its growth.”
This is all already understood, but the ORNL team managed to pinpoint the genetic triggers that tell a plant to associate with soil fungi for its own good. The gene can even trigger symbiosis in plants that usually resist it.
The present research, described in Nature Plants, was started ten years ago by ORNL scientists with collaboration from partner institutions. Their initial goal was “exploring ways to produce better bioenergy feedstock crops such as Populus, or the poplar tree.”
The discovery of the genetic underpinnings of symbiotic plant-fungal relationships could boost crop productivity and lead to climate-resilient and pathogen-resistant food crops that need less land, pesticides, and chemical fertilizers.
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