With small changes to cellular machinery, researchers may have begun to transform the relationship between plants and the soil. Their new work could help to develop crops that can collaborate with beneficial nitrogen-fixing soil microbes instead of fighting them off.
“This discovery could help scientists engineer crops that naturally fix nitrogen, reducing the need for chemical fertilizers,” says Simona Radutoiu, a professor of plant molecular biology at Aarhus University in Denmark.
The researchers focused their attention on specific receptor proteins, which in many plants detect molecules on soil bacteria and initiate a protective immune response that fights them off.
But in legumes this process looks different: these plants contain similar protein receptors, but these are able not only to trigger an immune response against some soil bacteria, but also to activate symbiosis with specific types of beneficial soil bacteria, earmarking them as friends, not foes. These bacteria lock in nitrogen from the air and, with the blessing of the plant, colonize its roots and provide it with this nutrient, in exchange for a supply of carbohydrates.
The researchers traced this symbiotic ability back to two key amino acids in plants’ receptor proteins. Then, taking barely—a staple crop—they discovered that if they modified those two amino acids in a barley receptor protein, and then inserted that modified protein into another test plant, they could successfully trigger symbiotic signalling in the plant.
Radutoiu calls this a “transformational” first step towards engineering plants with the ability to fix nitrogen in the future.
Showing that it may be possible to manipulate the immune response that normally overrides symbiosis in plants like barley, means that it might also work in other cereals like wheat and maize, which guzzle up almost half of the world’s fertilizer. Curbing these crops’ cravings for synthetic nitrogen, and instead pairing them up with abundant soil bacteria to supply their needs, could put a potentially large dent in global fertilizer production use.
The researchers’ next steps are to see if barley containing the two modified amino acids can receive and respond to signals from beneficial soil bacteria.
This isn’t the first project dedicated to the idea of self-fertilizing crops. Among other things, scientists—spurred on by the huge scale of fertilizer pollution and its climate impact—are also developing wheat that oozes a bacteria-friendly compound, and crops that can ‘talk’ to surrounding communities of microbes.
Rather than one fix, it’s likely to be a smorgasbord of solutions, like these, that will eventually make self-fertilizing crops a reality.
Tsitsikli et. al. “Two residues reprogram immunity receptors for nitrogen-fixing symbiosis.” Nature. 2025.
Image: © Anthropocene / AI-generated
