Scientists at Aarhus University have identified a tiny change in a plant root protein that allows crops to form partnerships with nitrogen-fixing bacteria. By altering just two amino acids, researchers transformed a defensive receptor into one that supports nutrient-sharing symbiosis. This breakthrough could reduce reliance on synthetic fertilizers and lower agricultural emissions.
Nitrogen is essential for plant growth, yet most major crops like wheat and maize depend on synthetic fertilizers to obtain it. These fertilizers consume about two percent of global energy and contribute significantly to CO2 emissions. In contrast, legumes such as peas, beans, and clover naturally partner with soil bacteria to convert atmospheric nitrogen into a usable form, eliminating the need for added fertilizers.
A team led by professors Kasper Røjkjær Andersen and Simona Radutoiu at Aarhus University has uncovered a key mechanism behind this natural ability. Plants use cell-surface receptors to detect signals from soil microorganisms, deciding whether to mount a defense or initiate cooperation. The researchers pinpointed a small region in one such receptor, dubbed Symbiosis Determinant 1, which acts as a molecular switch.
By modifying only two amino acids in this switch, the team reprogrammed the receptor to favor symbiosis over immunity. In experiments with the model plant Lotus japonicus, the altered receptor enabled nitrogen-fixing bacteria to enter root tissues. Remarkably, the same tweak worked in barley, a cereal crop, suggesting broader applicability.
"We have shown that two small changes can cause plants to alter their behavior on a crucial point—from rejecting bacteria to cooperating with them," Radutoiu explained. Andersen added, "It is quite remarkable that we are now able to take a receptor from barley, make small changes in it, and then nitrogen fixation works again."
While promising, the researchers caution that additional genetic elements must be identified to fully engineer nitrogen-fixing cereals like wheat or rice. "We are one step closer to a greener and climate-friendlier food production," the professors concluded. Their findings, published in Nature, offer a foundation for developing self-fertilizing crops that could transform sustainable agriculture.