Researchers Identify Genetic Switch to Enhance Nitrogen Fixation

Researchers at Aarhus University have made a significant breakthrough in understanding how certain plants can thrive without reliance on artificial fertilizers. Their study, published in the journal Nature on November 6, 2025, reveals critical genetic mechanisms that could pave the way for more sustainable agricultural practices.

The study, led by professors Kasper Røjkjær Andersen and Simona Radutoiu, focuses on the symbiotic relationship between plants and nitrogen-fixing bacteria. While plants typically require nitrogen from fertilizers, some, such as peas and clover, have developed the ability to engage in a symbiotic relationship with specific bacteria that convert atmospheric nitrogen into a usable form. This discovery could potentially reduce agriculture’s dependence on fertilizers, which currently accounts for approximately 2% of the world’s total energy consumption and contributes significantly to carbon emissions.

The researchers identified small changes in plant receptors that allow them to switch from an immune response to welcoming nitrogen-fixing bacteria. Plants utilize surface receptors to detect signals from soil microorganisms. Some bacteria signal danger, prompting the plant to activate its defenses, while others indicate a beneficial relationship. Legumes, for example, invite nitrogen-fixing bacteria into their roots, enabling them to grow without fertilizers.

The findings indicate that this symbiotic ability is largely controlled by just two amino acids in a protein located in the plant roots. Radutoiu emphasized the importance of this finding, stating, “This is a remarkable and important finding.” The protein acts as a receptor that determines whether the plant should defend itself or engage in a beneficial partnership.

The researchers discovered a specific region in the protein, termed Symbiosis Determinant 1, which functions as a switch for the plant’s internal messaging system. By making minor alterations to two amino acids in this switch, they were able to change a receptor that usually triggers an immune response into one that fosters symbiosis with nitrogen-fixing bacteria. Radutoiu remarked, “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.”

In laboratory experiments, the team successfully modified the plant species Lotus japonicus and confirmed that similar principles apply to barley. Røjkjær Andersen noted, “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.”

The implications of this research are substantial. If the genetic modifications can be adapted to widely cultivated crops like wheat, corn, and rice, it could revolutionize food production by enabling these plants to fix nitrogen independently. Radutoiu cautioned, “But we have to find the other, essential keys first. Only very few crops can perform symbiosis today. If we can extend that to widely used crops, it can really make a big difference on how much nitrogen needs to be used.”

This research represents a promising step toward reducing the environmental impact of agriculture and enhancing food security globally. As the scientific community continues to explore these genetic pathways, the potential for a more sustainable agricultural future is increasingly within reach.