Two Small Changes That Could Transform Agriculture

Researchers have taken a major step toward understanding how certain plants can thrive without chemically produced nitrogen. A breakthrough that could eventually reduce the need for artificial fertilizers in crops such as wheat, maize, and rice.

“We are one step closer to achieving a greener and more climate-friendly food production,” say Professors Kasper Røjkjær Andersen and Simona Radutoiu from the Department of Molecular Biology and Genetics at Aarhus University.

The two researchers have led a new study that uncovers a key mechanism in reducing agriculture’s dependence on synthetic fertilizers.

Plants need nitrogen to grow - a nutrient most crops can only obtain through fertilization. However, a few plants, such as peas, clover, and beans, can manage without it. They live in symbiosis with special bacteria that convert nitrogen from the air into a form the plant can use.

Today, scientists around the world are working to understand the genetic and molecular mechanisms behind this process, with the long-term goal of transferring the trait to other crops such as wheat, barley, and maize.

If successful, plants could become self-sufficient in nitrogen, reducing the need for artificial fertilizers, which currently account for about two percent of global energy consumption and emit large amounts of CO_₂.

Now, researchers from Aarhus University have identified exactly which small changes in plant receptors cause them to switch from activating their immune defenses to instead initiating symbiosis with nitrogen-fixing bacteria, which is a remarkable and important discovery, emphasizes Simona Radutoiu.

Friend or foe?
Plants use receptors on the surface of their cells to detect signals from microorganisms in the soil. Some bacteria signal “enemies,” triggering the plant’s defense mechanisms, while others signal “friends,” helping the plant obtain nutrients.

Leguminous plants such as peas, beans, and clover invite special bacteria into their roots. These bacteria can convert nitrogen from the air and pass it on to the plant. This partnership, known as symbiosis, allows legumes to grow without synthetic fertilizers.

In their new study, researchers from the Department of Molecular Biology and Genetics discovered that this ability is largely governed by just two amino acids - two small “building blocks” in a protein located in the plant’s roots.

This protein acts as a receptor that perceives bacterial signals and decides whether the plant should sound the alarm (activate immunity) or welcome the bacteria (start symbiosis).

The researchers identified a small region in the protein, which they named Symbiosis Determinant 1. It functions like a switch that determines which message is transmitted inside the plant cell. By changing just two amino acids in this switch, the researchers were able to transform a receptor that normally triggers immune defense into one that initiates symbiosis with nitrogen-fixing bacteria.

“We’ve shown that just two small changes can make plants alter their behavior in a crucial way from rejecting bacteria to cooperating with them,” explains Simona Radutoiu.

Goal: Transfer the trait to wheat, barley, and maize
In the new study, the modification was carried out in the plant Lotus japonicus. But the same principle was also found to apply in barley proteins. “It’s quite remarkable that we can now take a receptor from barley, make the corresponding small changes, and see nitrogen fixation restored,” says Kasper Røjkjær Andersen.

The implications are significant. If this new understanding can be transferred to other crops, it could one day be possible to give cereals such as wheat, maize, and rice the ability to fix nitrogen themselves just like legumes do today.

“But there are still other essential keys we need to find first,” notes Simona Radutoiu, adding:
“Only very few crops can form symbiosis today. If we can extend this ability to staple crops, it could make a real difference in how much nitrogen agriculture requires.”

Such a development could revolutionize farming by reducing dependence on synthetic fertilizers, cutting CO_₂ emissions, and making food production more sustainable.

Years of collaboration
The breakthrough is the result of years of collaboration and dedicated work by a large research team at Aarhus University. The main body of experimental work was carried out by Magdalini Tsitsikli, Bine Wissendorf Simonsen and Thi Bich Luu, who are the study’s three first authors.

"This project shows what's possible when skilled PhD students and postdocs work together across disciplines. Collaboration really is at the heart of scientific progress," says Professor Simona Radutoiu.

She emphasizes that the achievement reflects the strong research environment at the Department of Molecular Biology and Genetics, where teamwork across experience levels continues to drive discovery.