Plant and Soil Health: Genetic Controls of Nitrogen Fixation

Scientists have longed dreamed of transferring the nitrogen fixation trait found in soybeans and other legumes to grain crops. Just imagine for a moment all the money growers could save on nitrogen and, by extension, the reduction of nitrogen in surface waters.

Remember that bacteria (rhizobia species) take up residence in the roots, form nodules, take nitrogen out of the air and feed it back to the plant while the plant feeds on water, nutrients and sugars.

However, this is not an easy trait to transfer because it involves multiples genes with different functionalities that have to turn on at different times and do different things. Not an easy task, which is why after thirty years it hasn’t yet been accomplished.

However, this spring British scientists in Norwich, UK, discovered a key protein that controls the movement of calcium in plant cells. This action is a signal that nitrogen-fixing bacteria are near, which triggers the formation of a nodule.

Scientists have known that the interaction between plants and bacteria depends on movement of calcium in plant root cells. Researchers at the John Innes Centre in Norwich discovered a set of proteins which control calcium movement into the cell and its nucleus. The protein series CNGC15s enables the movement of calcium directly into the nucleus (brain of the cell) and transfers the information that nitrogen-fixing bacteria are at the root surfaces.

This signal results in the formation of a nodule that houses the bacteria, setting up the symbiotic relationship between the plant and bacteria. The information about these proteins in the nucleus is one more piece of the puzzle.

Myriam Charpentier of the Innes Centre stated “Although the presence of nuclear calcium signals in plants was demonstrated more than a decade ago, the exact identity of the nuclear calcium channel has remained a mystery. This research identifies the first nuclear calcium channel in plants. Calcium signaling is not only important for symbiosis but also for many other processes happening in the plant during development and in response to the environment. Knowing the identity of the nuclear calcium channel will now enable us to better understand how plants use nuclear calcium signals to grow and respond to their environments.”

We won’t be buying seed of nitrogen-fixing corn or wheat any time soon, but the science of discovery will continue and maybe within a few decades we may see a press release that they have done it—made corn into a self-reliant, nitrogen-fixing plant. And it all started with understanding how it works in soybeans.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com or ring him at 402-649-5919.