Scientists are one step closer to enabling more plants to use nitrogen-fixing bacteria, which would reduce the need for fertilizers and, in turn, lower costs for farmers.
Plants can absorb nitrogen only in some chemical compounds. Some forms of nitrogen occur naturally in soils, but usually not in the amounts needed to increase crop yields. Nitrogen is abundant in the air, but in a form that plants cannot absorb.
“Some bacteria living in the soil are able to convert atmospheric nitrogen into one of the forms that can be used by plants – this is called nitrogen fixation. Several species of plants, mainly from the legume family, have developed root tubers that attract and retain beneficial bacteria. A beneficial symbiosis will allow the plant to absorb nitrogen, and in return, the bacteria will get sugar from the plant,” says Mathias Kirst, a professor of plant genomics at the University of Wisconsin.
But can we teach other plants to develop a similar mechanism? Before answering this question, it is necessary to better understand how legumes, the original nitrogen-fixing plants, create tubers. Identifying this complex process may allow scientists to replicate it in other plants.
“When legumes come into contact with nitrogen-fixing microbes, we know that there is a large release of a plant hormone called cytokinin, and then tubers are formed. In this study, we wanted to get a real-time view of when the hormone is produced,” said Matthias Kirst.
To observe the process, the research team used a method that causes fluorescence in the presence of cytokinin – the area of interest glows in the dark. This will allow researchers to monitor each stage of hormone release. It turned out that cytokinin is released in two stages. At the first stage, it is produced in the outer layer of the root. In the second stage, this inner part of the root is pushed out like a balloon, forming a nodule.
The study also showed that this second step of cytokinin activity is controlled by a gene called IPT3. This is confirmed by the fluorescence method, as well as by observing plants that lacked the IPT3 gene. In this case, formation of nodules did not occur. So this gene plays a key role in the process.
According to Kirst, all plants have cytokinin and the IPT3 gene:
“From a biological point of view, every plant has the components to make a tuber, but the obstacle is that the gene has to work at the right time and in the right place. “Scientists hope that the discovered mechanism will allow other plants to be ‘taught’ to generate tubers,” explained Kirst. After that, the next big question is whether nitrogen-fixing bacteria will move into these tubers.