Nitrogen fixation is the process by which atmospheric nitrogen is converted into ammonia, which can then be used by plants to produce proteins and other nitrogen-containing compounds. This process is essential for plant growth, but it is also very energy-intensive. Legumes have evolved a symbiotic relationship with rhizobia, which are bacteria that live in nodules on the roots of legumes and convert atmospheric nitrogen into ammonia.
The debate over how rhizobia breach the cell walls of legumes has been going on for over 125 years. Some scientists believe that rhizobia use a process called "cell wall degradation," in which they secrete enzymes that break down the plant's cell walls. Others believe that rhizobia use a process called "invasion," in which they physically penetrate the plant's cell walls.
In their study, the JBEI team used a combination of microscopy and molecular biology techniques to show that rhizobia use both cell wall degradation and invasion to breach the cell walls of legumes. The team found that rhizobia first secrete enzymes that break down the plant's cell walls, and then they use these enzymes to create channels through which they can physically penetrate the cell walls.
This discovery has important implications for the development of more efficient nitrogen-fixing crops. By understanding how rhizobia breach the cell walls of legumes, scientists can design crops that are more resistant to rhizobia infection, which could lead to increased nitrogen fixation and improved crop yields.
"This study provides a new understanding of the molecular mechanisms underlying the symbiotic relationship between legumes and rhizobia," said JBEI Director Jay Keasling. "This knowledge could lead to the development of more efficient nitrogen-fixing crops, which could have a major impact on global food security."
