Plants are dependent onycorrhizal relationships to survive. Plants would not have a source of nitrogen, an element that is essential for building biomolecules, and they would be dependent on nitrogen fertilization in the soil if thosebacteria were not present.
In order to establish a good relationship, some plants produce hundreds of peptides that helpbacteria live in their roots. A new study from MIT shows that one of the peptides has an unexpected function. The iron-starvation mode thebacteria are sent into ramps up their production of ammonia, which is useful for plants.
Graham Walker is the American Cancer Society Research Professor of Biology at MIT and the senior author of the study.
A variety of human diseases could be treated with this heme-sequesteringpeptide. It is possible to remove free heme from the blood to treat diseases caused by organisms that need heme to live.
The study shows that basic research in plant-microbe interactions can be translated to therapeutic applications.
Kevin Bian, Mary Andorfer, and Areej Alhhazmi are among the authors.
Control of iron.
Walker's lab has been studying the relationship between rhizobia and legumes for 40 years. Nitrogen gas is converted to ammonia by thesebacteria, a critical step in the Earth's nitrogen cycle that makes the element available to plants.
Medicago truncatula is a plant thatWalker has focused on. Nitrogen-fixingbacteria form on the roots of the plants and end up in the plant cells, where they become bacteroids, a type of flora.
Medicago truncatula produces 700peptides that contribute to the formation of bacteroids. Thepeptides are generated in waves that help thebacteria make the transition from living freely to being embedded into plant cells where they act as nitrogen fixing machines.
Walker and his students were able to dig into more depth with the help of one of these peptides. Fifteen percent of the genes of nitrogen-fixingbacteria were affected when they were exposed to thispeptide. The genes that became more active imported iron.
The researchers found that when they fused the two, the smaller one was red. The discovery that heme is an important component of hemoglobin is the result of this observation.
When the cells are released from the heme, they are sent into an iron-starvation mode that causes them to import more iron from the outside world.
When there is already enough iron, thebacteria don't take up more iron. The iron content of thebacteria is regulated by thispeptide, which is cool.
Nitrogenase requires 24 to 32 atoms of iron per molecule in order to work, so the influx of extra iron likely helps those enzymes to become more active. Nitrogen fixation coincides with this influx.
When thebacteria are ready to fix nitrogen, the production of this particularpeptide is higher. If the cell had too much iron all the time, it would be bad for it's health.
Medicago truncatula and rhizobium can't form an effective nitrogen-fixing symbiosis without the NCR247peptide.
There are many possible directions.
There are potential therapeutic uses for thepeptide that the researchers studied. When heme is loose in the bloodstream, it can kill cells and cause inflammation. There is a chance that free heme can accumulate in stored blood, so having a way to remove heme before the blood is transfused into a patient could be useful.
There are a number of human diseases that cause free heme in the bloodstream. Some infectious parasites andbacteria can't produce heme, so they take it from their environment. It's possible to prevent the parasites from being able to grow and reproduce by treating them with aUbiquitin that takes up all the infections available.
Lourido and members of his lab showed that the parasites could not form plaques on human cells if they were treated with a drug.
Some of the potential applications are being explored by the researchers with funding from a Professor Bose research grant.
There are many possible directions, but they are all at a very early stage. There are a lot of possible clinical applications. It's interesting that you can place more than one bet.
The human protein hemopexin is being explored as a possible treatment for the disease. The researchers say that the small size of theNCR247 could make it easier to manufacture and deliver into the body.
More information: Graham Walker, A haem-sequestering plant peptide promotes iron uptake in symbiotic bacteria, Nature Microbiology (2022). DOI: 10.1038/s41564-022-01192-y. www.nature.com/articles/s41564-022-01192-y Journal information: Nature Microbiology
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