Could Self-Fertilizing Cereals Spell the End for Chemical Fertilizers?

Each technology revolution brings its own solutions, but also generates its own set of new problems. Before the invention of airplanes, there were no plane crashes. Of course, you also needed several months to sail across the Atlantic ocean. Likewise, the development of chemical fertilizers, mainly nitrogen, saved millions of humans from starvation in what was named the “green revolution.” The dark side of these chemicals, however, are effects such as eutrophication. This process means that the proliferation of microalgae, driven by an excess of nutrients, consumes all the oxygen available in a water mass, making life unsustainable. The manufacturing of chemical fertilizers is an exceedingly energy-intensive process too, as well as one of the main culprits of carbon dioxide emissions. Now, the Biological Engineering Department at MIT is exploring alternatives to solve the problem. Their approach is adding bacterial genes to crops and develop self-fertilizing properties.

Bacteria and legumes maintain a naturally symbiotic relationship, as the former can fix nitrogen from the air and put it into the soil through a set of genes known as nif. In theory, if the genetic expression of this bacteria could be added to other crops such as cereals, we would be able to grow new self-fertilizing species. That is the technology project of the MIT scientists. The challenges, however, are monumental, as these genes form complex clusters that cannot be plucked and chucked into somewhere else just like that. This is more like a DNA transplant, with all the involved complexity. Additionally, the bacteria in charge of fixing nitrogen are prokaryote cells with a radically different genetic expression from plant cells, which are eukaryotes.    

Distant cousins

Hence, to create these self-fertilizing species, instead of combining different cells, the researchers have organelles, i.e., structures within the eukaryotes. These organelles, called mitochondria and chloroplasts, have a common ancestry with bacteria, as millions of years ago, they existed as independent prokaryotes. It’s a bit like if, instead of trying to solder to cars, we took the engine from one and mounted it in the other. In addition to this, nitrogenase, which is the enzyme that bacteria use to fix nitrogen, requires a lot of energy and is also very sensitive to the presence of oxygen in the environment. Luckily, these organelles produce plenty of energy and are comfortable in low oxygen environments, which makes them ideal allies.

An ongoing research

MIT is carrying out tremendously ambitious research to develop self-fertilizing cereals that has required experts from all over the world. Ralph Block, a specialist in chloroplasts from the Max Planck Institute in Germany, and Luis Rubio, an expert in nitrogenase, are tow of the most important ones. The team has used yeast as a gene delivery system for nitrogenase, which is then targeted to mitochondria. The main milestone reached by the team has been the expression of a NifDK tetramer, an essential protein in the nitrogenase cluster. However,researchers of this technology project are confident that they will be announcing further progress in the coming months that could usher in a new era in cereal production.   

Source: MIT