Half of the plant protein in the EU comes from canola. Until now, the plant has only been used for oil and animal feed, as it is both bitter and dangerous for human consumption. In a new study published in Nature, researchers from the University of Copenhagen have come close to removing the plant’s bitter substances, paving the way for a new source of protein to support the green transition.
Fields of yellow flowers are a sure sign of summer. In Denmark, more than 200,000 hectares of rapeseed are now grown for use as edible and industrial oils and as a protein supplement for animal feed – but not as a direct source of food for humans. While the high content of bitter preservatives in the canola plant protects against disease and herbivores, they also make the plant unfit for human consumption.
Now, a team of researchers from the University of Copenhagen’s Department of Plant and Environmental Sciences has identified the proteins that help store bitter substances in the seeds of watercress, a model plant and a close relative of canola. The new research result has just been published in the scientific journal Nature.
The knowledge can be used to remove these proteins and thus, the bitter taste of rapeseed, which offers a wealth of possibilities. Indeed, half of the EU’s locally grown vegetable protein already comes from canola.
“The climate crisis demands that we reduce meat consumption and eat more plants, where canola has great potential as a new source of plant proteins in the green transition. Our latest research results bring us a critical step closer to the full use of canola,” says Professor Barbara Ann Halkeer, who led the research.
The substances in wasabi and mustard are gone
The bitter protective substances in canola are called glucosinolates and are best known for the spicy flavors of wasabi and mustard. As a result, so-called rapeseed meal, which is the residue from the seeds after the oil has been squeezed out, is only used in limited quantities as feed for pigs and chickens, despite its staggering 30-40 percent protein content.
The researchers were able to remove the bitter protective substances by identifying the three proteins in the plant responsible for transporting the substances into its seeds. The new knowledge makes it possible to prevent the accumulation of these substances in seeds by removing the proteins through a technology called “transport engineering”. As such, the protective substances remain in all other parts of the plant, allowing it to continue to defend itself.
“Our research shows that the connection – a kind of umbilical cord – that exists between the seed and the surrounding fruit coat is a cellular factory for the production of glucosinolates that end up in the seed. After all, plants are well rooted in the soil and cannot simply leave when there is danger. They must produce a host of defense substances to protect themselves from disease and herbivore attacks. Our discovery allowed us to find a way to eliminate these bitter substances from the seeds,” said Dr. Deyang Xu, lead author of the new study.
A breakthrough ten years in the making
So far, the researchers have shown that their method works in watercress (Arabidobsis thaliana), a model plant closely related to the canola plant.
“The next task is to show that we can transfer our result from Arabidopsis to the closely related canola plant, which we are now working on,” says Dr Xu.
The research that led to this discovery is the result of extensive work made possible by a 10-year grant from the Danish National Research Foundation to the DynaMo Center at the Faculty of Life Sciences in the Faculty of Plants and the Environment.
“I cannot emphasize enough how important this long-term grant was to us being able to achieve this major research result.” It really gave us time to dive into the details and have fun, which paid off,” says Barbara Ann Halkeer.
Facts about plant protection
Plants from the Cruciferous family are characterized by the fact that they can produce a group of protective substances called glucosinolates. These substances give plants such as broccoli, cabbage, arugula, and canola a strong, bitter taste that scares off herbivores and disease.
To protect their offspring, watercress and the closely related canola plants fill their seeds with glucosinolates so that the seeds and young seedlings can defend themselves against insects and other enemies. Since seeds cannot synthesize glucosinolates themselves, the substances must be transported from the mother plant to the seeds.
Some glucosinolates are healthy, such as those in broccoli and other types of cabbage. However, the glucosinolates in the seeds of the canola plant are unhealthy.