It took a group of more than 200 researchers from 20 countries (IWGSC) around 13 years to decipher the complex genome of wheat almost completely. Thanks to these new findings, we can now hope not only to be able to breed new, high-yielding wheat species more quickly in the near future but also to breed out allergens.
“We have researched a single wheat variety called Chinese Spring,” says Dr. Manuel Spannagl from Helmholtz Zentrum in Munich, which together with the Leibniz Institute for Plant Genetics and Crop Plant Research (IPK) Gatersleben played a leading role in the study. This wheat variety is “the laboratory rat” for wheat research, so to speak, he explains. Although it is no longer to be found in the field, it is “the model plant on which the scientists have agreed and we have sequenced this one line. It’s 94% complete.”
Chinese Spring is a bread wheat and according to Dr. Spannagl it is genetically more complex than durum wheat. “Bread wheat has three sub-genomes. It was formed by crossing a durum wheat with two sub-genomes and a grass variety that has only one sub-genome. Therefore, it has three sub-genomes.” Durum wheat, which is used for pasta production, has only two sub-genomes, and – one can hear and be amazed – humans only have a single sub-genome. Moreover, the human genome comprises around 20,000 genes, that of bread wheat 107,891.
More complex genome in wheat than in humans
“So that means that wheat is more complex than human beings”, says Spannagl. “The genome of wheat is much more complex than that of man. Human beings do not have by far the most complex genetic material of all living beings. Some plants have a much larger genetic make-up, with many more genes than humans. Bread wheat is a very good example, but it is not the end of the story either.”
However, the bread wheat was “already a really difficult genome to crack”. The complete sequencing of the genome, therefore, seemed impossible for a long time. “The more sub-genomes an organism has, the more complicated it is to sequence and analyse. The three sub-genomes give us three copies of each gene”, said the scientist. “This makes it very interesting, but also very complex.”
In the future, the researchers might even be able to crack 100% of the genome, but that is not so important, says Spannagl. “There are still a few areas of the genome that are very difficult to sequence because they consist of constantly repeating sequences. For most applications and most questions, it is probably not even necessary to sequence the genome to 100%. “We assume that in the 94% we now have, we have covered most or all genes. This 6%, which is still missing, most likely contains only repetitive elements, but are not responsible for proteins.”
Scientists hope that the results of their research will lead to a significant acceleration of breeding progress with innovative breeding methods and targeted breeding, “which also makes greater use of genomic information where a specific gene actually lies on the genome”. So far, the breeding of a new wheat variety takes about ten years. Considering that wheat, according to a publication by the research group, is the staple food for more than a third of the world’s population and accounts for almost 20 percent of calories and proteins, this would be an important step for people worldwide. In about two to three years, it should be possible to expect initial success in the use of the genome for breeding, assumes Spannagl.
But if anyone hopes that there will be wheat in the future that does not make people fat, they have to bury that hope. “I don’t think so,” laughs Spannagl. “That would be nice. However, it is mainly a question of resistance to pests. We have now sequenced one type of wheat, but of course, there are thousands of varieties, some of which have very different characteristics. There are also some that are naturally resistant to some pests. Many of the elite varieties we have on the field have a high yield, but are very susceptible to pests.” It is precisely these varieties that must now be made resistant to the pests. “It is very interesting to know that this gene is responsible for resistance to a certain pathogen.”
Spannagl calms everyone who is now afraid of genetically modified wheat. These resistances could be achieved with completely normal, conventional breeding. “This has nothing to do with genetic engineering. One could do the same with genetic engineering, but it is also quite normal with conventional breeding. These are two different tracks, the result is the same.”
With the CRISPR gene scissors, on which the European Court of Justice recently ruled, the result could perhaps be achieved even more quickly, “in principle such a thing is possible through the genetic material information that is now available, but also through conventional breeding.”
Hope for allergy sufferers
In an additional study, the researchers also analyzed the genes involved in allergies. That’s good news for everyone who is gluten intolerant, for example. “With the presence of the genetic material, we were able for the first time to clarify all genes responsible for the various wheat intolerances. There are not only gluten but many different incompatibilities,” says Spannagl. In order to get this far, the scientists had to clarify which genes are located where and what tasks individual genes have: “We have not found any new genes that are responsible for this, most of them were already known, but we have now been able to cat them precisely on the genome. This is the prerequisite for breeding wheat varieties that contain less gluten or less of the allergenic substances.
“There are these three sub-genomes in the wheat genome and thus three copies of each gene. If each gene and its three copies are now completely expressed, i.e. translated into a protein, then suddenly the triple amount of these proteins is available,” explains Spannagl. In some cases, however, this may not help the organism at all, perhaps too much of a good thing. “It is very exciting for us to see which genes in some of these three subgenomes are expressed in triplicate, which genes are regulated down. The organism has to regulate in a very complex way how strongly some genes are switched on and off.”
It is not so long ago that these three sub-genomes came together in the genome and it is therefore still a “work in progress” and therefore “very exciting to see how the organism regulates the switching on and off of genes and what the functions are for the genes that are regulated in such a way. Are they responsible for growth, for example? Or are they responsible for any resistance?”
Spannagl emphasises that this is very exciting because, like the human genome, earlier plant genomes that were sequenced, e.g. rice or corn, have only one subgenome. “They were much simpler, they didn’t have these three subgenomes. This is the first time that we have an organism with grasses or cereals that has these three sub-genomes and will actually be able to be looked at in this detail.”