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New wheat mutant can teach us more about spelt

Researchers from the Department of Agroecology at Aarhus University have by chance discovered a mutation that makes wheat speltoid.

2020.12.16 | Camilla Brodam

From the left is wheat and from the right is spelt.

There is a difference between wheat and spelt both in terms of appearance and baking properties, some even believe that spelt may be the ancestor of wheat, but according to Claus Krogh Madsen from the Department of Agroecology, this is not exactly the truth.

“A lot of people have a notion that spelt is a form of "wheat". In the past, there was a theory that spelt is the ancestor of wheat because it has some features in common with wheat’s wild ancestors. It has long been shown that these traits are linked to a particular variant of the gene Q called the q variant. Today, there is both archaeological finds and DNA evidence that the q variant has been reintroduced into wheat at a cross with one of the wild ancestors. This means that ordinary wheat is the oldest and the difference lies in a single gene,” he says.

For more than a hundred years, researchers have known about the gene Q, which could be studied using classical genetic methods, ie. crossbreeding and studies of the offspring. The molecular identity of the Q gene - the DNA sequence - was first established with two articles from 2003 and 2006 from a US group of researchers.

New mutant found via in silico TILLING

By chance, Claus Krogh Madsen and his colleagues discovered a wheat mutant, which in appearance resembles spelt with the characteristic elongated spike and powerful outer kernels, which are difficult to thresh. But it was not a sort of spelt they were dealing with, it was wheat. The mutant had been sent to researchers among a shipment of various other mutants from an in silico TILLING seed bank operated by the John Innes Centre in England.

In silico TILLING is a method of finding mutations in specific genes. It works by creating a collection of mutated plants that is DNA sequenced. The information is gathered in a database, in which researchers can find mutants for the exact gene they are working with. However, each mutated plant has many other mutations that complicate the work with this type of material.

"I got the suspicion that this mutant had a mutation in Q in addition to the mutation that I was actually interested in. Because the mutant was already DNA sequenced and available in the database, it was easy for me to get my suspicion confirmed. You could say I made in silico TILLING the other way around. Even though there was a mutation in Q that made the wheat look like spelt, it is not the exact same mutation found in real spelt, i.e. the q variant,” says Claus Krogh Madsen. 

Spelt is wheat with a small genetic difference

The researchers decided to investigate the wheat mutant further in the hope of being able to learn more about wheat and spelt and what it is that distinguishes the two species. To confirm that it was the mutation in Q that made the studied wheat speltoid, the researchers made a so-called backcross. They took a wheat that did not have the mutation and crossed it with the mutated one, to investigate how the mutation splits in the next generations. Some of the offspring had the mutation, others did not, and by examining the axes, the researchers could see that the spelt-like axis followed the mutation and thus get confirmation that it is precisely a mutation in Q that can make wheat look like spelt.

"This study supports a theory, that if something happens to the gene Q that makes the gene or the protein code less active, then wheat becomes more like spelt. This is because the protein that Q encodes is a so-called transcription factor - a protein that helps regulate other genes by binding to DNA. It is this pile of other genes, which is controlled by Q, that ultimately creates the differences one can see when comparing grains of wheat and spelt. With this mutation, we have shown that a certain area of ​​the Q protein cannot be dispensed with if wheat is to be wheat as we know it. We have thus gained a much greater understanding of how the Q gene works,” says Claus Krogh Madsen.

Can create a basis for further research

Previously, only two extremes were known. Common wheat with variant Q or spelt with variant q. That is, either you had wheat, as we know it with grains that are easy to thresh, or you had spelt with long axis that are very difficult to thresh. The new mutant is very close to spelt, and in recent years mutants, which are more extreme versions of common wheat, with extra compact spikes have also been found. It seemes that different "strengths" of Q can create new varieties, which are placed somewhere between wheat and spelt, or some that are even more extreme.

“There can be a lot of advantages to being able to manipulate Q. The shape of the axis is linked both to the yield and to the technical properties of the wheat. In addition, it is believed that there is a link between Q and baking quality. It is really an interesting,” says Claus Krogh Madsen.

According to the researchers, the discovery of the mutation in the Q gene calls for new research in wheat and spelt. Among other things, it could create a basis for a study of whether spelt is in fact healthier than wheat, as it is commonly known to be.

“If you really want to investigate, e.g. if spelt is healthier than wheat, then it is useful to have a mutant like the one we have found as a reference. It has this one gene, which makes it spelt similar, but otherwise it is like ordinary modern wheat. This means that it will be possible to use it to investigate whether any differences in spelt and common wheat are directly linked to the spelt gene q, or whether it is due to other genes. If you found a good property in spelt that is not linked to q, you can just transfer it to modern wheat and avoid the disadvantages of spelt,” says Claus Krogh Madsen.

Behind the research
Collaborators: Department of Agroecology at Aarhus University
Financing: The Innovation Fund Denmark
Conflicts of interest: None
Read more: The publication  ”A novel wheat q’ allele identified by forward genetic in silico TILLING” is written by Claus Krogh Madsen and Henrik Brinch-Pedersen
Contact: Claus Krogh Madsen, Institut for Agroøkologi, Aarhus Universitet. E-mail: clauskrogh.madsen@au.dk

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