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Agricultural Trends

Combating viruses with 'gene scissors'

08.03.2019
 

Since its invention, the new genome editing method CRISPR/Cas has enjoyed rapid growth in plant research. Robert Hoffie (27) uses CRISPR on winter barley to make it virus-resistant. We asked the scientist why he uses this method and when his barley could be launched on the market.

Mr Hoffie, when the new CRISPR/Cas tool, also called 'gene scissors', was developed seven years ago, you were still a student. Now you're using it in your own research. Has CRISPR/Cas won you over to plant research?

No, it's not that. I have always been interested in plants and plant cultivation, which is why I chosed to study plant biotechnology. I grew up on the southern edge of the Magdeburger Börde (Germany), where agriculture is an important part of life. The Leibniz Institute of Plant Genetics and Crop Research (Institut für Pflanzengenetik und Kulturpflanzenforschung, IPK) in Gatersleben (Germany) was also close to me at that time, and I visited it almost every year on its open day. I have also always been fascinated by fundamental research, for example in plant physiology. Who knows, maybe without CRISPR/Cas I would be studying aspects of photosynthesis today. But things turned out differently. After my master's I am now working with CRISPR again for my doctoral thesis.

What do you want to achieve with CRISPR?

I want to make winter barley resistant to the yellow mosaic virus. This virus infects the roots via soil fungi and may lead to the plant being severely inhibited in its development or even dying off. This means yield losses and such is a major risk for agricultural undertakings.

Why are gene scissors the right tool?

Because it allows me to work more precisely and directly than any other method. The prerequisite, however, is that the property I want to change can be influenced by intervention at one or at least a few sites in the genome. This is often the case with resistance. Using CRISPR, a specific gene can be deactivated by molecular biological means – in my project, the result is that the barley plant becomes resistant. In this way I imitate a mutation in the genetic material – i.e. in the plant DNA – occurring spontaneously in nature. It is precisely this change that was discovered in an Asian barley breed that is unaffected by the virus. I reproduce the same effect purely in barley that is susceptible to the virus.

Robert Hoffie

studied plant biotechnology at Leibniz University Hannover and worked with the genome editing method CRISPR/Cas9 for his master's thesis. Since November 2016, the 27-year-old PhD student has been at the Leibniz Institute of Plant Genetics and Crop Research (IPK), Gatersleben. As part of the IdeMoDeResBar project funded by the Federal Ministry of Education and Research, he is using CRISPR to work on resistance to the barley yellow mosaic virus for plant cultivation. Robert Hoffie is active on Twitter as @ForscherRobert and is committed to proper discussion about genetic engineering.

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Crispr/Cas

This abbreviation stands for Clustered Regularly Interspaced Short Palindromic Repeats and actually describes a kind of immune system of bacteria. From this a special method of genome editing was developed. The core of the system is the Cas molecule, a protein that acts as 'gene scissors' by cutting the DNA of plants at a particular gene. The protein only finds the desired gene because it carries an image of the DNA segment to which it is to apply the cut. Once it cuts through the DNA, the cell repairs that spot on its own. Small repair errors change the genetic make-up. As a result, mutations can be induced at a precisely predictable position in the genome.

How exactly does the new cultivation method work?

First, I assemble a DNA molecule in the laboratory, so to speak. It contains information on how to produce the gene scissors and on a "navigation system" intended to guide the gene scissors to the predetermined position in the barley genome. We then transfer this DNA molecule into barley cells by a bacterium. We take these cells and regenerate new barley plants through cell culture. With the help of the information introduced, the plant cells then generate the gene scissors (a protein) and the navigation system themselves. When the protein has cut through the target DNA, affected cells repair the site by themselves. In some cases, this can lead to repair errors that cause minimal genetic alterations. The simplest version is that the target gene then no longer functions. Which was precisely our goal, to make the barley resistant to the yellow mosaic virus. And we have achieved it. Our barley is already resistant.

That sounds like your resistant barley is almost ready for the market.

We have shown scientifically with laboratory plants that it works. If we now repeat the process with varieties that are cultivated agriculturally, these varieties could also be resistant in about two years. Then they would have to be tested in the field. But following the July 2018 ruling of the European Court of Justice (ECJ), the case now falls under the Genetically Modified Organisms (GMOs) Directive, as do other so called genome editing methods, which all mimic accidental mutations as occur in nature all the time.

The conditions for the application of our research have therefore changed: we now have to submit an application for approval for field trials. A GMO approval process for a corresponding new variety takes a very long time: ten to fifteen years according to previous experience. From our researchers' point of view, this is the problem with the judgement: it leads to a lengthy, extremely expensive and time-consuming approval process. The point mutations induced do not create any new risk for humans or the environment that would justify such an extensive process.

Aside from the ECJ ruling, will the new cultivation techniques replace the old methods?

No, cultivation will continue to work with all methods available in the future. Traditional cross-cultivation, for example, will always remain the core component when it comes to complex traits that are distributed over a large number of genes. Even when it comes to producing new genetic diversity, cross-cultivation is still the best solution. For example, to cross exotic genetic material from distant relatives in cultivated plants. Smart breeding, i.e. the targeted use of molecular markers in the cultivation process, will also continue. Thereby desired characteristic patterns can be tested in the very early developmental stage of plants, for example in seedlings. Genome editing is a very useful addition, but only one of the tools used in plant cultivation. Where these new processes can be used, however, the breeding processes often become very efficient, cost-effective and much faster.

Do you believe that genome editing methods such as CRISPR/Cas can help to manage the challenges of climate change?

Yes, they can make a contribution. The more opportunities and tools we have at our disposal, the better we can respond to current challenges. Plant research itself is also becoming ever faster and more comprehensive as a result of new developments such as genome sequencing. Today we have more knowledge at our disposal than ever before. So the question is whether we can or want to use all the methods at our disposal to make this knowledge available for cultivation and for agriculture. And if it is possible to produce plants that require less nitrogen fertiliser or pesticide, and also fewer tractor trips across the field, this will ease the burden on the soil, surface and groundwater as well as the atmosphere. Agriculture is a very complex system to which plant cultivation and research can make a major contribution.