• Dr Joanne Delange

Cancer Risk from Baked and Toasted Foods to be Reduced with Genome-Edited Wheat


A new strain of wheat is currently in development that has had its genome edited to reduce levels the levels of asparagine, which is a naturally occurring amino acid linked to cancer commonly found in toast.


Following on from our previous insight, where we reported on the UK government's announcement allowing the use of genome editing in crop production, here we are focusing on the research being undertaken by Rothamsted Research, who have been granted permission from the Department for Environment, Food and Rural Affairs (Defra) to run a series of field trials of wheat that has been genome-edited.


Scientists at Rothamsted Research, working alongside scientists at the University of Bristol edited the genome of a standard wheat strain to remove asparagine, which is converted to acrylamide, when bread is baked or toasted.


Dr Sarah Raffan, first author of the paper published in Plant Biotechnology Journal said: 'We've used genome editing to reduce the amount of the amino acid, asparagine, in the grain. It's the asparagine that is converted to acrylamide during baking and toasting, so a low asparagine wheat should lead to lower levels of acrylamide, which is good news for anyone who likes their toast well done.'


Acrylamide


Acrylamide, first discovered in food in 2002, forms during the baking, toasting and high-temperature processing of foods made from wheat. Its levels increase substantially when bread is toasted, and the darker the toast, the more acrylamide it contains.


It is also present in other wheat products and many crop-derived foods that are fried, baked, roasted or toasted, including biscuits, crisps, chips, roast potatoes, pies, batter, breakfast cereals and coffee.


Acrylamide is known to cause cancer in rodents and is considered 'probably carcinogenic' for humans. It is classed as a Group 2a carcinogen by the International Agency for Research on Cancer (IARC), and acrylamide in food potentially increases the risk of developing cancer for consumers in all age groups.


In 2006, a UN FAO/WHO Joint Expert Committee on Food Additives report stated that the potential cancer-causing effects of acrylamide in the diet were a concern. This was reiterated by the EU's CONTAM Committee in 2015, which drew a similar conclusion.


CRISPR/Cas9 Genome Editing


CRISPR/Cas9 is a genome-editing platform that uses an enzyme (Cas9) to make a double-stranded break at a specific location in the genome. It is highly precise and simpler, cheaper and significantly faster than traditional methods. The changes that CRISPR/Cas9 makes to a genome are permanent and can be passed on through generations.


The team of scientists used CRISPR/Cas9 to delete the asparagine synthetase gene, TaASN2, of wheat. In essence, the aim was to halt the function of the gene involved in the production of asparagine, and thus food products produced from the genome-edited wheat will be low in the cancer-risk increasing compound acrylamide.


This approach differs from genetically modified foods, as it doesn't involve the introduction of a new, foreign gene. The changes that the CRISPR/Cas9 approach to genome editing bring to the wheat DNA are similar to those that occur naturally.


Project leader, Professor Nigel Halford explained: 'A number of methods for reducing acrylamide in food products by changing processing methods have been developed. Some have been successful, but they are not applicable to all food types, are often expensive to implement and may have detrimental effects on product quality... The food industry would therefore benefit from the availability of raw materials with lower acrylamide-forming potential, and the determining factor for acrylamide formation in products made from wheat and rye grains, and probably those of other cereals, is the concentration of soluble (non-protein) asparagine.'


DEFRA Permission


Any research trials involving genome editing need to gain approval from DEFRA. With this permission granted, the scientists involved in this study will be the first to conduct field trials of CRISPR-edited wheat anywhere in the UK or Europe.


Professor Halford continued: 'this project aims to assess the performance of the wheat plants in the field and measure the concentration of asparagine in the grain produced under field conditions.'


The researchers have already shown that the asparagine concentrations in the grain of the edited plants were substantially lower when compared to un-edited plants. Conducting the new trial in the field, which is proposed to take up to five years, will allow the researchers to compare the wheat's yield and protein concentration, as well as the amount of asparagine in the grain within field conditions. The CRISPR genome-edited wheat will be compared to wheat in which asparagine synthesis has been altered using the traditional method of chemically-induced mutation. This traditional method is not precise, in the way that CRISPR is, and as such the mutations that occur are found randomly throughout the genome – rather than specifically to the gene that produced asparagine.


Conclusion


Reducing the asparagine levels of wheat would benefit consumers by reducing the amount of acrylamide in their diet. Furthermore, it would benefit food businesses by allowing them to conform to regulations on the levels of acrylamide in their products. However, seeing as the field trial will take up to five years, it is unlikely that bread produced from this new wheat would reach the market until well after the five-year trial comes to a conclusion.


References


Raffan S et al. (2021). Volume19, Issue8, Pages 1602-1613. Plant Biotechnology Journal. Wheat with greatly reduced accumulation of free asparagine in the grain, produced by CRISPR/Cas9 editing of asparagine synthetase gene TaASN2. Available at https://doi.org/10.1111/pbi.13573


Genome edited wheat field trial gets go-ahead from UK government. Rothamsted Research. Available at https://www.rothamsted.ac.uk/news/genome-edited-wheat-field-trial-gets-go-ahead-uk-government


Genome edited wheat to reduce cancer risk from bread and toast. Rothamsted Research. Available at https://www.rothamsted.ac.uk/news/genome-edited-wheat-reduce-cancer-risk-bread-and-toast

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