Scientists say the technology could be used one day to increase yields through drought and pest resistance, and improve nutrient profiles.
by Melita Brainta
The United States Department of Agriculture (USDA) has been toying with the greatest and most recent DNA manipulation technologies for a few years now. But on 28 March 2018, the agency has made it official that certain gene-edited plants can be designed, cultivated, and sold free from stern and lengthy regulations that are traditionally imposed on foods produced using any kind of biotechnology, such as genetically modified organisms (GMOs).1,2 This means that gene-edited foods made using CRISPR (also called CRISPR-Cas9) get the green light and is now one step closer to our dinner plates, while traditional GMOs stay in the red.
GMOs VS CRISPR
Gene modification involves the insertion of a chunk of DNA from other organisms such as bacteria into the genome of the crop, meaning that its final product can ultimately be identified as genetically modified (GM).
In contrast, genome editing deals solely with the alteration of genes that already exist within the crop. This process closely mimics nature in that a random mutation could technically have caused the same result.3 It is also more precise in comparison to conventional crop breeding methods or standard genetic engineering (transgenic or GM) methods, as researchers can make a meticulous edit right down to a single DNA base from the genome of the crop. The more precise the technique, the less of the genetic material is altered, and ultimately the uncertainty about other effects on how the plant behaves is also lowered.4
In order to make a CRISPR crop, scientists can either replace one of the billions of nucleotides (the building blocks of genes) present in the crop's genome or delete short segments. “Changing a G to an A is very different from bringing a gene from a bacterium into a plant,” Harvard geneticist George Church told Business Insider.5 The final products produced using CRISPR will be indistinguishable from those made using old-school plant breeding.
Coming soon to a store near you
If all this sounds unrealistically futuristic, think again! Gene-edited foods could be in grocery stores sooner than you expect. Two of the CRISPR gene-edited foods that are expected to be on sale soon are anti-browning mushrooms and reduced-gluten wheat.6
CRISPR-Cas9 technology was used by scientists from Penn State University to create small deletions in a specific gene encoding an enzyme known as polyphenol oxidase (PPO). This enzyme is responsible for causing white mushrooms to brown as it catalyses the oxidation of polyphenols in the mushroom when they are exposed to air, the first step in the generation of dark melanin pigments. “The small deletions knockout the gene and prevent the synthesis of the PPO, leading to a reduction of overall PPO activity by more than 30 percent,” says Yinong Yang from Penn State University. A bacterial plasmid construct was used to deliver the guider RNA and Cas9 enzyme into mushroom cells and accomplish the necessary deletions. Since the final product does not carry any DNA from a vector or donor organism, it is not covered by current rules that regulate the movement, import or release of GMOs in the US7 and thus the mushroom has been cleared by USDA for commercial cultivation.
CRISPR-Cas9 has also been utilised by researchers at the Institute for Sustainable Agriculture in Cordoba, Spain to reduce most of the gliadins, the gluten proteins that cause the majority of the gluten intolerance issues for people with celiac disease, in wheat. “There are many gliadin genes in the grain of wheat, which makes it impossible to obtain gliadin-free wheat lines using classic breeding methods. Gene editing by CRISPR/Cas allow the introduction of mutations in specific genes, and shutting down [of] those genes. In this work, we were able to mutate 35 out of 45 gliadin genes in bread wheat, and reduce wheat toxicity up to 85 percent. This is an unprecedented application of CRISPR/Cas technology. The low-gluten, transgene-free wheat lines described in the work constitute an unprecedented advance, and the resultant lines provide excellent source material for plant breeding programs to introgress the low-gluten trait into elite wheat varieties,” Dr Francisco Barro Losada, the geneticist whose team carried out the research, told Digital Trends.
Unfortunately, the resulting wheat is still not suitable for celiac disease patients as it still contains a small amount of gluten. The team is currently working to disable the remaining 10 genes to ensure that no gliadin proteins are produced.8
How it will help solve the world’s looming food crisis
Irregular rainfall and increasing temperatures are making food production more difficult. Crops narrowly survive a drought, only to be drowned in heavy rainfalls months later. Global warming is also increasing the dissemination of plant infections and diseases that thrive in hot, damp conditions.9
CRISPR hold the answer to feeding our rapidly growing population because by allowing scientists to produce plants that are resistant to drought, disease, pest, poor soils, and increased temperatures, it could in theory help boost crop yields despite the obstacles of climate change. It could also longer the shelf life of products, reducing food waste from spoilage.10
CRISPR-Cas9 gene editing technology is also a way to produce nutritionally enhanced food crops, namely broccoli. “Lycopene and glucosinolates in broccoli can reduce chronic disease or slow disease such as cancer. Sulforaphane is a glucosinolate in broccoli, and most of us know that when we cook broccoli, we lose the nutrients. So, gene editing can actually help us solve that problem and extend the nutrient to the cooked vegetable,” said Corinne Marshall, intellectual property and licensing manager for Sakata Seed America Inc.11
Melita Brainta is currently a student majoring in Food and Nutritional Sciences at the Chinese University of Hong Kong.