GMO vs. gene editing for plants: a closer look

Date:11-20-2018

By Brad Fabbri, Chief Science Officer, TechAccel

It’s easy to look at the vast array of upscale restaurants and groceries touting non-GMO (genetically modified organism) offerings and conclude that it is hazardous for your health to consume genetically modified organisms. The anti-GMO movement has effectively stoked fear and apprehension, often invoking discredited ‘scientific’ rationale and being guided by a ‘precautionary principle’ that even if there is no credible scientific reason for avoiding GMO foods, they should still be avoided because there might be a downside identified sometime in the future. This well-organized and -funded anti-GMO movement has effectively drowned out the arguments in favor of GMO including the significant overall improvements for agriculture sustainability.

Some in the anti-GMO movement argue there is a need for more scrutiny and regulation of certain breeding techniques including gene editing. The European Union, with its recent ruling that gene edited crops are to be treated like GMOs with respect to regulation, sows even greater confusion.

This EU ruling calls plants created using CRISPR and other gene-editing tools the same as genetically modified organisms and subject to the same stringent regulations. But the ruling also nods to an exception, allowing that plants developed using conventional mutagenic techniques with a long safety record are exempt.

The head-scratching nature of the ruling cries out for an understanding of the science involved. So, what is gene editing? And is it different from transgenesis or GMO crops? How can gene edited crops be regulated if they are indistinguishable from crops developed by traditional plant breeding?

There is a distinction between gene editing and creating genetically modified organisms. Understanding this distinction is crucial to making choices that are good for consumers and investors and for the future of the global food supply. It starts with a better understanding of mutagenesis.

Mutagenesis as Historic Means of Identifying Improved Plant Varieties

The fact is: We—humans—have consumed genetically modified foods as long as we have been eating plants.

Spontaneous mutagenesis—a change, or mutation, in DNA—happens naturally all the time. It occurs due to natural radiation such as ultraviolet or cosmic rays, chemical reactions, or errors in DNA replication. When this chemical change to the DNA occurs in a part of the genome that encodes something important for the plant, the change is often deleterious. But sometimes, the change is beneficial, and the resulting mutant plant is better than its parents.

Humans have been selecting improved mutant plants for at least 9,000 years. Modern crops including corn, watermelon, and peaches are radically different from their wild forebearers, a result of the long history of plant breeding where humans have selected for desirable qualities. Early farmers would select crop lines with advantageous mutations such as bigger grain, tastier fruit, or other desirable properties (like, a large gourd size with utility as a container). And season to season, seed from the best plants was saved and re-planted. Farmers were always looking for good seed, just as they do today. Over many generations of cross-breeding farmers have created genetic improvements and stronger, better-yielding crops. In essence, farmers have been genetically modifying crops for thousands of years—at least via selection of mutants and careful crossing of different varieties.

These traditional means are still in use today. In addition, over the last 90 years or so, plant breeders have employed new methods to increase efficiency for generating mutations with the goal of selecting improved varieties. Starting around 1930, various types of radiation including X-rays, gamma rays, ultraviolet and neutrons have been used to ‘mutagenize’ plant populations to generate high frequencies of induced plant mutants that the breeder can select from. Starting in the 1940s, mustard gas and similar compounds were used as another means of generating mutants. And even today, chemicals such as ethylmethane sulphonate (EMS) and similar compounds are commonly used to generate mutant plant populations. And these methods have been useful – a highly cited article published in 2004 estimated at the time that more than 2,250 plant varieties derived from mutagenized populations had been released.

A critical aspect of ‘spontaneous’ or ‘induced’ plant mutation is that the process of mutagenesis is random. Now, there are methods of introducing variation into plants that are not random and are highly planned.

These are the sophisticated gene-editing tools like CRISPR/Cas9, homing endonucleases (‘meganucleases’), oligonucleotide-directed mutagenesis, and zinc-finger nucleases that all can be used to generate mutations that are indistinguishable from those identified from spontaneous or induced populations.

Directing Desirable Mutations

We are experiencing rapid strides in genomic sequencing and analysis technologies, with prices dramatically dropping, and capabilities markedly increasing each year. This means that plant scientists and breeders can identify key desirable mutations, and these new gene editing tools can make the precise edits in a plant variety. This is a big advantage for time and resources over the traditional plant breeding steps required to develop mutant varieties and combine multiple desirable mutations into the same plant variety. There is significant interest in using this technology for improvement of plants, and companies including Calyxt, Precision Biosciences, and Pairwise are all focused on developing and delivering improved plant varieties using genome editing.

While each of these tools has a different mechanism, the change itself is in principle indistinguishable from a spontaneous, natural mutation. In the final product, no trace of a foreign substance remains, and the genome of the edited organism is essentially the same as that which came before.