Wouldn’t it be great if we could easily make our crops resistant to diseases? Or if we could expect good yields even in a drought? What if we could use less pesticide and fertiliser, so that our farming practices cause less damage to the environment? Whilst this may all sound quite fanciful, these ideas and more are becoming real possibilities, thanks to a scientific approach called “genome editing”.

Genome editing refers to a set of techniques that have been developed in recent years to make small, precise changes to an organism’s DNA. They differ from traditional genetic modification (GM) approaches in that there is no foreign DNA introduced. Rather, they rely on tiny errors being introduced or corrected in the DNA code.

The most popular technique used at the moment is CRISPR-Cas9. The technology is based on a bacterial immune system that protects cells from invading viruses. The system has two components that are bound together: a guide RNA (gRNA) and a Cas9 nuclease. The gRNA is a molecule with a specially designed sequence that binds to a specific region in the genome. The Cas9 is an enzyme that cuts DNA, guided by the bound gRNA.  When the cell tries to repair this cut, it often does a bad job and mistakes get incorporated. This changes the genetic sequence and may cause the gene to stop working. Alternatively, a changed copy of the DNA sequence can be introduced alongside the CRISPR-Cas9, and the cell can use this as a template to repair the cut. This can be used to rectify harmful mutations.

Changing genes so that they don’t work (known as “knocking out”) may sound like something we’d want to avoid, but it can actually be pretty useful. It’s very important to the scientific community: switching a gene off is an important step towards understanding how it functions. It can also benefit the organism if the gene in question is harmful. For example, the Mlo genes make plants vulnerable to a fungal infection called downy mildew, but using CRISPR, scientists have knocked out some of these genes in tomato and wheat, to help protect the plants from the disease. By carefully selecting which genes are targeted, scientists can use this technique to alter lots of traits that affect plant yield, such as drought tolerance and plant height. The whole process is much quicker, easier and cheaper than breeding or classical GM, and this is why scientists are getting so excited about it.

The regulations surrounding genome editing vary between countries. The European Court of Justice (ECJ) ruled earlier this year that gene edited crops should be treated the same as those generated by classical GM, meaning that they are subject to strict regulation. The US Department of Agriculture, by contrast, is much more relaxed. When older GM methods are used, whole genes insert randomly into the genome and this means the effects can be unpredictable. The changes made by CRISPR, by contrast, are much smaller (mere tweaks) and highly precise. These sorts of changes could feasibly happen naturally, by mutation. Therefore the ECJ ruling frustrates many scientists, who argue that CRISPR’s precision makes it much safer than past GM. Also, the changes that CRISPR makes to DNA are even fewer and more controlled than those made by the methods used by breeders to generate random mutations – considered ‘safer’ by EU regulations. Because of this, Europeans may not reap the benefits of genome editing technology, whilst people elsewhere enjoy lower food prices.

Genome editing has been getting a lot of press lately, particularly surrounding the ethics of its use in humans. However, in plants, it has enormous potential to do a whole lot of good. Innovations in crop farming have a history of saving lives: during the “Green Revolution” of the mid-20th century, the work of the American agronomist Norman Borlaug is credited with saving millions of people from starvation. The genome editing revolution could have just as much, or even more, impact. With a rapidly growing global population and a changing climate, it could be the miracle that we need.