The cross : How to simply explain the Crispr-Cas9 technique, which earned French researcher Emmanuelle Charpentier co-winner of the Nobel Prize in Chemistry in 2020?

Jean-Luc Welsh: Originally, it is a natural defense system discovered in bacteria that allows them to cut the DNA of viruses to make them inactive. In 2012, two researchers, Emmanuelle Charpentier and the American Jennifer Doudna, had the idea of ​​using this biological means of defense to make it a tool to modify the genome – the support of hereditary characteristics – of any organization.

The process consists of introducing a “guide RNA” into the cell, which targets a DNA sequence, associated with a Cas9 protein, which operates like molecular scissors at this precise location in the genome. When the cell’s repair system “glues” the two ends back together, the cut gene is rendered inactive. New versions of this system make it possible not to inactivate a gene but only to change a base – a letter – of the targeted gene.

What benefits can we expect from this technology?

J.-LG: In nature, all living organisms experience random mutations in their genome. It is a mechanism at the base of the evolution of species. Crispr-Cas9 technology makes it possible to mimic this process. For a plant, we can thus modify a gene in a precise way to give it the favorable character – resistance, quality, etc. – that we want to introduce.

The traditional selection method consists of looking for traits of interest in the natural variability of plants to introduce them by crossing into the plant to be improved. Which can be long. The genome editing method makes it possible to go faster by directly copying an identified mutation in the species to be improved.

What are the concrete applications?

J.-LG: In our plant genetic improvement station in Avignon, we work in particular on disease resistance. The mutations in peppers that have enabled these plants to resist certain viruses are well known. One of our research projects involves copying these mutations into a tomato or potato gene with the aim of generating the same resistances. We can thus hope to reduce the use of pesticides.

In Japan, a tomato variety developed using Crispr-Cas9 technology, which expresses compounds beneficial to health, has been commercialized. Other laboratories are exploring the possibility of modifying, through genetics, the root architecture of plants to enable them to establish themselves deeper in the soil and thus better resist drought.

This genome editing technology also raises concerns. Do you think they are justified?

J.-LG: Like all technologies, the use of Crispr-Cas9 needs to be supervised and controlled. We must ensure that we have targeted the part of the genome that we wanted to modify and not another. It will be up to the new European directive expected for 2023 to say how new genome editing techniques should be regulated.

“Crispr-Cas9 technology allows precise modification of a gene in a plant”