Europe remains apprehensive about using genetically modified organisms in agriculture and has strict laws against GMOs, which is why researchers have started working on various ways to use genetic techniques without altering plant genomes in order to overcome the stigma of GMOs. The Biotechnical Faculty at the University of Ljubljana has joined one such research effort.

Spray Induced Gene Silencing (SIGS) technology is a way to add RNA molecules to sprays, replacing the chemicals currently used to exterminate pests.

"These molecules stop or decelerate the expression of target genes in pests, which consequently kills them or inhibits their development and ability to infect the host plant," explains Taja Jeseničnik, a researcher at the Biotechnical Faculty who works on the application of genetic methods to agriculturally important plants.

The main difference between SIGS and traditional GMOs is that by using sprays, the genome of plants and pests is not changed, only its expression is controlled. "The RNA molecules are very unstable and disintegrate inside cells, so integration into the genome is not possible," says Jeseničnik.

Because they are unstable, RNA molecules are very environmentally friendly. And unlike synthetic chemical compounds, they do not last but disintegrate relatively quickly. As a result, it is highly unlikely that they would find their way into food.

SIGS also makes it possible to very precisely target specific pests. "The RNA molecule, which is the active ingredient in sprays, is specific to one target gene that we choose," explains Jeseničnik. "This is why targets need to be selected well, so that the chosen gene harms the adverse organism not other, beneficial organisms."

Researchers would like to design sprays that contain several RNA molecules targeting multiple genes. This reduces the probability of mutations and development of resistance, since simultaneous mutations on several target points are unlikely. Moreover, having a larger number of targets means that the spray can be used on several pests.

Long path to application in farming

SIGS studies are still in the early stages. There is only one such product on the market as of recently, in the United States. But scientists all over the world are currently actively looking for potential target genes in pests to develop fungicides, insecticides, and herbicides.

Researchers from the Biotechnical Faculty are focusing on hops pests and are working together with a laboratory in Spain and the Slovenian Institute of Hop Research and Brewing in Žalec.

At the moment, the path to market is hamstrung by price, since the production of RNA molecules remains very expensive. This is why development efforts must not focus only on molecules and their effects, but also on a faster and cheaper production of these molecules on a larger scale.

Until the new RNA sprays become cheap enough, the plant genome modification techniques used in pest protection that were discovered in the mid 1980s will probably continue to evolve. This involves inserting selected genes directly into the plant to produce plants with the desired traits faster, without time-consuming and expensive selective breeding.

There are many different approaches to inserting genes into plants that are much faster than selective breeding, but they are still not as simple as they might seem, says Jernej Jakše, a professor at the Biotechnical Faculty.

With monocot plants, the technique most often used is the gene gun, which involves cell nuclei being bombarded at high speeds with DNA particles. "With dicot plants, there is a specific bacterium which subdues the plants by inserting its genes into their cells and can be used in a laboratory to insert the desired genes."

One or several genes are inserted, which is a tiny percentage of the 32,000 genes that for example corn has. This results in a modification of traits that is similar to the results of selective breeding but much faster, added Jakše.

One of the most successful examples of GMOs is soybeans, with three quarters of the world production being genetically modified. The case of soybeans, which have been on the market since 1996, proves that there are no harmful effects of GMOs on people's health," says Jakše.

Despite that, there is a lot of resistance to GMOs in society, which is reflected in European legislation. The EU has one of the strictest GMO regulations in the world, due to which GMOs today are used almost exclusively for animal feed. RNA sprays could be a good alternative solution.