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Attempting to create virus-resistant crops can be dangerous: researchers at U of A

In this photo taken Tuesday, October 2, 2012. Richardson Okechukwu, a scientist who studies cassava, inspects plants at the International Institutes of Tropical Agriculture in Ibadan, Nigeria.

Domingo Alamba / AP

The use of gene-editing technology to create virus-resistant cassava plants can have dangerous consequences, warn researchers at the University of Alberta.

About three years ago, Devang Mehta, a postdoctoral fellow at the Department of Biological Sciences, started a study as a doctoral student in Switzerland on the creation of virus-resistant cassava plants.

The goal of the research was to make the starch root vegetable resistant to the devastating mosaic disease, which results in about 20% crop loss per year.

But during the study, researchers at the University of Liège in Belgium and the Swiss Federal Institute of Technology found that the virus was mutating and becoming resistant.

"We concluded that as this technology creates selective pressure for viruses to evolve faster and also provides viruses with a means to evolve, this has resulted in a mutant virus resistant to our interventions," Mehta said.

He added that the cassava plant is different because it does not require a seed to be replanted. Instead, a piece of the stem of the plant is cut to grow new crops, a staple grown in South America, Africa and Asia.

"The difference here is usually when a plant goes to seed, the viruses that were in that plant usually do not transmit to the next generation. While in the case of cassava because it does not involve a seed to reproduce, there is such potential that the virus can be transported across generations of crops, "said Mehta.

The researchers used the new gene-editing technology – CRISPR-Cas9 – to try to change the DNA of the mosaic virus in order to prevent the spread of the disease in the cassava plant.

CRISPR-Cas9 is essentially composed of two genes, CRISPR one and Cas9 another. CRISPR-Cas9 is prevalent in many natural bacteria, which use the system to defend against viruses.

The researchers concluded that gene-editing technology is appropriate for many different applications in which genome editing of a plant or animal is involved. But when it comes to editing the genome of a virus, there is a new set of features to consider, some of them dangerous.

"We found that the pressure that CRISPR-Cas9 applied to the virus probably encouraged it to evolve in a way that increased resistance to intervention," Mehta said, noting that his research team is willing to share the results with other scientists using the technology. design virus-resistant plants so they can quickly detect any similar viral mutations.

The article, "Linking CRISPR-Cas9 interference in cassava to the evolution of edible geminiviruses," is published in Genome Biology (doi: 10.1186 / s13059-019-1678-3).

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