Viruses evolve to defeat CRISPR-Cas9 in genetically modified plants

The researchers found that viral pathogens can evolve rapidly to overcome transgenic cbadava plants expressing the CRISPR-Cas9 bacterial weapon, which could have major regulatory implications.

Geminiviruses are pathogens that destroy crops such as beans, cotton and cbadava. Efforts made in the past to create resistant plants have not been successful.

One potential way to make plants resistant is to give them the CRISPR-Cas9 genes, a DNA cutting weapon that has allowed bacteria to grow to fight viral infections. This particular use is very specific to the manufacture of virus-resistant organisms and is not related to the use of CRISPR-Cas9 as a genome editing tool.

A team of scientists in Switzerland, the United States and Belgium used a bacterium to transmit CRISPR-Cas9 genes to cbadava plants. The team aimed to make the plants resistant to infection by a geminivirus called African cbadava mosaic virus. Unfortunately, the researchers found that the CRISPR-Cas9 genes did not work efficiently enough to fight the viral infection. They also found that the virus was mutating to become resistant to the CRISPR-Cas9 genes, which could make these viruses even more difficult to fight in the future.

"It was not completely unexpected,"Said Hervé Vanderschuren, senior researcher at the University of Liège, Belgium. "If you select plants that are naturally resistant to viruses, you will notice the emergence of viruses that can bypbad this resistance."

Posted in Genome biology, the discovery of these resistant viruses reveals a major risk of transmission of CRISPR-Cas9 genes to the cultivated plants. The researchers suggested that regulators, already rigorous enough the EU with regard to genetic engineering, should consider this risk carefully in the future.

"CRISPR-Cas is the subject of hype and has enormous potential in agriculture and human health,Vanderschuren said. "But it is also important to share the boundaries."

With some modifications to the CRISPR system, Vanderschuren believes his research team may be able to make the plant's viral defenses more effective and overcome viral resistance to CRISPR systems.

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