New ‘Medicine’ Could Vaccinate Plants Against Devastating Viruses

Few terms bode fear in a pumpkin farmer than CMV  viz. cucumber mosaic virus, a pathogen that spoils entire fields of pumpkins, cucumbers, and melons. Now, researchers have discovered a novel way to quickly develop vaccines that could in due course protect crops from viral pathogens.

“This is a really neat finding,” says Anna Whitfield, a plant pathologist at North Carolina State University in Raleigh who was not involved in the study.

Viruses are an ever-evolving constant threat to global food security, and according to Whitfield, the new technique might help farmers keep up with the constantly changing pathogens.

When a virus infects a cell in a plant, it typically releases RNA, in the form of either messenger RNA or double-stranded RNA, which runs through the cell, helping the virus replicate. Defense proteins residing in the plant cell recognize these viral RNAs, and its tiny scissors-like enzymes slice them apart. Small interfering RNAs (siRNAs), few resulting bits and pieces of RNA, team up with protein group called the Argonaute complex. The siRNAs serve as identifiers and lead the Argonaute complex to RNA on the virus genome, which is then destroyed by the Argonaute complex and other proteins.

Unfortunately, this deadly tactic is not always efficient. Out the several thousands of various siRNAs made by the plant, very few comprise the right chemical properties to fight the viral RNA. Biochemist Sven-Erik Behrens at Martin Luther University Halle-Wittenberg in Germany and his colleagues took the initiative to streamline the process. They conducted molecular tests to identify which siRNAs are efficient at fighting viruses. In laboratory experiments with tobacco plants, they found that they could select the winners and channel them as a vaccine against the tomato bushy stunt virus. This slowed growth and damaged leaves in tobacco plants. The best siRNA, when sprayed on the leaves, protected 90% of the plants, the team reported in this month’s journal Nucleic Acids Research.

Behrens shared that there are other methods of predicting which siRNAs might be effective against a plant virus, but most computer models that may not always work as expected

Whitfield described the most exciting outcome of the study was the fact that the team got results by simply spraying the siRNAs on the plant or rubbing them onto the leaves. This process is considerably simpler and faster than genetically engineering a plant for viral resistance, allowing scientists and farmers to continue with the quick evolution of viral pathogens with ease.

The thrilled researchers are now focusing on finding the most efficient and cost-effective way of administering the vaccine to plants like a spray that uses nanoparticles to deliver the siRNAs. They’re also attempting to identify siRNAs that would economically fight important viruses such as CMV or the zucchini yellow mosaic virus, on plants from melons to tomatoes.

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