Researchers develop pesticide alternative to protect plants form viral infection 

New screening process can detect efficient molecules that can help kill virus

By DTE Staff
Published: Thursday 22 August 2019

A novel approach to vaccinate plants against viruses can be used as an alternative to toxic pesticides that is harmful both to insects and the environment, according to a study.

The approach, developed by a team from Martin Luther University Halle-Wittenberg (MLU), helps to rapidly detect and produce vaccines that can be tailored to combat different pathogens in plants.

During a virus attack, plants initiate a two-stage molecular defence programme which protects them “both at the site of the infection and throughout its structure”.

The programme first triggers plants’ cells to multiply the virus, which creates viral ribonucleic acid molecules (RNAs). Using special enzyme scissors, the plants then detect these molecules and cuts them — a process which produces ‘small interfering RNAs’ (siRNAs).

The siRNAs spreads throughout the plant and attach themselves to a protein called Argonaute. The siRNAs then leads the protein to RNAs viruses to kill them.

However, only a few siRNA molecules have this a protective effect, said Sven-Erik Behrens, from MLU's Institute of Biochemistry and Biotechnology.

“The majority simply saturate the Argonaute complexes, rendering them inactive,” he explained.

The researchers developed a screening process that could detect siRNA molecules that bind strongly to the Argonaute and also leads the protein to viral RNAs’ sites to kill them. Molecules with these properties then qualify as potential vaccines, according to the study described in the journal Nucleic Acids Research

In the laboratory, the team infected two groups of tobacco plant N benthamiana with a model virus that attacks tomatoes and tobacco.

One group was vaccinated with the highly efficient siRNA molecules, while the other did not receive any treatment.

After six weeks, 90 per cent of the vaccinated plants did not show any signs of infection, but all the untreated plants were killed by the virus, the researchers found.

“If the pathogen changes or the plant needs to be protected against another virus, the established screening process enables suitable RNA molecules to fight the respective pathogen to be identified very quickly,” Behrens said.

“This means we can be very flexible when it comes to combatting new pests,” Behrens said. He added that it is unclear how long a vaccination will last.

The team wants to further explore how to produce the vaccines in larger quantities and to understand how these can be applied or absorbed by plants.

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