A new approach to inoculate plants against viruses can be used as an alternative to toxic pesticides, which is harmful to insects as well as environment.
Scientists from the Martin Luther University in Halle-Wittenberg (MLU, Institute of Biochemistry & Biotechnology), the Leibniz Institute of Plant Biochemistry (IPB, Department of Molecular Signal Processing) and from the Italian National Research Council (CNR, Institute for Sustainable Plant Protection) presented their discoveries on "Nucleic Acids Research, Oxford Academic"
The approach, developed by a group from Martin Luther University Halle-Wittenberg (MLU) will help to rapidly detect and produce vaccines that can be tailored to fight 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 known as 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 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 a reputed Research journal.
In the laboratory, the team infected 2 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 percent 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 combating 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.
Letter combinations such as CMV, TYLCV, ToMV, ToMMV, TSWV terrorize tomato producers, as they represent the acronyms of some of the viruses that damage both greenhouse and open-field crops. Producers spend most of their money trying to control the spreading of viruses with pesticides and insects, but things might change in the near future.
NR virologist Vitantonio Pantaleo (in the photo) reveals that "during an infection, plant cells act as a multiplication tank of the virus genome, i.e. of the invader. Yet plants maintain the capability of detecting said invaders. Special enzyme scissors cut foreign viral molecules. This process produces a multitude of viral interfering RNAs (vsiRNA) which spread within the plant and associate with proteins of the Argonautes group (AGO). VsiRNA guide AGOs in a sequence-specific manner against the viral genome mediating degradation and deactivation."
"The virus-silencing mechanism is not always very effective in nature, as some vsiRNAs are truly very effective. Scientists have therefore developed a screening process based on vegetable cell extracts that enables the identification of the most efficient and effective vsiRNAs, called "efficient antiviral siRNAs (easiRNAs)".
Virus on tomatoes
MLU biochemist Sven Berhens stated that "selected easiRNAs have a better affinity with the AGOs. In addition, they can recognize the weaknesses of the viral genome better than the others. The effectiveness of easiRNAs was demonstrated vaccinating tobacco plants (Nicotiana benthamiana) infected by a model virus, the Tomato bushy stunt virus (TBSV). The result was surprising: after six weeks, 90% of vaccinated plants showed no sign of infection, while all those untreated were killed by the virus."
"If the virus changes, the screening method enables the quick identification of the suitable RNA molecules to fight the new invader. This means we can be very flexible when fighting the new parasites."
A patent application for the method has already been filed.
Vaccinating potential
"RNAs are natural molecules found in nature. Tomatoes that get to our tables fresh or preserved already contain such RNAs. If we consider that using RNA vaccines is potentially effective to control pathogen fungi and post-harvest harmful agents, we can see all of its great potential," added Pantaleo.
The research group will now continue to explore and improve the screening method to clarify the application method and persistence on treated plants. Further studies will demonstrate how larger quantities can be produced at sustainable costs. Plant absorbance modes and efficiency will also be studied.
"According to Behrens, these studies can help reduce the use of chemicals in agriculture to the benefit of the environment, consumers, producers and the entire food chain in compliance with the objectives of the UN Global Agenda for Sustainable Development."
