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Context:

Scientists have developed an RNA-based antiviral that effectively combats the cucumber mosaic virus in plants.

Background

Farmers worldwide face a massive challenge from plant viruses, unlike bacteria or fungi, which farmers can control with chemicals like pesticides, no simple cure exists for viral infections in plants.

The United Nations’ Food and Agriculture Organization (FAO) reports that pests and diseases destroy 40% of global crops yearly, costing over $220 billion. Plant viruses alone cause losses of more than $30 billion annually. One such virus, the Cucumber Mosaic Virus (CMV), is a major threat.

Cucumber Mosaic Virus (CMV)

It infects over 1,200 plant species, including crops like cucumbers, pumpkins, bananas, cereals, and even medicinal plants.

In India, CMV causes 25-30% yield losses in banana plantations and up to 70% infection rates in pumpkins, cucumbers, and melons.

Infected plants show mosaic-like discoloration, stunted growth, and produce fruits that are not fit for sale.

It spreads through small insects called aphids, with nearly 90 aphid species capable of transmitting it, making outbreaks hard to control.

New Solution

Scientists at Martin Luther University Halle-Wittenberg in Germany have developed a new RNA-based antiviral to protect plants from CMV. RNA (Ribonucleic Acid) is a molecule that plays a key role in how living organisms, including plants, function. The researchers use RNA to strengthen a plant’s natural defense system, similar to how our immune system fights viruses.

Plants have a natural defense called RNA silencing. When a virus attacks, it introduces double-stranded RNA (dsRNA), which alerts the plant’s immune system.

• The plant produces Dicer-like enzymes (DCLs) that cut the dsRNA into small pieces called small interfering RNAs (siRNAs).
• These siRNAs act like guides, helping the plant identify and destroy the virus’s genetic material, stopping the infection.
• However, this natural defense isn’t always effective. The siRNAs plants produce may not target the virus well, and viruses can mutate quickly to escape.

To fix this, scientists developed two RNA-based techniques: Host-Induced Gene Silencing (HIGS) and Spray-Induced Gene Silencing (SIGS).

• HIGS: Scientists genetically modify plants to produce virus-fighting dsRNA inside their cells, giving lifelong protection. However, HIGS is expensive, faces strict regulations, and viruses can develop resistance.
• SIGS: Instead of modifying the plant’s DNA, scientists spray RNA molecules onto leaves. The plant absorbs the RNA, which triggers its immune system to fight the virus. SIGS is cheaper, eco-friendly, and doesn’t involve genetic modification, but traditional SIGS produces a mix of siRNAs, many of which are ineffective.

The German researchers improved SIGS by creating effective dsRNA, a specially designed RNA molecule packed with highly functional siRNAs. Unlike traditional dsRNA, which produces random siRNAs, effective dsRNA ensures the plant generates siRNAs that precisely target the CMV’s genetic material. This triggers a stronger and more targeted immune response.

In lab tests on a model plant, Nicotiana benthamiana, the effective dsRNA reduced the CMV viral load by nearly 80%, with some plants achieving complete protection. It worked better than traditional dsRNA because it produced more effective siRNAs. The method also proved effective against multiple CMV strains, making it versatile.

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Source: 

THE HINDU