Sprayable ‘origami’ RNA biopesticide shows promise for controlling caterpillar pests

An RNA-based biopesticide that folds into microscopic, three-dimensional shapes could help farmers control damaging caterpillar pests using a simple spray application, according to research from scientists in China.

The technology uses self-folding RNA structures — described as “RNA origami” — to deliver gene-silencing molecules directly into pests such as the beet armyworm (Spodoptera exigua), a globally important crop pest.

Early laboratory trials suggest the approach improves the stability and effectiveness of RNA spray products, which have struggled to work against many caterpillar species.

Researchers at the East China University of Science and Technology say the technique could open the door to more practical RNA-based crop protection tools that target pests precisely while reducing reliance on conventional chemical pesticides.

A new way to deliver RNA sprays

RNA interference (RNAi) is a biological process that can switch off specific genes. Scientists can exploit it by designing RNA molecules that disrupt genes essential for pest survival or development.

Despite the technology’s potential, in practice it has struggled. RNA molecules degrade quickly in the environment and often fail to enter pest cells, particularly in Lepidoptera — the insect group that includes moth and butterfly larvae responsible for many major crop pests.

Previous attempts to improve performance have relied on nanoparticles or other carriers to protect the RNA and deliver it into pests. However, these systems can be complex to manufacture and raise environmental concerns.

The new approach attempts to solve the problem by redesigning the RNA molecule itself. Instead of remaining as a linear strand, the RNA folds into a tiny four-sided nanostructure using a self-assembly technique known as RNA origami, or T-RiOB.

In research published on open research platform SSRN, the scientists said the 3-D structures improve stability, allowing RNA molecules to enter pest cells without needing additional carriers.

Better leaf coverage and plant uptake

Tests using cabbage leaves showed that the folded RNA structure improved spray behaviour compared with standard RNA solutions. The droplets spread more easily across the leaf surface, suggesting more of the product would remain on the plant after spraying. The researchers also tested how well plants absorbed the molecules.

Experiments on tobacco relatives (Nicotiana benthamiana) showed that the folded RNA entered leaves more effectively than conventional RNA sprays. Root tests using Arabidopsis thaliana, a small plant commonly used in laboratory studies, showed uptake levels around five times higher with the RNA origami structure.

This suggests the folded RNA molecules may move into plant tissues more easily, increasing the chance that feeding pests will ingest them, the researchers said.

Penetrating the insect gut

A major obstacle for RNA biopesticides is getting the molecules through the insect gut wall and into cells where gene silencing occurs.

In laboratory tests, the RNA origami structures were taken up much more readily by insect cells and larvae than standard RNA molecules. Using fluorescent markers, the researchers tracked the particles inside insects and found they accumulated in both the gut and body tissues.
Standard RNA molecules showed little uptake by comparison.

Once inside, the RNA molecules activated the insect RNAi pathway, the system responsible for shutting down targeted genes.

Targeting a key insect gene

To test pest control performance, the researchers designed RNA sequences targeted a gene in beet armyworm that is essential for normal gut function.

In feeding trials, caterpillars were given leaves treated with different RNA sprays for seven days. The most effective RNA origami treatment caused around 45% larval mortality, while treatments using conventional RNA structures produced mortality rates below 15%.

Further analysis showed the treatment reduced activity of the target gene by about 30%, confirming that the gene-silencing mechanism was working. Larvae exposed to the treatment were also smaller and developed more slowly than untreated insects.

While further research is needed, the researchers say the approach could help make RNA-based crop protection sprays more practical and effective for controlling insect pests.

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