Inspired by viruses, researchers at Iowa State find new means of protecting plants from aphids

AMES, Iowa – A pair of researchers at Iowa State University drew inspiration from viruses in designing a new way to allow plants to protect themselves from aphids, pests that can drastically reduce crop yields.

Aphids are tiny insects that can devastate nearly any crop grown in a temperate climate, said Bryony Bonning, professor of entomology. So finding a targeted method to deal with the pests would benefit farmers around the globe.

To that end, Bonning and Allen Miller, professor of plant pathology and microbiology, have discovered a way to genetically engineer a model plant to produce a toxic protein in its sap that interacts with aphids the same way certain plant viruses do. The result is a plant with a defense mechanism that fends off aphids without the use of pesticides, a development that could make farming less costly and improve the environment.

“We looked at how the plant virus works, how it is ingested by the aphid and transported whole into the aphid’s bloodstream without being digested, and used that against the aphid,” Miller said. “We end up with what should be an environmentally benign method for controlling aphids.”

Ordinarily, it’s the aphids that transmit the virus to the plants, which can make aphid infestations even more devastating. Bonning and Miller have devised a way to turn the tables by fusing a toxic peptide with the viral coat protein, which allows the toxin to be taken into the aphid’s bloodstream similar to the way a virus is. Once in the bloodstream, it fatally paralyzes the aphid.

The model plant Arabidopsis was chosen for the study, which was published this week in the journal Nature Biotechnology, because of the ease with which it can be genetically engineered, but Bonning and Miller said it should be possible to use the same technique in plants like soybeans.

“Having demonstrated that this works in Arabidopsis, there’s no reason to believe it won’t work in crops,” Bonning said.

But, she cautioned, it would take about a decade of further study and testing to commercialize the technology.

One challenge is making sure the toxin is harmful only to aphids. The toxin has already been shown to be harmless to mammals, and the fusion uses only the viral coat protein, meaning there’s no risk of toxicity to humans or viral infection of the plant.

Showing that the toxin affects only aphids would give it an important leg up on pesticides, which are far less selective in the insects they kill. Farmers have grown increasingly reliant on pesticides to deal with soybean aphids since the insects first invaded the Midwest in 2000, driving up input costs for farmers while threatening beneficial insects such as pollinators, Miller said.

“Current pesticides are indiscriminate in the insects they kill, while we think this solution allows us to be much more precise because only aphids transmit the virus,” Miller said.

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