PNAS: RNAi-based pesticides aim to get around resistance problems

Excerpted from PNAS, Dec. 9, 2020, by Leah Shaffer. Full article:

First identified in 1990, RNA interference (RNAi) entails using double-stranded RNA (dsRNA) to block messenger RNA from its usual function (i.e., sending out instructions to make proteins). With impressive specificity, RNAi can potentially block nucleotide sequences that are only found in a target pest and not in friendly insects or humans. As a result, some scientists are keen on making RNAi the next big tool in agricultural science.

With RNAi pesticides, biochemists can manufacture dsRNA that will silence the nucleotide sequence responsible for making proteins crucial to the development of one particular insect.   Bruce Tabashnik, professor of entomology at University of Arizona, has explored using RNAi to silence the production of proteins used to synthesize or transport juvenile hormones, something unique to a particular species of insect. Using RNAi as opposed to conventional pesticides is the difference between taking a hammer to a whole row of bugs versus using tweezers to cripple part of one particular insect.

Scientists can use the tools of genomics to examine nucleotide sequence variants between different insects, notes Brad Fabbri, chief science officer at TechAccel, a Kansas City-based private equity biotech firm investing in RNAi technology. “You should be able to design something that has a high degree of specificity,” says Fabbri.

One of the main ways to make dsRNA is to genetically modify a bacterium to produce it. Companies such as TechAccel use genetically modified microorganism to make dsRNA. And it’s becoming increasingly affordable to do so. Just four years ago, production of dsRNA could cost as much as $1,000 per gram, estimates Fabbri. That’s an economic nonstarter. But their system of using vats of microorganisms to spew out dsRNA has allowed them to lower that price to just under a dollar per gram. “Once you get that active ingredient cheap enough, it really opens up the door,” he says. It’s still early days, as their products are at least a few years away from starting the regulatory process. But he’s hopeful for the environmental and food production benefits that could emerge.


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