TECHNOLOGY

The next big thing for RNA? Identify moldy foods


among all fungi there, Botrytis cinerea It is he who keeps farmers awake at night. Scaly fungi have an insatiable appetite. They will happily chew on hundreds of plant species – although soft fruits like grapes are a favorite – covering everything they feed on with a velvety layer of mold. If you’ve ever left a tub of strawberries in the fridge for too long and they come back to find them looking kind of gray-green, there’s a good chance that one of the strawberry spores is always present. Botrytis Floating in the air he decided to make his forever home in your candy.

Rotten candy is a pain, sure, but for the food industry Botrytis It poses a big problem. This is the only type of fungus that is responsible, at least $10 billion in damages crops every year. Some estimates put the figure as high as $100 billion. It is so troublesome that a survey of plant pathologists classified it as second most important The fungal pathogen of plants, in what can only be described as the equivalent of their industry time List of the magazine’s “Most Influential People”. (Fore went to Magnaporthe oryzae: A fungus is destroying rice fields around the world.)

says Mark Singleton, head of plant and animal health at GreenLight Biosciences, a Massachusetts-based biotech startup that is working on a new generation of sprays to defend against Botrytis And other pests that bother farmers. The negative effects of existing fungicides and pesticides are well known: spray residues can accumulate in the environment and harm non-target organisms, while their excessive use can lead to the development of resistance to pests and weeds. Singleton is working on finding a way around these problems. Its starting point is RNA: a molecule similar to DNA that is one of the building blocks of life.

This new generation of pesticides is based on a cellular trick dating back over a billion years, at least as far as Last common ancestor Of animals, plants, fungi and demonstrators. At some point – we’re not sure exactly when – cells developed the ability to shred and destroy genetic material from invading pathogens, such as viruses. When a cell detects double-stranded RNA (dsRNA) — a stretch of genetic code that viruses use to replicate themselves — it breaks that RNA into tiny pieces. These bits of dsRNA look like tiny desirable labels. Molecules in the cell pick them up and use them to track down any identical stretches of messenger RNA (mRNA) – which molecular cells use to convert genetic instructions into proteins. If the molecular bad guys are chopped up before they can begin to turn into proteins, the cell will have escaped a successful invasion.

The discovery of this process – called RNA interference (RNAi) – gained two scientists in 2006 Nobel Prize in Physiology or Medicine. It also ignited a race to develop new tools based on it. Scientists soon realized that if you could introduce dsRNA into an irritating pathogen — a particularly annoying mushroom, for example — you could direct that pathogen’s cells to destroy their messenger RNA and prevent them from making essential proteins. In essence, they can turn off genes within pathogens at will. “We just go in there and look at the gene and protein orchestra there and silence the violin. That’s all we do,” says Michael Helmstetter, president of RNAissance Ag, another startup competing to bring RNA crop sprays to market.

A handful of RNA sprinklers are already in the works. RNAissance Ag works on a spray that targets the Diamondback moth, which has an insatiable appetite for cabbage and has Some resistance has already developed for common pesticides. GreenLight Biosciences has an RNA spray targeting the Colorado potato beetle that is currently being evaluated by the Environmental Protection Agency. The company expects to make a decision on this spray by mid-2022. It is also working on spraying Botrytis, In addition to those that fight Varroa miteIt is a common pest infecting honey bees. After initial lab trials, GreenLight is now field-testing a spray of Botrytis on grapes in California and strawberries in Italy. Singleton says they’re looking to see how long the spray sticks to plants and how it compares to chemical fungicides.

Crop RNA spraying could have some major advantages over the current toolkit of chemical pesticides. Microbes degrade RNA in the soil within two days, reducing the problem of environmental accumulation. Because RNA spray targets species-specific genes, there is – at least in theory – much less chance of other organisms getting caught in the crossfire. Even two very similar species have enough genetic differences to make it possible to make RNA sprays that target one insect while leaving the other alone, says Clauvis NT Taning, a postdoctoral researcher who studies RNAi pesticides at Ghent University in Belgium.



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