The Next Big Thing for RNA? Fixing Moldy Food

In all that fungus there, Botrytis cinerea is what keeps farmers at night. The scuzzy fungus has a strong appetite. It happily feeds on hundreds of plant species — although soft fruits like grapes are its favorites — everything it eats is covered with a velvety layer of mold. If you leave a tub of strawberries in the refrigerator for quite some time and come back to find it a kind of gray-green, there’s a good chance it’s one of the frequent spores in the Botrytis floating in the air decided to make his eternal home of your dessert.

A spoiled dessert is a disease, sure, but for the food industry Botrytis presents a major problem. That one type of fungus is responsible at least $ 10 billion in damage of crops each year. Other estimates put the number as high as $ 100 billion. It is so disturbing that a survey of plant pathologists ranked it as second most important plant fungal pathogen, in what only described their industry equivalent to PERIOD on the magazine’s “Most Influential People” list. (The highest place went to Magnaporthe oryzae: a fungus that destroys rice fields around the world.)

“It’s huge,” said Mark Singleton, head of plant and animal health at GreenLight Biosciences, a Massachusetts-based biotech startup working on a new generation of sprays to protect against Botrytis and other pests that harm farmers. Disadvantages of existing fungicides and pesticides are known: Residues from sprays can build up in the environment and harm non-target organisms, while excessive use of them can lead to pests and weeds. changing resistance. Singleton is working on a way to solve these problems. And his starting point is RNA: a DNA -like molecule that is one of the basic building blocks of life.

This new generation of pesticides is based on a cellular trick that began more than a billion years ago, at least until last common ancestor of animals, plants, fungi, and protists. At one point — we’re not sure when — the cells ’ability to cut down and destroy genetic material from invading pathogens, such as viruses, will change. When a cell detects the presence of double-stranded RNA (dsRNA) —a part of the genetic code used by viruses to duplicate themselves — it will hack this dsRNA into smaller pieces. These dsRNA fragments are like little like posters. Cell molecules extract it and use it to find any corresponding component of messenger RNA (mRNA) —the molecules that cells use to make proteins follow the genetic instructions. If the molecules of bad people are broken down before they start making proteins, the cell will go on a successful invasion.

The discovery of this process — called RNA interference (RNAi) —captured two scientists in 2006. Nobel Prize in Physiology or Medicine. It also promotes a race to create new tools based on it. Scientists soon realized that if you could introduce dsRNA to a frightening pathogen — for example, a particularly irritating fungus — you could teach the pathogen’s cells to destroy the mRNA itself and prevent it from make essential proteins. In essence, they can turn off genes within pathogens if desired. “We just go in there and watch the orchestra of genes and proteins there and we silence the violins. That’s all we do,” said Michael Helmstetter, chairman of RNAissance Ag, another competing startup to bring plant RNA sprays to market.

Some RNA sprays are already in the works. RNAissance Ag is working on a spray that targets the diamondback moth, which has an unsatisfactory appetite for cabbages and has to evolve with some resistance of common pesticides. GreenLight Biosciences has an RNA spray targeted at the Colorado potato beetle that is currently being investigated by the Environmental Protection Agency. The company expects a decision on that spray by mid-2022. It is also working on a spray for Botrytis, as well as one who is opposed to Varroa mite, a widespread pest that can affect honey bees. Following preliminary laboratory tests, GreenLight is now trying to spray Botrytis on California grapes and Italian strawberries. Singleton says they are looking to find out how long to spray the plants and how it compares to chemical fungicides.

Plant RNA sprays may have some major advantages over the current toolbox of chemical -based pesticides. The microbes break down the RNA in the soil within a few days, which reduces the problem of environmental degradation. And because RNA sprays target genes specific to individual species, there is — at least in theory — a lower chance that other organisms will be caught in the crossfire. Even the two very similar species have enough genetic differences that it is possible to make RNA sprays that target a bug while leaving one alone, according to Clauvis NT Taning, a postdoctoral researcher who studied RNAi pesticides at Ghent University in Belgium.

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