- Source: Cell Press
- Summary:
- Plants are among many eukaryotes that can 'turn
off' one or more of their genes by using a process called RNA
interference to block protein translation. Researchers are now
weaponizing this by engineering crops to produce specific RNA fragments
that, upon ingestion by insects, initiate RNA interference to shut down a
target gene essential for life or reproduction, killing or sterilizing
the insects.
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FULL STORY
Cornfield.
Credit: © Soru Epotok / Fotolia
Plants are among many eukaryotes that
can "turn off" one or more of their genes by using a process called RNA
interference to block protein translation. Researchers are now
weaponizing this by engineering crops to produce specific RNA fragments
that, upon ingestion by insects, initiate RNA interference to shut down a
target gene essential for life or reproduction, killing or sterilizing
the insects. The potential of this method is reviewed in Trends in Biotechnology's upcoming special issue on environmental biotechnology.
As chemical pesticides raise concerns over insect resistance,
collateral environmental damage, and human exposure risks, transgenic
methods are becoming an attractive option for future pest control. For
instance, certain strains of corn and cotton have been modified to
produce protein toxins from the bacterium Bacillus thuringiensis
(Bt) that poison certain worms, beetles, and moths. RNA interference
adds another degree of subtlety, by instead shutting down essential
genes in pests that consume crops.
"RNA interference-based pest control can provide protection at
essentially no cost because once the variety is developed, the plant can
just go on using it instead of needing additional applications of
insecticide," says co-senior author Ralph Bock, a director at the Max
Planck Institute of Molecular Plant Physiology in Germany.
An RNA interference strategy could also address environmental and
human toxicity questions around chemical pesticides. "When we target a
key pest with RNA interference technology, what we are really hoping for
is to see a big reduction in overall insecticide use," says co-senior
author David Heckel, a director at the Max Planck Institute of Chemical
Ecology.
Besides application cost and environmental advantages, advocates of
the method also point to the flexibility of finding a genetic target and
its species specificity. While chemical pesticides such as
organophosphates work by overloading an insect's nervous system, a
suitable RNA interference target might control something as esoteric,
yet indispensable, as cellular protein sorting. Additionally, even when
certain target genes are similar across species, optimally designed RNA
fragments only inhibit one species and its closest relatives, rather
than overwhelming non-threatening insects as some chemical pesticides
do.
Earlier attempts at pest control through genetic modification that
have involved engineering plants to produce proteins toxic to certain
insects have prompted concerns about what happens to those proteins when
the crop is harvested and ingested. "The objections to transgenic
proteins involve concerns about their possible toxicity or allergenicity
to humans, but with the RNA interference strategy there's no protein
that is made, just some extra RNA," Bock says.
RNA interference faces multiple obstacles before it could work for
all major crops and their pests. On the plant side, scientists have not
yet found a way to transform the chloroplast genomes of cereal grains
such as rice and corn, the most direct route to producing enough RNA
fragments to eliminate pests at a high rate. On the insect side,
prominent pests such as some caterpillars can degrade those fragments,
staving off shutdown of the target gene.
Bock and Heckel both expect RNA interference technology to be roughly
6 to 7 years away from the field, but they are cautiously optimistic
about its potential to change the debate around GMO technology in
agriculture. "The Colorado potato beetle is almost worldwide now, even
reaching into China," Heckel says. "With such a spread of a main pest
that's resistant to insecticides, there's a good case for the
development of a transgenic potato to try to halt that trend, and
hopefully it will demonstrate enough advantages to overcome the
opposition to any and all genetic modifications in crops."
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