[Pollinator] NY Times: Genetic Weapon Against Insects Raises Hope and Fear in Farming

[Kelly Rourke]

http://www.nytimes.com/2014/01/28/business/energy-environment/genetic-weapon
-against-insects-raises-hope-and-fear-in-farming.html?_r=1

 

 

http://ryti.rns/ljl3Plq

ENERGY & ENVIRONMENT

Genetic Weapon Against Insects Raises Hope

and Fear in Farming

By ANDREW POLLACX JAN. Zl, 2014

Scientists and biotechnology companies are developing what could

become the next powerful weapon in the war on pests - one that

harnesses a Nobel Pri2e-winning discovery to kill insects and pathogens by

disabling their genes.

By zeroing in on a genetic sequence unique to one species, the

technique has the potential to kill a pest without harming beneficial

insects. That would be a big advance over chemical pesticides.

"If you use a neuro-poison, it kills everything," said Subba Reddy

Palli, an entomologist at the University of Kentucky who is researching the

technology, which is called RNA interference. "But this one is very
targetspecific."

But some specialists fear that releasing gene-silencing agents into

fields could harm beneficial insects, especially among organisms that have

a common genetic makeup, and possibly even human health. The

controversy echoes the larger debate over genetic modification of crops

that has been raging for years. The Environmental Protection Agency,

which regulates pesticides, will hold a meeting of scientific advisers on

Tuesday to discuss the potential risks of RNA interference.

"To attempt to use this technology at this current stage of

understanding would be more naive than our use of DDT in the 1950S," the

National Honey Bee Advisory Board said in comments submitted to the

E.P.A before the meeting, at the agency's conference center in Arlington,

Va.

RNA interference is of interest to beekeepers because one possible use,

under development by Monsanto, is to kill a mite that is believed to be at

least partly responsible for the mass die-offs of honeybees in recent years.

Monsanto has applied for regulatory approval of corn that is

genetically engineered to use RNAi, as the approach is called for short, to

kill the western corn rootworm, one of the costliest of agricultural pests.
In

another project it is trying to develop a spray that would restore the
ability

of its Roundup herbicide to kill weeds that have grown impervious to it.

Some bee specialists submitted comments saying they would welcome

attempts to use RNAi to save honeybees. Groups representing corn,

soybean and cotton farmers also support the technology.

"Commercial RNAi technology brings u.S. agriculture into an entirely

new generation of tools holding great promise," the National Corn Growers

Association said.

Corn growers need a new tool. For a decade they have been combating

the rootworm by planting so-called BT crops, which are genetically

engineered to produce a toxin that kills the insects when they eat the crop.

Or at least the toxin is supposed to kill them. But rootworms are now

evolving resistance to at least one BT toxin.

RNA interference is a natural phenomenon that is set off by doublestranded

RNA

DNA, which is what genes are made of, is usually double stranded, the

famous double helix. But RNA, which is a messenger in cells, usually

consists of a single strand of chemical units representing the letters of
the

genetic code.

So when a cell senses a double-stranded RNA, it acts as if it has

encountered a virus. It activates a mechanism that silences any gene with a

sequence corresponding to that in the double-stranded RNA

Scientists quickly learned that they could deactivate virtually any gene

by synthesizing a snippet of double-stranded RNA with a matching

sequence.

The scientists who first unraveled this mechanism won the 2006

Nobel Prize in Physiology or Medicine, and it was initially assumed that

most of the use would be in medicine. Imagine drugs that could tum off

essential genes in pathogens or tumors, or one that contributes to high

cholesterol.

The initial euphoria has cooled somewhat, in part because it has been

difficult to deliver the RNA through the bloodstream into the cells in the

body where it is needed. Still, the challenges are gradually being overcome,

and enthusiasm is rising again.

Using RNAi in insects, at least for beetles, should be easier than in

people. Beetles, including the com rootworm, can simply eat the
doublestranded

RNA to set off the effect.

One way to get insects to do that is to genetically engineer crops to

produce double-stranded RNA corresponding to an essential gene of the

pest.

Various genetically engineered crops already harness RNAi to silence

genes in the crop itself. These include soybeans with more healthful oil and

a nonbrowning apple that appears close to federal approval. The

technique has also been used to genetically engineer virus resistance into

crops like papaya.

But generally those crops had been developed using methods to

modify DNA that were known to work but were not understood at the time

to involve RNAi. Monsanto's new rootworm-killing com is one of the first

in which the crop has been engineered specifically to produce a
doublestranded

RNA, in this case to inactivate a gene called Snf7 that is essential

for moving proteins around in the rootworm. Monsanto, which is based in

St. Louis, hopes to have the com, which it calls SmartStax Pro, on the

market late this decade.

The double-stranded RNA could also be incorporated in sprays.

Monsanto is developing a spray that would shore up one of its biggest

product lines - crops resistant to its Roundup herbicide. Farmers have

grown them widely because they can spray Roundup to kill weeds without

hurting the crop.

Roundup, known generically as glyphosate, works by inhibiting the

action of a protein plants need to survive. But many weeds have evolved

resistance to Roundup. Some of these weeds make so much of the protein

that Roundup cannot inhibit it all.

Monsanto's spray would use RNAi to silence the gene for that protein,

reducing production of the protein and restoring the ability of Roundup to

kill the weed.

Monsanto is also looking at putting RNA into sugar water fed to

honeybees to protect them from the varroa mite. The way to fight the mite

now is to spray pesticides that can also harm bees.

''We were trying to kill a little bug on a big bug," said Jerry Hayes, the

head of bee health at Monsanto.

If the RNAi is directed at a genetic sequence unique to the mite, the

bees would not be harmed by ingesting it, while the mites would be killed

once they attacked the bees. One field trial showed that this technique

could help protect bees from a virus. Monsanto acquired Beeologics, a

company developing the RNAi technology for bees. It bought at least two

other companies pursuing agricultural applications of the technology. And

it has paid tens of millions of dollars for patent rights and technology
from

medical RNAi companies like Alnylam Pharmaceuticals and Tekmira

Pharmaceuticals.

But Monsanto is not alone. In 2012, Syngenta signed an agreement to

work on RNAi sprays with Devgen, a Belgian biotech company, and later

said that it had acquired all of Devgen for around $500 million.

Some scientists are calling for caution, however, In a paper published

last year, two entomologists at the Department of Agriculture warned that

because genes are common to various organisms, RNAi pesticides might

hurt unintended insects.

One laboratory study by scientists at the University of Kentucky and

the University of Nebraska, for instance, found that a double-stranded

RNA intended to silence a rootworm gene also affected a gene in the

ladybug, killing that beneficial insect.

Concerns about possible human health effects were ignited by a 2011

paper by researchers at Nanjing University in China. They reported that

snippets of RNA produced naturally by rice could be detected in the blood

of people and mice who consumed the rice and could even affect a gene

that regulates cholesterol. Such a "cross kingdom" effect would be

extraordinary and was met with skepticism. At least three studies

subsequently challenged the findings.

In a paper prepared for Tuesday's meeting, E.P.A scientists said RNAi

presented "unique challenges for ecological risk assessment that have not

yet been encountered in assessments for traditional chemical pesticides."

A version of this article appears in print on January 28, 2014, on page A1
of the New York edition

with the headline: Genetic Weapon Against Insects Raises Hope and Fear in
Farming.

C 2014 The New York Times Company

 

Kelly Rourke

Program Associate

Pollinator Partnership

423 Washington Street, 5th Floor

San Francisco, CA 94111-2339

T: 415-362-1137 

F: 415-362-3070

E:  <mailto:kr at pollinator.org> kr at pollinator.org

 <http://www.pollinator.org> www.pollinator.org

 

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