Genetic Weapon Against Insects Raises Hope and Fear in Farming

[Buster's Uncle]

Genetic Weapon Against Insects Raises Hope and Fear in Farming
By ANDREW POLLACK  JAN. 27, 2014



Monsanto is exploring the use of RNA interference to kill a mite that may play a role in bee die-offs. Monsanto



Scientists and biotechnology companies are developing what could become the next powerful weapon in the war on pests — one that harnesses a Nobel Prize-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 target-specific.”

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.



Monsanto is also exploring the use of RNA interference to kill a rootworm that damages corn. Michael E. Gray/University of Illinois


“To attempt to use this technology at this current stage of understanding would be more naïve 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 double-stranded 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 turn 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 corn rootworm, can simply eat the double-stranded RNA to set off the effect.


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