RNA interference instead of Bt toxin

Geneticists have made potatoes poisonous to Colorado beetles

Alexander Khramov, Infox.ru

Scientists have come up with a new way to control agricultural pests. They have bred potatoes with RNA molecules that are deadly to Colorado beetles, Infox reports.

This is stated in an article by German scientists from the Institute of Molecular Plant Physiology of the Max Planck Society, published in the journal Science (Zhang et al., Full crop protection from an insect pest by expression of long double-stranded RNAs in plastids).

The technique proposed by the authors of the article is based on RNA interference. This is the name of the process by which cells destroy foreign viral RNA. When a double-stranded RNA molecule (dsRNA) enters the cytoplasm, it is cut by the Dicer enzyme into short small interfering RNAs (siRNAs). These "scraps" are picked up by a special RNA-protein complex, which begins to destroy all the RNA in the cell that contains such a sequence.

Not so long ago, scientists proposed to embed dsRNA genes into plant cells, in which the sequence of the matrix RNA (mRNA) of a pest insect is encoded, with which some of its important protein is synthesized. When such a plant dsRNA enters insect cells, RNA interference is triggered in them, and as a result, the pest begins to destroy its own mRNAs, depriving itself of the necessary protein.

However, scientists were prevented from using this method in practice by the plants' own RNA interference system. It cut dsRNA molecules into siRNA even before they got into insects, thereby reducing the effectiveness of their action. The authors of the article were able to circumvent this obstacle by launching the synthesis of insecticidal dsRNAs not in the plant cells themselves, but in their chloroplasts.

Since the precursors of chloroplasts were bacterial cells, there is no RNA interference system in them, that is, dsRNA molecules in chloroplasts can accumulate unhindered, entering the intestines of an insect intact. The researchers provided GM chloroplasts producing dsRNA to potato leaves.

During the experiments, torn potato leaves carrying such chloroplasts caused the death of all larvae eating them on day 5, since dsRNA interrupted the synthesis of actin protein in insects. At the same time, potatoes, which synthesized dsRNA from the genes of the nucleus of the plant cell itself, did not cause such an effect, since such molecules were quickly destroyed in the cytoplasm.

In the picture from the press release of the Max Planck Institute for Chemical Ecology Fighting the Colorado potato beetle with RNA interference, on the left - the leaves of ordinary potatoes, on the right – plucked from plants with modifications in the chloroplast genome. The newly hatched larvae of the Colorado potato beetle were fed with these leaves, replacing the bitten ones with fresh ones once a day. It is clear that the bush of GM potatoes will be damaged, but to a minimal extent that does not affect the yield of tubers - VM.Scientists hope that their invention will open a new era in the use of RNA interference for pest control.

In the case of Colorado beetles, this is especially true, since they easily adapt to conventional pesticides and do not have natural enemies in the countries where they were introduced.

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