Colorado potato beetles are a dreaded pest of potatoes all over the world. Because they do not have natural enemies in most potato-producing regions, farmers try to control them with pesticides. However, this strategy is often ineffective because the pest has developed resistances against nearly all insecticides. Now, scientists from the Max Planck Institutes of Molecular Plant Physiology in Potsdam-Golm and Chemical Ecology in Jena have shown that potato plants can be protected from herbivory using RNA interference (RNAi). The scientists genetically modified plants to enable their chloroplasts to accumulate double-stranded RNAs (dsRNAs) targeted against essential beetle genes. The results will be published in the February 27, 2015 iissue of Science. The article title is “Full Crop Protection from an Insect Pest by Expression of Long Double-Stranded RNAs in Plastids.” RNA interference (RNAi) is a type of gene regulation that occurs naturally in eukaryotes. In plants, fungi, and insects it also is used for protection against certain viruses. During infection, many viral pathogens transfer their genetic information into the host cells as double-stranded RNA (dsRNA). Replication of viral RNA leads to high amounts of dsRNA which is recognized by the host's RNAi system and chopped up into smaller RNA fragments, called siRNAs (small interfering RNAs). The cell then uses siRNAs to detect and destroy the foreign RNA. But the RNAi mechanism can also be exploited to knock down any desired gene, by tailoring dsRNA to target the gene's messenger RNA (mRNA). When the targeted mRNA is destroyed, synthesis of the encoded protein will be diminished or blocked completely. Targeting an essential gene of a crop pest can turn dsRNA into a precise and potent insecticide.
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