Beetle RNA makes crops a noxious meal

To keep pests at bay, try giving them a taste of their own genes. Hungry beetles spurn crops bearing the insects’ genetic material, scientists report in the Feb. 27 Science. When pests munch the engineered plants, beetle RNA in the leaves switches off key genes in the bugs.

The Colorado potato beetle is a voracious pest that has become resistant to many chemical pesticides. To protect potato plants from its ravages, researchers transplanted fragments of beetle genes into the crops.

The team chose machinery in plant cells called plastids to house the insect genes. Chloroplasts, which perform photosynthesis, are the most common type of plastids. They are found in the very part of the plant that potato beetles dine on: the leaves.

When laced with the insect gene fragments, the potato plants produce genetic material called double-stranded RNA that disables key genes in the beetles. Double-stranded RNA turns those genes off by stopping their instructions from being converted into proteins.

When potato beetles devoured leaves from the modified plants, cells in the bugs’ guts came into contact with insect RNA from the meal. The double-stranded RNA set to work flipping off genes the beetles need to survive.

It was not long before the insects’ guts started to break down, says Jiang Zhang, a coauthor of the new study and geneticist at the Max Planck Institute of Molecular Plant Physiology in Potsdam, Germany. Within three days, the adults had stopped feeding and left the potato plants alone. After four days, all the larvae that feasted on potato plants were dead.

Because plastids have their own DNA that doesn’t make it into pollen, the beetle genes can’t spread to other plants pollinated by the engineered crops.