New gene technique may sidestep some GM crop concerns

When is a genetically modified plant not genetically modified?

When its genes are being suppressed rather than spliced, claim researchers from Bayer CropScience. The German firm has developed a way of engineering plants to withstand tougher conditions that could get round the ethical concerns posed by genetically modified plants.

By increasing crop yields, the technique could help to feed more people more cheaply. It could also help to slow the pace of climate change by improving the yields of biofuels, and thereby cutting fossil fuel use. The breakthrough was needed because living threats such as pests and weeds do surprisingly little damage to crops.

Most of the harm is done by "abiotic" factors such as heat, drought and flooding, which knock off about three quarters of the yield. This is because plants that are facing difficult environmental conditions spend too much energy on protecting their cells and not enough on growth. This severely limits the yields of many crops.

Now Bayer's scientists have developed a "genetic shock absorber" to right this balance and boost the growth of crops during periods of excessive heat, drought and cold.

The way it works is simple to grasp. In stressful circumstances, plants protect themselves by switching on a gene called PARP. This produces a protein of the same name that repairs the plant's DNA and shields its cells from damage. Unfortunately, the protein needs a lot of energy to do its job, and because plants can't predict how long tough conditions will last, they end up over-producing it. If the hard times persist, the plant eventually runs out of energy.

But Michael Metzlaff, head of Bayer's crop productivity research group, has developed a way to fine tune the repressive levels of PARP so the plant can continue to grow while still being protected from the elements. He uses a technique called RNA interference, which employs a special molecule to block the message sent from the DNA that tells the plant to produce more of the PARP protein. The gene isn't completely shut off, but the plant's hyperactive stress response is toned down.

"The plants are more relaxed," says Metzlaff. "They can lean back and just do what they have to do." Metzlaff's method can be very specifically targeted to a plant of choice, using parts of the PARP genetic sequence that do not exist in other species. This tight control should allay fears from the anti-GM lobby that the RNA molecule could spread and harm other species in the area. Nor is the technique "unnatural." Plants themselves use RNA interference to fine tune the activity of their genes and to protect themselves from viruses.

Metzlaff stresses that RNA interference only uses genes and proteins that are a natural part of the plant: it plays with the recipe, but never adds new ingredients to the mix. "It's not classical GM," he says.

At first, Metzlaff tried the technique in mustard cress, a plant favoured by geneticists because it is easy to grow and manipulate. When subjected to heat, drought and cold, the modified plants showed an increase in yield of between 10 and 20 per cent compared with normal cress. In extreme cases, Metzlaff saw a 44 per cent improvement in growth. Since then, Bayer has successfully tested the RNA interference method in field trials with oilseed rape and canola, a crop that could be a significant source of biofuels. It is now conducting trials on cotton and rice. If successful, the hardier plants could be invaluable in coping with the difficult conditions that global warming will bring about, and so safeguarding tomorrow's harvests.

The Telegraph