Tiny plant that may feed the world

With temperatures expected to rise to levels that will endanger the world's food supply, scientists are nurturing a tiny plant in the hope that it will lead to a genetic breakthrough allowing adapted varieties of crops to grow in warmer climates.

An Arabidopsis seedling which is being used to find mutants not responsive to temperature.

Rising sea levels, unbearably hot summers, droughts and intense storms - the prospect of a world afflicted by climate change is little short of terrifying. But the biggest threat may not be the direct physical consequences of rising temperatures. It could be a lack of food. Crops that have adapted to growing in more temperate conditions might struggle to provide the same yields when the mercury rises. A heatwave that hit Europe in the summer of 2003 gave a chilling indication of what could be in store.

Yields of wheat dropped by more than 20 per cent in France, while those of fodder crops plunged as much as 60 per cent, contributing to a ?13 billion ($18.4bn) loss across the continent. "Historically, crop yields have gone up considerably, but the real challenge for agriculture over the next 50 years will be to increase crop yields while decreasing inputs in the face of climate change," says Dr Philip Wigge, a researcher at the John Innes Centre, a plant sciences research institute in Norwich, England.

"The projections are that we need to increase yields by 2030 by 50 per cent because of increases in population and affluence." And yet, says Dr Wigge, global temperatures are projected to increase about 4°C by 2100, and each 1°C increase can cause wheat and rice yields to drop by as much as 16 per cent. "That alone will have a huge effect on crop yields," he says. This all puts the onus on scientists to find ways of engineering plants so they will not suffer catastrophic drops in yields as temperatures increase. Dr Wigge and his colleague Vinod Kumar believe they have taken science a step closer to finding the solution.

Working with Arabidopsis, a tiny plant that reproduces quickly, helpful for laboratory experiments, the researchers connected a luminescent marker to a gene that is switched on by warmer temperatures. As temperatures increased, so did the luminescence of the plants. This allowed them to identify mutants that were not responsive to temperature, those plants that were just as luminescent when the temperature was low as when it was high.

The mutant plants had a change in a gene affecting a histone protein that the plant's DNA normally wraps itself around. In normal plants, the DNA is wrapped more tightly around this histone protein at lower temperatures, and when the temperature increases, the DNA is unwrapped and its genes are switched on. But in the mutants the histone is not incorporated into DNA, even at low temperatures, so the genes are expressed even when it is cooler. As a result, these plants grow at low temperatures just as well as their normal cousins do in warmer conditions.

By understanding the genetics of temperature sensing, the scientists believe it could be possible to create crops that grow in hot temperatures that conventional varieties cannot cope with. "Our long-term goal is to understand how temperature is sensed," says Dr Wigge. "If we can understand that, we can adapt plants to alter how they perceive temperatures from a number of different climates." Preliminary studies in yeast, which are fungi and not plants, have found similar results to those seen with Arabidopsis. This suggests that the genes involved in the temperature response could be conserved across eukaryotes, which are those organisms that, unlike bacteria, have a more complex cell structure.

That the mechanisms are highly conserved across different organisms suggests it will be possible to manipulate crop plants using the genes analysed in Arabidopsis. However, Dr Wigge does not believe transferring the knowledge they have gained with Arabidopsis to the most important crop plants can be done overnight. "We have done this in Arabidopsis where we can do experiments in a few months, but to move that knowledge into crop plants may take 15 to 20 years, although that would be within the timescale we've got," he said. "We'll take the genes in Arabidopsis and use them in wheat and rice."

In particular, the researchers are interested in manipulating temperature perception of the parts of the plant, such as the grains, that are the most important. "We'll probably do this with collaborators," said Dr Wigge. "We'll supply the tool kit. There are many world-class wheat and rice labs. "That's the big goal, our long-term aim: to see if we can create climate-proof crops." @Email:[e-mail]