April 1, 2000 / New Scientist / Andy Coghlan
Rice, which provides more than half the daily food for one third of people across the globe, is, according to this story, a key target for genetic engineers seeking to develop new crops to feed the world's burgeoning population. Just such a strain of genetically modified rice, which boosts yields by a massive 35 per cent, was unveiled this week in the Philippines at an international conference on rice biotechnology. As an added benefit, the story says, the GM rice, which has been tested in China, Korea and Chile, extracts as much as 30 per cent more carbon dioxide from the atmosphere than controls, offering a way of curbing global warming.
Maurice Ku of Washington State University in Pullman was cited as telling a conference in Manila hosted by the International Rice Research Institute that the bumper yields, results of which have yet to be published, approach targets which the IRRI say will be needed to feed the population over the coming 20 years.
Paul Christou, a veteran of rice research at the John Innes Centre in Norwich, was quoted as saying, "The potential is enormous."
Kevan Bundell of the charity Christian Aid was quoted as saying, "This rice may have potential provided it doesn't make poor farmers more reliant on expensive external inputs, such as herbicides."
To achieve such thumping gains, the story says Ku inserted maize genes which ramp up photosynthesis, the process by which plants harvest the energy of sunlight to produce sugars from water and CO2. The new genes enable the plant to absorb more CO2. They also stop oxygen from blocking sugar production and, Ku believes, might even help the plant to survive hardships such as drought and heat.
Ku and his colleagues sought to transfer maize genes because maize, sorghum and other related "C4 plants" are more "advanced" than plants like rice. C4 plants absorb CO2 and store large quantities of it instantly as four-carbon acids such as oxaloacetate, malate and aspartate.
Unfortunately for farmers, the story says that most major food crops, including rice, potatoes, wheat and other cereals, haven't evolved the enzymes to perform this trick. These "C3" plants rely on an inferior photosynthetic kit, which creates three-carbon compounds first, such as phosphoglycerate. This less efficient process means that C3 plants exhale much of the CO2 they breathe in.
Working with Mitsue Miyao of the National Institute of Agrobiological Resources in Tsukuba, Japan, and Makato Matsuoka at Nagoya University, Ku was cited as inserting one of three maize genes into rice plants. The first makes phosphoenolpyruvate carboxylase, the enzyme which initiates photosynthesis in maize (Nature Biotechnology, vol 17, p 76). In field trials last year, plants containing this gene yielded up to 12 per cent more rice than controls.
But the researchers saw yields soar by 35 per cent when they inserted the gene for pyruvate orthophosphate dikinase, another enzyme vital for C4 plants. Tests are under way for plants containing the third crucial gene, which codes for nicotinamide adenine dinucleotide phosphate-dependent malic enzyme.
Plants containing either of the first two genes sucked 30 per cent more CO2 from the atmosphere in greenhouse tests.
Ku was quoted as saying, "If we enhance crop productivity by taking out more CO2, it would reduce rising CO2 in the atmosphere which would otherwise cause global warming."
(posted without permission)
