New 'Golden Rice' Carries Far More Vitamin
Claims that genetically engineered "golden rice" can help prevent blindness by boosting vitamin A intake have been bolstered by a new strain.
Compared with the original golden rice unveiled in 2000, "Golden rice 2" contains up to 23 times more provitamin A, the substance converted in the body into vitamin A. This vitamin is vital for preventing childhood blindness, which affects 500,000 children worldwide each year.
The breakthrough was achieved by replacing a gene originally borrowed from daffodils, and which also has a counterpart from maize. "We found it made a dramatic difference - a 20-fold increase," says Rachel Drake, head of the team at Syngenta Seeds in Cabridge, UK, which developed the new strain.
"I'm absolutely delighted, and I think it's a very compelling story," says Drake, whose team developed the new strain for the Humanitarian Rice Board which runs the golden rice project at the University of Freiburg in Germany.
Critics of the original golden rice said that its levels of provitamin A - 1.6 micrograms per gram of rice - were too low to make the rice a practical proposition. But each gram of the new strain contains up to 37 micrograms of the provitamin.
Drake estimates conservatively that the rice could provide at least half what a child would need. But Jorge Mayer, golden rice project manager in Freiburg, is even more upbeat, saying the rice might now contain enough to supply the entire recommended daily intake.
But critics point out that it remains to be proven that the provitamin A is absorbed and converted into vitamin A when people eat the rice. They see the project as little more than a public relations exercise to soften up consumer opposition to GM foods.
"There are still lots of unanswered questions," says Christoph Then, Greenpeace's genetic engineering spokesman. "Even after five years of study, the researchers don't know how much provitamin A is left when the rice is cooked. And no risk assessments for the environment or human health have been performed."
Mayer says that questions about the uptake of provitamin A, also known as beta carotene, could be answered later in 2005 through feeding experiments in people using the original golden rice.
Coming up trumps
To ramp up the levels of provitamin A, Drake and her colleagues scrutinised the original golden rice plants, which contained two extra genes. One, called phytoene synthase, had been taken from daffodils. The other, called carotone synthetase 1, came from the soil bacterium, Erwinia uredovora.
She discovered that the enzyme made by the phytoene synthase was the "bottleneck" in production. When she tried counterpart genes from other plants to see if they worked better in the rice, the gene from maize came up trumps.
Syngenta owns golden rice 2, but is donating it to the Humanitarian Rice Board. Mayer says that permits have now been received allowing planting of the rice in India and the Philippines, two countries where the rice could have a real impact.