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April 28, 2009

Researchers develop gene-modified vitamin-fortified maize variety

by Karen Kaplan

Scientists have engineered vitamin-fortified maize designed to boost consumption of three key nutrients that are sorely lacking in the diets of millions of people in developing countries, according to a new study.

The genetically modified African maize has bright orange kernels, reflecting the 169-fold increase in beta carotene, a precursor of vitamin A. The corn also has six times the normal amount of vitamin C, and double the usual level of folate, researchers reported in the Proceedings of the National Academy of Sciences.

Though genetic engineering has been used to enhance vitamin content in a variety of crops -- including rice, potatoes, lettuce and tomatoes -- this is the first time scientists have been able to amplify multiple vitamins in a single plant.

"They really have made a major step forward here," said Martina Newell-McGloughlin, a plant pathologist at UC Davis who wasn't involved in the study. "I could see this transforming the field. It's just really cool stuff."

Corn breeders could potentially create the same plant by conventional means -- if they kept at it for several hundred years, Newell-McGloughlin said.

The researchers, from Spain and Germany, targeted this particular combination of vitamins because deficiencies in them cause many diseases in the developing world, said study leader Paul Christou of the University of Lleida in Spain. The beta carotene boost was the most dramatic because scientists are most familiar with the genes controlling that nutrient, he said.

The team inserted five genes from other organisms -- including rice and Escherichia coli -- into a popular South African white corn variety called M37W that Christou said is "completely devoid of vitamins."

To embed the genes into the corn's DNA, the researchers attached them to microscopic gold particles and shot them into immature corn embryos in a laboratory dish. When the cells divided, they contained the new genes.

The method the scientists used insures that the five genes are inserted in the genome together, so that they stick together in subsequent generations. The genes have stayed intact over four generations so far, according to the study.

These orange corn plants are just a proof of concept, the scientists added. To grow in Africa, Central America or elsewhere, they would have to be crossed with the many corn varieties adapted to specific regions. That process could take 10 years, said Gary Toenniessen, an agriculture specialist at the Rockefeller Foundation in New York who is involved with the rollout of a genetically engineered crop, Golden Rice, which is fortified with beta carotene.

But most of the target countries in Africa don't even have systems in place to evaluate and approve genetically modified crops, and several countries have banned them, Toenniessen said.

"They're going to be up against quite a challenge to actually take a product like what they've produced and eventually get it out to farmers," he said.

Other scientists are using conventional breeding to make corn more nutritious. The nonprofit HarvestPlus initiative is trying to create crops with 15 micrograms of beta carotene per gram of corn. That's only one-quarter as much as the European researchers achieved, but it's 10 times the amount in run-of-the-mill yellow corn, said Kevin Pixley, who leads corn-breeding efforts at HarvestPlus.

Considering the resistance to genetically modified foods, conventional breeding is probably a better way to create fortified corn plants for poor farmers, said Pixley, who is based at the International Maize and Wheat Improvement Center outside Mexico City. But in some cases, he said, genetic engineering is the only option.

"For certain other crops and nutrients, the naturally occurring genetic variation simply does not exist to allow achieving useful levels via conventional breeding," he said.

Los Angeles Times

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