‘Gene Stacking’ Tool Produces Antioxidant-Rich Purple Rice

Researchers genetically engineered rice to produce anthocyanins, which are pigments found in purplish foods and can help protect against a wide array of diseases.

Purple rice could help billions of people get their vitamins, Chinese researchers claim.

Publishing their findings today in the journal Molecular Plant, the South China Agricultural University biologists genetically engineered rice to produce anthocyanins, antioxidant-rich pigments also found in red wine, dark berries, and other purplish foods.

What’s more, the scientists used so-called “gene stacking” to infuse the anthocyanin in the rice’s endosperm, or the part eaten as white rice that doesn’t include the grain’s husk, bran, or germ. Brown rice, which is more nutritious, includes those parts but doesn’t contain anthocyanins. Long popular among healthy food shoppers, black rice contains anthocyanin but it’s not as popular as white or brown rice.

The scientists believed the discovery of more edible “Zijingmi” – or purple endosperm rice in Chinese – could lead to new superfoods that might deliver vitamins and other benefits on a mass scale. Anthocyanin combats certain cancers, cardiovascular disease, diabetes, and other chronic disorders, the researchers said.

The National Natural Science Foundation of China, the Chinese Ministry of Agriculture, and the Guangdong Province Public Interest Research and Capacity Building Special Fund helped support the researchers’ work.

“If we could promote this bio-refined, nutritionally enhanced food, it might benefit kids who suffer from vitamin deviancies,” said Yao-Guang Liu, the study’s senior author.

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Previous efforts to infuse rice endosperm with anthocyanin had fizzled because scientists couldn’t find the right combination of genes to tweak. Liu and his colleagues compared black and red rice that contain anthocyanin with traditional Japonica and Indica rice varieties to break that code.

"This is the first demonstration of engineering such a complex metabolic pathway in plants," said Liu.

The gene stacking technique they used in their study could rapidly find other combinations that were previously unknown, they added. The process entails altering numerous genes simultaneously in manners that don’t necessarily affect one another.

“Basically, you used to use trial and error to get an understanding of which gene is required. You used the cut-and-paste strategy,” said Liu, referring to older genetic engineering techniques that altered one gene at a time. “This is time consuming and inefficient. Now we modified the system.”

A similar approach created vitamin A-enriched “golden rice” that has been hailed as a way to end childhood blindness and other ailments that are widespread in the developing world.

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Rice could also be a more effective way of storing nutrients, the researchers said. It would be easier to produce and keep anthocyanin in rice than deal with grapes or other perishable materials, they noted.

“This has a lot of commercial value in industry, especially for healthcare and cosmetics,” said lead author Qinlong Zhu of South China Agricultural University. “You can store it in a long term. Once you dry the seed, it’s easy for transport.”

Liu, Zhu, and their colleagues were now testing to make sure the rice is safe to eat.

“We’re cautious,” said Liu, who acknowledged that some would reject the notion of genetically altering rice or any other food in any way. “Some people are very concerned. We need to do more experiments to convince people that these are completely safe to release commercially."

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