Less is more? Cutting out--rather than putting in--DNA may bump up corn's nutrition.

Exposing Corn's Latent Nutrition

John is a Science contributing correspondent.

Junk food and junk DNA now have something in common: Eliminate them and nutrition improves. At least according to a pair of researchers who have produced a more nutritious kind of corn by modifying its noncoding "junk" DNA. They hope that this technique will get genetically modified foods onto the market where others have failed.

Corn is a major crop worldwide, but its kernels have low levels of an essential amino acid called methionine. Biologists have struggled to create methionine-rich corn that could provide better nutrition in the developing world. What's more, it would save animal farmers $1 billion per year in synthetic methionine supplements to corn-based feed.

But corn, it turns out, already has a gene for a methionine-rich protein called delta-zein. Its production is limited, however. Biologists Jinsheng Lai and Joachim Messing of Rutgers University in New Brunswick, New Jersey, discovered that another protein hijacks RNA for delta-zein before the protein can be built. The RNA-munching protein, called Dzr1, latches onto a so-called junk region of genetic code, the researchers report in the May issue of Plant Journal. Such sections are normally snipped out of the RNA before it dictates what protein to build.

Removing the sequence, the researchers theorized, shouldn't have any effect on the protein's make-up. So they replaced the bait with a junk code from another corn gene. This prevented Dzr1 from nibbling at delta-zein's RNA and maximized the production of the methionine-rich protein. Chickens fed on this corn grew significantly faster than those fed normal corn.

Because the technique adds no new genes, it sidesteps fears that moving genes between unrelated species could cause unexpected toxicity or spread genes willy-nilly in the wild. But Sue Mayer, director of GeneWatch UK, noted that it must still be determined whether modifying junk DNA "causes any other changes to the composition of the plant that may affect its safety."

Related sites
Joachim Messing's home page
GeneWatch

Posted in Biology