NUTRITIOUS WHEAT: A newly discovered gene boosts the protein, zinc and iron available in wheat by as much as 15 percent and can be incorporated without resorting to genetic modification. Image: COURTESY OF ZVI PELEG AND ASSAF DISTELFELD
Humanity has been growing wheat as a staple crop for thousands of years, and we currently grow 620 million tons of the grain annually. During that span, however, its nutrition has largely not improved; in fact, it may have declined. But by returning to wheat's wild roots, researchers have found a gene that will boost the grain's nutritional value by speeding up its life span.
Wheat breeder Jorge Dubcovsky of the University of California, Davis, led an international team that discovered the gene-- dubbed gpc-B1 for its effect on grain protein content--in a wild emmer wheat that has grown naturally in the Middle East for millennia. His colleague Cristobel Uauy examined cultivated wheat breeds and discovered they all shared a nonworking copy of this gene. By inserting a cloned version of the wild gene into conventional wheat plants they boosted the amount of protein, zinc and iron in the grain by 10 to 15 percent. The gene works by making the plant mature more rapidly, thus speeding up the transfer of these nutrients from the leaves to the grain.
Further, by using RNA interference to block the effects of this gene, the researchers produced wheat that had 30 percent less of the nutrients in its grains, according to the paper presenting the result in the November 24 issue of Science. "This experiment confirmed that this single gene was responsible for all these changes," Dubcovsky notes.
Adding this gene back into the conventional wheat supply could help remedy the zinc and iron deficit suffered by more than two billion people worldwide, according to World Health Organization statistics. And more than 160 million children lack adequate protein in their diet, which this enhanced wheat could supply. "If you do not have anything else available to eat, it would be good to have wheat that provides more protein and micronutrients," Dubcovsky says. "We are also working on a new mutant that will eliminate an antinutrient present in wheat--phytic acid--which reduces the bioavailability of the zinc and iron present in the grain."
Such enhanced wheat could be available in 2007; Dubcovsky and others plan to release wheat varieties created using conventional breeding techniques to incorporate the gene within a year. But it remains unclear what the exact impact of including this double copy of the gene will be on a broader scale. "The exact effect depends on the genetic background of the [wheat] variety and the environment where the gene is used," Dubcovsky notes. "This needs to be tested experimentally." Still, it may have a broad impact, because other staple cereals share the gene. "Rice has a similar gene and we have created transgenic plants with reduced level of this gene to see if it also affects the same traits in rice," he adds. "We should know within the next six months."