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Restoring some of wheat’s ancient nutritional luster

By Clifton B. Parker on July 20, 2007 in University News

If you want to improve people's health, you study medicine, right?

Not necessarily.

For Cristobal Uauy, a newly minted postdoc in the UC Davis Department of Plant Sciences, agronomy may prove a quicker path to enhancing health. During five years of graduate research at UC Davis, Uauy (pronounced WAH-WEE) helped to discover a gene that affects protein, zinc and iron content in wheat, a discovery that some are calling an important step toward eradicating world hunger.

Hunger claims the lives of 20,000 children a day. The World Health Organization estimates that the diets of more than 2 billion people are deficient in zinc and iron, and more than 160 million children under the age of 5 do not eat enough protein. Worldwide, one of every three children is underweight and malnourished.

Ten thousand years ago, wild wheat used to be a good source of protein and minerals — elements less prevalent in wheat today after centuries of domestication. What if you could find and clone the lost genes that made wild wheat so nutritious? Could you breed them back in to modern strains, restoring wheat's nutritional luster?

The answer appears to be yes, thanks to the science of Uauy and his team.

"It's just one step," Uauy said. "It's no magic bullet. But the possibilities are exciting."

Uauy and his team picked up where other scientists left off. Some 100 years ago in what is now Israel, a scientist named Aaron Aaronsohn happened upon emmer wheat growing wild along the Sea of Galilee, just as it had for thousands of years. In 1910, he wrote about it in a U.S. Department of Agriculture publication. Sixty years later, a scientist named Moshe Feldman collected the same wild wheat from the hearths of Stone Age villages and sent them to America.

In 1997, UC Davis geneticist and wheat breeder Jorge Dubcovsky assembled a team and began researching the genetic qualities of wild and domesticated wheat.

Uauy joined that team in July 2002, coming from Chile where he had completed his undergraduate work at Catholic University. One visit with Dubcovsky, and Uauy knew UC Davis would be a perfect fit for his graduate work.

"I connected right away with Jorge," Uauy said. "And I was intrigued by the genetic work he was doing, which combined basic and applied science."

There is a negative correlation between yield and protein in wheat. Had the gene that controls protein been compromised after centuries of breeding to increase yield? Could Dubcovsky's team find the gene in wild wheat that affects protein?

Talk about a needle in a haystack. Uauy recalled: "I told my friends what we were trying to do and they said, 'Good luck! See you in 10 years.' "

Uauy worked in tandem with another graduate student — Assaf Distelfeld — from Tzion Fahima's laboratory in Israel. Day after day, week after week, month after month, they walked through the chromosome. Said Uauy: "Together, we moved twice as fast."

After years of mapping, they found a gene that called attention to itself. It seemed to regulate other genes and — miracle of miracles — increase the protein, zinc and iron content of grain by 10 percent to 15 percent.

"We were very excited — and very lucky," Uauy said. "One mutation seemed to explain everything."

They cloned the gene and Dubcovsky designed the field testing — cross-breeding wheat and planting it in the Department of Plant Sciences field station southwest of Russell Boulevard and La Rue Road.

Once a week Uauy would check on the wheat. But one week, he happened to go twice, and noticed something amazing. "Half the plants were starting to whither," he said, his eyes wide with excitement. "And because of the way we planted the wheat, you could tell unequivocally that all the plants from the same wild strain were withering, no matter where they were planted in the field."

When Uauy visited earlier that week, all the plants were green. If he had waited a few more days, all the plants would have been brown. But because of his random, midweek visit, the team discovered not just the gene that controls protein, but its very mechanism.

"Senescence," Uauy said. "All the high-nutrient plants had accelerated senescence, which means the plants send all the good stuff to the grain and doesn't keep any for the dying leaves."

The gene makes plants more efficient, he explained.

"It's like in a burning building," he said. "The efficient plant can send all the important stuff — the nutrients — out to the grain before it burns down. The less efficient plant isn't as fast at sending out the good stuff as quickly. It keeps some of it in its leaves, so it stays greener longer — and the grain isn't as nutritious."

Understanding the mechanism of nutrient distribution in plants is a big breakthough in the fight against world hunger, said Jonathan Gitlin, a pediatrician and geneticist at Washington University in St. Louis. Writing in the Nov. 24, 2006, edition of Science magazine, published by the American Association for the Advancement of Science, Gitlin said of the UC Davis research: "These elegant new studies reinforce the inherent value of basic science research for improving the lives of those youngest among us who remain without a voice in this world."

Dubcovsky, Uauy and their team have bred the ancestral protein-regulating gene back into modern wheat varieties (which all lack the gene) without the need for more controversial genetic engineering. The new seeds are being distributed to farmers all over the world.

"But it's still just one step," Uauy said. "There are many more questions. What gene does our gene control? What affect will this have on yield, and what affect will yield have on the nutrient content?"

With his graduate work behind him, Uauy will stay at Davis for at least a few years of post-doctoral work. Eventually, he wants to return to Chile.

Uauy's father is a pediatrician and very active in work to fight world hunger and improve child nutrition. When he was younger, Cristobal thought he should follow in his father's medical footsteps.

"Isn't it funny?" he asked. "I chose agronomy, and it seems to be leading me right back around to my father's field."

COVER STORY

Professors Jorge Dubcovsky and Jan Dvorak of the UC Davis Department of Plant Sciences contributed an article on wheat for Science magazine’s June 29 package on plant domestication. The magazine cover focused on wheat, showing a laborer using a sieve to separate wheat husks from the grain at a market in Amritsar, India. Science is published by the American Association for the Advancement of Science. Dubcovsky and Dvorak’s article is available online: www.sciencemag.org/cgi/content/full/316/5833/1862.

Diane Nelson is a writer for the Department of Plant Sciences.

Media contact(s)

Clifton B. Parker, Dateline, (530) 752-1932, cparker@ucdavis.edu

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