Using genetic engineering techniques to alter photosynthesis, they increased the productivity of a test plant — tobacco — by as much as 20 percent, they said Thursday in a study published by the journal Science.

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URBANA, Ill. — A decade ago, agricultural scientists at the University of Illinois suggested a bold approach to improve the food supply: Tinker with photosynthesis, the chemical reaction powering nearly all life on Earth.

The idea was greeted skeptically in scientific circles and ignored by funding agencies. But one outfit with deep pockets, the Bill & Melinda Gates Foundation, eventually paid attention, hoping the research might help alleviate global poverty.

Now, after several years of work funded by the Seattle-based foundation, the scientists are reporting a remarkable result.

Using genetic-engineering techniques to alter photosynthesis, they increased the productivity of a test plant — tobacco — by as much as 20 percent, they said Thursday in a study published by the journal Science. That is a huge number, given that plant breeders struggle to eke out gains of 1 or 2 percent with more conventional approaches.

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The scientists have no interest in increasing the production of tobacco; their plan is to try the same alterations in food crops, and one of the leaders of the work believes production gains of 50 percent or more may ultimately be achievable. If that prediction is borne out in further research — it could take a decade, if not longer, to know for sure — the result might be a transformation of global agriculture.

The findings could also intensify the political struggle over genetic engineering of the food supply. Some groups oppose it, arguing that researchers are playing God by moving genes from one species to another. That argument has gained some traction with the public, in part because the benefits of gene-altered crops have so far been modest at best.

But gains of 40 or 50 percent in food production would be an entirely different matter, potentially offering enormous benefits for the world’s poorest people, many of them farmers working small plots of land in the developing world.

“We’re here because we want to alleviate poverty,” said Katherine Kahn, the officer at the Gates Foundation overseeing the grant for the Illinois research. “What is it the farmers need, and how can we help them get there?”

One of the leaders of the research, Stephen Long, a crop scientist who holds appointments at the University of Illinois at Urbana-Champaign and at Lancaster University in England, emphasized in an interview that a long road lay ahead before any results from the work might reach farmers’ fields.

But Long is also convinced that genetic engineering could ultimately lead to what he called a “second Green Revolution” that would produce huge gains in food production, like the original Green Revolution of the 1960s and 1970s, which transferred advanced agricultural techniques to some developing countries and led to reductions in world hunger.

Improving photosynthesis

The research involves photosynthesis, in which plants use carbon dioxide from the air and energy from sunlight to form new, energy-rich carbohydrates. These compounds are, in turn, the basic energy supply for almost all animal cells, including those of humans. The mathematical description of photosynthesis is sometimes billed as “the equation that powers the world.”

For a decade, Long had argued that photosynthesis was not actually very efficient. In the course of evolution, several experts said, Mother Nature had focused on the survival and reproduction of plants, not on putting out the maximum amount of seeds or fruits for humans to come along and pick.

Long thought crop yields might be improved by certain genetic changes. Other scientists doubted it would work, but with the Science paper, Long and his collaborator — Krishna Niyogi, who holds appointments at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory — have gone a long way toward proving their point.

Much of the work at the University of Illinois was carried out by two young researchers from abroad who hold positions in Long’s laboratory, Johannes Kromdijk of the Netherlands and Katarzyna Glowacka of Poland.

No one plans to eat tobacco, of course, nor does the Gates Foundation have any interest in increasing the production of that health-damaging crop. But the researchers used it because tobacco is a particularly fast and easy plant in which to try new genetic alterations to see how well they work.

In a recent interview in Urbana, Kromdijk and Glowacka showed off tiny tobacco plants incorporating the genetic changes and described their aspirations.

“We hope it translates into food crops in the way we’ve shown in tobacco,” Kromdijk said. “Of course, you only know when you actually try it.”

Eyeing African staples

In the initial work, the researchers transferred genes from a common laboratory plant, known as thale cress or mouse-ear cress, into strains of tobacco. The effect was not to introduce alien substances, but rather to increase the level of certain proteins that already existed in tobacco.

When plants receive direct sunlight, they are often getting more energy than they can use, and they activate a mechanism that helps them shed it as heat — while slowing carbohydrate production. The genetic changes the researchers introduced help the plant turn that mechanism off faster once the excessive sunlight ends, so that the machinery of photosynthesis can get back more quickly to maximal production of carbohydrates.

It is a bit like a factory worker taking a shorter coffee break before getting back to the assembly line. But the effect on the overall growth of the tobacco plants was surprisingly large.

When the scientists grew the newly created plants in fields at the University of Illinois, they achieved yield increases of 13.5 percent in one strain, 19 percent in a second and 20 percent in a third, compared with normal tobacco plants grown for comparison.

Because the machinery of photosynthesis in many of the world’s food crops is similar to that of tobacco, theory suggests that a comparable manipulation of those crops should increase production. Work is planned to test that in crops that are especially important as dietary staples in Africa, like cowpeas, rice and cassava.

Two outside experts not involved in the research both used the word “exciting” to describe it. But they emphasized that the researchers had not yet proved that the food supply could be increased.

“How does it look in rice or corn or wheat or sugar beets?” said L. Val Giddings, a senior fellow at the Information Technology and Innovation Foundation in Washington and a longtime advocate of gene-altered crops. “You’ve got to get it into a handful of the important crops before you can show this is real and it’s going to have a huge impact. We are not there yet.”