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Modified tomatoes have longer vine lives and higher nutritional value


Scientists have inserted a gene from yeast into the tomato, and the result is a plant whose fruit stays longer on the vine and has an extended shelf life. To the researcher's surprise, the modified fruit also produces increased amounts of a natural antioxidant, called lycopene, which is associated with lower rates of certain cancers and heart disease in humans.

Lycopene gives ripening tomatoes—one of the traditional fruits of summer—their ruby red color. The transgenic tomatoes have 200 to 300 percent more lycopene than unmodified plants, according to the findings reported in Nature Biotechnology.

Red fruit from transgenic tomato line 579HO.

The researchers inserted a yeast gene, called ySAMdc, into tomato plants. They engineered the gene so that it would be activated in the fruit but not the rest of the plant.

Tomatoes with the gene have more polyamines—a growth substance—and this leads to their longer fruit lives on the vine. They also have longer shelf lives, according to Autar K. Mattoo, of the USDA-ARS Vegetable Laboratory in Beltsville, Maryland, who led the project.

The relatively small genome of the tomato, along with the ability of researchers to manipulate its genes in the laboratory, "make the plant an ideal model for genetic research," says Mattoo. The tomato, he suggests, is complementary to the mustard weed Arabidopsis and would be a useful species for investigating how fruit ripens.

In Mattoo's view, tomatoes with a yeast gene should not pose a problem for consumers: "We have used yeast for centuries to make bread, yogurt and wine."

Remarking on the study's surprise finding, the authors of a commentary accompanying the study observe that "serendipity still has a large part to play" in genomics research. "Often, it seems, approaches in one area yield fruitful discoveries in others," write Greg Tucker of the University of Nottingham in Loughborough, U.K., and Graham Seymour of Horticulture Research International, Wellesbourne, Warwick, U.K.

The father of modern tomato genetics, Charles Rick, died last month. Rick's genetic and evolutionary studies greatly contributed to mapping and understanding the tomato genome. He established the Tomato Genetics Research Center at the University of California, Davis, which houses the largest known collection of tomato seeds.

See related GNN articles
»Modified tomato plants silence the genes of invaders
»Researchers transform tomato with Petunia gene

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Mehta, R.A. et al. Engineered polyamine accumulation in tomato enhances phytonutrient content, juice quality, and vine life. Nat Biotechnol 20, 613-618 (June 2002).
Tucker, G. & Seymour, G. Life on the vine. Nat Biotechnol 20, 558-560 (June 2002).

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