Gene Boosts Tomato's Color, But May Make It Less Tasty

FRIDAY, June 29 (HealthDay News) -- The gene mutation that makes a tomato uniformly red is the same trait that reduces its sweetness, researchers have found.

A team from the Boyce Thompson Institute (BTI) for Plant Research at Cornell University, the U.S. Department of Agriculture (USDA), and the University of California, Davis discovered that the mutation, which is found in most supermarket tomatoes, reduces the amount of sugar, carbohydrates and carotenoids in the fruit.

"Practically, it is a very important trait," one of the study's senior authors, James Giovannoni, a plant molecular biologist with BTI and the USDA Agricultural Research Service, said in a Cornell news release. "It's a gene that, whether you realize it or not, most of your tomatoes have." But this trait also cuts the tomatoes' levels of sugars and nutrients.

Naturally ripened tomatoes have uneven patches of darker green and different shades of red. In the 1920s, however, commercial breeders found a natural mutation in tomatoes that causes them to ripen evenly from one shade of green to one shade of red. This mutation, the researchers explained, is evident in most tomatoes sold in grocery stores.

In conducting the study, the scientists pinpointed the location of the "uniform-ripening" gene. Using this location, the researchers uncovered the gene coding for the protein that controls photosynthesis levels in tomatoes.

Although leaves are the primary site of photosynthesis in plants, the study authors pointed out that developing tomato fruit can contribute up to 20 percent of their own photosynthesis, producing high sugar and nutrient levels when fully ripe. The uniform-ripening mutation, however, removes this protein, which reduces the tomatoes' sugar levels, they found.

"This is an unintended consequence," noted Giovannoni. "Producers currently don't get a penny more for [flavor] quality."

Producers who care more about taste than appearance should ensure their plants are mutation free, the researchers suggested in the report published in the June 29 issue of the journal Science.

The study "is a rare chance to translate scientific findings to the real world," said Ann Powell, a research biochemist who led the UC Davis team's efforts on the research. "It provides a strategy to re-capture quality characteristics that had been unknowingly bred out of modern cultivated tomatoes," she noted in the news release.