Bioengineered Tomatoes Taste
A retooled gene in Endless Summer tomatoes controls ripening to
give better flavor and shelf-life.
A tasty new tomato boasts more of the hearty, vine-ripened flavor that's
often missing in its supermarket counterparts.
The bioengineered Endless Summer tomato is a result, in part, of work by ARS
and University of California at Berkeley researchers. They found, copied, and
rebuilt a gene that lets these tomatoes stay on the vine without softening and
spoiling. That means the high-tech fruit can develop more of the sugars and
acids that make a home-grown tomato taste so sweet and rich.
DNA Plant Technology Corporation (DNAP) of Oakland, California, licensed the
gene and used that research, plus the company's proprietary technology, to
create Endless Summer tomatoes. Earlier this year, the big, juicy tomatoes were
test-marketed in New York.
DNAP business development director Dave Rochlin estimates that they may be
on sale in supermarkets throughout the country by 1997.
Typically, supermarket tomatoes have to be harvested while they're green and
hard. That's so they won't bruise and rot on the long trip from grower to
Perhaps most important, they're picked before they can begin to form a
natural ripening hormone, ethylene. Once ethylenecolorless, odorless
gaskicks in, so do all the problems of perishability. Ethylene also
triggers natural ripening and spoilage of hundreds of other kinds of fruits and
vegetables, like bananas, melons, lettuce, and apples.
In Endless Summer tomatoes, the gene that would ordinarily help the plant
make ethylene is retooled, to squelch almost all ethylene production. Because
the tomatoes form virtually no ripening gas, there's no need to hurriedly
harvest immature fruit.
When exposed to ethylene gas in the warehousethe procedure used to
ripen commercial tomatoesEndless Summer tomatoes soften, turn red, and
stay plump and fresh for about 4 weeks. That's 2 weeks longer than most grocery
"The longer shelf-life," says DNAP's Rochlin, "means we can
ship a consistent supply of these superb tomatoes."
ARS plant physiologist Athanasios Theologis at the ARS/University of
California Plant Gene Expression Center, Albany, and co-researcher Takahide
Sato isolated and cloned the ripening gene. Normally, the gene cues tomatoes to
produce an enzyme called ACC synthase. To make ethylene, plants need that
Theologis and Sato did the work in 1989 and applied for a patent. In lab and
greenhouse experiments that followed, Theologis and other colleagues blocked
99.5 percent of all ethylene production in about 100 tomatoes by remaking the
ACC synthase gene.
His team reported their success in an article that garnered the cover of
Science, one of the world's leading research journals.
DNAP and two other companies, Calgene, at Davis, California, and Monsanto,
in St. Louis, licensed the gene. But DNAP is the first to market a
gene-engineered tomato that's derived from the Albany work. The DNAP license
permits the gene's use not only in tomatoes, but in about a dozen other produce
section favorites as well.
DNAP's bioengineered bananaone that won't turn brown and squishy
before you've had a chance to put it on your breakfast cerealis already
in the works. By Marcia Wood, ARS.
Theologis is at the USDA-ARS
Gene Expression Center, 800 Buchanan Street, Albany, CA 94710; phone (510)
559-5911, fax (510) 559-5678.
"Bioengineered Tomatoes Taste Great" was
published in the July
1995 issue of Agricultural Research magazine.