- ITHACA, NY - The fruits of
genetic research are about to ripen: Scientists at the U.S. Department
of Agriculture (USDA) and the Boyce Thompson Institute for Plant Research,
Inc. (BTI), located on the campus of Cornell University, have discovered
a gene that controls ripening in tomatoes.
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- This means that tastier, more-nutritious grocery-store
tomatoes are not far behind, say the researchers in an article in the
latest
issue of the journal Science (April 12, 2002), titled "A MADS-box
gene necessary for fruit ripening at the tomato ripening-inhibitor (rin
) locus."
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- "For understanding tomato ripening and eventually
taste, this could be the Holy Grail," says Jim Giovannoni, a project
scientist with the USDA and also with BTI.
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- MADS refers to a family of genes (the name is an acronym
formed from the initials of the four original members of the family). More
than 100 MADS-box sequences have been found in species of microbes, animals
and plants, and most play important roles in developmental processes. Most
prominent, the MADS-box genes in flowering plants are the "molecular
architects" of growth.
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- Giovannoni and his colleagues have found two tandem
MADS-box
genes, one a ripening gene, the LeMADS-RIN (or rin for short), and the
other the LeMADS-MC gene, which controls the development of the sepal --
the collar of pointy green leaves at the top of tomatoes. Finding these
genes provides the first molecular insight into a non-hormonal way to ripen
fruit, he says.
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- The shelf life of tomatoes was lengthened by the
discovery
in the early 1960s, by Henry Munger, Cornell professor of plant breeding,
of a mutant tomato plant containing what Giovannoni and his group now have
shown to be a defect in the rin gene. Munger crossed this mutant plant
with normal tomatoes, allowing the fruit to reach full size while slowing
the ripening process. Today, this hybrid is commercially ubiquitous. But,
says Giovannoni, in order to be fresh for the supermarket, these tomatoes
are harvested while they are still firm and unripe so they can survive
the rigors of shipping and have an extended shelf life. As a result, tomato
flavors, typical of homegrown fruit, do not get a chance to develop on
the vine, and consumers complain about their blandness.
-
- The discovery of the rin gene provides a way to keep
the tomato on the vine a little longer so that it develops more nutrients,
color and taste, Giovannoni says. And yet it is still firm enough for
shipping,
and with a good shelf life. As a bonus, the longer a tomato remains on
the vine, the more lycopene (an antioxidant that inhibits cancer and heart
disease) is produced.
-
- Giovannoni's research team also has been able to moderate
the ripening process, creating tomatoes that ripen at fast, medium or slow
speeds. Using a procedure called "antisense," the researchers
take the rin gene and invert it. This effectively shuts off the normal
gene and, in this case, slows the tomato's ripening process. The procedure,
says Giovannoni, also should work with strawberries, bananas, bell peppers
and melons, in addition to many other fruits for which shelf life and
softening
are problems. This, says Giovannoni, could reduce the use of ethylene to
kick-start ripening after fruit has been shipped to the warehouse.
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- Giovannoni's co-authors of the Science paper are: Julia
Vrebalov, research associate at the USDA-Agricultural Research Service's
Plant, Soil and Nutrition Laboratory and at BTI; Ruth White, a researcher
at the USDA and BTI; Diana Medrano, researcher, BTI; Rachel Drake, of
Syngenta;
Wolfgang Schuch, formerly of Syngenta, now with CellFor, Inc.; and former
members of the Giovannoni lab, Diane Ruezinsky, now with Monsanto, and
Veeraragavan Padmanabhan, now with Pioneer Seed.
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- Early work on the research was conducted by Giovannoni
at the Texas Agricultural Experiment Station. The research was funded by
the USDA-National Research Initiative plant genome grant, the National
Science Foundation and Syngenta.
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- Related World Wide Web site -- The Boyce Thompson
Institute
for Plant Research, Inc: http://bti.cornell.edu
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- Original news release: http://w
ww.news.cornell.edu/releases/April02/TomatoGene.bpf.html
-
- Note: This story has been
adapted from a news release issued by Cornell University for journalists
and other members of the public. If you wish to quote from any part of
this story, please credit Cornell University as the original source. You
may also wish to include the following link in any citation:
-
- http://www.sciencedaily.com/releases/2002/04/020412075717.htm
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