College Station, Texas
November 20, 2006
A scientific method used to
explore cancer and HIV cures now has been successfully used by
agricultural researchers in the quest to develop food for the
world's hungry.
"The exciting finding is that
we have been able to reduce gossypol – which is a very toxic
compound – from cottonseed to a level that is considered safe
for consumption," said Dr. Keerti Rathore,
Texas Agricultural
Experiment Station plant biotechnologist. "In terms of human
nutrition, it has a lot of potential." The cottonseed from these
plants meet World Health Organization and U.S. Food and Drug
Administration standards for food consumption, he said,
potentially making the seed a new, high-protein food available
to 500 million people a year.
The work, announced today (Nov.
20) in the Proceedings of the
National Academy of Sciences, was done by Rathore and a team
of scientists from the Experiment Station, Texas A&M University
and the U.S. Department of Agriculture's Southern Plains
Research Center in College Station.
Gossypol naturally occurs
within the glands in all the above-ground parts of the cotton
plant including the seed. Rathore said the "beauty of this
project" is that the gossypol has been reduced only in the
cottonseed -- where the high levels of protein are packed -- but
not in the rest of the plant where the compound serves as a
defense against insects and disease.
The team used RNAi, or
technology that can "silence" a gene. This enabled them to
target the gossypol gene only in the cottonseed but let the gene
express itself in the rest of the plant. The discovery of RNAi
is what landed the Nobel Prize for Medicine this year for U.S.
scientists Andrew Z. Fire and Craig C. Mello.
"What we have done is use this
technology to selectively inhibit a gene that codes for an
enzyme that is involved in the gossypol biosynthetic pathway in
the seed, " Rathore said.
Cotton fibers have been spun
into fabric for more than 7,000 years. For most of that time,
products from the fuzzy seed that is extracted in the fiber
process have been edible only for cattle. They can tolerate
gossypol only after digesting it through the four compartments
of their stomachs.
"Very few people realize that
for every pound of cotton fiber, the plant produces 1.6 pounds
of seed," Rathore pointed out. "The world produces 44 million
metric tons of cottonseed each year. Cottonseed typically
contains about 22 percent protein, and it's a very high-quality
protein."
In all, about 10 million metric
tons of protein are contained in that amount of seed, he said.
Decades ago, California and
Texas researchers were able to breed cotton varieties that
contained no gossypol glands throughout the plant. But glandless
varieties were a commercial failure, Rathore said, because the
lack of any gossypol made the plants a delicious treat for
insects and diseases.
Processes have been developed
to extract gossypol, making the oil available for human
consumption but at great expense, he said. Plus, the meal that
is left after the oil is removed still contains the gossypol and
thus is not edible for humans, or for pigs, chickens or turkeys.
Plants with the new trait
developed by the team could make the plant more valuable both as
a fiber and a food crop.
"One could utilize the
cottonseed either directly as food if there is no gossypol or as
feed for livestock," he said.
The food value of the cotton
crop may be for countries "where there are small farmers who
grow cotton, and if they could use the seed they could get much
more value from it," Rathore noted.
He believes food products
ultimately could be developed from the cottonseed of these new
plants. Though the glandless cotton varieties bred by Experiment
Station researchers in the late 1970s and 1980s suffered from
insects and disease, one of the food products -- TAMUnuts --
made from the seed of these plants could be eaten by humans.
This discovery will yield not
just one new variety, but rather "a new trait that can be bred
into any good commercial variety, and the trait should be
maintained generation after generation," Rathore said.
The researchers have been
successful in maintaining the trait through three generations in
lab work. The next step will be to screen for the best plants
from the many lines they have produced, then grow plants with
the trait in a greenhouse.Field demonstrations will follow that,
he said.
He estimates at least another
decade in the development of cotton varieties for widespread
commercial production. |