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ALL FLOWERING PLANTS LINKED TO 200 MILLION YEAR OLD ANCESTOR
COLLEGE STATION -- Blades of bermuda and bunches of broccoli appear to
have little more in common than color. But a new study has found that
they -- and all flowering plants in the world -- stem from a common
ancestor that existed perhaps 200 million years ago.
The finding, reported in the December issue of Nature Genetics,
means that breeders who are trying to develop better plants may soon
have a much larger storehouse of genetic material to use.
"Down the road, we may be able to treat the genomes of all crops as
one," said Dr. Andrew Paterson, Texas Agricultural Experiment Station
molecular biologist and lead investigator on the project. "If we know
the function of a gene in cotton, we will be able to infer what that
gene's function in grain sorghum is."
Same goes for turfgrass, cactus, oak trees, grape vines and any of
the other 250,000 species of plants classified on Earth, according to a
United Nations report on biodiversity.
Paterson and colleagues last year were able to link the world's
most important cereal grains -- rice, corn and sorghum -- to a common
ancestor that grew about 65 million years ago, according to Science
magazine. That was significant, but all of those crops are from the
same family -- grasses, or monocots. The new research links the grass-
type plants with the broadleafs, or dicots, to one ancestor that
existed sometime between 130 million and 200 million years ago,
simultaneously with the dinosaurs.
"The differences among plants are relatively small compared to the similarities," Paterson said.
The discovery comes more than a year after Paterson's group began
analyzing DNA for four plants: the Arabidopsis -- a small flowering
weed that is commonly used by researchers but has no other commercial
value -- broccoli, sorghum and cotton. Arabidopsis and broccoli are
closely related broadleafs, cotton is a more distant dicot (broadleaf)
and sorghum is a grass.
The researcher put DNA sequences for which the genes were already known into a database
to see if those sequences would correspond to any other known set, then
determined where those genes existed on the chromosomes of each plant.
"If the genes were close to one another in the Arabidopsis DNA,
then we looked to see if they also were close in the sorghum more often
than we would expect by chance," Paterson explained. The answer was
repeatedly "yes."
All plants have a basic set of genes that are similar and function
in the same way, such as by fixing carbon into sugar, incorporating
nitrogen into protein and generally doing the things that "make a plant
a plant," Paterson said. This research shows that not only do the
genesfunction in the same ways many of them also are int he same orders
along the chromosomes.
Considering that the smallest plant genome, Arabidopsis, is
estimated to include 25,000 genes, this is very important information
for geneticists. Knowing the order of genes along the chromosome
provides researchers with a "genetic map," essentially like a roadmap,
and allows them to engineer improved crops quickly and efficiently.
"Plant breeders eventually will be able to take advantage of an
enormous body of information to assist with developing better
varieties," he said. "If we can find a gene for fiber quality affecting
the development of hairs in Arabidopsis, we know where to go look for
the corresponding gene which might improve fiber quality in cotton, for
example." Grass genes could be used in broadleaf plants as well, he
said.
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