Lab-Built Wheat Gene May Raise Dough
Yeast-raised breads will benefit from research on the genes in wheat and
wheats wild relatives that produce high-molecular-weight
gluteninsproteins that are important to baking quality.
Wheat plants of the future might provide grain for designer flours that
yield delicious, wholesome new breads, pastas, and other appetizing foods. And
giving some of wheat's flour genes to other kinds of grains--barley, oats,
corn, rye, or rice, for instance--could lead the way to innovative, versatile
flours from these wheat relatives, as well.
These futuristic flours are the target of genetic engineering experiments
conducted by Agricultural Research
Service scientists at the Western Regional Research Center in Albany,
California. They are investigating proteins unique to wheat flour, called
high-molecular-weight glutenins. These glutenins are critical to making strong
dough. For dough, strength is an asset because it leads to high-quality
Strong dough, explains geneticist Olin D. Anderson, is able to trap tiny
bubbles of carbon dioxide gas formed naturally by yeast during mixing and
rising. Bubbles enable dough to rise, helping form high, light, loaves. Dough
strength and the ability to contain gas bubbles is known as viscoelasticity.
Wheat with a large amount of certain high-molecular-weight glutenins yields
flour that produces stronger dough, larger bread loaf sizes, and light,
finer-textured breads. Recently, Anderson and geneticist Ann E. Blechl became
the first to use genetic engineering to boost the amount of
high-molecular-weight glutenins in wheat kernels and the flour ground from
those kernels. They did this by using a gene gun to move copies of a lab-built
gene into wheat cells.
The gene gun fired gold particles coated with genes that cue wheat plants to
manufacture more glutenins. So far, greenhouse plants with high levels of
high-molecular-weight glutenins retained the trait through successive
Geneticist Kent McCue examines the growth of wheat plants that have received a
gene for modifying starch production.
The researchers now want to fine-tune this strategy for more precise
control over wheat flour's glutenin levels. With colleagues from Australia's
Commonwealth Science and Industrial Research Organization in Sydney, they are
testing flours made from kernels harvested from these experimental plants.
No one knows exactly how high-molecular glutenins workonly that they're
vital for strong doughs and great breads. To reveal more about the inner
workings of these proteins, Anderson is building and testing modified versions
of other genes that control production of glutenins.
Some of these re-tooled genes are longer versions of the naturally occurring
ones. Their central sections have more repeats of a portion of genetic material
thought to be key to viscoelasticity. Anderson's tests showed that increasing
the copies of those portions of the genes increases dough-mixing time. That's a
boon to bakers, because increased dough-mixing time is a key indicator of dough
Scientists have anticipated that using genetic engineering to change a
wheat-flour protein could change the character of the resulting dough. The
Albany team was the first to succeed in doing that--using biotechnology.
Wheat glutenin genes inserted into other grains may lead to unique,
healthful products impossible to make today. Moving one or two of wheat's
high-molecular-weight glutenin genes into barley, for example, might open the
door to popular new products from barley flour.
Currently, American-grown barley is used mainly for malting and animal feed.
Barley flour lacks the high-molecular-weight glutenins that wheat flour boasts.
Although barley has flour proteins somewhat similar to those in wheat, barley
flour does not make a similar viscoelastic dough.
Now, senior lab technician Jeanie Lin, who is with the Albany team, has
succeeded in moving wheat glutenin genes into barley plants. And, says Lin,
some of those plants produced kernels with good levels of wheat glutenin
In another venture, Minnesota scientists using wheat glutenin genes
furnished by the Albany researchers have produced oat plants with the borrowed
wheat genes inside. David A. Somers led that work at the University of
Minnesota. He used a technique that he, Kimberly A. Torbert, and geneticist
Howard W. Rines of the ARS Plant Science Research Unit in St. Paul, Minnesota,
developed for genetically engineering oats.
At the ARS Western Regional Research Center in Albany, California, geneticist
Olin Anderson uses a sample-handling robot to search more efficiently for new
Like the barley foray, oat experiments may lead to development of tasty new
foods that rely on new oat flours. Today's oats are grown mostly for animal
feed or processed into breakfast cereals and other foods for people.
The glutenin experiments with wheat target the protein-rich portion of wheat
flour. But flour's other main component--starchmight also be re-worked through
genetic engineering into a more marketable product.
Wheat starch is composed of molecules known as amylose and amylopectin.
Wheat flour low in amylose, for example, is desirable for noodlemaking because
it improves noodle texture. Reduced-amylose flours may also improve dough for
frozen foods like pizza crusts or ready-to-bake breads by helping maintain
Scientists suspect that boosting the amount of amylopectin in starch may
concurrently reduce the amount of amylose, resulting in a value-added,
Geneticist Kent F. McCue, working with Anderson, isolated two genes that
direct wheat to make amylopectin-producing enzymes known as starch-branching
enzyme I and starch-branching enzyme II. McCue and Anderson used starch genes
from corn to isolate the two in wheat. With the wheat genes now in hand,
genetic engineers might soon be able to increase the ratio of amylopectin to
Modifying wheat starch could also make it more suitable for any of hundreds
of industrial uses ranging from pastes to papers to textiles. By
Marcia Wood, Agricultural
Research Service Information Staff.
For more information on U.S. Patent No. 5,650,558, "Glutenin
Genes and Their Uses," Patent Application No. 08/785,716,
"Altering Dough Viscoelasticity With Modified Glutenins," or
Patent Application No. 60/059,257, "Modification of Starch Branching
Patterns and Chain Length Distribution Via Transformation with Starch Branching
Enzymes," contact Olin D.
Crop Improvement and
Utilization Research Unit, Western Regional Research Center, 800 Buchanan
St., Albany, CA 94710; phone (510) 559-5773, fax (510) 559-5777.
"Lab-Built Wheat Gene May Raise Dough Quality" was
published in the November 1998 issue of Agricultural Research magazine.
to see this issue's table of contents.