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10 Agricultural Research/January 2005
Whether it’s a fragrant slice of freshly bakedartisan bread or a perfectly prepared pasta en-tree, most of us eat foods made from wheat flourevery day. The quality of that flour is due, inlarge part, to the work of hundreds of differentproteins that perform specialized tasks insidethe wheat kernel, or grain.
Discovering more about the work of theseproteins—and how they’re affected by the heat,soil nutrients, and other environmental condi-tions in which the plant is grown—might lead
to even better flours for tomorrow. A top-quality flour can makea bread or a pasta remarkable instead of just ordinary.
Gluten proteins are the most abundant and most studied.Researchers already know that these proteins have a premierrole in influencing a flour’s quality.
In contrast, scientists know very little about wheat kernels’so-called metabolic proteins, which occur in much smalleramounts. It is known, however, that these mostly mysteriousproteins are essential to a kernel’s growth. For example, wheatplants need metabolic proteins to form the gluten proteins andto make starch. Gluten and starch are the main components offlour.
Protein Profilers Sleuth Metabolic ProteinsIn Albany, California, ARS plant physiologist William J.
Hurkman is working with Charlene K. Tanaka, also a plantphysiologist, and chemist William H. Vensel to uncover moredetails about the biochemical chores carried out by these less-abundant wheat proteins. The scientists are in the ARS WesternRegional Research Center’s Crop Improvement and UtilizationResearch Unit.
Working with kernels from wheat plants grown in their re-search greenhouses, the scientists separated metabolic proteinsfrom one another with a laboratory technique called two-dimensional gel electrophoresis.
Another technology, mass spectrometry, gave them a distinctprofile of each protein. Using computers, they matched manyof these protein profiles to those in other plants. They locatedthose other profiles by searching research databases posted onthe World Wide Web. With this approach, the researchers
Scientists ona Roll WithWheat ProteinStudies
Flour Power for Tomorrow
Using two-dimensional gelelectrophoresis and sophisticatedcomputer software, plant physiologistsCharlene Tanaka and Bill Hurkmancompare protein patterns in wheatendosperm during grain development.
A wheat grainis made upmostly ofstarchyendosperm. Inthis close-up,the extrudedendospermappears as awhitish mass atthe tip of thegrain in thecenter of thehead.
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11Agricultural Research/January 2005
Whether metabolic or gluten, all wheatproteins are the product of genes. Susan B.Altenbach, a biologist with the ARS group, isstudying genes that cue the wheat plant to makekernel proteins. To do this, she’s using a tech-nique called microarray analysis. This leading-edge technology makes it possible to studythousands of wheat genes, conveniently posi-tioned on a single, 1-by-3-inch glass slide.
Analyzing kernel proteins in their end prod-uct—wheat flour itself—is another tactic that’srevealing more about them. Plant physiologistFrances M. DuPont of the Albany team hasshown that the amounts of heat and fertilizergreenhouse wheat plants were exposed to affect-ed levels of certain kernel proteins. One outcome:lower-quality flour, resulting in doughs that wereunable to withstand the rigorous mixing that’spart of making bread.
The experiments highlight the importance ofpinpointing kernel proteins’ precise roles andusing what’s discovered to breed better wheatplants for the future. The superior flours theseplants produce should please not only growersand millers, but also the people working in com-mercial or home kitchens to prepare delicious,wheat-flour-based foods for us.—By MarciaWood, ARS.
This research is part of Plant Biological andMolecular Processes (#302) and Quality andUtilization of Agricultural Products (#306), twoARS National Programs described on the World
Wide Web at www.nps.ars.usda.gov.William J. Hurkman, Charlene K. Tanaka, William H. Vensel,
Susan Altenbach, and Frances M. DuPont are in the USDA-ARS Crop Improvement and Utilization Research Unit, West-ern Regional Research Center, 800 Buchanan St., Albany, CA94710; phone (510) 559-5750, fax (510) 559-5818, [email protected], [email protected], [email protected], [email protected], [email protected]. ★
identified more than 200 wheat kernelproteins and grouped them by the tasks theylikely perform, ranging from storingcarbohydrates to protecting the kernelagainst insects.
The researchers also tested kernels, fromthe greenhouse plants, in two differentgrowth stages. They found changes, overtime, in the relative abundance of proteins.For example, certain metabolic proteinswere more abundant in the early days ofkernel growth than in the final weeks. Thischronology of proteins at work inside wheatkernels is the kind of detail that could leadto improved flours.
A Catalog of Kernel ProteinsThe analysis of hundreds of wheat-
kernel proteins is what’s newly describedas “proteomics,” the comprehensive studyof the function, structure, and location ofproteins. The catalog of proteins in wheatkernels that the scientists are compiling isa proteome, just as a genome is a directoryof all genetic material in a plant or animal.
Similar work has been done at other labsto identify proteins and their functions inwheat, barley, and alfalfa grains, forinstance. But the California investigatorsare likely the first to delve this deeply intothe roles and changing ratios of the lesser-known wheat-kernel proteins.
The ARS research led to new collaborations with Universi-ty of California at Berkeley researcher Bob B. Buchanan andcolleagues to learn more about other aspects of wheat proteins.
Tracking Proteins to Their Gene OriginsAs part of uncovering even more pieces of the wheat pro-
tein puzzle, scientists are tracking the proteins’ gene origins,as well as how proteins affect flours.
Plant physiologist Bill Hurkmanharvests a wheat head from plantsgrown in a climate-controlledgreenhouse at ARS’s WesternRegional Research Center.
Chemist William Venselloads a plate of wheatendosperm protein digestsinto an autosampler forprotein analysis.
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