Wheat Texture is Determined by Two ProteinsBy
Kathryn Barry Stelljes
May 26, 1998
Wheat breeders are a step closer to developing super-soft or other
custom-designed wheats, thanks to a key discovery by
Agricultural Research Service scientists.
That could mean cookies that melt in your mouth better or new kinds of pasta
Researchers at the ARS Western
Wheat Quality Laboratory in Pullman, Wash., identified the molecular basis
for one of wheat's most important qualities: texture, known as hardness or
softness. Bakers use hard wheats to make bread and soft wheats for cookies and
Scientists have known since the 1970's that one gene controls wheat texture.
The gene directs wheat to make proteins called puroindolines. But until now,
they haven't understood the relationship between puroindolines and hardness.
ARS researchers found that specific types of puroindolines (known as pinA
and pinB) correlate perfectly with wheat texture.
All soft wheats, including wheat's wild ancestors, have pinA and a specific
form of pinB. This pinB has glycine as the 46th amino acid in the protein.
Scientists tested more than 200 North American hard wheats. Most differ from
soft wheat by a single amino acid, serine, as the 46th amino acid in pinB. The
rest of the hard wheats have the glycine pinB but don't have pinA.
Breeders can use this information to develop new varieties with specific
puroindoline combinations, using either traditional breeding or biotechnology.
By adding extra genetic copies of puroindolines, for example, they might
create a super- soft wheat to make new kinds of cakes and cookies. That's
because millers could grind the softer wheat to a finer flour than is possible
today without damaging the wheat's starch, a common milling problem.
A report on these findings appears in today's issue of the Proceedings
of the National Academy of Sciences (abstracts are available at http://www.pnas.org).
Scientific contact: Craig Morris, USDA-ARS Western Wheat Quality
Laboratory, Pullman, WA 99164, (509) 335-4055, fax (509) 335-8573,