CALIFORNIA
USDA-ARS WESTERN REGIONAL RESEARCH CENTER
Wheat Biotechnology and Wheat Genetic Engineering Groups, 800 Buchanan St., Albany, CA 94710, USA.
Michael Gitt.
Our major interests are the molecular biology and bioengineering
of wheat seed components, including the seed storage proteins
(prolamines), starch, and exogenous molecules such as those hypothesized
to confer fungal resistance.
Personnel. The directors of these projects are Olin D.
Anderson and Ann Blechl, with assistance from Barbara Dowdle-Rizzo,
Michael Gitt, Phyllis Han, Cheryl Hsia, Hahna Kang, Lance Larka,
Gerard Lazo, Jeanie Lin, and Pat Okubara.
Transgenic studies. Certainly one of the major research
interests in the lab is to generate transgenic wheat with a host
of exogenous genes. We have transformed Dy10, Dx5 (implicated
in good dough quality), and hybrid Dy10:Dx5 genes with interesting
results. Some resultant lines exhibit suppression of one or more
of the endogenous glutenins, although some lines are not suppressed
at all. A marked variation in the amount of exogenous glutenin
expressed also was observed.
Starch metabolism transgenes. We have isolated several of the genes involved
in wheat starch biosynthesis. Several of these, along with antisense
constructs, have been introduced into wheat, and we are developing
the lines at this time.
Fungal resistance transgenes. Several candidate genes have
been obtained that we hope can confer resistance to wheat upon
transformation and expression. Under the control of the maize
ubiquitin promoter these genes have been transformed into wheat,
and several positive lines have been obtained. We are now collecting
material for the experimental challenge with the fungus, to be
done in collaboration with another laboratory.
Structurefunction studies. We have generated several mutants
of a synthetic version of the glutenin Dx5, which is highly expressed
in E. coli. These mutations are in amino acids hypothesized
to play a central role in glutenin intermolecular interactions
responsible for dough viscoelasticity. We are now expressing large
quantities of these mutants for use in mixing experiments.
Prolamine gene structure and evolution. We have sequenced
the upstream and downstream regions of the genes encoding Ax,
Ay, Bx, By, Dx, and Dy glutenins. These flanking sequences provide
information on the evolution of the various glutenin alleles and
suggest new control sequences that could prove useful in future
transgenic work. We also have isolated and sequenced several gliadin
genes, including the discovery of new classes of gliadins.
Wheat genomics. The lab is still maintaining the GrainGenes
database (http:// wheat.pw.usda.gov) that permits web-based homology
searches to wheat, oat, barley, rice, sugarcane, maize, and noncereal.
Features include color- coded EST (expressed sequence tag) graphics
that are quickly interpreted.
Wheat probe repository. We are continuing service to the
cereal research community by banking and partially characterizing
all clones that we and others provide. We also make these clones
available for the entire research community. This past year, we
distributed over 3,500 individual clones. Clones can be ordered
by contacting probes@pw.usda.gov
Wheat est (expressed sequence tag) database. Large throughput
sequencing in our lab of endosperm cDNAs by the use of the ABI
310 sequencer and, lately, a Beckmann CEQ 2000, has yielded 2,500
clone sequences in the past year. Approximately 1.25 Mb of independent
sequence has been added to the database. To make future sequencing
productive, we are now focusing on methods to select only nonredundant
EST clones for further characterization.