Dr.
Virginia Walbot
Stanford
University
Department
of Biological Sciences
As a lover of striped flowers from an early
age, Virginia Walbot was drawn to the intricacies of the striped and speckled
seeds of Indian corn. A large fraction of her nearly 200 publications deal
with maize and the colorful Bronze-2 gene (Bz-2), encoding a glutathione-S-transferase
involved in the last step of anthocyanin pigmentation. This is one
of a family of enzymes essential for sequestering many compounds in vacuoles.
With a B.A. in biology from Stanford, Dr. Walbot worked with Ian Sussex at Yale on molecular aspects of plant embryogenesis
for M. Phil. and Ph. D. degrees. After a postdoctoral period at the
University of Georgia with Leon Dure, she was a faculty member at Washington
University in St. Louis before returning to Stanford where she is a professor
in the Department of Biological Sciences. She began working with
maize while in Missouri, collaborating with Ed Coe at the University of
Missouri and spending time with Barbara McClintock at Cold Spring Harbor.
Dr. Walbot is an Adjunct Progessor of Agronomy at the University of Missouri
and a nonresident Fellow of the Noble Foundation (Ardmore, OK) in addition
to her position at Stanford. She has served on editorial boards of a number
of journals, most notably as Associate Editor of Annual Review of Plant
Physiology and Plant Molecular Biology for 16 years. She is active in a
number of societies including the American Society for Cell Biology, AAAS,
AIBS, Genetics Society, and International Society for Plant Molecular Biology.
A broad theme of Dr. Walbot's research is
the interplay of environment and development in the life cycle of plants.
A transposable element, Mutator, is responsive to the developmental stage
of the plant and to UV-B exposure and can be used to monitor the influence
of environment on the pace of genetic change. Regulation of the excision
and transposition of Mu elements appears to be controlled at the post-transcriptional
level and efforts are directed to pin down the details of the responsible
processes. One particular construct allows rescue by plasmids to produce
RescueMu elements.
RescueMu elements provide a foundation for a ten laboratory consortium
funded by NSF as the Maize Gene Discovery Project with Dr. Walbot as PI.
Her lab has sequenced ~80,000 ESTs. By sequencing Mu insert sites, preferentially
found in traditional genes, 30,000 tagged maize genes should be obtained
within two years.
Much of the developmental work in Dr. Walbot's
laboratory uses the Bz-2 locus to report the activity of Mu elements.
Color patterns help deduce the developmental fate of lineages of cells
to see when Mu inserts into and excises from genes. A surprising biochemical
finding is that glutathione-S-transferase serves as a facilitator for the
last step of anthocyanin biosynthesis by delivering anthocyanin to a specific
tonoplant pump. Only when it is sequestered in the vacuole does the anthocyanin
yield its usual color. Some phytoalexins, disease resistance substances,
are similar to anthocyanins and are similarly transported. A functional
Bz-2 gene in a dicot species indicates that anthocyanin synthesis is an
ancient process.
Colloquium:
"Maize Gene Discovery
with ESTs and Mu Transposon Tagging"