WINKEL-SHIRLEY, BRENDA. Department of Biology, Virginia Tech, Blacksburg, VA 24061-0406. - Molecular genetics and control of anthocyanin expression.
The flavonoid pathway leading to anthocyanin biosynthesis has been
well-characterized in a number of model systems, including maize,
petunia, snapdragon and, more recently, Arabidopsis. Genetic
approaches have identified many of the regulatory and structural genes
required for the synthesis of these important plant pigments. In all
species examined to date, control of the flavonoid pathway is known to
occur, at least in part, at the level of transcription. In addition,
there is evidence for regulation of this pathway at the level of the
biosynthetic enzymes. Of particular interest to my research group is
the possibility that flavonoid enzymes are organized as a multi-enzyme
complex. This type of metabolic organization offers the potential not
only for enhancing the efficiency of flavonoid biosynthesis, but also
for regulating the flux of intermediates into branch pathways leading
to anthocyanins and other endproducts. We have recently demonstrated
specific interactions between flavonoid enzymes in Arabidopsis using
co-immunoprecipitation, affinity chromatography, and two-hybrid
analysis. Immunocytochemistry is providing further evidence for the
co-localization of these enzymes at specific subcellular sites in root
cells, consistent with biological roles of some flavonoids in auxin
transport and the wound response. Additional approaches, including the
expression of scFv antibodies in transgenic plants and homology
modeling of the structures of various flavonoid enzymes, are being
used to identify protein domains involved in the assembly and
positioning of this system within the cell. Analysis of a series of
Arabidopsis mutants has also provided evidence that intermediates in
flavonoid biosynthesis function in a feedback control system. Our
studies indicate that plants use a diversity of mechanisms to control
the synthesis of flavonoid products, including anthocyanins.
Key words: Arabidopsis, chalcone isomerase, chalcone synthase, flavonoid