PLANT PHYSIOLOGY , Vol 106, Issue 2 485-491, Copyright © 1994 by American Society of Plant Biologists
|
MOLECULAR BIOLOGY AND GENE REGULATION |
Cloning and Regulation of Flavonol 3-Sulfotransferase in Cell-Suspension Cultures of Flaveria bidentis
S. Ananvoranich, L. Varin, P. Gulick and R. Ibrahim
Plant Biochemistry Laboratory, Concordia University, Montreal, Quebec, Canada H3G 1M8
Flaveria spp. accumulate flavonol sulfate esters whose biosynthesis is
catalyzed by a number of position-specific flavonol sulfotransferases.
Although the accumulation of sulfated flavonols appears to be tissue
specific and developmentally regulated and to vary among related species,
little is known about the mechanism of regulation controlling the synthesis
of these metabolites. In the present work, we report the isolation of a
cDNA clone from Flaveria bidentis (pBFST3) encoding flavonol
3-sulfotransferase (F3-ST), which catalyzes the first step in the
biosynthesis of flavonol poly-sulfates. This clone (pBFST3) was expressed
in Escherichia coli and produced an F3-ST with high affinity for the
flavonol aglycones, quercetin, and its 7-methyl derivative, rhamnetin. In
addition, the synthetic auxin 2,4-dichlorophenoxyacetic acid was shown to
induce F3-ST enzyme activity and F3-ST mRNA transcript levels in cell
cultures of F. bidentis. The F3-ST mRNA levels increased within the first 3
h, reaching a maximum after 24 h of treatment, and remained elevated for up
to 48 h. Treatments with either quercetin 3-sulfate or quercetin
3,7,4[prime]-trisulfate reduced F3-ST enzyme activity in cell cultures but
had no effect on the transcript levels. These results are discussed in
relation to the putative role of flavonoid conjugates in the regulation of
auxin transport.
