PLANT PHYSIOLOGY , Vol 110, Issue 1 79-88, Copyright © 1996 by American Society of Plant Biologists
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GENE REGULATION AND MOLECULAR GENETICS |
Auxin-Sensitive Elements from Promoters of Tobacco GST Genes and a Consensus as-1-Like Element Differ Only in Relative Strength
B. J. van der Zaal, FNJ. Droog, F. J. Pieterse and PJJ. Hooykaas
Institute of Molecular Plant Sciences, Leiden University, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands
We have investigated the cis-acting potential of several as elements (20-bp
as-1/ocs-like sequences) in both yeast and plant cells. These
TGACG[N7]TGACG-resembling elements were surprisingly similar with respect
to their ability to confer inducibility by auxins and related compounds to
a heterologous TATA box in stably transformed plant cells. Both in plant
cells and in yeast it was found that differences between as elements were
of a quantitative nature. A strong element based on the consensus sequence
for as elements conferred the highest level of gene expression. The rather
aberrant as elements present in the promoters of auxin-inducible gst genes
Nt103 and Nt114 of tobacco were much weaker cis-acting elements. The
ability of an element to drive reporter gene expression was found to
correlate with the extent to which proteins present in (nuclear) extracts
of yeast and plant cells bound to it. The cloned transcription factor TGA1a
was shown to be a very good candidate to be the factor that mediates the in
vivo regulation of gene expression via as elements. The physiological
significance of gene activation by active and inactive auxins is discussed.
