PLANT PHYSIOLOGY , Vol 105, Issue 1 259-268, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
Analysis of the Involvement of ocs-Like bZip-Binding Elements in the Differential Strength of the Bidirectional mas1[prime]2[prime] Promoter
D. Feltkamp, R. Masterson, J. Starke and S. Rosahl
Max-Planck-Institut fur Zuchtungsforschung, Department of Genetic Principles of Plant Breeding, Carl von Linne-Weg 10, D 50829 Koln, Germany
The ocs-like elements of the bidirectional mas 1[prime]2[prime] promoter of
Agrobacterium tumefaciens, mas1[prime] and mas2[prime], were analyzed to
elucidate their role in the expression conferred by this promoter.
Tetramers of the elements were cloned upstream of the
[beta]-glucuronidase-coding region linked to the 35S promoter deleted at
-54. Transient expression assays with tobacco (Nicotiana tabacum) and
potato (Solanum tuberosum) protoplasts showed that tetramers of the
mas1[prime] element had 3- to 8-fold enhancing activity, respectively.
Enhancement obtained by tetramers of the mas2[prime] element was higher,
suggesting that this element plays a role in the stronger promoter activity
from the 2[prime] side. Three cDNA clones with high homology to the tobacco
transcription factor TGA1a were isolated from a potato root expression
library. Overexpression of the proteins encoded by these cDNA clones in
Escherichia coli and analysis of DNA-binding activity in bacterial extracts
showed that all three factors could bind strongly to the mas1[prime]
ocs-like element. In contrast, only two of the mas-binding factors
exhibited significant binding to the mas2[prime] element. Southern analysis
revealed the presence of a small, multigene family encoding the mas-binding
factors in potato.
