THE PLANT CELL, Vol 1, Issue 9 839-853, Copyright © 1989 by American Society of Plant Biologists
Regulation of [beta]-Glucuronidase Expression in Transgenic Tobacco Plants by an A/T-Rich, cis-Acting Sequence Found Upstream of a French Bean [beta]-Phaseolin Gene
M. M. Bustos, M. J. Guiltinan, J. Jordano, D. Begum, F. A. Kalkan and T. C. Hall
Department of Biology, Texas A&M University, College Station, Texas 77843-3258
A 0.8-kilobase fragment from the 5[prime]-flanking region of a French bean
[beta]-phaseolin gene yielded strong, temporally regulated, and
embryo-specific expression of [beta]-glucuronidase (GUS) in transgenic
tobacco plants, paralleling that found for the seed protein phaseolin
[Sengupta-Gopalan, C., Reichert, N.A., Barker, R.F., Hall, T.C., and Kemp,
J.D. (1985) Proc. Natl. Acad. Sci. USA 82, 3320-3324]. Gel retardation and
footprinting assays using nuclear extracts from immature bean cotyledons
revealed strong binding of nuclear proteins to an upstream region (-628 to
-682) that contains two inverted A/T-rich motifs. Fusion of a 103-base pair
fragment or a 55-base pair synthetic oligonucleotide containing these
motifs to a minimal 35S promoter/GUS cassette yielded strong GUS expression
in several tissues. A different pattern of GUS expression was obtained in
immature embryos and germinating seedlings from the nominally constitutive,
full-length, 35S promoter. Whereas GUS expression under the control of the
0.8-kilobase [beta]-phaseolin regulatory region is limited to immature
embryos, expression from constructs containing the A/T-rich motifs is
strongest in roots. These data, combined with S1 mapping, provide direct
evidence that a plant upstream A/T-rich sequence that binds nuclear
proteins can activate transcription in vivo. They also indicate that
additional regulatory elements in the [beta]-phaseolin 5[prime]-flanking
region are required for embryo-specific gene expression.
