PLANT PHYSIOLOGY , Vol 106, Issue 2 447-458, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
Seed-Specific Gene Activation Mediated by the Cre/lox Site-Specific Recombination System
J. T. Odell, J. L. Hoopes and W. Vermerris
Agricultural Products, DuPont, Experimental Station, P.O. Box 80402, Wilmington, Delaware 19880-0402
The Cre/lox site-specific recombination system was used to activate a
transgene in a tissue-specific manner. Cre-mediated activation of a
[beta]-glucuronidase marker gene, by removal of a lox-bounded blocking
fragment, allowed the visualization of the activation process. By using
seed-specific promoters, the timing and efficiency of gene activation could
be followed within the developing tobacco (Nicotiana tabacum) embryo. To
serve as a basis for analyzing gene expression after Cre-mediated
activation, the timing and patterns of expression of the promoters of the
genes encoding French bean (Phaseolus vulgaris) [beta]-phaseolin and the
[alpha][prime] subunit of soybean (Glycine max) [beta]-conglycinin, as well
as the cauliflower mosaic virus 35S promoter, were studied in developing
transgenic tobacco embryos using the same visual marker. These
seed-specific promoters were expressed earlier than anticipated. The 35S
promoter was expressed earlier than the seed-specific promoters, but not in
globular-stage embryos. Cre-mediated gene activation occurred approximately
1 d after promoter activation, based on developmental staging, and spread
progressively throughout the embryo. The timing of gene activation was
varied by altering Cre expression. Efficient Cre expression ultimately
directed gene activation throughout the model tissue, whereas inefficient
Cre expression resulted in mosaic tissue. Limited gene activation provides
a system for cell lineage and developmental analyses.
