PLANT PHYSIOLOGY , Vol 105, Issue 1 357-367, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
Identification of a Light-Responsive Region of the Nuclear Gene Encoding the B Subunit of Chloroplast Glyceraldehyde 3-Phosphate Dehydrogenase from Arabidopsis thaliana
H. B. Kwon, S. C. Park, H. P. Peng, H. M. Goodman, J. Dewdney and M. C. Shih
Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242 (H.-B.K., S.-C.P, H.-P.P., M.-C. S.)
We report here the identification of a cis-acting region involved in light
regulation of the nuclear gene (GapB) encoding the B subunit of chloroplast
glyceraldehyde 3-phosphate dehydrogenase from Arabidopsis thaliana. Our
results show that a 664-bp GapB promoter fragment is sufficient to confer
light induction and organ-specific expression of the Escherichia coli
[beta]-glucuronidase reporter gene (Gus) in transgenic tobacco (Nicotiana
tabacum) plants. Deletion analysis indicates that the -261 to -173 upstream
region of the GapB gene is essential for light induction. This region
contains four direct repeats with the consensus sequence 5[prime]
-ATGAA(A/G)A-3[prime] (Gap boxes). Deletion of all four repeats abolishes
light induction completely. In addition, we have linked a 109-bp (-263 to
-152) GapB upstream fragment containing the four direct repeats in two
orientations to the -92 to +6 upstream sequence of the cauliflower mosaic
virus 35S basal promoter. The resulting chimeric promoters are able to
confer light induction and to enhance leaf-specific expression of the Gus
reporter gene in transgenic tobacco plants. Based on these results we
conclude that Gap boxes are essential for light regulation and
organ-specific expression of the GapB gene in A. thaliana. Using gel
mobility shift assays we have also identified a nuclear factor from tobacco
that interacts with GapA and GapB DNA fragments containing these Gap boxes.
Competition assays indicate that Gap boxes are the binding sites for this
factor. Although this binding activity is present in nuclear extracts from
leaves and roots of light-grown or dark-treated tobacco plants, the
activity is less abundant in nuclear extracts prepared from leaves of
dark-treated plants or from roots of greenhouse-grown plants. In addition,
our data show that this binding factor is distinct from the GT-1 factor,
which binds to Box II and Box III within the light-responsive element of
the RbcS-3A gene of pea.
