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Site-specific mutations alter in vitro factor binding and change promoter expression pattern in transgenic plants
E Lam1, P N Benfey, P M Gilmartin
1Laboratory of Plant Molecular Biology, Rockefeller University, New York, NY 10021.
Summary
Activation sequence factor 1 (ASF-1) binds to the cauliflower mosaic virus 35S promoter. This binding is crucial for high gene expression in plant leaves and stems, influencing overall plant gene regulation.
Area of Science:
- Plant Molecular Biology
- Gene Regulation
- Biochemistry
Background:
- The cauliflower mosaic virus (CaMV) 35S promoter drives high gene expression across most plant organs.
- Understanding the regulatory elements of the 35S promoter is key to controlling gene expression in plants.
Purpose of the Study:
- To identify and characterize cellular factors that bind to the CaMV 35S promoter.
- To investigate the role of specific DNA motifs in regulating promoter activity in vivo.
Main Methods:
- DNase I footprinting and gel retardation assays to detect and characterize DNA-binding factors.
- Site-directed mutagenesis of specific promoter regions in transgenic tobacco plants.
- Analysis of gene expression levels in different plant tissues.
Main Results:
- A novel cellular factor, activation sequence factor 1 (ASF-1), was identified, binding to a TGACG motif in the 35S promoter.
- Mutations in the TGACG motif reduced ASF-1 binding and significantly decreased promoter activity in leaves, stems, and roots.
- A 21-bp element containing the TGACG motif was sufficient to confer high root expression when inserted into another promoter.
Conclusions:
- ASF-1 plays a significant role in regulating CaMV 35S promoter activity, particularly in leaf and stem tissues.
- The TGACG motif is essential for optimal promoter function, and its binding site is sufficient to alter expression patterns.
- Specific DNA-protein interactions are critical for differential gene expression in plants.