|Liang, Hua - BRDC POST DOC|
Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 28, 1999
Publication Date: N/A
Technical Abstract: Glutamine synthetase (GS) in higher plants is encoded by small gene families. In corn, six genes encode five cytoplasmic and one chloroplast forms of the enzyme. Our earlier work suggests that the cytoplasmic gene GS1-2 encodes for the pedicel-specific GS isozyme, which is the most abundant GS form in the maize kernel. A full-length genomic GS1-2 clone, including 1.9 kb of the 5' flanking sequence, has been isolated and the 5' flanking sequence, the 5' UTR and the coding region, up to and including the first two introns, have been fused in frame to luciferase (LUC) and used, along with a series of deletion constructs, to evaluate its ability to drive transient gene expression in Maize Black Mexican Sweet cells. Luciferase expression was largely dependent on the presence of the native introns, however, maize ADH intron 1, when used to replace the native introns, worked equally as well at stimulating gene expression. Promoter activity was positively correlated with promoted length from -207 to -817. A -72 promoter construct, however, was roughly 2 orders of magnitude more active than the -207 to -817 constructs in the transient assay. A control construct deleted down to +10 of the putative transcription start site did not induce LUC activity. These data suggest that the GS1-2 promoter contains a silencer element somewhere between -72 and -200 base pairs upstream of the transcription start site. Results of our characterization of this region will be presented.