Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1998
Publication Date: N/A
Technical Abstract: Glutamine synthetase (GS), which catalyzes the assimilation of ammonia into glutamine, is a key enzyme of nitrogen metabolism in higher plants. Most maize kernel glutamine synthesis occurs in the maternal seed (pedicel) tissues. A physically and kinetically distinct GS isoform, localized in the pedicel, increases in activity during grain fill. Analysis of the tissue and temporal expression patterns of known maize GS genes suggests that the cytoplasmic GS1-2 gene encodes the pedicel-specific GS isoform. A full-length genomic GS1-2 clone, including 1.9 kb of the 5' flanking sequence, has been isolated and the 5' flanking sequence has been shown to drive tobacco leaf transient gene expression. A series of deletion constructs are being made for characterization of the GS1-2 promoter in tobacco leaf transient assays. Tobacco plants are also being stably transformed with either the 1.9 kb promoter/GUS reporter construct or a 2.8 kb portion of the GS 1-2 gene, which includes the 5' upstream region, the 5' UTR and the first intron, fused in frame to the GUS reporter gene. The results of the characterization of the GS1-2 promoter in this heterologous system will be presented.