|Liang, Hua - UNIV CHICAGO, CHICAGO, IL|
|Rastogi, Rajeev - FORMER ARS POST DOC|
Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 25, 2001
Publication Date: N/A
Technical Abstract: Glutamine synthetase (GS) is a key enzyme in plant nitrogen metabolism. In maize, GS is encoded as a single plastid gene and five cytoplamsic genes. One of these, GS1-2, is strongly expressed within the basal maternal tissues of developing seeds (Rastogi, et al Plant and Cell Physiol. 39:443-446, 1998). The GS1-2 gene expression pattern correlates with the production of a unique GS isozyme that is found in the kernel's pedicel tissues. This gene has now been isolated and its 5' upstream regulatory region has been characterized by both transient and stable expression in maize tissues. Deletion and linker-scanner experiments revealed a minimal requirement of approximately 40 base pairs upstream of the putative transcription start site to drive transient gene expression. Stable expression of a heterologous gene, consisting of the GS1-2 genomic clone extending from 664 base pairs upstream of the putative transcriptional start site to the middle of exon III, fused in-frame with GUS, resulted in the predicted tissue-specific expression in the basal maternal seed tissues, including the surrounding pericarp. Gene expression within the pedicel parenchyma that subtends the basal endosperm transfer cells and embryo was particularly strong. In contrast, GUS expression was not observed in the endosperm, embryo, leaves or roots. The GS1-2 expression pattern is consistent with the GS isozyme's role in nitrogen metabolism during grain fill.