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Glutamate dehydrogenase (GDH) is ubiquitous to all organisms, yet its role in higher plants remains enigmatic. To better understand the role of GDH in plant nitrogen metabolism, we have characterized an Arabidopsis mutant (gdh1-1) defective in one of two GDH gene products and have studied GDH1 gene expression. GDH1 mRNA accumulates to highest levels in(More)
Studies of enzymes involved in nitrogen assimilation in higher plants have an impact on both basic and applied plant research. First, basic research in this area should uncover the mechanisms by which plants regulate genes involved in a metabolic pathway. Second, because nitrogen is a rate-limiting element in plant growth (Hageman and Lambert, 1988), it may(More)
In bacteria and yeast, glutamine synthetase (GS) expression is tightly regulated by the metabolic status of the cell, both at the transcriptional and posttranscriptional levels. We discuss the relative contributions of light and metabolic cues on the regulation of members of the GS gene family (chloroplastic GS2 and cytosolic GS1) in Arabidopsis. These(More)
In plants, ammonium released during photorespiration exceeds primary nitrogen assimilation by as much as 10-fold. Analysis of photorespiratory mutants indicates that photorespiratory ammonium released in mitochondria is reassimilated in the chloroplast by a chloroplastic isoenzyme of glutamine synthetase (GS2), the predominant GS isoform in leaves of(More)
We are using molecular, biochemical, and genetic approaches to study the structural and regulatory genes controlling the assimilation of inorganic nitrogen into the amino acids glutamine, glutamate, aspartate and asparagine. These amino acids serve as the principal nitrogen-transport amino acids in most crop and higher plants including Arabidopsis thaliana.(More)
What we'd like: f 2 NP f / 2 P/poly such that. What we'd like: f 2 NP f / 2 P/poly such that. Explicit circuit lower bounds known for very few circuit classes. What we'd like: f 2 NP f / 2 P/poly such that. Explicit circuit lower bounds known for very few circuit classes. Even for low depth circuits of AND, OR, NOT and mod-m gates, a lower bound eluded us(More)
The chemotactic cytokine interleukin 8 (IL-8) is produced upon stimulation by various agents in many cell types, including connective-tissue fibroblasts. Tumor necrosis factor (TNF) and IL-1 are potent inducers of IL-8 expression. Earlier we showed that TNF-induced stimulation of IL-8 mRNA accumulation in human FS-4 fibroblasts was inhibited by interferon(More)
The cytokine interleukin-8 (IL-8) is an important mediator of neutrophil, lymphocyte, and basophil chemotaxis and activation. Earlier we demonstrated that beta interferon (IFN-beta) can inhibit tumor necrosis factor (TNF)-induced IL-8 gene expression at the transcriptional level, apparently by a novel mechanism. To define the cis-acting elements and(More)