Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A cDNA, hvst1, was isolated from Hordeum vulgare by heterologous complementation in Escherichia coli. This cDNA encodes a high-affinity sulfate transporter that is 2442 bp in length and consists of 660 amino acids. Under steady-state conditions of sulfate supply during culture, sulfate influx (measured at 100 microM external sulfate concentration) and hvst1 transcript level were inversely correlated with sulfate concentrations in the culture solution. Glutathione (GSH) concentrations increased as external sulfate was increased from 2.5 to 250 microM. A time-course study, designed to investigate effects of sulfate withdrawal on the abundance of hvst1 transcript, showed a 5-fold increase of the latter within the first two hours. This was followed by a further slight increase during the next 46 h. These changes were accompanied by a parallel increase in sulfate influx and a decrease of root GSH concentrations. When plants that had been deprived of sulfate for 24 h were exposed to L-cysteine (Cys) or GSH for 3 h, GSH was the more effective down-regulator, reducing hvst1 transcript level to below that of unstarved controls. The decrease in transcript abundance induced by sulfate or Cys was partially relieved by the addition of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. Both hvst1 transcripts and sulfate influx increased as a function of N supply to N-starved plants. Amino oxyacetate acid (AOA), an aminotransferase inhibitor, when supplied with NO3-, increased transcript abundance of hvst1, while tungstate, methionine sulfoximine (MSO) and azaserine (AZA), inhibitors of nitrate reductase, glutamine synthetase and glutamate synthase (GOGAT), respectively, were without effect. AOA decreased root concentrations of aspartate (Asp), Cys and GSH; in contrast, glutamate (Glu) concentrations remained unchanged.
 ...
PMID:Regulation of the hvst1 gene encoding a high-affinity sulfate transporter from Hordeum vulgare. 1048 22

The significance of root nitrate reductase for sulfur assimilation was studied in tobacco (NICOTIANA TABACUM) plants. For this purpose, uptake, assimilation, and long-distance transport of sulfur were compared between wild-type tobacco and transformants lacking root nitrate reductase, cultivated either with nitrate or with ammonium nitrate. A recently developed empirical model of plant internal nitrogen cycling was adapted to sulfur and applied to characterise whole plant sulfur relations in wild-type tobacco and the transformant. Both transformation and nitrogen nutrition strongly affected sulfur pools and sulfur fluxes. Transformation decreased the rate of sulfate uptake in nitrate-grown plants and root sulfate and total sulfur contents in root biomass, irrespective of N nutrition. Nevertheless, glutathione levels were enhanced in the roots of transformed plants. This may be a consequence of enhanced APR activity in the leaves that also resulted in enhanced organic sulfur content in the leaves of the tranformants. The lack of nitrate reductase in the roots in the transformants caused regulatory changes in sulfur metabolism that resembled those observed under nitrogen deficiency. Nitrate nutrition reduced total sulfur content and all the major fractions analysed in the leaves, but not in the roots, compared to ammonium nitrate supply. The enhanced organic sulfur and glutathione levels in ammonium nitrate-fed plants corresponded well to elevated APR activity. But foliar sulfate contents also increased due to decreased re-allocation of sulfate into the phloem of ammonium nitrate-fed plants. Further studies will elucidate whether this decrease is achieved by downregulation of a specific sulfate transporter in vascular tissues.
 ...
PMID:Interaction of sulfur and nitrogen nutrition in tobacco (Nicotiana tabacum) plants: significance of nitrogen source and root nitrate reductase. 1785 63

To investigate the regulatory interactions between S assimilation and N metabolism in Brassica napus, de novo synthesis of amino acids and proteins was quantified by (15)N and (34)S tracing, and the responses of transporter genes, assimilatory enzymes and metabolites pool involving in nitrate and sulfate metabolism were assessed under continuous sulfur supply, sulfur deprivation and sulfate resupply after 3 days of sulfur (S) deprivation. S-deprived plants were characterized by a strong induction of sulfate transporter genes, ATP sulfurylase (ATPS) and adenosine 5'-phosphosulfate reductase (APR), and by a repressed activity of nitrate reductase (NR) and glutamine synthetase (GS). Sulfate resupply to the S-deprived plants strongly increased cysteine, amino acids and proteins concentration. The increase in sulfate and cysteine concentration caused by sulfate resupply was not matched with the expression of sulfate transporters and the activity of ATPS and APR which were rapidly decreased by sulfate resupply. A strong induction of O-acetylserine(thiol)lyase (OASTL), NR and GS upon sulfate resupply was accompanied with the increase in cysteine, amino acids and proteins pool. Sulfate resupply resulted in a strong increase in de novo synthesis of amino acids and proteins, as evidenced by the increases in N and S incorporation into amino acids (1.8- and 2.4-fold increase) and proteins (2.2-and 6.3-fold increase) when compared to S-deprived plants. The results thus indicate that sulfate resupply followed by S-deprivation accelerates nitrate assimilation for protein synthesis.
...
PMID:Sulfate resupply accentuates protein synthesis in coordination with nitrogen metabolism in sulfur deprived Brassica napus. 2552 20