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

The reduction of nitrate to nitrite catalyzed by nitrate reductase (NR) is considered to be the rate-limiting and regulated step of nitrate assimilation, a major metabolic pathway occurring in a wide range of organisms which in turn supply the nutritional nitrogen requirements for other forms of life. Chlorella vulgaris NR mRNA levels are very responsive to changes in nitrogen source. In the presence of ammonia as the sole nitrogen source, under repressed conditions, NR mRNA is undetectable. Under inducing conditions, the removal of ammonia and addition of nitrate, rapid NR mRNA synthesis occurs. We are studying the elements involved in regulating the expression of this important gene. Two overlapping genomic clones (NRS1 and NR5') were isolated from a cosmid library. The two clones were sequenced and their sequences were aligned with that of a full-length NR cDNA. The gene is approximately 8 kb long and consists of 19 exons and 18 introns. Unlike NR isolated from other species, the exons which code for the functional domains of C. vulgaris are separated by introns. Two transcription start points (tsp) were identified and each is surrounded by potential initiator sequences. No TATA, CAAT or GC-rich promoter elements were located. A time course of NR induction revealed that while transcription initiation from one tsp remains at a constant level from the point of induction through steady state, the level of initiation from another tsp is high upon induction, but decreases as steady state is attained.
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PMID:Cloning and characterization of the nitrate reductase-encoding gene from Chlorella vulgaris: structure and identification of transcription start points and initiator sequences. 866 64

Previously we have shown that nitrate reductase (NR) activity was impaired in Arabidopsis seedlings and rosette stage leaves when the basic leucine zipper transcription factors HY5 and HYH were absent. In the present work, we investigated the influence of hy5 and hyh null mutations on the expression of the NR encoding genes NIA1 and NIA2, as well as genes involved in nitrate uptake and further assimilation of nitrite. Only NIA2, and not NIA1, transcript levels were positively influenced by the presence of HY5 and HYH. In the hy5 hyh mutant, enhancement of NIA2 expression by light was impaired in both seedlings and rosette stage plants. Induction of NIA2 transcription by nitrate was not influenced by HY5 or HYH. Although the peak NIA2 transcript level was much higher in wild type in comparison with the hy5 hyh mutant plant, diurnal variations of NIA2 expression were also observed in the mutant. A dual affinity nitrate transporter gene, NRT1.1, was expressed at a higher level in hy5 hyh than in the wild type, indicating that HY5 and HYH are repressors of NRT1.1. In conclusion, HY5 and HYH were activators of NIA2, but inhibitors of NRT1.1 when tested across various light treatments and tissue types.
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PMID:The bZIP transcription factors HY5 and HYH are positive regulators of the main nitrate reductase gene in Arabidopsis leaves, NIA2, but negative regulators of the nitrate uptake gene NRT1.1. 1954 16

The basic leucine zipper (bZIP) transcription factor HY5 plays a multifaceted role in plant growth and development. Here the apple MdHY5 gene was cloned based on its homology with Arabidopsis HY5. Expression analysis demonstrated that MdHY5 transcription was induced by light and abscisic acid treatments. Electrophoretic mobility shift assays and transient expression assays subsequently showed that MdHY5 positively regulated both its own transcription and that of MdMYB10 by binding to E-box and G-box motifs, respectively. Furthermore, we obtained transgenic apple calli that overexpressed the MdHY5 gene, and apple calli coloration assays showed that MdHY5 promoted anthocyanin accumulation by regulating expression of the MdMYB10 gene and downstream anthocyanin biosynthesis genes. In addition, the transcript levels of a series of nitrate reductase genes and nitrate uptake genes in both wild-type and transgenic apple calli were detected. In association with increased nitrate reductase activities and nitrate contents, the results indicated that MdHY5 might be an important regulator in nutrient assimilation. Taken together, these results indicate that MdHY5 plays a vital role in anthocyanin accumulation and nitrate assimilation in apple.
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PMID:The bZIP transcription factor MdHY5 regulates anthocyanin accumulation and nitrate assimilation in apple. 2911 91