scholarly journals A Novel Gene (narM) Required for Expression of Nitrate Reductase Activity in the Cyanobacterium Synechococcus elongatus Strain PCC7942

2004 ◽  
Vol 186 (7) ◽  
pp. 2107-2114 ◽  
Author(s):  
Shin-ichi Maeda ◽  
Tatsuo Omata
Keyword(s):  
Nitrate Reductase ◽  
Structural Gene ◽  
Nitrate Reductase Activity ◽  
Insertional Mutagenesis ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Gene Cassette ◽  
Synechococcus Elongatus ◽  
Prosthetic Group ◽  
Functional Link

ABSTRACT A new class of mutants deficient in nitrate assimilation was obtained from the cyanobacterium Synechococcus elongatus strain PCC7942 by means of random insertional mutagenesis. A 0.5-kb genomic region had been replaced by a kanamycin resistance gene cassette in the mutant, resulting in inactivation of two genes, one of which was homologous to the recently characterized cnaT gene of Anabaena sp. strain PCC7120 (J. E. Frías, A. Herrero, and E. Flores, J. Bacteriol. 185:5037-5044, 2003). While insertional mutation of the cnaT homolog did not affect expression of the nitrate assimilation operon or the activity of the nitrate assimilation enzymes in S. elongatus, inactivation of the other gene, designated narM, resulted in specific loss of the cellular nitrate reductase activity. The deduced NarM protein is a hydrophilic protein consisting of 161 amino acids. narM was expressed constitutively at a low level. The narM gene has its homolog only in the cyanobacterial strains that are capable of nitrate assimilation. In most of the cyanobacterial strains, narM is located downstream of narB, the structural gene of the cyanobacterial nitrate reductase, suggesting the functional link between the two genes. NarM is clearly not the structural component of the cyanobacterial nitrate reductase. The narM insertional mutant normally expressed narB, indicating that narM is not the transcriptional regulator of the structural gene of nitrate reductase. These results suggested that narM is required for either synthesis of the prosthetic group of nitrate reductase or assembly of the prosthetic groups to the NarB polypeptide to form functional nitrate reductase in cyanobacteria.

Nitrate Reductase from a Mutant Strain of Chlamydomonas reinhardii Incapable of Nitrate Assimilation

1983 ◽  
Vol 38 (5-6) ◽  
pp. 439-445 ◽  
Author(s):  
Emilio Fernández ◽  
Jacobo Cárdenas
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Wild Strain ◽  
Nitrate Assimilation ◽  
Pyridine Nucleotide ◽  
Spectral Studies ◽  
Binding Region ◽  
Chlamydomonas Reinhardii ◽  
Blue Sepharose

Nitrate reductase from mutant 305 of Chlamydomonas reinhardii has been purified about 90-fold and biochemically characterized. The enzyme can use reduced flavins and viologens as electron donors to reduce nitrate but, unlike the nitrate reductase complex from its parental wild strain, lacks NAD(P)H-nitrate reductase and NAD(P)H-cytochrome c reductase activities, does not bind to Blue-Agarose or Blue-Sepharose and exhibits a significantly lower molecular weight (177.000 vs. 241.000), whereas its kinetic characteristics and its sensitivity against several inhibitors and treatments are very similar to those of the terminal nitrate reductase activity of the wild strain complex. Spectral studies and antagonistic experiments with tungstate show the presence of cytochrome b557 and molybdenum. These facts lead us to propose that nitrate reductase from mutant 305 has a protein deletion which affects the pyridine nucleotide binding region of the diaphorase protein but without any effect on the terminal nitrate reductase activity.

Seasonal variation in nitrate reductase activity in needles of high-elevation red spruce trees

1992 ◽  
Vol 22 (3) ◽  
pp. 375-380 ◽  
Author(s):  
M.G. Tjoelker ◽  
S.B. McLaughlin ◽  
R.J. DiCosty ◽  
S.E. Lindberg ◽  
R.J. Norby
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
High Elevation ◽  
Preliminary Evidence ◽  
Air Pollutant ◽  
Red Spruce ◽  
Acid Vapor ◽  
Assimilation Capacity

To assess seasonal and site variation in foliar nitrate reductase activity and its utility as a biochemical marker for the uptake of nitrogen oxide pollutants in high-elevation forests, we measured nitrate reductase activity in current-year needles of red spruce (Picearubens Sarg.) saplings at two high-elevation stands (1935 and 1720 m) in the Great Smoky Mountains, North Carolina. Measurements spanned two growing seasons between September 1987 and September 1988. Nitrate reductase activity peaked near 60 nmol•g−1•h−1 at both sites in September and October 1987 and August 1988 and declined 80% in November 1987 and 65% in September 1988. Although nitrate reductase activity was 30% greater in saplings at the higher site relative to the lower site in September and October 1987, activity dropped to approximately 10 nmol•g−1•h−1 at both sites in November 1987. No differences among sites were evident the following year. Comparing deposition of nitric acid vapor at a nearby site to nitrate reductase activity suggests that needle nitrate reductase activity is not an unequivocal marker for foliar uptake of nitrogen oxides during air pollutant episodes. The changes in soil nitrate levels in this system provide preliminary evidence that foliar nitrate assimilation may, in part, include nitrate taken up from the soil, as the highest activity occurred during periods of higher A-horizon nitrate concentrations in 1988. These measurements of nitrate reductase activity suggest that red spruce are capable of assimilating nitrate in foliage in the field and that the nitrate assimilation capacity varies throughout the year.

Contribution of the Root System to Nitrate Assimilation in Whole Cotton Plants.

1977 ◽  
Vol 4 (5) ◽  
pp. 811 ◽  
Author(s):  
JW Radin
Keyword(s):  
Nitrate Reductase ◽  
Root Growth ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Physiological Role ◽  
Nitrate Assimilation ◽  
Relative Magnitude ◽  
Balance Sheets ◽  
Cotton Plants ◽  
Reduced Nitrogen

Cotton (Gossypium hirsutum L.) is a species in which most nitrate is assimilated in the green shoot. A physiological role for the small amount of nitrate reductase activity in the roots can be questioned on the basis of relative magnitude. In this investigation, cotton plants were grown on nutrient solutions containing either 1 or 5 mM nitrate, and balance sheets were developed for the transport and metabolism of nitrate and reduced nitrogen in the root and shoot during exponential growth. At either nitrate level, assimilation in the roots was adequate to supply all the nitrogen for root growth. However, some of the reduced nitrogen was exported in the xylem, leaving a net deficit of about 10% at 1 mM nitrate and 36% at 5 mM nitrate. This deficit was presumably satisfied by reduced nitrogen from the shoot. Thus, at these two nitrate concentrations, root growth apparently depended more upon nitrogen assimilated in the roots themselves than upon nitrogen from the shoot. The different fates of nitrogen assimilated in the root and in the shoot may be related to the demonstrated differential regulation of nitrate reductase activity in these two sites.

scholarly journals Transcriptional and translational adaptation to aerobic nitrate anabolism in the denitrifier Paracoccus denitrificans

2017 ◽  
Vol 474 (11) ◽  
pp. 1769-1787 ◽  
Author(s):  
Victor M. Luque-Almagro ◽  
Isabel Manso ◽  
Matthew J. Sullivan ◽  
Gary Rowley ◽  
Stuart J. Ferguson ◽  
...  
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Mutational Analysis ◽  
Paracoccus Denitrificans ◽  
Reductase Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Nitrate Assimilation ◽  
Transcriptional Unit ◽  
Regulation Mechanism ◽  
N Source

Transcriptional adaptation to nitrate-dependent anabolism by Paracoccus denitrificans PD1222 was studied. A total of 74 genes were induced in cells grown with nitrate as N-source compared with ammonium, including nasTSABGHC and ntrBC genes. The nasT and nasS genes were cotranscribed, although nasT was more strongly induced by nitrate than nasS. The nasABGHC genes constituted a transcriptional unit, which is preceded by a non-coding region containing hairpin structures involved in transcription termination. The nasTS and nasABGHC transcripts were detected at similar levels with nitrate or glutamate as N-source, but nasABGHC transcript was undetectable in ammonium-grown cells. The nitrite reductase NasG subunit was detected by two-dimensional polyacrylamide gel electrophoresis in cytoplasmic fractions from nitrate-grown cells, but it was not observed when either ammonium or glutamate was used as the N-source. The nasT mutant lacked both nasABGHC transcript and nicotinamide adenine dinucleotide (NADH)-dependent nitrate reductase activity. On the contrary, the nasS mutant showed similar levels of the nasABGHC transcript to the wild-type strain and displayed NasG protein and NADH–nitrate reductase activity with all N-sources tested, except with ammonium. Ammonium repression of nasABGHC was dependent on the Ntr system. The ntrBC and ntrYX genes were expressed at low levels regardless of the nitrogen source supporting growth. Mutational analysis of the ntrBCYX genes indicated that while ntrBC genes are required for nitrate assimilation, ntrYX genes can only partially restore growth on nitrate in the absence of ntrBC genes. The existence of a regulation mechanism for nitrate assimilation in P. denitrificans, by which nitrate induction operates at both transcriptional and translational levels, is proposed.

Nitrate assimilation in suspension cultures of Paul's scarlet rose

1980 ◽  
Vol 58 (9) ◽  
pp. 1088-1094 ◽  
Author(s):  
Douglas B. Jordan ◽  
John S. Fletcher
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Suspension Cultures ◽  
Fresh Weight ◽  
Assay Medium ◽  
Enzyme Extraction ◽  
Cell Age

Nitrate reductase activity, the assimilation of NO3−, and growth were studied in suspension cultures of Rosa cv. Paul's Scarlet grown in media with either 24 mM NO3−,or with 24 mM NO3− + 0.91 mM NH4+.Ammonium partially repressed the development of nitrate reductase during the first 4 days of growth and the degree of repression was more pronounced when cells were provided with lower concentrations of NO3−. The repression of nitrate reductase by NH4+ was only observed when casein was used during enzyme extraction. The repression of nitrate reductase activity by NH4+ was not recognized in earlier work when no casein was used.The presence of casein in the extraction or assay medium increased the total recoverable nitrate reductase activity. The enhancement was differential depending on cell age with the greatest influence being on young and old cells where 100 and 400% enhancements were observed, respectively.In vitro nitrate reductase activity correlated well with NO3− assimilation. Over 14 days of growth, the ratio of total nitrate reductase activity to the total amount of NO3− reduced was 3.8 for cultures grown with or without NH4+. Cultures grown with NH4+ achieved 80% more fresh weight and reduced 70% more NO3− over 14 days than cultures grown without NH4+.

Influence of nitrate level on nitrate assimilation in tomato (Lycopersicon esculentum) plants under saline stress

2004 ◽  
Vol 82 (2) ◽  
pp. 207-213 ◽  
Author(s):  
Pilar Flores ◽  
M Ángeles Botella ◽  
Antonio Cerdá ◽  
Vicente Martínez
Keyword(s):  
Lycopersicon Esculentum ◽  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Plant Size ◽  
Saline Stress ◽  
Short Period ◽  
Half Strength ◽  
Short Time

This experiment was conducted to study the effect of salinity and different NO3– concentrations on NO3– uptake, transport, and reduction. To avoid the significant effect of plant size, the main difference from other studies was the short time period of treatment application. Tomato plants (Lycopersicon esculentum Mill. 'Asun') were grown for 11 d in half-strength Hoagland solution (with 7 mmol/L NO3–) in a growth chamber under controlled conditions. After that, the different NO3– treatments were 0.5, 2, and 4 mmol/L NO3–, and saline treatments consisted of two levels of NaCl: 0 (control) and 75 mmol/L. Under control conditions, an increase in NO3– concentration in the nutrient solution resulted in greater NO3– uptake, NO3– xylem flux, NO3- concentrations in tissues, and leaf and root nitrate reductase activity. However, when plants were exposed to salinity for a short period of time and the plant size or the shoot/root ratio was not an additional factor affecting the physiological parameters, the NO3– concentration in the solution slightly affected the different steps of NO3– assimilation.Key words: nitrate assimilation, nitrate reductase activity, nitrogen, salinity, tomato, Lycopersicon esculentum.

scholarly journals An Indirect Impact of Sika Deer Overpopulation on Eutrophication of an Aquatic Ecosystem via Understory Vegetation: An Individual-Based Approach Using Nitrate Reductase Activity

2021 ◽  
Vol 9 ◽  
Author(s):  
Yasuo Tsuboike ◽  
Masanori Fujii ◽  
Yumiko Yoshida ◽  
Naoto Kamata
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Sika Deer ◽  
Reductase Activity ◽  
Nitrate Assimilation ◽  
Understory Vegetation ◽  
Vegetation Coverage ◽  
Significant Difference ◽  
The Difference

Eutrophication of aquatic ecosystems is a serious global issue. Stream nitrate concentrations at the University of Tokyo Chichibu Forest have increased since 2000 after the opening of the new highway in 1998. Nitrogen oxide emissions from automobile exhausts were the most likely source of increased nitrate input in the forest ecosystem. Around the area, the sika deer Cervus nippon Temminck population has greatly increased since around 2000 and intensively browsed the understory vegetation. We hypothesized that the degradation of the understory vegetation caused by the deer overpopulation was one of the causes of increased nitrate output. Monthly observations were carried out from April to October 2013 to investigate the understory vegetation at the heights of 0–30 and 100–150 cm above the ground inside (without deer) and outside (with deer) of a deer exclusion fence. Plant taxa and % coverage of each taxon at each layer were recorded. The in vivo nitrate reductase activity (NRA) (≈ nitrate assimilation rate) was determined for each plant taxa each month. Compared to inside the fence, the understory vegetation outside was poor with smaller % coverage and less diverse community structure, and was occupied by unpalatable plant taxa that were uncommon or absent inside the fence. Contrary to our expectation, the phylogenetic diversity of the community assemblage outside the fence showed greater evenness (less clustering) than inside. The NRA peaked in early in the season or late in the season. In contrast to a previous report, no significant difference in the NRA was found between woody and herbaceous plants. Although the difference was no more than that of vegetation coverage, the estimated community-level NRA inside the fence was 5.6 times higher than that of the outside. The difference was greatest early in the season. These results support our hypothesis.

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