Monomeric NarB Is a Dual-Affinity Nitrate Reductase, and Its Activity Is Regulated Differently from That of Nitrate Uptake in the Unicellular Diazotrophic Cyanobacterium Synechococcus sp. Strain RF-1

ABSTRACT Synechococcus sp. strain RF-1 is a unicellular freshwater cyanobacterium that fixes N2 aerobically and exhibits a circadian rhythm for nitrogenase activity under a light-dark regimen. Synechococcus sp. strain RF-1 also utilizes nitrate, nitrite, or ammonium for growth. Under the diazotrophic growth, the nitrate uptake in Synechococcus sp. strain RF-1 was induced by nitrate or nitrite but repressed by ammonium. In contrast, a prominent nitrate reductase (NR) activity was detected in diazotrophically grown cells using the reduced methyl viologen assay. The NR activity was not inhibited by ammonium and only slightly enhanced by nitrate. The different expression patterns of nitrate uptake and NR in Synechococcus sp. strain RF-1 were reflected in general at the transcript level determined by reverse transcriptase PCR. Under both nitrate-induced and uninduced conditions, the in situ NR activity exhibited similar biphasic kinetics for nitrate. The recombinant NR encoded by the narB gene of Synechococcus sp. strain RF-1, expressed in E. coli, also showed the biphasic kinetics with similar pH and temperature profiles. By in-gel NR activity assay, the recombinant NarB was found to exist as a single form. Both the high- and low-affinity NR activities of the recombinant NarB showed the same thermostability. When modified at the N terminus by a polyhistidine tag, the recombinant NR activity was shifted from biphasic to hyperbolic kinetics and showed only a single Km for nitrate, indicating the functional importance of the NarB N-terminal structure in NR kinetics.

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Nitrogen assimilation and dissimilation in five genotypes of Brachiaria spp.

Canadian Journal of Botany ◽

10.1139/b81-201 ◽

1981 ◽

Vol 59 (8) ◽

pp. 1475-1479 ◽

Cited By ~ 15

Author(s):

Pedro Antonio A. Pereira ◽

Johanna Döbereiner ◽

Carlos A. Neyra

Keyword(s):

Nitrate Reductase ◽

Field Experiment ◽

Nitrogen Assimilation ◽

Nitrogenase Activity ◽

Nitrate Accumulation ◽

Brachiaria Ruziziensis ◽

Intact Soil ◽

Nr Activity ◽

Better Than ◽

Nitrate Fertilization

Five genotypes of Brachiaria spp. were planted in a field experiment with and without nitrate fertilization. Nitrogen metabolism was evaluated by measurements of nitrate reductase (NR) activity in leaves, nitrate accumulation in stems, and nitrogenase activity and dentrification in intact soil–plant cores. There were differences between genotypes in all parameters and a tendency was observed for genotypes with high NR activity and nitrate accumulation to have low nitrogenase activity and vice versa. Brachiaria radicans (Tanner grass) was representative for the first type and B. ruziziensis (CPI 30623) for the second. Denitrification reached 7% of the applied N within 63 h and was lowest in Tanner grass and highest in B. brizantha (FL 902-4). Brachiaria ruziziensis (CPI 30623) plants were able to withstand N stress better than B. radicans as a consequence, possibly, of differences in nitrogenase activity.

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Effect of External Nitrate Concentration on Nitrate and Iron Uptake and Assimilation in Vaccinium Species

HortScience ◽

10.21273/hortsci.40.4.1116c ◽

2005 ◽

Vol 40 (4) ◽

pp. 1116C-1116

Author(s):

Rebecca Darnell

Keyword(s):

Nitrate Reductase ◽

Iron Uptake ◽

Nitrate Uptake ◽

Nitrate Concentration ◽

Dry Weight ◽

Optimal Growth ◽

Low Ph ◽

Iron Nitrate ◽

Nr Activity ◽

Soil Adaptation

Most Vaccinium species, including V. corymbosum, have strict soil requirements for optimal growth, requiring low pH, high iron, and nitrogen, primarily in the ammonium form. V. arboreum is a wild species adapted to high pH, low iron, nitrate-containing soils. This broader soil adaptation in V. arboreum may be related to increased efficiency of iron or nitrate uptake/assimilation compared with cultivated Vaccinium species. To test this, nitrate and iron uptake, and nitrate reductase (NR) and ferric chelate reductase (FCR) activities were compared in two Vaccinium species, V. arboreum and the cultivated V. corymbosum. Plants were grown hydroponically for 15 weeks in either 1.0 or 5.0 mm NO3 with 0.09 mm Fe. Root FCR activity was greater in V. arboreum compared with V. corymbosum, especially at the lower external nitrate concentration. However, this was not reflected in differences in iron uptake. Nitrate uptake and root NR activity were greater in V. arboreum compared with V. corymbosum. The lower nitrate uptake and assimilation in V. corymbosum was reflected in decreased plant dry weight compared with V. arboreum. V. arboreum appears to be more efficient in acquiring nitrate compared with V. corymbosum, possibly due to increased NR activity, and this may partially explain the wider soil adaptation of V. arboreum.

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RELATIONS BETWEEN NITRATE REDUCTASE ACTIVITY AND NITROGEN ACCUMULATION IN SOYBEANS

Canadian Journal of Plant Science ◽

10.4141/cjps76-057 ◽

1976 ◽

Vol 56 (2) ◽

pp. 377-384 ◽

Cited By ~ 5

Author(s):

MIR HATAM ◽

D. J. HUME

Keyword(s):

Nitrate Reductase ◽

Nitrate Reduction ◽

Nitrate Uptake ◽

Reductase Activity ◽

N Uptake ◽

Nitrogen Accumulation ◽

Total N ◽

Total Plant ◽

Nr Activity

An in vivo assay for nitrate reductase (NR) activity was adapted to measure total NR activity in soybean [Glycine max (L.) Merr.] plants grown for a 29-day period indoors. Disappearance of nitrate from the nutrient solution, plant nitrate and total plant nitrogen (N) also were measured. Under the conditions of this experiment, nitrate reduction estimated from NR activities agreed closely with actual nitrate reduction. The same assay was used to measure leaf NR activities of field-grown soybeans throughout the 1971 growing season. Leaf NR activities accounted for 77 and 72% of the total N uptake in plants receiving 0 and 280 kg N as NH4NO3/ha, respectively. Measurements of nitrate and ammonium losses from soil under soybeans and under adjacent bare soil at three stages of plant development suggested that in plots receiving no fertilizer N, 86% of N uptake from the soil was in the form of nitrate. The NR activity of field-grown plants agreed well with total plant N derived from soil nitrates. Results indicated that leaf NR activities were proportional to nitrate uptake and might be used to determine amounts and seasonal patterns of nitrate uptake by soybean plants.

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Influence of simazine on nitrate uptake and nitrate reductase activity in Triticum aestivum (L.) and Cucumis sativus (L.) seedlings

Acta Societatis Botanicorum Poloniae ◽

10.5586/asbp.1984.023 ◽

2014 ◽

Vol 53 (2) ◽

pp. 247-256 ◽

Cited By ~ 1

Author(s):

Irena Jarzyńska ◽

Józef Buczek

Keyword(s):

Triticum Aestivum ◽

Nitrate Reductase ◽

Cucumis Sativus ◽

Nitrate Uptake ◽

Reductase Activity ◽

Triticum Aestivum L ◽

Probable Mechanism ◽

Cucumis Sativus L ◽

Photosynthesis Inhibition ◽

Nr Activity

The influence of simazine (2-chloro-4,6-bis(ethylamine)-1,3,5-triazine) on N03- uptake and nitrate reductase (NR) activity in wheat (Triticum aestivum) and cucumber (Cucumis sativus) seedlings was investigated. It was found that at first (up to 12 h after herbicide treatment) simazine enhanced and then inhibited NR activity in the leaves and roots of the tested plants. After seven days of growth in nutrient medium containing 2.5 and 25 µM simazine the herbicide inhibited by 25 and 70 per cent, respectively, NR activity and reduced by 30 per cent in wheat and 50 per cent in cucumber seedlings nitrate uptake. The probable mechanism of NR inhibition by simazin is discussed and it is suggested that the influence of the herbicide on NR activity may not be exclusively connected with photosynthesis inhibition.

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Nitrogen assimilation and dissimilation in five genotypes of Brachiaria spp.

Canadian Journal of Botany ◽

10.1139/b81-143 ◽

1981 ◽

Vol 59 (6) ◽

pp. 1050-1055 ◽

Cited By ~ 1

Author(s):

Pedro Antonio A. Pereira ◽

Johanna Döbereiner ◽

Carlos A. Neyra

Keyword(s):

Nitrate Reductase ◽

Field Experiment ◽

Nitrogen Assimilation ◽

Nitrogenase Activity ◽

Nitrate Accumulation ◽

Brachiaria Ruziziensis ◽

Intact Soil ◽

Nr Activity ◽

Better Than ◽

Nitrate Fertilization

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Structural genes for nitrate-inducible formate dehydrogenase in Escherichia coli K-12.

Genetics ◽

10.1093/genetics/125.4.691 ◽

1990 ◽

Vol 125 (4) ◽

pp. 691-702 ◽

Cited By ~ 6

Author(s):

B L Berg ◽

V Stewart

Keyword(s):

Escherichia Coli ◽

Nitrate Reductase ◽

Formate Dehydrogenase ◽

Recombinant Dna ◽

Structural Genes ◽

Respiratory Pathway ◽

E Coli ◽

Formate Oxidation ◽

Operon Expression ◽

K 12

Abstract Formate oxidation coupled to nitrate reduction constitutes a major anaerobic respiratory pathway in Escherichia coli. This respiratory chain consists of formate dehydrogenase-N, quinone, and nitrate reductase. We have isolated a recombinant DNA clone that likely contains the structural genes, fdnGHI, for the three subunits of formate dehydrogenase-N. The fdnGHI clone produced proteins of 110, 32 and 20 kDa which correspond to the subunit sizes of purified formate dehydrogenase-N. Our analysis indicates that fdnGHI is organized as an operon. We mapped the fdn operon to 32 min on the E. coli genetic map, close to the genes for cryptic nitrate reductase (encoded by the narZ operon). Expression of phi(fdnG-lacZ) operon fusions was induced by anaerobiosis and nitrate. This induction required fnr+ and narL+, two regulatory genes whose products are also required for the anaerobic, nitrate-inducible activation of the nitrate reductase structural gene operon, narGHJI. We conclude that regulation of fdnGHI and narGHJI expression is mediated through common pathways.

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Morpho-physiological and gene expression responses of wheat by Aegilops cylindrica amphidiploids to salt stress

10.1101/2020.06.07.139220 ◽

2020 ◽

Author(s):

Razieh Kiani ◽

Ahmad Arzani ◽

S. A. M. Mirmohammady Meibody ◽

Mehdi Rahimmalek ◽

Khadijeh Razavi

Keyword(s):

Salt Stress ◽

Expression Patterns ◽

Ion Homeostasis ◽

Transcript Level ◽

Salt Tolerant ◽

Quantitative Real Time Pcr ◽

Aegilops Cylindrica ◽

Significant Differential Expression ◽

Lower Root ◽

Vacuolar Sequestration

AbstractAegilops cylindrica Host is one of the most salt-tolerant species in the Triticeae tribe. Amphidiploid plants derived from hybridization of ‘Roshan’ × Aegilops cylindrica and ‘Chinese Spring’ × Ae. cylindrica genotypes contrasting in salt tolerance were assessed for their morpho-physiological responses and the expression patterns of two genes related to ion homeostasis under 250 mM NaCl. Results showed that salt stress caused significant declines in both their morphological and phenological traits. Moreover, salt stress reduced not only their chlorophyll content but also their root and shoot K contents and K/Na ratios, while it led to significant enhancements in the remaining traits. Similar to Ae. cylindrica, the amphidiploids subjected to salt stress exhibited significantly higher H2O2 levels, root and shoot K contents, and root and shoot K/Na ratios accompanied by lower root and shoot Na contents and MDA concentrations when compared with the same traits in the wheat parents. Quantitative Real-Time PCR showed significant differential expression patterns of the NHX1 and HKT1;5 genes between the amphidiploids and their parents. The transcript level of HKT1;5 was found to be higher in the roots than in the shoots of both the amphidiploids and Ae. cylindrica while NHX1 exhibited a higher expression in the shoot tissues. The consistency of these data provides compelling support for the hypothesis that active exclusion of Na from the roots and elevated vacuolar sequestration of Na in the leaves might explain the declining Na levels in the shoots and roots of both the amphidiploids and Ae. cylindrica relative to those measured in wheat parents. It is concluded that the hybridized amphiploids are potentially valuable resources for salt improvement in bread wheat through the backcrossing approach.

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Fnr-, NarP- and NarL-Dependent Regulation of Transcription Initiation from the Haemophilus influenzae Rd napF (Periplasmic Nitrate Reductase) Promoter in Escherichia coli K-12

Journal of Bacteriology ◽

10.1128/jb.187.20.6928-6935.2005 ◽

2005 ◽

Vol 187 (20) ◽

pp. 6928-6935 ◽

Cited By ~ 9

Author(s):

Valley Stewart ◽

Peggy J. Bledsoe

Keyword(s):

Escherichia Coli ◽

Nitrate Reductase ◽

Haemophilus Influenzae ◽

Control Region ◽

Binding Sites ◽

Transcription Initiation ◽

Transcriptional Control ◽

Class I ◽

E Coli ◽

Fnr Protein

ABSTRACT Periplasmic nitrate reductase (napFDAGHBC operon product) functions in anaerobic respiration. Transcription initiation from the Escherichia coli napF operon control region is activated by the Fnr protein in response to anaerobiosis and by the NarQ-NarP two-component regulatory system in response to nitrate or nitrite. The binding sites for the Fnr and phospho-NarP proteins are centered at positions −64.5 and −44.5, respectively, with respect to the major transcription initiation point. The E. coli napF operon is a rare example of a class I Fnr-activated transcriptional control region, in which the Fnr protein binding site is located upstream of position −60. To broaden our understanding of napF operon transcriptional control, we studied the Haemophilus influenzae Rd napF operon control region, expressed as a napF-lacZ operon fusion in the surrogate host E. coli. Mutational analysis demonstrated that expression required binding sites for the Fnr and phospho-NarP proteins centered at positions −81.5 and −42.5, respectively. Transcription from the E. coli napF operon control region is activated by phospho-NarP but antagonized by the orthologous protein, phospho-NarL. By contrast, expression from the H. influenzae napF-lacZ operon fusion in E. coli was stimulated equally well by nitrate in both narP and narL null mutants, indicating that phospho-NarL and -NarP are equally effective regulators of this promoter. Overall, the H. influenzae napF operon control region provides a relatively simple model for studying synergistic transcription by the Fnr and phospho-NarP proteins acting from class I and class II locations, respectively.

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