Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of Bradyrhizobium japonicum wild-type strain USDA110 nirK, norC and nosZ denitrification genes in soybean root nodules was studied by in situ histochemical detection of beta-galactosidase activity. Similarly, P(nirK)-lacZ, P(norC)-lacZ, and P(nosZ)-lacZ fusions were also expressed in bacteroids isolated from root nodules. Levels of beta-galactosidase activity were similar in both bacteroids and nodule sections from plants that were solely N(2)-dependent or grown in the presence of 4 mM KNO(3). These findings suggest that oxygen, and not nitrate, is the main factor controlling expression of denitrification genes in soybean nodules. In plants not amended with nitrate, B. japonicum mutant strains GRK308, GRC131, and GRZ25, that were altered in the structural nirK, norC and nosZ genes, respectively, showed a wild-type phenotype with regard to nodule number and nodule dry weight as well as plant dry weight and nitrogen content. In the presence of 4 mM KNO(3), plants inoculated with either GRK308 or GRC131 showed less nodules, and lower plant dry weight and nitrogen content, relative to those of strains USDA110 and GRZ25. Taken together, the present results revealed that although not essential for nitrogen fixation, mutation of either the structural nirK or norC genes encoding respiratory nitrite reductase and nitric oxide reductase, respectively, confers B. japonicum reduced ability for nodulation in soybean plants grown with nitrate. Furthermore, because nodules formed by each the parental and mutant strains exhibited nitrogenase activity, it is possible that denitrification enzymes play a role in nodule formation rather than in nodule function.
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PMID:Expression of nir, nor and nos denitrification genes from Bradyrhizobium japonicum in soybean root nodules. 1503 54

Soybean (Glycine max L. cv Williams) seeds were sown in pots containing a 1:1 perlite-vermiculite mixture and grown under greenhouse conditions. Nodules were initiated with a nitrate reductase expressing strain of Rhizobium japonicum, USDA 110, or with nitrate reductase nonexpressing mutants (NR(-) 108, NR(-) 303) derived from USDA 110. Nodules initiated with either type of strain were normal in appearance and demonstrated nitrogenase activity (acetylene reduction). The in vivo nitrate reductase activity of N(2)-grown nodules initiated with nitrate reductase-negative mutant strains was less than 10% of the activity shown by nodules initiated with the wild-type strain. Regardless of the bacterial strain used for inoculation, the nodule cytosol and the cell-free extracts of the leaves contained both nitrate reductase and nitrite reductase activities. The wild-type bacteroids contained nitrate reductase but not nitrite reductase activity while the bacteroids of strains NR(-) 108 and NR(-) 303 contained neither nitrate reductase nor nitrite reductase activities.Addition of 20 millimolar KNO(3) to bacteroids of the wild-type strain caused a decrease in nitrogenase activity by more than 50%, but the nitrate reductase-negative strains were insensitive to nitrate. The nitrogenase activity of detached nodules initiated with the nitrate reductase-negative mutant strains was less affected by the KNO(3) treatment as compared to the wild-type strain; however, the results were less conclusive than those obtained with the isolated bacteroids.The addition of either KNO(3) or KNO(2) to detached nodules (wild type) suspended in a semisolid agar nutrient medium caused an inhibition of nitrogenase activity of 50% and 65% as compared to the minus N controls, and provided direct evidence for a localized effect of nitrate and nitrite at the nodule level. Addition of 0.1 millimolar sucrose stimulated nitrogenase activity in the presence or absence of nitrate or nitrite. The sucrose treatment also helped to decrease the level of nitrite accumulated within the nodules.
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PMID:Nitrate and Nitrite Reduction in Relation to Nitrogenase Activity in Soybean Nodules and Rhizobium japonicum Bacteroids. 1666 97

The main objectives of this work were to study the effect of different N sources on plant growth, N accumulation, and on the expression of nitrate reductase activity in Phaseolus vulgaris L. leaves. Plants were grown under greenhouse conditions (15 to 25 kilolux; 16/8 hour day/night cycles) in plastic pots filled with perlite: vermiculite (1:1) and watered daily with a minus N solution (N(2) plants) or supplemented with either KNO(3), (NH(4))(2)SO(4), or urea as combined N sources.Significant levels of nitrate reductase activity in trifoliolate leaves of N(2)-, NH(4) (+)-, urea-, or NO(3) (-)-dependent plants was demonstrated throughout this work. Leaves from the urea- or NH(4) (+)-grown plants accumulated NO(2) (-) in the dark but not in the light when NO(2) (-) was supplied by vacuum infiltration. These results indicated that the potential for reduction of NO(3) (-) or NO(2) (-) was not impaired by growing the plants on NH(4) (+) or urea and, in addition, provided evidence for the occurrence of a non-nitrate-inducible nitrite reductase. The nitrate reductase activities associated with N(2)-, NH(4) (+)-, or urea-dependent plants are tentatively regarded as ;constitutive' to differentiate from the widely occurring NO(3) (-)-inducible nitrate reductase activity.Plants grown on NO(3) (-) or urea accumulated significantly larger amounts of reduced N and dry matter as compared to NH(4) (+)- and N(2)-dependent plants. Regardless of N treatment, or size of plants, about 50% of the N accumulated by the plant was allocated to the leaves.
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PMID:Expression of Nitrate and Nitrite Reductase Activities under Various Forms of Nitrogen Nutrition in Phaseolus vulgaris L. 1666 85

The level of nitrate reductase (NR) and nitrite reductase (NiR) varied in both shoot and root tissue from nitrate-fed Zea mays L. grown under a 16-hour light/8-hour dark regime over a 10-day period postgermination, with peak activity occurring in days 5 to 6. To study the effect of different light regimes on NR and NiR enzyme activity and mRNA levels, 6-day-old plants were grown in the presence of continuous KNO(3) (10 millimolar). Both shoot NRA and mRNA varied considerably, peaking 4 to 8 hours into the light period. Upon transferring plants to continuous light, the amplitude of the peaks increased, and the peaks moved closer together. In continuous darkness, no NR mRNA or NR enzyme activity could be detected by 8 hours and 12 hours, respectively. In either a light/dark or continuous light regime, root NRA and mRNA did not vary substantially. However, when plants were placed in continuous darkness, both declined steadily in the roots, although some remained after 48 hours. Although there was no obvious cycling of NiR enzyme activity in shoot tissue, changes in mRNA mimicked those seen for NR mRNA. The expression of NR and NiR genes is affected by the light regime adopted, but light does not have a direct effect on the expression of these genes.
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PMID:Effect of light/dark cycles on expression of nitrate assimilatory genes in maize shoots and roots. 1666 65

The effects of a non-selective blocker of NO synthases LNNA in a dose of 25 mg/kg and nitrates KNO3, NaNO3, Mg(NO3)2, and Ca(NO3)2 in doses of 5 and 50 mg/kg were studied on the model of experimental ischemic stroke induced by bilateral occlusion of the common carotid arteries. Wistar rats were randomized into 40 treatment (n=960) and 8 control (n=192) groups. Treatment group rats received injection of either nitrate, or LNNA, or a combination LNNA+nitrate. All substances were administered intraperitoneally 1 h prior to brain ischemia or 5 sec after occlusion of the common carotid arteries. Control rats received the same volume of 0.9% NaCl at the same terms. The non-selective inhibitor of NO synthases LNNA administered against the background of brain ischemia increased neurological deficit and animal mortality. Nitrate/nitrite reductase system had protective properties depending on the cation of nitrate and concentration of a nitrate during inhibition of NO synthase system under conditions of brain ischemia and hypoxia.
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PMID:Protective Role of Nitrate/Nitrite Reductase System during Transient Global Cerebral Ischemia. 2979 13