Note on nitrate reduction in<i>Rhizobium</i>

Ishizawa, Shuichi

doi:10.1080/00380768.1980.10431231

Cited by 14 publications

(10 citation statements)

References 6 publications

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“…Inhibition of nitrogenase in bacteroids by ammonium has recently been reported (19). Ammonium might be generated from nitrate in some bacteroids by nitrate reductase (10, 12) and nitrite reductase (8,17). For these reasons, [NH4+J in nodules was determined in most experiments reported here.…”

Section: Discussionmentioning

confidence: 99%

Synthesis and Accumulation of Nitrite in Soybean Nodules Supplied with Nitrate

Streeter¹

1982

Plant Physiol.

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It has been known for over a century that combined nitrogen inhibits the growth of legume nodules, and, in recent decades, it has been shown that combined nitrogen also inhibits N2 fixation activity of nodules (6,7,9,13,17,22). While there has been some interest in the effect of ammonium (7, 9), most of the emphasis has been on the effect of nitrate, which is the most common form of nitrogen absorbed by plant roots growing in cultivated soil. The mechanism by which nodule growth and nitrogenase activity are adversely affected by nitrate is still not clear.One of the simplest explanations for the effect of nitrate on nodule growth and nitrogenase activity states that some product of nitrate metabolism is inhibitory. Nitrite is a logical candidate for such an inhibitory role because (a) it is a potent inhibitor of nitrogenase activity when mixed with the purified enzyme (24) (b) it deoxygenates and oxidizes leghemoglobin in vitro resulting in the formation of ferric leghemoglobin ( 18); and (c) it (ie. nitrous acid) reacts spontaneously with primary and secondary amines.There have been very few reports demonstrating the actual presence of nitrite in nodules on plants supplied with nitrate.Rigaud has reported 140 to 780 nmole NO2/g fresh weight of soybean nodules 6 to 24 h after supplying plants with 7 mM N03 (17). More recently, Manhart and Wong have reported high NO2 concentrations in lupine and cowpea nodules supplied with very high (15 mM) nitrate (13). They also showed that the amount of NO2-accumulated in nodules was positively correlated with NR2 activity in bacteroids (13). In both of these studies, the main interest was in exploring the inhibition of nitrogenase activity by nitrate over periods of 1 to 5 d.After the discovery of NR in Rhizobium japonicum bacteroids (5) it was generally assumed that the synthesis of nitrite in nodules occurs in the bacteroids. However, Gibson and Pagan showed that growth and N2-fixing activity of Macroptilium atropurpureum and Trifolium subterraneum nodules formed by Rhizobia lacking NR were still depressed when plants were supplied with nitrate (6). This observation has recently been extended to Vigna unguiculata and Lupinus angustifolius nodules (13). Coupled with the fact that nitrite was not detected in these nodules (6, 13), these observations make it less likely that the generation of nitrite in nodules may be the mechanism by which nitrate inhibits nodule growth and activity. The work reported here was focused on the effect of nitrate on soybean nodule growth. The objectives were to (a) Beeson, were planted in silica sand. Variations in nitrate concentration in nutrient solutions were provided by balancing nitrate and chloride. Details on nutrient solution composition and plant growth conditions have been published (22).Plants for experiments 1 and 2 were grown outdoors during the summer months without alteration of the natural photoperiod.

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Section: Discussionmentioning

confidence: 99%

Synthesis and Accumulation of Nitrite in Soybean Nodules Supplied with Nitrate

Streeter¹

1982

Plant Physiol.

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“…Nevertheless, the bacteroids' NRA obtained from the nodules with -1.8 MPa potential was still maintained at the equivalent level as compared to that in the control (-0.6 MPa). The reduction of NO3-by NR in the bacteroids has been described as an assimilatory reduction (4,7,9). But, bacteroids could also utilize NO3-as electron acceptor for nitrate respiration if 02 was limited resulting in the production of ATP for the support of N2 fixation (2, 4, 8).…”

Section: Resultsmentioning

confidence: 99%

“…Daniel and Appleby (2), Riguad et al (8), and Zablotowicz et al (16) indicated that the utilization of NO3-by soybean bacteroids was dissimilatory. Nevertheless, Randall et al (7), Russell et al (9), and Ishizawa (4) suggested that the reduction of NO3-in soybean nodules could also be assimilatory, and, thus contributed to the nitrogen economy ofthe bean plant.…”

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confidence: 99%

“…Although the majority of absorbed N03-was reduced in the aerial portion of bean plant, NO3-reduction was also detectable in symbiotic nodules (1,2,4,8,13 (7), Russell et al (9), and Ishizawa (4) suggested that the reduction of NO3-in soybean nodules could also be assimilatory, and, thus contributed to the nitrogen economy ofthe bean plant.…”

Section: Introductionmentioning

confidence: 99%

“…The results show that nitrate reduction occurred both in the cytosol and bacteroids of water-stressed soybean nodules. The reduction of nitrate functioned at different physiological modes in these two fractions.Soybean plant can utilize both soil NO3-and atmospheric N2.Although the majority of absorbed N03-was reduced in the aerial portion of bean plant, NO3-reduction was also detectable in symbiotic nodules (1,2,4,8,13 (7), Russell et al (9), and Ishizawa (4) suggested that the reduction of NO3-in soybean nodules could also be assimilatory, and, thus contributed to the nitrogen economy ofthe bean plant.The NO2-, produced as a result of NO-reduction, is further reduced by NiR2. Daniel and Appleby (2) were unable to detect NiRA in bacteroids of soybean nodules, even though enzyme activity could be found in Rhizobium japonicum grown anaerobically.…”

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confidence: 99%

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Effect of Water Stress on the Reduction of Nitrate and Nitrite by Soybean Nodules

Chen¹,

Sung²

1983

Plant Physiol.

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The effects of water stress on nitrate reductase and nitrite reductase activities in symbiotic nodules were examined in field-grown soybean plants (Glycine max L Merr. cv Clark). The in vitro assays of enzyme activity indicated that the nodule cytosol and bacteroids contained both nitrate reductase and nitrite reductase activities. The reduction of nitrate in bacteroids increased significantly as nodule water potential declined from -0.6 to -1.4 megapascals, and then decreased when -1.8 megapascals water potential was reached. On the contrary, the reduction of nitrate in nodule cytosol was inhibited as water stress progressed. Increases in water stress intensity also caused a significant inhibition in nitrite reductase activities of bacteroids and nodule cytosol within soybean nodules. The results show that nitrate reduction occurred both in the cytosol and bacteroids of water-stressed soybean nodules. The reduction of nitrate functioned at different physiological modes in these two fractions.Soybean plant can utilize both soil NO3-and atmospheric N2.Although the majority of absorbed N03-was reduced in the aerial portion of bean plant, NO3-reduction was also detectable in symbiotic nodules (1,2,4,8,13 (7), Russell et al. (9), and Ishizawa (4) suggested that the reduction of NO3-in soybean nodules could also be assimilatory, and, thus contributed to the nitrogen economy ofthe bean plant.The NO2-, produced as a result of NO-reduction, is further reduced by NiR2. Daniel and Appleby (2) were unable to detect NiRA in bacteroids of soybean nodules, even though enzyme activity could be found in Rhizobium japonicum grown anaerobically. However, NiR existed in the cytosol fraction of soybean nodules ( 12).It is well documented that the NRA in the leaves of higher plants is very sensitive to changes in the water status ofthe plant. But little attention seems to have been given to the effect ofwater stress on NRA in root nodules. Aparicio-Tejo and Sanchez-Diaz (I) reported that the nodule NRA in Medicago sativa L. was stimulated by water stress. There are no reports on the relationship between nodule NRA and water stress in the soybean plant. The present study reports the effect of water stress on NRA and NiRA using detached soybean nodules.

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Nitrous oxide production by nitrogen-fixing, fast-growing Rhizobia

1984

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Rhizobium trifolii, R. leguminosarum, andR. "hedysarum", grownex planta under anoxic conditions in a chemically defined medium, evolve N2O from NO3 (-), NO2 (-), and (NH4)2NO3. The amount of nitrous oxide formed after 96 hours is about 0.2μM×mg(-1) cells d.w. Large availability of organic matter enhances the production of N2O from nitrate by free-livingR. trifolii in peat/sand mixtures. Denitrification of the above species andR. meliloti was detected also in planta. Nitrous oxide production increases almost linearly from 10-45μM×mg(-1) nodules d.w. when nitrogen-fixing plants are exposed to increasing concentrations of nitrate (1-12μM).

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Note on nitrate reduction inRhizobium

Cited by 14 publications

References 6 publications

Synthesis and Accumulation of Nitrite in Soybean Nodules Supplied with Nitrate

Synthesis and Accumulation of Nitrite in Soybean Nodules Supplied with Nitrate

Effect of Water Stress on the Reduction of Nitrate and Nitrite by Soybean Nodules

Nitrous oxide production by nitrogen-fixing, fast-growing Rhizobia

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