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1.
Summary Incorporation of15NO3-into amino acids was studied during the anaerobic germination of rice seeds. In treated coleoptiles, the label was incorporated into glutamine, glutamate, alanine,-aminobutyric acid (Gaba), arginine, aspartate and methionine. These findings are consistent with a primary incorporation of nitrate nitrogen into glutamine, glutamate and aspartate, and their further conversion to alanine, Gaba, arginine and methionine. 相似文献
2.
Two ferredoxin-dependent proteins, nitrite reductase and glutamate synthase, play a role in nitrate assimilation during the
anaerobic germination of rice (Oryza sativa L.). This paper reports the expression of the root form of ferredoxin-NADP+ oxidoreductase (FNR), the protein responsible for providing reduced ferredoxin in rice coleoptiles. Using an antibody against
FNR, a protein with the expected molecular mass for root FNR (35 kDa) was recognized by Western blot analysis in extracts
from aerobic and anaerobic coleoptiles. The enzyme is synthesized de novo, as shown by immunoprecipitation of the radiolabeled
35-kDa protein from anaerobic seedlings grown in the presence of [35S]methionine. Northern blot analysis with specific probes for root and leaf FNR showed the presence of mRNA for the root form
but not for the leaf form, in both aerobic and anaerobic rice coleoptiles. The inductive effect of exogenous nitrate on the
expression of FNR is further evidence for the presence of the root type of FNR in rice coleoptiles. The importance of the
expression of root FNR during the anaerobic development of rice seedlings is discussed.
Received: 7 October 1996 / Accepted: 22 January 1997 相似文献
3.
Monica Mattana Immacolata Coraggio Ida Brambilla Alcide Bertani Remo Reggiani 《Planta》1996,199(1):74-78
Ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1) is the last enzyme involved in the pathway of nitrate assimilation in higher plants. This paper describes the synthesis and expression of the enzyme in anaerobic coleoptiles of rice (Oryza sativa L.) and its regulation by exogenous nitrate. The activity of Fd-GOGAT was strongly inhibited by cycloheximide between 4 and 9 d of anaerobic germination. The addition of nitrate slightly increased, in the first 5 h, the specific activity of Fd-GOGAT as well as the amount of a 160-kDa protein specifically immunoprecipitated with anti-Fd-GOGAT serum. Northern blot analysis, performed with a specific riboprobe, showed the presence of mRNA of the expected size and the inductive effect of nitrate. The role of Fd-GOGAT is discussed in relation to the anaerobic assimilation of nitrate by rice coleoptiles.Abbreviations CHX
cycloheximide
- Fd
ferredoxin
- GOGAT
glutamate synthase
- GS
glutamine synthetase
- NiR
nitrite reductase
- NR
nitrate reductase
The authors wish to thank Dr. J. Turner (Rothamsted Experimental Station, Harpenden, UK) for providing Fd-GOGAT antibody and Dr. H. Sakakibara (Nagoya University, Nagoya, Japan) for Fd-GOGAT clone. This research was supported by the National Research Council of Italy, special project RAISA, sub-projekt N. 2, paper N. 2174. 相似文献
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5.
Remo Reggiani Monica Mattana Nicoletta Aurisano Alcide Bertani 《Physiologia plantarum》1993,89(3):640-643
Nitrate present in rice caryopses can be reduced to ammonium and the ammonium subsequently assimilated by the coleoptile during anaerobic germination. All the enzymes of nitrate reduction and ammonia assimilation are present in the coleoptile. The supply of 15 NO3 confirms that the nitrate nitrogen is anaerobically incorporated into amino acids. Under anoxia, nitrate and nitrite reductase activities are increased in the coleoptile by exogenous nitrate. The importance of nitrate utilization during the anaerobic germination of rice caryopses is discussed. 相似文献
6.
Summary The effects of different nitrogen sources (NH4, NO3, and NH4 NO3) on the uptake of copper by wheat and barley growing in solution culture were compared in three experiments. Both the copper
concentration and weight gain of shoots and roots were found to decrease in the order NO3>NH4 NO3>NH4 irrespective of the solution copper concentration. Ammonium nitrogen was also found to decrease the copper concentration
of wheat grown on a copper deficient soil compared with a nitrate source of nitrogen.
Increasing concentrations of ammonium ions in solution culture caused ammonium toxicity and reduced both plant copper concentrations
and vegetative yield. Biochemical investigations using paper chromatography revealed that the amino acid asparagine was the
major detoxification product of ammonia in wheat. Copper deficient plants were found to have elevated levels of amino acids
compared with controls, irrespective of the nitrogen source. 相似文献
7.
Martha R. Downs Knute J. Nadelhoffer Jerry M. Melillo John D. Aber 《Trees - Structure and Function》1993,7(4):233-236
Summary Seedlings of red maple, white pine, pitch pine and red pine were fertilized with nutrient solutions containing 4 levels of nitrate or ammonium additions. These levels corresponded to approximately 0.5, 1, 2 and 4 times normal availability of nitrogen in northeastern forests. Nitrate reductase (NR) activity was assayed in roots and leaves. Red maples treated with nitrate showed much higher leaf activities and higher ratios of leaf NR activity to root NR activity than any other species. Ammonium additions to red maple and white pine appeared to inhibit NR activity in leaves. With high nitrate additions, NR activity was induced in roots and leaves of pine species, but activity in roots remained much higher than in leaves. 相似文献
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10.
Glutamine synthetase (GS; EC.6.3.1.2.) occurs as cytosolic (GS1) and plastidic (GS2) polypeptides. This paper describes the expression of GS isoenzymes in coleoptile during the anaerobic germination of rice (Oryza sativa L.) and the influence of exogenous nitrate on this. By immunoprecipitation with anti-GS serum, two polypeptides of 41- and 44-kDa were detected of which the former was predominant. After fractionation by ion-exchange chromatography, the 41 and 44 kDa bands were identified as GS1 and GS2, respectively. Northern blot analysis with specific probes showed the presence of mRNA for cytosolic GS but not for the plastidic form. The presence of exogenous nitrate did not alter the activity and expression of GS in the coleoptile. The role of GS during the anaerobic germination of rice seems to induce the re-assimilation of ammonia rather than the assimilation of nitrate.Abbreviations GS
glutamine synthetase
- GS1
cytosolic glutamine synthetase
- GS2
platidic glutamine synthetase
We are grateful to Dr. Julie V. Cullimore for providing GS anti-serum and clones. The research was supported by the National Research Council of Italy, special project RAISA, sub-project N. 2 paper N. 1586. 相似文献
11.
Summary The leaf and root nitrate reductase activities were measured in 7 day-old barley seedlings by anoxic nitrite accumulation in darkness, during 48h after the transfer from a N-starved medium to a 1.5 mM K15NO3 medium. Thisin situ nitrate reduction was compared with the15N incorporation in the reduced N fraction of the whole seedlings.The nitrate reduction integrated fromin situ measurements was lower than the reduced15N accumulation. The rootin situ nitrate reductase activity seemed to account for only the third of the real root nitrate reduction, which may have been responsible for the overall underestimation. This discrepancy was partly explained by the ability of the root to reduce nitrite in an anoxic environment.These results suggest that, after correction of thein situ estimation of the nitrate reduction. the roots contribute to about 50% of the total assimilation. 相似文献
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15.
Endopeptidase activity and nitrogen mobilization in senescing leaves of Nicotiana rustica in light and dark 总被引:1,自引:0,他引:1
The time course of endopeptidase activity (digestion of azocasein at pH 4.6) in leaves of intact plants of Nicotiana rustica L. was studied and related to changes in the contents of chlorophyll, total nitrogen and soluble and insoluble protein nitrogen. Endopeptidase activity increased several fold during senescence. However, the course of protein degradation did not reflect the steep slope of azocaseolytic activity. When single mature leaves were darkened, senescence proceeded faster than in illuminated leaves but the amount of nitrogen mobilized and translocated did not differ greatly between darkened and illuminated leaves. However, in contrast to leaves in light, azocaseolytic activity did not increase.
Gelatin zymograms obtained using isoelectric focusing of extracts of mature leaves showed several bands in the pH 4.0 to 6.5 region of the gels. During senescence in both light and dark the position and number of bands remained largely unchanged. In leaves in light, the activity of endopeptidases focusing in the range pH 4.1 to 5.0 increased greatly. In leaves in dark, however, no major changes in activity could be detected. The results suggest that in tobacco leaves endopeptidase activity normally increases considerably during senescence but this increase is not a prerequisite for an effective protein degradation.
Separation and analysis of free amino acids showed that during senescence in light the levels of all amino acids decreased considerably. In leaves senescing in the dark there were large increases in the levels of glutamine and asparagine, concomitant decreases in glutamate and aspartate, and considerable increases in all other amino acids. 相似文献
Gelatin zymograms obtained using isoelectric focusing of extracts of mature leaves showed several bands in the pH 4.0 to 6.5 region of the gels. During senescence in both light and dark the position and number of bands remained largely unchanged. In leaves in light, the activity of endopeptidases focusing in the range pH 4.1 to 5.0 increased greatly. In leaves in dark, however, no major changes in activity could be detected. The results suggest that in tobacco leaves endopeptidase activity normally increases considerably during senescence but this increase is not a prerequisite for an effective protein degradation.
Separation and analysis of free amino acids showed that during senescence in light the levels of all amino acids decreased considerably. In leaves senescing in the dark there were large increases in the levels of glutamine and asparagine, concomitant decreases in glutamate and aspartate, and considerable increases in all other amino acids. 相似文献
16.
The ability of several high arctic plant species to utilize nitrate nitrogen under field conditions 总被引:2,自引:0,他引:2
The ability to utilize NO
inf3
sup–
in seven high arctic plant species from Truelove Lowland, Devon Island, Canada was investigated, using an in vivo assay of maximum potential nitrate reductase (NR) activity and applications of 15N. Plant species were selected on the basis of being characteristic of nutrient-poor and nutrient-rich habitats. In all species leaves were the dominant site of NR activity. Root NR activity was negligible in all species except Saxifraga cernua. NO
inf3
sup–
availability per se did not appear to limit NR activity of the species typically found on nutrient-poor sites (Dryas integrifolia, Saxifraga oppositifolia, and Salix arctica), or in Cerastium alpinum, as leaf NR activities remained low, even after NO
inf3
sup–
addition. 15NO
inf3
sup–
uptake was limited in D. integrifolia and Salix arctica. However, the lack of field induction of NR activity in C. alpinum and Saxifraga oppositifolia was not due to restricted nitrate uptake, as 15NO
inf3
sup–
labelled NO
inf3
sup–
entered the roots and shoots of both species. Leaf NR activity rates were low in three of the species typical of nutrient-rich habitats (O. digyna, P. radicatum and Saxifraga cernua), sampled from a site containing low soil NO
inf3
sup–
. Additions of NO
inf3
sup–
significantly increased leaf NR activity in these latter species, suggesting that potential NR activity was limited by the availability of NO
inf3
sup–
. 15N labelled NO
inf3
sup–
was taken up by O. digyna. P. radicatum and Saxifraga cernua. Although two species (D. integrifolia and Salix arctica) showed little utilization of NO
inf3
sup–
, we concluded that five of the seven selected high arctic plant species (C. alpinum, O. digyna, P. radicatum, Saxifraga cernua and Saxifraga oppositifolia) do have the potential to utilize NO
inf3
sup–
as a nitrogen source under field conditions, with the highest potential to utilize NO
inf3
sup–
occurring in three of the species typically found on fertile habitats. 相似文献
17.
M. C. Cowan 《Plant and Soil》1979,51(2):279-282
Summary When nitrogen fixation in peas was partially replaced by nitrate assimilation as the source of nitrogen, an increase was found in the amount of soluble nitrogen that could be extracted from the fruits of the plants, and within this soluble fraction, increases were found in the levels of some of the acidic amino acids. Levels of protein amino acids in the peas were generally unaffected by the type of nitrogen source except for the level of aspartic acid which was about 20 per cent lower in peas supplied with nitrate. No differences were found in the proportions of the essential amino acids. 相似文献
18.
开放式空气二氧化碳浓度增高(FACE)条件下水稻的根系活力和氮同化能力 总被引:7,自引:1,他引:7
利用FACE(Free Air Carbon-dioxide Enrichment)平台技术,用伤流量法研究了低氮(LN 150 kg·hm-2)和常氮(NN 250 kg·hm-2)水平下,大气CO2浓度升高对水稻分蘖、抽穗期和穗后35 d根系活力和根系N同化能力(氨基酸合成能力)的影响.结果表明,就整株水稻来看, CO2浓度升高和N处理对根系活力无显著影响;但由于FACE条件下水稻分蘖数增加14.5%(LN)和20.7%(NN),使每茎根系活力(伤流强度)降低1.4%~21.7%.在分蘖和抽穗期,虽然FACE处理促进了根系吸收的无机N向氨基酸转化,根系伤流液中氨基酸氮/无机氮提高11.1%~143.1%,但氨基酸浓度和合成总量和对照相比无明显差异.在穗后35 d,FACE处理减弱了水稻根系的N同化能力,表现为根系伤流液中氨基酸/无机氮降低38.1%(LN)和29.2%(NN);同时氨基酸浓度降低34.0%(LN)和44.7%(NN),氨基酸合成总量降低50.8%(LN)和40.0%(NN).提高施氮水平促进了抽穗期水稻根系对无机氮的吸收,伤流液中无机氮含量增加51.1%(对照)和155.2%(FACE),但并未增加氨基酸合成量,由此导致抽穗期氨基酸氮/无机氮显著降低19.5%(对照)和36.8%(FACE);同时,氮处理在这个时期与FACE处理表现出明显的交互作用. 相似文献
19.
The mechanism inducing the difference in growth rate under various temperature (10–50 °C) conditions was analyzed using rice
and azuki bean seedlings. The growth rate of rice coleoptiles and azuki bean epicotyls increased as temperature increased
up to 40 and 30 °C, respectively, and the elongation was retarded at a higher temperature. The cell wall extensibility of
rice coleoptiles and azuki bean epicotyls also showed the highest value at 40 and 30 °C, respectively, and became smaller
as the temperature rose or dropped from the optimum. The opposite tendency was observed in the minimum stress-relaxation time
of the cell wall. On the other hand, the cellular osmotic concentration of rice coleoptiles and azuki bean epicotyls was lower
at the temperature optimum for growth at 40 and 30 °C, respectively. When rice and azuki bean seedlings grown at 10, 20, 40,
or 50 °C were transferred to the initial temperature (30 °C), the growth rate of coleoptiles and epicotyls was mostly elevated,
concomitant with an increase in the cell wall extensibility. The growth rate was correlated with the cell wall mechanical
parameters in both materials. These results suggest that the environmental temperature modulates the growth rate of plant
shoots by affecting mainly the mechanical properties of the cell wall.
Electronic Publication 相似文献
20.
Effect of nitrate on water transfer across roots of nitrogen pre-starved maize seedlings 总被引:8,自引:0,他引:8
Jackson Hoarau Laure Barthes Agnès Bousser Eliane Deléens Jean-Louis Prioul 《Planta》1996,200(4):405-415
The addition of 10 mM KNO3 to the solution bathing the roots of young nitrogen-starved seedlings of Zea mays L. enhanced root water transfer within 15 h, compared with 10 mM KCl addition. The free exudation flux was 2.2–3.9 times higher in excised KNO3-treated roots than in KCl-treated ones. Cryo-osmometry data for xylem sap suggested that, compared with chloride, nitrate treatment increased the steady solute flux into the xylem, but did not modify the osmotic concentration of sap. Root growth was not significantly modified by nitrate within 15 h. Root hydraulic conductances were measured by using either hydrostatic-pressure or osmotic-gradient methods. During hydrostatic experiments, the conductance (kp), which is thought to refer mainly to the apoplasmic pathway, was 1.6 times larger in KNO3-than in KCl-treated plants. From experiments in which polyethylene glycol (PEG) 8000 was used as external osmolyte, osmotic conductances (ks) were found to be smaller by 5–20 times than kp for the two kinds of plants. The KCl-treated roots were characterized by a low ks which was the same for influx or efflux of water. By contrast, KNO3-treated roots exhibited two distinct conductances ks1 and ks2, indicating that influx of water was easier than efflux when the water flow was driven by the osmotic pressure gradient. Infiltration of roots with KNO3 solution supported the idea that nitrate might enhance the efficiency of the cell-to-cell pathway. The low ks value of KCl-treated roots and the existence of two contrasting ks values (ks1 and ks2) for KNO3-treated roots are discussed in terms of reversible closing of water channels. 相似文献