Studies on possible routes of ammonium assimilation in soybean root nodule bacteroids

1973 ◽  
Vol 19 (12) ◽  
pp. 1493-1499 ◽  
Author(s):  
Stanley D. Dunn ◽  
Robert V. Klucas
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Reductive Amination ◽  
Root Nodule ◽  
Root Nodules ◽  
Ammonium Assimilation ◽  
Kinetic Properties ◽  
Transferase Activity ◽  
Soybean Root

Glutamine amide–2-oxoglutarate aminotransferase NAD+ oxidoreductase (GOGAT), glutamine synthetase (GS), glutamate dehydrogenase (GD), and alanine dehydrogenase (AD) were studied in soybean root nodules. GS, GOGAT, and AD were present in bacteroids at levels that could account for ammonium assimilation, but GD activity was quite low. The total activities of GS and GD were higher in the cytosol than in the bacteroids by factors of 20 and 7, respectively, whereas GOGAT was not detected in the cytosol. GS (transferase activity) was inhibited by alanine, CTP, glycine, and tryptophan at 5 mM but was relatively unaffected by asparagine, aspartic acid, CMP, glucosamine, and histidine at 5 mM. GOGAT activity was unaffected by ATP, ADP, 8-hydroxyquinoline, and 1,10-phenanthroline but was inhibited by EDTA, citrate, and parachloromercuribenzoate. GOGAT activity (reductive amination) was also inhibited 97% by preincubation with 10−4 M azaserine for 30 min but GD activity was inhibited only 13%. The apparent Km values for NH4+ by AD was 7.4 × 10−3 M and by GD was 7.3 × 10−2 M while for glutamine by GOGAT it was 9.3 × 10−5 M. Activities and kinetic properties for these enzymes may suggest potential routes of nitrogen assimilation in vivo.

Distinct properties of two glutamine synthetase isoforms in soybean root nodules

2016 ◽  
Vol 52 (6) ◽  
pp. 643-649 ◽  
Author(s):  
Y. S. Tian ◽  
R. T. Wang ◽  
W. Zhao ◽  
J. X ◽  
X. J. Xing ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Root Nodules ◽  
Soybean Root

scholarly journals The sRNA NsiR4 is involved in nitrogen assimilation control in cyanobacteria by targeting glutamine synthetase inactivating factor IF7

2015 ◽  
Vol 112 (45) ◽  
pp. E6243-E6252 ◽  
Author(s):  
Stephan Klähn ◽  
Christoph Schaal ◽  
Jens Georg ◽  
Desirée Baumgartner ◽  
Gernot Knippen ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Metabolism ◽  
Nitrogen Assimilation ◽  
Nitrogen Sources ◽  
Transcriptome Profiling ◽  
Site Directed Mutagenesis ◽  
Reporter System ◽  
Available Nitrogen ◽  
Mrna Accumulation

Glutamine synthetase (GS), a key enzyme in biological nitrogen assimilation, is regulated in multiple ways in response to varying nitrogen sources and levels. Here we show a small regulatory RNA, NsiR4 (nitrogen stress-induced RNA 4), which plays an important role in the regulation of GS in cyanobacteria. NsiR4 expression in the unicellularSynechocystissp. PCC 6803 and in the filamentous, nitrogen-fixingAnabaenasp. PCC 7120 is stimulated through nitrogen limitation via NtcA, the global transcriptional regulator of genes involved in nitrogen metabolism. NsiR4 is widely conserved throughout the cyanobacterial phylum, suggesting a conserved function. In silico target prediction, transcriptome profiling on pulse overexpression, and site-directed mutagenesis experiments using a heterologous reporter system showed that NsiR4 interacts with the 5′UTR ofgifAmRNA, which encodes glutamine synthetase inactivating factor (IF)7. InSynechocystis, we observed an inverse relationship between the levels of NsiR4 and the accumulation of IF7 in vivo. This NsiR4-dependent modulation ofgifA(IF7) mRNA accumulation influenced the glutamine pool and thusNH4+assimilation via GS. As a second target, we identifiedssr1528, a hitherto uncharacterized nitrogen-regulated gene. Competition experiments between WT and an ΔnsiR4KO mutant showed that the lack of NsiR4 led to decreased acclimation capabilities ofSynechocystistoward oscillating nitrogen levels. These results suggest a role for NsiR4 in the regulation of nitrogen metabolism in cyanobacteria, especially for the adaptation to rapid changes in available nitrogen sources and concentrations. NsiR4 is, to our knowledge, the first identified bacterial sRNA regulating the primary assimilation of a macronutrient.

scholarly journals The Biology of Frankia sp. Strains in the Post-Genome Era

2011 ◽  
Vol 24 (11) ◽  
pp. 1310-1316 ◽  
Author(s):  
David R. Benson ◽  
James M. Brooks ◽  
Ying Huang ◽  
Derek M. Bickhart ◽  
Juliana E. Mastronunzio
Keyword(s):  
Root Nodule ◽  
Root Nodules ◽  
Ammonium Assimilation ◽  
Defense Responses ◽  
Nodule Formation ◽  
Plant Defense Responses ◽  
Plant Host ◽  
Future Studies ◽  
Microbiological Techniques ◽  
Bacterial Genes

Progress in understanding symbiotic determinants involved in the N2-fixing actinorhizal plant symbioses has been slow but steady. Problems persist with studying the bacterial contributions to the symbiosis using traditional microbiological techniques. However, recent years have seen the emergence of several genomes from Frankia sp. strains and the development of techniques for manipulating plant gene expression. Approaches to understanding the bacterial side of the symbiosis have employed a range of techniques that reveal the proteomes and transcriptomes from both cultured and symbiotic frankiae. The picture beginning to emerge provides some perspective on the heterogeneity of frankial populations in both conditions. In general, frankial populations in root nodules seem to maintain a rather robust metabolism that includes nitrogen fixation and substantial biosynthesis and energy-generating pathways, along with a modified ammonium assimilation program. To date, particular bacterial genes have not been implicated in root nodule formation but some hypotheses are emerging with regard to how the plant and microorganism manage to coexist. In particular, frankiae seem to present a nonpathogenic presence to the plant that may have the effect of minimizing some plant defense responses. Future studies using high-throughput approaches will likely clarify the range of bacterial responses to symbiosis that will need to be understood in light of the more rapidly advancing work on the plant host.

scholarly journals Inhibition of Glutamine Synthetase by Phosphinothricin Leads to Transcriptome Reprograming in Root Nodules of Medicago truncatula

2012 ◽  
Vol 25 (7) ◽  
pp. 976-992 ◽  
Author(s):  
Ana R. Seabra ◽  
Patrícia A. Pereira ◽  
Jörg D. Becker ◽  
Helena G. Carvalho
Keyword(s):  
Glutamine Synthetase ◽  
Medicago Truncatula ◽  
Root Nodule ◽  
Higher Plants ◽  
Cell Metabolism ◽  
Root Nodules ◽  
Organic N ◽  
N Availability ◽  
Time Points ◽  
N Assimilation

Glutamine synthetase (GS) is a vital enzyme for the assimilation of ammonia into amino acids in higher plants. In legumes, GS plays a crucial role in the assimilation of the ammonium released by nitrogen-fixing bacteria in root nodules, constituting an important metabolic knob controlling the nitrogen (N) assimilatory pathways. To identify new regulators of nodule metabolism, we profiled the transcriptome of Medicago truncatula nodules impaired in N assimilation by specifically inhibiting GS activity using phosphinothricin (PPT). Global transcript expression of nodules collected before and after PPT addition (4, 8, and 24 h) was assessed using Affymetrix M. truncatula GeneChip arrays. Hundreds of genes were regulated at the three time points, illustrating the dramatic alterations in cell metabolism that are imposed on the nodules upon GS inhibition. The data indicate that GS inhibition triggers a fast plant defense response, induces premature nodule senescence, and promotes loss of root nodule identity. Consecutive metabolic changes were identified at the three time points analyzed. The results point to a fast repression of asparagine synthesis and of the glycolytic pathway and to the synthesis of glutamate via reactions alternative to the GS/GOGAT cycle. Several genes potentially involved in the molecular surveillance for internal organic N availability are identified and a number of transporters potentially important for nodule functioning are pinpointed. The data provided by this study contributes to the mapping of regulatory and metabolic networks involved in root nodule functioning and highlight candidate modulators for functional analysis.

scholarly journals Expression of the Plastid-Located Glutamine Synthetase ofMedicago truncatula. Accumulation of the Precursor in Root Nodules Reveals an in Vivo Control at the Level of Protein Import into Plastids

2003 ◽  
Vol 132 (1) ◽  
pp. 390-399 ◽  
Author(s):  
Paula M. Melo ◽  
Lı́gia M. Lima ◽  
Isabel M. Santos ◽  
Helena G. Carvalho ◽  
Julie V. Cullimore
Keyword(s):  
Glutamine Synthetase ◽  
Protein Import ◽  
Root Nodules

scholarly journals The Effect of Bialaphos on Ammonium-Assimilation and Photosynthesis I. Effect on the Enzymes of Ammonium-Assimilation

1989 ◽  
Vol 44 (1-2) ◽  
pp. 97-102 ◽  
Author(s):  
Aloysius Wild ◽  
Christine Ziegler
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Ammonium Assimilation ◽  
Inhibiting Effect ◽  
Whole Plants ◽  
Leaf Homogenate

Abstract In this investigation, the effect of bialaphos (phosphinothricyl-alanyl-alanine) on the enzymes involved in NH4+-assimilation - glutamine synthetase, glutamine-2-oxoglutarate aminotransferase, glutamate dehydrogenase - is examined and compared to the effect of phosphinothricin (glufosinate) on the same enzymes. Bialaphos was given to whole plants (in vivo) and to leaf homogenate (in vitro). The investigation showed that bialaphos has an inhibiting effect on glutamine synthetase in vivo, but not in vitro. In contrast to this, phosphinothricin inhibits glutamine synthetase in vitro as well as in vivo. It was found that bialaphos, similar to phosphinothricin, does not inhibit glutamine-2-oxoglutarate aminotransferase and glutamate dehydrogenase in vivo or in vitro. Only at bialaphos concentrations exceeding 10 mM, there is an inhibition of glutamate dehydrogenase in vitro. Using radioactive [3H]bialaphos (phosphinothricyl-3H-alanyl-alanine) it could be demonstrated that in the plant, bialaphos is split into phosphinothricin and alanine. The phosphinothricin released is probably the active herbicide component. Consequently, the herbicidal effects of phosphinothricin and bialaphos are the same.

The green hydra symbiosis and ammonium. I. The role of the host in ammonium assimilation and its possible regulatory significance

1986 ◽  
Vol 229 (1256) ◽  
pp. 299-314 ◽  
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Ammonium Assimilation ◽  
Nitrogen Status ◽  
Continuous Darkness ◽  
Methionine Sulphoximine ◽  
Vacuolar Ph ◽  
Regulatory Significance

Evidence for ammonium assimilation by host and symbiont in algal─invertebrate symbioses is summarized and critically evaluated. The host from all strains of hydra studied possessed glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities. The host from associations with high maltose releasing algae (E/E, E /3N8) had high GS and low GDH activities, whereas aposymbiotic animals (EALB) and the association with a low maltose releasing alga (E/NC) had low GS and high GDH activities. The observation that symbiotic animals do not release ammonium in the light, whereas aposymbiotic animals release substantial amounts, may be explicable on the basis of variation in the ability of the host to assimilate ammonium. Thus, the photosynthetic inhibitor DCMU had no effect on ammonium release by symbiotic animals, with the possible exception of E/NC. Methionine sulphoximine (MSO) completely inhibited GS activity from EALB both in vitro and in vivo . In the presence of MSO, ammonium release was enhanced in both EALB and E/E. In continuous darkness, an increase in ammonium released by symbiotic animals (E/E) was correlated with a decrease in host GS activity. It is suggested that the evidence is consistent with host and not symbiont assimilation of ammonium. A model of symbiont regulation is proposed based on regulation of ammonium supply as a means of controlling both perialgal vacuolar pH and symbiont nitrogen status.

scholarly journals Oxidative Turnover of Soybean Root Glutamine Synthetase. In Vitro and in Vivo Studies

1999 ◽  
Vol 119 (4) ◽  
pp. 1483-1496 ◽  
Author(s):  
Jose Luis Ortega ◽  
Dominique Roche ◽  
Champa Sengupta-Gopalan
Keyword(s):  
Glutamine Synthetase ◽  
In Vivo Studies ◽  
Soybean Root

scholarly journals Cellular Location and Concentration of Leghaemoglobin in Soybean Root Nodules

1973 ◽  
Vol 26 (4) ◽  
pp. 741 ◽  
Author(s):  
FJ Bergersen ◽  
DJ Goodchild
Keyword(s):  
Root Nodule ◽  
Root Nodules ◽  
Fresh Tissue ◽  
Cellular Location ◽  
Soybean Root ◽  
Tissue Sections

The reaction of leghaemoglobin (Lb) with oxidized 3,3'-diaminobenzidine has been used to demonstrate the localization of this haemoprotein within the membrane envelopes surrounding the bacteroids in soybean root nodule cells. In fresh tissue sections mounted in a modified Honda medium, the reagent stained the envelope contents a brick-red colour.

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