scholarly journals Expression Map for Genes Involved in Nitrogen and Carbon Metabolism in Alfalfa Root Nodules

1999 ◽  
Vol 12 (6) ◽  
pp. 526-535 ◽  
Author(s):  
Gian B. Trepp ◽  
Stephen J. Temple ◽  
Bruna Bucciarelli ◽  
Li Fang Shi ◽  
Carroll P. Vance
Keyword(s):  
Nitrogen Fixation ◽  
Glutamine Synthetase ◽  
Carbon Metabolism ◽  
Root Nodule ◽  
Root Nodules ◽  
Constitutive Expression ◽  
Nodule Development ◽  
Relative Distribution ◽  
Nitrogen Fixing ◽  
Alfalfa Root

During root nodule development several key genes involved in nitrogen fixation and assimilation exhibit enhanced levels of expression. However, little is known about the temporal and spatial distribution patterns of these transcripts. In a systematic study the transcripts for 13 of the essential enzymes involved in alfalfa (Medicago sativa) root nodule nitrogen and carbon metabolism were localized by in situ hybridization. A serial section approach allowed the construction of a map that reflects the relative distribution of these transcripts. In 33-day-old root nodules, the expression of nifH, NADH-dependent glutamate synthase (NADH-GOGAT; EC 1.4.1.14) and a cytosolic isoform of glutamine synthetase (GS13; GS; EC 6.3.1.2) were localized predominantly in a 5- to 15-cell-wide region in the distal part of the nitrogen-fixing zone. This zone was also the region of high expression for leghemoglobin, a second cytosolic glutamine synthetase isoform (GS100), aspartate aminotransferase-2 (AAT-2; EC 2.6.1.1), asparagine synthetase (AS; 6.3.5.4), phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31), and sucrose synthase (SuSy; EC 2.4.1.13). This suggests that, in 33-day-old alfalfa root nodules, nitrogen fixation is restricted to this 5- to 15-cell-wide area. The continued significant expression of the GS100 subclass of GS and AS in the proximal part of the nitrogen-fixing zone implicates these gene products in nitrogen remobilization. A low constitutive expression of NADH-dependent glutamate dehydrogenase (NADH-GDH; EC 1.4.1.2) was observed throughout the nodule. The transcript distribution map will be used as a navigational tool to assist in developing strategies for the genetic engineering of alfalfa root nodules for enhanced nitrogen assimilation.

Nitrogen fixation in legume root nodules: biochemical studies with soybean

1969 ◽  
Vol 172 (1029) ◽  
pp. 401-416 ◽  
Keyword(s):  
Nitrogen Fixation ◽  
Root Nodule ◽  
Root Nodules ◽  
Reducing Power ◽  
Nitrogen Fixing ◽  
Nodule Bacteria ◽  
Stages Of Growth ◽  
Host Cytoplasm ◽  
Photosynthetic Product ◽  
Power And Energy

It is now clear from studies with soybean root nodules that the nitrogen fixing activity resides in the bacteroids which are the symbiotic form of the root nodule bacteria. These develop as a result of a complex series of changes in metabolism and structure which occur in the bacteria during the final stages of growth within membrane-enclosed vesicles in the host cytoplasm. Nitrogenase appears when these changes are complete. The primary product of nitrogen fixation is NH 3 , which in intact nodules, is rapidly transformed into α -amino compounds which are used by the host plant. In suspensions of bacteroids and in cell-free extracts prepared from them, the reaction terminates in NH 3 , which is released into the medium. Free O 2 , which is required for the production of energy for nitrogen fixation by nodules and by bacteroid suspensions, also causes inactivation of the nitrogen fixing system and exerts important kinetic influences upon the reaction. Reducing power and energy for the reduction of N 2 to NH 3 is provided by a photosynthetic product from the host in nodules; in bacteroid suspensions, a substrate such as succinate is required. In cell-free extracts, requirements for energy and reductant are met by ATP and dithionite. The natural reductant has not yet been identified. A schematic representation of various factors which affect nitrogen fixation in nodules, bacteroid suspensions and cell-free extracts is presented.

scholarly journals A New Species of Devosia That Forms a Unique Nitrogen-Fixing Root-Nodule Symbiosis with the Aquatic Legume Neptunia natans (L.f.) Druce

2002 ◽  
Vol 68 (11) ◽  
pp. 5217-5222 ◽  
Author(s):  
Raul Rivas ◽  
Encarna Velázquez ◽  
Anne Willems ◽  
Nieves Vizcaíno ◽  
Nanjappa S. Subba-Rao ◽  
...  
Keyword(s):  
Root Nodule ◽  
Root Nodules ◽  
Infection Process ◽  
Nitrogen Fixing ◽  
Rhizobium Tropici ◽  
Rdna Sequences ◽  
Root Nodule Symbiosis ◽  
16S Rdna Sequences ◽  
The Common ◽  
Nodule Symbiosis

ABSTRACT Rhizobia are the common bacterial symbionts that form nitrogen-fixing root nodules in legumes. However, recently other bacteria have been shown to nodulate and fix nitrogen symbiotically with these plants. Neptunia natans is an aquatic legume indigenous to tropical and subtropical regions and in African soils is nodulated by Allorhizobium undicola. This legume develops an unusual root-nodule symbiosis on floating stems in aquatic environments through a unique infection process. Here, we analyzed the low-molecular-weight RNA and 16S ribosomal DNA (rDNA) sequence of the same fast-growing isolates from India that were previously used to define the developmental morphology of the unique infection process in this symbiosis with N. natans and found that they are phylogenetically located in the genus Devosia, not Allorhizobium or Rhizobium. The 16S rDNA sequences of these two Neptunia-nodulating Devosia strains differ from the only species currently described in that genus, Devosia riboflavina. From the same isolated colonies, we also located their nodD and nifH genes involved in nodulation and nitrogen fixation on a plasmid of approximately 170 kb. Sequence analysis showed that their nodD and nifH genes are most closely related to nodD and nifH of Rhizobium tropici, suggesting that this newly described Neptunia-nodulating Devosia species may have acquired these symbiotic genes by horizontal transfer.

scholarly journals Expression Analysis of PIN Genes in Root Tips and Nodules of Lotus japonicus

2019 ◽  
Vol 20 (2) ◽  
pp. 235 ◽  
Author(s):  
Izabela Sańko-Sawczenko ◽  
Dominika Dmitruk ◽  
Barbara Łotocka ◽  
Elżbieta Różańska ◽  
Weronika Czarnocka
Keyword(s):  
Root Nodule ◽  
Root Nodules ◽  
Quantitative Polymerase Chain Reaction ◽  
Lotus Japonicus ◽  
Nodule Development ◽  
Vascular Bundles ◽  
Root Tips ◽  
Gus Reporter ◽  
Gene Assay ◽  
Development And Differentiation

Auxins are postulated to be one of the pivotal factors in nodulation. However, their transporters in Lotus japonicus, the model species for the study of the development of determinate-type root nodules, have been scarcely described so far, and thus their role in nodulation has remained unknown. Our research is the first focusing on polar auxin transporters in L. japonicus. We analyzed and compared expression of PINs in 20 days post rhizobial inoculation (dpi) and 54 dpi root nodules of L. japonicus by real-time quantitative polymerase chain reaction (qPCR) along with the histochemical β-glucuronidase (GUS) reporter gene assay in transgenic hairy roots. The results indicate that LjPINs are essential during root nodule development since they are predominantly expressed in the primordia and young, developing nodules. However, along with differentiation, expression levels of several PINs decreased and occurred particularly in the nodule vascular bundles, especially in connection with the root’s stele. Moreover, our study demonstrated the importance of both polar auxin transport and auxin intracellular homeostasis during L. japonicus root nodule development and differentiation.

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.

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 FrankiaDiversity in Host Plant Root Nodules Is Independent of Abundance or Relative Diversity ofFrankiaPopulations in Corresponding Rhizosphere Soils

2017 ◽  
Vol 84 (5) ◽  
Author(s):  
Seifeddine Ben Tekaya ◽  
Trina Guerra ◽  
David Rodriguez ◽  
Jeffrey O. Dawson ◽  
Dittmar Hahn
Keyword(s):  
Host Plant ◽  
Root Nodule ◽  
Root Nodules ◽  
Actinorhizal Plants ◽  
Nodule Formation ◽  
Nitrogen Fixing ◽  
Content Type ◽  
Rhizosphere Soils ◽  
Root Nodule Formation ◽  
Host Infection

ABSTRACTActinorhizal plants form nitrogen-fixing root nodules in symbiosis with soil-dwelling actinobacteria within the genusFrankia, and specificFrankiataxonomic clusters nodulate plants in corresponding host infection groups. In same-soil microcosms, we observed that some host species were nodulated (Alnus glutinosa,Alnus cordata,Shepherdia argentea,Casuarina equisetifolia) while others were not (Alnus viridis,Hippophaë rhamnoides). Nodule populations were represented by eight different sequences ofnifHgene fragments. Two of these sequences characterized frankiae inS. argenteanodules, and three others characterized frankiae inA. glutinosanodules. Frankiae inA. cordatanodules were represented by five sequences, one of which was also found in nodules fromA. glutinosaandC. equisetifolia, while another was detected in nodules fromA. glutinosa. Quantitative PCR assays showed that vegetation generally increased the abundance of frankiae in soil, independently of the target gene (i.e.,nifHor the 23S rRNA gene). Targeted Illumina sequencing ofFrankia-specificnifHgene fragments detected 24 unique sequences from rhizosphere soils, 4 of which were also found in nodules, while the remaining 4 sequences in nodules were not found in soils. Seven of the 24 sequences from soils represented >90% of the reads obtained in most samples; the 2 most abundant sequences from soils were not found in root nodules, and only 2 of the sequences from soils were detected in nodules. These results demonstrate large differences between detectableFrankiapopulations in soil and those in root nodules, suggesting that root nodule formation is not a function of the abundance or relative diversity of specificFrankiapopulations in soils.IMPORTANCEThe nitrogen-fixing actinobacteriumFrankiaforms root nodules on actinorhizal plants, with members of specificFrankiataxonomic clusters nodulating plants in corresponding host infection groups. We assessedFrankiadiversity in root nodules of different host plant species, and we related specific populations to the abundance and relative distribution of indigenous frankiae in rhizosphere soils. Large differences were observed between detectableFrankiapopulations in soil and those in root nodules, suggesting that root nodule formation is not a function of the abundance or relative diversity of specificFrankiapopulations in soils but rather results from plants potentially selecting frankiae from the soil for root nodule formation. These data also highlight the necessity of using a combination of different assessment tools so as to adequately address methodological constraints that could produce contradictory data sets.

Starch content and activities of starch-metabolizing enzymes in effective and ineffective root nodules of soybean

1991 ◽  
Vol 69 (4) ◽  
pp. 697-701 ◽  
Author(s):  
Sharon I. Forrest ◽  
Desh Pal S. Verma ◽  
Rajinder S. Dhindsa
Keyword(s):  
Nitrogen Fixation ◽  
Starch Content ◽  
Root Nodules ◽  
Starch Synthase ◽  
Nodule Development ◽  
Wild Type ◽  
Starch Phosphorylase ◽  
High Concentration ◽  
Key Words Nitrogen Fixation ◽  
Glycine Max L

Starch content and activities of some enzymes of starch metabolism were determined in wild-type, N2-fixing (fix+) nodules and in two non-N2-fixing (fix−) nodules induced by Bradyrhizobium japonicum mutant strains, T5-95 and T8-1, on soybean (Glycine max L.) roots. The T5-95 nodules are similar to wild type in ultrastructure, but the T8-1 nodules are different in that the bacteroids are not released from the infection thread. After initial accumulation to relatively high concentration, starch was depleted during nitrogen fixation in fix+ nodules. However, in fix− nodules, the accumulated starch was not metabolized. The activity of starch-bound starch synthase (EC 2.4.1.21) declined in fix+ nodules but remained high in fix− nodules. The activity of α-amylase (EC 3.2.1.1) was only slightly higher than wild type in T5-95 but was four times higher than wild type in T8-1 nodules. The activity of starch phosphorylase (EC 2.4.1.1) increased in all nodule types from 14 to 21 days postinfection. A positive correlation was observed between the capacity of nodules to fix N2 and their capacity to degrade starch. Collectively, these results support the concept that starch accumulated during early stages of nodule development is metabolized to supply energy for nitrogen fixation and to meet the metabolic demands of bacteroids. Key words: nitrogen fixation, starch content, effective and ineffective nodules, starch synthase, starch phosphorylase, α-amylase.

Sign in / Sign up

Export Citation Format

Share Document