The plant as the genetic determinant of leghaemoglobin production in the legume root nodule.
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Acrylates↗
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Results for “Plant Root Nodulation”
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Effect of cadmium on nodulation and N2-fixation of soybean in contaminated soils.
The effects of cadmium stress on nodulation, N2-fixation capabilities of the root nodule, the change in ultrastructure of the root nodule, soybean growth, and the distribution of cadmium in plants were studied. The results obtained show that the nodulation of soybean roots was greatly inhibited by the addition of Cd, especially at the addition level of 10 and 20 mg kg(-1) soil. The inhibition of plant growth, especially the root growth, increased as the cadmium concentration increased, with deleterious effects observed for the roots. The weight ratio of soybean root/leaf decreased as the Cd concentration increased, which might explain the reason for nodulation decreases. The results also indicate that N2-fixation of root nodule was stimulated to some extent at the low levels of Cd addition, but decreased sharply with further increase of the Cd concentration. High Cd levels were also associated with changes in the ultrastructure of root nodule, in which the effective N2-fixing area was reduced and the N2-fixing cells in the area also reduced. In addition, the results also reveal that the content of Cd in different parts of the plants was as follows: roots >> stems > seeds, indicating that the accumulation of Cd by roots is much larger than that by any other part of the soybean plant, and might cause deleterious effects to root systems.
Cadmium↗
Two Isoenzymes of NADH-dependent Glutamate Synthase in Root Nodules of Phaseolus vulgaris L: Purification, Properties and Activity Changes during Nodule Development.
The specific activity of plant NADH-dependent glutamate synthase (NADH-GOGAT) in root nodules of Phaseolus vulgaris L. is over threefold higher than the specific activity of ferredoxin-dependent GOGAT. The NADH-GOGAT is composed of two distinct isoenzymes (NADH-GOGAT I and NADH-GOGAT II) which can be separated from crude nodule extracts by ion-exchange chromatography. Both NADH-GOGAT isoenzymes have been purified to apparent homogeneity and shown to be monomeric proteins with similar M(r)s of about 200,000. They are both specific for NADH as reductant. An investigation of their kinetic characteristics show slight differences in their K(m)s for l-glutamine, 2-oxoglutarate, and NADH, and they have different pH optima, with NADH-GOGAT I exhibiting a broad pH optimum centering at pH 8.0 whereas NADH-GOGAT II has a much narrower pH optimum of 8.5. The specific activity of NADH-GOGAT in roots is about 27-fold lower than in nodules and consists almost entirely of NADH-GOGAT I. During nodulation both isoenzymes increase in activity but the major increase is due to NADH-GOGAT II which increases over a time course similar to the increase in nitrogenase activity. This isoenzyme is twice as active as NADH-GOGAT I in mature nodules. The roles and regulation of these two isoenzymes in the root nodule are discussed.
Journal Article↗
Nodule initiation involves the creation of a new symplasmic field in specific root cells of medicago species.
The organogenesis of nitrogen-fixing nodules in legume plants is initiated in specific root cortical cells and regulated by long-distance signaling and carbon allocation. Here, we explore cell-to-cell communication processes that occur during nodule initiation in Medicago species and their functional relevance using a combination of fluorescent tracers, electron microscopy, and transgenic plants. Nodule initiation induced symplasmic continuity between the phloem and nodule initials. Macromolecules such as green fluorescent protein could traffic across short or long distances from the phloem into these primordial cells. The created symplasmic field was regulated throughout nodule development. Furthermore, Medicago truncatula transgenic plants expressing a viral movement protein showed increased nodulation. Hence, the establishment of this symplasmic field may be a critical element for the control of nodule organogenesis.
Biological Transport↗
Demonstration of the isolation of non-infective Alnus crispa var. mollis Fern, nodule endophyte by morphological immunolabelling and whole cell composition studies.
Two filamentous, branched, and septate actinomycetes were isolated from field-collected and from axenic in vitro produced root nodules of Alnus crispa var. mollis Fern. host plant. After their transfer to a chemically defined medium, these nodule isolates could not be distinguished from each other on the basis of morphology, cultural reactions, and whole cell composition and were considered to be the same species. They were morphologically similar to the root nodule endophyte, but were incapable of nodulating aseptic host plants growing in a nitrogen-deficient substrate. Whole cells of the nodule isolates were used for the production of rabbit antibodies. The resulting specific antiisolate antibodies were conjugated with fluorescein isothiocyanate and used in staining tests of the nodule endophyte. The immunofluorescence reactions demonstrated the homology of the nodule isolates with the nodule endophyte. After pectinase degradation of the endophyte capsule, the indirect immunoferritin method corroborated the fluorescent anti-body (FA) staining reactions. There was no antigenic relationship between the nodule isolates and 13 known strains of actinomycetes as determined by the FA techique. Fluorescent antibody reactions of adsorbed conjugates suggested that endophytes of both Alnus crispa var. mollis Fern. and Alnus rugosa (DuRoi) Spreng. root nodules belong to a common serotype. The LL and mesoisomers of diaminopimelic acid were present in similar proportions in the nodule endophyte and in the nodule isolates. Glucose, mannose, and an unknown sugar were the predominant whole cell sugars in the nodule isolates, although trace amounts of arabinose and rhamnose were also displayed. The unknown sugar found in the nodule isolates was also present in trace amounts in the endophyte-suspension hydrolysate.
Actinomycetales↗
Shoot-applied polyamines suppress nodule formation in soybean (Glycine max).
In legumes, the number of root nodules is controlled by a mechanism called autoregulation. Recently, we found that the foliar brassinosteroid (BR), a plant growth-regulating hormone, systemically regulates the nodule number in soybean plants. In the present study we report that such down-regulation of root nodule formation by a BR may occur through a change of the polyamine contents, with the experimental evidence as follows. The foliar contents of both spermidine (Spd) and spermine (Spm) in the super-nodulating soybean mutant, En6500, were always lower than those in its parent line, Enrei. This lower Spd and Spm content accompanied a striking accumulation of putrescine (Put) in the former plant. This finding indicates that Spd and Spm biosynthesis from their precursor Put is repressed in En6500. The foliar treatments with Spd or Spm of En6500 led to a reduction of both nodule number and root growth. On the other hand, foliar treatment with MDL74038, a specific inhibitor of Spd biosynthesis, apparently increased the root nodule number in Enrei. Foliar application of brassinolide (BL) of En6500 increased the leaf Spd level and reduced the nodule number. These results suggested that BL-induced Spd synthesis in shoots might suppress the root nodule formation.
Brassinosteroids↗
[Serologic characteristics of root nodule bacteria].
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Bacteria↗
[Studies on root nodule bacteria].
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Bacteria↗
Characterization of Rhizobia from Ineffective Alfalfa Nodules: Ability to Nodulate Bean Plants [Phaseolus vulgaris (L.) Savi.].
This study was initiated to characterize Rhizobium isolates obtained from root nodules of ineffectively nodulated, field-grown alfalfa (Medicago sativa L.) plants. The purpose was to determine if these isolates possessed characteristics which would explain either their ineffectiveness in N(2) fixation or their apparent ability to tolerate the moderately acid soil conditions from which they originated. Isolates were characterized by analysis of growth rate, 39 degrees C tolerance, acid production on conventional media, and symbiotic performance. All isolates were ineffective in N(2) fixation on alfalfa, and they contained one or more anomalous characteristics. These included either slow growth rate, lack of 39 degrees C tolerance, or lack of acid production on conventional media. Infectiveness tests on a broad range of legumes revealed that the isolates formed root nodules on M. sativa, Medicago lupulina L., and Phaseolus vulgaris (L.) Savi. (common bean). These results provide evidence that, in some situations, ineffective nodulation of M. sativa in the field may be due to the presence of promiscuous, native Rhizobium species.
Journal Article↗
Effect of salinity on root-nodule conductance to the oxygen diffusion in the Cicer arietinum-Mesorhizobium ciceri symbiosis.
Nodule conductance to O2 diffusion has been involved as a major factor of the inhibition of N2 fixation by soil salinity that severely reduces the production of grain legumes. In order to determine the effect of this constraint on the nodule conductance, oxygen uptake by the nodulated roots of Cicer arietinum was measured by recording the concentration of O2 as a function of pO2 in a gas-tight incubator. After germination and inoculation with the strain Mesorhizobium ciceri UPMCa7, the varieties Amdoun 1 and INRAT 93-1 were hydroponically grown in a glasshouse on 1L glass bottles filled with nutrient solution containing 25 mM NaCl. Salinity induced a marked decrease in shoot (30% versus 14%), root (43% versus 20%), and nodule biomass (100% versus 43%) for Amdoun 1 relative to INRAT 93-1. Although salinity completely prevented nodule formation in the sensitive variety Amdoun 1, nodule number and biomass were higher in the first than in the second variety in the absence of salt. This effect was associated with a significantly higher O2 uptake by nodulated root (510 versus 255 micromol O2 plant(-1)h(-1)) and nodule conductance (20 versus 5 microm s(-1)) in Amdoun 1 than in INRAT 93-1. Salinity did not significantly change the nodule conductance and nodule permeability for INRAT 93-1. Thus, the salt tolerance of this variety appears to be associated with stability in nodule conductance and the capacity to form nodules under salt constraint.
Biomass↗
Plant delta-aminolevulinic acid dehydratase. Expression in soybean root nodules and evidence for a bacterial lineage of the Alad gene.
We isolated a soybean (Glycine max) cDNA encoding the heme and chlorophyll synthesis enzyme delta-aminolevulinic acid (ALA) dehydratase by functional complementation of an Escherichia coli hemB mutant, and we designated the gene Alad. ALA dehydratase was strongly expressed in nodules but not in uninfected roots, although Alad mRNA was only 2- to 3-fold greater in the symbiotic tissue. Light was not essential for expression of Alad in leaves of dark-grown etiolated plantlets as discerned by mRNA, protein, and enzyme activity levels; hence, its expression in subterranean nodules was not unique in that regard. The data show that soybean can metabolize the ALA it synthesizes in nodules, which argues in favor of tetrapyrrole formation by the plant host in that organ. Molecular phylogenetic analysis of ALA dehydratases from 11 organisms indicated that plant and bacterial enzymes have a common lineage not shared by animals and yeast. We suggest that plant ALA dehydratase is descended from the bacterial endosymbiont ancestor of chloroplasts and that the Alad gene was transferred to the nucleus during plant evolution.
Amino Acid Sequence↗
[Effect of bound nitrogen compounds on nitrogen-fixing activity of root-nodule bacteria in root nodules of soy and bean and their relation to leguminous plants].
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Bacteria↗
A protein phosphatase 2C gene, LjNPP2C1, from Lotus japonicus induced during root nodule development.
Symbiotic interactions between legumes and compatible strains of rhizobia result in root nodule formation. This new plant organ provides the unique physiological environment required for symbiotic nitrogen fixation by the bacterial endosymbiont and assimilation of this nitrogen by the plant partner. We have isolated two related genes (LjNPP2C1 and LjPP2C2) from the model legume Lotus japonicus that encode protein phosphatase type 2C (PP2C). Expression of the LjNPP2C1 gene was found to be enhanced specifically in L. japonicus nodules, whereas the LjPP2C2 gene was expressed at a similar level in nodules and roots. A glutathione S-transferase-LjNPP2C1 fusion protein was shown to have Mg2+- or Mn2+-dependent and okadaic acid-insensitive PP2C activity in vitro. A chimeric construct containing the full-length LjNPP2C1 cDNA, under the control of the Saccharomyces cerevisiae alcohol dehydrogenase promoter, was found to be able to complement a yeast PP2C-deficient mutant (pct1Delta). The transcript level of the LjNPP2C1 gene was found to increase significantly in mature nodules, and its highest expression level occurred after leghemoglobin (lb) gene induction, a molecular marker for late developmental events in nodule organogenesis. Expression of the LjNPP2C1 gene was found to be drastically altered in specific L. japonicus lines carrying monogenic-recessive mutations in symbiosis-related loci, suggesting that the product of the LjNPP2C1 gene may function at both early and late stages of nodule development.
Amino Acid Sequence↗
Physiological implications of trehalase from Phaseolus vulgaris root nodules: partial purification and characterization.
The purification and characterization of trehalase from common bean nodules as well as the role of this enzyme on growth, nodulation nitrogen fixation by examining the effects of the trehalase inhibitor validamycin A, was studied. Validamycin A did not affect plant and nodule mass, neither root trehalase and nitrogenase activity; however this treatment applied at the time of sowing increased nodule number about 16% and decreased nodule trehalase activity (16-fold) and the size of nodules. These results suggest that nodule trehalase activity of Phaseolus vulgaris could be involved in nodule formation and development. In addition, acid trehalase (EC 3.2.1.28) was purified from root nodules by fractionating ammonium sulfate, column chromatography on DEAE-sepharose and sephacryl S-300, and finally on native polyacrylamide gel electrophoresis. The purified homogeneous preparation of native acid trehalase exhibited a molecular mass of 42 and 45 kDa on SDS-PAGE. The enzyme has the optimum pH 3.9, Km of 0.109 mM, Vmax of 3630 nkat mg-1 protein and is relatively heat stable. Besides trehalose, it shows maximal activity with sucrose and maltose and, to a lesser degree melibiose, cellobiose and raffinose, and it does not hydrolyze on lactose and turanose. Acid trehalase was activated by Na+, Mn2+, Mg2+, Li+, Co2+, K+ and inhibited by Fe3+, Hg+ and EDTA.
Cations↗
Organic Acid contents of soybean: age and source of nitrogen.
The organic acid content of soybean (Glycine max v. Hodgson) root, stem, and leaf tissue was followed for 33 days after germination. Malonate was the predominant acid in leaf and root tissue, whereas fumarate was predominant in the stem. The malonate concentrations of the stem and root showed similar variations with time, but the leaf response was quite different. In nodules from 33-day-old plants, malonate was the predominant acid. Malonate levels in root and nodule tissue of 33-day-old plants were depressed in response to the addition of either nitrate or ammonia. Nodule tissue had a higher malonate concentration on nitrate nitrogen than it did on ammonium nitrogen, whereas root tissue had the higher malonate concentration on ammonium nitrogen. Analysis of organic acid concentrations of roots as a function of age and distance from the root tip in young soybean seedlings revealed a zone consistently high in malate. The malonate level in the entire root rose dramatically in tissue of age 96 to 120 hours.
Journal Article↗
Lipochitooligosaccharides and legume Rhizobium symbiosis--a new concept.
Legume-Rhizobium symbiosis is a multistep process characterized by the formation of root nodules on the host plant. A number of genes from both symbiotic partners share information during the interaction process. Nodulation genes (nod, nol and noe) have been classified as common nodulation genes and host specific (hsn) nodulation genes. Though common nodulation genes are enough to form root nodules, host specific nodulation genes are needed for specific interaction leading to formation of functional nodules. Core lipochitooligosaccharides (LCOs), the products of common nodulation genes are modified by the action of host specific nodulation genes. LCOs seem to be present in legumes as well as nonlegume and are known to act as a morphogen by acting as auxin-transport inhibitor. The understanding of Nod factor may contribute to reveal complex biological functions such as developmental regulation, signal transduction and plant morphogenesis.
Fabaceae↗
Respiration and the energy requirement for nitrogen fixation in nodulated pea roots.
Pisum sativum L. cv. Trapper plants were inoculated and grown in a controlled environment on N-free nutrient solution. After 4 weeks N was supplied to treatment plants as NH(4)NO(3), KNO(3), or NH(4)Cl and rates of C(2)H(2) reduction, root + nodule respiration, and leaf photosynthesis were determined 1 week later. The increase in respiration per unit of C(2)H(2) reduction was not affected by either the form of N added or the light conditions during growth, although the basal respiration rate with no C(2)H(2) reduction increased with irradiance level. The mean regression coefficient from plots of respiration versus C(2)H(2) reduction was 0.23 + 0.04 (P [unk] .01) mg of CO(2) (mumol of C(2)H(2) reduced)(-1) which was very similar to the value for the coefficient of respiration associated with nitrogenase activity estimated by subtracting growth and maintenance respiration. Since the rate of N accumulation in N-free nutrient conditions was proportional to the rate of C(2)H(2) reduction, it appears that the method gives a true estimate of the energy requirements for N fixation which for these conditions was equivalent to 17 grams of carbohydrate consumed per gram of N fixed.
Journal Article↗
Comparison of nodule induction in legume and actinorhizal symbioses: the induction of actinorhizal nodules does not involve ENOD40.
Two types of root nodule symbioses are known for higher plants, legume and actinorhizal symbioses. In legume symbioses, bacterial signal factors induce the expression of ENOD40 genes. We isolated an ENOD40 promoter from an actinorhizal plant, Casuarina glauca, and compared its expression pattern in a legume (Lotus japonicus) and an actinorhizal plant (Allocasuarina verticillata) with that of an ENOD40 promoter from the legume soybean (GmENOD40-2). In the actinorhizal Allocasuarina sp., CgENOD40-GUS and GmENOD40-2-GUS showed similar expression patterns in both vegetative and symbiotic development, and neither promoter was active during nodule induction. The nonsymbiotic expression pattern of CgENOD40-GUS in the legume genus Lotus resembled the nonsymbiotic expression patterns of legume ENOD40 genes; however, in contrast to GmENOD40-2-GUS, CgENOD40-GUS was not active during nodule induction. The fact that only legume, not actinorhizal, ENOD40 genes are induced during legume nodule induction can be linked to the phloem unloading mechanisms established in the zones of nodule induction in the roots of both types of host plants.
Base Sequence↗