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PubMed1984

Experimental determination of the respiration associated with soybean/rhizobium nitrogenase function, nodule maintenance, and total nodule nitrogen fixation.

The total metabolic cost of soybean (Glycine max L. Mer Clark) nodule nitrogen fixation was empirically separated into respiration associated with electron flow through nitrogenase and respiration associated with maintenance of nodule function.Rates of CO(2) evolution and H(2) evolution from intact, nodulated root systems under Ar:O(2) atmospheres decreased in parallel when plants were maintained in an extended dark period. While H(2) evolution approached zero after 36 hours of darkness at 22 degrees C, CO(2) evolution rate remained at 38 degrees of the rate measured in light. Of the remaining CO(2) evolution, 62% was estimated to originate from the nodules and represents a measure of nodule maintenance respiration. The nodule maintenance requirement was temperature dependent and was estimated at 79 and 137 micromoles CO(2) (per gram dry weight nodule) per hour at 22 degrees C and 30 degrees C, respectively.The cost of N(2) fixation in terms of CO(2) evolved per electron pair utilized by nitrogenase was estimated from the slope of H(2) evolution rate versus CO(2) evolution rate. The cost was 2 moles CO(2) evolved per mole H(2) evolved and was independent of temperature.In this symbiosis, nodule maintenance consumed 22% of total respiratory energy while the functioning of nitrogenase consumed a further 52%. The remaining respiratory energy was calculated to be associated with ammonia assimilation, transport of reduced N, and H(2) evolution.

Journal Article↗

PubMed1990

Nodulation of Soybean by a Transposon-Mutant of Rhizobium fredii USDA257 Is Subject to Competitive Nodulation Blocking by Other Rhizobia.

Rhizobium fredii USDA257 fails to nodulate the improved soybean [Glycine max (L.)Merr.] cultivar McCall in plastic growth pouches. Mutant 257DH4, which was derived from USDA257 by transposon mutagenesis, forms nitrogen fixing nodules under these conditions. If USDA257 is present in inocula containing the mutant, most infections are arrested prior to organization of the nodule meristem, and nodule number is reduced by 95%. The improved cultivars Essex, Harosoy, Hodgson 78, and Viçoja, as well as a supernodulating mutant of Williams, respond like McCall to inoculation with such mixtures of bacteria. Nodulation blocking on McCall can be elicited by rhizobia other than USDA257, provided that they meet two criteria: Blocking strains must themselves be able to induce cortical cells of McCall to divide, and such divisions must proceed to the stage of nodule meristem formation. Nodulation by the mutant remains sensitive to a challenge inoculation with USDA257 for only the first 6 to 12 hours after inoculation. Nodulation blocking involving mutant 257DH4 thus appears to be a rapid, generalized process.

Journal Article↗

PubMed1991

Effect of localized nitrate application on isoflavonoid concentration and nodulation in split-root systems of wild-type and nodulation-mutant soybean plants.

Although isoflavonoids are known to be inducers of nod genes in Bradyrhizobium japonicum, it was recently proposed that internal root levels of isoflavonoids may be important in nodule development on soybean (Glycine max [L.] Merr.). The hypernodulating soybean mutants were shown to accumulate higher root concentrations of isoflavonoid compounds (daidzein, genistein, and coumestrol) and to be more extensively nodulated than was the Williams parent when inoculated with B. japonicum. The hypernodulating mutants and the parent line, Williams, also showed decreased isoflavonoid concentrations and decreased nodule development if N was applied. The current study evaluated the effect of localized NO(3) (-) application on root isoflavonoid concentration and on nodulation in split-root systems of the Williams wild type and a hypernodulating mutant (NOD1-3). Nitrate application markedly decreased isoflavonoid concentrations in non-inoculated soybean roots. When roots were inoculated, nodule number, weight, and nitrogenase activity were markedly suppressed on the root-half receiving 5 millimolar NO(3) (-) compared with the other root-half receiving 0 millimolar NO(3) (-). High performance liquid chromatographic analyses of root extracts showed that the root-half receiving 5 millimolar NO(3) (-) was markedly lower in isoflavonoid concentrations in both soybean lines. This was partially due to the localized stimulatory effect of NO(3) (-) on root growth. The inoculated NOD1-3 mutant had higher isoflavonoid concentrations than did the Williams control in both the presence and absence of NO(3) (-). These results provide evidence that the site of N application primarily controls the site of nodulation inhibition, possibly through decreasing isoflavonoid levels. Although the effect of NO(3) (-) on nodule development and root isoflavonoid concentration was strongly localized, there was evidence that NO(3) (-) also resulted in a systemic effect on root isoflavonoids. The results are consistent with previous speculation that internal levels of root isoflavonoids may affect nodule development.

Journal Article↗

PubMed1985

Regulation of Nodulation by Rhizobium meliloti 102F15 on Its Mutant Which Forms an Unusually High Number of Nodules on Alfalfa.

A mutant (WL3A150) of Rhizobium meliloti 102F51 that elicits an unusually high number of nodules on its host, alfalfa (Medicago sativa), supports the idea that the host may rely on early bacteroid development in the nodule or on metabolites produced in the infection thread as one of the signals to control further nodulation. This mutant was initially isolated because of its Fix phenotype. It consistently formed many more nodules than all the other Fix mutants isolated from strain 102F51 (a total of 11 mutants). Nodules formed by this mutant were small and white and were indistinguishable in appearance from nodules formed by the other Fix mutants. An ultrastructural study of the nodules, however, showed that this mutant, although forming numerous infection threads, failed to develop into bacteroids. The ability of the mutant to form an unusually high number of nodules coulde be suppressed in a time-dependent manner by the presence of the wild type.

Journal Article↗

PubMed1990

Enhanced Nodulation and Nitrogen Fixation by a Revertant of a Nodulation-Defective Bradyrhizobium japonicum Tryptophan Auxotroph.

In greenhouse studies, the symbiotic properties of a prototrophic revertant (TA11 NOD) of a nodulation defective tryptophan auxotroph of Bradyrhizobium japonicum were compared with those of the normally nodulating wild-type strain, B. japonicum I-110 ARS. Strain I-110 ARS was the parent of auxotrophic mutant TA11. Plants inoculated with TA11 NOD contained significantly more nitrogen per plant than did plants inoculated with wild-type bacteria (275.9 +/- 35 versus 184 +/- 18 mg). Also, plants that received the revertant were larger, averaging 8.4 +/- 0.9 g (dry weight) versus 6.4 +/- 0.6 g for those that received the wild-type bacterial strain. Additionally, plants that received the NOD strain had 56% more nodules and 41% more nodule mass than did control plants. With both inocula, average nodule size and amount of nitrogen fixed per gram of nodule were about the same. These data indicated that the improvement in nitrogen fixation observed with the TA11 NOD resulted from an increase in the overall nodule number. The physiological basis for this increase in nodulation is not known, but enhanced tryptophan catabolism does not appear to be involved.

Journal Article↗

PubMed1963

Bacteriology of Manganese Nodules: I. Bacterial Action on Manganese in Nodule Enrichments.

Bacteria, found in manganese nodules from the Atlantic Ocean, enhance the adsorption of Mn from sea water by crushed manganese nodules in the presence of peptone. When bacterial outgrowth from crushed manganese nodules was experimentally delayed, peptone did not enhance Mn adsorption by nodular substance, but hindered it in some cases. A mechanism to explain the role of bacteria in enhancing Mn adsorption by manganese nodules is presented. Oyster shells were shown to adsorb Mn in the absence of bacteria. Peptone did not enhance the rate of Mn adsorption. Adsorbed Mn was not visibly oxidized during experimental observation. These results suggest one way whereby nodule formation may be initiated in the oceans. Some bacteria in the nodules were found to release manganese from them in the presence of glucose and peptone. Bacteria may, therefore, play a role not only in nodule buildup but also in nodule breakdown.

Journal Article↗

PubMed1977

Effect of rj1rj1 (non-nodulating) soybeans on nodulation of near isogenic Rj1Rj1 plants in nutrient culture.

An earlier proposal (Can. J. Microbiol. 7: 851; 1961) that rj1rj1 (non-nodulating) soybeans (Glycine max (L.) Merr.) excrete a substance that inhibits nodulation of Rj1 Rj1 (nodulating) plants was tested. Using near isogenic lines (isolines) of "Clark" and "Harosoy" soybeans, we consistently found nonsignificant reduction in nodule number and acetylene reduction per Rj1Rj1 plant grown in association with their rj1rj1 counterparts: these results suggest that a nodulation inhibitor is not associated with the rj1 gene. Reducing the number of plants grown in each pot produced significant (P = 0.05) reductions in nodule number per Rj1Rj1 plant, and resembled the observations of the earlier report. On this basis, we suggest that the reported inhibition of nodulation was due to a failure to detoxify or remove an inhibitor (possibly nitrate) already present in the nutrient solution. Both Clark isolines removed nitrate from their nutrient solutions at similar rates. Harosoy rj1rj1 plants removed nitrate at a significantly (P - 0.05) slower rate than Harosoy Rj1Rj1 plants, but the differences were not correlated (P = 0.05) with the small observed decreases in nodulation. These differences in nitrate uptake were highly correlated (P = 0.01) with reduced dry weight per Harosoy rj1rj1 plant.

Acetylene↗

PubMed1980

Nodulation of soybeans carrying the nodulation-restrictive gene, rj1, by an incompatible Rhizobium japonicum strain upon mixed inoculation with a compatible strain.

The rj1 gene in soybeans prevents nodulation by most strains of Rhizobium japonicum. Several strains, however, are known to nodulate rj1 plants in vermiculite or sand culture. Pure broth cultures of one of these strains (61 NalR) and a strain producing the typical non-nodulating response with rj1 (I-110 ARS) were mixed and used as inoculum on Clark rj1 soybeans in a growth chamber experiment. Both strains carried drug resistance markers and were identified using selective media. Analysis of the nodules formed indicated that 32% of the nodules contained both strains, 36% contained only the usually non-nodulating strain I-110 ARS, and 32% contained the usually infective strain (61 NalR). These results indicate that under conditions of high inoculum density the roots of Clark rj1 plants did not distinguish between Rhizobium strains 61 NalR and I-110 ARS. Subsequent tests with Rhizobium isolates from the nodules containing only strain I-110 ARS indicated that these rhizobia had not undergone a permanent genetic change in nodulation potential but were infective only because of temporary association with strain 61 NalR.

Culture Media↗

PubMed1978

Membranes in lupin root nodules. II. Preparation and properties of peribacteroid membranes and bacteroid envelope inner membranes from developing lupin nodules.

Peribacteroid membranes and bacteroid envelope inner membranes have been isolated from developing lupin nodules. Isolation of the peribacteroid membranes was achieved by first preparing membrane-enclosed bacteroids free from other plant organelles or membranes. The peribacteroid membranes were then released by osmotic shock and purified by centrifugation to equilibrium on sucrose gradients. The bacteroids were broken in a pressure cell and the bacteroid envelope inner membranes were isolated using sucrose gradient fractionation of the bacteroid total envelope preparation. The density of the peribacteroid membranes decreased during the period of development of N2-fixation in lupin nodules from 1.148 g/ml for nodules from 12-day plants to 1.137 g/ml for nodules from 18-day plants. The density of the bacteroid envelope inner membranes from nodules from 18-day plants was 1-153 g/ml. The identity and homogeneity of the isolated membranes was established, by comparison with membranes in intact nodules, using phosphotungstic acid and silver staining of thin sections and particle densitites on faces of freeze-fracture replicas of the membranes. Analyses for NADH oxidase and succinate dehydrogenase, spectral analyses and gel-electrophoretic analysis of proteins were also used to characterize the membrane and soluble protein fractions from the nodules. The ratio of lipid to protein was 6.1 for the peribacteroid membranes and 2.5 for the bacteroid envelope inner membranes. Leghaemoglobin was localized in the plant cytoplasm in lupin nodules and not in the peribacteroid space.

Cell Fractionation↗

PubMedDate not supplied

Cell proliferation and cell loss in nodule-in-nodule hepatocellular carcinoma.

BACKGROUND/AIMS: In order to clarify the significance of the balance between cell proliferation and cell loss during the progression of hepatocellular carcinoma, 16 operative specimens of nodule-in-nodule hepatocellular carcinoma were investigated. METHODOLOGY: In 16 specimens, cell proliferation was evaluated by the expression of Ki-67 nuclear antigen, and cell loss was also examined by the method of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL). The expressions of p53 protein, bcl-2 protein and Fas antigen were also investigated to clarify the relationship between their expression and cell kinetics. RESULTS: The Ki-67 labeling index of the inner nodules was higher than that for the outer nodules (18.9% vs. 7.2%; p < 0.05) and the TUNEL labeling index of the inner nodules was also higher than that for the outer nodules (12.8% vs. 6.6%; p < 0.05). The increasing rate of the Ki-67 labeling index from Edmondson's grade I to II was 3.9 +/- 3.0, that from grade II to III was 3.9 +/- 2.4, while the increasing rate of the TUNEL labeling index from grade I to II was 2.7 +/- 0.3 and that from grade II to III was 1.7 +/- 0.2 (p < 0.05). p53 Protein was observed in 5 cases, while bcl-2 protein was found in 4 cases in the border area of the inner nodule. However, Fas antigen was found in none of the examined cases. Regarding the Ki-67 positive rate in the inner nodule, the Ki-67 positive rate in the p53 protein positive cases was significantly higher than that in the negative cases (30.3 +/- 15.4 vs. 11.9 +/- 9.2; p < 0.05). However, the TUNEL labeling index was not affected by the expression of those proteins. CONCLUSIONS: This study suggested that tumor progression depends on a disturbance in the cell kinetic balance caused not by a decrease in the absolute amount of cell loss but in the chaotic balance between cell loss and cell proliferation.

Apoptosis↗

PubMed1998

Pathogenic mechanisms in the rheumatoid nodule: comparison of proinflammatory cytokine production and cell adhesion molecule expression in rheumatoid nodules and synovial membranes from the same patient.

OBJECTIVE: To investigate the production of proinflammatory cytokines and expression of cell adhesion molecules in the rheumatoid nodule. METHODS: Cytokine content (tumor necrosis factor alpha [TNFalpha], interleukin-1beta [IL-1beta], and IL-1 receptor antagonist [IL-1Ra]), at the messenger RNA (mRNA) and protein levels, and cell adhesion molecule expression were studied in 16 rheumatoid nodules and 6 synovial membranes. RESULTS: Macrophages in the rheumatoid nodules contained TNFalpha, IL-1beta, and IL-1Ra mRNA and protein, particularly in perivascular cells of the stroma and in the palisading layer. All cell adhesion molecules studied were expressed in both the rheumatoid nodules and synovial membranes, with increased expression of E-selectin in the rheumatoid nodule compared with the synovial membrane, and with the absence of vascular cell adhesion molecule 1 expression on cells of the palisading layer in the rheumatoid nodule. CONCLUSION: The presence of similar proinflammatory cytokines and cell adhesion molecules in the rheumatoid nodule and synovial membrane suggests that similar pathogenic processes result in the chronic inflammation and tissue destruction in these lesions.

Adult↗

PubMed2006

What is that nodule? A diagnostic approach to evaluating subcutaneous and cutaneous nodules.

The evaluation of patients with subcutaneous nodules remains a diagnostic challenge. The presence of nodules can be a clue to an underlying systemic disease; however, the varied presentations of nodules and numerous disease associations make the assessment of patients with nodules far from simple. With further investigation into the appearance, location, and symptoms associated with nodules, the clinical significance of these lesions can become clearer and aid in logical diagnostic evaluation. We have reviewed the causes of nodules with emphasis on those associated with rheumatic disease and provide guidelines for nodule evaluation to better characterize disease association and lead to directed diagnostic assessment.

Diagnosis, Differential↗

PubMed1983

Nodule-specific host proteins in effective and ineffective root nodules of Pisum sativum.

Nodule-specific root proteins - so called nodulins - were identified in root nodules of pea plants by an immunological assay. Nodulin patterns were examined at different stages of nodule development. About 30 nodulins were detectable during development. Some were preferentially synthesized before nitrogen fixation started, whereas the majority were synthesized concomitantly with leghaemoglobin. Some of the nodulins were located within the peribacteroid membrane. Ineffective Rhizobium strains (a natural nodfix and a pop fix) appeared to be useful in studying the expression of nodulin genes. Synthesis of some nodulins was repressed in ineffective root nodules, indicating that nodulins are essential for the establishment of nitrogen fixation. In both types of ineffective root nodules, leghaemoglobin synthesis was not completely repressed. Low amounts of leghaemoglobin were always detected in young ineffective root nodules whereas in old nodules no leghaemoglobin was present.

Journal Article↗

PubMed1990

The early nodulin transcript ENOD2 is located in the nodule parenchyma (inner cortex) of pea and soybean root nodules.

A pea cDNA clone homologous to the soybean early nodulin clone pGmENOD2 that most probably encodes a cell wall protein was isolated. The derived amino acid sequence of the pea ENOD2 protein shows that it contains the same repeating pentapeptides, ProProHisGluLys and ProProGluTyrGln, as the soybean ENOD2 protein. By in situ hybridization the expression of the ENOD2 gene was shown to occur only in the inner cortex of the indeterminate pea nodule. The transcription of the pea ENOD2 gene starts when the inner cortical cells develop from the nodule meristem. In the determinate soybean nodule the ENOD2 gene is expressed in the inner cortex as well as in cells surrounding the vascular bundle that connects the nodule with the root central cylinder. The term 'nodule inner cortex' is misleading, as there is no direct homology with the root inner cortex. Therefore, we propose to consider this tissue as nodule parenchyma. A possible role of ENOD2 in a major function of the nodule parenchyma, namely creating an oxygen barrier for the central tissue with the Rhizobium containing cells, is discussed.

Amino Acid Sequence↗

PubMed1993

Two classes of differentially regulated glutamine synthetase genes are expressed in the soybean nodule: a nodule-specific class and a constitutively expressed class.

We have characterized two sets of cDNA clones representing the glutamine synthetase (GS) mRNA in soybean nodules. Using the 3'-untranslated regions of a representative member of each set, as gene member(s) specific probes, we have shown that one set of the GS genes are expressed in a nodule-specific manner, while the other set is expressed in other tissues, besides the nodules. The nodule-specific GS genes are expressed in a developmentally regulated manner in the nodules, independent of the onset of nitrogen fixation. The other class of GS genes is expressed constitutively in all tissues tested, but its expression level is dramatically enhanced in nodules following onset of N2 fixation. The latter set of genes is also expressed in cotyledons of germinating seedlings in a developmentally regulated manner. Analysis of hybrid select translation products and genomic Southern blots suggests that multiple gene members in each class are expressed in the nodules.

Amino Acid Sequence↗

PubMed1996

NodZ of Bradyrhizobium extends the nodulation host range of Rhizobium by adding a fucosyl residue to nodulation signals.

The nodulation genes of rhizobia are involved in the production of the lipo-chitin oligosaccharides (LCO), which are signal molecules required for nodule formation. A mutation in nodZ of Bradyrhizobium japonicum results in the synthesis of nodulation signals lacking the wild-type 2-O-methylfucose residue at the reducting-terminal N-acetylglucosamine. This phenotype is correlated with a defective nodulation of siratro (Macroptilium atropurpureum). Here we show that transfer of nodZ to Rhizobium leguminosarum blovar (bv) viciae, which produces LCOs that are not modified at the reducing-terminal N-acetylglucosamine, results in production of LCOs with a fucosyl residue on C-6 of the reducing-terminal N-acetylglucosamine. This finding, together with in vitro enzymatic assays, indicates that the product of nodZ functions as a fucosyltransferase. The transconjugant R. leguminosarum strain producing fucosylated LCOs acquires the capacity to nodulate M. atropurpureum, Glycine soja, Vigna unguiculate and Leucaena leucocephala. Therefore, nodZ extends the narrow host range of R. leguminosarum bv. viciae to include various tropical legumes. However, microscopic analysis of nodules induced on siratro shows that these nodules do not contain bacteroids, showing that transfer of nodZ does not allow R. leguminosarum to engage in a nitrogen-fixing symbiosis with this plant.

Amino Acid Sequence↗

PubMed1991

Light Microscopy Study of Nodule Initiation in Pisum sativum L. cv Sparkle and in Its Low-Nodulating Mutant E2 (sym 5).

We compared nodule initiation in lateral roots of Pisum sativum (L.) cv Sparkle and in a low-nodulating mutant E2 (sym 5). In Sparkle, about 25% of the infections terminated in the epidermis, a similar number stopped in the cortex, and 50% resulted in the formation of a nodule meristem or an emerged nodule. The mutant E2 (sym 5) was infected as often as was the parent, and it formed a normal infection thread. In the mutant, cell divisions rarely occurred in advance of the infection thread, and few nodule primordia were produced. Growing the mutant at a low root temperature or adding Ag(+) to the substrate increased the number of cell divisions and nodule primordia. We conclude that, in the E2 line, the infection process is arrested in the cortex, at the stage of initial cell divisions before the establishment of a nodule primordium.

Journal Article↗

PubMed1992

Nodules Initiated by Rhizobium meliloti Exopolysaccharide Mutants Lack a Discrete, Persistent Nodule Meristem.

Infection of alfalfa with Rhizobium meliloti exo mutants deficient in exopolysaccharide results in abnormal root nodules that are devoid of bacteria and fail to fix nitrogen. Here we report further characterization of these abnormal nodules. Tightly curled root hairs or shepherd's crooks were found after inoculation with Rm 1021-derived exo mutants, but curling was delayed compared with wild-type Rm 1021. Infection threads were initiated in curled root hairs by mutants as well as by wild-type R. meliloti, but the exo mutant-induced threads aborted within the peripheral cells of the developing nodule. Also, nodules elicited by Rm 1021-derived exo mutants were more likely to develop on secondary roots than on the primary root. In contrast with wild-type R. meliloti-induced nodules, the exo mutant-induced nodules lacked a well defined apical meristem, presumably due to the abortion of the infection threads. The relationship of these findings to the physiology of nodule development is discussed.

Journal Article↗