SEARCH · PubMed Health

Results for “Plant Root Nodulation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources

PubMed2003

Rhizobium leguminosarum biovar viciae 1-aminocyclopropane-1-carboxylate deaminase promotes nodulation of pea plants.

Ethylene inhibits nodulation in various legumes. In order to investigate strategies employed by Rhizobium to regulate nodulation, the 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene was isolated and characterized from one of the ACC deaminase-producing rhizobia, Rhizobium leguminosarum bv. viciae 128C53K. ACC deaminase degrades ACC, the immediate precursor of ethylene in higher plants. Through the action of this enzyme, ACC deaminase-containing bacteria can reduce ethylene biosynthesis in plants. Insertion mutants with mutations in the rhizobial ACC deaminase gene (acdS) and its regulatory gene, a leucine-responsive regulatory protein-like gene (lrpL), were constructed and tested to determine their abilities to nodulate Pisum sativum L. cv. Sparkle (pea). Both mutants, neither of which synthesized ACC deaminase, showed decreased nodulation efficiency compared to that of the parental strain. Our results suggest that ACC deaminase in R. leguminosarum bv. viciae 128C53K enhances the nodulation of P. sativum L. cv. Sparkle, likely by modulating ethylene levels in the plant roots during the early stages of nodule development. ACC deaminase might be the second described strategy utilized by Rhizobium to promote nodulation by adjusting ethylene levels in legumes.

Carbon-Carbon Lyases↗

PubMed1995

gsa1 is a universal tetrapyrrole synthesis gene in soybean and is regulated by a GAGA element.

Expression of plant tetrapyrroles is high in photosynthetic tissues and in legume root nodules in the form of chlorophyll and heme, respectively. The universal tetrapyrrole precursor delta-aminolevulinic acid (ALA) is synthesized from glutamate 1-semialdehyde (GSA) by GSA aminotransferase in plants, which is encoded by gsa. Immunoblot analysis showed that GSA aminotransferase was expressed in soybean leaves and nodules, but not in roots, and that protein correlated with enzyme activity. These observations indicate that GSA aminotransferase expression is controlled in tetrapyrrole formation and argue against significant activity of an enzyme other than the well described aminotransferase for GSA-dependent ALA formation. gas mRNA and protein were induced in soybean nodules, and their activation was temporally intermediate between those of the respective early and late genes endo2 and lb. A GSA aminotransferase gene, designated gsa1, was isolated and appears to be one of two gsa genes in the soybean genome. gsa1 mRNA accumulated to high levels in leaves and nodules, but not in uninfected roots as discerned with a gsa1-specific probe. Message levels were higher in leaves from etiolated plantlets than in mature plants, and expression in the former was slightly elevated by light. The expression pattern of gsa1 mRNA was qualitatively similar to that of total gsa. The data strongly suggest that gsa1 is a universal tetrapyrrole synthesis gene and that a gsa gene specific for a tissue, tetrapyrrole, or light condition is unlikely. The gsa1 promoter contained a genetic element found in numerous Drosophila melanogaster genes; the so-called GAGA element displayed single-stranded character in vitro and formed a complex with nuclear factors from nodules and leaves but not from roots. From these observations we infer that the GAGA element is involved in the transcriptional control of gsa1.

Animals↗

PubMed1995

Symbiotic induction of a MADS-box gene during development of alfalfa root nodules.

In response to infection by Rhizobium, highly differentiated organs called nodules form on legume roots. Within these organs, the symbiotic association between the host plant and bacteria is established. A putative plant transcription factor, NMH7, has been identified in alfalfa root nodules. nmh7 contains a MADS-box DNA-binding region and shows homology to flower homeotic genes. This gene is a member of a multigene family in alfalfa and was identified on the basis of nucleic acid homology to plant regulatory protein genes (MADS-box-containing genes) from Antirrhinum and Arabidopsis. RNA analysis and in situ hybridization showed that expression of this class of regulatory genes is limited to the infected cells of alfalfa root nodules and is likely to be involved in the signal transduction pathway initiated by the bacterial symbiont, Rhizobium meliloti. The expression of nmh7 in a root-derived organ is unusual for this class of regulatory genes.

Amino Acid Sequence↗

PubMed2006

Metabolic changes of rhizobia in legume nodules.

Bacteria have evolved a wide variety of metabolic strategies to cope with varied environments. Some are specialists and only able to survive in restricted environments; others are generalists and able to cope with diverse environmental conditions. Rhizobia (e.g. Rhizobium, Sinorhizobium, Bradyrhizobium, Mesorhizobium and Azorhizobium species) can survive and compete for nutrients in soil and the plant rhizosphere but can also form a beneficial symbiosis with legumes in a highly specialized plant cell environment. Inside the legume-root nodule, the bacteria (bacteroids) reduce dinitrogen to ammonium, which is secreted to the plant in exchange for a carbon and energy source. A new and challenging aspect of nodule physiology is that nitrogen fixation requires the cycling of amino acids between the bacteroid and plant. This review aims to summarize the metabolic plasticity of rhizobia and the importance of amino acid cycling.

Amino Acids↗

PubMed1992

Characterization of delta-Aminolevulinic Acid Formation in Soybean Root Nodules.

Formation of the heme precursor delta-aminolevulinic acid (ALA) was studied in soybean root nodules elicited by Bradyrhizobium japonicum. Glutamate-dependent ALA formation activity by soybean (Glycine max) in nodules was maximal at pH 6.5 to 7.0 and at 55 to 60 degrees C. A low level of the plant activity was detected in uninfected roots and was 50-fold greater in nodules from 17-day-old plants; this apparent stimulation correlated with increases in both plant and bacterial hemes in nodules compared with the respective asymbiotic cells. The glutamate-dependent ALA formation activity was greatest in nodules from 17-day-old plants and decreased by about one-half in those from 38-day-old plants. Unlike the eukaryotic ALA formation activity, B. japonicum ALA synthase activity was not significantly different in nodules than in cultured cells, and the symbiotic activity was independent of nodule age. The lack of symbiotic induction of B. japonicum ALA synthase indicates either that ALA formation is not rate-limiting, or that ALA synthase is not the only source of ALA for bacterial heme synthesis in nodules. Plant cytosol from nodules catalyzed the formation of radiolabeled ALA from U-[(14)C]glutamate and 3,4-[(3)H]glutamate but not from 1-[(14)C]glutamate, and thus, operation of the C(5) pathway could not be confirmed.

Journal Article↗

PubMed1996

Presence of nitric oxide synthase activity in roots and nodules of Lupinus albus.

NO is a widespread messenger molecule in physiology. We were interested in investigating whether an NO-generating system could be present in plants. NO and L-[14C]citrulline were synthesized by roots and nodules of Lupinus albus in an L-arginine-dependent manner. L-[14C]Citrulline production was inhibited by N(G)-monomethyl-L-arginine, a nitric oxide synthase antagonist, in a competitive way. NADPH-diaphorase activity was localized in the vascular bundles in root and nodules, and also in the nodule infected zone. This staining was significantly reduced in the presence of N(G)-monomethyl-L-arginine. These results indicate the presence of a putative nitric oxide synthase in plants.

Arginine↗

PubMed1998

Lotus corniculatus nodulation specificity is changed by the presence of a soybean lectin gene

Plant lectins have been implicated as playing an important role in mediating recognition and specificity in the Rhizobium-legume nitrogen-fixing symbiosis. To test this hypothesis, we introduced the soybean lectin gene Le1 either behind its own promoter or behind the cauliflower mosaic virus 35S promoter into Lotus corniculatus, which is nodulated by R. loti. We found that nodulelike outgrowths developed on transgenic L. corniculatus plant roots in response to Bradyrhizobium japonicum, which nodulates soybean and not Lotus spp. Soybean lectin was properly targeted to L. corniculatus root hairs, and although infection threads formed, they aborted in epidermal or hypodermal cells. Mutation of the lectin sugar binding site abolished infection thread formation and nodulation. Incubation of bradyrhizobia in the nodulation (nod) gene-inducing flavonoid genistein increased the number of nodulelike outgrowths on transgenic L. corniculatus roots. Studies of bacterial mutants, however, suggest that a component of the exopolysaccharide surface of B. japonicum, rather than Nod factor, is required for extension of host range to the transgenic L. corniculatus plants.

Journal Article↗

PubMed1996

Bacillus polymyxa stimulates increased Rhizobium etli populations and nodulation when co-resident in the rhizosphere of Phaseolus vulgaris.

Microbial competition for carbon sources is a primary determinant of rhizosphere ecology. We employed the PCR to examine the population fluctuations of a symbiotic nitrogen-fixing bacterium (Rhizobium etli) during the first 11 days following inoculation of Phaseolus vulgaris seedlings grown in the presence or absence of a common asymbiotic rhizosphere resident (Bacillus polymyxa). When B. polymyxa was applied as a co-inoculant, increases in both early rhizobial root populations and final root population densities were observed as compared to single inoculation with R. etli. Modifications to host plant growth (including increased lateral root formation and nodules number) were found concomitant with elevations in R. etli populations on plants co-inoculated with both bacterial genera. In contrast to the in planta results, population enhancements were not observed when R. etli and B. polymyxa were co-cultured in vitro using minimal media in the absence of the seedling. Addition of seed exudate to the growth media also failed to stimulate the population increases observed during co-release in planta. These results suggest that B. polymyxa acts indirectly (i.e., via the plant host) to increase R. etli populations. Our observed synergism among co-resident bacteria supports the hypothesis that microbial communities which colonize the spermosphere may play a significant role in plant development and rhizosphere ecology.

Bacillus↗

PubMed1986

Isozymes of Glutamine Synthetase in Phaseolus vulgaris L. and Phaseolus lunatus L. Root Nodules.

The glutamine synthetase (GS) isozymes in the plant fraction of nodule extracts from 62 cultivars of Phaseolus vulgaris L. and one cultivar of Phaseolus lunatus L. were analyzed by polyacrylamide gel electrophoresis. All P. vulgaris nodule extracts displayed two GS activity bands: a nodule-specific band (GS(n1)) and a band (GS(n2)) similar to the single band (GS(r)) present in root extracts. In nodule extracts of P. lunatus, the GS(n1) band was detected, but the GS(n2) band was barely detectable. In contrast to P. vulgaris, the GS(n2) band and the GS(r) band of P. lunatus appeared to be different. The electrophoretic mobility of the GS(n1) band in P. vulgaris was governed by both the plant cultivar and the development stage of the nodule. In nodule extracts of P. vulgaris and P. lunatus, the zone of GS(n1) activity coincided with six to nine distinct protein bands as revealed after treatment of gels, which had previously been stained for GS activity, with Coomassie blue. All these protein bands were shown to consist of polypeptides of identical molecular weight (approximately 47,000 daltons) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Our results indicate that P. vulgaris continuously generates isozymes of GS(n1) of increasing electrophoretic mobility during the course of nodule development.

Journal Article↗

PubMed1996

Amplification of 16S rRNA genes from Frankia strains in root nodules of Ceanothus griseus, Coriaria arborea, Coriaria plumosa, Discaria toumatou, and Purshia tridentata.

To study the global diversity of plant-symbiotic nitrogen-fixing Frankia strains, a rapid method was used to isolate DNA from these actinomycetes in root nodules. The procedure used involved dissecting the symbiont from nodule lobes; ascorbic acid was used to maintain plant phenolic compounds in the reduced state. Genes for the small-subunit rRNA (16S ribosomal DNA) were amplified by the PCR, and the amplicons were cycle sequenced. Less than 1 mg (fresh weight) of nodule tissue and fewer than 10 vesicle clusters could serve as the starting material for template preparation. Partial sequences were obtained from symbionts residing in nodules from Ceanothus griseus, Coriaria arborea, Coriaria plumosa, Discaria toumatou, and Purshia tridentata. The sequences obtained from Ceonothus griseus and P. tridentata nodules were identical to the sequence previously reported for the endophyte of Dryas drummondii. The sequences from Frankia strains in Coriaria arborea and Coriaria plumosa nodules were identical to one another and indicate a separate lineage for these strains. The Frankia strains in Discaria toumatou nodules yielded a unique sequence that places them in a lineage close to bacteria that infect members of the Elaeagnaceae.

Actinomycetales↗

PubMed2005

Probing the Sinorhizobium meliloti-alfalfa symbiosis using temperature-sensitive and impaired-function citrate synthase mutants.

To study the role of the decarboxylating leg of the bacterial TCA cycle in symbiotic nitrogen fixation, we used DNA shuffling and localized random polymerase chain reaction mutagenesis to construct a series of temperature-sensitive and impaired-function mutants in the Sinorhizobium meliloti Rm104A14 citrate synthase (gltA) gene. Reducing citrate synthase (CS) activity by mutation led to a corresponding decrease in the free-living growth rate; however, alfalfa plants formed fully effective nodules when infected with mutants having CS activities as low as 7% of the wild-type strain. Mutants with approximately 3% of normal CS activity formed nodules with lower nitrogenase activity and a mutant with less than 0.5% of normal CS activity formed Fix- nodules. Two temperature-sensitive (ts) mutants grew at a permissive temperature (25 degrees C) with 3% of wild-type CS activities but were unable to grow on minimal medium at 30 degrees C. Alfalfa plants that were inoculated with the ts mutants and grown with a root temperature of 20 degrees C formed functional nodules with nitrogenase activities approximately 20% of the wild type. When the roots of plants infected with the ts mutants were transferred to 30 degrees C, the nodules lost the ability to fix nitrogen over several days. Microscopic examination of these nodules revealed the loss of bacteroids and senescence, indicating that CS activity was essential for nodule maintenance.

Citrate (si)-Synthase↗

PubMed1997

Cloning of a WD-repeat-containing gene from alfalfa (Medicago sativa): a role in hormone-mediated cell division?

Rhizobium meliloti can interact symbiotically with Medicago plants thereby inducing the formation of root nodules. Screening of a young nodule cDNA library led to the isolation of a cDNA from Medicago sativa, Msgbl, that comprises a new member of the RACK1 (Receptor of Activated C Kinase) subfamily of WD-repeat proteins. This subfamily shows homology to the beta-subunit of heterotrimeric G proteins. Besides RACK1, this subfamily contains several plant genes including the well characterized auxin-inducible ArcA of tobacco. The Msgbl gene is strongly expressed in young embryos and in leaves, and is induced upon cytokinin treatment of roots. Whereas northern analysis failed to reveal differences in expression between total RNA from roots and nodules, in situ hybridization demonstrated that the transcript was most abundant in dividing cells of nodule primordia and in the nodule meristem. Msgbl may be related to the signal transduction acting in response to hormone-mediated cell division.

Amino Acid Sequence↗

PubMedDate not supplied

Mineral nutrition of plants: a short history of plant physiology.

The development of the knowledge on the mineral nutrition of plants begins between the 17th and 18th centuries when some European naturalists gave the first experimental evidences of what had been empirically known for about two millennia. The works of Hales and Ingenhousz were of absolute importance in relation to the transport of water and solutes, and assimilation of "fixed air" (carbon dioxide), respectively. The early chemistry introduced by Lavoisier benefited the first physiologists Senebier and De Saussure to reject the "theory of humus", which imposed the soil as the unique source of carbon. During the first half of the 19th century, Sprengel and Liebig investigated on the problems related to some indispensable mineral salts, while Boussingault and Ville attempted to prove the nitrogen fixation from air without giving any convincing evidence. Liebig was the pioneer of the agricultural chemistry: he epitomised the knowledge of that period by imposing the so-called "law of the minima", already acknowledged by Sprengel, and patronised the use of mineral fertilisers in Europe by devising several formulas of mineral manure. He, however, did not recognise the needs of external supplies of nitrogen salts for the crops, in open dispute with the English school of Lawes and Gilbert, who were instead convinced assertors of such needs. At the end of the 19th century Hellriegel showed that leguminous plants presenting peculiar nodules on their roots could really fix the gaseous nitrogen. From these nodules Beijerinck and Prazmowski isolated for the first time some bacteria which were recognised as the real agents fixing nitrogen. This discovery was of fundamental importance for plant nutrition, only second to the discovery of photosynthesis. Another basic contribution came from early research of Sachs on plants grown on aqueous solutions: these techniques allowed to impose the concept of "essential elements", which was fixed as a principle by Arnon and Stout in 1939. This principle benefited further research concerning the effects of states of deficiency on plant growth and development through investigation on the anatomical, histologic and biochemical nutritional disorders of plants.

Biology↗

PubMed2005

Attractive properties of an isoflavonoid found in white clover root nodules on the clover root weevil.

The clover root weevil, Sitona lepidus, frequently feeds on N2 fixing rhizobial root nodules of white clover (Trifolium repens), which may contain isoflavonoids with defensive and plant regulatory properties. This study investigated the isoflavonoids present in N2 fixing (active) root nodules, root nodules that were not fixing N2 (inactive), and roots without nodules, and tested the behavioral responses of neonatal S. lepidus larvae to aglycones of the identified compounds. Formononetin concentrations were higher in the active nodules compared with inactive nodules and roots alone. Moreover, there was a statistically significant attraction to formononetin by S. lepidus in arena experiments, whereas the other isoflavonoids were unattractive. It is suggested that S. lepidus may have become tolerant to the toxic effects of formononetin with repeated exposure, and that it may play a role in root nodule location. Such coevolutionary relationships are widely reported for aboveground insects and plants, but the present study suggests they may also occur belowground.

Animals↗

PubMed2005

Glutathione and homoglutathione play a critical role in the nodulation process of Medicago truncatula.

Legumes form a symbiotic interaction with bacteria of the Rhizobiaceae family to produce nitrogen-fixing root nodules under nitrogen-limiting conditions. This process involves the recognition of the bacterial Nod factors by the plant which mediates the entry of the bacteria into the root and nodule organogenesis. We have examined the importance of the low molecular weight thiols, glutathione (GSH) and homoglutathione (hGSH), during the nodulation process in the model legume Medicago truncatula. Using both buthionine sulfoximine, a specific inhibitor of GSH and hGSH synthesis, and transgenic roots expressing GSH synthetase and hGSH synthetase in an antisense orientation, we showed that deficiency in GSH and hGSH synthesis inhibited the formation of the root nodules. This inhibition was not correlated to a modification in the number of infection events or to a change in the expression of the Rhizobium sp.-induced peroxidase rip1, indicating that the low level of GSH or hGSH did not alter the first steps of the infection process. In contrast, a strong diminution in the number of nascent nodules and in the expression of the early nodulin genes, Mtenod12 and Mtenod40, were observed in GSH and hGSH-depleted plants. In conclusion, GSH and hGSH appear to be essential for proper development of the root nodules during the symbiotic interaction.

Buthionine Sulfoximine↗

PubMed1977

Root and nodule respiration in relation to acetylene reduction in intact nodulated peas.

Inoculated pea plants (Pisum sativum L.) were grown with N-free nutrients in a controlled environment room and rates of respiratory CO(2) evolution and C(2)H(2) reduction by the intact nodulated roots were determined. Experiments followed changes related to diurnal cycles, light and dark treatments, partial defoliation, aging of plants and NH(4)NO(3) addition. In all experiments, changes in C(2)H(2) reduction were associated with parallel changes in the respiration rate, although in all but the defoliation experiment there was a basal level of respiration which was independent of the rate of C(2)H(2) reduction. In conditions which affected growth or plant size as well as C(2)H(2) reduction, respiration changed by an average of 0.42 mg CO(2) (mumol C(2)H(2) reduced)(-1). However, some treatments decreased C(2)H(2) reduction without greatly changing the growth and in these conditions respiration was decreased by an average of 0.27 mg CO(2) (mumol C(2)H(2) reduced)(-1). While this value may also include some respiration associated with other processes, it is proposed that it more closely estimates respiration directly associated with energy utilization for acetylene reduction; whereas the higher value includes respiration related to maintenance and growth processes as well.

Journal Article↗

PubMed2004

The promoter of the Vicia faba L. leghemoglobin gene VfLb29 is specifically activated in the infected cells of root nodules and in the arbuscule-containing cells of mycorrhizal roots from different legume and nonlegume plants.

The VfLb29 leghemoglobin gene promoter was polymerase chain reaction-amplified from a Vicia faba genomic library and was fused to the gusAint coding region. Expression of the chimeric gene was analyzed in transgenic hairy roots of the legumes V. faba, V. hirsuta, and Medicago truncatula as well as in transgenic Nicotiana tabacum plants. The VfLb29 promoter was found to be specifically active not only in the infected cells of the nitrogen-fixing zone of root nodules but also in arbuscule-containing cells of transgenic V. faba and M. truncatula roots colonized by the endomycorrhizal fungus Glomus intraradices. In addition to these two legumes, specific expression in arbuscule-containing cells was also observed in the nonlegume N. tabacum. All studies were done in comparison to the V. faba leghemoglobin gene promoter VfLb3 that as VfLb29 was expressed in the infected cells of root nodules but showed no activity in endomycorrhiza. An activation of the VfLb29 promoter due to hypoxia in metabolically active tissues was excluded. The conserved activation in arbuscule-containing cells of legumes and the nonlegume N. tabacum suggests a conserved trigger for this promoter in legume and nonlegume endomycorrhiza symbioses.

Anaerobiosis↗

PubMed1991

Alfalfa Controls Nodulation during the Onset of Rhizobium-induced Cortical Cell Division.

The formation of first nodules inhibits subsequent nodulation in younger regions of alfalfa (Medicago sativa L.) roots by a feedback regulatory mechanism that controls nodule number systemically (G Caetano-Anollés, WD Bauer [1988] Planta 175: 546-557). Following inoculation with wild-type Rhizobium meliloti, almost all infections associated with cortical cell division developed into mature nodules. While the distribution of Rhizobium- induced cell divisions closely paralleled the distribution of first emergent nodules, only 9 to 15% of total cell division foci failed to become functional nodules. Nodule formation was restricted to the primary root when plants were inoculated before lateral root emergence. Excision of these primary root nodules allowed nodules to reappear in lateral roots clustered around the location of the root tip at the time of nodule removal. Apparently, this region regained susceptibility to infection within the first hours after excision of primary nodules and suppression of nodulation was restored a day later probably due to the development of new infection foci. Our results suggest that alfalfa controls nodulation during the onset of cell division in the root cortex and not during infection development as in soybean.

Journal Article↗