Plasmid replicons of Rhizobium

2005 ◽  
Vol 33 (1) ◽  
pp. 157-158 ◽  
Author(s):  
L.C. Crossman
Keyword(s):  
Short Review ◽  
Nitrogen Fixing ◽  
Rhizobium Etli ◽  
Free Living ◽  
Leguminous Plants ◽  
Symbiotic Plasmid ◽  
Rhizobium Spp ◽  
Plasmid Replicons ◽  
Rhizobium Sp

Rhizobium spp. are found in soil. They are both free-living and found symbiotically associated with the nodules of leguminous plants. Traditionally, studies have focused on the association of these organisms with plants in nitrogen-fixing nodules, since this is regarded as the most important role of these bacteria in the environment. Rhizobium sp. are known to possess several replicons. Some, like the Rhizobium etli symbiotic plasmid p42d and the plasmid pNGR234b of Rhizobium NGR234, have been sequenced and characterized. The plasmids from these organisms are the focus of this short review.

scholarly journals Novel Reiterated Fnr-Type Proteins Control the Production of the Symbiotic Terminal Oxidase cbb3 in Rhizobium etli CFN42

2007 ◽  
Vol 20 (10) ◽  
pp. 1241-1249 ◽  
Author(s):  
Manuel J. Granados-Baeza ◽  
Nicolás Gómez-Hernández ◽  
Yolanda Mora ◽  
María J. Delgado ◽  
David Romero ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Oxygen Affinity ◽  
Structural Similarity ◽  
Transcriptional Regulators ◽  
Terminal Oxidase ◽  
Nitrogen Fixing ◽  
Rhizobium Etli ◽  
High Oxygen Affinity ◽  
Key Genes

Symbiotic nitrogen-fixing bacteria express a terminal oxidase with a high oxygen affinity, the cbb3-type oxidase encoded by the fixNOQP operon. Previously, we have shown that, in Rhizobium etli CFN42, the repeated fixNOQP operons (fixNOQPd and fixNOQPf) have a differential role in nitrogen fixation. Only the fixNOQPd operon is required for the establishment of an effective symbiosis; microaerobic induction of this operon is under the control of at least three transcriptional regulators, FixKf, FnrNd, and FnrNchr, belonging to the Crp/Fnr family. In this work, we describe two novel Crp/Fnr-type transcriptional regulators (StoRd and StoRf, symbiotic terminal oxidase regulators) that play differential roles in the control of key genes for nitrogen fixation. Mutations either in stoRd or stoRf enhance the microaerobic expression of both fixNOQP reiterations, increasing also the synthesis of the cbb3-type oxidase in nodules. Despite their structural similarity, a differential role of these genes was also revealed, since a mutation in stoRd but not in stoRf enhanced both the expression of fixKf and the nitrogen-fixing capacity of R. etli CFN42.

scholarly journals Characterization and ecological role of free-living nitrogen-fixing bacteria isolated from the rhizoplane of Melastoma malabathricum inhabiting acidic plain lands in Kalimantan

Tropics ◽  
2006 ◽  
Vol 15 (4) ◽  
pp. 365-369 ◽  
Author(s):  
Yasuyuki HASHIDOKO ◽  
Yukako GOTOU ◽  
Mitsuru OSAKI ◽  
Erry PURNOMO ◽  
Limin H. SUWIDO ◽  
...  
Keyword(s):  
Ecological Role ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Free Living ◽  
Melastoma Malabathricum

scholarly journals Differential Regulation of fixN-Reiterated Genes in Rhizobium etli by a Novel fixL—fixK Cascade

2000 ◽  
Vol 13 (12) ◽  
pp. 1283-1292 ◽  
Author(s):  
Lourdes Girard ◽  
Susana Brom ◽  
Araceli Dávalos ◽  
Oswaldo López ◽  
Mario Soberón ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Regulatory Element ◽  
Regulatory Gene ◽  
Regulatory System ◽  
Differential Regulation ◽  
Rhizobium Etli ◽  
Free Living ◽  
Symbiotic Plasmid ◽  
Independent Mechanism ◽  
Fusion Analysis

Among the complexities in the regulation of nitrogen fixation in the Rhizobiaceae are reiteration of regulatory components as well as variant roles for each component between species. For Rhizobium etli CFN42, we reported that the symbiotic plasmid (pCFN42d) contains a key regulatory gene (fixKd) and genes for a symbiotic cytochrome oxidase (fixNOQPd). Here we discuss the occurrence of reiteration of these genes (fixKf and fixNOQPf) and the finding of an unusual fixL homolog on a plasmid previously considered cryptic (pCFN42f). The structure of the deduced FixL polypeptide is suggestive of a fusion of the receiver and transmitter modules of a two-component regulatory system as described in R. leguminosarum bv. viciae VF39. Gene fusion analysis, coupled with mutation of each regulatory element, revealed that free-living expression of FixKf was dependent fully on FixL. In contrast, synthesis of FixKd was not detected under the conditions tested. The FixKf protein is needed for microaerobic expression of both fixN reiterations, whereas the FixKd protein appears to be dispensable. Interestingly, expression of the fixN reiterations exhibits a differential dependence for FixL, where transcription of fixNf was suppressed in the absence of FixL but expression of fixNd still showed significant levels. This suggests the existence of a FixL-independent mechanism for expression of the fixNd reiteration. Surprisingly, mutations in fixL, fixKd, or fixKf (either singly or in combination) did not alter symbiotic effectiveness. A mutation in fixNd (but not in fixNf) was, however, severely affected, indicating a differential role for these reiterations in nitrogen fixation.

scholarly journals Analysis of a Symbiosis-Specific Cytochrome P450 Homolog in Rhizobium sp. BR816

2001 ◽  
Vol 14 (7) ◽  
pp. 918-924 ◽  
Author(s):  
Ellen Luyten ◽  
Elfriede Swinnen ◽  
Katrien Vlassak ◽  
Christel Verreth ◽  
Bruno Dombrecht ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Amino Acid ◽  
Transcriptional Analysis ◽  
Free Living ◽  
Amino Acid Similarity ◽  
Reading Frame ◽  
P450 Gene ◽  
Symbiotic Plasmid ◽  
Rhizobium Sp ◽  
Free Living Conditions

Sequence analysis of the DNA region upstream of nodO in Rhizobium sp. BR816 revealed an open reading frame in which the deduced amino acid sequence shows homology with cytochrome P450. Because the BR816 P450 homolog shows 73% amino acid similarity with CYP127A1(Y4vG), which is identified on the symbiotic plasmid of Rhizobium sp. NGR234, it is named CYP127A2. Transcriptional analysis of CYP127A2 revealed high expression in bacteroids, whereas no or hardly any expression was observed under free-living conditions. Low-level, free-living expression, however was noticed when cells were grown microoxically at acid pH levels. A number of possible substrates that may induce P450 gene expression were analyzed, but only the addition of short-chain alcohols to cultures slightly increased CYP127A2 expression. High levels of CYP127A2 expression observed in bacteroids of a nifH mutant strain, which formed non-fixing nodules on bean, indicated that the genuine substrate for CYP127A2 is not a metabolite resulting from N2-fixation. Nevertheless, expression analysis pointed to a NifA- and σ54-dependent transcription.

Transformation of Azotobacter vinelandii strains unable to fix nitrogen with Rhizobium spp. DNA

1978 ◽  
Vol 24 (3) ◽  
pp. 209-214 ◽  
Author(s):  
William J. Page
Keyword(s):  
Transcriptional Control ◽  
Deoxyribonucleic Acid ◽  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Spontaneous Reversion ◽  
Mutant Strains ◽  
Rhizobium Spp ◽  
Rhizobium Sp

The phenotypes of Azotobacter vinelandii ATCC 12837 strains defective in nitrogen fixation (Nif−) were characterized by intrageneric transformation with known Nif− strains of A. vinelandii OP. These former mutant strains were used as recipients for intergeneric transformation by deoxyribonucleic acid (DNA) prepared from Rhizobium spp. to determine if the rhizobia would transform the Azotobacter Nif− phenotypes to Nif+. The frequency of Nif+ transformants using Rhizobium DNA was always less than the frequency using Azotobacter wild-type DNA but was greater than the spontaneous reversion frequency. The Azotobacter Nif+ recombinants also were stable. DNA from all of the Rhizobium spp. transformed to Nif+Azotobacter mutants defective in the nitrogenase component I (molybdoferredoxin); however, some recombinants had a lower nitrogenase activity and a delayed nitrogenase depression time. Mutants defective in the pleiotrophic transcriptional control of both nitrogenase components were transformed to Nif+ by the asymbiotic nitrogen fixing Rhizobium sp. 32H1 and 41A1, but not the symbiotic nitrogen-fixing species. The significance of these results and the possible future applications of this system are discussed.

scholarly journals Structural Elements Required for Replication and Incompatibility of the Rhizobium etli Symbiotic Plasmid

2000 ◽  
Vol 182 (11) ◽  
pp. 3117-3124 ◽  
Author(s):  
Miguel A. Ramírez-Romero ◽  
Nora Soberón ◽  
Angeles Pérez-Oseguera ◽  
Juan Téllez-Sosa ◽  
Miguel A. Cevallos
Keyword(s):  
Plasmid Copy Number ◽  
Intergenic Sequence ◽  
Structural Elements ◽  
Rhizobium Etli ◽  
Plasmid Copy ◽  
Plasmid Segregation ◽  
Symbiotic Plasmid ◽  
Conserved Genes ◽  
Dna Strand ◽  
Plasmid Replicons

ABSTRACT The symbiotic plasmid of Rhizobium etli CE3 belongs to the RepABC family of plasmid replicons. This family is characterized by the presence of three conserved genes, repA,repB, and repC, encoded by the same DNA strand. A long intergenic sequence (igs) between repBand repC is also conserved in all members of the plasmid family. In this paper we demonstrate that (i) the repABCgenes are organized in an operon; (ii) the RepC product is essential for replication; (iii) RepA and RepB products participate in plasmid segregation and in the regulation of plasmid copy number; (iv) there are two cis-acting incompatibility regions, one located in the igs (incα) and the other downstream ofrepC (incβ) (the former is essential for replication); and (v) RepA is a trans-acting incompatibility factor. We suggest that incα is acis-acting site required for plasmid partitioning and that the origin of replication lies within incβ.

scholarly journals Regulatory Role of Rhizobium etli CNPAF512 fnrN during Symbiosis

2004 ◽  
Vol 70 (3) ◽  
pp. 1287-1296 ◽  
Author(s):  
Martine Moris ◽  
Bruno Dombrecht ◽  
Chuanwu Xi ◽  
Jos Vanderleyden ◽  
Jan Michiels
Keyword(s):  
Sigma Factor ◽  
Rhizobium Etli ◽  
Wild Type ◽  
Free Living ◽  
Severe Reduction ◽  
Fixation Capacity ◽  
Additional Level ◽  
Microaerobic Conditions ◽  
Related Proteins

ABSTRACT The Rhizobium etli CNPAF512 fnrN gene was identified in the fixABCX rpoN 2 region. The corresponding protein contains the hallmark residues characteristic of proteins belonging to the class IB group of Fnr-related proteins. The expression of R. etli fnrN is highly induced under free-living microaerobic conditions and during symbiosis. This microaerobic and symbiotic induction of fnrN is not controlled by the sigma factor RpoN and the symbiotic regulator nifA or fixLJ, but it is due to positive autoregulation. Inoculation of Phaseolus vulgaris with an R. etli fnrN mutant strain resulted in a severe reduction in the bacteroid nitrogen fixation capacity compared to the wild-type capacity, confirming the importance of FnrN during symbiosis. The expression of the R. etli fixN, fixG, and arcA genes is strictly controlled by fnrN under free-living microaerobic conditions and in bacteroids during symbiosis with the host. However, there is an additional level of regulation of fixN and fixG under symbiotic conditions. A phylogenetic analysis of the available rhizobial FnrN and FixK proteins grouped the proteins in three different clusters.

scholarly journals A Comparative Transcriptome Analysis of Rhizobium etli Bacteroids: Specific Gene Expression During Symbiotic Nongrowth

2011 ◽  
Vol 24 (12) ◽  
pp. 1553-1561 ◽  
Author(s):  
Maarten Vercruysse ◽  
Maarten Fauvart ◽  
Serge Beullens ◽  
Kristien Braeken ◽  
Lore Cloots ◽  
...  
Keyword(s):  
Stationary Phase ◽  
Specific Gene ◽  
Nitrogen Fixing ◽  
Rhizobium Etli ◽  
Transcriptome Profile ◽  
Free Living ◽  
Specific Expression ◽  
Genome Wide ◽  
Physiological Adaptations ◽  
Upregulated Genes

Rhizobium etli occurs either in a nitrogen-fixing symbiosis with its host plant, Phaseolus vulgaris, or free-living in the soil. During both conditions, the bacterium has been suggested to reside primarily in a nongrowing state. Using genome-wide transcriptome profiles, we here examine the molecular basis of the physiological adaptations of rhizobia to nongrowth inside and outside of the host. Compared with exponentially growing cells, we found an extensive overlap of downregulated growth-associated genes during both symbiosis and stationary phase, confirming the essentially nongrowing state of nitrogen-fixing bacteroids in determinate nodules that are not terminally differentiated. In contrast, the overlap of upregulated genes was limited. Generally, actively growing cells have hitherto been used as reference to analyze symbiosis-specific expression. However, this prevents the distinction between differential expression arising specifically from adaptation to a symbiotic lifestyle and features associated with nongrowth in general. Using stationary phase as the reference condition, we report a distinct transcriptome profile for bacteroids, containing 203 induced and 354 repressed genes. Certain previously described symbiosis-specific characteristics, such as the downregulation of amino acid metabolism genes, were no longer observed, indicating that these features are more likely due to the nongrowing state of bacteroids rather than representing bacteroid-specific physiological adaptations.

Evidence countering the role of polygalacturonase in invasion of root hairs of leguminous plants by Rhizobium spp.

1968 ◽  
Vol 14 (6) ◽  
pp. 617-625 ◽  
Author(s):  
Thomas T. Lillich ◽  
Gerald H. Elkan
Keyword(s):  
Enzyme Activity ◽  
Glycine Max ◽  
Sole Carbon Source ◽  
Root Hairs ◽  
Rhizobium Japonicum ◽  
Leguminous Plants ◽  
Uninoculated Control ◽  
Rhizobium Spp ◽  
Polygalacturonase Activity

Polygalacturonase has been postulated as being involved in the invasion of the host legume by Rhizobium spp. The role of this enzyme in the invasion of Glycine max by Rhizobium japonicum was investigated. Enzyme activity of several Rhizobium spp. was assayed viscometrically and no constitutive polygalacturonase was found. The enzyme could not be induced by growth with either pectin or galactose as the sole carbon source. Extract and exudate from the roots of nodulating and nonnodulating strains of Glycine max that had been incubated with effective strains of R. japonicum failed to show any higher levels of polygalacturonase activity than did uninoculated control plants. Previously reported experiments were duplicated. Levels of polygalacturonase activity from the extract and exudate of white clover inoculated with R. trifolii Cl 226 were as reported in the literature. Contrary to published reports, however, no greater levels of enzyme activity were found from effective plant–bacteria associations than from either ineffective associations or uninoculated control plants. It was concluded from these experiments that polygalacturonase does not play a major role in the invasion of Glycine max by Rhizobium japonicum.

POPDC proteins and cardiac function

2019 ◽  
Vol 47 (5) ◽  
pp. 1393-1404 ◽  
Author(s):  
Thomas Brand
Keyword(s):  
Potential Role ◽  
Striated Muscle ◽  
Short Review ◽  
Effector Proteins ◽  
Muscle Disease ◽  
Disease Genes ◽  
Protein Protein Interaction ◽  
Interaction Partners ◽  
And Function

Abstract The Popeye domain-containing gene family encodes a novel class of cAMP effector proteins in striated muscle tissue. In this short review, we first introduce the protein family and discuss their structure and function with an emphasis on their role in cyclic AMP signalling. Another focus of this review is the recently discovered role of POPDC genes as striated muscle disease genes, which have been associated with cardiac arrhythmia and muscular dystrophy. The pathological phenotypes observed in patients will be compared with phenotypes present in null and knockin mutations in zebrafish and mouse. A number of protein–protein interaction partners have been discovered and the potential role of POPDC proteins to control the subcellular localization and function of these interacting proteins will be discussed. Finally, we outline several areas, where research is urgently needed.

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