Characterization of Symbiotic Genes and Regulation of Their Expression in Rhizobium Leguminosarum PRE

Rhizobium sp. strain TALI 145 nodulates Leucaena ieucocephaia and Phaseolus vulgaris, in addition to a wide range of tropical tree legumes. Six overlapping clones that complemented nodulation defects in leucaena and bean rhizobia were isolated and a 40-kb map of the symbiosis region was constructed. The common nod and nifA genes were situated approximately 17 kb apart, with the nodlJ genes in between. These clones enabled a derivative of TAL1145 carrying a partially deleted pSym to form ineffective nodules on both leucaena and bean, and a similar derivative of Rhizobium etli TAL182 to form ineffective nodules on bean. When two representative clones, pUHR9 and pUHR114, were each transferred to wild-type rhizobial strains, they allowed ineffective nodulation by Rhizobium meliloti on both leucaena and bean and by Rhizobium leguminosarum bv. viciae on bean. Transconjugants of R. leguminosarum bv. trifolii formed effective nodules on leucaena and ineffective nodules on bean. Tn5 mutagenesis of the symbiosis region resulted in a variety of nodulation and fixation phenotypes on leucaena and bean. On the basis of 16S rRNA sequences, TAL1145 was found to be distinct from both R. tropici and NGR234, the two groups of leucaena symbionts that were previously described.Key words: Rhizobium, Leucaena leucocephala, nodulation, nitrogen fixation.

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Identification and Characterization of a Bacteroid-Specific Dehydrogenase Complex in Rhizobium leguminosarum PRE

Applied and Environmental Microbiology ◽

10.1128/aem.54.12.3008-3013.1988 ◽

1988 ◽

Vol 54 (12) ◽

pp. 3008-3013 ◽

Cited By ~ 4

Author(s):

René M. Klein Lankhorst ◽

Panagiotis Katinakis ◽

Albert van Kammen ◽

Rommert C. van den Bos

Keyword(s):

Rhizobium Leguminosarum ◽

Identification And Characterization ◽

Dehydrogenase Complex

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Chemical characterization of effective and ineffective strains of Rhizobium leguminosarum bv. viciae.

Acta Biochimica Polonica ◽

10.18388/abp.1999_4125 ◽

1999 ◽

Vol 46 (4) ◽

pp. 1001-1009

Author(s):

S F Izmailov ◽

G Y Zhiznevskaya ◽

L V Kosenko ◽

G N Troitskaya ◽

N N Kudryavtseva ◽

...

Keyword(s):

Fatty Acids ◽

Rhizobium Leguminosarum ◽

Unsaturated Fatty Acids ◽

Effective Strain ◽

Chemical Characterization ◽

Unsaturation Index ◽

Fa Composition ◽

Sds Page ◽

Lower Molecular Mass

Chemical composition of lipopolysaccharide (LPS) isolated from an effective (97) and ineffective (87) strains of R. l. viciae has been determined. LPS preparations from the two strains contained: glucose, galactose, mannose, fucose, arabinose, heptose, glucosamine, galactosamine, quinovosamine, and 3-N-methyl-3,6-dideoxyhexose, as well as glucuronic, galacturonic and 3-deoxyoctulosonic acid. The following fatty acids were identified: 3-OH 14:0, 3-OH 15:0, 3-OH 16:0, 3-OH 18:0 and 27-OH 28:0. The ratio of 3-OH 14:0 to other major fatty acids in LPS 87 was higher that in LPS 97. SDS/PAGE profiles of LPS indicated that, in lipopolysaccharides, relative content of S form LPS I to that of lower molecular mass (LPS II) was much higher in the effective strain 97 than in 87. All types of polysaccharides exo-, capsular-, lipo, (EPS, CPS, LPS, respectively) examined possessed the ability to bind faba bean lectin. The degree of affinity of the host lectin to LPS 87 was half that to LPS 97. Fatty acids (FA) composition from bacteroids and peribacteroid membrane (PBM) was determined. Palmitic, stearic and hexadecenoic acids were common components found in both strains. There was a high content of unsaturated fatty acids in bacteroids as well as in PBM lipids. The unsaturation index in the PBM formed by strain 87 was lower than in the case of strain 97. Higher ratio of 16:0 to 18:1 fatty acids was characteristic for PMB of the ineffective strain.

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Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum.

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-02-21-0037-r ◽

2021 ◽

Author(s):

Isabel Webb ◽

Jiabao Xu ◽

Carmen Sanchez-Cañizares ◽

Ramakrishnan Karunakaran ◽

Vinoy Ramachandran ◽

...

Keyword(s):

Nitrogen Fixation ◽

Rhizobium Leguminosarum ◽

Redox Balance ◽

Rna Seq ◽

Wild Type ◽

Transcription Start Sites ◽

Sym Plasmid ◽

Microaerobic Conditions ◽

Type Infection

Symbiosis between Rhizobium leguminosarum and Pisum sativum requires tight control of redox balance in order to maintain respiration under the microaerobic conditions required for nitrogenase, whilst still producing the eight electrons and sixteen molecules of ATP needed for nitrogen fixation. FixABCX, electron transfer flavoproteins essential for nitrogen fixation, are encoded on the Sym plasmid (pRL10), immediately upstream of nifA, which encodes the general transcriptional regulator of nitrogen fixation. There is a symbiotically-regulated NifA-dependent promoter upstream of fixA (PnifA1), as well as an additional basal constitutive promoter driving background expression of nifA (PnifA2). These were confirmed by 5’-end mapping of transcription start sites using differential (d) RNA-seq. Complementation of polar fixAB and fixX mutants (Fix- strains) confirmed expression of nifA from PnifA1 in symbiosis. Electron microscopy combined with single-cell Raman microspectroscopy characterization of fixAB mutants revealed previously unknown heterogeneity in bacteroid morphology within a single nodule. Two morphotypes of mutant fixAB bacteroids were observed. One was larger than wild-type bacteroids and contained high levels of polyhydroxy-3-butyrate, a complex energy/reductant storage product. A second bacteroid phenotype was morphologically and compositionally different and resembled wild-type infection thread cells. From these two characteristic fixAB mutant bacteroid morphotypes, inferences can be drawn on the metabolism of wild-type nitrogen-fixing bacteroids.

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Binding Site Determinants for the LysR-Type Transcriptional Regulator PcaQ in the Legume Endosymbiont Sinorhizobium meliloti

Journal of Bacteriology ◽

10.1128/jb.01456-07 ◽

2007 ◽

Vol 190 (4) ◽

pp. 1237-1246 ◽

Cited By ~ 15

Author(s):

Allyson M. MacLean ◽

Michelle I. Anstey ◽

Turlough M. Finan

Keyword(s):

Binding Site ◽

Sinorhizobium Meliloti ◽

Rhizobium Leguminosarum ◽

Transcriptional Start Site ◽

Mesorhizobium Loti ◽

Equilibrium Dissociation ◽

Dyad Symmetry

ABSTRACT LysR-type transcriptional regulators represent one of the largest groups of prokaryotic regulators described to date. In the gram-negative legume endosymbiont Sinorhizobium meliloti, enzymes involved in the protocatechuate branch of the β-ketoadipate pathway are encoded within the pcaDCHGB operon, which is subject to regulation by the LysR-type protein PcaQ. In this work, purified PcaQ was shown to bind strongly (equilibrium dissociation constant, 0.54 nM) to a region at positions −78 to −45 upstream of the pcaD transcriptional start site. Within this region, we defined a PcaQ binding site with dyad symmetry that is required for regulation of pcaD expression in vivo and for binding of PcaQ in vitro. We also demonstrated that PcaQ participates in negative autoregulation by monitoring expression of pcaQ via a transcriptional fusion to lacZ. Although pcaQ homologues are present in many α-proteobacteria, this work describes the first reported purification of this regulator, as well as characterization of its binding site, which is conserved in Agrobacterium tumefaciens, Rhizobium leguminosarum, Rhizobium etli, and Mesorhizobium loti.

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Phaseolus vulgaris is nodulated in northern Spain by Rhizobium leguminosarum strains harboring two nodC alleles present in American Rhizobium etli strains: biogeographical and evolutionary implications

Canadian Journal of Microbiology ◽

10.1139/w10-048 ◽

2010 ◽

Vol 56 (8) ◽

pp. 657-666 ◽

Cited By ~ 41

Author(s):

Paula García-Fraile ◽

Daniel Mulas-García ◽

Alvaro Peix ◽

Raúl Rivas ◽

Fernando González-Andrés ◽

...

Keyword(s):

Phaseolus Vulgaris ◽

Rhizobium Leguminosarum ◽

Intergenic Spacer ◽

Climatic Conditions ◽

Phylogenetic Group ◽

Rhizobium Etli ◽

Symbiotic Genes ◽

Northern Spain ◽

Major Producer ◽

Core Genes

In this study a collection of rhizobial strains were isolated from effective nodules of Phaseolus vulgaris in a wide region of northern Spain, which is the major producer region of this legume in Spain. The analysis of their core genes, rrs, atpD, and recA, and the 16S–23S intergenic spacer showed that all isolates belong to the phylogenetic group of Rhizobium leguminosarum and some of them were identical to those of strains nodulating Vicia or Trifolium . None of the isolates was identified as Rhizobium etli ; however, all of them carry the nodC alleles α and γ harboured by American strains of this species. These alleles were also found in strains nodulating P. vulgaris in southern Spain identified as R. etli. These results suggest that R. etli was carried from America to Spain with common bean seeds, but that they could have found difficulties persisting in the soils of northern Spain, probably because of the climatic conditions. The symbiotic genes of this species could have been transferred, after the arrival of P. vulgaris, to strains of R. leguminosarum already present in northern Spanish soils.

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