scholarly journals An Iron Uptake Operon Required for Proper Nodule Development in the Bradyrhizobium japonicum-Soybean Symbiosis

2005 ◽  
Vol 18 (9) ◽  
pp. 950-959 ◽  
Author(s):  
Heather P. Benson ◽  
Eric Boncompagni ◽  
Mary Lou Guerinot
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Iron Acquisition ◽  
Outer Membrane Proteins ◽  
Protein Characterization ◽  
Nodule Development ◽  
In Planta ◽  
Siderophore Receptors ◽  
Infected Cells ◽  
Inner Membrane Protein ◽  
Mutant Forms

Rhizobia live in the soil or enter into a nitrogen-fixing symbiosis with a suitable host plant. Each environment presents different challenges with respect to iron acquisition. The soybean symbiont Bradyrhizobium japonicum 61A152 can utilize a variety of siderophores (Fe[III]-specific ligands). Purification of iron-regulated outer membrane proteins had previously allowed the cloning of a gene, fegA, from B. ja-ponicum 61A152, whose predicted protein shares significant amino acid similarity with known TonB-dependent siderophore receptors. Here, we show that fegA is in an operon with a gene, fegB, that is predicted to encode an inner membrane protein. Characterization of fegAB and fegB mutants shows that both fegA and fegB are required for utilization of the siderophore ferrichrome. Whereas the fegB mutant forms a normal symbiosis, the fegAB mutant has a dramatic phenotype in planta. Six weeks after inoculation with a fegAB strain, soybean nodules do not contain leghemoglobin and do not fix nitrogen. Infected cells contain few symbiosomes and are filled with vesicles. As ferrichrome is a fungal siderophore not likely to be available in nodules, the symbiotic defect suggests that the fegAB operon is serving a different function in planta, possibly one involved in signaling between the two partners.

A D-pinitol transporter, LjPLT11, regulates plant growth and nodule development in Lotus japonicus

2021 ◽  
Author(s):  
Lu Tian ◽  
Leru Liu ◽  
Shaoming Xu ◽  
Rufang Deng ◽  
Pingzhi Wu ◽  
...  
Keyword(s):  
Plant Growth ◽  
Nitrogenase Activity ◽  
Lotus Japonicus ◽  
Nodule Development ◽  
Xenopus Laevis Oocytes ◽  
Oxygen Species ◽  
In Planta ◽  
Osmotic Balance ◽  
Infected Cells ◽  
Functional Analyses

Abstract Polyol transporters (PLTs) have been functionally characterized in yeast and Xenopus laevis oocytes as H +-symporters with broad substrate specificity, but little is known about their physiological roles in planta. To extend this knowledge we investigated roles of LjPLT11 in Lotus japonicus-Mesorhizobium symbiosis. Functional analyses of the LjPLT11 in yeast characterized this protein as an energy-independent transporter of xylitol, two O-methyl inositols, xylose and galactose. We also showed that LjPLT11 is located on peribacteroid membranes (PBMs) and functions as a facilitative transporter of D-pinitol within infected cells of L. japonicus nodules. Knockdown of LjPLT11 (LjPLT11i) in L. japonicus accelerated plant growth under nitrogen-sufficiency, but resulted in abnormal bacteroids with corresponding reductions in nitrogenase activity in nodules and plant growth in the nitrogen-fixing symbiosis. LjPLT11i nodules had higher osmotic pressure in cytosol and fewer in bacteroids than wildtype nodules both three and four weeks after inoculation of M. loti. Levels and distributions of reactive oxygen species were also perturbed in infected cells of four-week-old nodules in LjPLT11i plants. The results indicate that LjPLT11 plays a key role in adjustment of levels of its substrate pinitol, and thus maintenance of osmotic balance in infected cells and PBM stability during nodule development.

scholarly journals Genome-Wide Transcript Analysis of Bradyrhizobium japonicum Bacteroids in Soybean Root Nodules

2007 ◽  
Vol 20 (11) ◽  
pp. 1353-1363 ◽  
Author(s):  
Gabriella Pessi ◽  
Christian H. Ahrens ◽  
Hubert Rehrauer ◽  
Andrea Lindemann ◽  
Felix Hauser ◽  
...  
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Experimental Approach ◽  
Root Nodules ◽  
Nodule Development ◽  
Dependent Manner ◽  
Wild Type ◽  
In Planta ◽  
Soybean Root ◽  
Genome Wide ◽  
Transcript Profiles

The transcriptome of endosymbiotic Bradyrhizobium japonicum bacteroids was assessed, using RNA extracted from determinate soybean root nodules. Results were compared with the transcript profiles of B. japonicum cells grown in either aerobic or microaerobic culture. Microoxia is a known trigger for the induction of symbiotically relevant genes. In fact, one third of the genes induced in bacteroids at day 21 after inoculation are congruent with those up-regulated in culture by a decreased oxygen concentration. The other induced genes, however, may be regulated by cues other than oxygen limitation. Both groups of genes provide a rich source for the possible discovery of novel functions related to symbiosis. Samples taken at different timepoints in nodule development have led to the distinction of genes expressed early and late in bacteroids. The experimental approach applied here is also useful for B. japonicum mutant analyses. As an example, we compared the transcriptome of wild-type bacteroids with that of bacteroids formed by a mutant defective in the RNA polymerase transcription factor σ54. This led to a collection of hitherto unrecognized B. japonicum genes potentially transcribed in planta in a σ54-dependent manner.

Strain distribution and in planta production of an extracellular polysaccharide depolymerase from Bradyrhizobium japonicum

1992 ◽  
Vol 38 (8) ◽  
pp. 857-861 ◽  
Author(s):  
Michael F. Dunn ◽  
Arthur L. Karr
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Root Nodules ◽  
Extracellular Polysaccharide ◽  
Extracellular Polysaccharides ◽  
Neutral Sugar ◽  
In Planta ◽  
In Vitro Production ◽  
Polysaccharide Composition ◽  
Vitro Production

Thirty-four strains of Bradyrhizobium japonicum were screened for the in vitro production of an extracellular polysaccharide depolymerase active against the B. japonicum acidic extracellular polysaccharide that contains mannose, glucose, galactose, and 4-O-methylgalactose as neutral sugar components. Over 90% of tested strains producing this type of extracellular polysaccharide also produced the extracellular polysaccharide depolymerase, whereas strains producing a compositionally different extracellular polysaccharide did not. In addition, representatives of species related to B. japonicum by extracellular polysaccharide composition or host range were also phenotypically depolymerase negative. Depolymerase was also present in soybean root nodules formed by B. japonicum strain 2143. In contrast to the cell-associated depolymerase activity found in free-living cells of this strain, most of the depolymerase activity present in nodules is free of the bacteroids. The widespread occurrence of the depolymerase among B. japonicum strains and the spatiotemporal distribution of its activity in planta are consistent with the enzyme playing a role in the removal of surface extracellular polysaccharide from the microorganism during the infection of nodulation process. Key words: Bradyrhizobium japonicum, soybean, extracellular polysaccharides, extracellular polysaccharide depolymerase, bacteroids.

Contact-dependent acquisition of transferrin-bound iron by two strains of Haemophilus parasuis

1995 ◽  
Vol 41 (1) ◽  
pp. 70-74 ◽  
Author(s):  
N. Charland ◽  
C. G. D'silva ◽  
R. A. Dumont ◽  
D. F. Niven
Keyword(s):  
Type Strain ◽  
Iron Acquisition ◽  
Outer Membrane Proteins ◽  
Transferrin Receptors ◽  
Haemophilus Parasuis ◽  
Isolation And Identification ◽  
Isolation Technique ◽  
Affinity Isolation ◽  
Sds Page ◽  
Bovine Transferrin

Two strains of Haemophilus parasuis, namely, the type strain (ATCC 19417) and strain E751, were investigated with respect to iron acquisition. Both strains produced iron-repressible outer membrane proteins and could acquire iron from porcine transferrin but not from porcine lactoferrin. Neither strain used bovine transferrin, and human transferrin was used to only a very limited extent, if at all. In all cases, iron acquisition from transferrin required direct contact between the organisms and the protein. An affinity isolation technique based on biotinylated porcine transferrin plus streptavidin-agarose, followed by SDS-PAGE, allowed the isolation and identification of two potential porcine transferrin binding polypeptides (94 and 60 kDa) from total membranes derived from the type strain grown under iron-restricted conditions but only one (96 kDa) from strain E751. Each of these polypeptides was iron repressible and was not isolated when biotinylated human or bovine transferrin was used instead of biotinylated porcine transferrin. It is concluded that both strains acquire transferrin-bound iron by means of siderophore-independent mechanisms and that the isolated polypeptides represent porcine transferrin receptor components.Key words: Haemophilus parasuis, iron, transferrin, receptors.

scholarly journals Evolution of mitochondrial protein import – lessons from trypanosomes

2020 ◽  
Vol 401 (6-7) ◽  
pp. 663-676 ◽  
Author(s):  
André Schneider
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Protein Import ◽  
Outer Membrane Proteins ◽  
Mitochondrial Protein ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
System A ◽  
Import Receptors ◽  
Inner Membrane Protein

AbstractThe evolution of mitochondrial protein import and the systems that mediate it marks the boundary between the endosymbiotic ancestor of mitochondria and a true organelle that is under the control of the nucleus. Protein import has been studied in great detail in Saccharomyces cerevisiae. More recently, it has also been extensively investigated in the parasitic protozoan Trypanosoma brucei, making it arguably the second best studied system. A comparative analysis of the protein import complexes of yeast and trypanosomes is provided. Together with data from other systems, this allows to reconstruct the ancestral features of import complexes that were present in the last eukaryotic common ancestor (LECA) and to identify which subunits were added later in evolution. How these data can be translated into plausible scenarios is discussed, providing insights into the evolution of (i) outer membrane protein import receptors, (ii) proteins involved in biogenesis of α-helically anchored outer membrane proteins, and (iii) of the intermembrane space import and assembly system. Finally, it is shown that the unusual presequence-associated import motor of trypanosomes suggests a scenario of how the two ancestral inner membrane protein translocases present in LECA evolved into the single bifunctional one found in extant trypanosomes.

scholarly journals Digalactosyldiacylglycerol Synthase Gene MtDGD1 Plays an Essential Role in Nodule Development and Nitrogen Fixation

2019 ◽  
Vol 32 (9) ◽  
pp. 1196-1209
Author(s):  
Zaiyong Si ◽  
Qianqian Yang ◽  
Rongrong Liang ◽  
Ling Chen ◽  
Dasong Chen ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Essential Role ◽  
Symbiotic Nitrogen Fixation ◽  
Histochemical Staining ◽  
Nodule Development ◽  
Nodule Number ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Infected Cells ◽  
Nodule Symbiosis

Little is known about the genes participating in digalactosyldiacylglycerol (DGDG) synthesis during nodule symbiosis. Here, we identified full-length MtDGD1, a synthase of DGDG, and characterized its effect on symbiotic nitrogen fixation in Medicago truncatula. Immunofluorescence and immunoelectron microscopy showed that MtDGD1 was located on the symbiosome membranes in the infected cells. β-Glucuronidase histochemical staining revealed that MtDGD1 was highly expressed in the infection zone of young nodules as well as in the whole mature nodules. Compared with the control, MtDGD1-RNA interference transgenic plants exhibited significant decreases in nodule number, symbiotic nitrogen fixation activity, and DGDG abundance in the nodules, as well as abnormal nodule and symbiosome development. Overexpression of MtDGD1 resulted in enhancement of nodule number and nitrogen fixation activity. In response to phosphorus starvation, the MtDGD1 expression level was substantially upregulated and the abundance of nonphospholipid DGDG was significantly increased in the roots and nodules, accompanied by corresponding decreases in the abundance of phospholipids such as phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol. Overall, our results indicate that DGD1 contributes to effective nodule organogenesis and nitrogen fixation by affecting the synthesis and content of DGDG during symbiosis.

scholarly journals A Dominant-Negative fur Mutation in Bradyrhizobium japonicum

2004 ◽  
Vol 186 (5) ◽  
pp. 1409-1414 ◽  
Author(s):  
Heather P. Benson ◽  
Kristin LeVier ◽  
Mary Lou Guerinot
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Iron Uptake ◽  
Outer Membrane Proteins ◽  
Dominant Negative ◽  
Ferric Uptake Regulator ◽  
Null Mutant ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Fur Protein

ABSTRACT In many bacteria, the ferric uptake regulator (Fur) protein plays a central role in the regulation of iron uptake genes. Because iron figures prominently in the agriculturally important symbiosis between soybean and its nitrogen-fixing endosymbiont Bradyrhizobium japonicum, we wanted to assess the role of Fur in the interaction. We identified a fur mutant by selecting for manganese resistance. Manganese interacts with the Fur protein and represses iron uptake genes. In the presence of high levels of manganese, bacteria with a wild-type copy of the fur gene repress iron uptake systems and starve for iron, whereas fur mutants fail to repress iron uptake systems and survive. The B. japonicum fur mutant, as expected, fails to repress iron-regulated outer membrane proteins in the presence of iron. Unexpectedly, a wild-type copy of the fur gene cannot complement the fur mutant. Expression of the fur mutant allele in wild-type cells leads to a fur phenotype. Unlike a B. japonicum fur-null mutant, the strain carrying the dominant-negative fur mutation is unable to form functional, nitrogen-fixing nodules on soybean, mung bean, or cowpea, suggesting a role for a Fur-regulated protein or proteins in the symbiosis.

scholarly journals Expression and Functional Roles of Bradyrhizobium japonicum Genes Involved in the Utilization of Inorganic and Organic Sulfur Compounds in Free-Living and Symbiotic Conditions

2011 ◽  
Vol 24 (4) ◽  
pp. 451-457 ◽  
Author(s):  
Masayuki Sugawara ◽  
Gopit R. Shah ◽  
Michael J. Sadowsky ◽  
Oleg Paliy ◽  
Justin Speck ◽  
...  
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Gene Clusters ◽  
Sulfur Source ◽  
Organosulfur Compounds ◽  
In Planta ◽  
Growth And Survival ◽  
Functional Roles ◽  
Organic Sulfur Compounds ◽  
Sulfatase Activity ◽  
Bradyrhizobium Spp

Strains of Bradyrhizobium spp. form nitrogen-fixing symbioses with many legumes, including soybean. Although inorganic sulfur is preferred by bacteria in laboratory conditions, sulfur in agricultural soil is mainly present as sulfonates and sulfur esters. Here, we show that Bradyrhizobium japonicum and B. elkanii strains were able to utilize sulfate, cysteine, sulfonates, and sulfur-ester compounds as sole sulfur sources for growth. Expression and functional analysis revealed that two sets of gene clusters (bll6449 to bll6455 or bll7007 to bll7011) are important for utilization of sulfonates sulfur source. The bll6451 or bll7010 genes are also expressed in the symbiotic nodules. However, B. japonicum mutants defective in either of the sulfonate utilization operons were not affected for symbiosis with soybean, indicating the functional redundancy or availability of other sulfur sources in planta. In accordance, B. japonicum bacteroids possessed significant sulfatase activity. These results indicate that strains of Bradyrhizobium spp. likely use organosulfur compounds for growth and survival in soils, as well as for legume nodulation and nitrogen fixation.

scholarly journals Mutation in a Gene Required for Lipopolysaccharide and Enterobacterial Common Antigen Biosynthesis Affects Virulence in the Plant Pathogen Erwinia carotovora subsp. atroseptica

1999 ◽  
Vol 12 (6) ◽  
pp. 499-507 ◽  
Author(s):  
I. K. Toth ◽  
C. J. Thorpe ◽  
S. D. Bentley ◽  
V. Mulholland ◽  
L. J. Hyman ◽  
...  
Keyword(s):  
Surface Defects ◽  
Single Gene ◽  
Outer Membrane Proteins ◽  
Pectate Lyase ◽  
Erwinia Carotovora ◽  
Enteric Bacteria ◽  
Common Antigen ◽  
In Planta ◽  
Enterobacterial Common Antigen ◽  
Multiple Cell

Spontaneous bacteriophage-resistant mutants of the phytopathogen Erwinia carotovora subsp. atroseptica (Eca) SCRI1043 were isolated and, out of 40, two were found to exhibit reduced virulence in planta. One of these mutants, A5/22, showed multiple cell surface defects including alterations in synthesis of outer membrane proteins, lipopolysaccharide (LPS), enterobacterial common antigen (ECA), and flagella. Mutant A5/22 also showed reduced synthesis of the exoenzymes pectate lyase (Pel) and cellulase (Cel), major virulence factors for this pathogen. Genetic analysis revealed the pronounced pleiotropic mutant phenotype to be due to a defect in a single gene (rffG) that, in Escherichia coli, is involved in the production of ECA. We also show that while other enteric bacteria possess duplicate homologues of this gene dedicated separately to synthesis of LPS and ECA, Eca has a single gene.

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