scholarly journals Nodule Development Induced by Mesorhizobium loti Mutant Strains Affected in Polysaccharide Synthesis

2005 ◽  
Vol 18 (5) ◽  
pp. 446-457 ◽  
Author(s):  
Alejandra L. D'Antuono ◽  
Adriana Casabuono ◽  
Alicia Couto ◽  
Rodolfo A. Ugalde ◽  
Viviana C. Lepek
Keyword(s):  
Pleiotropic Effect ◽  
Nodule Development ◽  
Wild Type ◽  
Mesorhizobium Loti ◽  
O Antigen ◽  
Polysaccharide Synthesis ◽  
Infection Threads ◽  
Surface Polysaccharides ◽  
Hair Curling

The role of Mesorhizobium loti surface polysaccharides on the nodulation process is not yet fully understood. In this article, we describe the nodulation phenotype of mutants affected in the synthesis of lipopolysaccharide (LPS) and β(1,2) cyclic glucan. M. loti lps β2 mutant produces LPS with reduced amount of O-antigen, whereas M. loti lps β1 mutant produces LPS totally devoid of O-antigen. Both genes are clustered in the chromosome. Based on amino acid sequence homology, LPS sugar composition, and enzymatic activity, we concluded that lps β2 codes for an enzyme involved in the transformation of dTDP-glucose into dTDP-rhamnose, the sugar donor of rhamnose for the synthesis of O-antigen. On the other hand, lps β1 codes for a glucosyl transferase involved in the biosynthesis of the O-antigen. Although LPS mutants elicited normal nodules, both show reduced competitiveness compared with the wild type. M. loti β(1-2) cyclic glucan synthase (cgs) mutant induces white, empty, ineffective pseudonodules in Lotus tenuis. Cgs mutant induces normal root hair curling but is unable to induce the formation of infection threads. M. loti cgs mutant was more sensitive to deoxycholate and displayed motility impairment compared with the wild-type strain. This pleiotropic effect depends on calcium concentration and temperature.

scholarly journals Glucomannan-Mediated Attachment of Rhizobium leguminosarum to Pea Root Hairs Is Required for Competitive Nodule Infection

2008 ◽  
Vol 190 (13) ◽  
pp. 4706-4715 ◽  
Author(s):  
Alan Williams ◽  
Adam Wilkinson ◽  
Martin Krehenbrink ◽  
Daniela M. Russo ◽  
Angeles Zorreguieta ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Rhizobium Leguminosarum ◽  
Root Hairs ◽  
The Other ◽  
Plant Interactions ◽  
Wild Type ◽  
Polysaccharide Synthesis ◽  
Surface Polysaccharides

ABSTRACT The Rhizobium leguminosarum biovar viciae genome contains several genes predicted to determine surface polysaccharides. Mutants predicted to affect the initial steps of polysaccharide synthesis were identified and characterized. In addition to the known cellulose (cel) and acidic exopolysaccharide (EPS) (pss) genes, we mutated three other loci; one of these loci (gmsA) determines glucomannan synthesis and one (gelA) determines a gel-forming polysaccharide, but the role of the other locus (an exoY-like gene) was not identified. Mutants were tested for attachment and biofilm formation in vitro and on root hairs; the mutant lacking the EPS was defective for both of these characteristics, but mutation of gelA or the exoY-like gene had no effect on either type of attachment. The cellulose (celA) mutant attached and formed normal biofilms in vitro, but it did not form a biofilm on root hairs, although attachment did occur. The cellulose-dependent biofilm on root hairs appears not to be critical for nodulation, because the celA mutant competed with the wild-type for nodule infection. The glucomannan (gmsA) mutant attached and formed normal biofilms in vitro, but it was defective for attachment and biofilm formation on root hairs. Although this mutant formed nodules on peas, it was very strongly outcompeted by the wild type in mixed inoculations, showing that glucomannan is critical for competitive nodulation. The polysaccharide synthesis genes around gmsA are highly conserved among other rhizobia and agrobacteria but are absent from closely related bacteria (such as Brucella spp.) that are not normally plant associated, suggesting that these genes may play a wide role in bacterium-plant interactions.

scholarly journals NO Network for Plant–Microbe Communication Underground: A Review

2021 ◽  
Vol 12 ◽  
Author(s):  
Anjali Pande ◽  
Bong-Gyu Mun ◽  
Da-Sol Lee ◽  
Murtaza Khan ◽  
Geun-Mo Lee ◽  
...  
Keyword(s):  
Mycorrhizal Fungi ◽  
Nodule Development ◽  
Symbiotic Interaction ◽  
Plant Microbe Interaction ◽  
Nodule Senescence ◽  
Infection Threads ◽  
Molecular Patterns ◽  
Defense Studies ◽  
Hair Curling

Mechanisms governing plant–microbe interaction in the rhizosphere attracted a lot of investigative attention in the last decade. The rhizosphere is not simply a source of nutrients and support for the plants; it is rather an ecosystem teeming with diverse flora and fauna including different groups of microbes that are useful as well as harmful for the plants. Plant–microbe interaction occurs via a highly complex communication network that involves sophisticated machinery for the recognition of friend and foe at both sides. On the other hand, nitric oxide (NO) is a key, signaling molecule involved in plant development and defense. Studies on legume–rhizobia symbiosis suggest the involvement of NO during recognition, root hair curling, development of infection threads, nodule development, and nodule senescence. A similar role of NO is also suggested in the case of plant interaction with the mycorrhizal fungi. Another, insight into the plant–microbe interaction in the rhizosphere comes from the recognition of pathogen-associated molecular patterns (PAMPs)/microbe-associated molecular patterns (MAMPs) by the host plant and thereby NO-mediated activation of the defense signaling cascade. Thus, NO plays a major role in mediating the communication between plants and microbes in the rhizosphere. Interestingly, reports suggesting the role of silicon in increasing the number of nodules, enhancing nitrogen fixation, and also the combined effect of silicon and NO may indicate a possibility of their interaction in mediating microbial communication underground. However, the exact role of NO in mediating plant–microbe interaction remains elusive. Therefore, understanding the role of NO in underground plant physiology is very important, especially in relation to the plant’s interaction with the rhizospheric microbiome. This will help devise new strategies for protection against phytopathogens and enhancing plant productivity by promoting symbiotic interaction. This review focuses on the role of NO in plant–microbe communication underground.

scholarly journals Role of Trehalose Transport and Utilization in Sinorhizobium meliloti-Alfalfa Interactions

2005 ◽  
Vol 18 (7) ◽  
pp. 694-702 ◽  
Author(s):  
John Beck Jensen ◽  
Osei Yaw Ampomah ◽  
Richard Darrah ◽  
N. Kent Peters ◽  
T. V. Bhuvaneswari
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Sinorhizobium Meliloti ◽  
Brucella Melitensis ◽  
Sole Source ◽  
Root Surface ◽  
Wild Type ◽  
Major Pathway ◽  
Mesorhizobium Loti ◽  
Infection Threads

Genes thuA and thuB in Sinorhizobium meliloti Rm1021 code for a major pathway for trehalose catabolism and are induced by trehalose but not by related structurally similar disaccharides like sucrose or maltose. S. meliloti strains mutated in either of these two genes were severely impaired in their ability to grow on trehalose as the sole source of carbon. ThuA and ThuB show no homology to any known enzymes in trehalose utilization. ThuA has similarity to proteins of unknown function in Mesorhizobium loti, Agrobacterium tumefaciens, and Brucella melitensis, and ThuB possesses homology to dehydrogenases containing the consensus motif AGKHVXCEKP. thuAB genes are expressed in bacteria growing on the root surface and in the infection threads but not in the symbiotic zone of the nodules. Even though thuA and thuB mutants were impaired in competitive colonization of Medicago sativa roots, these strains were more competitive than the wild-type Rm1021 in infecting alfalfa roots and forming nitrogen-fixing nodules. Possible reasons for their increased competitiveness are discussed.

scholarly journals Fimbria-Encoding GeneyadCHas a Pleiotropic Effect on Several Biological Characteristics and Plays a Role in Avian Pathogenic Escherichia coli Pathogenicity

2015 ◽  
Vol 84 (1) ◽  
pp. 187-193 ◽  
Author(s):  
Renu Verma ◽  
Thaís Cabrera Galvão Rojas ◽  
Renato Pariz Maluta ◽  
Janaína Luisa Leite ◽  
Livia Pilatti Mendes da Silva ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Soft Agar ◽  
Pleiotropic Effect ◽  
Biological Characteristics ◽  
Wild Type ◽  
Content Type ◽  
Pathogenic Escherichia Coli

The extraintestinal pathogen termed avian pathogenicEscherichia coli(APEC) is known to cause colibacillosis in chickens. The molecular basis of APEC pathogenesis is not fully elucidated yet. In this work, we deleted a component of the Yad gene cluster (yadC) in order to understand the role of Yad in the pathogenicity of the APEC strain SCI-07.In vitro, the transcription level ofyadCwas upregulated at 41°C and downregulated at 22°C. TheyadCexpressionin vivowas more pronounced in lungs than in spleen, suggesting a role in the early steps of the infection. Chicks infected with the wild-type and mutant strains presented, respectively, 80% and 50% mortality rates. The ΔyadCstrain presented a slightly decreased ability to adhere to HeLa cells with or without thed-mannose analog compared with the wild type. Real-time PCR (RT-PCR) assays showed thatfimHwas downregulated (P< 0.05) andcsgAandecpAwere slightly upregulated in the mutant strain, showing thatyadCmodulates expression of other fimbriae. Bacterial internalization studies showed that the ΔyadCstrain had a lower number of intracellular bacteria recovered from Hep-2 cells and HD11 cells than the wild-type strain (P< 0.05). Motility assays in soft agar demonstrated that the ΔyadCstrain was less motile than the wild type (P< 0.01). Curiously, flagellum-associated genes were not dramatically downregulated in the ΔyadCstrain. Taken together, the results show that the fimbrial adhesin Yad contributes to the pathogenicity and modulates different biological characteristics of the APEC strain SCI-07.

scholarly journals MtBZR1 Plays an Important Role in Nodule Development in Medicago truncatula

2019 ◽  
Vol 20 (12) ◽  
pp. 2941
Author(s):  
Can Cui ◽  
Hongfeng Wang ◽  
Limei Hong ◽  
Yiteng Xu ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Normal Growth ◽  
Dry Mass ◽  
Growth Conditions ◽  
Nodule Development ◽  
Functional Study ◽  
Loss Of Function ◽  
Wild Type

Brassinosteroid (BR) is an essential hormone in plant growth and development. The BR signaling pathway was extensively studied, in which BRASSINAZOLE RESISTANT 1 (BZR1) functions as a key regulator. Here, we carried out a functional study of the homolog of BZR1 in Medicago truncatula R108, whose expression was induced in nodules upon Sinorhizobium meliloti 1021 inoculation. We identified a loss-of-function mutant mtbzr1-1 and generated 35S:MtBZR1 transgenic lines for further analysis at the genetic level. Both the mutant and the overexpression lines of MtBZR1 showed no obvious phenotypic changes under normal growth conditions. After S. meliloti 1021 inoculation, however, the shoot and root dry mass was reduced in mtbzr1-1 compared with the wild type, caused by partially impaired nodule development. The transcriptomic analysis identified 1319 differentially expressed genes in mtbzr1-1 compared with wild type, many of which are involved in nodule development and secondary metabolite biosynthesis. Our results demonstrate the role of MtBZR1 in nodule development in M. truncatula, shedding light on the potential role of BR in legume–rhizobium symbiosis.

Rhizobitoxine production and symbiotic compatibility of Bradyrhizobium from Asian and North American lineages of Amphicarpaea

2001 ◽  
Vol 47 (10) ◽  
pp. 889-894 ◽  
Author(s):  
Matthew A Parker ◽  
N Kent Peters
Keyword(s):  
North American ◽  
Nodule Development ◽  
Close Relative ◽  
Inhibition Assay ◽  
Wild Type ◽  
The North ◽  
Leaf Chlorosis ◽  
Bradyrhizobium Sp ◽  
Bradyrhizobium Elkanii

Reciprocal inoculations with Bradyrhizobium sp. isolates from the North American legume Amphicarpaea bracteata (L.) Fern. (Phaseoleae-Glycininae) and from a Japanese population of its close relative Amphicarpaea edgeworthii (Benth.) var. japonica were performed to analyze relative symbiotic compatibility. Amphicarpaea edgeworthii plants formed few or no nodules with any North American bradyrhizobial strains isolated from A. bracteata, but all A. bracteata lineages formed effective nitrogen-fixing nodules with Japanese Bradyrhizobium isolates from A. edgeworthii. However, one group of A. bracteata plants (lineage Ia) when inoculated with Japanese bradyrhizobia developed a striking leaf chlorosis similar to that known to be caused by rhizobitoxine. The β-cystathionase inhibition assay demonstrated that significant amounts of rhizobitoxine were present in nodules formed by these Japanese bradyrhizobia. No North American bradyrhizobial isolate from A. bracteata induced chlorosis on any plants, and the β-cystathionase assay failed to detect rhizobitoxine in nodules formed by these isolates. The role of rhizobitoxine in A. edgeworthii nodulation development was tested by inoculating plants with a Bradyrhizobium elkanii rhizobitoxine-producing strain, USDA 61, and two mutant derivatives, RX17E and RX18E, which are unable to synthesize rhizobitoxine. Amphicarpaea edgeworthii inoculated with wild-type USDA 61 developed >150 nodules per plant, while plants inoculated with RX17E and RX18E developed fewer than 10 nodules per plant. Thus, efficient nodule development in A. edgeworthii appears to be highly dependent on rhizobitoxine production by Bradyrhizobium strains.Key words: Bradyrhizobium elkanii, geographic variation, Leguminosae, mutualism.

Alteration of O-specific polysaccharide structure of symbiotically defective Mesorhizobium loti mutant 2213.1 derived from strain NZP2213.

2008 ◽  
Vol 55 (1) ◽  
pp. 191-200 ◽  
Author(s):  
Anna Turska-Szewczuk ◽  
Hubert Pietras ◽  
Wojciech Borucki ◽  
Ryszard Russa
Keyword(s):  
Wild Type Strain ◽  
2D Nmr ◽  
Chain Structure ◽  
Wild Type ◽  
Immunoblot Assay ◽  
Mesorhizobium Loti ◽  
Nmr Data ◽  
Specific Polysaccharide ◽  
C Nmr

Mesorhizobium loti mutant 2213.1 derived from the wild-type strain NZP2213 by Tn5 mutagenesis showed impaired effectiveness of symbiosis with the host plant Lotus corniculatus (Turska-Szewczuk et al., 2007 Microbiol Res, in press). The inability of lipopolysaccharide (LPS) isolated from the mutant 2213.1 strain or de-O-acetylated LPS of the parental cells to inactivate phage A1 particles implicated alterations in the LPS structure. The O-specific polysaccharide of the mutant was studied by chemical analyses along with (1)H and (13)C NMR spectroscopy, which clearly confirmed alterations in the O-chain structure. 2D NMR data showed that the mutant O-polysaccharide consists of a tetrasaccharide repeating unit containing non-substituted as well as O-acetylated or O-methylated 6-deoxytalopyranose residues. Additionally, an immunogold assay revealed a reduced number of gold particles on the mutant bacteroid cell surface, which could result from both a diminished amount of an O-antigenic determinant in mutant LPS and modifications of structural epitopes caused by alterations in O-acetylation or O-methylation of sugar residues. Western immunoblot assay of alkaline de-O-acetylated lipophilic M. loti NZP2213 LPS showed no reactivity with homologous serum indicating a role of O-acetyl groups in its O-specificity.

scholarly journals Defects in Rhizobial Cyclic Glucan and Lipopolysaccharide Synthesis Alter Legume Gene Expression During Nodule Development

2008 ◽  
Vol 21 (1) ◽  
pp. 50-60 ◽  
Author(s):  
Alejandra L. D'Antuono ◽  
Thomas Ott ◽  
Lene Krusell ◽  
Vera Voroshilova ◽  
Rodolfo A. Ugalde ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mutant Strain ◽  
Early Recognition ◽  
Lotus Japonicus ◽  
Cdna Array ◽  
Nodule Development ◽  
Marker Genes ◽  
Wild Type ◽  
Mesorhizobium Loti ◽  
Expression Of Genes

cDNA array technology was used to compare transcriptome profiles of Lotus japonicus roots inoculated with a Mesorhizobium loti wild-type and two mutant strains affected in cyclic β(1-2) glucan synthesis (cgs) and in lipopolysaccharide synthesis (lpsβ2). Expression of genes associated with the development of a fully functional nodule was significantly affected in plants inoculated with the cgs mutant. Array results also revealed that induction of marker genes for nodule development was delayed when plants were inoculated with the lpsβ2 mutant. Quantitative real-time reverse-transcriptase polymerase chain reaction was used to quantify gene expression of a subset of genes involved in plant defense response, redox metabolism, or genes that encode for nodulins. The majority of the genes analyzed in this study were more highly expressed in roots inoculated with the wild type compared with those inoculated with the cgs mutant strain. Some of the genes exhibited a transient increase in transcript levels during intermediate steps of normal nodule development while others displayed induced expression during the final steps of nodule development. Ineffective nodules induced by the glucan mutant showed higher expression of phenylalanine ammonia lyase than wild-type nodules. Differences in expression pattern of genes involved in early recognition and signaling were observed in plants inoculated with the M. loti mutant strain affected in the synthesis of cyclic glucan.

scholarly journals Role of RpoS in Fine-Tuning the Synthesis of Vi Capsular Polysaccharide in Salmonella enterica Serotype Typhi

2006 ◽  
Vol 75 (3) ◽  
pp. 1382-1392 ◽  
Author(s):  
Javier Santander ◽  
Soo-Young Wanda ◽  
Cheryl A. Nickerson ◽  
Roy Curtiss
Keyword(s):  
Salmonella Enterica ◽  
Capsular Polysaccharide ◽  
Fine Tuning ◽  
O Antigen ◽  
Native Promoter ◽  
Regulatory Systems ◽  
Polysaccharide Synthesis ◽  
Clinical Detection ◽  
Vi Capsular Polysaccharide

ABSTRACT Regulation of the synthesis of Vi polysaccharide, a major virulence determinant in Salmonella enterica serotype Typhi, is under the control of two regulatory systems, ompR-envZ and rscB-rscC, which respond to changes in osmolarity. Some serotype Typhi strains exhibit overexpression of Vi polysaccharide, which masks clinical detection of lipopolysaccharide O antigen. This variation in Vi polysaccharide and O antigen display (VW variation) has been observed since the initial studies of serotype Typhi. In this study, we report that rpoS plays a role in this increased expression in Vi polysaccharide. We constructed a variety of isogenic serotype Typhi mutants that differed in their expression levels of RpoS and examined the role of the rpoS product in synthesis of Vi polysaccharide under different osmolarity conditions. Vi polysaccharide synthesis was also examined in serotype Typhi mutants in which the native promoter of the rpoS was replaced by an araCPBAD cassette, so that the expression of rpoS was arabinose dependent. The RpoS− strains showed increased syntheses of Vi polysaccharide, which at low and medium osmolarities masked O antigen detection. In contrast, RpoS+ strains showed lower syntheses of Vi polysaccharide, and an increased detection of O antigen was observed. During exponential growth, when rpoS is unstable or present at low levels, serotype Typhi RpoS+ strains overexpress the Vi polysaccharide at levels comparable to those for RpoS− strains. Our results show that RpoS is another regulator of Vi polysaccharide synthesis and contributes to VW variation in serotype Typhi, which has implications for the development of recombinant attenuated Salmonella vaccines in humans.

scholarly journals Varying the Abundance of O Antigen inRhizobium etli and Its Effect on Symbiosis withPhaseolus vulgaris

2000 ◽  
Vol 182 (19) ◽  
pp. 5317-5324 ◽  
Author(s):  
K. Dale Noel ◽  
Lennart S. Forsberg ◽  
Russell W. Carlson
Keyword(s):  
Phaseolus Vulgaris ◽  
Structural Feature ◽  
Gel Electrophoresis ◽  
Genetic Locus ◽  
Normal Amount ◽  
Wild Type ◽  
Sugar Composition ◽  
Genetic Region ◽  
O Antigen

ABSTRACT Judged by migration of its lipopolysaccharide (LPS) in gel electrophoresis, the O antigen of Rhizobium etli mutant strain CE166 was apparently of normal size. However, its LPS sugar composition and staining of the LPS bands after electrophoresis indicated that the proportion of its LPS molecules that possessed O antigen was only 40% of the wild-type value. Its LPS also differed from the wild type by lacking quinovosamine (2-amino-2,6-dideoxyglucose). Both of these defects were due to a single genetic locus carrying a Tn5 insertion. The deficiency in O-antigen amount, but not the absence of quinovosamine, was suppressed by transferring into this strain recombinant plasmids that shared a 7.8-kb stretch of the R. etli CE3lps genetic region α, even though this suppressing DNA did not carry the genetic region mutated in strain CE166. Strain CE166 gave rise to pseudonodules on legume host Phaseolus vulgaris, whereas the mutant suppressed by DNA fromlps region α elicited nitrogen-fixing nodules. However, the nodules in the latter case developed slowly and were widely dispersed. Two other R. etli mutants that had one-half or less of the normal amount of O antigen also gave rise to pseudonodules on P. vulgaris. The latter strains were mutated inlps region α and could be restored to normal LPS content and normal symbiosis by complementation with wild-type DNA from this region. Hence, the symbiotic role of LPS requires near-normal abundance of O antigen and may require a structural feature conferred by quinovosamine.

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