Early production of rhizopine in nodules induced bySinorhizobium melilotistrain L5-30

2001 ◽  
Vol 47 (2) ◽  
pp. 165-171 ◽  
Author(s):  
K Heinrich ◽  
M H Ryder ◽  
P J Murphy
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Fold Increase ◽  
Gas Chromatography Mass Spectrometry ◽  
Post Inoculation ◽  
Infection Threads ◽  
Nodulation Competitiveness ◽  
Meliloti Strain ◽  
Early Production ◽  
Early Effects

The rhizopine L-3-O-methyl-scyllo-inosamine (3-O-MSI) is metabolized by approximately 10% of the strains of Rhizobium leguminosarum bv. viciae and Sinorhizobium meliloti. Rhizopine strains enjoy a substantial competitive advantage in nodulation, which is manifest before 14 days post-inoculation, implying that rhizopine is produced before this time. We were able to detect this compound in the roots of alfalfa (Medicago sativum L. cv. Hunter River) four days after germination (six days post-infection) with S. meliloti strain L5-30 by gas chromatography-mass spectrometry (GC-MS). At four days, nodules were not visible, and the concentration of rhizopine was extremely low, estimated at 67 pg/gfw (picograms/gram fresh weight). The amount increased gradually but remained low until 16 days, when there was a 50-fold increase from day four, by which time nodules were well established. This pattern of synthesis is consistent with previous studies indicating that rhizopine synthesis is regulated by nifA/ntrA regulatory genes, which are maximally expressed in bacteroids at the onset of nitrogen fixation. However, the low level of rhizopine synthesis must be responsible for the early effects on competition for nodulation. Production of rhizopine at this time most likely results from micro-aerobic induction of mos genes in free-living bacteria, either in the infection threads or in the rhizosphere.Key words: Medicago sativum, nodulation competitiveness, Rhizobium, rhizopine, Sinorhizobium meliloti.

scholarly journals Involvement of Diamine Oxidase and Peroxidase in Insolubilization of the Extracellular Matrix: Implications for Pea Nodule Initiation by Rhizobium leguminosarum

2000 ◽  
Vol 13 (4) ◽  
pp. 413-420 ◽  
Author(s):  
J.-P. Wisniewski ◽  
E. A. Rathbun ◽  
J. P. Knox ◽  
N. J. Brewin
Keyword(s):  
Diamine Oxidase ◽  
Rhizobium Leguminosarum ◽  
Plant Cell Wall ◽  
Extracellular Enzymes ◽  
Host Cells ◽  
Soluble Form ◽  
Post Inoculation ◽  
Root Tips ◽  
Pea Seedlings ◽  
Infection Threads

Rhizobium leguminosarum colonizes host cells and tissues through infection threads, which are tubular in-growths of the plant cell wall. Monoclonal antibody MAC265 recognizes a plant matrix glycoprotein (MGP) associated with the lumen of these infection threads. This glycoprotein is also released in soluble form from the root tips of pea seedlings. In the presence of hydrogen peroxide, release of glycoprotein from root tips was not observed. Extractability from root tips was therefore used as the basis for investigating the peroxide-driven insolubilization of MGP and the possible involvement of two extracellular enzymes, peroxidase (POD) and diamine oxidase (DAO), was investigated. Release of MGP from root tips was enhanced by application of POD and DAO inhibitors (salicylhy-droxamic acid and o-phenanthroline, respectively). Furthermore, release of MGP was inhibited by pretreatment of roots with putrescine (the substrate of DAO) and also by application of a partially purified extract of DAO from pea shoots. Following inoculation of pea roots with R. le-guminosarum, elevated levels of DAO transcript were observed by reverse transcriptase-polymerase chain reaction (RT-PCR), but these then dropped to a low level from 4 to 10 days post inoculation, rising again in more mature nodules. In situ hybridization studies indicated that the bulk of the transcription was associated with the infected tissue in the center of the nodule. On the basis of these observations, we postulate that DAO may be involved in the peroxide-driven hardening of MGP in the lumen of infection threads and in the intercellular matrix.

scholarly journals Expression of an Exogenous 1-Aminocyclopropane-1-Carboxylate Deaminase Gene in Sinorhizobium meliloti Increases Its Ability To Nodulate Alfalfa

2004 ◽  
Vol 70 (10) ◽  
pp. 5891-5897 ◽  
Author(s):  
Wenbo Ma ◽  
Trevor C. Charles ◽  
Bernard R. Glick
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Higher Plants ◽  
Regulatory Gene ◽  
Regulatory Protein ◽  
Acc Deaminase ◽  
Plasmid Vector ◽  
Plant Growth Promoting Rhizobacteria ◽  
Infection Threads ◽  
Plant Growth Promoting

ABSTRACT 1-Aminocyclopropane-1-carboxylate (ACC) deaminase has been found in various plant growth-promoting rhizobacteria, including rhizobia. This enzyme degrades ACC, the immediate precursor of ethylene, and thus decreases the biosynthesis of ethylene in higher plants. The ACC deaminase of Rhizobium leguminosarum bv. viciae 128C53K was previously reported to be able to enhance nodulation of peas. The ACC deaminase structural gene (acdS) and its upstream regulatory gene, a leucine-responsive regulatory protein (LRP)-like gene (lrpL), from R. leguminosarum bv. viciae 128C53K were introduced into Sinorhizobium meliloti, which does not produce this enzyme, in two different ways: through a plasmid vector and by in situ transposon replacement. The resulting ACC deaminase-producing S. meliloti strains showed 35 to 40% greater efficiency in nodulating Medicago sativa (alfalfa), likely by reducing ethylene production in the host plants. Furthermore, the ACC deaminase-producing S. meliloti strain was more competitive in nodulation than the wild-type strain. We postulate that the increased competitiveness might be related to utilization of ACC as a nutrient within the infection threads.

scholarly journals Analysis of the chromosome sequence of the legume symbiont Sinorhizobium meliloti strain 1021

2001 ◽  
Vol 98 (17) ◽  
pp. 9877-9882 ◽  
Author(s):  
D. Capela ◽  
F. Barloy-Hubler ◽  
J. Gouzy ◽  
G. Bothe ◽  
F. Ampe ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Chromosome Sequence ◽  
Meliloti Strain

scholarly journals H2O2 Is Required for Optimal Establishment of the Medicago sativa/Sinorhizobium meliloti Symbiosis

2007 ◽  
Vol 189 (23) ◽  
pp. 8741-8745 ◽  
Author(s):  
Alexandre Jamet ◽  
Karine Mandon ◽  
Alain Puppo ◽  
Didier Hérouart
Keyword(s):  
Medicago Sativa ◽  
Plant Cell ◽  
Sinorhizobium Meliloti ◽  
Root Hairs ◽  
Symbiotic Interaction ◽  
Infection Threads ◽  
Cell Layers

ABSTRACT The symbiotic interaction between Medicago sativa and Sinorhizobium meliloti RmkatB ++ overexpressing the housekeeping catalase katB is delayed, and this delay is combined with an enlargement of infection threads. This result provides evidence that H2O2 is required for optimal progression of infection threads through the root hairs and plant cell layers.

A rhizobial homolog of IHF stimulates transcription of dctA in Rhizobium leguminosarum but not in Sinorhizobium meliloti

Gene ◽  
1999 ◽  
Vol 238 (2) ◽  
pp. 489-500 ◽  
Author(s):  
John Sojda ◽  
Baohua Gu ◽  
Joon Lee ◽  
Timothy R Hoover ◽  
B.Tracy Nixon
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum

scholarly journals Alfalfa Root Nodule Invasion Efficiency Is Dependent on Sinorhizobium melilotiPolysaccharides

2000 ◽  
Vol 182 (15) ◽  
pp. 4310-4318 ◽  
Author(s):  
Brett J. Pellock ◽  
Hai-Ping Cheng ◽  
Graham C. Walker
Keyword(s):  
Molecular Weight ◽  
Sinorhizobium Meliloti ◽  
Root Nodule ◽  
Fluorescent Protein ◽  
Infection Thread ◽  
Low Molecular Weight ◽  
Infection Threads ◽  
Green Fluorescent ◽  
K Antigen ◽  
Alfalfa Root

ABSTRACT The soil bacterium Sinorhizobium meliloti is capable of entering into a nitrogen-fixing symbiosis with Medicago sativa (alfalfa). Particular low-molecular-weight forms of certain polysaccharides produced by S. meliloti are crucial for establishing this symbiosis. Alfalfa nodule invasion by S. meliloti can be mediated by any one of three symbiotically important polysaccharides: succinoglycan, EPS II, or K antigen (also referred to as KPS). Using green fluorescent protein-labeled S. meliloti cells, we have shown that there are significant differences in the details and efficiencies of nodule invasion mediated by these polysaccharides. Succinoglycan is highly efficient in mediating both infection thread initiation and extension. However, EPS II is significantly less efficient than succinoglycan at mediating both invasion steps, and K antigen is significantly less efficient than succinoglycan at mediating infection thread extension. In the case of EPS II-mediated symbioses, the reduction in invasion efficiency results in stunted host plant growth relative to plants inoculated with succinoglycan or K-antigen-producing strains. Additionally, EPS II- and K-antigen-mediated infection threads are 8 to 10 times more likely to have aberrant morphologies than those mediated by succinoglycan. These data have important implications for understanding how S. meliloti polysaccharides are functioning in the plant-bacterium interaction, and models are discussed.

scholarly journals Elevated Serum Sorbitol and not Fructose in Type 2 Diabetic Patients

2010 ◽  
Vol 5 ◽  
pp. BMI.S4530 ◽  
Author(s):  
Gregory M. Preston ◽  
Roberto A. Calle
Keyword(s):  
Elevated Serum ◽  
Fold Increase ◽  
Clinical Development ◽  
Gas Chromatography Mass Spectrometry ◽  
Diabetic Patients ◽  
Dose Selection ◽  
Type 2 Diabetic Patients ◽  
Early Proof ◽  
Proof Of Mechanism

Reductions in fasting serum fructose or erythrocyte sorbitol have been proposed as markers for early proof of mechanism in clinical development of aldose reductase (AR) inhibitors. However fructose is significantly impacted by meals and evaluation of erythrocyte sorbitol poses technical challenges. To more accurately assess the performance of these markers in biological samples, a gas chromatography-mass spectrometry assay was modified and validated. Serum was collected on three consecutive days from 13 healthy volunteers (HV) and 14 patients with type 2 diabetes mellitus (T2DM), and assayed for sorbitol and fructose using this assay. Serum fructose and sorbitol were relatively constant across the three days. Fasting fructose levels were comparable between the two groups (T2DM: 1.48 ± 0.49 mg/L; HV: 1.39 ± 0.38 mg/L, mean ± standard deviation, P = 0.61), but fasting sorbitol levels were significantly higher in diabetics (T2DM: 0.280 ± 0.163 mg/L; HV: 0.164 ± 0.044 mg/L, P = 0.02). Feeding resulted in a 5–6 fold increase in serum fructose levels, but only a 5%-10% increase in sorbitol. Only sorbitol remained significantly elevated pre- and post feeding in T2DM patients relative to HV. These data suggest that serum sorbitol may be a robust proof of mechanism biomarker and facilitate dose selection for clinical development of AR inhibitors.

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