scholarly journals A Gene That Encodes a Proline-Rich Nodulin with Limited Homology to PsENOD12 Is Expressed in the Invasion Zone of Rhizobium meliloti-Induced Alfalfa Root Nodules

1993 ◽  
Vol 103 (1) ◽  
pp. 21-30 ◽  
Author(s):  
M. Lobler ◽  
A. M. Hirsch
Keyword(s):  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Alfalfa Root

Comparison of the genomic arrangement and the relative transcription of the nitrogenase genes in Rhizobium meliloti during symbiotic development in alfalfa root nodules

1982 ◽  
Vol 28 (12) ◽  
pp. 1330-1339 ◽  
Author(s):  
Alan S. Paau ◽  
Winston J. Brill
Keyword(s):  
Rhizobium Meliloti ◽  
Protein Pattern ◽  
Root Nodules ◽  
Symbiotic Association ◽  
Free Living ◽  
Genomic Arrangement ◽  
Infection Threads ◽  
Nitrogenase Genes ◽  
Specific Amplification ◽  
Alfalfa Root

In the course of the symbiotic development of free-living rhizobia to mature bacteroids in alfalfa nodules, mRNA transcripts of the nitrogenase structural genes are first detected when the rhizobia are inside the infection threads. These transcripts are most abundant in the mature bacteroids of young (6 to 8 weeks) root nodules and are present in a much lower level in bacteroids from senescent root nodules (13 weeks). Translation of these and related rhizobial genes essential for the symbiotic association apparently occurs very early in the symbiosis because the protein pattern of the "infection thread rhizobia" is very similar to that of the mature bacteroids and is different from that of the cultured vegetative rhizobia. Although bacteroids have a higher DNA content than the vegetative bacteria and are very different in the nucleoid organization, no specific amplification or rearrangement of the nitrogenase genes is detected in bacteroids.

Effect of Low Nitrate Supply on Nitrogen Fixation in Alfalfa Root Nodules Induced by Rhizobium meliloti Strains with Varied Nitrate Reductase Activity

1989 ◽  
Vol 135 (2) ◽  
pp. 207-211 ◽  
Author(s):  
Cesáreo Arrese-Igor ◽  
José M. Estavillo ◽  
José I. Peña ◽  
Carmen Gonzalez-Murua ◽  
Pedro M. Aparicio-Tejo
Keyword(s):  
Nitrogen Fixation ◽  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Rhizobium Meliloti ◽  
Reductase Activity ◽  
Root Nodules ◽  
Nitrate Supply ◽  
Alfalfa Root

scholarly journals Bio-chemical characterization of rhizobia isolated from root nodules of Velvet bean (Mucuna pruriens L.)

Our Nature ◽  
2017 ◽  
Vol 15 (1-2) ◽  
pp. 7-12 ◽  
Author(s):  
Som Prasad Paudyal ◽  
Vimal NP Gupta
Keyword(s):  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Chemical Characterization ◽  
High Sensitivity ◽  
Mucuna Pruriens ◽  
Velvet Bean ◽  
Trigonella Foenum Graecum ◽  
Antibiotics Sensitivity ◽  
The Himalaya

Rhizobia are the symbiotic bacteria found in the soil which have potential ability to convert atmospheric di-nitrogen into usable form. A total of ten rhizobial strains were isolated from the root nodules of a medicinal legume Mucuna pruriens (L.) that commonly grow in the foothills of the Himalaya. All the ten   strains isolated from different locations of same area were morphologically, biochemically and physiologically characterized based on the Bergey’s Manual of systematic Bacteriology. They were tested for the antibiotics sensitivity. The isolates showed high sensitivity to amoxicillin and least to erythromycin. Authentication test was done in eleven legumes but shown nodulations only in Trigonella foenum-graecum, Mucuna pruriens and Medicago sativa. The morphology, physiology, biochemical and infection test studies carried out justifies that the bacteria isolated belonged to the species of Rhizobium meliloti.

Reactive oxygen species accumulation patterns of alfalfa root nodules identified using an optimized method

2019 ◽  
Vol 51 (4) ◽  
pp. 448-451
Author(s):  
Liangliang Yu ◽  
Leqi Huang ◽  
Shuang Zeng ◽  
Guirong Tang ◽  
Sunjun Wang ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Root Nodules ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Reactive Oxygen Species Accumulation ◽  
Species Accumulation ◽  
Alfalfa Root

scholarly journals Malic Enzyme Cofactor and Domain Requirements for Symbiotic N2 Fixation by Sinorhizobium meliloti

2006 ◽  
Vol 189 (1) ◽  
pp. 160-168 ◽  
Author(s):  
Michael J. Mitsch ◽  
Alison Cowie ◽  
Turlough M. Finan
Keyword(s):  
Amino Acid ◽  
Malic Enzyme ◽  
Sinorhizobium Meliloti ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
High Ratio ◽  
Terminal Region ◽  
Wild Type ◽  
Mutant Strains ◽  
Alfalfa Root

ABSTRACT The NAD+-dependent malic enzyme (DME) and the NADP+-dependent malic enzyme (TME) of Sinorhizobium meliloti are representatives of a distinct class of malic enzymes that contain a 440-amino-acid N-terminal region homologous to other malic enzymes and a 330-amino-acid C-terminal region with similarity to phosphotransacetylase enzymes (PTA). We have shown previously that dme mutants of S. meliloti fail to fix N2 (Fix−) in alfalfa root nodules, whereas tme mutants are unimpaired in their N2-fixing ability (Fix+). Here we report that the amount of DME protein in bacteroids is 10 times greater than that of TME. We therefore investigated whether increased TME activity in nodules would allow TME to function in place of DME. The tme gene was placed under the control of the dme promoter, and despite elevated levels of TME within bacteroids, no symbiotic nitrogen fixation occurred in dme mutant strains. Conversely, expression of dme from the tme promoter resulted in a large reduction in DME activity and symbiotic N2 fixation. Hence, TME cannot replace the symbiotic requirement for DME. In further experiments we investigated the DME PTA-like domain and showed that it is not required for N2 fixation. Thus, expression of a DME C-terminal deletion derivative or the Escherichia coli NAD+-dependent malic enzyme (sfcA), both of which lack the PTA-like region, restored wild-type N2 fixation to a dme mutant. Our results have defined the symbiotic requirements for malic enzyme and raise the possibility that a constant high ratio of NADPH + H+ to NADP in nitrogen-fixing bacteroids prevents TME from functioning in N2-fixing bacteroids.

Gene Expression of Medicago sativa Inoculated with Sinorhizobium meliloti as Modulated by the Xenobiotics Cadmium and Fluoranthene

2000 ◽  
Vol 55 (3-4) ◽  
pp. 222-232 ◽  
Author(s):  
Heike Neumann ◽  
Dietrich Werner
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Medicago Sativa ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Cadmium Concentration ◽  
Transcript Level ◽  
Northern Hybridization ◽  
Fresh Weight

Abstract Alfalfa plants (Medicago sativa cv. Europe) inoculated with Sinorhizobium meliloti 2011 (formerly Rhizobium meliloti, de Lajudie et al., 1994) were cultivated for 14 days under standardized growth conditions in mineral medium with addition of the heavy metal cadmium or the polycyclic aromatic hydrocarbon fluoranthene. These xenobiotics significantly reduced the numbers of root nodules before any visible damage to the plant could be detected. EC10. EC50, and EC90 (effective concentrations reducing nodulation, shoot and root fresh weight by 10, 50, or 90% compared to the control without pollutant) were calculated. EC50 for cadmium ranged from 5.8 jam (nodulation) to more than 20 μᴍ (root fresh weight). Testing fluoranthene resulted in an EC50 of 2.5 μg cm-2 for nodulation, and EC50 values of more than 35 μg cm-2 for shoot and root biomass production, indicating that the effect parameter nodulation is 10-fold more sensitive than shoot and root fresh weight. With m RNA differential display techniques the effects of both xenobiotics on gene expression in alfalfa root systems were studied. 37 differentially displayed transcripts were detected. Two of them, called DDMs1 and DDMs2, were confirmed by northern hybridization to be down-regulated in the presence of the xenobiotics. The expression of transcript DDMs1 was enhanced in alfalfa control plants inoculated with rhizobia, the transcript level was increased 2.5-3-fold compared to non-inoculated plants. This positive effect of nodulation was suppressed, partly by 35 μg cm-2 fluoranthene and totally by 20 μᴍ cadmium. The decrease in DDMsl transcription was highly affected by the cadmium concentration with an EC50 of 5.9 μᴍ . Compared to nodulation, almost identical EC10, EC50. and EC90 values were found for DDMsl expression. Sequence analysis of DDMsl revealed a significant overall homology (50% identity) to a hypothetical protein from Arabidopsis thaliana with high similarity to a copper transporting ATPase. High levels of transcript DDMs2 were observed in control plants with a 50% decrease in the xenobiotic-treated plants. DDM s2 gave a strong homology (82% identity) to the cytoplasmatic 60S ribosomal protein L18 from Arabidopsis thaliana.

Ineffectiveness of viomycin-resistant mutants of Rhizobium meliloti

1969 ◽  
Vol 15 (7) ◽  
pp. 671-675 ◽  
Author(s):  
G. S. Hendry ◽  
D. C. Jordan
Keyword(s):  
Cell Wall ◽  
Nitrogen Fixation ◽  
Parent Strain ◽  
Rhizobium Meliloti ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Effective Strain ◽  
One Step ◽  
Increased Sensitivity ◽  
Resistant Mutants

Under clearly defined conditions one-step acquisition of viomycin resistance by a normally effective strain of Rhizobium meliloti resulted in one-step acquisition of ineffectiveness in nitrogen fixation, which probably occurred with a one-gene change in the R. meliloti genome. Two-step mutants retained their ability to produce root nodules but such nodules also were ineffective. Increased sensitivity of the viomycin-resistant mutants to glycine and D-alanine was not noted. Bacteroids were not seen in nodules formed by the viomycin-resistant mutants on their homologous host plant. Nitrogenase activity was not detected, by acetylene reduction, in detached ineffective nodules, whereas effective nodules formed 10.6 μmoles of ethylene per hour per gram of nodules. Growth of the effective parent strain in a low concentration of viomycin resulted in elongation and swelling of the cells so that they appeared as artificially produced bacteroids. Viomycin-resistant mutants did not undergo this transformation. Antigens could be readily extracted by hot- and cold-saline extraction of wet packed cells of both resistant and sensitive cultures but antigenic differences, which may have indicated cell wall differences, were not noted.

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