Do mitochondria provide the oxygen diffusion barrier in root nodules of Coriaria and Datisca?

1999 ◽  
Vol 77 (9) ◽  
pp. 1358-1366 ◽  
Author(s):  
Warwick B Silvester ◽  
Birgit Langenstein ◽  
R Howard Berg
Keyword(s):  
Nitrogen Fixation ◽  
Oxygen Diffusion ◽  
Root Nodules ◽  
Root Systems ◽  
Cationic Dye ◽  
Central Vacuole ◽  
Tetrazolium Chloride ◽  
Transmission Electron ◽  
Oxygen Protection ◽  
Reducing Potential

Root nodules of Coriaria Lindsay and Datisca Baill. display a unique anatomy in which the symbiotic vesicles radiate inwards towards a central vacuole. Use of the confocal microscope and the redox dye cyano-tetrazolium chloride demonstrates that the vesicles are the sites of reducing potential and that there is a sharp cut-off in reducing potential at the base of the vesicles. The use of the lipophylic cationic dye rhodamine 123 revealed a continuous blanket of mitochondria in this zone. This was verified by transmission electron microscope views of nodule cells. Further studies reveal that the mitochondrial layer also forms a discontinuous layer around the intercellular air spaces. The nodules of plants grown with root systems at 5 and 40 kPa O2 did not show any differences in the thickness of the mitochondrial layer. Microtubules are also radially arranged in these cells and mitochondria are likely to reach their position by moving along this radial framework.Key words: actinorhiza, mitochondria, nitrogen fixation, nitrogenase, nodule, oxygen protection.

Hopanoid lipids inFrankia: identification of squalene-hopene cyclase gene sequences

2001 ◽  
Vol 47 (6) ◽  
pp. 535-540 ◽  
Author(s):  
Svetlana V Dobritsa ◽  
Dan Potter ◽  
Timothy E Gookin ◽  
Alison M Berry
Keyword(s):  
Polymerase Chain Reaction ◽  
Dna Sequences ◽  
Oxygen Diffusion ◽  
Root Nodules ◽  
Pcr Primers ◽  
Coding Region ◽  
Chain Reaction ◽  
Wide Range ◽  
Oxygen Protection ◽  
Polymerase Chain

In Frankia, the microsymbiont in actinorhizal root nodules, nitrogen fixation takes place in specialized structures called vesicles. The lipidic vesicle envelope forms a barrier to oxygen diffusion, an essential part of the nitrogenase oxygen protection system. We have shown previously that the vesicle envelope is composed primarily of two species of hopanoid lipids, sterol-like molecules that are synthesized in a wide range of bacteria, including Frankia, several cyanobacteria, and rhizobia. The levels of hopanoid found in Frankia are among the highest of any organism known to date. Here we report that short (328-bp) DNA sequences from several strains of Frankia spp. have been identified that are homologous to a portion of the coding region of squalene-hopene cyclase (shc) genes. The fragments and corresponding polymerase chain reaction (PCR) primers can be used in phylogenetic comparisons of Frankia, both within Frankiaceae and among bacteria that synthesize hopanoids.Key words: Frankia, squalene-hopene cyclase, shc, hopanoid, phylogeny, actinorhizal.

Low-temperature annealing of YBa2Cu3O7-x

1992 ◽  
Vol 50 (1) ◽  
pp. 88-89
Author(s):  
R.L. Sabatini ◽  
Yimei Zhu ◽  
Masaki Suenaga ◽  
A.R. Moodenbaugh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Oxygen Diffusion ◽  
Diffusion Rate ◽  
Oxygen Depletion ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Microstructural Effects ◽  
Oxygen Diffusion Rate

Low temperature annealing (<400°C) of YBa2Cu3O7x in a ozone containing oxygen atmosphere is sometimes carried out to oxygenate oxygen deficient thin films. Also, this technique can be used to fully oxygenate thinned TEM specimens when oxygen depletion in thin regions is suspected. However, the effects on the microstructure nor the extent of oxygenation of specimens has not been documented for specimens exposed to an ozone atmosphere. A particular concern is the fact that the ozone gas is so reactive and the oxygen diffusion rate at these temperatures is so slow that it may damage the specimen by an over-reaction. Thus we report here the results of an investigation on the microstructural effects of exposing a thinned YBa2Cu3O7-x specimen in an ozone atmosphere using transmission electron microscopy and energy loss spectroscopy techniques.

The Effects of Nitrogen on Electrical and Structural Properties in TaSixNy/SiO2/p-Si MOS Capacitors

2002 ◽  
Vol 716 ◽  
Author(s):  
You-Seok Suh ◽  
Greg Heuss ◽  
Jae-Hoon Lee ◽  
Veena Misra
Keyword(s):  
Structural Properties ◽  
Electron Spectroscopy ◽  
Oxygen Diffusion ◽  
Gate Dielectric ◽  
Barrier Properties ◽  
Reaction Rates ◽  
Cross Sectional ◽  
Mos Capacitors ◽  
Transmission Electron ◽  
Thermal Stability Of

AbstractIn this work, we report the effects of nitrogen on electrical and structural properties in TaSixNy /SiO2/p-Si MOS capacitors. TaSixNy films with various compositions were deposited by reactive sputtering of TaSi2 or by co-sputtering of Ta and Si targets in argon and nitrogen ambient. TaSixNy films were characterized by Rutherford backscattering spectroscopy and Auger electron spectroscopy. It was found that the workfunction of TaSixNy (Si>Ta) with varying N contents ranges from 4.2 to 4.3 eV. Cross-sectional transmission electron microscopy shows no indication of interfacial reaction or crystallization in TaSixNy on SiO2, resulting in no significant increase of leakage current in the capacitor during annealing. It is believed that nitrogen retards reaction rates and improves the chemical-thermal stability of the gate-dielectric interface and oxygen diffusion barrier properties.

scholarly journals Mutation in the ntrR Gene, a Member of the vap Gene Family, Increases the Symbiotic Efficiency of Sinorhizobium meliloti

2001 ◽  
Vol 14 (7) ◽  
pp. 887-894 ◽  
Author(s):  
Boglárka Oláh ◽  
Erno Kiss ◽  
Zoltán Györgypál ◽  
Judit Borzi ◽  
Gyöngyi Cinege ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pathogenic Bacteria ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Nifh Gene ◽  
Dry Weight ◽  
Nodule Occupancy ◽  
Gene Encoding ◽  
Symbiotic Efficiency ◽  
Host Interactions

In specific plant organs, namely the root nodules of alfalfa, fixed nitrogen (ammonia) produced by the symbiotic partner Sinorhizobium meliloti supports the growth of the host plant in nitrogen-depleted environment. Here, we report that a derivative of S. meliloti carrying a mutation in the chromosomal ntrR gene induced nodules with enhanced nitrogen fixation capacity, resulting in an increased dry weight and nitrogen content of alfalfa. The efficient nitrogen fixation is a result of the higher expression level of the nifH gene, encoding one of the subunits of the nitrogenase enzyme, and nifA, the transcriptional regulator of the nif operon. The ntrR gene, controlled negatively by its own product and positively by the symbiotic regulator syrM, is expressed in the same zone of nodules as the nif genes. As a result of the nitrogen-tolerant phenotype of the strain, the beneficial effect of the mutation on efficiency is not abolished in the presence of the exogenous nitrogen source. The ntrR mutant is highly competitive in nodule occupancy compared with the wild-type strain. Sequence analysis of the mutant region revealed a new cluster of genes, termed the “ntrPR operon,” which is highly homologous to a group of vap-related genes of various pathogenic bacteria that are presumably implicated in bacterium-host interactions. On the basis of its favorable properties, the strain is a good candidate for future agricultural utilization.

scholarly journals NITROGEN FIXATION BY EXCISED SOY BEAN ROOT NODULES

1954 ◽  
Vol 208 (1) ◽  
pp. 29-39
Author(s):  
M.H. Aprison ◽  
Wayne E. Magee ◽  
R.H. Burris
Keyword(s):  
Nitrogen Fixation ◽  
Root Nodules ◽  
Bean Root

scholarly journals Multimodal Spectroscopic Imaging of Pea Root Nodules to Assess the Nitrogen Fixation in the Presence of Biofertilizer Based on Nod-Factors

2021 ◽  
Vol 22 (23) ◽  
pp. 12991
Author(s):  
Katarzyna Susniak ◽  
Mikolaj Krysa ◽  
Dominika Kidaj ◽  
Monika Szymanska-Chargot ◽  
Iwona Komaniecka ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Mass Spectrometry Imaging ◽  
Root Nodules ◽  
Spectroscopic Imaging ◽  
Ionization Mass ◽  
Nod Factors ◽  
Pea Root ◽  
Ft Ir ◽  
Ir And Raman ◽  
Apparent Distribution

Multimodal spectroscopic imaging methods such as Matrix Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI MSI), Fourier Transform Infrared spectroscopy (FT-IR) and Raman spectroscopy were used to monitor the changes in distribution and to determine semi quantitatively selected metabolites involved in nitrogen fixation in pea root nodules. These approaches were used to evaluate the effectiveness of nitrogen fixation by pea plants treated with biofertilizer preparations containing Nod factors. To assess the effectiveness of biofertilizer, the fresh and dry masses of plants were determined. The biofertilizer was shown to be effective in enhancing the growth of the pea plants. In case of metabolic changes, the biofertilizer caused a change in the apparent distribution of the leghaemoglobin from the edges of the nodule to its centre (the active zone of nodule). Moreover, the enhanced nitrogen fixation and presumably the accelerated maturation form of the nodules were observed with the use of a biofertilizer.

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