Rhizobium–Legume Symbiosis: A Model System for the Recovery of Metal-Contaminated Agricultural Land

Salinization of agricultural land is a devastating phenomenon which will affect future food security. Understanding how plants survive and thrive in response to salinity is therefore critical to potentiate tolerance traits in crop species. The halophyte Salicornia europaea has been used as model system for this purpose. High salinity causes NH4+ accumulation in plant tissues and consequent toxicity symptoms that may further exacerbate those caused by NaCl. In this experiment we exposed Salicornia plants to five concentrations of NaCl (0, 1, 10, 50 and 200 mM) in combination with two concentrations of NH4Cl (1 and 50 mM). We confirmed the euhalophytic behavior of Salicornia that grew better at 200 vs. 0 mM NaCl in terms of both fresh (+34%) and dry (+46%) weights. Addition of 50 mM NH4Cl to the growth medium caused a general growth reduction, which was likely caused by NH4+ accumulation and toxicity in roots and shoots. When plants were exposed to high NH4Cl, high salinity reduced roots NH4+ concentration (−50%) compared to 0 mM NaCl. This correlates with the activation of the NH4+ assimilation enzymes, glutamine synthetase and glutamate dehydrogenase, and the growth inhibition was partially recovered. We argue that NH4+ detoxification is an important trait under high salinity that may differentiate halophytes from glycophytes and we present a possible model for NH4+ detoxification in response to salinity.

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The Rhizobium-Legume Symbiosis: Co-opting Successful Stress Management

Frontiers in Plant Science ◽

10.3389/fpls.2021.796045 ◽

2022 ◽

Vol 12 ◽

Author(s):

Justin P. Hawkins ◽

Ivan J. Oresnik

Keyword(s):

Model System ◽

Low Ph ◽

Complex Signal ◽

Tolerance Mechanisms ◽

Positive Interaction ◽

Bacterial Response ◽

Plant Peptides ◽

Legume Symbiosis ◽

Growth Inhibiting ◽

Signal Exchange

The interaction of bacteria with plants can result in either a positive, negative, or neutral association. The rhizobium-legume interaction is a well-studied model system of a process that is considered a positive interaction. This process has evolved to require a complex signal exchange between the host and the symbiont. During this process, rhizobia are subject to several stresses, including low pH, oxidative stress, osmotic stress, as well as growth inhibiting plant peptides. A great deal of work has been carried out to characterize the bacterial response to these stresses. Many of the responses to stress are also observed to have key roles in symbiotic signaling. We propose that stress tolerance responses have been co-opted by the plant and bacterial partners to play a role in the complex signal exchange that occurs between rhizobia and legumes to establish functional symbiosis. This review will cover how rhizobia tolerate stresses, and how aspects of these tolerance mechanisms play a role in signal exchange between rhizobia and legumes.

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A Protozoan Model for Golgi-Associated Calcification

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065705 ◽

1971 ◽

Vol 29 ◽

pp. 332-333

Author(s):

D. C. Williams ◽

D. E. Outka

Keyword(s):

Golgi Apparatus ◽

Organic Matrix ◽

Model System ◽

Sequential Formation

Many studies have shown that the Golgi apparatus is involved in a variety of synthetic activities, and probably no Golgi product is more elaborate than the scales produced by various kinds of phytoflagellates. The formation of calcified scales (coccoliths, Fig. 1,2) of the coccolithophorid phytoflagellates provides a particularly interesting model system for the study of biological mineralization, and the sequential formation of Golgi products.The coccoliths of Hymenomonas carterae consist of a scale-like base (Fig. 2 and 4, b) with a highly structured calcified (CaCO3) rim composed of two distinct elements which alternate about the base periphery (Fig. 1 and 3, A, B). Each element is enveloped by a sheath-like organic matrix (Fig. 3; Fig. 4, m).

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Existence of DNA in yeast microbodies

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082029 ◽

1978 ◽

Vol 36 (2) ◽

pp. 232-233

Author(s):

Masako Osumi ◽

Misuzu Nagano ◽

Hiroko Kazama

Keyword(s):

Catalase Activity ◽

Buoyant Density ◽

Model System ◽

Contour Length ◽

Native State ◽

Normal Alkane ◽

Remarkable Increase ◽

Dna Molecule ◽

Mitochondrial Dnas

We have found that microbodies appeared profusely together with a remarkable increase in catalase activity in normal alkane-grown cells of hydrocarbon-utilizing Candida yeasts, and that the microbodies multiplied by division in these cells. These features of Candida yeasts seem to provide a useful model system for studies on the biogenesis of the microbody. Subsequently, we have succeeded in isolation of Candida microbodies in an apparently native state, as judged biochemically and morphologically. The presence of DNA in the purified microbody fraction thus obtained was proved by the diphenylamine method. DNA molecule of about 15 urn in contour length was released from an isolated microbody. The physicochemical analyses of the microbody DNA revealed that its buoyant density differed from nuclear and mitochondrial DNAs. All these results lead us to the possibility that there is a novel type of DNA in microbodies.

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The coprecipitation of Cr3P and Cr in Cu

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105886 ◽

1988 ◽

Vol 46 ◽

pp. 764-765

Author(s):

M.J. Witcomb ◽

U. Dahmen ◽

K.H. Westmacott

Keyword(s):

Orientation Relationship ◽

Interface Structure ◽

Model System ◽

Relative Orientation ◽

Age Hardening ◽

Precipitation Behavior ◽

Solution Treated ◽

Small Needle ◽

Diffraction Patterns ◽

Interface Structures

Cu-Cr age-hardening alloys are of interest as a model system for the investigation of fcc/bcc interface structures. Several past studies have investigated the morphology and interface structure of Cr precipitates in a Cu matrix (1-3) and good success has been achieved in understanding the crystallography and strain contrast of small needle-shaped precipitates. The present study investigates the effect of small amounts of phosphorous on the precipitation behavior of Cu-Cr alloys.The same Cu-0.3% Cr alloy as was used in earlier work was rolled to a thickness of 150 μm, solution treated in vacuum at 1050°C for 1h followed by quenching and annealing for various times at 820 and 863°C.Two laths and their corresponding diffraction patterns in an alloy aged 2h at 820°C are shown in correct relative orientation in Fig. 1. To within the limit of accuracy of the diffraction patterns the orientation relationship was that of Kurdjumov-Sachs (KS), i.e. parallel close-packed planes and directions.

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Membrane-associated microtubular areays induced in proximal myelinated processes of dorsal root ganglia by large doses of vitamin B6

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143468 ◽

1986 ◽

Vol 44 ◽

pp. 368-369

Author(s):

V.J. Montpetit ◽

S. Dancea ◽

L. Tryphonas ◽

D.F. Clapin

Keyword(s):

Animal Model ◽

Endoplasmic Reticulum ◽

Dorsal Root Ganglia ◽

Rough Endoplasmic Reticulum ◽

Dorsal Root ◽

Vitamin B6 ◽

Morphological Changes ◽

Model System ◽

Sensory Nerves ◽

Peripheral Sensory

Very large doses of pyridoxine (vitamin B6) are neurotoxic in humans, selectively affecting the peripheral sensory nerves. We have undertaken a study of the morphological and biochemical aspects of pyridoxine neurotoxicity in an animal model system. Early morphological changes in dorsal root ganglia (DRG) associated with pyridoxine megadoses include proliferation of neurofilaments, ribosomes, rough endoplasmic reticulum, and Golgi complexes. We present in this report evidence of the formation of unique aggregates of microtubules and membranes in the proximal processes of DRG which are induced by high levels of pyridoxine.

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An Ultrastructural Comparison of Hepatocytes from ADH+ and ADH−Peromyscus Maniculatus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100162612 ◽

1996 ◽

Vol 54 ◽

pp. 30-31

Author(s):

J. T. Ellzey ◽

D. Borunda ◽

B. P. Stewart

Keyword(s):

South Carolina ◽

Adult Male ◽

Uranyl Acetate ◽

Model System ◽

Deer Mice ◽

En Bloc ◽

Genetic Stock ◽

Hepes Buffer ◽

Transmission Electron ◽

Color Scanner

Genetically alcohol deficient deer mice (ADHN/ADHN) (obtained from the Peromyscus Genetic Stock Center, Univ. of South Carolina) lack hepatic cytosolic alcohol dehydrogenase. In order to determine if these deer mice would provide a model system for an ultrastructural study of the effects of ethanol on hepatocyte organelles, 75 micrographs of ADH+ adult male deer mice (n=5) were compared with 75 micrographs of ADH− adult male deer mice (n=5). A morphometric analysis of mitochondrial and peroxisomal parameters was undertaken.The livers were perfused with 0.1M HEPES buffer followed by 0.25% glutaraldehyde and 2% sucrose in 0.1M HEPES buffer (4C), removed, weighed and fixed by immersion in 2.5% glutaraldehyde in 0.1M HEPES buffer, pH 7.4, followed by a 3,3’ diaminobenzidine (DAB) incubation, postfixation with 2% OsO4, en bloc staining with 1% uranyl acetate in 0.025M maleate-NaOH buffer, dehydrated, embedded in Poly/Bed 812-BDMA epon resin, sectioned and poststained with uranyl acetate and lead citrate. Photographs were taken on a Zeiss EM-10 transmission electron microscope, scanned with a Howtek personal color scanner, analyzed with OPTIMAS 4.02 software on a Gateway2000 4DX2-66V personal computer and stored in Excel 4.0.

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Elemental analysis of human erythrocytes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015318x ◽

1989 ◽

Vol 47 ◽

pp. 242-243

Author(s):

S. A. Livesey ◽

A. A. del Campo ◽

E. S. Griffey ◽

D. Ohlmer ◽

T. Schifani ◽

...

Keyword(s):

Sample Preparation ◽

Elemental Analysis ◽

Human Erythrocyte ◽

Spectroscopic Analysis ◽

Model System ◽

Human Erythrocytes ◽

List Type ◽

Chemical Fixation ◽

Ethanol Dehydration ◽

Lowicryl K4m

The aim of this study is to compare methods of sample preparation for elemental analysis. The model system which is used is the human erythrocyte. Energy dispersive spectroscopic analysis has been previously reported for cryofixed and cryosectioned erythrocytes. Such work represents the reference point for this study. The use of plastic embedded samples for elemental analysis has also been documented. The work which is presented here is based on human erythrocytes which have been either chemically fixed and embedded or cryofixed and subsequently processed by a variety of techniques which culminated in plastic embedded samples.Heparinized and washed erythrocytes were prepared by the following methods for this study :(1). Chemical fixation in 4% paraformaldehyde/0.25% glutaraldehyde/0.2 M sucrose in 0.1 M Na cacodylate, pH 7.3 for 30 min, followed by ethanol dehydration, infiltration and embedding in Lowicryl K4M at -20° C.

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