Changes in actin microfilament arrays in developing pea root nodule cells

2001 ◽  
Vol 79 (7) ◽  
pp. 767-776 ◽  
Author(s):  
A L Davidson ◽  
W Newcomb
Keyword(s):  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Infection Process ◽  
Host Cells ◽  
Actin Microfilaments ◽  
Symbiotic Associations ◽  
Actin Microfilament ◽  
Pea Root ◽  
Microfilament Bundles ◽  
Infected Cells

Various microorganisms that form symbiotic associations with plant roots alter the cytoskeleton of host cells. The objective of this study was to determine the organization of actin microfilaments in developing Pisum sativum L. (pea) root nodule cells at various stages after infection by Rhizobium leguminosarum bv. viciae. Fluorescently labelled microfilaments in uninfected pea root nodule cells occur in association with the nucleus, along cytoplasmic strands, and as long microfilament bundles randomly organized in the cortex of the cell. These actin arrays are also present in recently infected cells that have been invaded by an infection thread and contain a small number of bacteroids. In addition, the recently infected cells contain diffuse cytoplasmic actin, long actin microfilament bundles near the vacuole, and a nuclear-associated network of microfilament bundles. In older infected cells, the predominant array is a network of cytoplasmic microfilaments that are wavy and extend in multiple directions within the cell; the network is equally abundant in all regions of the cytoplasm and may interact with the bacteroids and organelles. Thus, actin microfilaments reorganize during the pea root nodule infection process to form distinct arrays whose organization depends on the stage of infection.Key words: nodule, actin microfilaments, Rhizobium, pea, symbiosis.

Organization of microtubules in developing pea root nodule cells

2001 ◽  
Vol 79 (7) ◽  
pp. 777-786
Author(s):  
A L Davidson ◽  
W Newcomb
Keyword(s):  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Root Nodules ◽  
Cell Cortex ◽  
Cortical Microtubules ◽  
Microtubule Organization ◽  
Pea Root ◽  
Fluorescence And Electron Microscopy ◽  
Infected Cells ◽  
Cytoplasmic Microtubules

Pisum sativum L. (pea) root nodule cells undergo many cellular changes in response to infection by Rhizobium leguminosarum bv. viciae. These include cell growth, organelle reorganization, and changes relating to the increase in the number of bacteria within the cell. The objective of this study was to characterize microtubule organization during nodule cell development. The organization of microtubules was examined in developing pea root nodules using fluorescence and electron microscopy techniques. Immunolabelling of microtubules in meristematic cells showed diffuse fluorescence in the cell cortex and adjacent to the nuclear envelope. Recently infected cells contained randomly oriented cortical microtubules and cytoplasmic microtubules that were fragmented with diffuse fluorescence. Infected cells contained an extensive network of long, randomly arranged cortical microtubules with some parallel bundles. Cytoplasmic microtubules in single optical sections of infected cells appeared as short undulating filaments; however, overlapping images from a Z-series of an infected cell showed that the microtubules are long and wavy, and generally radiate inward from the cell cortex.Key words: nodule, microtubules, Rhizobium, pea, symbiosis.

Ultrastructure of eastern cottonwood clones susceptible or resistant to leaf rust

1987 ◽  
Vol 65 (8) ◽  
pp. 1586-1598 ◽  
Author(s):  
L. Shain ◽  
U. Järlfors
Keyword(s):  
Electron Microscopy ◽  
Leaf Rust ◽  
Light And Electron Microscopy ◽  
Infection Process ◽  
The Other ◽  
Host Cells ◽  
Eastern Cottonwood ◽  
Melampsora Medusae ◽  
Wall Appositions ◽  
Infected Cells

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused by Melampsora medusae was studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.

scholarly journals The Endothelial Cytoskeleton: Organization in Normal and Regenerating Endothelium*

1990 ◽  
Vol 18 (4a) ◽  
pp. 603-617 ◽  
Author(s):  
Avrum I. Gotlieb
Keyword(s):  
Shear Stress ◽  
Structural Integrity ◽  
Phorbol Esters ◽  
Actin Microfilaments ◽  
Actin Microfilament ◽  
Cytoskeleton Organization ◽  
Cell Locomotion ◽  
Microfilament Bundles ◽  
External Stimuli ◽  
Hemodynamic Shear Stress

The components of the endothelial cell cytoskeleton that have been shown to be important in maintaining endothelial structural integrity and in regulating endothelial repair include F-actin microfilament bundles, including stress fibers, and microtubules, and centrosomes. Endothelial cells contain peripheral and central actin microfilaments. The dense peripheral band (DPB) consists of peripheral actin microfilament bundles which are associated with vinculin adhesion plaques and are most prominent in low or no hemodynamic shear stress conditions. The central microfilaments are very prominent in areas of elevated hemodynamic shear stress. There is a redistribution of actin microfilaments characterized by a decrease of peripheral actin and an increase in central microfilaments under a variety of conditions, including exposure to thrombin, phorbol-esters, and hemodynamic shear stress. During reendothelialization, there is a sequential series of cytoskeletal changes. The DPB remains intact during the rapid lamellipodia mediated repair of very small wounds except at the base of the lamellipodia where it is splayed. The DPB is reduced or absent when cell locomotion occurs to repair a wound. In addition, when cell locomotion is required, the centrosome, in the presence of intact microtubules, redistributes to the front of the cell to establish cell polarity and acts as a modulator of the directionality of migration. This occurs prior to the loss of the DPB but does not occur in very small wounds that close without migration. Thus, the cytoskeleton is a dynamic intracellular system which regulates endothelial integrity and repair and is modulated by external stimuli that are present at the vessel wall-blood interface.

Development of an ineffective pea root nodule: morphogenesis, fine structure, and cytokinin biosynthesis

1977 ◽  
Vol 55 (14) ◽  
pp. 1891-1907 ◽  
Author(s):  
William Newcomb ◽  
Kunihiko Syono ◽  
John G. Torrey
Keyword(s):  
Rhizobium Leguminosarum ◽  
Nitrogenase Activity ◽  
Zeatin Riboside ◽  
Infection Process ◽  
Nodule Development ◽  
Cytokinin Biosynthesis ◽  
Low Frequencies ◽  
Host Cytoplasm ◽  
Host Membrane ◽  
Infected Cells

Roots of the garden pea Pisam sativum L. cv. Little Marvel inoculated with Rhizobium leguminosarum strain 1019 produce small white nodules which are ineffective in fixing atmospheric nitrogen. Analyses of cytokinin contents of the nodules at different ages using extraction, purification, and thin-layer chromatographic separation showed that the cytokinins zeatin and zeatin riboside and isopentenyladenine and its riboside were present in greatest amounts early in nodule development and decreased thereafter. A new unidentified cytokinin was present in older nodules. The early stages of the infection process in the ineffective nodules were similar to those observed in effective nodules. However, bacteria released from the bacterial thread via an unwalled droplet were not always surrounded by a host membrane. In later stages of nodule development many infected cells contained rhizobia with no enclosing membranes so that the bacteria were free within the host cytoplasm. Such cells showed very low frequencies of mitochondria, of polyribosomes, and endoplasmic reticulum. Thus, the biosynthetic capacity of the cells appeared to be impaired and membrane synthesis defective. The failure of the nodules to develop nitrogenase activity is probably related to the failure of membrane formation around the bacteria. Abnormalities in amyloplast formation were also noted, as well as structural differences in the nodule, including a higher proportion of uninfected cells and earlier cessation of mitotic activity in the nodule meristem than occurs in effective nodules of pea. Transfer cells were observed in the pericycle in both effective and ineffective nodules.

scholarly journals A comparative cytological and morphometric analysis of vacuolation in central tissue of the effective and ineffective pea (Pisum sativum L.) root nodules

2011 ◽  
Vol 76 (2) ◽  
pp. 109-118 ◽  
Author(s):  
Wojciech Borucki
Keyword(s):  
Root Nodule ◽  
Root Nodules ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Thin Layers ◽  
Central Vacuole ◽  
Dynamic Changes ◽  
Pea Root ◽  
Dimensional Reconstruction ◽  
Infected Cells

Vacuoles play very important physiological roles in plant cells. Pea root nodules, which exhibit distinct zonation (meristematic zone and central tissue zones), may serve as a good experimental model for the investigations of vacuole development and its importance to cell and tissue functioning. Moreover, the nodule central tissue is composed of both infected and uninfected cells which play different physiological roles and differ in the level of vacuolation. Cytological observations revealed that central vacuoles of the infected cells of the effective nodules expand toward cell walls. Thus only thin layers of the cytoplasm separate each central vacuole from plasma membrane and cell wall. This finding is discussed from the viewpoint of improved exchange of solutes and water between the central vacuole and apoplast of the infected cell. Three-dimensional reconstruction of the vacuoles of infected cells within a fragment of effective nodule central tissue, showed their spatial arrangement. Possible advantages coming from the spatial arrangement of vacuoles within the central tissue are discussed. A comparative study of the central tissue (bacteroidal tissue) and meristem vacuolation of the effective and ineffective pea root nodules is also presented. Morphometric measurements revealed that the effective nodule central tissue was more vacuolated than the ineffective one. It was proved that maturation of the infected cells involves dynamic changes in their vacuolation. Having numerous fixing nitrogen bacteroids, the infected cells of effective central tissue were less vacuolated than uninfected cells. On the other hand, both infected and uninfected cells of the effective central tissue showed a much higher level of vacuolation in nitrogen-fixing zone than cells of the same type in ineffective tissue. These results indicate that vacuolation is an important factor in development and functioning of pea root nodule central tissue.

scholarly journals Early events in living epidermal cells of cowpea and broad bean during infection with basidiospores of the cowpea rust fungus

1991 ◽  
Vol 69 (10) ◽  
pp. 2279-2285 ◽  
Author(s):  
Haixin Xu ◽  
Kurt Mendgen
Keyword(s):  
Vicia Faba ◽  
Broad Bean ◽  
Rust Fungus ◽  
Infection Process ◽  
Host Cells ◽  
Appressorium Formation ◽  
Vigna Sinensis ◽  
Infected Cells ◽  
Uromyces Vignae ◽  
Defence Reactions

The infection process of basidiospores of the cowpea rust fungus (Uromyces vignae) was studied on living host (Vigna sinensis) and nonhost (Vicia faba) leaves using light microscopy with differential interference contrast optics. During the first 8 h, fungal development was similar on host and on nonhost leaves. Penetration and production of intraepidermal vesicles occurred in nonhost cells 4 h earlier than in host cells. Penetration frequency was also higher in nonhost leaves. These results suggest that the cuticle of the cowpea plant delays basidiospore infection. Both host and nonhost cells produced cytoplasmic aggregates during appressorium formation and again, a few hours later, during penetration of the epidermal cell wall. Cytoplasmic aggregates were also observed in cells adjacent to a collapsing cell. Papillae were observed at most infection sites in both host and nonhost cells. The nuclei of infected cells migrated towards the penetration site in both plant–pathogen combinations. Nuclear size increased considerably only in the nonhost epidermis and decreased again markedly after cell collapse. In the nonhost cells, three types of defence reactions occurred during or after formation of the intraepidermal vesicle. First, following the halt of cytoplasmic streaming, the cytoplasm of the invaded cell either contracted or disintegrated into granules. Alternatively, the cytoplasm continued streaming but darkly pigmented material encased the fungal infection structure. Key words: basidiospore, broad bean (Vicia faba), cowpea (Vigna sinensis), cowpea rust fungus (Uromyces vignae), hypersensitivity, nonhost resistance.

Changes in actin microfilament arrays in developing pea root nodule cells

2001 ◽  
Vol 79 (7) ◽  
pp. 767-776 ◽  
Author(s):  
A.L. Davidson ◽  
W. Newcomb
Keyword(s):  
Root Nodule ◽  
Actin Microfilament ◽  
Pea Root

Gene expression during the infection process in nodulating and nonnodulating pea genotypes

1989 ◽  
Vol 67 (9) ◽  
pp. 2535-2538 ◽  
Author(s):  
M. F. Le Gal ◽  
S. L. A. Hobbs ◽  
C. M. O. Delong
Keyword(s):  
Gene Expression ◽  
North American ◽  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Infection Process ◽  
In Vitro Translation ◽  
Protein Patterns ◽  
Pisum Sativum L ◽  
Root Proteins

Pea (Pisum sativum L.) cv. Afghanistan inoculated with Rhizobium leguminosarum biovar. viciae aborts the nodulation process if North American strains are used but will form effective nodules with strain TOM. Early nodulins (nodule specific root proteins) were examined by in vitro translation of total root or root + nodule RNA and two-dimensional gel analysis. Qualitatively different protein patterns were found between effective nodulation in Trapper (a North American variety) and 'Afghanistan' and between effective and abortive nodulation in 'Afghanistan'. Six days after inoculation a 26-kDa protein was evident that was only produced in Trapper roots and several nodulins were visible. Nodulin N-37 was present in effective and abortive combinations. Nodulin N-52 was present in inoculated Trapper but not in inoculated 'Afghanistan', whereas N-23 was present in inoculated 'Afghanistan' but not in inoculated Trapper. Nodulin N-58 occurred only in abortive combinations with 'Afghanistan'. Nonnodulating Trapper (Trapper into which the nonnodulation genes of 'Afghanistan' had been back-crossed) showed the same patterns of gene expression as 'Afghanistan'. The expression of several genes apparently differs between 'Afghanistan' and Trapper for the nodulation process.

scholarly journals Helicobacter pylori Outer Membrane Vesicles and Extracellular Vesicles from Helicobacter pylori-Infected Cells in Gastric Disease Development

2021 ◽  
Vol 22 (9) ◽  
pp. 4823
Author(s):  
María Fernanda González ◽  
Paula Díaz ◽  
Alejandra Sandoval-Bórquez ◽  
Daniela Herrera ◽  
Andrew F. G. Quest
Keyword(s):  
Gastric Cancer ◽  
Helicobacter Pylori ◽  
Outer Membrane ◽  
Extracellular Vesicles ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Host Cells ◽  
Gastric Epithelium ◽  
Infected Cells ◽  
H Pylori

Extracellular vesicles (EVs) are cell-derived vesicles important in intercellular communication that play an essential role in host-pathogen interactions, spreading pathogen-derived as well as host-derived molecules during infection. Pathogens can induce changes in the composition of EVs derived from the infected cells and use them to manipulate their microenvironment and, for instance, modulate innate and adaptive inflammatory immune responses, both in a stimulatory or suppressive manner. Gastric cancer is one of the leading causes of cancer-related deaths worldwide and infection with Helicobacter pylori (H. pylori) is considered the main risk factor for developing this disease, which is characterized by a strong inflammatory component. EVs released by host cells infected with H. pylori contribute significantly to inflammation, and in doing so promote the development of disease. Additionally, H. pylori liberates vesicles, called outer membrane vesicles (H. pylori-OMVs), which contribute to atrophia and cell transformation in the gastric epithelium. In this review, the participation of both EVs from cells infected with H. pylori and H. pylori-OMVs associated with the development of gastric cancer will be discussed. By deciphering which functions of these external vesicles during H. pylori infection benefit the host or the pathogen, novel treatment strategies may become available to prevent disease.

scholarly journals “Limiting access to iron decreases infection of Atlantic salmon SHK-1 cells with bacterium Piscirickettsia salmonis”

2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Rodrigo Díaz ◽  
José Troncoso ◽  
Eva Jakob ◽  
Stanko Skugor
Keyword(s):  
Gene Expression ◽  
Iron Deficiency ◽  
Atlantic Salmon ◽  
Bacterial Load ◽  
Host Cells ◽  
Immune Gene ◽  
Immune Signaling ◽  
Immune Effector ◽  
Infected Cells ◽  
Piscirickettsia Salmonis

Abstract Background Vertebrate hosts limit the availability of iron to microbial pathogens in order to nutritionally starve the invaders. The impact of iron deficiency induced by the iron chelator deferoxamine mesylate (DFO) was investigated in Atlantic salmon SHK-1 cells infected with the facultative intracellular bacterium Piscirickettsia salmonis. Results Effects of the DFO treatment and P. salmonis on SHK-1 cells were gaged by assessing cytopathic effects, bacterial load and activity, and gene expression profiles of eight immune biomarkers at 4- and 7-days post infection (dpi) in the control group, groups receiving single treatments (DFO or P. salmonis) and their combination. The chelator appears to be well-tolerated by host cells, while it had a negative impact on the number of bacterial cells and associated cytotoxicity. DFO alone had minor effects on gene expression of SHK-1 cells, including an early activation of IL-1β at 4 dpi. In contrast to few moderate changes induced by single treatments (either infection or chelator), most genes had highest upregulation in the infected groups receiving DFO. The mildest induction of hepcidin-1 (antimicrobial peptide precursor and regulator of iron homeostasis) was observed in cells exposed to DFO alone, followed by P. salmonis infected cells while the addition of DFO to infected cells further increased the mRNA abundance of this gene. Transcripts encoding TNF-α (immune signaling) and iNOS (immune effector) showed sustained increase at both time points in this group while cathelicidin-1 (immune effector) and IL-8 (immune signaling) were upregulated at 7 dpi. The stimulation of protective gene responses seen in infected cultures supplemented with DFO coincided with the reduction of bacterial load and activity (judged by the expression of P. salmonis 16S rRNA), and damage to cultured host cells. Conclusion The absence of immune gene activation under normal iron conditions suggests modulation of host responses by P. salmonis. The negative effect of iron deficiency on bacteria likely allowed host cells to respond in a more protective manner to the infection, further decreasing its progression. Presented findings encourage in vivo exploration of iron chelators as a promising strategy against piscirickettsiosis.

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