Structure and host–actinomycete interactions in developing root nodules of Comptonia peregrina

1978 ◽  
Vol 56 (5) ◽  
pp. 502-531 ◽  
Author(s):  
William Newcomb ◽  
R. L. Peterson ◽  
Dale Callaham ◽  
John G. Torrey
Keyword(s):  
Host Cell ◽  
Root Nodules ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Host Cytoplasm ◽  
Transmission Electron ◽  
Microscopic Studies ◽  
Host Plasma Membrane ◽  
Soil Actinomycete

Correlated fluorescence, bright-field, transmission electron, and scanning electron microscopic studies were made on developing root nodules of Comptonia peregrina (L.) Coult. (Myricaceae) produced by a soil actinomycete which invades the root and establishes a symbiosis leading to fixation of atmospheric dinitrogen. After entering the host via a root hair infection, the hyphae of the endophyte perforate root cortical cells by local degradation of host cell walls and penetration of the host cytoplasm. The intracellular hyphae are always surrounded by host plasma membrane and a thick polysaccharide material termed the capsule. (For convenience, term intracellular refers to the endophyte being inside a Comptonia cell as distinguished from being intercellular, i.e.. between host cells, even though the former is actually extracellular as the endophyte is separated from the host cytoplasm by the host plasmalemma.) Numerous profiles of vesiculate rough endoplasmic reticulum (RER) occur near the growing hyphae. Although the capsule shows a positive Thiery reaction indicating its polysaccharide nature, the fibrillar contents of the RER do not, leaving uncertain whether the capsule results from polymers derived from the RER. Amyloplasts of the cortical cells lose their starch deposits during hyphal proliferation. The hyphae branch extensively in specific layers of the cortex, penetrating much of the host cytoplasm. At this stage, hyphal ends become swollen and form septate club-shaped vesicles within the periphery of the host cells. Lipid-like inclusions and Thiery-positive particles, possibly glycogen, are observed in the hyphae at this time. Associated with hyphal development is an increase in average host cell volume, although nuclear volume appears to remain constant. Concomitant with vesicle maturation, the mitochondrial population increases sharply, suggesting a possible relationship to vesicle function. The intimate interactions between host and endophyte during development of the symbiotic relationship are emphasized throughout.

A correlated light and electron microscopic study of symbiotic growth and differentiation in Pisum sativum root nodules

1976 ◽  
Vol 54 (18) ◽  
pp. 2163-2186 ◽  
Author(s):  
William Newcomb
Keyword(s):  
Electron Microscopy ◽  
Pisum Sativum ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Light And Electron Microscopy ◽  
Infection Thread ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Garden Pea ◽  
Host Cytoplasm

Plants of the garden pea Pisum sativum cv. Little Marvel were grown in aeroponic culture to facilitate observations and microscopy and were inoculated with Rhizobium leguminosarum, and nodules were sampled at five weekly intervals for light and electron microscopy. The invasion of the cortical cells by the infection thread, the structure of the infection thread, and the release of bacteria from it into the host cytoplasm and the subsequent symbiotic growth and differentiation of the two organisms are described in detail. The fine structure of the nodule is correlated with light microscopic observations and morphogenesis. A restriction in the use of the term 'vesicle' is proposed because of the current multiple and confusing usage of the term. The loss of the nodule meristem and its morphogenetic significance are discussed.

Ultrastructure of the haustorium of the peanut late leaf spot fungus Cercosporidium personatum

1989 ◽  
Vol 67 (4) ◽  
pp. 1198-1202 ◽  
Author(s):  
C. W. Mims ◽  
E. S. Luttrell ◽  
S. C. Alderman
Keyword(s):  
Host Cell ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cercosporidium Personatum ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Biotrophic Fungi ◽  
Leaf Spot Fungus ◽  
Extrahaustorial Matrix ◽  
Cell Protoplast

Data from scanning and transmission electron microscopic observations support light microscopic reports of the production of haustoria by the hemibiotrophic fungus Cercosporidium personatum. The trunklike base of the haustorium extended a short distance into the host cell where it formed three to five slightly thinner primary branches. These branches terminated in multiple, smaller, mostly opposite branch tips that gave the end of the haustorium a coralloid appearance. The morphology of this haustorium was distinctly different from the more extensively studied haustoria of various biotrophic fungi. Haustoria of C. personatum were observed in both living and dead host cells. In living cells an extrahaustorial matrix and extrahaustorial membrane separated the haustorium wall from the host cell protoplast. In dead cells the extrahaustorial membrane was absent. Haustoria in dead cells remained intact and appeared healthy.

Dynamics of arbuscule development and degeneration in onion, bean, and tomato with reference to vesicular–arbuscular mycorrhizae in grasses

1989 ◽  
Vol 67 (8) ◽  
pp. 2505-2513 ◽  
Author(s):  
Tom Alexander ◽  
Ronald Toth ◽  
Rose Meier ◽  
Hans Christian Weber
Keyword(s):  
Host Cell ◽  
Cell Volume ◽  
Arbuscular Mycorrhizae ◽  
Arbuscular Mycorrhizal Fungus ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Host Cytoplasm ◽  
Vesicular Arbuscular

A quantitative light and electron microscopic study of developing and degenerating arbuscules of the vesicular–arbuscular mycorrhizal fungus Glomus fasciculatum in onion, bean, and tomato was carried out to estimate three parameters during the colonization cycle and to compare these parameters with those in maize, oats, and wheat. The parameters are (i) Vv(a,c) the fraction of the host cell volume (c) occupied by the arbuscule (a); (ii) VV(cy,c) the fraction of the host cell volume occupied by host cytoplasm (cy); and (iii) SV(p,c) the ratio of the surface area of the host protoplast (p) to the volume of the whole host cell. Uninfected cortical cells contained 3.4% cytoplasm in onion, 3.1% in bean, and 3.5% in tomato. In cells with mature arbuscules, cytoplasm increased to 9.9% in onion, 14.2% in bean, and 13.6% in tomato. Cells with mature arbuscules contained 11.4% fungus in onion, 20.3% in bean, and 20.5% in tomato. The initial SV(p,c) in onion was 0.10 μm2/μm3 and in bean and tomato 0.11 μm2/μm3. This increased to 0.37 μm2/μm3 in onion, 0.82 μm2/μm3 in bean, and 0.54 μm2/μm3 in tomato by the time arbuscules were mature. Development of the arbuscule was estimated to take 2.5 days and occupied 33% of the total cycle time. The variation seen across host species can be used as an indicator of fungal and (or) host control for each parameter. Arbuscular parameters of onion were compared with those obtained by other authors.

Studies on the haustorium of Castilleja (Scrophulariaceae). II. The endophyte

1973 ◽  
Vol 51 (5) ◽  
pp. 923-931 ◽  
Author(s):  
David R. Dobbins ◽  
Job Kuijt
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Light Microscope ◽  
Cell Walls ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Host Cell Wall ◽  
Dark Staining ◽  
Host Tissues

The portion of the Castilleja haustorium within the host, the endophyte, was examined at the light-and electron-microscopic levels. The endophyte consists of a stalk of lipid-containing cells and digitate cells at its tip. Vessels run the length of the endophyte. There is a harmonious meshing between host cortical cells and those of the endophyte flank, suggesting that penetration is accomplished, in part, by cell dissolution. Crushing of cells also occurs during endophyte invasion as host phloem tissues are severely buckled and cell walls are greatly folded. Some features of digitate cells include dense cytoplasm, an abundance of endoplasmic reticulum, lateral walls that are thickened as well as those on the side adjacent to the host, and an ability to conform to the contours of host tissues. Often digitate cells are divided by very thin walls that are hardly visible under the light microscope. It is suggested that the thick cell walls may function as "free space" in the absorption of materials from the host. Within the endophyte, vessels differentiate and may contain either a finely granular, dark-staining material or a more coarsely granular, light-staining material. The particles of the latter have irregular shapes. Although granular materials are thus carried by some vessels, cells resembling the structurally intermediate "phloeotracheids" were not seen. Connections through the cell wall were not observed between parasite and host; however, within the endophyte plasmodesmata were highly branched and often contained median nodules. Transfer-like cells which have irregularly thickened walls occurred in the endophyte. Host tissues next to digitate cells appeared to be in a degraded state. Invaginations of the plasmalemma were common and small flattened vesicles were formed in some host cells from the disrupted tonoplast. In several instances, the cytoplasm had receded from the host cell wall and a "beaded" material was present in both vacuoles and large vesicles. The host cell wall at times had a very loose fibrillar appearance. Some host tracheids were occluded with a dense and dark-staining material. The xylem strands of the parasite are connected to the host xylem either by cell wall dissolution or by actual penetration of a digitate cell into a host xylary cell. The penetrating cell subsequently differentiates into a vessel member. A summary and general discussion are given to relate the two portions of the haustorium, the upper haustorium and the endophyte. The mass of new information gained in this study leads us to encourage the application of plastic embedding and sectioning techniques to further light-microscope studies on haustoria.

Light and electron microscopic studies on Myxobolus egyptica sp. nov. (Myxozoa, Myxosporea), infecting the hornlip mullet Oedalechilus labiosus from the Red Sea

2011 ◽  
Vol 56 (3) ◽  
Author(s):  
Abdel-Azeem Abdel-Baki
Keyword(s):  
Electron Microscopy ◽  
Red Sea ◽  
Direct Contact ◽  
Developmental Stages ◽  
Mature Spore ◽  
Host Cells ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Microscopic Studies ◽  
Gill Lamellae

AbstractA new myxosporean, Myxobolus egyptica sp. nov., was described from the gills of the hornlip mullet Oedalechilus labiosus, collected from the Red Sea at Al-Quseir city, Egypt. The prevalence of infection was 12/72 (16.66%). Myxobolus egyptica was identified on the basis of spore morphometry, histology and transmission electron microscopy. It was distinguished from all previously reported Myxobolus spp. by its shape, dimensions of the mature spore 10.0 ± 0.6 (9.5–10.5) μm in length, 8.5 ± 0.4 (8.0–9.0) μm in width and 8.7 ± 0.5 (8.4–9.2) μm in thickness, polar capsules, locality and host. The parasite formed intrafilamental cyst-like plasmodia. These plasmodia caused curling and atrophy of the gill lamellae. The ultrastructural analysis revealed a double-unit plasmodial membrane which was in direct contact with the host cells and had numerous vesicles. Some mitochondria were found below this membrane. The disporic pansporoblast was earliest recognizable stage of sporogenesis. Advanced developmental stages of spores and mature spores were reported.

Radial mass analysis of unstained STEM images of molluscan hemocyanins

1990 ◽  
Vol 48 (3) ◽  
pp. 810-811
Author(s):  
M.G. Hamilton ◽  
T.T. Herskovits ◽  
J.S. Wall
Keyword(s):  
Image Analysis ◽  
Hollow Cylinder ◽  
Electron Micrographs ◽  
Side View ◽  
Mass Analysis ◽  
Mass Measurements ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Microscopic Studies

The hemocyanins of molluscs are aggregates of a cylindrical decameric subparticle that assembles into di-, tri-, tetra-, penta-, and larger multi-decameric particles with masses that are multiples of the 4.4 Md decamer. Electron micrographs of these hemocyanins typically show the particles with two profiles: circular representing the cylinder viewed from the end and rectangular representing the side-view of the hollow cylinder.The model proposed by Mellema and Klug from image analysis of a didecameric hemocyanin with the two decamers facing one another with collar (closed) ends outward fits the appearance of side-views of the negatively-stained cylinders. These authors also suggested that there might be caps at the ends. In one of a series of transmission electron microscopic studies of molluscan hemocyanins, Siezen and Van Bruggen supported the Mellema-Klug model, but stated that they had never observed a cap component. With STEM we have tested the end cap hypothesis by direct mass measurements across the end-views of unstained particles.

A light and electron microscope study of the fungal endophytes in the sporophyte and gametophyte of Lycopodium cernuum with observations on the gametophyte–sporophyte junction

1992 ◽  
Vol 70 (1) ◽  
pp. 58-72 ◽  
Author(s):  
Jeffrey G. Duckett ◽  
Roberto Ligrone
Keyword(s):  
Root Nodules ◽  
Fungal Endophytes ◽  
Fungal Endophyte ◽  
Peninsular Malaysia ◽  
Epidermal Cells ◽  
Host Cells ◽  
Wall Material ◽  
Intercellular Spaces ◽  
Host Cytoplasm ◽  
Fungal Associations

The ventral epidermal cells of the photosynthetic, surface-living gametophytes of Lycopodium cernuum, collected from moist shaded banks in Peninsular Malaysia, contain an aseptate fungus. In some cells the hyphae are thick walled and form coils encapsulated by a thin layer of host wall material. In others the fungus is thin walled and shows limited differentiation into larger trunk hyphae and arbuscules. The adjacent host cytoplasm, separated from the fungus by a granular interfacial matrix, contains numerous chloroplasts, mitochondria, and microtubules. The hyphae contact the substratum via the ventral walls of the epidermal cells and the rhizoids are free from infection. In the protocorm and root nodules, aseptate hyphae initially colonize mucilage-filled schizogenous intercellular spaces. Subsequent invasion of the host cells is associated with the development of massive overgrowths of host wall material. The fungal associations in L. cernuum share a mixture of attributes otherwise found in different angiosperm mycorrhizae and in mycotrophic relationships in liverworts. Wall ingrowths are present in both the gametophyte and sporophyte cells in the placenta of L. cernuum. The very limited development of the placenta, compared with L. appressum, certain bryophytes and ferns, the diminutive size, and early senescence of the gametophytes of L. cernuum are all linked to the presence of the protocorm. This massive absorptive organ, homologous to a foot, in terms of its position in sporophyte ontogeny, but external to the parent gametophyte, derives its nutrition partly from photosynthesis and partly from its fungal endophyte. Key words: chloroplasts, Lycopodium, mycorrhiza, pteridophytes, root nodules, symbiosis, transfer cells.

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