A comparative ultrastructural study of endophytic basidiomycetes in the parasitic achlorophyllous hepatic Cryptothallus mirabilis and the closely allied photosynthetic species Aneura pinguis (Metzgeriales)

1993 ◽  
Vol 71 (5) ◽  
pp. 666-679 ◽  
Author(s):  
Roberto Ligrone ◽  
Keith Pocock ◽  
Jeffrey G. Duckett
Keyword(s):  
Ultrastructural Study ◽  
Starch Content ◽  
Sand Dunes ◽  
Ectomycorrhizal Fungus ◽  
Host Cytoplasm ◽  
Amyloid Deposits ◽  
Host Plasma Membrane ◽  
Thin Walled ◽  
Fungal Associations ◽  
Hyphal Contact

This ultrastructural study of two closely related liverworts with contrasting modes of nutrition reveals very similar interactions with endophytic dikaryotic basidiomycetes. In both hepatics, collected from a variety of sites, the fungus is confined to specific regions of the gametophyte thallus, and hyphal contact with the substratum is via the rhizoids. The colonization cycle comprises a growth phase when the fungus forms large intracellular coils, host cytoplasm proliferates and the starch content of the plastids decreases, followed by senescence when the hyphae die back and aggregate into large masses. Repeated colonization cycles are frequent. Young hyphae contain abundant glycogen and sometimes amyloid deposits in Cryptothallus. In terms of dolipore substructure, hyphal dimensions, highly characteristic multilayered walls, absence of clamp connections, and the mode of hyphal degeneration, the endophyte in Cryptothallus is virtually identical to that in Aneura from alpine sites but very different from the fungus in Aneura from sand dunes and a chalk pit. It is suggested that Cryptothallus evolved from an Aneura-like ancestor through association with a fungal saprophyte of waterlogged peaty soils. Differences in dolipore morphology in the ectomycorrhizal fungus of Betula roots growing in association with Cryptothallus indicate that these two hosts do not share the same fungus. Remarkable similarities between the fungal associations in Cryptothallus and Aneura and orchidaceous mycorrhizae include the same colonization cycle, absence of polyphosphate granules, and separation of the host plasma membrane from thin-walled, exclusively intracellular hyphae by a prominent interfacial matrix. Key words: basidiomycetes, dolipores, liverworts, mycorrhiza, symbiosis, ultrastructure.

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.

scholarly journals Deciphering the mode of action and host recognition of bacterial type III effectors

2010 ◽  
Vol 37 (10) ◽  
pp. 926 ◽  
Author(s):  
Selena Gimenez-Ibanez ◽  
Dagmar R. Hann ◽  
John P. Rathjen
Keyword(s):  
Mode Of Action ◽  
Pathogenic Bacteria ◽  
Plant Immunity ◽  
Plant Defence ◽  
Host Recognition ◽  
Type Iii Effectors ◽  
Host Cytoplasm ◽  
Host Plasma Membrane ◽  
Defence Responses ◽  
Bacterial Effectors

Plant pathogenic bacteria adhere to cell walls and remain external to the cell throughout the pathogenic lifecycle, where they elicit host immunity through host plasma membrane localised receptors. To be successful pathogens, bacteria must suppress these defence responses, which they do by secreting a suite of virulence effector molecules into the host cytoplasm. However, effectors themselves can act as elicitors after perception by intracellular host immune receptors, thus, re-activating plant immunity. Bacterial effectors generally target host molecules through specific molecular activities to defeat plant defence responses. Although effectors can be used as tools to elucidate components of plant immunity, only a handful of these molecular targets are known and much remains to be learnt about effector strategies for bacterial pathogenicity. This review highlights recent advances in our understanding of the mode of action of bacterial effectors, which in the future will lead to improvements in agriculture.

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.

The fine structure of Leucocytozoon simondi. II. Megaloschizogony

1970 ◽  
Vol 48 (3) ◽  
pp. 417-421 ◽  
Author(s):  
Sherwin S. Desser
Keyword(s):  
Nuclear Division ◽  
Phagocytic Cells ◽  
Polar Ring ◽  
Host Cytoplasm ◽  
Stage Of Development ◽  
Multiple Fission ◽  
Host Plasma Membrane ◽  
Infected Cells ◽  
The Difference ◽  
Further Development

Incompletely divided cytomeres released from hepatic schizonts of L. simondi undergo prolific development in phagocytic cells of the host which become grossly hypertrophied. These infected cells together with the parasites within are termed megaloschizonts. Young megaloschizonts contain numerous round cytomeres bounded by a five-layered envelope. With further development the cytomeres expand and become invaginated. Microtubular spindles occur in dividing parasite nuclei at this stage of development. Thickenings form on the single membrane bounding the newly formed cytomeric surfaces. Electron-dense paired organelles develop adjacent to the thickenings which become the polar rings of merozoites. Abundant granular endoplasmic reticulum and numerous mitochondria with vesicular cristae are seen in the cytoplasm of invaginated cytomeres. Nuclear division by multiple fission and further cytoplasmic fragmentation continue until uninucleate merozoites are formed. Male and female merozoites can be distinguished by the difference in the density of their cytoplasm and each contains a mitochondrion and paired organelles with the associated polar ring. The megaloschizont is surrounded by a capsule whose irregular inner surface is lined by the host plasma membrane. Outside this lies a thick filamentous zone from which numerous vesicles are pinched off and are seen within the hypertrophied host cytoplasm. A fibrous layer bounds the outer surface of the megaloschizonts.

An ultrastructural study on the development of silicified tissues in the lemma of Phalaris canariensis L

1984 ◽  
Vol 222 (1229) ◽  
pp. 413-425 ◽  
Keyword(s):  
Thin Layer ◽  
Ultrastructural Study ◽  
Outer Edge ◽  
Silica Deposition ◽  
Thin Walls ◽  
Tangential Wall ◽  
Siliceous Material ◽  
Thin Walled ◽  
Thickened Wall ◽  
Phalaris Canariensis

Silica deposition in the lemma of Phalaris canariensis L. takes place after panicle emergence in both the outer epidermal long cells and the macrohairs covering the outer epidermis. Before panicle emergence, the macrohairs have large vacuoles and thin walls. The first indication of silica deposition occurs at emergence when a thin layer of electron-opaque siliceous material appears at the outer edge of the wall. The hair wall becomes considerably thickened during the two weeks after emergence, and silica is eventually deposited in the whole of this thickened wall. At maturity the hairs are highly silicified, and the cytoplasm breaks down to leave a small central lumen. The outer epidermal cells are relatively thin-walled one week before emergence. By emergence, however, the inner tangential wall becomes greatly thickened, occupying most of the cell volume. During the week following emergence granular siliceous material is deposited in the wall surrounding the pre-existing lumen. This deposition is continued in the same area, until by maturity a silica aggregate is formed. The results are compared with those of previous studies, and discussed in relation to silica deposition mechanisms.

scholarly journals A remorin protein interacts with symbiotic receptors and regulates bacterial infection

2010 ◽  
Vol 107 (5) ◽  
pp. 2343-2348 ◽  
Author(s):  
Benoit Lefebvre ◽  
Ton Timmers ◽  
Malick Mbengue ◽  
Sandra Moreau ◽  
Christine Hervé ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Root Nodule ◽  
Biotic Interactions ◽  
Scaffolding Protein ◽  
Host Cytoplasm ◽  
Bacterial Signaling ◽  
Core Set ◽  
Cellular Signal ◽  
Host Plasma Membrane ◽  
Nodule Symbiosis

Remorin proteins have been hypothesized to play important roles during cellular signal transduction processes. Induction of some members of this multigene family has been reported during biotic interactions. However, no roles during host-bacteria interactions have been assigned to remorin proteins until now. We used root nodule symbiosis between Medicago truncatula and Sinorhizobium meliloti to study the roles of a remorin that is specifically induced during nodulation. Here we show that this oligomeric remorin protein attaches to the host plasma membrane surrounding the bacteria and controls infection and release of rhizobia into the host cytoplasm. It interacts with the core set of symbiotic receptors that are essential for perception of bacterial signaling molecules, and thus might represent a plant-specific scaffolding protein.

An ultrastructural study of the marine diatom Licmophora hyalina and its parasite Ectrogella perforans. II. Development of the fungus in its host

1980 ◽  
Vol 58 (24) ◽  
pp. 2557-2574 ◽  
Author(s):  
Chandralata Raghu Kumar
Keyword(s):  
Plasma Membrane ◽  
Host Cell ◽  
Ultrastructural Study ◽  
Typical Feature ◽  
Golgi Body ◽  
Marine Diatom ◽  
Host Plasma Membrane ◽  
Cytoplasmic Bridges ◽  
Dense Vesicles

The thallus of the fungus Ectrogella perforans Petersen inside its host, the diatom Licmophora hyalina Agardh, is surrounded initially by two electron-dense membranes, of which the outer one is the invaginated host plasma membrane and the inner one, the fungal plasma membrane. Later, new membranes are added between these two membranes and the fungal envelope consists of four to six membranes. When the fungal thallus is mature, all the membranes except the fungal plasmalemma break down and it secretes an amorphous wall around itself. This coincides with the breakdown of host organelles followed by death of the host cell. Zoosporogenesis begins after the sporangium becomes multinucleate. A peculiar "multitubular body" is always observed in the multinucleate sporangium. A typical feature of the multinucleate sporangium prior to zoosporogenesis is the presence of a ring of tubular cisternae around the nuclei, electron-dense vesicles, and granular vesicles.The tubular cisternae found around the nuclei move away and act as cleavage cisternae. The cleavage cisternae run perpendicular to the sporangial plasma membrane and delimit the sporangial mass into uninucleate units at the time of zoosporogenesis. Simultaneously, vesicles are pinched off from the Golgi body which act as cleavage vesicles. These cleavage vesicles fuse with each other and form cleavage furrows. The cleavage cisternae fuse with the plasma membrane outside and with the cleavage vesicles inside and thus deepen the cleavage furrows. The sporangial mass is thus divided into zoospore units and the units are connected only by narrow cytoplasmic bridges. The zoospores have their flagella developed already. The structure of primary zoospores, encysted primary zoospores, and encysted secondary zoospores is described here.

Resistant structures in the entomogenous hyphomycete, Nomuraea rileyi: an ultrastructural study

1982 ◽  
Vol 60 (8) ◽  
pp. 1569-1576 ◽  
Author(s):  
J. C. Pendland
Keyword(s):  
Metabolic Activity ◽  
Ultrastructural Study ◽  
Environmental Conditions ◽  
Anticarsia Gemmatalis ◽  
Nomuraea Rileyi ◽  
Larval Tissue ◽  
Low Humidity ◽  
Thin Walled ◽  
Adverse Environmental Conditions

Three types of resistant or resting structures were found to occur in the entomogenous hyphomycete Nomuraea rileyi when unfavorable conditions (e.g., low humidity) inhibited conidiogenesis. Intrahyphal hyphae, which are regenerative hyphae within deteriorating parent hyphae, were observed in both the disintegrating larval tissue of Anticarsia gemmatalis and the extracuticular fungal mat. Thick-walled hyphae and chlamydospores were found in the external mat, and lipid-filled, thin-walled hyphae were prevalent in the larval tissue. Chlamydospores formed as apical swellings of thick-walled hyphae. Resistant structures remained viable for at least 12 weeks. Upon rehydration, cells resumed metabolic activity and after several days, conidiophores and conidia were produced. Verification of the existence of such structures provides an explanation as to how the fungus survives in the field under adverse environmental conditions.

Immunocytochemical Localization of Amyloid Protein AA in the “Dense Fibrillar Inclusions” of the Reticuloendothelical Cells

1977 ◽  
Vol 35 ◽  
pp. 438-439
Author(s):  
T. Shirahama ◽  
M. Skinner ◽  
A.S. Cohen
Keyword(s):  
Amyloid Fibril ◽  
Close Association ◽  
Gel Filtration ◽  
Fibril Formation ◽  
Amyloid Protein ◽  
Electron Microscopic ◽  
Amyloid Deposits ◽  
Amyloid Fibril Formation ◽  
Electron Microscopic Technique ◽  
Lysosomal System

A1thought the mechanisms of amyloidogenesis have not been entirely clarified, proteolysis of the parent proteins may be one of the important steps in the amyloid fibril formation. Recently, we reported that "dense fibrillar inclusions" (DFI), which had the characteristics of lysosomes and contained organized fibrillar profiles as well, were observed in the reticuloendothelial cells in close association with the foci of new amyloid deposits. We considered the findings as evidence for the involvement of lysosomal system in amyloid fibril formation (l). In the present study, we attempted to determine the identity of the contents of the DFI by the use of antisera against the amyloid protein (AA) and an immuno-electron microscopic technique.Amyloidosis was induced in CBA/J mice by daily injections of casein (l). AA was isolated from amyloid-laden spleens by gel filtration and antibody to it was produced in rabbits (2). For immunocytochemistry, the unlabeled antibody enzyme method (3) was employed.

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