Septal Swelling Research Articles

ULTRASTRUCTURE OF THE METABASIDIUM OF AURICULARIA FUSCOSUCCINEA

Maturation of the metabasidium of Auricularia fuscosuccinea was followed with light microscopy and transmission electron microscopy. The basidium was divided into four compartments by septa which developed centripetally as in hyphae. Each septum formed a septal pore apparatus with imperforate pore caps. A band of electron‐dense material was situated in the middle of the septal pore. There was a large increase in the volume of cytoplasm, excluding vacuoles, in each compartment during sterigmal outgrowth. Compartments were evacuated in basipetal sequence and vacuole enlargement began at the base of a compartment only when sterigmal formation was well advanced. The septal pore apparatus was intact until late in maturation of a compartment when septal swellings occluded the pore. The metabasidial wall was differentiated from those of other hymenial and subhymenial cells. The pattern of basidial maturation is compared with that in other phragmobasidiate and holobasidiate fungi. Use of the septal pore apparatus for phylogenetic and taxonomic purposes is discussed, as is the concept of primary and adventitious septa.

The fine structure of septal pore apparatus in the lamellae of Pholiota terrestris

The lamellae of Pholiota terrestris, when viewed in thin sections cut perpendicular to the hymenial surface, consist of a hymenial layer of basidia and scattered cystidia, an interwoven subhymenium, and a trama. The inner trama is composed of a zone of relatively large, vacuolated hyphal elements, whereas the outer trama consists of smaller hyphal elements with relatively dense cytoplasmic contents. The septal pore apparatus throughout the lamellae are similar to those described in most other Homobasidiomycetes and saprobic Heterobasidiomycetes. In the center of the septal pore there is a narrow electron-dense zone that intersects the pore canal. In some septal pores similar electron-dense zones occur near one or both orifices. The septal cap consists of three membranes, of which the two defining membranes appear clearly tripartite in cross section. The pores in the septal cap are arranged hexagonally and are 70–105 nm in diameter. The proximal septal caps of the subbasidial septa and those in the subhymenium develop an electron-dense, granular outer cap that is usually delimited externally by endoplasmic reticulum or, less often, by the tonoplast of an adjacent vacuole. The septal pores of the subbasidial septa become plugged by the expanded septal swelling following basidiospore discharge. The septal pore apparatus in the trama are not associated with outer caps; however, many septal pores in the trama become occluded with electron-dense plugs near both orifices. The observations of the septal pore apparatus in the lamellae of P. terrestris are compared with studies of other Homobasidiomycetes and saprobic Heterobasidiomycetes.

SEPTUM STRUCTURE IN SPINIGER MEINECKELLUS

The structure of the hyphal septum in Spiniger meineckellus is of the dolipore type and is basically like that reported for other Holobasidiomycetes. The septum forms centripetally across the hypha and is accompanied by invagination of the plasmalemma. That portion of the septum surrounding the single central pore enlarges to form a septal swelling. The laminate central region of the septum wall extends through the septal swelling to the edge of the pore. On both sides of the septum there is a convex, laminate, electron‐dense, perforate septal cap that covers the septal swelling and pore. The septal cap is sometimes continuous with endoplasmic reticulum that extends along the septum. Two electron‐opaque rings surround the septal pore and rest on the shoulders of the septal swelling. Small, fine, dark filaments extend from these rings to narrow electron‐dense bands inside the pore.

Septum Structure in Spiniger Meineckellus

The structure of the hyphal septum in Spiniger meineckellus is of the dolipore type and is basically like that reported for other Holobasidiomycetes. The septum forms centripetally across the hypha and is accompanied by invagination of the plasmalemma. That portion of the septum surrounding the single central pore enlarges to form a septal swelling. The laminate central region of the septum wall extends through the septal swelling to the edge of the pore. On both sides of the septum there is a convex, laminate, electron-dense, perforate septal cap that covers the septal swelling and pore. The septal cap is sometimes continuous with endoplasmic reticulum that extends along the septum. Two electron-opaque rings surround the septal pore and rest on the shoulders of the septal swelling. Small, fine, dark filaments extend from these rings to narrow electron-dense bands inside the pore.

Ultrastructural localization of polysaccharides in the wall and septum of the basidiomycete Schizophyllum commune

The location of polysaccharides in the wall and the septum of monokaryotic mycelium of Schizophyllum commune was determined using thin sections and shadowed preparations. Extraction procedures and staining, to detect periodate-sensitive polysaccharides, were used to localize wall polymers that had previously been identified by chemical analysis. Apart from a water-soluble β-1,3-β-1,6-linked glucan (mucilage) that surrounds the hyphae, the lateral wall has an outer layer consisting of relatively pure α-1,3-glucan (S-glucan). The inner layer consists of R-glucan, an alkali-insoluble polymer containing a large proportion of β-1,3-β-1,6-linked glucan, in which chitin microfibrils are embedded. Adjacent to the plasmalemma, these microfibrils are clearly visible but at the interface with the S-glucan layer they are completely embedded in R-glucan. The septum has a central plate mainly composed of randomly oriented chitin microfibrils, except at the septal swelling, where they are arranged circularly around the septal pore. The central plate is covered at both sides by a layer of R-glucan in which chitin microfibrils are embedded. R-Glucan and chitin only occur in the central part of the septal swelling. The main body of this structure is made up of a mucilaginous substance that may be similar to the water-soluble β-1,3-β-1,6-glucan that surrounds the hyphae. S-Glucan appears to be absent from the septum. At the junction of lateral wall and septum, chitin and R-glucan appear to be resistant to enzymatic treatment, which dissolves most of the other wall material, resulting in the appearance of septal rings.

Septal involvement in nuclear migration in Schizophyllum commune.

A system, utilizing thedwarf andpuff morphological mutants ofSchizophyllum commune, was devised to select specific hyphal segments that were in different stages of septal dissolution and nuclear migration. These stages were observed with the electron microscope. Direct evidence of the dissolution of complex septal during nuclear migration was obtained. Initially there was a disruption of the septal swelling, followed by erosion of the remaining cross wall. Complex septa were therepy converted to simple septa through which nuclei migrated. These septa were covered with secondary cell wall material. Following nuclear migration only vacuolate hyphae with remnant membrane structures remained. Occasionally, intact hyphae were observed within these vacuolate hyphae.

Studies on the vegetative hypha of Corticium areolatum

The structure of the hyphae of Corticium areolatum was examined by phase-contrast and electron microscopy. The hyphae lack clamp connexions and although the cells are mainly binucleate, multinucleate cells occur scattered throughout the mycelium. The hyphal wall and the cross wall are lamellate and a deposition of additional lamellae takes place at the junction of cross and lateral walls. A septal pore swelling is associated with and structurally different from the cross-wall. On each side of the septal swelling is a septal pore cap, in continuity with the endoplasmic reticulum. Associated with some of the cross-walls are paramural bodies, elaborate invaginations of the plasmalemma.

Efizymic Degradation of Septa in Hyphal Wall Preparations from a Monokaryon and a Dikaryon of Schizophyllum commune

SUMMARY: Hyphal wall preparations of Schizophyllum commune were treated with enzymes and the dissolution of wall components and the degradation of septa were simultaneously recorded. The breakdown of the alkali-insoluble R-glucan (β-1,3, β-1,6-glucan) by R-glucanase was not influenced by the presence of chitinase but the breakdown of chitin by chitinase was stimulated by R-glucanase. The combination of R-glucanase and chitinase also had a synergistic effect on crosswall degradation. This indicates that the crosswalls contain both chitin and R-glucan, the chitin probably embedded in R-glucan. S-glucan (α-1,3-glucan), a prominent component of the lateral walls, is apparently absent from the crosswalls. The septal swellings consist of material that is alkali soluble but different from S-glucan. Crosswalls in hyphal wall fragments from a dikaryon were much more resistant to enzymic dissolution than those in hyphal wall fragments from a monokaryon. Such a difference could not be noted in the dissolution of wall components. The results are discussed with regard to their significance for sexual morphogenesis in Schizophyllum commune

Fine structure of the septal pore apparatus in Polyporus tomentosus, Poria latemarginata, and Rhizoctonia solani

The septal pore apparatus was studied in Poria latemarginata, Polyporus tomentosus, and Rhizoctonia solani. Fixation by potassium permanganate was compared with fixation by glutaraldehyde – osmium tetroxide. Potassium permanganate reduced the size of the septal swelling about 50% and destroyed much of the internal integrity of the septal swelling. In glutaraldehyde – osmium tetroxide fixed material, a fibrillar network extended from the cross wall throughout the septal swelling. Except for this network, the septal swelling was electron transparent and similar in appearance to a vacuole. A rim of electronopaque material, attached to the septal swelling, surrounded the pore mouth in Polyporus tomentosus and Rhizoctonia solani.

SEPTAL PORES IN THE HETEROBASIDIOMYCETIDAE, PUCCINIA GRAMINIS AND P. RECONDITA

The septal pores in uredial mycelium of Puccinia graminis and P. recondita lack the septal swelling and septal pore cap (dolipore‐parenthosome configuration) typically associated with the pores of previously investigated Homobasidiomycetidae and the Tremellales among the Heterobasidiomycetidae. The pores in young hyphae of these two species of Puccinia are characterized by the presence of a cytoplasmic matrix which apparently occludes the pore and acts as a plug, thus preventing the migration of organelles from cell to cell. Large vesicles are typically present at the periphery of the pore matrix and the matrix may be very incompletely bounded by a membrane. Nuclei and other cytoplasmic structures migrate from cell to cell through an opening in the septum lateral to the pore. The available evidence indicates that this peripheral gap in the septum results from a breakdown of a portion of an initially complete septum rather than from incomplete septum formation. In addition to the centripetally formed septa, the hyphae of P. graminis and P. recondita are further compartmentalized by shallow infoldings of the lateral wall and limited unilateral septum formation. There is apparent free passage of cellular material between adjacent compartments.

Septal Pores in the Heterobasidiomycetidae, Puccinia graminis and P. recondita

The septal pores in uredial mycelium of Puccinia graminis and P. recondita lack the septal swelling and septal pore cap (dolipore-parenthosome configuration) typically associated with the pores of previously investigated Homobasidiomycetidae and the Tremellales among the Heterobasidiomycetidae. The pores in young hyphae of these two species of Puccinia are characterized by the presence of a cytoplasmic matrix which apparently occludes the pore and acts as a plug, thus preventing the migration of organelles from cell to cell. Large vesicles are typically present at the periphery of the pore matrix and the matrix may be very incompletely bounded by a membrane. Nuclei and other cytoplasmic structures migrate from cell to cell through an opening in the septum lateral to the pore. The available evidence indicates that this peripheral gap in the septum results from a breakdown of a portion of an initially complete septum rather than from incomplete septum formation. In addition to the centripetally formed septa, the hyphae of P. graminis and P. recondita are further compartmentalized by shallow infoldings of the lateral wall and limited unilateral septum formation. There is apparent free passage of cellular material between adjacent compartments.

FINE STRUCTURE OF THE AGARICUS CARPOPHORE

The fine structure in the carpophore of the mushroom, Agaricus campestris, was studied with the electron microscope. The stipe consists of two types of cells (i) fundamental and (ii) long and thread-like. The pileus contains only the first type. The tramal cells of the gills are more elongated than broad, regularly arranged, and rich in cytoplasmic contents. The cross wall of the hyphal cells shows a conspicuous pore apparatus with dark septal swellings encased in the plasma membrane. The nuclear membranes are differentiated early during nuclear division and are highly alveolated around the interphase nucleus. In the maturing basidium, the mitochondria increase in number by division of pre-existing ones, and thus become small with few cristae. Numerous vacuoles appear in the upper portion of the basidium. Oil globules are also produced in the mature basidium but were not observed during the early stages of development of the basidium or in any other part of the carpophore. The young basidium has food reserve which is granular in nature. The basidiospore contains numerous large oil globules, few mitochondria, scanty endoplasmic reticulum, and a wall of three well-defined layers.

The Basidia of Exidia nucleata. I. Ultrastructure

SUMMARYThe nucleus of the basidium of Exidia nucleata is surrounded by an alveolate nuclear envelope. The mitochondria within the basidia have plate-like cristae and are morphologically similar to those reported from other fungi. Also present within the basidia are vacuoles similar to those described in plant cells, oil globules, and two types of unidentified cytoplasmic inclusions. The ectoplast is visible as a single, electron-dense line in good thin sections of KMnO4-fixed material.The endoplasmic reticulum is thought to form an extensive, flattened network throughout the cytoplasmic ground substance of the basidium. Continuities between the nuclear envelope and the endoplasmic reticulum and between systems of parallel lamellae and the endoplasmic reticulum are described and illustrated; however, continuities purported to occur in other fungi between the endoplasmic reticulum and other membrane systems and organelles were not observed.Systems of parallel, double lamellae were noted frequently. Although these systems exhibit certain morphological features of the Golgi apparatus as described in plant and animal cells, sufficient evidence is not available to support a conclusion on their nature and function.The sub-basidial septa have a structure similar to that reported for the septa of Polyporus versicolor and Pellicularia filamentosa. The pore within the septal pore apparatus becomes occluded, following the collapse of the basidium, by the formation of secondary wall material within the clamp-conection or within the fertile hyphal segment. The septal swellings of occluded pores disintegrate, whereas the cross walls remain intact.