Septal Pore Apparatus Research Articles

Ultrastructure of hyphal cells of Trichophyton tonsurans.

Background and Purpose: Trichophyton tonsurans is a widely distributed anthropophilic dermatophyte causing different diseases of skin. In the literature limited data are available about the morphogenesis of vegetative mycelium of T. tonsurans and related anthropophilic dermatophytes. The aim of present study was to describe ultrastructural patterns of development, cellular organellography and septal pore apparatus structure of in vitro growing vegetative mycelium of T. tonsurans.Materials and Methods: Trichophyton tonsurans strain RCPFF 214/898 was grown on solid Czapek’s Agar (CzA) at 28ºС. For investigation of colonies morphology we used methods of light-, scanning and transmission electron microscopy (SEM and TEM).Results:Differences in morphogenesis of aerial and substrate hyphae were revealed. Mitochondrial reticulum and fibrosinous bodies were shown in T. tonsurans for the first time. The septal pore apparatus in hyphal cells of was comprised Woronin bodies and septal pore plugs. Woronin bodies (0.18 µm), located with 1‒4 near the pore, were spherical, membrane-bound, and had a homogeneous, electron-dense content. The cells of aerial and submerged hyphal cells of T. tonsurans contain two nuclei.Conclusion:Mature cells of substrate hyphae appeared more active than comparable cells in the aerial mycelium. During the maturation process, the differences in number and morphology of mitochondria, number of vacuoles, and in the synthesis of different types of storage substances were revealed. Presence of “mitochondrial reticulum” and variable types of storage substances in submerged hyphal cells suggested higher levels of metabolic activity compared to aerial mycelium.

Structural character evolution in Pucciniomycotina: mitosis, septa, and hyphal branch initiation in two Helicogloea species

ABSTRACTEarly diverging taxa of Ascomycota and Basidiomycota share similarities in subcellular characters of the spindle pole body (SPB), nuclear division, and septal pore apparatus, but our understanding of character evolution is incomplete because of the limited number of structural studies within the earliest diverging subphyla of Dikarya, Taphrinomycotina and Pucciniomycotina. Two species of Helicogloea (Atractiellomycetes) were analyzed for these characters and provide data on SPB and nuclear division for an additional class of Pucciniomycotina. A detailed analysis of septal pore apparatus for the Helicogloea species permits comparisons with those of other Pucciniomycotina and Ascomycota. The endogenous origin of hyphal branches is shown to occur in a third class of Pucciniomycotina. The full set of characters supports a close relationship between Atractiellomycetes and Pucciniomycetes.

Cultural and cytological characterization of Dacryopinax primogenitus, a new species in the Dacrymycetes with a fully sequenced genome

A Dacryopinax species that was cultured in Costa Rica and fruited in the laboratory provided DNA for the first sequenced genome for the Dacrymycetes. Here we characterize the isolate morphologically and cytologically and name it D. primogenitus. Molecular sequences from the nuclear large subunit gene and internal transcribed spacer indicated that it is closely related to the South American D. indacocheae with which it agrees structurally. Both species form conidia on the basidiocarp, and D. primogenitus also forms them on the mycelium. Unlike previous reports for the Dacrymycetales postmeiotic nuclear division results in uninucleate basidiospores and six residual nuclei in the basidium after basidiospore discharge. Ultrastructural analysis shows the characteristic septal-pore apparatus for the class and endogenous origin of the epibasidia/sterigmata, which may be a common occurrence in Dacrymycetes and the early diverging orders of its sister class, the Agaricomycetes.

Intra- and interspecific diversity of ultrastructural markers in Scedosporium

Ultrastructural features of conidia, lateral walls of aerial and submerged hyphal cells, and of septal pore apparatus of Scedosporium apiospermum, S. boydii, Pseudallescheria angusta and Scedosporium aurantiacum were studied. Submerged hyphal cells possessed a thick extracellular matrix. Crystalline satellites accessory to the septal pore apparatus were revealed. Fundamental ultrastructural features appeared to be heterogeneous at low taxonomic levels. The closely interrelated members of the S. apiospermum complex showed quantitative ultrastructural variability, but the unambiguously different species S. aurantiacum deviated qualitatively by markers of conidial wall structure, Woronin bodies morphology and presence/absence of crystalline satellites of the septal pore apparatus.

The genome of the xerotolerant mold Wallemia sebi reveals adaptations to osmotic stress and suggests cryptic sexual reproduction

Wallemia (Wallemiales, Wallemiomycetes) is a genus of xerophilic Fungi of uncertain phylogenetic position within Basidiomycota. Most commonly found as food contaminants, species of Wallemia have also been isolated from hypersaline environments. The ability to tolerate environments with reduced water activity is rare in Basidiomycota. We sequenced the genome of W. sebi in order to understand its adaptations for surviving in osmotically challenging environments, and we performed phylogenomic and ultrastructural analyses to address its systematic placement and reproductive biology. W. sebi has a compact genome (9.8Mb), with few repeats and the largest fraction of genes with functional domains compared with other Basidiomycota. We applied several approaches to searching for osmotic stress-related proteins. In silico analyses identified 93 putative osmotic stress proteins; homology searches showed the HOG (High Osmolarity Glycerol) pathway to be mostly conserved. Despite the seemingly reduced genome, several gene family expansions and a high number of transporters (549) were found that also provide clues to the ability of W. sebi to colonize harsh environments. Phylogenetic analyses of a 71-protein dataset support the position of Wallemia as the earliest diverging lineage of Agaricomycotina, which is confirmed by septal pore ultrastructure that shows the septal pore apparatus as a variant of the Tremella-type. Mating type gene homologs were identified although we found no evidence of meiosis during conidiogenesis, suggesting there may be aspects of the life cycle of W. sebi that remain cryptic.

Septal pore apparatus and nuclear division of Auriscalpium vulgare

Ultrastructure of the septal pore apparatus and nuclear division of Auriscalpium vulgare (Russulales) was examined with freeze substitution and is presented for inclusion in the AFTOL Structural and Biochemical Database (http://aftol.umn.edu). Previously unreported septal characters for the Russulales (Agaricomycotina) were observed: Septa of the hymenophore had bell-shaped perforated septal pore caps that may extend along the septum and a zone of organelle exclusion surrounded the septal pore apparatus. Metaphase I of meiosis and metaphase of mitosis were similar. Globular spindle pole bodies with electron-opaque inclusions were set within polar fenestrae of the nuclear envelope. The nuclear envelope was mostly intact with occasional gaps. Fragments of endoplasmic reticulum were present near the spindle pole bodies but did not form a polar cap. Structural characters may distinguish one or more clades of the Agaricomycotina and provide additional signal in phylogenetic analyses.

Septal pore apparatus and nuclear division of Auriscalpium vulgare

Ultrastructure of the septal pore apparatus and nuclear division of Auriscalpium vulgare (Russulales) was examined with freeze substitution and is presented for inclusion in the AFTOL Structural and Biochemical Database (http://aftol.umn.edu). Previously unreported septal characters for the Russulales (Agaricomycotina) were observed: Septa of the hymenophore had bell-shaped perforated septal pore caps that may extend along the septum and a zone of organelle exclusion surrounded the septal pore apparatus. Metaphase I of meiosis and metaphase of mitosis were similar. Globular spindle pole bodies with electron-opaque inclusions were set within polar fenestrae of the nuclear envelope. The nuclear envelope was mostly intact with occasional gaps. Fragments of endoplasmic reticulum were present near the spindle pole bodies but did not form a polar cap. Structural characters may distinguish one or more clades of the Agaricomycotina and provide additional signal in phylogenetic analyses.

Assembling the Fungal Tree of Life: constructing the Structural and Biochemical Database

A major goal of the Assembling the Fungal Tree of Life project is to create a searchable database <http://aftol.umn.edu> of selected ultrastructural and biochemical characters from published and new data for use in phylogenetic and other analyses. While developing this database such issues as evaluating specimen fixation quality in published micrographs, organizing data to accommodate characters that were dependent on location and developmental stage, and requiring accountability of data contributors were addressed. Character states for three traits, septal pore apparatus, nuclear division and spindle pole body cycle, are illustrated, and character states are resolved with maximum parsimony and plotted on a summary cladogram of known phylogenetic relationships of the Fungi. The analysis illustrates the inherent phylogenetic signal of these characters, the paucity of comparable characters and character states in subcellular studies and the challenges in establishing a comprehensive structural and biochemical database of the Fungi.

Assembling the Fungal Tree of Life: constructing the Structural and Biochemical Database

A major goal of the Assembling the Fungal Tree of Life project is to create a searchable database <http://aftol.umn.edu> of selected ultrastructural and biochemical characters from published and new data for use in phylogenetic and other analyses. While developing this database such issues as evaluating specimen fixation quality in published micrographs, organizing data to accommodate characters that were dependent on location and developmental stage, and requiring accountability of data contributors were addressed. Character states for three traits, septal pore apparatus, nuclear division and spindle pole body cycle, are illustrated, and character states are resolved with maximum parsimony and plotted on a summary cladogram of known phylogenetic relationships of the Fungi. The analysis illustrates the inherent phylogenetic signal of these characters, the paucity of comparable characters and character states in subcellular studies and the challenges in establishing a comprehensive structural and biochemical database of the Fungi.

The simple-septate basidiomycetes: a synopsis

The simple-septate basidiomycetes comprise more than 8,000 species that show a high morphological and ecological heterogeneity. To gain insight in the phylogenetic relationships within this group, we compared several ultrastructural features such as septal pore apparatus, form, and behavior of the spindle pole bodies, types of host–parasite interaction, presence or absence of colacosomes, symplechosomes, atractosomes, and cystosomes as well as nuclear rDNA sequences coding for small- and large-subunit rRNA. Based on our integrated analysis, we propose a new classification system for the simple-septate basidiomycetes with the subphylum Pucciniomycotina and the classes Agaricostilbomycetes, Atractiellomycetes, Classiculomycetes, Cryptomycocolacomycetes, Cystobasidiomycetes, Microbotryomycetes, Mixiomycetes, and Pucciniomycetes. We also propose the pucciniomycotinous taxa Cystobasidiales, Erythrobasidiales, Helicobasidiales, Mixiales, Naohideales, Pachnocybales, Spiculogloeales, and Kondoaceae and the new subphyla Agaricomycotina (equivalent to the current Hymenomycetes) and Ustilaginomycotina (equivalent to the current Ustilaginomycetes).

The Exobasidiales: An evolutionary hypothesis

To gain insight in the phylogenetic relationships within the Exobasidiales, septal pore apparatus, host-parasite interactions, sori, hymenia, basidia, and nucleotide sequences from the 5′ terminal domain of the nuclear large subunit rRNA gene were studied and compared.

Ustilaginomycetes on Osmunda

Sporulation, septal pore apparatus and host-parasite interaction between Ustilago osmundae and its host, the royal fern, were analyzed by light and electron microscopy using herbarium material and compared with findings in other species of Basidiomycota. The fungus produced thick-walled and thin-walled hyphae on leaf surfaces and sporulated externally. Coralloid haustoria with numerous lobes were present only in epidermal cells. Hyphae in intercellular spaces were lacking. The septal pore apparatus was composed of a simple pore with two caps. Ustilago osmundae shares the type of septal pore apparatus and host-parasite interaction with the Melanotaeniaceae of Ustilaginomycetes. It differs from the other species of this family primarily in the external sporulation and in the lack of intercellular hyphae. To accomodate this unusual fungus in Melanotaeniaceae a new genus, Exoteliospora, is proposed. Description and illustrations are given for Exoteliospora osmundae.

Ustilaginomycetes on Selaginella

The lycophytes represent the most primitive host group for Ustilaginomycetes. Morphology and ultrastructure of the two known smut species on Selaginella, Melanotaenium oreophilum and M. selaginellae, as well as teliospore germination and the 5’ end of the nuclear large subunit rRNA gene of the first species were studied and compared. The results of molecular analyses suggest that these two smut fungi belong either to the Doassansiales or George-fischeriales. The presence of complex interaction apparatus including cytoplasmic compartments favors the placement in the Doassansiales. M. oreophilum and M. selaginellae share the type of septal pore apparatus and host-parasite interaction with the Doassansiales, but not with the Georgefischeriales. They differ from the other members of the Doassansiales in the pigmentation of the teliospores and, at least in M. oreophilum, in the basidial type. To accomodate these two species in the Doassansiales, a new genus, Melaniella, and a new family, Melaniellaceae, are proposed. Descriptions and illustrations are given for Melaniella oreophila and M. selaginellae.

Ustilaginomycetes on Selaginella

The lycophytes represent the most primitive host group for Ustilaginomycetes. Morphology and ultrastructure of the two known smut species on Selaginella, Melanotaenium oreophilum and M. selaginellae, as well as teliospore germination and the 5’ end of the nuclear large subunit rRNA gene of the first species were studied and compared. The results of molecular analyses suggest that these two smut fungi belong either to the Doassansiales or George-fischeriales. The presence of complex interaction apparatus including cytoplasmic compartments favors the placement in the Doassansiales. M. oreophilum and M. selaginellae share the type of septal pore apparatus and host-parasite interaction with the Doassansiales, but not with the Georgefischeriales. They differ from the other members of the Doassansiales in the pigmentation of the teliospores and, at least in M. oreophilum, in the basidial type. To accomodate these two species in the Doassansiales, a new genus, Melaniella, and a new family, Melaniellaceae, are proposed. Descriptions and illustrations are given for Melaniella oreophila and M. selaginellae.

Septal pore apparatus of the smutUstacystis waldsteiniae

The septal pore apparatus in intercellular hyphae of Ustacystis waldsteiniae was analyzed by serial- section electron microscopy using chemically fixed and high pressure frozen/freeze substituted samples. Sep- ta have a central simple pore with rounded, non- swollen margins. However, the pore apparatus is a highly complex structure, differing significantly from that found in simple- and complex-septate basidi? omycetes. Three features are typical: 1) the pore canal is traversed by two symmetrically arranged bands, 2) a dome shaped membranous cap, intimately attached to the plasma membrane, encloses the pore on both sides, and 3) a thin electron transparent layer and a layer of medium electron density cover the cytoplasmic side of the membranous cap. From our observations of septal pore morphology we suggest a general ab- sence of transport of organelles including ribosomes through the pore.

Meiosis, septal pore architecture, and systematic position of the heterobasidiomycetous fern parasite Herpobasidium filicinum

Meiosis, spindle pole body cycle and septal pores in Herpobasidium filicinum were examined using light and electron microscopy and compared with findings in the Uredinales and other simple-pored heterobasidiomycetes. The septal pore apparatus in Herpobasidium filicinum is rustlike, and the nuclear characteristics are also similar but not identical to those found in the Uredinales. Some details, such as the spindle pole body behaviour at prophase, the presence of a complete wrapping of endoplasmic reticulum surrounding the nucleus during division, the extension of the spindle pole body into the cytoplasm during division, and the nucleolus behaviour, distinguish Herpobasidium filicinum from the rusts. On the other hand, nuclear division and spindle pole body characteristics in Herpobasidium filicinum show some features common with Cryptomycocolax abnorme. However, Herpobasidium filicinum shares more important nuclear features with Pachnocybe ferruginea, Eocronartium muscicola, Helicobasidium mompa, and Helicobasidium brebissonii than with the Uredinales or Cryptomycocolacales. Apart from the phylogenetic implications of the ultrastructural data, the most interesting observation in the present work is the unusual type of meiosis. No evidence for meiosis II was found in basidia of Herpobasidium filicinum. Instead, the genesis of the interphase I spindle pole body in Herpobasidium filicinum is essentially identical to the basidiomycetous postmeiotic and intermitotic spindle pole body duplication. Key words: Herpobasidium filicinum, heterobasidiomycetes, meiosis, septal pore, spindle pole body, ultrastructure.

Septal pore apparatus in some clavarioid fungi: taxonomic and phylogenetic implications

Septal pore apparatus in some clavarioid fungi: taxonomic and phylogenetic implications

Ultrastructure of the Septal Pore Apparatus and Early Septum Initiation inAuricularia Auricula-Judae

The septal pore apparatus and septum initiation in vegetative hyphae of Auricularia auricula-judae were studied by light and electron microscopy for phylogenetic comparisons. Both freeze substituti...

Ultrastructure of the Septal Pore Apparatus and Early Septum Initiation in Auricularia auricula-judae

The septal pore apparatus and septum initiation in vegetative hyphae of Auricularia auricula-judae were studied by light and electron microscopy for phylogenetic comparisons. Both freeze substitution and conventional chemical fixation methods were employed for electron microscopic studies. Septa developed at the base of the clamp connection and in the main hypha near the clamp where the nuclear divisions had occurred. Septum formation lasted about 4 min. Septal swellings were much larger in chemically fixed than in freeze-substituted hyphae. Fine filaments at the adseptal side of the septal pore cap appeared to be attached to the orifice area of the septal pore and to the cap via intermediate structures. Broader filaments, 7.6 to 9.4 nm in diam, usually connected the plasma membrane bordering the cross wall with endoplasmic reticulum which was continuous with the pore cap. There was a central plate in the septal pore. Ribosomes were absent between the plate and the pore cap. Septum initiation and development involved microvesicles, apparently from the Golgi apparatus, and a third type of filament, 10.6-13.2 nm diam. Septal structure supports the relationship of Auricularia to Tremella and functional analysis suggests a general absence of transport of larger organelles between cells, unlike the situation in homobasidiomycetes.

Intracellular appearance, morphological features and properties of oyster mushroom virus

Viruses in Agaricus hisporus and Lentinula edodes are well-known but have not previously been reported in Pleurotus spp. Two kinds of virus were found in sporophores of Pleurotus sapidus in this study. One occurred as spherical particles 24 nm diam and the other as flexuous rods. The virus preparation of P. sapidus had a typical nucleoprotein ultraviolet spectrum and three peaks were obtained during ISCO sucrose density gradient centrifugation. The nucleic acid derived from the spherical virus was shown to be double-stranded ribonucleic acid (dsRNA) by a positive orcinol reaction and RNase treatment. Four major bands appeared during Polyacrylamide gel electrophoresis, and the molecular weight was determined at 1·3, 1·10, 0·98, and 0·85 × 10°6 using CMV dsRNA and virus dsRNA of Aspergillus niger as markers. Two major components of the virus capsid polypeptide with molecular weights 44 and 22 kDa, respectively, were obtained using discontinuous SDS-PAGE. Immune diffusion tests showed that the anti-serum to P. sapidus virus reacted with P. ostreahis virus and P. florida virus. Ultrathin sections of the septal pore apparatus of P. ostreatus revealed the regular arrangement of the pore cap perforation and the openings. Virus particles appear to be able to pass through the septal dolipore. These results provide new evidence for the translocation of viruses in basidiomycetes.