397 research outputs found
The anamorph genus <i>Knufia</i> and its phylogenetically allied species in <i>Coniosporium</i>, <i>Sarcinomyces</i>, and <i>Phaeococcomyces</i>
No full text Knufia endospora , a species described previously on the basis of cultured material, was found forming distinctive sporodochia on the bark of balsam poplar. Phylogenetic analyses of this fungus and some allied species indicated that (i) it forms a monophyletic group with Knufia cryptophialidica (type species of Knufia ) and with Coniosporium perforans , Coniosporium epidermidis and Phaeococcomyces chersonesos and (ii) P. chersonesos and Sarcinomyces petricola are conspecific. These Coniosporium and Phaeococcomyces species also shared major morphological characteristics with Knufia in culture and were morphologically and phylogenetically distant from the type species of their respective genera. The following new combinations are proposed: Knufia perforans (Sterflinger) Tsuneda, Hambleton & Currah; Knufia epidermidis (D.M. Li, de Hoog, Saunte & X.R. Chen) Tsuneda, Hambleton & Currah; and Knufia chersonesos (Bogom. & Minter) Tsuneda, Hambleton & Currah. Phaeococcomyces catenatus and Phaeococcomyces nigricans (type species of Phaeococcomyces) were morphologically similar but phylogenetically distant from each other and from Knufia. </jats:p
Endoconidiogenesis in Endoconidioma populi and Phaeotheca fissurella
No full textDetails of the development of endoconidia were basically the same in Endoconidioma populi and Phaeotheca fissurella. In both species, endoconidiogenesis involved (i) subdivision of conidiogenous mother cells by septation to form two to several daughter cells; (ii) accumulation of an electrondense material between the daughter and mother cell walls; and (iii) separation of the daughter cells by septum schizolysis, accompanied by the dissolution of mother cell wall. Conidiomata of E. populi were unique in having a closed peridium and a locule filled with conidiogenous mother cells and, therefore, we proposed the new term, cleistopycnidium (pl. -a), for this structure. In the cleistopycnidium of E. populi, endoconidiation usually began in the core of the locule and spread outward. Release of endoconidia was by the degeneration of peridial cell walls
Endomembrane system of aspen roots plays a key role in defense against a common fungal endophyte Cryptosporiopsis radicicola
No full textThe host-endophyte interaction between roots of aspen (Populus tremuloides) andCryptosporiopsis radicicola was examined primarily by transmission electron microscopy. Hyphae growing on the exterior of the inoculated roots had a thick, electron-dense, adhesive sheath. At hyphal contact and penetration, host epidermal cells exhibited a series of defense responses (viz. formation of papillae and partition walls, general wall thickening and walling-off of internal hyphae). In papilla formation, loop-shaped, rough endoplasmic reticula (rER) gave rise to globose secretory vesicles that accumulated around and then fused to the developing papilla. Unlike papillae, general wall thickening was associated with the Golgi apparatus (GA) that produced cell wall materials; 1–3 layers of Golgi cisternae were in contact with or in the immediate proximity (mostly within 0–0.5 mm) of and lying parallel to the host cell wall, where they budded out numerous subglobose vesicles that fused directly to the host cell wall and made it thicker. Partition wall formation and walling-off of internal hyphae also were common; the former was associated with an extended single cisterna, which was indistinguishable from rER or individual cisternae of GA, and in the latter phenomenon internal hyphae were encased by electron-dense material containing numerous ribosomes and membranous elements that were derived apparently from proliferated rER. These pronounced defense responses protected the stele and contributed to making C. radicicola endophytic rather than pathogenic
Ascomatal Morphogenesis in Myxotrichum arcticum Supports the Derivation of the Myxotrichaceae from a Discomycetous Ancestor
No full textElectron microscopy shows that ascomata of Myxotricum arcticum bear a striking resemblance to discocarps in morphogenesis and in previously overlooked aspects of gross morphology. Although mature ascomata of M. arcticum superficially resemble reticuloperidial cleistothecia common in the Onygenales, the bramble-like aggregation of thickwalled hyphae, previously considered to represent a closed peridium, forms a basket-like apothecium that overarches a distinct hymenium of stipitate, protunicate asci interspersed with paraphyses. There is no evidence of asci developing in chains and at different levels as is characteristic of the centrum of many Eurotiomycetes. Instead, more or less globose, stipitate and evanescent asci arise individually from penultimate cells of croziers and develop almost synchronously across a distinct hymenial layer derived from a richly branched network of crozier-bearing hyphae. After dissolution of the ascus wall, ascospores adhere to a membranous sheath that underlies the hymenium. These observations provide strong support for prior suggestions based on molecular phylogenetic comparisons that the Myxotrichaceae recently are derived from a helotialean ancestor. Observations of conidiogenesis show that the typical Oidiodendron anamorph is accompanied by a second conidiogenous form with ampullae and botryose clusters of blastic conidia
Morphology and Phylogenetic Placement of Endoconidioma, a New Endoconidial Genus from Trembling Aspen
No full textEndoconidioma populi gen. et sp. nov. is described from black subicula on twigs of trembling aspen, Populus tremuloides, in Alberta, Canada. Pycnidium- like conidiomata are produced on twigs and in culture, but, unlike pycnidia, conidiomata of E. populi have a closed peridium and a locule filled with conidiogenous cells that form conidia endogenously. These endoconidia are hyaline, unicellular and released by the dissolution of the peridial cell wall. In addition to endoconidia, mostly two-celled conidia that form blastically from undifferentiated hyphae occur often in culture but are observed only occasionally on Populus twigs. No coelomycetous taxa have been reported to produce endoconidia, and both the morphological features and DNA sequence data demonstrate that Endoconidioma is distinct from the previously established endoconidial genera. Parsimony analyses of portions of the nuclear ribosomal RNA gene (SSU and ITS) suggest that Endoconidioma is closely related phylogenetically to members of the Dothideales and allied anamorphs in Hormonema and Kabatina
Morphology and development of the reticuloperidial ascomata of Auxarthron conjugatum
No full textLight and electron microscopy showed that the reticuloperidium of thick-walled hyphae, characteristic of the mature ascoma of Auxarthron conjugatum, originated from branches that grew from the broad, gyre-like hyphal loops making up the ascomatal initials. Within the developing peridium, short, acropetally proliferating chains of prototunicate asci each arose from a single crozier and matured from base to tip. The walls of young asci were two-layered but evanesced as they matured with the outer layer dissolving before the inner one. Distal asci in some chains retained the inner wall, detached from adjacent asci by septum schizolysis and when transferred to fresh media produced germ tubes and mycelium. Ultraviolet epifluorescent staining with a DNA intercalator (Hoechst) indicated that these spore-like asci probably contained diploid nuclei. In normal asci, ascospores had an inner, electron lucent primary wall and a three-layered secondary wall. The deposition pattern of the middle layer of the secondary wall created the distinctive array of pits and ridges characteristic of the ascospores in this taxon. The production of ascospores, spore-like asci and arthroconidia, along with the tendency of ascospores to adhere in a mass, is interpreted as contributing to the reproductive flexibility and inoculum potential of A. conjugatum. In all respects the ascomata of A. conjugatum differed substantially from the morphologically similar taxon, Myxotrichum arcticum. These findings underscore the benefit of using DNA-based phylogenies in concert with cytological and ultrastructural observations for exploring selective pressures behind homoplasious characters and revealing novel structural features
Evidence that the gemmae of Papulaspora sepedonioides are neotenous perithecia in the Melanosporales
No full textPapulaspora sepedonioides produces large multicellular gemmae with several, thick-walled central cells enclosed within a sheath of smaller thinwalled cells. Phylogenetic analysis of the large subunit rDNA indicates P. sepedonioides has affinities to the Melanosporales (Hypocreomycetidae). The development of gemmae in P. sepedonioides was characterized by light and scanning and transmission electron microscopy and was similar to previous ontogenetic studies of ascoma development in the Melanosporales. However instead of giving rise to ascogenous tissues the central cells of the incipient gemma became darkly pigmented, thick walled and filled with lipid globules while the contents of the sheath cells autolysed, leaving them empty and deflated at maturity. Both central cells and pre-autolytic sheath cells produced both germ tubes and new gemmae primordia, suggesting microcyclic conidiogenesis occurs in this species. Mature gemmae were nondeciduous or seceded by schizolytic secession and appear to have both perennating and disseminative potential. The evolution of these neotenous perithecial propagules may be driven by life-history and ecological factors selecting for functional versatility
Modified Regional Self-Interaction Correction Method Based on the Pseudospectral Method
No full textA modification of the regional self-interaction correction (RSIC) scheme (Tsuneda et al., J. Comput. Chem. 2003, 24, 1592), pseudospectral RSIC (PSRSIC), is proposed to eliminate the self-interaction errors (SIEs) especially in core regions. PSRSIC reduces the SIEs by substituting the HF exchange energy density calculated with the use of the pseudospectral technique for the exchange energy in the SI-domain region. PSRSIC is combined with the long-range correction (LC) scheme. TDDFT calculations with LC-PSRSIC yield all of the core-, valence-, Rydberg-, and charge-transfer-excitation energies with reasonable accuracy. Core-ionization energies are also well-reproduced by LC-PSRSIC
Phialocephala urceolata sp. nov. from a commercial, water soluble heparin solution
No full textPhialocephala urceolata sp. nov. was isolated from a black film that had developed on a watersoluble proprietary heparin solution (pH 2.5). Morphological and enzymatic characters, along with phylogenetic analyses of rDNA sequence data, indicated that the conidial fungus is closely related to species of Phialocephala known primarily as endophytes in the roots of vascular plants (e.g. Acephala applanata, P. fortinii and P. sphaeroides) or as associates of persistent plant organs such as the stems and needles of woody plants (e.g. P. compacta, P. dimorphospora and P. scopiformis). Phialocephala urceolata is distinctive in having urn-shaped phialides that are sparsely distributed along the conidiophore axis, a slow growth rate in culture and in exhibiting a unique combination of reactions on enzymatic test media (i.e. it acidifies casamino acids medium and is gelatinase negative). Partial sequence data from the small subunit (SSU) rDNA indicated that P. urceolata is among the Helotiales and close to the type species of Phialocephala. Sequence data from the internal transcribed spacer (ITS) region places P. urceolata closest to P. sphaeroides. The source of this contaminant is unknown but its taxonomic relationship with other root endophytic species and its ability to produce polyphenol oxidases suggest that the natural habitat of this species is possibly woody plant tissues or soil enriched with lignocellulose
<i>Endoconidioma populi</i> from aspen and alder: phylogeny, and variations in cleistopycnidial morphology and their ecological implications
No full text Cleistopycnidial ontogeny and sequences of nuclear internal transcribed spacers (ITS) and large subunits (LSU) were compared for five strains of Endoconidioma populi Tsuneda et al.: three from trembling aspen and two from alder. The cleistopycnidia of two of the aspen strains, including the type strain, were subglobose to flask-shaped (mostly 35–100 µm × 30–60 µm), and consisted solely of meristematic cells with thick cell walls that were heavily impregnated with melanin granules. Peridial cells were not visibly differentiated from locular cells and were also capable of forming endoconidia. Endoconidia were released from one to several sites of the cleistopycnidium by the dissolution of peridial cell wall. The alder strains shared these characteristics, except that their cleistopycnidia released both endoconidia and conidiogenous cells. Unlike those four strains, cleistopycnidia of the third aspen strain were cylindrical, often exceeding 500 µm in length, branched, and possessed a peridium of textura angularis that developed from short, determinate hyphae. Conidiogenous cells contained abundant lipid bodies that were not mobilized until the onset of endoconidiogenesis. The peridium at the basal area was prone to breakage by external forces, indicating that the individual cleistopycnidium, as a whole, functions as a dispersal unit. A small number of ITS nucleotide differences among strains corresponded to their observed morphological differences and host association. Phylogenetic analyses suggested a close relationship of E. populi with Hormonema carpetanum Bills, Peláez & Ruibal, and Coniozyma leucospermi (Crous & Denman) Crous. </jats:p
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