Conidium Ontogeny Research Articles

Molecular Systematics of the Herpotrichiellaceae with an Assessment of the Phylogenetic Positions of Exophiala dermatitidis and Phialophora americana

Despite a significant body of evidence in support of the close phylogenetic relationship of species of Capronia (Herpotrichiellaceae) and black yeasts belonging to or allied with the genus Exophiala, questions concerning the taxonomic importance of features furnished by ascospore, stromal and anamorph characters have remained unanswered. In order to address these issues and to elucidate more fully relationships within the family, we have sequenced a portion of the nuclear large ribosomal RNA subunit (28S), the 5.8S gene, and the internal transcribed spacers (ITS1 and ITS2) of 15 species of Capronia and 19 black yeasts assigned to the form genera Cladosporium, Cladophialophora, Exophiala, Fonsecaea, Phaeococcomyces, Phialophora, Ramichloridium and Rhinocladiella. Cladistic analysis of these data confirmed the monophyly of the Herpotrichiellaceae but did not support the division of the genus Capronia on the basis of conidial ontogeny, pattern of ascospore septation, or the degree of stromal development. Homothallic species of Capronia with 8-spored asci, muriform ascospores and Exophiala anamorphs formed a well-supported lineage that included the medically important species Exophiala dermatitidis. Capronia mansonii and Capronia munkii, morphologically similar taxa isolated from the wood of Populus, were inferred as closely related but separate species. The clade comprising members of the Herpotrichiellaceae that possess Cladosporium-like and Phialophora anamorphs was also strongly supported. Available molecular evidence indicates that Dictyotrichiella semiimmersa and Phialophora americana are teleomorph and anamorph states of a single holomorph. Cladistic analysis also confirmed that the genera Cladophialophora and Ramichloridium are polyphyletic. The anamorphs of Capronia nigerrima and Dictyotrichiella semiimmersa are described and illustrated, and the combination Capronia semiimmersa is proposed.

Molecular systematics of the Herpotrichiellaceae with an assessment of the phylogenetic positions of Exophiala dermatitidis and Phialophora americana

Despite a significant body of evidence in support of the close phylogenetic relationship of species of Capronia (Herpotrichiellaceae) and black yeasts belonging to or allied with the genus Exophiala, questions concerning the taxonomic importance of features furnished by ascospore, stromal and anamorph characters have remained unanswered. In order to address these issues and to elucidate more fully relationships within the family, we have sequenced a portion of the nuclear large ribosomal RNA subunit (28S), the 5.8S gene, and the internal transcribed spacers (ITS1 and ITS2) of 15 species of Capronia and 19 black yeasts assigned to the form genera Cladosporium, Cladophialophora, Exophiala, Fonsecaea, Phaeococcomyces, Phialophora, Ramichloridium and Rhinocladiella. Cladistic analysis of these data confirmed the monophyly of the Herpotrichiellaceae but did not support the division of the genus Capronia on the basis of conidial ontogeny, pattern of ascospore septation, or the degree of stromal development. Homothallic species of Capronia with 8-spored asci, muriform ascospores and Exophiala anamorphs formed a well-supported lineage that included the medically important species Exophiala dermatitidis. Capronia mansonii and Capronia munkii, morphologically similar taxa isolated from the wood of Populus, were inferred as closely related but separate species. The clade comprising members of the Herpotrichiellaceae that possess Cladosporium-like and Phialophora anamorphs was also strongly supported. Available molecular evidence indicates that Dictyotrichiella semiimmersa and Phialophora americana are teleomorph and anamorph states of a single holomorph. Cladistic analysis also confirmed that the genera Cladophialophora and Ramichloridium are polyphyletic. The anamorphs of Capronia nigerrima and Dictyotrichiella semiimmersa are described and illustrated, and the combination Capronia semiimmersa is proposed.

Studies of conidial anatomy and conidiogenesis in Sporoschisma nigroseptatum using light and electron microscopy

The results of an ultrastructural study of the conidial anatomy and conidiogenesis in Sporoschisma nigroseptatum are presented. The development of the conidial chain involves endogenous conidial ontogeny, apical wall-building, and retrogressive conidial delimitation followed by cessation of apical wall-building, then replacement ring wall-building of additional retrogressively delimited conidia, and extrusion of the true conidial chain through the terminal aperture of the conidiogenous cell. Maturation of conidia involves deposition of two inner wall layers and formation of five distosepta. Conidial chains secede schizolytically. No proliferation of the conidiogenous cell occurs and the conidium is delimited by a cross wall that is discontinuous with the periclinal wall. Each conidium has polar plug-and-socket-like structures that are interlocked between adjacent conidia along the conidial chain. Similar plug-and-socket-like structures are also seen in other Sporoschisma species. The taxonomy of Chalara is also briefly discussed with reference to patterns of conidial wall-building.Key words: Chalara, conidial chain, conidial ontogeny, ultrastructures.

Notes onTremella mesentericaand allied species

Some aspects of development and biology of Tremella mesenterica and two closely allied species are discussed; some associated fungi are noted. Tremella brasiliensis, previously known only from neotropical areas, is reported from Japan; an extended description is provided. One North American species, Tremella mesenterella Bandoni & Ginns, is described as new, and other taxa with superficially similar basidiocarps are discussed.Key words: Tremellaceae, Tremella, T. mesenterica, T. mesenterella, T. philippinensis, T. rufobrunnea, conidium ontogeny, basidiome development.

Notes on <I>Tremella mesenterica</I> and allied species

Some aspects of development and biology of Tremella mesenterica and two closely allied species are discussed; some associated fungi are noted. Tremella brasiliensis, previously known only from neotropical areas, is reported from Japan; an extended description is provided. One North American species, Tremella mesenterella Bandoni & Ginns, is described as new, and other taxa with superficially similar basidiocarps are discussed.Key words: Tremellaceae, Tremella, T. mesenterica, T. mesenterella, T. philippinensis, T. rufobrunnea, conidium ontogeny, basidiome development.

Evolutionary relationships of members of the genera Taphrina, Protomyces, Schizosaccharomyces, and related taxa within the archiascomycetes: Integrated analysis of genotypic and phenotypic characters

To study the phylogeny and evolution of archiascomycetes, we determined the full sequence of the nuclear 18S rRNA gene from 14Taphrina species and 2Protomyces species, and the partial sequence ofSchizosaccharomyces japonicus var.japonicus. The sequences were phylogenetically analyzed by the neighbor-joining, maximum parsimony, and maximum-likelihood methods. We also looked at their principal phenotypic characters and genotypic character. Relationships within the Ascomycota are concordant with the previously published phylogenies inferred from 18S rDNA sequence divergence and divide the archi-, hemi-and euascomycetes into distinct major lineages. All the trees show that, within the archiascomycete lineage, 11 of the 14Taphrina species and the 2Protomyces species are monophyletic. A core groups ofTaphrina andProtomyces is always monophyletic. The evidence from molecular and phenotypic characters such as cell wall sugar composition, ubiquinone, cell wall ultrastructure, and mode of conidium ontogeny, strongly suggests that ‘T’. californica CBS 374.39, ‘T’. maculans CBS 427.69 and ‘T’. farlowii CBS 376.39 should be excluded from the archiascomycete lineage. ‘Taphrina’ farlowii CBS 376.39 groups withCandida albicans in the Saccharomycetales, whereas ‘T’. californica CBS 374.39 and ‘T’. maculans CBS 427.69 have a basidiomycete affinity and group with Tremellalean members in the hymenomycete lineage.Schizosaccharomyces is monophyletic. The strictly anamorphic yeastSaitoella complicata groups with the apothecial ascomyceteNeolecta vitellina rather than theTaphrina/Protomyces branch.

The phylogenetic relationships of two trichothecene-producing hyphomycetes, Spicellum roseum and Trichothecium roseum

The phylogenetic relationship between the hyphomycetes Spicellum roseum and Trichothecium roseum was inferred from an analysis of partial sequences of nuclear small (18S) and nuclear large (28S) ribosomal RNA subunits. Both analyses suggest that the two species form a monophyletic group allied with the Hypocreales but sister group relationships are unclear. Colony characters and trichothecene production also support the close relationship between these two species. However, differences in conidiophore branching and conidium ontogeny suggest the retention of separate anamorph genera is justified.

Some electron microscope observations of conidium ontogeny ofSphaceloma murrayaeonSalix

Abstract Conidiomata of Sphaceloma murrayae, formed intra-and subepidermally in willow (Salix spp.) leaves, were acervular. Conidium ontogeny was phialidic i.e., the primary conidium initial developed enteroblastically and with the release of successive conidia, sets of scars formed at a similar level around the phialidic apex. Occasionally successive conidia formed through new loci in existing conidiophores.

Analysis of conidium ontogeny in anamorphs of Ophiostoma: Pesotum and Phialographium are synonyms of Graphium

Representatives of the anamorph-genera Pesotum and Phialographium, supposedly characterized by sympodial and phialidic conidiogenesis, respectively, were shown to exhibit more than one kind of conidium formation. Specifically, conidiogenous cells of both genera proliferated percurrently, a process supposedly diagnostic of the related genus Graphium. Accordingly, the three genera are merged in Graphium, the oldest name.

Ceratopycnidium baccharidicola sp. nov., from Baccharis coridifolia in Argentina

Ceratopycnidium baccharidicola sp. nov. is described, illustrated and compared with C. citricola , the type species of the genus. Both have similar conidial ontogeny. The new species was isolated as an endophyte from Baccharis coridifolia .

An evaluation of straw-extract agar media for the growth and sporulation of Madurella mycetomatis

Four new media, namely Wheat straw extract agar, Bajra straw extract agar, Jowar straw extract agar and Paddy straw extract agar, were evaluated for their potential to stimulate the growth and sporulation of Madurella mycetomatis in comparison with the conventional Sabouraud dextrose agar and Soil extract agar. Vegetative growth of M. mycetomatis on the four types of Straw extract agars was superior to that obtained on Sabouraud dextrose agar. Isolates of M. mycetomatis sporulated better and faster on the Straw extract agars than on the Sabouraud dextrose agar and Soil extract agar. Straw extract agar is recommended as a sporulation medium for M. mycetomatis. It may prove useful especially for studies of the conidium ontogeny of the fungus for elucidating its taxonomic status.

Ultrastructure of budding process ofMalassezia pachydermatis

The ultrastructure of Malassezia pachydermatis and its budding process was investigated by scanning and transmission electron microscopy. The innermost layer of the cell wall showed the serrated structure characteristic of the genus Malassezia. In the daughter cell, this structure became more defined as the cell grew. The mode of conidium ontogeny was monopolar blastic development with a collarette. The appearance was similar to that reported previously for Malassezia furfur, with the following difference: the budding base was 0.9-1.1 microns in diameter which was broader than that of M. furfur (0.5-0.7 microns).

Some electron microscope observations ofPhlyctema vagabundaonSalix

Abstract Conidiomata of Phlyctema vagabunda formed subepidermally in willow (Salix spp.) leaves were eustromatic andacervular, becoming erumpent and cupulate. Conidia were released by rupture of both the apical stromatal wall and host epidermal tissues. Conidium ontogeny was phialidic, viz., the primary conidium developed enteroblastically and sets of scars formed at the same level around the phialidic apex. Conidium-delimiting septa were aperforate.

An Ultrastructural Comparison of Conidiogenesis inScedosporium Apiospermum, Scedosporium InflatumandScopulariopsis Brumptii

The major objective of this study was to characterize conidium ontogeny in S. inflatum as compared and contrasted with S. apiospermum and S. briumptii

Nuclear behaviour during conidial ontogeny of Bremia lactucae

Cytological examination of nuclear behaviour during conidial ontogeny of one isolate of Bremia lactucae , growing under controlled conditions in detached cotyledons of lettuce, Lactuca sativa cv. Imperial Triumph, and of a second isolate in field grown leaves of the same cultivar showed that one nucleus migrated into conidial initials and no nuclear migrations were found at later developmental stages. The first three mitoses in conidia were nearly synchronous at incubation temperatures of 4·5°, 15° and 20·5 °C. A fourth mitosis occurred in 60% of spores at 4·5° and this was also nearly synchronous. At 15° and 20·5° in 85% of spores there was a fourth mitosis, but in the other 15% only some of the nuclei divided. Fifth mitoses were less synchronous than the fourth. Nuclear behaviour during conidiogenesis in the field at several geographically diverse sites in different years was consistent with that under controlled conditions indicating that the behaviour is a stable, heritable characteristic. Secondary migration into developing conidia is likely to be rare, and conidia will then be homokaryotic providing there is no mitotic segregation during conidial development.

Conidiogenesis in Phoma betae

Conidiogenesis in Phoma betae (teleomorph: Pleospora betae ) was studied using thin sections of pycnidia observed under the TEM. Four stages of conidial ontogeny (initiation, maturation, delimitation and secession) are distinguished. Conidiogenous development in P. betae is described as both holoblastic and enteroblastic.

The Synnematous Hyphomycete Dictyocatenulata Alba

The synnematous hyphomycete Dictyocatenulata alba Finley & Morris was described as the only species of the genus (Morris and Finley, 1967). Because the species was described in a journal unfamiliar to many mycologists and the original illustration was rather diagrammatic, D. alba has remained a poorly known species despite its comparatively common occurrence. The purpose of this note is to provide a detailed description and illustrations of the organism, as well as to discuss its conidium ontogeny, report on extensions of its known distribution, and to speculate on some other aspects of its biology.

Charomyces, a new genus of Hyphomycetes with thallic–arthric conidia

Charomyces amphimelas is described as the type species of a new anamorph genus of Hyphomycetes. The species produces verticillate conidiogenous hyphae that become chains of cylindrical brown ameroconidia with black polar bands. Conidium ontogeny is apparently thallic–arthric, and conidia secede rhexolytically.

Ultrastructure of conidiogenesis in Cercospora beticola

Details of an optical, scanning and transmission electron microscope study of conidiophores and conidiogenesis in Cercospora beticola are reported. Some conidiophore initials are formed enteroblastically from stromatic cells ; others are formed holoblastically. Conidial ontogeny is confirmed as holoblastic and secession as schizolytic. Scars at the conidial base and the conidiogenous locus become thickened by the deposition of additional granular electron-opaque wall material over the initially translucent layer of the delimiting septum. Proliferation of the conidiogenous cell after conidial formation is enteroblastic.

Conidium Ontogeny in Pyricularia1

AbstractConidium ontogeny of twenty‐three isolates of Pyricularia (including international races, some nutritional, coloured mutants and isolates obtained from cultivated and wild species of Gramineae) was studied. Among them, sixteen isolates were found to be of typical blastic type of conidiogenesis characteristic of the genus Pyricularia. Three coloured mutants and an international race showed gangliar type of conidiogenesis. However, two races and one nutritional mutant showed both the types.Most of the isolates tested are morphologically indistinguishable and potentially pathogenic with the respective hosts and on differential cultivars. Possible alteration of morphogenetic pattern of conidiogenesis by mutation and temperature response is suggested.