Surface Ultrastructure of Oidia in the Basidiomycete Psathyrella coprophila

Abstract

The existence of oidia has long been known and their structure and development have been described using the light microscope (Brodie, 1936). They are formed asexually, are uninucleate and usually borne in clusters on the monokaryotic mycelia of many basidiomycetes. Oidia of different species may have different functions. In some species they readily germinate to form monokaryotic mycelia. In many coprophilous species they do not germinate (Falck, 1902), and they probably act as fertilizing agents or spermatia. The oidia of Psathyrella coprophila Watling (Watling & Jurand, 1971)~ which were used in this investigation, do not germinate. They are borne on oidiophores and cohere in a droplet of mucilage.The surface structure of oidia is of interest in studies of the relationship between the hyphae and the oidia. Hyphae of many species are known to react to an oidial stimulus by growing towards and fusing with oidia (Bistis, 1970; Kemp, 1970). The directed growth and fusion between hyphae and oidia is either followed by dikaryotization or by vacuolation and death. Dikaryotization indicates that two isolates belong to the same species. Homing followed by a lethal reaction indicates that two isolates are closely related. The physiological basis for the recognition of oidia by hyphae has not yet been resolved and a study of the oidial surface might be relevant to this problem.From this preliminary study it is suggested that the surface of the oidia of PsathyreZZa coprophila has numerous filamentous appendages which may be embedded in a layer of mucilage. A similar surface structure has been described in certain bacteria. In some respects the filamentous appendages appear to resemble bacterial fimbriae (pili) (Duguid, Smith, Dempster & Edmunds, 1955; Brinton, 1969, and the mucilaginous coat in which they are embedded may be similar to bacterial capsules (Duguid, 1951). METHODSPsathyrella coprophila was chosen because it produces abundant oidia in culture. Monokaryotic mycelia, from basidiospores of the type specimen which is deposited in the herbarium of the Royal Botanic Garden, Edinburgh, were grown on agar plates at 20 "C on horse-dung extract agar (Lange, 1952). The oidia were harvested when the mycelium almost covered the agar surface.For electron-microscope preparations the oidia were harvested with 0.8 I yo (w/v) NaCl.About 4 ml of the saline solution was poured into each plate, the oidia suspended by gentle rocking and the suspension centrifuged at 3000 rev./min for 5 min to concentrate the oidia into a pellet. Three fixation methods were used:(i) Fixation with OsO, (I %, w/v) according to Palade (I952), but with addition of 0.045 mg sucrose/ml of fixative, for I h at room temperature;

Asexual Sporulation inCoprinus cinereus:Structure and Development of Oidiophores and Oidia in anAmut BmutHomokaryon

“…Due to the application of cryotechniques in sample preparation (high pressure freezing followed by freeze-substitution) our electron microscopic pictures of harvested oidia show newly for C. cinereus hairy appendages on the primary cell wall. Similar surface fibrils were also found on the oidia of Psathyrella coprophila (Coprinaceae; Jurand and Kemp, 1972) and on conidia and chlamydospores of several other hymenomycetes (Palmer et al, 1983a,b). Such structures are thought to play a role in cell-cell interactions such as in conjugation (Day and Poon, 1975), pathogenicity (Benhamou et al, 1986), and flocculation (Calleja et al, 1977).…”

“…The spores of strain AmutBmut are embedded in a gelatinous mucilage (Fig. 9C), as are the oidia of C. cinereus monokaryons (Watling, 1979) and those of P. coprophila (Jurand and Kemp, 1972). This mucilage is thought to be related to the fibrils and likely contributes to the sticky spore character (Watling, 1979).…”

Molecular phylogenetics and taxonomy in Psathyrellaceae (Agaricales) with focus on psathyrelloid species: introduction of three new genera and 18 new species

“…The major taxonomic treatments of the genus Psathyrella by Smith (1972), , Kits van Waveren (1985), and Singer (1986) were mainly based on phenotypic characters although sometimes complemented by mating tests using haploid mycelia (Galland 1972;Jurand and Kemp 1972). The infrageneric classification differs among authors.…”

Incompatibility in basidiomycetes: The heterogenic Pentax

“…It is essential to do this in a tetrapolar species to distinguish between common-B heterokaryons and true dikaryons which may be found only at the junction-line in certain matings (Kemp, 1980). Blocker monokaryons into which nuclei cannot migrate are not uncommon in many species of Coprinus (Kemp, 1974) and Psathyrella (Jurand, 1975). A compatible mating between a blocker and a normal strain obtained from a different fruit-body usually results in unilateral nuclear migration, but a mating between two blocker monokaryons, derived from the same fruit-body, may be fully incompatible in Coprinus bisporus and C. congregatus (Kemp, unpublished) or give a junctionline dikaryon as in C. sassii (Kemp, 1974).…”