YEASTS ISOLATED FROM HOMOBASIDIOMYCETES (ASTEROPHORA, COLLYBIA) - NEW ASPECTS FOR SEXUALITY, TAXONOMY, AND SPECIATION

Prillinger, H., Altenbuchner, J., Laaser, G., and Dörfler, C. 1993. Yeasts isolated from Homobasidiomycetes (Asterophora, Collybia): New aspects for sexuality, taxonomy, and speciation. Experimental Mycology 17, 24-45. A positive selection vector to clone fungal nDNA in Escherichia coli together with random-fragment hybridization analysis turned out to be useful for clarifying the taxonomic relationship between the yeast and hyphal strains from Asterophora lycoperdoides and A. parasitica, on the one hand, and for confirming conspecificity of the Collybia yeasts (C. cirrata, C. cf. cookei, and C. tuberosa) and detecting processes of speciation, on the other. The rapid loss of sexual compatibility between the yeast and hyphal strains from Collybia accompanied by a distinct RFLP with a few nDNA probes permits the early stages of speciation in the dimorphic Collybia species to be investigated. Although the species-specific intracellular yeasts isolated from two Asterophora species exhibited a remarkable degree of nDNA/nDNA reassociation and an identical ubiquinone (Q-9) system, conspecificity as well as a suspected partial identity of the nDNA from Asterophora yeasts and hyphae could be excluded. The conspecificity of the Collybia yeasts and hyphae, already established by morphological data and rDNA analysis, could be confirmed using homologous and heterologous hybridization experiments performed with Southern-blotted nDNA digested with different restriction endonucleases and hybridized with cloned 3- to 10-kb BamHI nDNA fragments from yeasts and hyphae as a probe. The physiological characterization of the Collybia yeasts displayed a remarkable variability. The qualitative and quantitative monosaccharide pattern of purified yeast cell walls exhibited some similarities to tremelloid fungi. Data are discussed in the light of taxonomy, mating-type evolution, and speciation. © 1993 Academic Press. All rights reserved.