Phase Transition in Wangiella Dermatitidis: Identification of Cell-Division-Cycle Genes Involved in Yeast Bud Emergence

  • Chester R. CooperJr.


Yeast-to-multicellular-form (Y→Mc) conversion in the darkly-pigmented (dematiaceous), pathogenic fungus Wangiella dermatitidis represents an excellent model to investigate similar phase transitions exhibited by other dematiaceous fungi upon invasion of host tissue. The yeast-phase cell cycle of W. dermatitidis and its role in Y→Mc conversion was studied by previous investigators using temperature-sensitive (ts) morphological mutants. Both the mutants, designated multicellular (Mc) strains, and the parental wild type grow as virtually indistinguishable budding yeasts at the permissive temperature (25 °C). However, at the restrictive temperature (37 °C), the Mc strains quantitatively undergo Y→Mc conversion whereas the wild type continues to grow as a yeast. In two Mc strains, Mc2 and Mc3, the ts lesions reflect distinct cell-cycle execution points for yeast bud emergence. This suggests that the ts lesions delimit separate mutations in one or more genes.

Because W. dermatitidis is an asexual fungus, a parasexual system of genetic analysis was established to investigate the relationship of the ts lesions in strains Mc2 and Mc3. Specifically, spheroplasts of melanin-deficient (albino) auxotrophs independently derived from strains Mc2 and Mc3 were fused and regenerated at 25 °C in minimal medium. The resulting fusion products were dematiaceous and prototrophic. At 37°C, all fusion products exhibited polarized growth predominantly as uninucleate yeasts and less frequently as moniliform hyphae. These results indicated that the mutation in each Mc parental strain was complemented by a wild-type allele present in its fusion partner. Subsequent analysis of albino ts segregants derived from one fusion product demonstrated that the ts lesions in strains Mc2 and Mc3 were non-allelic. Hence, the genes defined by these mutations have been designated CDC1 and CDC2, respectively. These are the first cell-division-cycle genes identified in a dematiaceous fungus. Their discovery provides the basis for additional studies into the molecular mechanisms involved in fungal morphogenesis and pathogenesis.


Parental Strain Fusion Product Restrictive Temperature Dematiaceous Fungus Parasexual Cycle 
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Copyright information

© Springer Science+Business Media New York 1993

Authors and Affiliations

  • Chester R. CooperJr.
    • 1
  1. 1.Molecular Genetics Program and Laboratories for Mycology, Wadsworth Center for Laboratories and ResearchNew York State Department of HealthAlbanyUSA

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