Morphogenesis ofFilobasidiella Neoformans, the Sexual State ofCryptococcus Neoformans

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Abstract
SUMMARY Morphogenesis of Filobasidiella neoformans (= Cryptococcus neoformans) has been studied. A dikaryotic mycelium with clamp connections is formed after conjugation of two yeast cells of opposite mating type. A nonseptate, slender basidium with an abruptly expanded apex arises laterally or terminally from the dikaryotic hypha. The zygote nucleus in the basidium undergoes meiosis and the four resulting haploid nuclei appear in the apical area of the basidium. As the nuclei divide by mitosis, uninucleate basidiospores are budded out from four spots on the apex of basidium. This basipetal budding produces long chains of basidiospores. Genetic analysis has revealed a bipolar mating type system in this pathogen. The phylogenetic relationship of F. neoformans with other fungi is discussed.