Morphological and genomic characterization of Filobasidiella depauperata: a homothallic sibling species of the pathogenic cryptococcus species complex.
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The fungal species Cryptococcus neoformans and Cryptococcus gattii cause respiratory and neurological disease in animals and humans following inhalation of basidiospores or desiccated yeast cells from the environment. Sexual reproduction in C. neoformans and C. gattii is controlled by a bipolar system in which a single mating type locus (MAT) specifies compatibility. These two species are dimorphic, growing as yeast in the asexual stage, and producing hyphae, basidia, and basidiospores during the sexual stage. In contrast, Filobasidiella depauperata, one of the closest related species, grows exclusively as hyphae and it is found in association with decaying insects. Examination of two available strains of F. depauperata showed that the life cycle of this fungal species shares features associated with the unisexual or same-sex mating cycle in C. neoformans. Therefore, F. depauperata may represent a homothallic and possibly an obligately sexual fungal species. RAPD genotyping of 39 randomly isolated progeny from isolate CBS7855 revealed a new genotype pattern in one of the isolated basidiospores progeny, therefore suggesting that the homothallic cycle in F. depauperata could lead to the emergence of new genotypes. Phylogenetic analyses of genes linked to MAT in C. neoformans indicated that two of these genes in F. depauperata, MYO2 and STE20, appear to form a monophyletic clade with the MATa alleles of C. neoformans and C. gattii, and thus these genes may have been recruited to the MAT locus before F. depauperata diverged. Furthermore, the ancestral MATa locus may have undergone accelerated evolution prior to the divergence of the pathogenic Cryptococcus species since several of the genes linked to the MATa locus appear to have a higher number of changes and substitutions than their MATalpha counterparts. Synteny analyses between C. neoformans and F. depauperata showed that genomic regions on other chromosomes displayed conserved gene order. In contrast, the genes linked to the MAT locus of C. neoformans showed a higher number of chromosomal translocations in the genome of F. depauperata. We therefore propose that chromosomal rearrangements appear to be a major force driving speciation and sexual divergence in these closely related pathogenic and saprobic species.
Genes, Mating Type, Fungal
Microscopy, Electron, Scanning
Microscopy, Electron, Transmission
Nucleic Acid Hybridization
Polymerase Chain Reaction
Published Version (Please cite this version)10.1371/journal.pone.0009620
Publication InfoDietrich, FS; Findley, K; Heitman, Joseph; Rodriguez-Carres, M; & Sun, S (2010). Morphological and genomic characterization of Filobasidiella depauperata: a homothallic sibling species of the pathogenic cryptococcus species complex. PLoS One, 5(3). pp. e9620. 10.1371/journal.pone.0009620. Retrieved from http://hdl.handle.net/10161/4531.
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Chair, Department of Molecular Genetics and Microbiology
Signal transduction cascades regulating development and virulence of microorganisms Our research focuses on how cells sense their environment and communicate with other cells. We employ genetic and biochemical approaches to study two divergent single-celled eukaryotic organisms, the yeast Saccharomyces cerevisiae and the pathogenic fungus Cryptococcus neoformans. These organisms both grow as budding yeasts and appear quite similar, yet they have been diverging ov