Sex in Fungi

Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Annual Review of Genetics (Impact Factor: 15.72). 11/2010; 45(1):405-30. DOI: 10.1146/annurev-genet-110410-132536
Source: PubMed


Sexual reproduction enables genetic exchange in eukaryotic organisms as diverse as fungi, animals, plants, and ciliates. Given its ubiquity, sex is thought to have evolved once, possibly concomitant with or shortly after the origin of eukaryotic organisms themselves. The basic principles of sex are conserved, including ploidy changes, the formation of gametes via meiosis, mate recognition, and cell-cell fusion leading to the production of a zygote. Although the basic tenants are shared, sex determination and sexual reproduction occur in myriad forms throughout nature, including outbreeding systems with more than two mating types or sexes, unisexual selfing, and even examples in which organisms switch mating type. As robust and diverse genetic models, fungi provide insights into the molecular nature of sex, sexual specification, and evolution to advance our understanding of sexual reproduction and its impact throughout the eukaryotic tree of life.

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    • "Significantly, clinical C. neoformans isolates were found to show varied AIF1 expression. For example, one isolate showed high levels of heteroresistance to fluconazole and stable Chr1 aneuploidy, and these characteristics were a consequence of decreased AIF1 expression (Semighini et al. 2011). Thus, regulation of apoptosis-like pathways can modulate aneuploid formation and associated drug resistance in pathogens such as C. neoformans. "
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    ABSTRACT: Human fungal pathogens can exist in a variety of ploidy states, including euploid and aneuploid forms. Ploidy change has a major impact on phenotypic properties, including the regulation of interactions with the human host. In addition, the rapid emergence of drug-resistant isolates is often associated with the formation of specific supernumerary chromosomes. Pathogens such as Candida albicans and Cryptococcus neoformans appear particularly well adapted for propagation in multiple ploidy states with novel pathways driving ploidy variation. In both species, heterozygous cells also readily undergo loss of heterozygosity (LOH), leading to additional phenotypic changes such as altered drug resistance. Here, we examine the sexual and parasexual cycles that drive ploidy variation in human fungal pathogens and discuss ploidy and LOH events with respect to their far-reaching roles in fungal adaptation and pathogenesis.
    Cold Spring Harbor Perspectives in Medicine 07/2014; 4(10). DOI:10.1101/cshperspect.a019604 · 9.47 Impact Factor
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    • "Fungal mating types are determined by a single genetic locus termed the mating-type locus (MAT locus), which consists of highly divergent nonhomologous genes that are termed idiomorphs (Heitman et al. 2013). Generally, the MAT idiomorphs encode for two key transcriptional regulators: where the MAT1-1 mating type is controlled by the MAT1-1-1 α-box transcription factor and where the MAT1-2 mating type is controlled by the MAT1-2-1 high-mobility group (HMG) transcription factor (Ni et al. 2011). Whereas some fungal species have a heterothallic (outcrossing) mating system [e.g., Neurospora crassa (Metzenberg and Glass 1990) and Aspergillus fumigatus (O’Gorman et al. 2009)] involving each individual having either the MAT1-1-1 or the MAT1-2-1 idiomorph, others can reproduce homothallically; the individual carries both idiomorphs, and thus a single strain is capable of mating with itself, i.e., it is self-fertile [e.g., Aspergillus nidulans (Paoletti et al. 2007), Sclerotinia sclerotiorum (Amselem et al. 2011), Sordaria macrospora (Klix et al. 2010)]. "
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    ABSTRACT: White-nose syndrome (WNS) of bats has devastated bat populations in eastern North America since its discovery in 2006. WNS, caused by the fungus Pseudogymnoascus destructans, has spread quickly in North America and become one of the most severe wildlife epidemics of our time. While P. destructans is spreading rapidly in North America, nothing is known about the sexual capacity of this fungus. To gain insight into the genes involved in sexual reproduction, we characterized the mating-type locus (MAT) of two Pseudogymnoascus spp. that are closely related to P. destructans and homothallic (self-fertile). As with other homothallic Ascomycota, the MAT locus of these two species encodes a conserved α-box protein (MAT1-1-1) as well as two high mobility group (HMG) box proteins (MAT1-1-3 and MAT1-2-1). Comparisons to the MAT locus of the North American isolate of P. destructans (the ex-type isolate) revealed that this isolate of P. destructans was missing a clear homolog of the conserved HMG box protein (MAT1-2-1). These data prompted the discovery and molecular characterization of a heterothallic mating system in isolates of P. destructans from the Czech Republic. Both mating types of P. destructans were found to coexist within hibernacula, suggesting the presence of mating populations in Europe. Although populations of P. destructans in North America are thought to be clonal and of one mating type, the potential for sexual recombination indicates that continued vigilance is needed regarding introductions of additional isolates of this pathogen.
    G3-Genes Genomes Genetics 07/2014; 4(9). DOI:10.1534/g3.114.012641 · 3.20 Impact Factor
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    • "This result is consistent with uniparental mitochondrion inheritance within Candida spp. (Ni et al. 2011), although previous observations of chimeric sequences in C. orthopsilosis mitochondrial genomes (Valach et al. 2012) suggest that recombination could also occur between the two parental mitochondrial genomes. Altogether our results point to a chimeric genome of MCO456 with two distinct haplotypes at approximately 5% divergence. "
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    ABSTRACT: The Candida parapsilosis species complex comprises a group of emerging human pathogens of varying virulence. This complex was recently subdivided into three different species: C. parapsilosis sensu stricto, C. metapsilosis, and C. orthopsilosis. Within the latter, at least two clearly distinct subspecies seem to be present among clinical isolates (Type 1 and Type 2). To gain insight into the genomic differences between these subspecies we undertook the sequencing of a clinical isolate classified as Type 1 and compared it to the available sequence of a Type 2 clinical strain. Unexpectedly, the analysis of the newly sequenced strain revealed a highly heterozygous genome, which we show to be the consequence of a hybridization event between both identified subspecies. This implicitly suggests that C. orthopsilosis is able to mate, a so-far unanswered question. The resulting hybrid shows a chimeric genome which maintains a similar gene dosage from both parental lineages and displays ongoing loss of heterozygosity. Several of the differences found between the gene content in both strains relate to virulent-related families, with the hybrid strain presenting a higher copy numbers of genes coding for efflux pumps or secreted lipases. Remarkably, two clinical strains isolated from distant geographical locations (Texas and Singapore) are descendants of the same hybrid line, raising the intriguing possibility of a relationship between the hybridization event and the global spread of a virulent clone.
    Genome Biology and Evolution 04/2014; 6(5). DOI:10.1093/gbe/evu082 · 4.23 Impact Factor
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