Browsing by Subject "Genes, Mating Type, Fungal"

Now showing 1 - 6 of 6
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    Analyses of pediatric isolates of Cryptococcus neoformans from South Africa.
    (J Clin Microbiol, 2011-01) Miglia, Kathleen J; Govender, Nelesh P; Rossouw, Jenny; Meiring, Susan; Mitchell, Thomas G; Group for Enteric, Respiratory and Meningeal Disease Surveillance in South Africa
    Compared to the incidence in adults, cryptococcosis is inexplicably rare among children, even in sub-Saharan Africa, which has the highest prevalence of coinfection with HIV and Cryptococcus neoformans. To explore any mycological basis for this age-related difference in the incidence of cryptococcosis, we investigated isolates of C. neoformans recovered from pediatric and adult patients during a 2-year period in South Africa. From reports to the Group for Enteric, Respiratory, and Meningeal Disease Surveillance in South Africa (GERMS-SA), we reviewed all cases of cryptococcosis in 2005 and 2006. We analyzed one isolate of C. neoformans from each of 82 pediatric patients (<15 years of age) and determined the multilocus sequence type (ST), mating type, ploidy, and allelic profile. This sample included isolates of all three molecular types of serotype A or C. neoformans var. grubii (molecular types VNI, VNII, and VNB) and one AD hybrid. Seventy-seven (94%) of the strains possessed the MATα mating type allele, and five were MATa. Seventy-five (91%) were haploid, and seven were diploid. A total of 24 different STs were identified. The ratios of each mating type and the proportion of haploids were comparable to those for the isolates that were obtained from 86 adult patients during the same period. Notably, the most prevalent pediatric ST was significantly associated with male patients. Overall, these pediatric isolates exhibited high genotypic diversity. They included a relatively large percentage of diploids and the rarely reported MATa mating type.
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    Comparative analyses of clinical and environmental populations of Cryptococcus neoformans in Botswana.
    (Mol Ecol, 2015-07) Chen, Yuan; Litvintseva, Anastasia P; Frazzitta, Aubrey E; Haverkamp, Miriam R; Wang, Liuyang; Fang, Charles; Muthoga, Charles; Mitchell, Thomas G; Perfect, John R
    Cryptococcus neoformans var. grubii (Cng) is the most common cause of fungal meningitis, and its prevalence is highest in sub-Saharan Africa. Patients become infected by inhaling airborne spores or desiccated yeast cells from the environment, where the fungus thrives in avian droppings, trees and soil. To investigate the prevalence and population structure of Cng in southern Africa, we analysed isolates from 77 environmental samples and 64 patients. We detected significant genetic diversity among isolates and strong evidence of geographic structure at the local level. High proportions of isolates with the rare MATa allele were observed in both clinical and environmental isolates; however, the mating-type alleles were unevenly distributed among different subpopulations. Nearly equal proportions of the MATa and MATα mating types were observed among all clinical isolates and in one environmental subpopulation from the eastern part of Botswana. As previously reported, there was evidence of both clonality and recombination in different geographic areas. These results provide a foundation for subsequent genomewide association studies to identify genes and genotypes linked to pathogenicity in humans.
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    Evolution of the sex-related locus and genomic features shared in microsporidia and fungi.
    (PLoS One, 2010-05-07) Lee, Soo Chan; Corradi, Nicolas; Doan, Sylvia; Dietrich, Fred S; Keeling, Patrick J; Heitman, Joseph
    BACKGROUND: Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that microsporidia share a particularly close evolutionary relationship with the zygomycetes. METHODOLOGY/PRINCIPAL FINDINGS: Here we expanded this analysis and also examined a putative sex-locus for variability between microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and microsporidians. One locus previously found to be conserved in many microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sex-related locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According to sequence-based phylogenetic analyses, the TPT and RNA helicase genes flanking the HMG genes are paralogous rather than orthologous between zygomycetes and microsporidians. CONCLUSION/SIGNIFICANCE: The unique genomic hallmarks between microsporidia and fungi are independent of sequence based phylogenetic comparisons and further contribute to define the borders of the fungal kingdom and support the classification of microsporidia as unusual derived fungi. And the sex/sex-related loci appear to have been subject to frequent gene conversion and translocations in microsporidia and zygomycetes.
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    Morphological and genomic characterization of Filobasidiella depauperata: a homothallic sibling species of the pathogenic cryptococcus species complex.
    (PLoS One, 2010-03-10) Rodriguez-Carres, Marianela; Findley, Keisha; Sun, Sheng; Dietrich, Fred S; Heitman, Joseph
    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.
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    Ratiometric GPCR signaling enables directional sensing in yeast.
    (PLoS biology, 2019-10-17) Henderson, Nicholas T; Pablo, Michael; Ghose, Debraj; Clark-Cotton, Manuella R; Zyla, Trevin R; Nolen, James; Elston, Timothy C; Lew, Daniel J
    Accurate detection of extracellular chemical gradients is essential for many cellular behaviors. Gradient sensing is challenging for small cells, which can experience little difference in ligand concentrations on the up-gradient and down-gradient sides of the cell. Nevertheless, the tiny cells of the yeast Saccharomyces cerevisiae reliably decode gradients of extracellular pheromones to find their mates. By imaging the behavior of polarity factors and pheromone receptors, we quantified the accuracy of initial polarization during mating encounters. We found that cells bias the orientation of initial polarity up-gradient, even though they have unevenly distributed receptors. Uneven receptor density means that the gradient of ligand-bound receptors does not accurately reflect the external pheromone gradient. Nevertheless, yeast cells appear to avoid being misled by responding to the fraction of occupied receptors rather than simply the concentration of ligand-bound receptors. Such ratiometric sensing also serves to amplify the gradient of active G protein. However, this process is quite error-prone, and initial errors are corrected during a subsequent indecisive phase in which polarity clusters exhibit erratic mobile behavior.
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    Structure, function, and phylogeny of the mating locus in the Rhizopus oryzae complex.
    (PLoS One, 2010-12-09) Gryganskyi, AP; Lee, SC; Litvintseva, AP; Smith, ME; Bonito, G; Porter, TM; Anishchenko, IM; Heitman, J; Vilgalys, R
    The Rhizopus oryzae species complex is a group of zygomycete fungi that are common, cosmopolitan saprotrophs. Some strains are used beneficially for production of Asian fermented foods but they can also act as opportunistic human pathogens. Although R. oryzae reportedly has a heterothallic (+/-) mating system, most strains have not been observed to undergo sexual reproduction and the genetic structure of its mating locus has not been characterized. Here we report on the mating behavior and genetic structure of the mating locus for 54 isolates of the R. oryzae complex. All 54 strains have a mating locus similar in overall organization to Phycomyces blakesleeanus and Mucor circinelloides (Mucoromycotina, Zygomycota). In all of these fungi, the minus (-) allele features the SexM high mobility group (HMG) gene flanked by an RNA helicase gene and a TP transporter gene (TPT). Within the R. oryzae complex, the plus (+) mating allele includes an inserted region that codes for a BTB/POZ domain gene and the SexP HMG gene. Phylogenetic analyses of multiple genes, including the mating loci (HMG, TPT, RNA helicase), ITS1-5.8S-ITS2 rDNA, RPB2, and LDH genes, identified two distinct groups of strains. These correspond to previously described sibling species R. oryzae sensu stricto and R. delemar. Within each species, discordant gene phylogenies among multiple loci suggest an outcrossing population structure. The hypothesis of random-mating is also supported by a 50:50 ratio of plus and minus mating types in both cryptic species. When crossed with tester strains of the opposite mating type, most isolates of R. delemar failed to produce zygospores, while isolates of R. oryzae produced sterile zygospores. In spite of the reluctance of most strains to mate in vitro, the conserved sex locus structure and evidence for outcrossing suggest that a normal sexual cycle occurs in both species.