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Nováková A, Hubka V, Dudová Z, Matsuzawa T, Kubátová A, Yaguchi T, Kolařík M. New species in Aspergillus section Fumigati from reclamation sites in Wyoming (U.S.A.) and revision of A. viridinutans complex. FUNGAL DIVERS 2013. [DOI: 10.1007/s13225-013-0262-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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202
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Chi MH, Craven KD. Oxygen and an extracellular phase transition independently control central regulatory genes and conidiogenesis in Aspergillus fumigatus. PLoS One 2013; 8:e74805. [PMID: 24040343 PMCID: PMC3764054 DOI: 10.1371/journal.pone.0074805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 08/06/2013] [Indexed: 11/18/2022] Open
Abstract
Conidiogenesis is the primary process for asexual reproduction in filamentous fungi. As the conidia resulting from the conidiogenesis process are primarily disseminated via air currents and/or water, an outstanding question has been how fungi recognize aerial environments suitable for conidial development. In this study, we documented the somewhat complex development of the conidia-bearing structures, termed conidiophores, from several Aspergillus species in a subsurface (gel-phase) layer of solid media. A subset of the isolates studied was able to develop conidiophores in a gel-phase environment, but exposure to the aeriform environment was required for the terminal developmental transition from phialide cells to conidia. The remaining Aspergilli could not initiate the conidiogenesis process until they were exposed to the aeriform environment. Our observations of conidiophore development in high or low oxygen conditions in both aeriform and gel-phase environments revealed that oxygen and the aeriform state are positive environmental factors for inducing conidiogenesis in most of the aspergilli tested in this study. Transcriptional analysis using A. fumigatus strain AF293 confined to either the aeriform or gel-phase environments revealed that expression of a key regulatory gene for conidiophore development (AfubrlA) is facilitated by oxygen while expression of another regulatory gene controlling conidia formation from phialides (AfuabaA) was repressed regardless of oxygen levels in the gel-embedded environment. Furthermore, by comparing the developmental behavior of conidiation-defective mutants lacking genes controlling various regulatory checkpoints throughout the conidiogenesis pathway, we propose that this aerial response by the fungus requires both oxygen and the phase transition (solid to aeriform), with these environmental signals integrating into the upstream regulatory pathway and central regulatory pathway of conidiogenesis, respectively. Our findings provide not only novel insight into how fungi respond to an aerial environment to trigger development for airborne conidia production but also the relationship between environmental factors and conidiogenesis regulation in aspergilli.
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Affiliation(s)
- Myoung-Hwan Chi
- Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma, United States of America
| | - Kelly D. Craven
- Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma, United States of America
- * E-mail:
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203
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Holland SL, Reader T, Dyer PS, Avery SV. Phenotypic heterogeneity is a selected trait in natural yeast populations subject to environmental stress. Environ Microbiol 2013; 16:1729-40. [PMID: 24000788 PMCID: PMC4231229 DOI: 10.1111/1462-2920.12243] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 07/31/2013] [Accepted: 08/03/2013] [Indexed: 11/28/2022]
Abstract
Populations of genetically uniform microorganisms exhibit phenotypic heterogeneity, where individual cells have varying phenotypes. Such phenotypes include fitness-determining traits. Phenotypic heterogeneity has been linked to increased population-level fitness in laboratory studies, but its adaptive significance for wild microorganisms in the natural environment is unknown. Here, we addressed this by testing heterogeneity in yeast isolates from diverse environmental sites, each polluted with a different principal contaminant, as well as from corresponding control locations. We found that cell-to-cell heterogeneity (in resistance to the appropriate principal pollutant) was prevalent in the wild yeast isolates. Moreover, isolates with the highest heterogeneity were consistently observed in the polluted environments, indicating that heterogeneity is positively related to survival in adverse conditions in the wild. This relationship with survival was stronger than for the property of mean resistance (IC(50)) of an isolate. Therefore, heterogeneity could be the major determinant of microbial survival in adverse conditions. Indeed, growth assays indicated that isolates with high heterogeneities had a significant competitive advantage during stress. Analysis of yeasts after cultivation for ≥ 500 generations additionally showed that high heterogeneity evolved as a heritable trait during stress. The results showed that environmental stress selects for wild microorganisms with high levels of phenotypic heterogeneity.
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Affiliation(s)
- Sara L Holland
- School of Life Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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204
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Netíková L, Bogusch P, Heneberg P. Czech Ethanol-Free Propolis Extract Displays Inhibitory Activity against a Broad Spectrum of Bacterial and Fungal Pathogens. J Food Sci 2013; 78:M1421-9. [DOI: 10.1111/1750-3841.12230] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 06/24/2013] [Indexed: 12/21/2022]
Affiliation(s)
- Ladislava Netíková
- Faculty of Science, Univ. of Hradec Králové; Rokitanského 62; CZ-500 03 Hradec Králové; Czech Republic
| | - Petr Bogusch
- Faculty of Science, Univ. of Hradec Králové; Rokitanského 62; CZ-500 03 Hradec Králové; Czech Republic
| | - Petr Heneberg
- Third Faculty of Medicine, Charles Univ. in Prague; Ruská 87; CZ-100 00 Prague; Czech Republic
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205
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Stewart JE, Thomas KA, Lawrence CB, Dang H, Pryor BM, Timmer LMP, Peever TL. Signatures of recombination in clonal lineages of the citrus brown spot pathogen, Alternaria alternata sensu lato. PHYTOPATHOLOGY 2013; 103:741-749. [PMID: 23441968 DOI: 10.1094/phyto-08-12-0211-r] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Most Alternaria spp. are considered asexual but recent molecular evolution analyses of Alternaria mating-type genes show that the mating locus is under strong purifying selection, indicating a possible role in sexual reproduction. The objective of this study was to determine the mode of reproduction of an Alternaria alternata sensu lato population causing citrus brown spot in central Florida. Mating type of each isolate was determined, and isolates were sequenced at six putatively unlinked loci. Three genetically distinct subpopulations (SH1, SH4A, and SH4B) were identified using network and Bayesian population structure analyses. Results demonstrate that most subpopulations of A. alternata associated with citrus are clonal but some have the ability to extensively recombine through a cryptic sexual cycle or parasexual cycle. Although isolates were sampled in close physical proximity (≈2,500-m² area), we were able to reject a random mating model using multilocus gametic disequilibrium tests for two subpopulations, SH1 and SH4B, suggesting that these subpopulations were predominantly asexual. However, three recombination events were identified in SH1 and SH4B and localized to individuals of opposite mating type, possibly indicating meiotic recombination. In contrast, in the third subpopulation (SH4A), where only one mating type was present, extensive reticulation was evident in network analyses, and multilocus gametic disequilibrium tests were consistent with recombination. Recombination among isolates of the same mating type suggests that a nonmeiotic mechanism of recombination such as the parasexual cycle may be operating in this subpopulation. The level of gene flow detected among subpopulations does not appear to be sufficient to prevent differentiation, and perhaps future speciation, of these A. alternata subpopulations.
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Affiliation(s)
- Jane E Stewart
- Department of Plant Pathology, Washington State University, Pullman, USA.
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206
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Aspergillus felis sp. nov., an emerging agent of invasive aspergillosis in humans, cats, and dogs. PLoS One 2013; 8:e64871. [PMID: 23798996 PMCID: PMC3683053 DOI: 10.1371/journal.pone.0064871] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 04/17/2013] [Indexed: 11/19/2022] Open
Abstract
We describe a novel heterothallic species in Aspergillus section Fumigati, namely A. felis (neosartorya-morph) isolated from three host species with invasive aspergillosis including a human patient with chronic invasive pulmonary aspergillosis, domestic cats with invasive fungal rhinosinusitis and a dog with disseminated invasive aspergillosis. Disease in all host species was often refractory to aggressive antifungal therapeutic regimens. Four other human isolates previously reported as A. viridinutans were identified as A. felis on comparative sequence analysis of the partial β-tubulin and/or calmodulin genes. A. felis is a heterothallic mold with a fully functioning reproductive cycle, as confirmed by mating-type analysis, induction of teleomorphs within 7 to 10 days in vitro and ascospore germination. Phenotypic analyses show that A. felis can be distinguished from the related species A. viridinutans by its ability to grow at 45°C and from A. fumigatus by its inability to grow at 50°C. Itraconazole and voriconazole cross-resistance was common in vitro.
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207
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Horn BW, Olarte RA, Peterson SW, Carbone I. Sexual reproduction in Aspergillus tubingensis from section Nigri. Mycologia 2013; 105:1153-63. [PMID: 23709489 DOI: 10.3852/13-101] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A sclerotium-forming member of Aspergillus section Nigri was sampled from a population in a single field in North Carolina, USA, and identified as A. tubingensis based on genealogical concordance analysis. Aspergillus tubingensis was shown to be heterothallic, with individual strains containing either a MAT1-1 or MAT1-2 mating-type gene. Strains of opposite mating type were crossed on mixed cereal agar and incubated for 5-6 months. Stromata typically formed 1-2 indehiscent ascocarps containing asci and ascospores within the pseudo-parenchymatous matrix in a manner similar to the Petromyces sexual stage from section Flavi, which is closely related to section Nigri. Ascospores of A. tubingensis differed from those of section Flavi species in the reticulate ornamentation of ascospores and the presence of two crests that form an equatorial furrow. Sexual reproduction in A. tubingensis may be useful for enhancing enzyme and organic acid production through recombination-mediated genetic engineering of industrial strains.
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Affiliation(s)
- Bruce W Horn
- National Peanut Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Dawson, Georgia 39842
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208
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Discovery of a sexual cycle in Aspergillus lentulus, a close relative of A. fumigatus. EUKARYOTIC CELL 2013; 12:962-9. [PMID: 23650087 PMCID: PMC3697472 DOI: 10.1128/ec.00040-13] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Aspergillus lentulus was described in 2005 as a new species within the A. fumigatus sensu lato complex. It is an opportunistic human pathogen causing invasive aspergillosis with high mortality rates, and it has been isolated from clinical and environmental sources. The species is morphologically nearly identical to A. fumigatus sensu stricto, and this similarity has resulted in their frequent misidentification. Comparative studies show that A. lentulus has some distinguishing growth features and decreased in vitro susceptibility to several antifungal agents, including amphotericin B and caspofungin. Similar to the once-presumed-asexual A. fumigatus, it has only been known to reproduce mitotically. However, we now show that A. lentulus has a heterothallic sexual breeding system. A PCR-based mating-type diagnostic detected isolates of either the MAT1-1 or MAT1-2 genotype, and examination of 26 worldwide clinical and environmental isolates revealed similar ratios of the two mating types (38% versus 62%, respectively). MAT1-1 and MAT1-2 idiomorph regions were analyzed, revealing the presence of characteristic alpha and high-mobility-group (HMG) domain genes, together with other more unusual features such as a MAT1-2-4 gene. We then demonstrated that A. lentulus possesses a functional sexual cycle with mature cleistothecia, containing heat-resistant ascospores, being produced after 3 weeks of incubation. Recombination was confirmed using molecular markers. However, isolates of A. lentulus failed to cross with highly fertile strains of A. fumigatus, demonstrating reproductive isolation between these sibling species. The discovery of the A. lentulus sexual stage has significant implications for the management of drug resistance and control of invasive aspergillosis associated with this emerging fungal pathogen.
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209
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Nieuwenhuis BPS, Aanen DK. Sexual selection in fungi. J Evol Biol 2013; 25:2397-411. [PMID: 23163326 DOI: 10.1111/jeb.12017] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Revised: 09/07/2012] [Accepted: 09/07/2012] [Indexed: 12/14/2022]
Abstract
The significance of sexual selection, the component of natural selection associated with variation in mating success, is well established for the evolution of animals and plants, but not for the evolution of fungi. Even though fungi do not have separate sexes, most filamentous fungi mate in a hermaphroditic fashion, with distinct sex roles, that is, investment in large gametes (female role) and fertilization by other small gametes (male role). Fungi compete to fertilize, analogous to 'male-male' competition, whereas they can be selective when being fertilized, analogous to female choice. Mating types, which determine genetic compatibility among fungal gametes, are important for sexual selection in two respects. First, genes at the mating-type loci regulate different aspects of mating and thus can be subject to sexual selection. Second, for sexual selection, not only the two sexes (or sex roles) but also the mating types can form the classes, the members of which compete for access to members of the other class. This is significant if mating-type gene products are costly, thus signalling genetic quality according to Zahavi's handicap principle. We propose that sexual selection explains various fungal characteristics such as the observed high redundancy of pheromones at the B mating-type locus of Agaricomycotina, the occurrence of multiple types of spores in Ascomycotina or the strong pheromone signalling in yeasts. Furthermore, we argue that fungi are good model systems to experimentally study fundamental aspects of sexual selection, due to their fast generation times and high diversity of life cycles and mating systems.
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Affiliation(s)
- B P S Nieuwenhuis
- Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands.
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210
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Abstract
Our understanding of the interactions between normal skin microbiota and the human host has been greatly extended by recent investigations. In their recent study in mBio, A. Gioti et al. (mBio 4[1]:e00572-12, 2013) sequenced the genome of the atopic eczema-associated yeast, Malassezia sympodialis, and compared its gene content and organization with that of Malassezia globosa, a species implicated in dandruff. Their findings were also contrasted with those previously obtained for Ustilago maydis, which is a close relative but ecologically distinct plant parasite. Besides gaining additional insight into key host-specific adaptations and the particular function and molecular evolution of allergens related to atopic eczema, Gioti et al. also uncovered several lines of evidence that elegantly suggest the presence of an extant sexual cycle, with important implications in disease.
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211
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Krijgsheld P, Bleichrodt R, van Veluw G, Wang F, Müller W, Dijksterhuis J, Wösten H. Development in Aspergillus. Stud Mycol 2013; 74:1-29. [PMID: 23450714 PMCID: PMC3563288 DOI: 10.3114/sim0006] [Citation(s) in RCA: 235] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The genus Aspergillus represents a diverse group of fungi that are among the most abundant fungi in the world. Germination of a spore can lead to a vegetative mycelium that colonizes a substrate. The hyphae within the mycelium are highly heterogeneous with respect to gene expression, growth, and secretion. Aspergilli can reproduce both asexually and sexually. To this end, conidiophores and ascocarps are produced that form conidia and ascospores, respectively. This review describes the molecular mechanisms underlying growth and development of Aspergillus.
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Affiliation(s)
- P. Krijgsheld
- Microbiology and Kluyver Centre for Genomics of Industrial Fermentations, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - R. Bleichrodt
- Microbiology and Kluyver Centre for Genomics of Industrial Fermentations, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - G.J. van Veluw
- Microbiology and Kluyver Centre for Genomics of Industrial Fermentations, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - F. Wang
- Microbiology and Kluyver Centre for Genomics of Industrial Fermentations, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - W.H. Müller
- Biomolecular Imaging, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - J. Dijksterhuis
- Applied and Industrial Mycology, CBS-KNAW Fungal Biodiversity Centre, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands
| | - H.A.B. Wösten
- Microbiology and Kluyver Centre for Genomics of Industrial Fermentations, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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212
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Gabriel F, D'Almeida M, Albert O, Fitton-Ouhabi V, Noël T, Accoceberry I. A disseminated infection with the antifungal-multiresistant teleomorphic fungus Neocosmospora vasinfecta in a patient with acute B-lymphoblastic leukemia. Med Mycol Case Rep 2013; 2:44-7. [PMID: 24432214 DOI: 10.1016/j.mmcr.2013.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 01/08/2013] [Indexed: 12/28/2022] Open
Abstract
We report on a fatal invasive infection due to the ascomycetous fungus Neocosmospora vasinfecta, in a 20-year-old European patient suffering from an acute lymphoblastic leukemia. The infection could not be controlled by a bitherapy combining liposomal amphotericin B and voriconazole. This is the second case of disseminated infection reported with this unusual fungus, which develops under its teleomorphic state, is fully resistant to all systemic antifungals, and which is known to live in tropical countries.
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Affiliation(s)
- Frédéric Gabriel
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France ; Centre Hospitalier Universitaire de Bordeaux, Laboratoire de Parasitologie-Mycologie, F-33000 Bordeaux, France
| | - Mahussi D'Almeida
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France ; Centre Hospitalier Universitaire de Bordeaux, Laboratoire de Parasitologie-Mycologie, F-33000 Bordeaux, France
| | - Olivier Albert
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France ; Centre Hospitalier Universitaire de Bordeaux, Laboratoire de Parasitologie-Mycologie, F-33000 Bordeaux, France
| | - Valérie Fitton-Ouhabi
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Thierry Noël
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Isabelle Accoceberry
- Université de Bordeaux, Microbiologie Fondamentale et Pathogénicité UMR 5234, F-33000 Bordeaux, France ; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France ; Centre Hospitalier Universitaire de Bordeaux, Laboratoire de Parasitologie-Mycologie, F-33000 Bordeaux, France
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213
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Abstract
Over 450 peer-reviewed papers containing the keyword Aspergillus fumigatus were published in 2011. Although this method may be an impossible task, I have selected three clusters of papers describing exciting recent advances in research on A. fumigatus. The first is the novel approach of in vivo imagining of experimental aspergillosis by the use of (68) Ga-labeled siderophores, internalized by the fungus, and detected via positron emission tomography to image the site infection. This work may lead to improved diagnosis of aspergillosis. The second important finding is that NK lymphocytes, not thought to be involved in host resistance to aspergillosis, can kill aspergilli through direct contact, either through perforin or interferon-γ, or both. The third area pertains to a novel first-in-class antifungal drug, E1210 (Eisai), which inhibits GPI anchoring of fungal-associated cell wall proteins. Thus far, it shows promising in vitro activity against a broad range of fungi including Aspergilli, as well as those that are difficult to treat with currently available therapies. Overall, these three areas demonstrate the exciting promise, progress, and utility of basic research against A. fumigatus.
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Affiliation(s)
- Nir Osherov
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine Ramat-Aviv, Tel-Aviv, Israel.
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214
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Riley R, Corradi N. Searching for clues of sexual reproduction in the genomes of arbuscular mycorrhizal fungi. FUNGAL ECOL 2013. [DOI: 10.1016/j.funeco.2012.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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215
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Chooi YH, Fang J, Liu H, Filler SG, Wang P, Tang Y. Genome mining of a prenylated and immunosuppressive polyketide from pathogenic fungi. Org Lett 2013; 15:780-3. [PMID: 23368997 DOI: 10.1021/ol303435y] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Activation of the polycyclic polyketide prenyltransferase (pcPTase)-containing silent clusters in Aspergillus fumigatus and Neosartorya fischeri led to isolation of a new metabolite neosartoricin (3). The structure of 3 was solved by X-ray crystallography and NMR to be a prenylated anthracenone. 3 exhibits T-cell antiproliferative activity with an IC(50) of 3 μM, suggestive of a physiological role as an immunosuppressive agent.
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Affiliation(s)
- Yit-Heng Chooi
- Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, California 90066, United States
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216
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Sexual reproduction and mating-type-mediated strain development in the penicillin-producing fungus Penicillium chrysogenum. Proc Natl Acad Sci U S A 2013; 110:1476-81. [PMID: 23307807 DOI: 10.1073/pnas.1217943110] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Penicillium chrysogenum is a filamentous fungus of major medical and historical importance, being the original and present-day industrial source of the antibiotic penicillin. The species has been considered asexual for more than 100 y, and despite concerted efforts, it has not been possible to induce sexual reproduction, which has prevented sexual crosses being used for strain improvement. However, using knowledge of mating-type (MAT) gene organization, we now describe conditions under which a sexual cycle can be induced leading to production of meiotic ascospores. Evidence of recombination was obtained using both molecular and phenotypic markers. The identified heterothallic sexual cycle was used for strain development purposes, generating offspring with novel combinations of traits relevant to penicillin production. Furthermore, the MAT1-1-1 mating-type gene, known primarily for a role in governing sexual identity, was also found to control transcription of a wide range of genes with biotechnological relevance including those regulating penicillin production, hyphal morphology, and conidial formation. These discoveries of a sexual cycle and MAT gene function are likely to be of broad relevance for manipulation of other asexual fungi of economic importance.
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217
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Morton CO, Bouzani M, Loeffler J, Rogers TR. Direct interaction studies between Aspergillus fumigatus and human immune cells; what have we learned about pathogenicity and host immunity? Front Microbiol 2012; 3:413. [PMID: 23264771 PMCID: PMC3525292 DOI: 10.3389/fmicb.2012.00413] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 11/15/2012] [Indexed: 12/24/2022] Open
Abstract
Invasive aspergillosis is a significant threat to health and is a major cause of mortality in immunocompromised individuals. Understanding the interaction between the fungus and the immune system is important in determining how the immunocompetent host remains disease free. Several studies examining the direct interaction between Aspergillus fumigatus and purified innate immune cells have been conducted to measure the responses of both the host cells and the pathogen. It has been revealed that innate immune cells have different modes of action ranging from effective fungal killing by neutrophils to the less aggressive response of dendritic cells. Natural killer cells do not phagocytose the fungus unlike the other innate immune cells mentioned but appear to mediate their antifungal effect through the release of gamma interferon. Transcriptional analysis of A. fumigatus interacting with these cells has indicated that it can adapt to the harsh microenvironment of the phagosome and produces toxins, ribotoxin and gliotoxin, that can induce cell death in the majority of innate immune cells. These data point toward potential novel antifungal treatments including the use of innate immune cells as antifungal vaccines.
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Affiliation(s)
- Charles O Morton
- School of Science and Health, University of Western Sydney Campbelltown, NSW, Australia
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218
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Discovery of a HapE mutation that causes azole resistance in Aspergillus fumigatus through whole genome sequencing and sexual crossing. PLoS One 2012; 7:e50034. [PMID: 23226235 PMCID: PMC3511431 DOI: 10.1371/journal.pone.0050034] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 10/15/2012] [Indexed: 01/10/2023] Open
Abstract
Azole compounds are the primary therapy for patients with diseases caused by Aspergillus fumigatus. However, prolonged treatment may cause resistance to develop, which is associated with treatment failure. The azole target cyp51A is a hotspot for mutations that confer phenotypic resistance, but in an increasing number of resistant isolates the underlying mechanism remains unknown. Here, we report the discovery of a novel resistance mechanism, caused by a mutation in the CCAAT-binding transcription factor complex subunit HapE. From one patient, four A. fumigatus isolates were serially collected. The last two isolates developed an azole resistant phenotype during prolonged azole therapy. Because the resistant isolates contained a wild type cyp51A gene and the isolates were isogenic, the complete genomes of the last susceptible isolate and the first resistant isolate (taken 17 weeks apart) were sequenced using Illumina technology to identify the resistance conferring mutation. By comparing the genome sequences to each other as well as to two A. fumigatus reference genomes, several potential non-synonymous mutations in protein-coding regions were identified, six of which could be confirmed by PCR and Sanger sequencing. Subsequent sexual crossing experiments showed that resistant progeny always contained a P88L substitution in HapE, while the presence of the other five mutations did not correlate with resistance in the progeny. Cloning the mutated hapE gene into the azole susceptible akuB(KU80) strain showed that the HapE P88L mutation by itself could confer the resistant phenotype. This is the first time that whole genome sequencing and sexual crossing strategies have been used to find the genetic basis of a trait of interest in A. fumigatus. The discovery may help understand alternate pathways for azole resistance in A. fumigatus with implications for the molecular diagnosis of resistance and drug discovery.
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Ropars J, Dupont J, Fontanillas E, Rodríguez de la Vega RC, Malagnac F, Coton M, Giraud T, López-Villavicencio M. Sex in cheese: evidence for sexuality in the fungus Penicillium roqueforti. PLoS One 2012. [PMID: 23185400 PMCID: PMC3504111 DOI: 10.1371/journal.pone.0049665] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although most eukaryotes reproduce sexually at some moment of their life cycle, as much as a fifth of fungal species were thought to reproduce exclusively asexually. Nevertheless, recent studies have revealed the occurrence of sex in some of these supposedly asexual species. For industrially relevant fungi, for which inoculums are produced by clonal-subcultures since decades, the potentiality for sex is of great interest for strain improvement strategies. Here, we investigated the sexual capability of the fungus Penicillium roqueforti, used as starter for blue cheese production. We present indirect evidence suggesting that recombination could be occurring in this species. The screening of a large sample of strains isolated from diverse substrates throughout the world revealed the existence of individuals of both mating types, even in the very same cheese. The MAT genes, involved in fungal sexual compatibility, appeared to evolve under purifying selection, suggesting that they are still functional. The examination of the recently sequenced genome of the FM 164 cheese strain enabled the identification of the most important genes known to be involved in meiosis, which were found to be highly conserved. Linkage disequilibria were not significant among three of the six marker pairs and 11 out of the 16 possible allelic combinations were found in the dataset. Finally, the detection of signatures of repeat induced point mutations (RIP) in repeated sequences and transposable elements reinforces the conclusion that P. roqueforti underwent more or less recent sex events. In this species of high industrial importance, the induction of a sexual cycle would open the possibility of generating new genotypes that would be extremely useful to diversify cheese products.
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Affiliation(s)
- Jeanne Ropars
- Department Systématique et Evolution, Origine, Structure, Evolution de la Biodiversité, UMR 7205 CNRS-MNHN, Muséum National d'Histoire Naturelle, Paris, France.
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Yang E, Hulse AM, Cai JJ. Evolutionary Analysis of Sequence Divergence and Diversity of Duplicate Genes in Aspergillus fumigatus. Evol Bioinform Online 2012; 8:623-44. [PMID: 23225993 PMCID: PMC3510868 DOI: 10.4137/ebo.s10372] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Gene duplication as a major source of novel genetic material plays an important role in evolution. In this study, we focus on duplicate genes in Aspergillus fumigatus, a ubiquitous filamentous fungus causing life-threatening human infections. We characterize the extent and evolutionary patterns of the duplicate genes in the genome of A. fumigatus. Our results show that A. fumigatus contains a large amount of duplicate genes with pronounced sequence divergence between two copies, and approximately 10% of them diverge asymmetrically, i.e. two copies of a duplicate gene pair diverge at significantly different rates. We use a Bayesian approach of the McDonald-Kreitman test to infer distributions of selective coefficients γ(=2N(e)s) and find that (1) the values of γ for two copies of duplicate genes co-vary positively and (2) the average γ for the two copies differs between genes from different gene families. This analysis highlights the usefulness of combining divergence and diversity data in studying the evolution of duplicate genes. Taken together, our results provide further support and refinement to the theories of gene duplication. Through characterizing the duplicate genes in the genome of A. fumigatus, we establish a computational framework, including parameter settings and methods, for comparative study of genetic redundancy and gene duplication between different fungal species.
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Affiliation(s)
- Ence Yang
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas, USA
| | - Amanda M. Hulse
- Interdisciplinary Program in Genetics, Texas A&M University, College Station, Texas USA
| | - James J. Cai
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas, USA
- Interdisciplinary Program in Genetics, Texas A&M University, College Station, Texas USA
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Molecular and morphological data support the existence of a sexual cycle in species of the genus Paracoccidioides. EUKARYOTIC CELL 2012; 12:380-9. [PMID: 23125354 DOI: 10.1128/ec.05052-11] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The genus Paracoccidioides includes the thermodimorphic species Paracoccidioides brasiliensis and P. lutzii, both of which are etiologic agents of paracoccidioidomycosis, a systemic mycosis that affects humans in Latin America. Despite the common occurrence of a sexual stage among closely related fungi, this has not been observed with Paracoccidioides species, which have thus been considered asexual. Molecular evolutionary studies revealed recombination events within isolated populations of the genus Paracoccidioides, suggesting the possible existence of a sexual cycle. Comparative genomic analysis of all dimorphic fungi and Saccharomyces cerevisiae demonstrated the presence of conserved genes involved in sexual reproduction, including those encoding mating regulators such as MAT, pheromone receptors, pheromone-processing enzymes, and mating signaling regulators. The expression of sex-related genes in the yeast and mycelial phases of both Paracoccidioides species was also detected by real-time PCR, with nearly all of these genes being expressed preferentially in the filamentous form of the pathogens. In addition, the expression of sex-related genes was responsive to the putative presence of pheromone in the supernatants obtained from previous cocultures of strains of two different mating types. In vitro crossing of isolates of different mating types, discriminated by phylogenetic analysis of the α-box (MAT1-1) and the high-mobility-group (HMG) domain (MAT1-2), led to the identification of the formation of young ascocarps with constricted coiled hyphae related to the initial stage of mating. These genomic and morphological analyses strongly support the existence of a sexual cycle in species of the genus Paracoccidioides.
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Abstract
Dermatophytes are a uniquely pathogenic group of fungi that cause most common fungal infections globally. The major cause of athlete’s foot is Trichophyton rubrum, a pathogen of human skin. A recent paper in this journal reported the sequencing and analysis of five additional genome sequences, including that of Trichophyton rubrum. These five join the existing two additional genome sequences to bring the total to seven dermatophyte genome sequences, a notable milestone in the study of these fungi. These additional genomes set the stage for future genome-supported studies on the biology, pathogenicity, and host specificity of this important group of pathogens. To predict how this future might play out, we review the history of Aspergillus genomics since the initial publication of the first three Aspergillus genome sequences in 2005, an event that stimulated important studies of the pathogenic Aspergillus species. From these 7 years of Aspergillus history, we offer some speculation on the future of dermatophyte studies supported by the genome sequences given the similarities, differences, and relative levels of support for studies in these two groups of fungi and the diseases they cause.
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VeA regulates conidiation, gliotoxin production, and protease activity in the opportunistic human pathogen Aspergillus fumigatus. EUKARYOTIC CELL 2012; 11:1531-43. [PMID: 23087369 DOI: 10.1128/ec.00222-12] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Invasive aspergillosis by Aspergillus fumigatus is a leading cause of infection-related mortality in immunocompromised patients. In this study, we show that veA, a major conserved regulatory gene that is unique to fungi, is necessary for normal morphogenesis in this medically relevant fungus. Although deletion of veA results in a strain with reduced conidiation, overexpression of this gene further reduced conidial production, indicating that veA has a major role as a regulator of development in A. fumigatus and that normal conidiation is only sustained in the presence of wild-type VeA levels. Furthermore, our studies revealed that veA is a positive regulator in the production of gliotoxin, a secondary metabolite known to be a virulent factor in A. fumigatus. Deletion of veA resulted in a reduction of gliotoxin production with respect to that of the wild-type control. This reduction in toxin coincided with a decrease in gliZ and gliP expression, which is necessary for gliotoxin biosynthesis. Interestingly, veA also influences protease activity in this organism. Specifically, deletion of veA resulted in a reduction of protease activity; this is the first report of a veA homolog with a role in controlling fungal hydrolytic activity. Although veA affects several cellular processes in A. fumigatus, pathogenicity studies in a neutropenic mouse infection model indicated that veA is dispensable for virulence.
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224
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Gibbons JG, Rokas A. The function and evolution of the Aspergillus genome. Trends Microbiol 2012; 21:14-22. [PMID: 23084572 DOI: 10.1016/j.tim.2012.09.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Revised: 09/20/2012] [Accepted: 09/24/2012] [Indexed: 10/27/2022]
Abstract
Species in the filamentous fungal genus Aspergillus display a wide diversity of lifestyles and are of great importance to humans. The decoding of genome sequences from a dozen species that vary widely in their degree of evolutionary affinity has galvanized studies of the function and evolution of the Aspergillus genome in clinical, industrial, and agricultural environments. Here, we synthesize recent key findings that shed light on the architecture of the Aspergillus genome, on the molecular foundations of the genus' astounding dexterity and diversity in secondary metabolism, and on the genetic underpinnings of virulence in Aspergillus fumigatus, one of the most lethal fungal pathogens. Many of these insights dramatically expand our knowledge of fungal and microbial eukaryote genome evolution and function and argue that Aspergillus constitutes a superb model clade for the study of functional and comparative genomics.
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Affiliation(s)
- John G Gibbons
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
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225
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Arabatzis M, Velegraki A. Sexual reproduction in the opportunistic human pathogen Aspergillus terreus. Mycologia 2012; 105:71-9. [PMID: 23074177 DOI: 10.3852/11-426] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Aspergillus terreus has a worldwide distribution in soil, constitutes the third most important cause of invasive aspergillosis in humans and is classically regarded as a strictly asexual species. Strains of A. terreus were characterized by ITS, β-tubulin and calmodulin sequences. Mating type was identified by amplifying and sequencing MAT1-1 and MAT1-2 genes. One MAT1-2 strain produced hyphal masses when crossed with four MAT1-1 strains on mixed cereal agar after 3 wk at 37 C. Cleistothecia formed inside the hyphal masses and produced asci containing smooth-walled ascospores with an equatorial protuberance. This is the first report of sexual reproduction in A. terreus.
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Affiliation(s)
- Michael Arabatzis
- Department of Microbiology, National and Kapodistrian University of Athens, Athens, Greece.
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226
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Henk DA, Shahar-Golan R, Devi KR, Boyce KJ, Zhan N, Fedorova ND, Nierman WC, Hsueh PR, Yuen KY, Sieu TPM, Kinh NV, Wertheim H, Baker SG, Day JN, Vanittanakom N, Bignell EM, Andrianopoulos A, Fisher MC. Clonality despite sex: the evolution of host-associated sexual neighborhoods in the pathogenic fungus Penicillium marneffei. PLoS Pathog 2012; 8:e1002851. [PMID: 23055919 PMCID: PMC3464222 DOI: 10.1371/journal.ppat.1002851] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 06/25/2012] [Indexed: 12/04/2022] Open
Abstract
Molecular genetic approaches typically detect recombination in microbes regardless of assumed asexuality. However, genetic data have shown the AIDS-associated pathogen Penicillium marneffei to have extensive spatial genetic structure at local and regional scales, and although there has been some genetic evidence that a sexual cycle is possible, this haploid fungus is thought to be genetically, as well as morphologically, asexual in nature because of its highly clonal population structure. Here we use comparative genomics, experimental mixed-genotype infections, and population genetic data to elucidate the role of recombination in natural populations of P. marneffei. Genome wide comparisons reveal that all the genes required for meiosis are present in P. marneffei, mating type genes are arranged in a similar manner to that found in other heterothallic fungi, and there is evidence of a putatively meiosis-specific mutational process. Experiments suggest that recombination between isolates of compatible mating types may occur during mammal infection. Population genetic data from 34 isolates from bamboo rats in India, Thailand and Vietnam, and 273 isolates from humans in China, India, Thailand, and Vietnam show that recombination is most likely to occur across spatially and genetically limited distances in natural populations resulting in highly clonal population structure yet sexually reproducing populations. Predicted distributions of three different spatial genetic clusters within P. marneffei overlap with three different bamboo rat host distributions suggesting that recombination within hosts may act to maintain population barriers within P. marneffei.
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Affiliation(s)
- Daniel A Henk
- Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, London, United Kingdom.
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227
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Gomes-Rezende JA, Gomes-Alves AG, Menino JF, Coelho MA, Ludovico P, Gonçalves P, Sturme MHJ, Rodrigues F. Functionality of the Paracoccidioides mating α-pheromone-receptor system. PLoS One 2012; 7:e47033. [PMID: 23056569 PMCID: PMC3464258 DOI: 10.1371/journal.pone.0047033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 09/07/2012] [Indexed: 12/27/2022] Open
Abstract
Recent evidence suggests that Paracoccidioides species have the potential to undergo sexual reproduction, although no sexual cycle has been identified either in nature or under laboratory conditions. In the present work we detected low expression levels of the heterothallic MAT loci genes MAT1-1 and MAT1-2, the α-pheromone (PBα) gene, and the α- and a-pheromone receptor (PREB and PREA) genes in yeast and mycelia forms of several Paracoccidioides isolates. None of the genes were expressed in a mating type dependent manner. Stimulation of P. brasiliensis MAT1-2 strains with the synthetic α-pheromone peptide failed to elicit transcriptional activation of MAT1-2, PREB or STE12, suggesting that the strains tested are insensitive to α-pheromone. In order to further evaluate the biological functionality of the pair α-pheromone and its receptor, we took advantage of the heterologous expression of these Paracoccidioides genes in the corresponding S. cerevisiae null mutants. We show that S. cerevisiae strains heterologously expressing PREB respond to Pbα pheromone either isolated from Paracoccidioides culture supernatants or in its synthetic form, both by shmoo formation and by growth and cell cycle arrests. This allowed us to conclude that Paracoccidioides species secrete an active α-pheromone into the culture medium that is able to activate its cognate receptor. Moreover, expression of PREB or PBα in the corresponding null mutants of S. cerevisiae restored mating in these non-fertile strains. Taken together, our data demonstrate pheromone signaling activation by the Paracoccidioides α-pheromone through its receptor in this yeast model, which provides novel evidence for the existence of a functional mating signaling system in Paracoccidioides.
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Affiliation(s)
- Jéssica A. Gomes-Rezende
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B’s - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Ana G. Gomes-Alves
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B’s - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - João F. Menino
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B’s - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Marco A. Coelho
- Centro de Recursos Microbiológicos (CREM), Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - Paula Ludovico
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B’s - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Paula Gonçalves
- Centro de Recursos Microbiológicos (CREM), Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - Mark H. J. Sturme
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B’s - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Fernando Rodrigues
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B’s - PT Government Associate Laboratory, Braga/Guimarães, Portugal
- * E-mail:
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228
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Abstract
The arbuscular mycorrhizal fungi (AMF) are important symbionts of land plants, which are known for their tremendous positive effects on terrestrial ecosystems, their peculiar cellular features, and their very old evolutionary history. To date, no sexual stage or apparatus have ever been observed in these organisms; a remarkable absence for a eukaryotic lineage. For this reason, AMF have long been considered an evolutionary oddity, having evolved for over 500 millions of years in the absence of sexual reproduction and meiosis. Here, we discuss the recent identification across a number of AMF genomes, of many genes that are known to be involved in the process of meiosis in several eukaryotic model species. The presence of these genes in AMF is a previously unsuspected and highly intriguing finding, which suggests the presence of a “hidden” sexual (or parasexual) reproduction that awaits formal observation in these poorly studied fungi.
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Affiliation(s)
- Nicolas Corradi
- Canadian Institute for Advanced Research; Department of Biology; University of Ottawa; Ottawa, ON Canada
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229
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Yaguchi T, Imanishi Y, Matsuzawa T, Hosoya K, Hitomi J, Nakayama M. Method for identifying heat-resistant fungi of the genus Neosartorya. J Food Prot 2012; 75:1806-13. [PMID: 23043829 DOI: 10.4315/0362-028x.jfp-12-060] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Species of the genus Neosartorya are heat-resistant fungi that cause the spoilage of heat-processed acidic foods due to the formation of heat-resistant ascospores, and they produce mycotoxins, such as fumitremorgins and gliotoxin. Their anamorphs are phylogenetically and morphologically very close to Aspergillus fumigatus, which has never been reported as a spoilage agent in heat-processed food products. Therefore it is important to discriminate between the species of Neosartorya and A. fumigatus in the food industry. In the present study, we examined β-tubulin and calmodulin genes to identify Neosartorya and A. fumigatus at the species level and found a region for specifically detecting these species. We succeeded in developing the PCR method of differentiating and identifying Neosartorya and A. fumigatus using specific primer sets. Moreover, we developed specific primer sets to identify Neosartorya species, N. fischeri, N. glabra, N. hiratsukae, N. pseudofischeri, and N. spinosa-complex, which are important in food spoilage; these fungi vary in heat resistance and productivity of mycotoxins, depending on the species. PCR using these primer sets did not detect other fungi involved in food spoilage and environmental contamination. These identification methods are rapid and simple with extremely high specificity.
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Affiliation(s)
- Takashi Yaguchi
- Medical Mycology Research Center, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8673, Japan.
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230
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Kabir MA, Hussain MA, Ahmad Z. Candida albicans: A Model Organism for Studying Fungal Pathogens. ISRN MICROBIOLOGY 2012; 2012:538694. [PMID: 23762753 PMCID: PMC3671685 DOI: 10.5402/2012/538694] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Accepted: 08/30/2012] [Indexed: 01/12/2023]
Abstract
Candida albicans is an opportunistic human fungal pathogen that causes candidiasis. As healthcare has been improved worldwide, the number of immunocompromised patients has been increased to a greater extent and they are highly susceptible to various pathogenic microbes and C. albicans has been prominent among the fungal pathogens. The complete genome sequence of this pathogen is now available and has been extremely useful for the identification of repertoire of genes present in this pathogen. The major challenge is now to assign the functions to these genes of which 13% are specific to C. albicans. Due to its close relationship with yeast Saccharomyces cerevisiae, an edge over other fungal pathogens because most of the technologies can be directly transferred to C. albicans from S. cerevisiae and it is amenable to mutation, gene disruption, and transformation. The last two decades have witnessed enormous amount of research activities on this pathogen that leads to the understanding of host-parasite interaction, infections, and disease propagation. Clearly, C. albicans has emerged as a model organism for studying fungal pathogens along with other two fungi Aspergillus fumigatus and Cryptococcus neoformans. Understanding its complete life style of C. albicans will undoubtedly be useful for developing potential antifungal drugs and tackling Candida infections. This will also shed light on the functioning of other fungal pathogens.
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Affiliation(s)
- M Anaul Kabir
- Molecular Genetics Laboratory, School of Biotechnology, National Institute of Technology Calicut, Calicut 673601, Kerala, India
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231
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Soukup AA, Farnoodian M, Berthier E, Keller NP. NosA, a transcription factor important in Aspergillus fumigatus stress and developmental response, rescues the germination defect of a laeA deletion. Fungal Genet Biol 2012; 49:857-65. [PMID: 23022264 DOI: 10.1016/j.fgb.2012.09.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Revised: 09/11/2012] [Accepted: 09/13/2012] [Indexed: 10/27/2022]
Abstract
Aspergillus fumigatus is an increasingly serious pathogen of immunocompromised patients, causing the often fatal disease invasive aspergillosis (IA). One A. fumigatus virulence determinant of IA is LaeA, a conserved virulence factor in pathogenic fungi. To further understand the role of LaeA in IA, the expression profile of ΔlaeA was compared to wild type, and several transcription factors were found significantly misregulated by LaeA loss. One of the transcription factors up-regulated over 4-fold in the ΔlaeA strain was Afu4g09710, similar in sequence to Aspergillus nidulans NosA, which is involved in sexual development. Here we assessed loss of nosA (ΔnosA) and overexpression of nosA (OE::nosA) on A. fumigatus in both a wild type and ΔlaeA background. Based on the multiple alterations of physiological development of single and double mutants, we suggest that NosA mediates the decreased radial growth and delayed conidial germination observed in ΔlaeA strains, the former in a light dependent manner. The ΔnosA mutant showed increased virulence in the Galleria mellonella larvae model of disseminated aspergillosis, potentially due to its increased growth and germination rate. Furthermore, the A. fumigatus nosA allele was able to partially remediate sexual development in an A. nidulans ΔnosA background. Likewise, the A. nidulans nosA allele was able to restore the menadione sensitivity defect of the A. fumigatus ΔnosA strain, suggesting conservation of function of the NosA protein in these two species.
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Affiliation(s)
- Alexandra A Soukup
- Department of Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA
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232
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Comparative genome analysis of Trichophyton rubrum and related dermatophytes reveals candidate genes involved in infection. mBio 2012; 3:e00259-12. [PMID: 22951933 PMCID: PMC3445971 DOI: 10.1128/mbio.00259-12] [Citation(s) in RCA: 166] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The major cause of athlete's foot is Trichophyton rubrum, a dermatophyte or fungal pathogen of human skin. To facilitate molecular analyses of the dermatophytes, we sequenced T. rubrum and four related species, Trichophyton tonsurans, Trichophyton equinum, Microsporum canis, and Microsporum gypseum. These species differ in host range, mating, and disease progression. The dermatophyte genomes are highly colinear yet contain gene family expansions not found in other human-associated fungi. Dermatophyte genomes are enriched for gene families containing the LysM domain, which binds chitin and potentially related carbohydrates. These LysM domains differ in sequence from those in other species in regions of the peptide that could affect substrate binding. The dermatophytes also encode novel sets of fungus-specific kinases with unknown specificity, including nonfunctional pseudokinases, which may inhibit phosphorylation by competing for kinase sites within substrates, acting as allosteric effectors, or acting as scaffolds for signaling. The dermatophytes are also enriched for a large number of enzymes that synthesize secondary metabolites, including dermatophyte-specific genes that could synthesize novel compounds. Finally, dermatophytes are enriched in several classes of proteases that are necessary for fungal growth and nutrient acquisition on keratinized tissues. Despite differences in mating ability, genes involved in mating and meiosis are conserved across species, suggesting the possibility of cryptic mating in species where it has not been previously detected. These genome analyses identify gene families that are important to our understanding of how dermatophytes cause chronic infections, how they interact with epithelial cells, and how they respond to the host immune response.
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234
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Standardization of an Indirect ELISA for Serological Diagnosis of Aspergilloma. ARCHIVES OF CLINICAL INFECTIOUS DISEASES 2012. [DOI: 10.5812/archcid.14467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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235
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Molecular epidemiology of Aspergillus fumigatus isolates harboring the TR34/L98H azole resistance mechanism. J Clin Microbiol 2012; 50:2674-80. [PMID: 22675126 DOI: 10.1128/jcm.00335-12] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A rapid emergence of azole resistance has been observed in Aspergillus fumigatus in The Netherlands over the past decade. The dominant resistance mechanism appears to be of environmental origin and involves the TR(34)/L98H mutations in cyp51A. This resistance mechanism is now also increasingly being found in other countries. Therefore, genetic markers were used to gain more insights into the origin and spread of this genotype. Studies of 142 European isolates revealed that those with the TR(34)/L98H resistance mechanism showed less genetic variation than azole-susceptible isolates or those with a different genetic basis of resistance and were assigned to only four CSP (putative cell surface protein) types. Sexual crossing experiments demonstrated that TR(34)/L98H isolates could outcross with azole-susceptible isolates of different genetic backgrounds, suggesting that TR(34)/L98H isolates can undergo the sexual cycle in nature. Overall, our findings suggest a common ancestor of the TR(34)/L98H mechanism and subsequent migration of isolates harboring TR(34)/L98H across Europe.
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236
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Plasma membrane localization is required for RasA-mediated polarized morphogenesis and virulence of Aspergillus fumigatus. EUKARYOTIC CELL 2012; 11:966-77. [PMID: 22562470 DOI: 10.1128/ec.00091-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Ras is a highly conserved GTPase protein that is essential for proper polarized morphogenesis of filamentous fungi. Localization of Ras proteins to the plasma membrane and endomembranes through posttranslational addition of farnesyl and palmitoyl residues is an important mechanism through which cells provide specificity to Ras signal output. Although the Aspergillus fumigatus RasA protein is known to be a major regulator of growth and development, the membrane distribution of RasA during polarized morphogenesis and the role of properly localized Ras signaling in virulence of a pathogenic mold remain unknown. Here we demonstrate that Aspergillus fumigatus RasA localizes primarily to the plasma membrane of actively growing hyphae. We show that treatment with the palmitoylation inhibitor 2-bromopalmitate disrupts normal RasA plasma membrane association and decreases hyphal growth. Targeted mutations of the highly conserved RasA palmitoylation motif also mislocalized RasA from the plasma membrane and led to severe hyphal abnormalities, cell wall structural changes, and reduced virulence in murine invasive aspergillosis. Finally, we provide evidence that proper RasA localization is independent of the Ras palmitoyltransferase homolog, encoded by erfB, but requires the palmitoyltransferase complex subunit, encoded by erfD. Our results demonstrate that plasma membrane-associated RasA is critical for polarized morphogenesis, cell wall stability, and virulence in A. fumigatus.
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Woudenberg JHC, De Gruyter J, Crous PW, Zwiers LH. Analysis of the mating-type loci of co-occurring and phylogenetically related species of Ascochyta and Phoma. MOLECULAR PLANT PATHOLOGY 2012; 13:350-62. [PMID: 22014305 PMCID: PMC6638728 DOI: 10.1111/j.1364-3703.2011.00751.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Ascochyta and Phoma are fungal genera containing several important plant pathogenic species. These genera are morphologically similar, and recent molecular studies performed to unravel their phylogeny have resulted in the establishment of several new genera within the newly erected Didymellaceae family. An analysis of the structure of fungal mating-type genes can contribute to a better understanding of the taxonomic relationships of these plant pathogens, and may shed some light on their evolution and on differences in sexual strategy and pathogenicity. We analysed the mating-type loci of phylogenetically closely related Ascochyta and Phoma species (Phoma clematidina, Didymella vitalbina, Didymella clematidis, Peyronellaea pinodes and Peyronellaea pinodella) that co-occur on the same hosts, either on Clematis or Pisum. The results confirm that the mating-type genes provide the information to distinguish between the homothallic Pey. pinodes (formerly Ascochyta pinodes) and the heterothallic Pey. pinodella (formerly Phoma pinodella), and indicate the close phylogenetic relationship between these two species that are part of the disease complex responsible for Ascochyta blight on pea. Furthermore, our analysis of the mating-type genes of the fungal species responsible for causing wilt of Clematis sp. revealed that the heterothallic D. vitalbina (Phoma anamorph) is more closely related to the homothallic D. clematidis (Ascochyta anamorph) than to the heterothallic P. clematidina. Finally, our results indicate that homothallism in D. clematidis resulted from a single crossover between MAT1-1 and MAT1-2 sequences of heterothallic ancestors, whereas a single crossover event followed by an inversion of a fused MAT1/2 locus resulted in homothallism in Pey. pinodes.
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Affiliation(s)
- Joyce H C Woudenberg
- CBS-KNAW Fungal Biodiversity Centre, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
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238
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Jernerén F, Oliw EH. The fatty acid 8,11-diol synthase of Aspergillus fumigatus is inhibited by imidazole derivatives and unrelated to PpoB. Lipids 2012; 47:707-17. [PMID: 22544380 DOI: 10.1007/s11745-012-3673-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 04/06/2012] [Indexed: 12/13/2022]
Abstract
(8R)-Hydroperoxy-(9Z,12Z)-octadecadienoic acid (8-HPODE) is formed by aspergilli as an intermediate in biosynthesis of oxylipins with effects on sporulation. 8-HPODE is transformed by separate diol synthases to (5S,8R)-dihydroxy- and (8R,11S)-dihydroxy-(9Z,12Z)-octadecadienoic acids (5,8- and 8,11-DiHODE). The former is formed by the cytochrome P450 (P450) domain of 5,8-linoleate diol synthase (5,8-LDS or PpoA). Our aim was to characterize the 8,11-diol synthase of Aspergillus fumigatus, which is prominent in many strains. The 8,11-diol synthase was soluble and had a larger molecular size (>100 kDa) than most P450. Miconazole, ketoconazole, and 1-benzylimidazole, classical inhibitors of P450, reduced the biosynthesis of 8,11-DiHODE from 8-HPODE (apparent IC(50) values ~0.8, ~5, and ~0.6 μM, respectively), but did not inhibit the biosynthesis of 5,8-DiHODE. Analysis of hydroperoxides of regioisomeric C(18) and C(20) fatty acids showed that the 8,11-diol synthase was specific for certain hydroperoxides with R configuration. The suprafacial hydrogen abstraction and oxygen insertion at C-11 of 8-HPODE was associated with a small deuterium kinetic isotope effect ((H) k (cat)/(D) k (cat) ~1.5), consistent with P450-catalyzed oxidation. The genome of A. fumigatus contains over 70 P450 sequences. The reaction mechanism, size, and solubility of 8,11-diol synthase pointed to PpoB, a homologue of 5,8-LDS, as a possible candidate of this activity. Gene deletion of ppoB of A. fumigatus strains AF:∆ku80 and J272 did not inhibit biosynthesis of 8,11-DiHODE and recombinant PpoB appeared to lack diol synthase activity. We conclude that 8,11-DiHODE is formed from 8-HPODE by a soluble and substrate-specific 8,11-diol synthase with catalytic characteristics of class III P450.
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Affiliation(s)
- Fredrik Jernerén
- Department of Pharmaceutical Biosciences, Uppsala Biomedical Center, Uppsala University, 75124, Uppsala, Sweden
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239
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Aspergilosis. Formas clínicas y tratamiento. Enferm Infecc Microbiol Clin 2012; 30:201-8. [DOI: 10.1016/j.eimc.2011.12.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 12/13/2011] [Indexed: 11/24/2022]
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240
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Asexual reproduction induces a rapid and permanent loss of sexual reproduction capacity in the rice fungal pathogen Magnaporthe oryzae: results of in vitro experimental evolution assays. BMC Evol Biol 2012; 12:42. [PMID: 22458778 PMCID: PMC3379926 DOI: 10.1186/1471-2148-12-42] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 03/29/2012] [Indexed: 12/15/2022] Open
Abstract
Background Sexual reproduction is common in eukaryotic microorganisms, with few species reproducing exclusively asexually. However, in some organisms, such as fungi, asexual reproduction alternates with episodic sexual reproduction events. Fungi are thus appropriate organisms for studies of the reasons for the selection of sexuality or clonality and of the mechanisms underlying this selection. Magnaporthe oryzae, an Ascomycete causing blast disease on rice, reproduces mostly asexually in natura. Sexual reproduction is possible in vitro and requires (i) two strains of opposite mating types including (ii) at least one female-fertile strain (i.e. a strain able to produce perithecia, the female organs in which meiosis occurs). Female-fertile strains are found only in limited areas of Asia, in which evidence for contemporary recombination has recently been obtained. We induced the forced evolution of four Chinese female-fertile strains in vitro by the weekly transfer of asexual spores (conidia) between Petri dishes. We aimed to determine whether female fertility was rapidly lost in the absence of sexual reproduction and whether this loss was controlled genetically or epigenetically. Results All the strains became female-sterile after 10 to 19 rounds of selection under asexual conditions. As no single-spore isolation was carried out, the observed decrease in the production of perithecia reflected the emergence and the invasion of female-sterile mutants. The female-sterile phenotype segregated in the offspring of crosses between female-sterile evolved strains and female-fertile wild-type strains. This segregation was maintained in the second generation in backcrosses. Female-sterile evolved strains were subjected to several stresses, but none induced the restoration of female fertility. This loss of fertility was therefore probably due to genetic rather than epigenetic mechanisms. In competition experiments, female-sterile mutants produced similar numbers of viable conidia to wild-type strains, but released them more efficiently. This advantage may account for the invasion of our populations by female-sterile mutants. Conclusions We show for the first time that, in the absence of sexual reproduction, female-sterile mutants of M. oryzae rice strains can arise and increase in abundance in asexual generations. This change in phenotype was frequent and probably caused by mutation. These results suggest that female fertility may have been lost rapidly during the dispersion of the fungus from Asia to the rest of the world.
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241
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Spatafora JW, Owensby CA, Douhan GW, Boehm EWA, Schoch CL. Phylogenetic placement of the ectomycorrhizal genus Cenococcum in Gloniaceae (Dothideomycetes). Mycologia 2012; 104:758-65. [PMID: 22453119 DOI: 10.3852/11-233] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cenococcum is a genus of ectomycorrhizal Ascomycota that has a broad host range and geographic distribution. It is not known to produce either meiotic or mitotic spores and is known to exist only in the form of hyphae, sclerotia and host-colonized ectomycorrhizal root tips. Due to its lack of sexual and asexual spores and reproductive structures, it has proven difficult to incorporate into traditional classification within Ascomycota. Molecular phylogenetic studies of ribosomal RNA placed Cenococcum in Dothideomycetes, but the definitive identification of closely related taxa remained elusive. Here we report a phylogenetic analysis of five nuclear loci (SSU, LSU, TEF1, RPB1, RPB2) of Dothideomycetes that placed Cenococcum as a close relative of the genus Glonium of Gloniaceae (Pleosporomycetidae incertae sedis) with strong statistical support. Glonium is a genus of saprobic Dothideomycetes that produces darkly pigmented, carbonaceous, hysteriate apothecia and is not known to be biotrophic. Evolution of ectomycorhizae, Cenococcum and Dothideomycetes is discussed.
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Affiliation(s)
- Joseph W Spatafora
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR97330, USA.
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242
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Morita A, Saitoh Y, Izumitsu K, Tanaka C. Molecular organization of the mating type (Mat) locus of Exserohilum monoceras (Setosphaeria monoceras), a bioherbicide agent for Echinochloa weeds. MYCOSCIENCE 2012. [DOI: 10.1007/s10267-011-0141-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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243
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Presence and functionality of mating type genes in the supposedly asexual filamentous fungus Aspergillus oryzae. Appl Environ Microbiol 2012; 78:2819-29. [PMID: 22327593 DOI: 10.1128/aem.07034-11] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The potential for sexual reproduction in Aspergillus oryzae was assessed by investigating the presence and functionality of MAT genes. Previous genome studies had identified a MAT1-1 gene in the reference strain RIB40. We now report the existence of a complementary MAT1-2 gene and the sequencing of an idiomorphic region from A. oryzae strain AO6. This allowed the development of a PCR diagnostic assay, which detected isolates of the MAT1-1 and MAT1-2 genotypes among 180 strains assayed, including industrial tane-koji isolates. Strains used for sake and miso production showed a near-1:1 ratio of the MAT1-1 and MAT1-2 mating types, whereas strains used for soy sauce production showed a significant bias toward the MAT1-2 mating type. MAT1-1 and MAT1-2 isogenic strains were then created by genetic manipulation of the resident idiomorph, and gene expression was compared by DNA microarray and quantitative real-time PCR (qRT-PCR) methodologies under conditions in which MAT genes were expressed. Thirty-three genes were found to be upregulated more than 10-fold in either the MAT1-1 host strain or the MAT1-2 gene replacement strain relative to each other, showing that both the MAT1-1 and MAT1-2 genes functionally regulate gene expression in A. oryzae in a mating type-dependent manner, the first such report for a supposedly asexual fungus. MAT1-1 expression specifically upregulated an α-pheromone precursor gene, but the functions of most of the genes affected were unknown. The results are consistent with a heterothallic breeding system in A. oryzae, and prospects for the discovery of a sexual cycle are discussed.
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244
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Saleh D, Xu P, Shen Y, Li C, Adreit H, Milazzo J, Ravigné V, Bazin E, Nottéghem JL, Fournier E, Tharreau D. Sex at the origin: an Asian population of the rice blast fungus Magnaporthe oryzae reproduces sexually. Mol Ecol 2012; 21:1330-44. [PMID: 22313491 DOI: 10.1111/j.1365-294x.2012.05469.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Sexual reproduction may be cryptic or facultative in fungi and therefore difficult to detect. Magnaporthe oryzae, which causes blast, the most damaging fungal disease of rice, is thought to originate from southeast Asia. It reproduces asexually in all rice-growing regions. Sexual reproduction has been suspected in limited areas of southeast Asia, but has never been demonstrated in contemporary populations. We characterized several M. oryzae populations worldwide both biologically and genetically, to identify candidate populations for sexual reproduction. The sexual cycle of M. oryzae requires two strains of opposite mating types, at least one of which is female-fertile, to come into contact. In one Chinese population, the two mating types were found to be present at similar frequencies and almost all strains were female-fertile. Compatible strains from this population completed the sexual cycle in vitro and produced viable progenies. Genotypic richness and linkage disequilibrium data also supported the existence of sexual reproduction in this population. We resampled this population the following year, and the data obtained confirmed the presence of all the biological and genetic characteristics of sexual reproduction. In particular, a considerable genetic reshuffling of alleles was observed between the 2 years. Computer simulations confirmed that the observed genetic characteristics were unlikely to have arisen in the absence of recombination. We therefore concluded that a contemporary population of M. oryzae, pathogenic on rice, reproduces sexually in natura in southeast Asia. Our findings provide evidence for the loss of sexual reproduction by a fungal plant pathogen outside its centre of origin.
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Affiliation(s)
- Dounia Saleh
- Centre de Coopération Internationale en Recherche Agronomique pour le Développement, UMR BGPI, Montpellier, France
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245
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Burco JD, Etienne KA, Massey JG, Ziccardi MH, Balajee SA. Molecular sub-typing suggests that the environment of rehabilitation centers may be a potential source ofAspergillus fumigatusinfecting rehabilitating seabirds. Med Mycol 2012; 50:91-8. [DOI: 10.3109/13693786.2011.592860] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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246
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Sinonasal and sino-orbital aspergillosis in 23 cats: Aetiology, clinicopathological features and treatment outcomes. Vet J 2012; 191:58-64. [DOI: 10.1016/j.tvjl.2011.02.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 01/26/2011] [Accepted: 02/02/2011] [Indexed: 12/13/2022]
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247
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Hara S, Jin FJ, Takahashi T, Koyama Y. A further study on chromosome minimization by protoplast fusion in Aspergillus oryzae. Mol Genet Genomics 2011; 287:177-87. [PMID: 22207035 DOI: 10.1007/s00438-011-0669-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 12/18/2011] [Indexed: 11/29/2022]
Abstract
Our goal in this work was to develop a method to minimize the chromosomes of Aspergillus oryzae, to arrive at a deeper understanding of essential gene functions that will help create more efficient industrially useful strains. In a previous study, we successfully constructed a highly reduced chromosome 7 using multiple large-scale chromosomal deletions (Jin et al. in Mol Genet Genomics 283:1-12, 2010). Here, we have created a further reduced chromosome A. oryzae mutant harboring a reduced chromosome 7 and a reduced chromosome 8 both of which contain a large number of non-syntenic blocks. These are the smallest A. oryzae chromosomes that have been reported. Protoplast fusion between the two distinct chromosome-reduced mutants produced a vigorous and stable fusant which was isolated. PCR and flow cytometry confirmed that two kinds of nuclei, derived from the parent strains, existed in this fusant and that the chromosome DNA per nucleus was doubled, suggesting that the fusant was a heterozygous diploid strain. By treating the cell with 1 μg/ml benomyl, cell nuclei haploidization was induced in the stable diploid strain. Array comparative genomic hybridization and pulsed-field gel electrophoresis confirmed that the reduced chromosomes 7 and 8 co-existed in the haploid fusant and that no other chromosomal modifications had occurred. This method provides a useful tool for chromosome engineering in A. oryzae to construct an industry-useful strain.
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Affiliation(s)
- Seiichi Hara
- Noda Institute for Scientific Research, 399 Noda, Noda 278-0037, Japan
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248
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A fungal sexual revolution: Aspergillus and Penicillium show the way. Curr Opin Microbiol 2011; 14:649-54. [DOI: 10.1016/j.mib.2011.10.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 09/29/2011] [Accepted: 10/03/2011] [Indexed: 01/09/2023]
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249
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Klaassen CHW, Gibbons JG, Fedorova ND, Meis JF, Rokas A. Evidence for genetic differentiation and variable recombination rates among Dutch populations of the opportunistic human pathogen Aspergillus fumigatus. Mol Ecol 2011; 21:57-70. [PMID: 22106836 DOI: 10.1111/j.1365-294x.2011.05364.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
As the frequency of antifungal drug resistance continues to increase, understanding the genetic structure of fungal populations, where resistant isolates have emerged and spread, is of major importance. Aspergillus fumigatus is an ubiquitously distributed fungus and the primary causative agent of invasive aspergillosis (IA), a potentially lethal infection in immunocompromised individuals. In the last few years, an increasing number of A. fumigatus isolates has evolved resistance to triazoles, the primary drugs for treating IA infections. In most isolates, this multiple-triazole-resistance (MTR) phenotype is caused by mutations in the cyp51A gene, which encodes the protein targeted by the triazoles. We investigated the genetic differentiation and reproductive mode of A. fumigatus in the Netherlands, the country where the MTR phenotype probably originated, to determine their role in facilitating the emergence and distribution of resistance genotypes. Using 20 genome-wide neutral markers, we genotyped 255 Dutch isolates including 25 isolates with the MTR phenotype. In contrast to previous reports, our results show that Dutch A. fumigatus genotypes are genetically differentiated into five distinct populations. Four of the five populations show significant linkage disequilibrium, indicative of an asexual reproductive mode, whereas the fifth population is in linkage equilibrium, indicative of a sexual reproductive mode. Notably, the observed genetic differentiation among Dutch isolates does not correlate with geography, although all isolates with the MTR phenotype nest within a single, predominantly asexual, population. These results suggest that both reproductive mode and genetic differentiation contribute to the structure of Dutch A. fumigatus populations and are probably shaping the evolutionary dynamics of drug resistance in this potentially deadly pathogen.
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Affiliation(s)
- Corné H W Klaassen
- Department of Medical Microbiology and Infectious Diseases, Canisius Wilhelmina Hospital, Weg Door Jonkerbos 100, 6532 SZ Nijmegen, The Netherlands.
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250
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Abstract
The mating efficiency of 50 Aspergillus fumigatus isolates from both clinical and environmental sources was analyzed. Forty isolates completed the sexual cycle in 4 weeks with variable levels of fertility designated high, medium, or low. Two opposite-mating-type strains exhibiting the highest fertility, AFB62 (MAT1-1), isolated from a case of invasive aspergillosis, and AFIR928 (MAT1-2), isolated from the environment, were chosen as the supermater pair. Single cleistothecia obtained from a cross of the two strains harbored a minimum of 1 × 104 ascospores. The viability of ascospores increased with the age of the fruiting body, 17% at 4 weeks and reaching 95% at 20 weeks. AFB62 and AFIR928 were equally virulent in two different murine models, despite differences in their sources. High recombination frequencies were observed when the closely linked genes alb1 (AFUA_2G17600) and abr2 (AFUA_2G17530) were used as genetic markers. Comparative genome hybridization analyses revealed that only 86 genes (ca. 0.86% of the genome) are significantly diverged between AFB62 and AFIR928. The high fertility in a relatively short period, combined with a high degree of virulence and a high recombination frequency, demonstrates that the mating pair AFB62 and AFIR928 provides an excellent tool for genetic studies of A. fumigatus. ImportanceAspergillus fumigatus is a heterothallic fungal pathogen that causes life-threatening infections in immunocompromised hosts. Although heterothallism facilitates genetic study via recombinational analysis, previous work showed that a 6-month incubation period is required for the completion of sexual reproduction in this species. Such a long incubation period impedes progress in genetic research. To discover a highly fertile (supermater) pair that can complete the sexual cycle in a considerably shorter period, we screened 50 strains collected from various geographic regions for mating efficiency. We identified a highly virulent pair of supermaters that can be an invaluable tool for genetic study. Aspergillus fumigatus is a heterothallic fungal pathogen that causes life-threatening infections in immunocompromised hosts. Although heterothallism facilitates genetic study via recombinational analysis, previous work showed that a 6-month incubation period is required for the completion of sexual reproduction in this species. Such a long incubation period impedes progress in genetic research. To discover a highly fertile (supermater) pair that can complete the sexual cycle in a considerably shorter period, we screened 50 strains collected from various geographic regions for mating efficiency. We identified a highly virulent pair of supermaters that can be an invaluable tool for genetic study.
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