Discovery of a sexual cycle in the opportunistic fungal pathogen Aspergillus fumigatus

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Abstract

Aspergillus fumigatus is a saprotrophic fungus whose spores are ubiquitous in the atmosphere1. It is also an opportunistic human pathogen in immunocompromised individuals, causing potentially lethal invasive infections2,3, and is associated with severe asthma and sinusitis4. The species is only known to reproduce by asexual means5, but there has been accumulating evidence for recombination and gene flow from population genetic studies5,6,7,8, genome analysis9,10, the presence of mating-type genes8,10 and expression of sex-related genes8 in the fungus. Here we show that A. fumigatus possesses a fully functional sexual reproductive cycle that leads to the production of cleistothecia and ascospores, and the teleomorph Neosartorya fumigata is described. The species has a heterothallic breeding system; isolates of complementary mating types are required for sex to occur. We demonstrate increased genotypic variation resulting from recombination between mating type and DNA fingerprint markers in ascospore progeny from an Irish environmental subpopulation. The ability of A. fumigatus to engage in sexual reproduction is highly significant in understanding the biology and evolution of the species. The presence of a sexual cycle provides an invaluable tool for classical genetic analyses and will facilitate research into the genetic basis of pathogenicity and fungicide resistance in A. fumigatus, with the aim of improving methods for the control of aspergillosis. These results also yield insights into the potential for sexual reproduction in other supposedly ‘asexual’ fungi.

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Figure 1: Genetic diversity of 91 A. fumigatus isolates from Dublin, Ireland.
Figure 2: Neosartorya fumigata sp. nov.
Figure 3: Segregation patterns of molecular markers.

Accession codes

Primary accessions

GenBank/EMBL/DDBJ

Data deposits

DNA sequences have been deposited in GenBank under accession numbers EU541353 and EU541354 (carboxypeptidase-5) and EU541355 (β-tubulin). The holotype of Neosartorya fumigata has been deposited in the Herbarium of the Royal Botanic Gardens, Kew, under accession number K(M)159484. The assignment Neosartorya fumigata O’Gorman, Fuller & Dyer sp. nov. has been deposited in MycoBank under accession number MB 512563.

Change history

  • 22 January 2009

    The Latin diagnosis for Neosartorya fumigata was moved from the Supplementary Information to the main text on 29 January 2009.

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Acknowledgements

We thank S. A. Balajee for access to unpublished data, C. Duggan for assistance with the Latin diagnosis, and C. O’Connell for taking the scanning electron micrographs. This work was supported by an IRCSET Postgraduate Research Scholarship, an EC Marie Curie Training Fellowship and a grant from the British Mycological Society to C.O’G.

Author Contributions C.O’G., H.T.F. and P.S.D. designed the experiments. C.O’G. performed most of the experiments. C.O’G. and P.S.D. analysed the results and wrote the manuscript. All authors contributed to editing the manuscript.

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Correspondence to Céline M. O’Gorman or Paul S. Dyer.

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This file contains Supplementary Notes, Supplementary Figure 1, Supplementary Tables 1-5, Supplementary Discussion and additional references. (PDF 658 kb)

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O’Gorman, C., Fuller, H. & Dyer, P. Discovery of a sexual cycle in the opportunistic fungal pathogen Aspergillus fumigatus. Nature 457, 471–474 (2009). https://doi.org/10.1038/nature07528

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