Eukaryotic Cell doi:10.1128/EC.00117-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Genomic and Population Analyses of the Mating Type Loci in Coccidioides reveals evidence for Sexual Reproduction and Gene Acquisition
M. Alejandra Mandel,
Bridget M. Barker,
Scott Kroken,
Steven D. Rounsley,
and
Marc J. Orbach*
Department of Plant Sciences, Division of Plant Pathology and Microbiology, University of Arizona, Tucson, AZ; Valley Fever Center for Excellence, Tucson, AZ; Graduate Interdisciplinary Program in Genetics, University of Arizona; Bio5 Institute, University of Arizona; and Department of Plant Sciences, Division of Plant Biology, University of Arizona
* To whom correspondence should be addressed. Email:
orbachmj{at}ag.arizona.edu.
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Abstract |
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Coccidioides species, the fungi responsible for the valley fever disease, are known to reproduce asexually through the production of arthroconidia that are the infectious propagules. The possible role of sexual reproduction in survival and dispersal of this pathogen is unexplored. To determine the potential for mating in Coccidioides, we analyzed genome sequences and identified mating type loci characteristic of heterothallic ascomycetes. Coccidioides strains contain either a MAT1-1 or MAT1-2 idiomorph, which are 8.1 and 9 kb in length respectively, the longest reported for any ascomycete species. They contain four and five genes respectively, also more than present in the MAT loci of most ascomycetes. Along with their cDNA structures, we determined that all genes in the MAT loci are transcribed. Two genes frequently found in common sequences flanking MAT idiomorphs, APN2 and cox13, are within the MAT loci in Coccidioides, but the MAT1-1 and MAT1-2 copies have diverged dramatically from each other. Data indicate that the acquisition of these genes in the MAT loci occurred prior to the separation of Coccidioides from Uncinocarpus reesii. Analysis of 436 Coccidioides isolates from patients and the environment indicate that in both C. immitis and C. posadasii there is a 1:1 distribution of MAT loci, as would be expected for sexually reproducing species. In addition, analysis of isolates obtained from eleven soil samples found that at three sites, strains of both mating types were present indicating that compatible strains were in close proximity in the environment.
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