Mandel M Alejandra, Barker Bridget M, Kroken Scott, Rounsley Steven D, Orbach Marc J
Division of Plant Pathology and Microbiology, Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA.
Eukaryot Cell. 2007 Jul;6(7):1189-99. doi: 10.1128/EC.00117-07. Epub 2007 May 18.
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 the survival and dispersal of these pathogens is unexplored. To determine the potential for mating of Coccidioides, we analyzed genome sequences and identified mating type loci characteristic of heterothallic ascomycetes. Coccidioides strains contain either a MAT1-1 or a MAT1-2 idiomorph, which is 8.1 or 9 kb in length, respectively, the longest reported for any ascomycete species. These idiomorphs contain four or five genes, respectively, more than are 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. An analysis of 436 Coccidioides isolates from patients and the environment indicates that in both Coccidioides immitis and C. posadasii, there is a 1:1 distribution of MAT loci, as would be expected for sexually reproducing species. In addition, an analysis of isolates obtained from 11 soil samples demonstrated that at three sampling sites, strains of both mating types were present, indicating that compatible strains were in close proximity in the environment.
球孢子菌属是引发山谷热疾病的真菌，已知其通过产生作为感染性繁殖体的关节孢子进行无性繁殖。有性繁殖在这些病原体的生存和传播中可能发挥的作用尚未得到探索。为了确定球孢子菌的交配潜力，我们分析了基因组序列，并鉴定了异宗配合子囊菌特有的交配型位点。球孢子菌菌株含有MAT1-1或MAT1-2特异性基因座，长度分别为8.1或9 kb，这是所有子囊菌物种中报道的最长的。这些特异性基因座分别包含四个或五个基因，比大多数子囊菌的MAT基因座中的基因更多。连同它们的cDNA结构，我们确定MAT基因座中的所有基因都被转录。在MAT特异性基因座侧翼的共同序列中经常发现的两个基因APN2和COX13在球孢子菌的MAT基因座内，但MAT1-1和MAT1-2拷贝彼此之间已经发生了显著分化。数据表明，这些基因在MAT基因座中的获得发生在球孢子菌与瑞斯氏单囊菌分离之前。对436份来自患者和环境的球孢子菌分离株的分析表明，在粗球孢子菌和波萨达斯球孢子菌中，MAT基因座的分布比例均为1:1，这是有性繁殖物种所预期的。此外，对从11个土壤样本中获得的分离株的分析表明，在三个采样点都存在两种交配型的菌株，这表明环境中存在相容性菌株。
