Rydholm C, Dyer P S, Lutzoni F
Biology Department, Box 90338, Duke University, Durham, NC 27708, USA.
Eukaryot Cell. 2007 May;6(5):868-74. doi: 10.1128/EC.00319-06. Epub 2007 Mar 23.
Degenerate PCR and chromosome-walking approaches were used to identify mating-type (MAT) genes and flanking regions from the homothallic (sexually self-fertile) euascomycete fungus Neosartorya fischeri, a close relative of the opportunistic human pathogen Aspergillus fumigatus. Both putative alpha- and high-mobility-group-domain MAT genes were found within the same genome, providing a functional explanation for self-fertility. However, unlike those in many homothallic euascomycetes (Pezizomycotina), the genes were not found adjacent to each other and were termed MAT1 and MAT2 to recognize the presence of distinct loci. Complete copies of putative APN1 (DNA lyase) and SLA2 (cytoskeleton assembly control) genes were found bordering the MAT1 locus. Partial copies of APN1 and SLA2 were also found bordering the MAT2 locus, but these copies bore the genetic hallmarks of pseudogenes. Genome comparisons revealed synteny over at least 23,300 bp between the N. fischeri MAT1 region and the A. fumigatus MAT locus region, but no such long-range conservation in the N. fischeri MAT2 region was evident. The sequence upstream of MAT2 contained numerous candidate transposase genes. These results demonstrate a novel means involving the segmental translocation of a chromosomal region by which the ability to undergo self-fertilization may be acquired. The results are also discussed in relation to their significance in indicating that heterothallism may be ancestral within the Aspergillus section Fumigati.
采用简并PCR和染色体步移方法，从同宗配合（性自育）的真子囊菌费氏新萨托菌中鉴定交配型（MAT）基因及其侧翼区域，该菌是机会性人类病原体烟曲霉的近亲。在同一基因组中发现了假定的α和高迁移率族结构域MAT基因，为自育性提供了功能解释。然而，与许多同宗配合的真子囊菌（粪壳菌纲）不同，这些基因并非相邻，而是被命名为MAT1和MAT2以识别不同位点的存在。在MAT1位点边界发现了假定的APN1（DNA裂解酶）和SLA2（细胞骨架组装控制）基因的完整拷贝。在MAT2位点边界也发现了APN1和SLA2的部分拷贝，但这些拷贝具有假基因的遗传特征。基因组比较显示，费氏新萨托菌MAT1区域与烟曲霉MAT位点区域之间至少有23,300 bp的同线性，但费氏新萨托菌MAT2区域没有明显的这种长距离保守性。MAT2上游序列包含许多候选转座酶基因。这些结果证明了一种涉及染色体区域片段易位的新机制，通过该机制可能获得自交能力。还讨论了这些结果对于表明异宗配合可能是烟曲霉属烟曲霉组的祖先的意义。
