Department of Genetics, Forestry and Agricultural Biotechnology Institute-FABI, University of Pretoria, Pretoria 0002, South Africa.
Fungal Biol. 2013 Jun;117(6):411-21. doi: 10.1016/j.funbio.2013.04.005. Epub 2013 Apr 23.
Leptographium procerum and the closely related species Leptographium profanum, are ascomycetes associated with root-infesting beetles on pines and hardwood trees, respectively. Both species occur in North America where they are apparently native. L. procerum has also been found in Europe, China New Zealand, and South Africa where it has most probably been introduced. As is true for many other Leptographium species, sexual states have never been observed in L. procerum or L. profanum. The objectives of this study were to clone and characterize the mating type loci of these fungi, and to develop markers to determine the mating types of individual isolates. To achieve this, a partial sequence of MAT1-2-1 was amplified using degenerate primers targeting the high mobility group (HMG) sequence. A complete MAT1-2 idiomorph of L. profanum was subsequently obtained by screening a genomic library using the HMG sequence as a probe. Long range PCR was used to amplify the complete MAT1-1 idiomorph of L. profanum and both the MAT1-1 and MAT1-2 idiomorphs of L. procerum. Characterization of the MAT idiomorphs suggests that the MAT genes are fully functional and that individuals of both these species are self-sterile in nature with a heterothallic mating system. Mating type markers were developed and tested on a population of L. procerum isolates from the USA, the assumed center of origin for this species. The results suggest that cryptic sexual reproduction is occurring or has recently taken place within this population.
串珠镰孢菌（Leptographium procerum）和与其密切相关的物种平脐蠕孢菌（Leptographium profanum）是子囊菌，分别与危害松树和硬木树木的根部的甲虫有关。这两个物种都出现在北美的本土地区。串珠镰孢菌也存在于欧洲、中国、新西兰和南非，在这些地区，它很可能是被引入的。与许多其他的串珠镰孢菌物种一样，在串珠镰孢菌或平脐蠕孢菌中从未观察到有性状态。本研究的目的是克隆和鉴定这些真菌的交配型基因座，并开发用于确定单个分离株交配型的标记。为了实现这一目标，使用针对高迁移率族（HMG）序列的简并引物扩增了 MAT1-2-1 的部分序列。随后，通过使用 HMG 序列作为探针筛选基因组文库，获得了平脐蠕孢菌完整的 MAT1-2 同型物。长距离 PCR 用于扩增平脐蠕孢菌完整的 MAT1-1 同型物以及串珠镰孢菌的 MAT1-1 和 MAT1-2 同型物。MAT 同型物的特征表明，MAT 基因是完全功能的，这两个物种的个体本质上是自育的，具有异宗配合的交配系统。开发了交配型标记，并在美国的串珠镰孢菌分离株群体中进行了测试，美国被认为是该物种的起源中心。结果表明，在该种群中正在发生或最近发生了隐式有性繁殖。
