White grain disorder (WGD) is a recently emerged wheat disease in Australia caused by three Botryosphaeriaceae fungi, from the genus Eutiarosporella. These species are E. tritici-australis, E. darliae, and E. pseudodarliae. Characterisation of the mating type genes for the WGD-species show that the genome sequence of a single E. darliae and E. pseudodarliae isolate both harbour MAT1-2-1 and MAT1-1-1, which suggests that these species are homothallic. However, unlike most other characterised mating-type loci from other homothallic Dothideomycetes, these species' MAT1-1-1 are located at a separate locus, inserted within the coding region of another gene. The sequenced strain of E. tritici-australis analysed did not harbour MAT1-1-1. Including the sequenced strain, we screened the mating type genes present in 16 E. tritici-australis individuals isolated from infected grain from fields in South Australia. Of these 16, 11 harbour MAT1-1-1 and the other five harbour MAT1-2-1. The genome of a MAT1-1-1 harbouring isolate was re-sequenced, which demonstrated that MAT1-1-1 was present at the MAT locus. We examined non-coding DNA surrounding the MAT1-1-1 gene in E. pseudodarliae and observed fragments of the MAT locus both up and downstream. These fragments and their orientation around MAT1-1-1 is similar to characterised heterothallic Botryosphaeriaceae. Based on these gene arrangements, we conclude that the new MAT1-1-1 containing locus likely originated from a cryptic DNA integration event between two heterothallic individuals. We hypothesise that this integration event led to the formation of a homothallic lineage, which is the common ancestor of E. darliae and E. pseudodarliae.

中文翻译：

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据推测，从杂种变态到同种变态的转变促进了新兴的葡萄球菌小麦病原体之间的物种形成。

白粒病（WGD）是澳大利亚一种新近出现的小麦病，由Eutiarosporella属的三种Botryosphaeriaceae真菌引起。这些物种是大叶埃希氏菌，大肠埃希氏菌和伪大肠埃希氏菌。WGD物种的交配型基因的特征表明，单个大肠埃希氏菌和假大肠埃希氏菌的基因组序列都分离了MAT1-2-1和MAT1-1-1，这表明这些物种是同型的。然而，与来自其他同型十二指肠菌的大多数其他特征性交配型基因座不同，这些物种的MAT1-1-1位于单独的基因座，插入另一个基因的编码区域内。所分析的小麦小麦的测序菌株未携带MAT1-1-1。包括测序菌株在内，我们筛选了16 E中存在的交配型基因。从南澳大利亚田地的受感染谷物中分离出的小麦-小麦。在这16个港口中，有11个港口有MAT1-1-1，其他五个港口有MAT1-2-1。对带有MAT1-1-1的分离株的基因组进行了重新测序，这表明MAT1-1-1存在于MAT基因座上。我们检查了伪大肠埃希菌中MAT1-1-1基因周围的非编码DNA，并观察了MAT基因座上下游的片段。这些片段及其在MAT1-1-1周围的方向类似于特征性的杂藻灰霉菌科。基于这些基因安排，我们得出的结论是，包含新MAT1-1-1的基因座可能起源于两个异基因个体之间的隐秘DNA整合事件。我们假设，这种整合事件导致了同源系的形成，这是E的共同祖先。