Unidirectional Evolutionary Transitions in Fungal Mating Systems and the Role of Transposable Elements
Unidirectional Evolutionary Transitions in Fungal Mating Systems and the Role of Transposable Elements
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DOI：
10.1093/molbev/mss132
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发表时间：
2012-10-01
影响因子：
10.7
通讯作者：
Johannesson, Hanna
中科院分区：
文献类型：
--
作者：
Gioti, Anastasia;Mushegian, Alexandra A.;Johannesson, Hanna
在真菌王国中，交配系统的进化是高度动态的，甚至在密切相关的物种之间也是不同的。交配型（mat）基因座中的重排，其中包含性发育的主要调节因子，预计是自不育（异宗配合）和自育（同宗配合）之间的过渡。然而，真菌交配系统的遗传机制和进化转变的方向仍存在争议。在这里，我们提出了新的序列的垫轨迹的四个同宗配合和一个异宗配合的模式属脉孢菌（子囊菌门）的物种。通过研究这些序列和以前发表的数据之间的同线性模式，我们表明，该位点是属于不同的系统发育分支的异宗配合物种之间的保守，而不同的基因排列特征的四个同宗配合物种。这些结果使我们能够确定一个异宗配合的祖先属，证实了单向过渡到自交的死胡同理论的预测。我们发现，至少有四个转变，从异宗配合到同宗配合发生在脉孢菌，其中三个涉及收购到同一个单倍体基因组的两种交配类型的序列。我们目前的证据表明，两种遗传机制，使这些转变：易位和不平等的交叉。最后，我们确定了两个新的反转录转座子，并建议这些发挥了重要作用，在交配系统的过渡，通过促进多个重排的垫轨迹。
In the fungal kingdom, the evolution of mating systems is highly dynamic, varying even among closely related species. Rearrangements in the mating-type (mat) locus, which contains the major regulators of sexual development, are expected to underlie the transitions between self-sterility (heterothallism) and self-fertility (homothallism). However, both the genetic mechanisms and the direction of evolutionary transitions in fungal mating systems are under debate. Here, we present new sequences of the mat locus of four homothallic and one heterothallic species of the model genus Neurospora (Ascomycota). By examining the patterns of synteny among these sequences and previously published data, we show that the locus is conserved among heterothallic species belonging to distinct phylogenetic clades, while different gene arrangements characterize the four homothallic species. These results allowed us to ascertain a heterothallic ancestor for the genus, confirming the prediction of the dead-end theory on unidirectional transitions toward selfing. We show that at least four shifts from heterothallism to homothallism have occurred in Neurospora, three of which involve the acquisition of sequences of both mating types into the same haploid genome. We present evidence for two genetic mechanisms allowing these shifts: translocation and unequal crossover. Finally, we identified two novel retrotransposons and suggest that these have played a major role in mating-system transitions, by facilitating multiple rearrangements of the mat locus.