Evolution of Plants and Fungi, Ruhr-University Bochum, Bochum, Germany.
Environmental Genomics, Germany and Max Planck Institute for Evolutionary Biology, Botanical Institute, Christian-Albrechts University of Kiel, Plön, Germany.
BMC Genomics. 2023 Jun 13;24(1):321. doi: 10.1186/s12864-023-09387-1.
The Ustilaginales comprise hundreds of plant-parasitic fungi with a characteristic life cycle that directly links sexual reproduction and parasitism: One of the two mating-type loci codes for a transcription factor that not only facilitates mating, but also initiates the infection process. However, several species within the Ustilaginales have no described parasitic stage and were historically assigned to the genus Pseudozyma. Molecular studies have shown that the group is polyphyletic, with members being scattered in various lineages of the Ustilaginales. Together with recent findings of conserved fungal effectors in these non-parasitic species, this raises the question if parasitism has been lost recently and in multiple independent events or if there are hitherto undescribed parasitic stages of these fungi.
In this study, we sequenced genomes of five Pseudozyma species together with six parasitic species from the Ustilaginales to compare their genomic capability to perform two central functions in sexual reproduction: mating and meiosis. While the loss of sexual capability is assumed in certain lineages and asexual species are common in Asco- and Basidiomycota, we were able to successfully annotate potentially functional mating and meiosis genes that are conserved throughout the whole group.
Our data suggest that at least the key functions of a sexual lifestyle are maintained in the analyzed genomes, challenging the current understanding of the so-called asexual species with respect to their evolution and ecological role.
锈菌目包含数百种寄生植物的真菌，其特征性生命周期直接将有性繁殖和寄生联系在一起：两个交配型基因座中的一个编码转录因子，该因子不仅促进交配，而且还启动感染过程。然而，锈菌目中的几个物种没有描述的寄生阶段，历史上被分配到假丝酵母属。分子研究表明，该组是多系的，成员分散在锈菌目的各个谱系中。与这些非寄生物种中保守真菌效应物的最新发现一起，这提出了一个问题，即寄生是否最近在多个独立事件中丢失，或者这些真菌是否存在迄今为止未描述的寄生阶段。
在这项研究中，我们对五个假丝酵母物种的基因组进行了测序，同时对锈菌目中的六个寄生物种进行了测序，以比较它们在有性繁殖中执行两个核心功能的基因组能力：交配和减数分裂。虽然某些谱系中丧失了有性能力，且无性物种在子囊菌和担子菌中很常见，但我们能够成功注释潜在的功能交配和减数分裂基因，这些基因在整个群体中是保守的。
我们的数据表明，至少在分析的基因组中维持了有性生活方式的关键功能，这对所谓的无性物种的进化和生态作用的现有理解提出了挑战。
