Department of Botany and Plant Pathology, College of Agricultural Sciences, Oregon State University, Oregon, USA.
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland, BC, Canada.
Sci Rep. 2021 Feb 5;11(1):3217. doi: 10.1038/s41598-021-82607-4.
The zoosporic obligate endoparasites, Olpidium, hold a pivotal position to the reconstruction of the flagellum loss in fungi, one of the key morphological transitions associated with the colonization of land by the early fungi. We generated genome and transcriptome data from non-axenic zoospores of Olpidium bornovanus and used a metagenome approach to extract phylogenetically informative fungal markers. Our phylogenetic reconstruction strongly supported Olpidium as the closest zoosporic relative of the non-flagellated terrestrial fungi. Super-alignment analyses resolved Olpidium as sister to the non-flagellated terrestrial fungi, whereas a super-tree approach recovered different placements of Olpidium, but without strong support. Further investigations detected little conflicting signal among the sampled markers but revealed a potential polytomy in early fungal evolution associated with the branching order among Olpidium, Zoopagomycota and Mucoromycota. The branches defining the evolutionary relationships of these lineages were characterized by short branch lengths and low phylogenetic content and received equivocal support for alternative phylogenetic hypotheses from individual markers. These nodes were marked by important morphological innovations, including the transition to hyphal growth and the loss of flagellum, which enabled early fungi to explore new niches and resulted in rapid and temporally concurrent Precambrian diversifications of the ancestors of several phyla of fungi.
游动孢子专性内寄生菌 Olpidium 在重建真菌鞭毛丧失方面具有关键地位，这是与早期真菌在陆地定殖相关的关键形态转变之一。我们从 Olpidium bornovanus 的非共生游动孢子中生成了基因组和转录组数据，并采用宏基因组方法提取了具有系统发育信息的真菌标记物。我们的系统发育重建强烈支持 Olpidium 是无鞭毛陆生真菌的最接近的游动孢子亲缘关系。超级对齐分析将 Olpidium 确定为无鞭毛陆生真菌的姐妹群，而超级树方法则恢复了 Olpidium 的不同位置，但没有得到强有力的支持。进一步的研究检测到采样标记物之间几乎没有冲突的信号，但揭示了与 Olpidium、Zoopagomycota 和 Mucoromycota 分支顺序相关的早期真菌进化中的潜在并系现象。定义这些谱系进化关系的分支具有短分支长度和低系统发育含量的特点，并且来自单个标记物的替代系统发育假设的支持具有模棱两可性。这些节点的特征是重要的形态创新，包括向菌丝生长和鞭毛丧失的转变，这使早期真菌能够探索新的生态位，并导致几个真菌门的祖先在寒武纪迅速和同时多样化。
