Department of Invertebrate Zoology, St-Petersburg State University, Saint Petersburg, 199034, Russia.
Zoological Institute, Russian Academy of Sciences, Saint Petersburg, 199034, Russia.
Parasit Vectors. 2020 Nov 10;13(1):559. doi: 10.1186/s13071-020-04424-4.
Parasitic flatworms (Trematoda: Digenea) represent one of the most remarkable examples of drastic morphological diversity among the stages within a life cycle. Which genes are responsible for extreme differences in anatomy, physiology, behavior, and ecology among the stages? Here we report a comparative transcriptomic analysis of parthenogenetic and amphimictic generations in two evolutionary informative species of Digenea belonging to the family Psilostomatidae.
In this study the transcriptomes of rediae, cercariae and adult worm stages of Psilotrema simillimum and Sphaeridiotrema pseudoglobulus, were sequenced and analyzed. High-quality transcriptomes were generated, and the reference sets of protein-coding genes were used for differential expression analysis in order to identify stage-specific genes. Comparative analysis of gene sets, their expression dynamics and Gene Ontology enrichment analysis were performed for three life stages within each species and between the two species.
Reference transcriptomes for P. simillimum and S. pseudoglobulus include 21,433 and 46,424 sequences, respectively. Among 14,051 orthologous groups (OGs), 1354 are common and specific for two analyzed psilostomatid species, whereas 13 and 43 OGs were unique for P. simillimum and S. pseudoglobulus, respectively. In contrast to P. simillimum, where more than 60% of analyzed genes were active in the redia, cercaria and adult worm stages, in S. pseudoglobulus less than 40% of genes had such a ubiquitous expression pattern. In general, 7805 (36.41%) and 30,622 (65.96%) of genes were preferentially expressed in one of the analyzed stages of P. simillimum and S. pseudoglobulus, respectively. In both species 12 clusters of co-expressed genes were identified, and more than a half of the genes belonging to the reference sets were included into these clusters. Functional specialization of the life cycle stages was clearly supported by Gene Ontology enrichment analysis.
During the life cycles of the two species studied, most of the genes change their expression levels considerably, consequently the molecular signature of a stage is not only a unique set of expressed genes, but also the specific levels of their expression. Our results indicate unexpectedly high level of plasticity in gene regulation between closely related species. Transcriptomes of P. simillimum and S. pseudoglobulus provide high quality reference resource for future evolutionary studies and comparative analyses.
寄生虫扁形动物（吸虫纲：复殖目）代表了生命周期内各阶段形态多样性急剧变化的最显著例子之一。哪些基因导致了各阶段在解剖、生理、行为和生态方面的极端差异？在这里，我们报告了两种隶属于 Psilostomatidae 科的复殖目吸虫的单性生殖和两性生殖世代的比较转录组分析。
在这项研究中，测序并分析了 Psilotrema simillimum 和 Sphaeridiotrema pseudoglobulus 的前殖体、尾蚴和成虫阶段的转录组。生成了高质量的转录组，并使用差异表达分析来分析蛋白质编码基因的参考集，以鉴定特定阶段的基因。对每个物种的三个生命阶段和两个物种之间的基因集进行了比较分析、表达动态和基因本体论（GO）富集分析。
P. simillimum 和 S. pseudoglobulus 的参考转录组分别包含 21433 和 46424 个序列。在 14051 个直系同源群（OG）中，有 1354 个是两种分析的 Psilostomatidae 物种所共有的，而 13 和 43 个 OG 分别是 P. simillimum 和 S. pseudoglobulus 所特有的。与 P. simillimum 不同，在 P. simillimum 中，超过 60%的分析基因在前殖体、尾蚴和成虫阶段都有活性，而在 S. pseudoglobulus 中，不到 40%的基因具有如此普遍的表达模式。一般来说，P. simillimum 中有 7805（36.41%）和 S. pseudoglobulus 中有 30622（65.96%）个基因优先在分析的一个阶段表达。在这两个物种中，分别鉴定到 12 个共表达基因簇，并且属于参考集的基因中有一半以上被归入这些簇中。GO 富集分析清楚地支持了生命周期阶段的功能专业化。
在研究的两个物种的生命周期中，大多数基因的表达水平发生了很大变化，因此阶段的分子特征不仅是一组独特的表达基因，还有它们特定的表达水平。我们的结果表明，在密切相关的物种之间，基因调控的可塑性出乎意料地高。P. simillimum 和 S. pseudoglobulus 的转录组为未来的进化研究和比较分析提供了高质量的参考资源。
