Transcriptome profiling of Symbion pandora (phylum Cycliophora): insights from a differential gene expression analysis
Cycliophorans are characterized by a complex life cycle that involves an asexual generation and a sexual generation. The most prominent life cycle stage in both generations is the so-called feeding stage. Using RNA-Seq, we profiled differential gene expression between feeding stages from asexual and sexual generations to study this intergenerational shift. For this, we also generated a reference transcriptome for the cycliophoran Symbion pandora. We found that a total of 2660 contigs (more than 10% of the total transcriptome) correspond to genes that are expressed differentially in the feeding stages from the asexual generation as compared to the sexual feeding stages. Among these, 1236 genes are upregulated in the asexual stages as compared to the sexual stages. Conversely, 1424 genes are upregulated in the sexual stages as compared to the asexual stages. The asexual stages express genes predominantly related to RNA processing and splicing as well as protein folding, which suggests a high degree of regulation at the transcriptional and post-transcriptional levels. In marked contrast, the sexual stages highly express genes related to signal transduction and neurotransmission. This is the first time that a large whole-transcriptome RNA-Seq expression dataset has been generated for any cycliophoran. Moreover, this study provides important information for further studies on the molecular mechanisms that are involved in the shift from asexual to sexual generations in this still enigmatic group.
KeywordsSexual vs. asexual reproduction Life cycle Transcriptomics RNA sequencing Spiralia Lophotrochozoa
We are grateful to the generous support by the staff from The Sven Lovén Centre for Marine Sciences at the University of Gothenburg. The authors also thank Birgitte Rubak and Stine Elle (both Copenhagen) for providing the line drawings. We thank Kevin Kocot (University of Alabama, USA) for his helpful comments on a preliminary version of this article.
RCN and HR conceived of the study and participated in its design and coordination and drafted the manuscript. RCN is the main coordinator of the project, prepared the material for sequencing, coordinated the molecular genetic studies and analysed the data. SS analysed the data. JCG performed statistical analysis and helped to draft the manuscript. All authors read and approved the final manuscript.
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Conflict of interest
The authors declare that they have no competing interests.
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