Ascidians with very similar embryos but highly divergent genomes are thought to have undergone extensive developmental system drift. We compared, in four species (Ciona and Phallusia for Phlebobranchia, Molgula and Halocynthia for Stolidobranchia), gene expression and gene regulation for a network of six transcription factors regulating peripheral nervous system (PNS) formation in Ciona. All genes, but one in Molgula, were expressed in the PNS with some differences correlating with phylogenetic distance. Cross-species transgenesis indicated strong levels of conservation, except in Molgula, in gene regulation despite lack of sequence conservation of the enhancers. Developmental system drift in ascidians is thus higher for gene regulation than for gene expression; and is impacted not only by phylogenetic distance, but also in a clade-specific manner and unevenly within a network. Finally, considering that Molgula is divergent in our analyses, this suggests deep conservation of developmental mechanisms in ascidians after 390 My of separate evolution.
- Sébastien Darras
- Sébastien Darras
- Joshua F Coulcher
- Sébastien Darras
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Shigehiro Kuraku, RIKEN Center for Biosystems Dynamics Research, Japan
- Received: May 21, 2020
- Accepted: November 13, 2020
- Accepted Manuscript published: November 16, 2020 (version 1)
© 2020, Coulcher et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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