Soukup, V. | Search bioRxiv

bioRxiv2021

Evolutionary conservation of maternal RNA localization in fishes and amphibians revealed by TOMO-Seq

Asymmetrical localization of biomolecules inside the egg, results in uneven cell division and establishment of many biological processes, cell types and the body plan. However, our knowledge about evolutionary conservation of localized mRNAs is still limited to a few candidates. Our goal was to compare localization profiles along the animal-vegetal axis of mature eggs from four models, Xenopus laevis, Danio rerio, Ambystoma mexicanum and Acipenser ruthenus using the spatial expression method called TOMO-Seq. We revealed that RNAs of many known important genes such as germ layer determinants, germ plasm factors and members of key signalling pathways, are localized in completely different profiles among the models. There was also a poor correlation between vegetally localized genes but a relatively good correlation between animally localized genes. These findings indicate that the regulation of embryonic development within the animal kingdom is highly diverse and cannot be deduced based on a single model.

developmental biology↗

bioRxiv2021

Evolution of the nitric oxide synthase family in vertebrates and novel insights in gill development

Nitric oxide (NO) is an ancestral key signaling molecule essential for life and has enormous versatility in biological systems, including cardiovascular homeostasis, neurotransmission, and immunity. Although our knowledge of nitric oxide synthases (Nos), the enzymes that synthesize NO in vivo, is substantial, the origin of a large and diversified repertoire of nos gene orthologs in fish with respect to tetrapods remains a puzzle. The recent identification of nos3 in the ray-finned fish spotted gar, which was considered lost in the ray-finned fish lineage, changed this perspective. This prompted us to explore nos gene evolution and expression in depth, surveying vertebrate species representing key evolutionary nodes. This study provides noteworthy findings: first, nos2 experienced several lineage-specific gene duplications and losses. Second, nos3 was found to be lost independently in two different teleost lineages, Elopomorpha and Clupeocephala. Third, the expression of at least one nos paralog in the gills of developing shark, bichir, sturgeon, and gar but not in arctic lamprey, suggest that nos expression in this organ likely arose in the last common ancestor of gnathostomes. These results provide a framework for continuing research on nos genes roles, highlighting subfunctionalization and reciprocal loss of function that occurred in different lineages during vertebrate genome duplications.

evolutionary biology↗