Biology subjects

Soukup, V.

Publications and source records attributed to Soukup, V..

4 recordsLinked to original sources

bioRxiv2026

Continuous pharyngeal endoderm links external and internal gills

Amphibians develop both external and internal gills during ontogeny, offering an opportunity to investigate the developmental relationship between these positionally distinct respiratory organs. Although internal gills of vertebrates are widely accepted to arise from pharyngeal endoderm, external gills have long been regarded as purely ectodermal outgrowths, obscuring their relationship to other vertebrate gills. Here, we combine histological analysis with direct lineage tracing in the Mexican axolotl (Ambystoma mexicanum) and the African clawed frog (Xenopus laevis) to resolve the embryonic origin of amphibian gills. We show that the external gill develops as a continuous epithelial extension of the pharyngeal endoderm, which forms its basal epithelium and reaches the distal gill tip. In the frog, this extension remains continuous with the epithelium giving rise to the internal gills. Rather than representing separate epithelial structures, external and internal gills therefore arise from a shared epithelial domain of the pharyngeal endoderm. These findings resolve a longstanding question concerning the embryonic origin of amphibian gills and provide a developmental viewpoint for understanding how spatially diverse vertebrate gills can evolve through repeated modification of a conserved endodermal tissue.

developmental biology↗

bioRxiv2024

Induction of ectopic external gills and tetrapodomorph-like skeletal elements through homeotic transformations in the salamander branchial region

Homeotic transformations are morphological changes associated with alterations of identities of segments in serially repeated systems and these changes may be a source of modifications in body plan evolution. Retinoic acid (RA) signaling has previously been shown to induce homeotic transformations in the vertebral column, although its role in other vertebrate segmented systems remains unexplored. Here, we use pharmacological inhibition of RA receptors to study homeotic transformations in the larval salamander branchial region. This region normally contains three pairs of external gills supported by the underlying skeleton, however upon treatments we observe induction of ectopic outgrowths in the posterior portion of the apparatus. We characterize these outgrowths as ectopically induced fourth external gills on the position of the otherwise gill-free segment. This induction is further associated with transformations and appearance of cartilaginous elements that phenocopy similar elements in fossil stem amphibians and tetrapodomorphs. These experimentally instigated morphological changes qualify as homeotic transformations in the branchial region and present re-emergence of features that were lost prior to the origin of modern tetrapods. More broadly, our results point to RA signaling as a potent driver regulating the number and composition of pharyngeal segments and thus controlling the evolution of the vertebrate pharyngeal apparatus.

developmental biology↗

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↗