Expression of vasa, piwi, and nanos during gametogenesis in Typosyllis antoni (Annelida, Syllidae)

Abstract

Although model species have proven to be crucial for developmental biology, the evo-devo approach requires a broader picture across phylogeny. Herein, we try to expand the range of studied annelids by presenting a transcriptome of Typosyllis antoni as a tool for the study of developmental and evolutionary processes in Syllidae. Moreover, we provide homologs of the stem-cell markers vasa, piwi, and nanos, and investigate their expression patterns in gamete-producing individuals for the first time in this group. We found no expression in females, while there is a distinct expression pattern in males. Based on this data, we argue that spermatogenesis starts in the gonads and finishes in the coelomic cavity, and it occurs simultaneously in a large number of segments. Surprisingly, no expression of the stem-cell markers was found in the segment addition zone of these reproducing animals (stolonizing). Preliminary explanations like a lack of growth during stolonization, or the absence of a common genetic program between germ and somatic stem cells, are discussed. Finally, no reservoir of primordial cells has been detected, suggesting a possible epigenic origin of the Primordial Germ Cells of this species, though this hypothesis needs to be further investigated.

Comparative transcriptomics in Syllidae (Annelida) indicates that posterior regeneration and regular growth are comparable, while anterior regeneration is a distinct process

“…These high duplication levels were probably a consequence of pooling different individuals for each sequencing library, which can introduce allelic variation, splicing differences, and assembly artefacts [73]. Nevertheless, our transcriptomic analyses relied on highly complete assemblies based on BUSCO criteria and the comparison with other annelid assemblies [57, 74, 75]; and, since we performed the differential expression analyses at the level of Trinity ‘genes’ (which sums up the expression values of all isoforms of a ‘gene’), this redundancy does not affect our results.…”

“…PL10, like vasa , piwi , and nanos , is one of the germline multipotency program genes [80]. These genes are linked to somatic differentiation and stem-cellness, and can be considered conserved markers of the SAZ in annelids [14, 26, 34, 48, 62, 74, 80, 81].…”

Expression of Piwi Genes during the Regeneration of Lineus sanguineus (Nemertea, Pilidiophora, Heteronemertea)

“…This is different from Drosophila, Dugesia, Hydra, and Pleurobrachia; however, L. sanguineus is not the only animal species with these genes silent in female gonads. For example, the Ta-piwi2 of Typosyllis antoni (Annelida) is expressed in male testes but not in female ovaries [50]. Unfortunately, no development of testes was observed in our experimental animals; thus, whether piwi genes of L. sanguineus, particularly Ls-piwi2 and Ls-piwi3, are expressed in male germlines remains to be studied.…”

On the Diversity of Phyllodocida (Annelida: Errantia), with a Focus on Glyceridae, Goniadidae, Nephtyidae, Polynoidae, Sphaerodoridae, Syllidae, and the Holoplanktonic Families

“…Accordingly, all hypotheses on the monophyly of the main groups within Syllidae (i.e., the five subfamilies and the main lineages within them) are highly congruent. This stable phylogenetic scenario allowed to trace the evolution of biological processes such as the reproductive modes and a large variety of regenerative abilities [500,[503][504][505].…”