Schistosome W-linked genes inform temporal dynamics of sex chromosome evolution and suggest candidate for sex determination Elkrewi, Marwan N ; https://orcid.org/0000-0002-5328-7231 Moldovan, Mikhail A. ; https://orcid.org/0000-0002-8876-6494 Picard, Marion A L ; https://orcid.org/0000-0002-8101-2518 Vicoso, Beatriz ; https://orcid.org/0000-0002-4579-8306 sex chromosomes evolutionary strata W-linked gene sex determining gene schistosome parasites ddc:610 Schistosomes, the human parasites responsible for snail fever, are female-heterogametic. Different parts of their ZW sex chromosomes have stopped recombining in distinct lineages, creating “evolutionary strata” of various ages. Although the Z-chromosome is well characterized at the genomic and molecular level, the W-chromosome has remained largely unstudied from an evolutionary perspective, as only a few W-linked genes have been detected outside of the model species Schistosoma mansoni. Here, we characterize the gene content and evolution of the W-chromosomes of S. mansoni and of the divergent species S. japonicum. We use a combined RNA/DNA k-mer based pipeline to assemble around 100 candidate W-specific transcripts in each of the species. About half of them map to known protein coding genes, the majority homologous to S. mansoni Z-linked genes. We perform an extended analysis of the evolutionary strata present in the two species (including characterizing a previously undetected young stratum in S. japonicum) to infer patterns of sequence and expression evolution of W-linked genes at different time points after recombination was lost. W-linked genes show evidence of degeneration, including high rates of protein evolution and reduced expression. Most are found in young lineage-specific strata, with only a few high expression ancestral W-genes remaining, consistent with the progressive erosion of nonrecombining regions. Among these, the splicing factor u2af2 stands out as a promising candidate for primary sex determination, opening new avenues for understanding the molecular basis of the reproductive biology of this group. Oxford University Press 2021 info:eu-repo/semantics/article doc-type:Article Article http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/10167 https://research-explorer.ista.ac.at/download/10167/11352 Elkrewi MN, Moldovan MA, Picard MAL, Vicoso B. Schistosome W-linked genes inform temporal dynamics of sex chromosome evolution and suggest candidate for sex determination. <i>Molecular Biology and Evolution</i>. 2021;138(12):5345-5358. doi:<a href="https://doi.org/10.1093/molbev/msab178">10.1093/molbev/msab178</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1093/molbev/msab178 info:eu-repo/semantics/altIdentifier/issn/0737-4038 info:eu-repo/semantics/altIdentifier/e-issn/1537-1719 info:eu-repo/semantics/altIdentifier/wos/000741368600009 info:eu-repo/semantics/altIdentifier/pmid/34146097 https://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess