Multi-genome comparisons reveal gain-and-loss evolution of anti-Mullerian hormone receptor type 2 as a candidate master sex-determining gene in Percidae
Résumé
Abstract Background The Percidae family comprises many fish species of major importance for aquaculture and fisheries. Based on three new chromosome-scale assemblies in Perca fluviatilis , Perca schrenkii , and Sander vitreus along with additional percid fish reference genomes, we provide an evolutionary and comparative genomic analysis of their sex-determination systems. Results We explored the fate of a duplicated anti-Mullerian hormone receptor type-2 gene ( amhr2bY ), previously suggested to be the master sex-determining (MSD) gene in P. flavescens . Phylogenetically related and structurally similar a mhr2 duplicates ( amhr2b ) were found in P. schrenkii and Sander lucioperca , potentially dating this duplication event to their last common ancestor around 19–27 Mya. In P. fluviatilis and S. vitreus , this amhr2b duplicate has been likely lost while it was subject to amplification in S. lucioperca . Analyses of the amhr2b locus in P. schrenkii suggest that this duplication could be also male-specific as it is in P. flavescens . In P. fluviatilis , a relatively small (100 kb) non-recombinant sex-determining region (SDR) was characterized on chromosome 18 using population-genomics approaches. This SDR is characterized by many male-specific single-nucleotide variations (SNVs) and no large duplication/insertion event, suggesting that P. fluviatilis has a male heterogametic sex-determination system (XX/XY), generated by allelic diversification. This SDR contains six annotated genes, including three ( c18h1orf198 , hsdl1 , tbc1d32 ) with higher expression in the testis than in the ovary. Conclusions Together, our results provide a new example of the highly dynamic sex chromosome turnover in teleosts and provide new genomic resources for Percidae, including sex-genotyping tools for all three known Perca species.
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