Multi-genome comparisons reveal gain-and-loss evolution of the
anti-Mullerian hormone receptor type 2 gene, an old master sex
determining gene, in Percidae
Abstract
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. 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 amhr2 duplications (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 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 variants (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
testis than ovary. 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.