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bioRxiv · 10.1101/2020.11.24.396218

Heterochiasmy facilitated the establishment of gsdf as a novel sex determining gene in Atlantic halibut

Edvardsen, R. B.·Wallerman, O.·Furmanek, T.·Kleppe, L.·Jern, P.·Wallberg, A.·Kjaerner-Semb, E.·Maehle, S.·Olausson, S. K.·Sundstrom, E.·Harboe, T.·Mangor-Jensen, R.·Mogster, M.·Perrichon, P.·Norberg, B.·Rubin, C.-J.
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Abstract

Atlantic Halibut (Hippoglossus hippoglossus) has a X/Y genetic sex determination system, but the sex determining factor is not known. We produced a high-quality genome assembly and identified parts of chromosome 13 as the Y chromosome due to sequence divergence between sexes and segregation of sex genotypes in pedigrees. Linkage analysis revealed that all chromosomes exhibit heterochiasmy, i.e. male- and female restricted meiotic recombination intervals (MRR/FRR). We show that FRR/MRR intervals differ in nucleotide diversity and repeat class content and that this is true also for other Pleuronectidae species. We further show that remnants of a Gypsy-like transposable element insertion on chr13 promotes early male specific expression of gonadal somatic cell derived factor (gsdf). Less than 4 MYA, this male-determining element evolved on an autosomal FRR segment featuring pre-existing male meiotic recombination barriers, thereby creating a Y chromosome. We propose that heterochiasmy may facilitate the evolution of genetic sex determination systems.

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Edvardsen, R. B., Wallerman, O., Furmanek, T., Kleppe, L., Jern, P., Wallberg, A., Kjaerner-Semb, E., Maehle, S., Olausson, S. K., Sundstrom, E., Harboe, T., Mangor-Jensen, R., Mogster, M., Perrichon, P., Norberg, B., Rubin, C.-J.. 2020-11-24. Heterochiasmy facilitated the establishment of gsdf as a novel sex determining gene in Atlantic halibut. https://doi.org/10.1101/2020.11.24.396218

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