title: Evolutionary Changes in Sensitivity to Hormonally Induced Gonadal Sex Reversal in a Frog Species.
abstract: The Japanese frog Glandirana rugosa is unique in that it shows geographic variation in sex chromosome differentiation and heterogametic sex determination. To elucidate the cause of interpopulation differences in gonadal sex differentiation, we investigated hormonally induced sex reversal and the expression patterns of genes associated with sex determination during early tadpole development. We found that sex reversal was easily induced in XX females and XY males of 2 forms (West-Japan and East-Japan) of G. rugosa with the ancestral homomorphic sex chromosomes under male heterogametic sex determination. During sex reversal, expression of CYP19 and/or FOXL2 was dependent on the phenotypic sex of the gonad. In contrast, sex reversal was not induced in ZW females of a population with a heteromorphic ZW sex chromosome system or in XX females or XY males in a population with a heteromorphic XY sex chromosome system. The latter 2 populations are evolutionarily derived forms. These results indicate an evolutionary direction for the gonadal sex differentiation mechanism. The original system was highly sensitive to sex hormones and allowed almost complete sex reversal. From this ancestral form, a new system evolved that was resistant to hormones and showed a change in the heterogametic sex and the sex chromosome differentiation mechanism.
authors.affiliation: Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Miura
authors.forename: Hiromi
authors.initials: H
authors.lastname: Ohtani
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Ogata
authors.forename: Tariq
authors.initials: T
authors.lastname: Ezaz
mesh_terms: D000818:Animals; D005075:Biological Evolution; D012739:Gonadal Steroid Hormones / Q000819:agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology; D006066:Gonads / Q000187:drug effects* / Q000502:physiology*; D007621:Karyotyping; D008297:Male; D011898:Ranidae; D012730:Sex Chromosomes / Q000235:genetics; D019849:Sex Determination Processes / Q000187:drug effects* / Q000235:genetics; D012733:Sex Differentiation / Q000187:drug effects* / Q000235:genetics
chemical_list: D012739:Gonadal Steroid Hormones