Department of Developmental Biochemistry, Biocenter, University of Wuerzburg, Am Hubland, 97074, Wuerzburg, Germany.
Reproductive and Molecular Biology Group, Department of Structural and Functional Biology, Institute of Biosciences, UNESP, Botucatu, Brazil.
Sci Rep. 2022 Mar 30;12(1):5408. doi: 10.1038/s41598-022-09314-6.
Fish are amongst vertebrates the group with the highest diversity of known sex-determining genes. Particularly, the genus Oryzias is a suitable taxon to understand how different sex determination genetic networks evolved in closely related species. Two closely related species, O. latipes and O. curvinotus, do not only share the same XX/XY sex chromosome system, but also the same male sex-determining gene, dmrt1bY. We performed whole mRNA transcriptomes and morphology analyses of the gonads of hybrids resulting from reciprocal crosses between O. latipes and O. curvinotus. XY male hybrids, presenting meiotic arrest and no production of sperm were sterile, and about 30% of the XY hybrids underwent male-to-female sex reversal. Both XX and XY hybrid females exhibited reduced fertility and developed ovotestis while aging. Transcriptome data showed that male-related genes are upregulated in the XX and XY female hybrids. The transcriptomes of both types of female and of the male gonads are characterized by upregulation of meiosis and germ cell differentiation genes. Differences in the parental species in the downstream pathways of sexual development could explain sex reversal, sterility, and the development of intersex gonads in the hybrids. We hypothesize that male-to-female sex reversal may be connected to a different development time between species at which dmrt1bY expression starts. Our results provide molecular clues for the proximate mechanisms of hybrid incompatibility and Haldane's rule.
鱼类是脊椎动物中性别决定基因多样性最高的群体之一。特别是稻属（Oryzias）是一个合适的分类单元，可以了解不同的性别决定遗传网络在亲缘关系密切的物种中是如何进化的。两个亲缘关系密切的物种，Oryzias latipes 和 Oryzias curvinotus，不仅共享相同的 XX/XY 性染色体系统，而且还共享相同的雄性性别决定基因 dmrt1bY。我们对来自 Oryzias latipes 和 Oryzias curvinotus 相互杂交的杂种的性腺进行了全 mRNA 转录组和形态分析。表现出减数分裂停滞且不产生精子的 XY 雄性杂种是不育的，约 30%的 XY 杂种发生了雄性到雌性的性反转。XX 和 XY 杂种雌性的生育能力降低，并随着年龄的增长发育出卵睾。转录组数据显示，雄性相关基因在 XX 和 XY 雌性杂种中上调。XX 和 XY 类型的雌性和雄性性腺的转录组均表现出减数分裂和生殖细胞分化基因的上调。性发育下游途径中亲本性别的差异可以解释性反转、不育和杂种中两性性腺的发育。我们假设雄性到雌性的性反转可能与 dmrt1bY 表达开始时物种之间不同的发育时间有关。我们的研究结果为杂种不亲和性和 Haldane 法则的近因机制提供了分子线索。
