Abstract
Sex differentiation in teleost fishes occurs in response to sex determination signals, which induce the gonad to develop as either an ovary or testis. However, sex differentiation mechanisms in fishes are diverse, and information on gonad differentiation in sex changing fishes remains limited. The orange-spotted grouper (Epinephelus coioides) is a protogynous hermaphroditic fish that provides an ideal model for investigating gonad differentiation in vertebrates. In this study, Transcriptome data showed that expression levels of amh and amhrII in gonads were increased during sex differentiation. Then we investigated the effect of overexpression anti-Müllerian hormone (Amh) on gonad development in juvenile orange-spotted groupers. Expression levels of female-related genes and serum 17β-estradiol levels were decreased, while expression of male-related genes and serum 11-ketotestosterone levels were increased in fish fed with amh-plasmid. Overexpression of Amh was also promoted the spermatogonia proliferation and induced the development of male gonads in undifferentiated orange-spotted groupers, but that this male tendency was preceded by female differentiation. In summary, these results illustrated that Amh overexpression by amh-plasmid feeding induced male gonad development in undifferentiated groupers.
Highlights
Sexual reproduction depends on the production of two types of gametes, which in turn rely on the specialized functions of the female and male gonads
We found that expression levels of both amh and amh receptor type II gene (amhrII) were increased during sex differentiation in gonads (Figure 2)
There are positive and negative controls (Figures 8P,Q). These results suggested that anti-Müllerian hormone (Amh) overexpression induced the development of male gonads in undifferentiated orange-spotted groupers, but that this male tendency was preceded by female differentiation (Table 4)
Summary
Sexual reproduction depends on the production of two types of gametes, which in turn rely on the specialized functions of the female and male gonads. Sex determination leads to a binary choice of gonad fate, to form either an ovary or a testis. Administration of low doses of exogenous sex steroid hormones (androgens or estrogens) leads to sex reversal in medaka, and this method has demonstrated that sex steroid hormones play an important role in gonad differentiation in a wide variety of fish species [3,4,5]. Several of fishes show a negative correlation between amh and aromatase expression during the sex differentiation phase [11]. Higher levels of amh are correlated with lower cyp19a1a in zebrafish. These data indicate that amh is a candidate gene downregulating cyp19a1a, potentially leading to juvenile ovary-to-testis transformation [12]. The role of amh during fish sex differentiation remains unclear
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