Abstract
The crustacean male-specific androgenic gland (AG) regulates sexual differentiation. In the prawn Macrobrachium rosenbergii, silencing an AG-specific insulin-like encoding transcript (Mr-IAG) inhibited the development of male sexual characters, suggesting that Mr-IAG is a key androgenic hormone. We used recombinant pro-Mr-IAG peptide to generate antibodies that recognized the peptide in AG cells and extracts, as verified by mass spectrometry. We revealed the temporal expression pattern of Mr-IAG and studied its relevance to the timetable of sex differentiation processes in juveniles and after puberty. Mr-IAG was expressed from as early as 20 days after metamorphosis, prior to the appearance of external male sexual characters. Mr-IAG expression was lower in the less reproductively active orange-clawed males than in both the dominant blue-clawed males and the actively sneak mating small males. These results suggest a role for Mr-IAG both in the timing of male sexual differentiation and in regulating reproductive strategies.
Highlights
Sexual differentiation in the animal kingdom can be defined as a series of events whereby the sexually indeterminate embryo progressively acquires male or female characteristics in the gonads, genital tract, and external genitalia
The presence of the protein encoded by Mr-IAG was demonstrated by using an antibody raised against recombinant pro-Mr-IAG in rabbit, which recognized a specific band of ∼20 kDa both in the cleaned recombinant protein and in extracts from hypertrophied androgenic gland (AG) (Figure 1(a); lanes 1 and 2, resp.)
No signal was detected in the sperm duct (Figure 1(c); SD) or in the other cells surrounding the AG; the nuclei of all these cells are stained blue with diamidino phenylindole (DAPI)
Summary
Sexual differentiation in the animal kingdom can be defined as a series of events whereby the sexually indeterminate embryo progressively acquires male or female characteristics in the gonads, genital tract, and external genitalia. Anti-Mullerian hormone (AMH) and testosterone are the two key hormones produced by the testes in optimal concentrations during a critical time frame in early gestation to ensure male development. These two hormones are produced in parallel to the developmental expression of their cognate receptors in target tissues [3]. In addition to these two factors, an array of peptidic and steroidal sex hormones governs the process of sexual differentiation in all vertebrates, but with differences between and within phyla
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