Dimorphic Expression of<i> dmrt1</i> and <i>cyp19a1 </i>(Ovarian Aromatase) during Early Gonadal Development in Pejerrey, <i>Odontesthes bonariensis</i>

Abstract

The pejerrey (Odontesthes bonariensis) is a teleost fish with strong temperature-dependent sex determination (TSD). Several studies have shown that dmrt1 and gonadal aromatase (cyp19a1) are implicated in the sex differentiation process in teleosts but little is known on the expression balance and endocrine regulation of these two genes during TSD. This study was designed to clarify the expression patterns of both genes during gonadal sex differentiation of pejerrey reared at female-, male- and mixed-sex-producing temperatures (FPT, MPT, and MixPT, respectively). The expression of dmrt1 was found to be significantly higher during gonadal sex differentiation at MPT compared to FPT. Conversely, cyp19a1 expression clearly increased during differentiation at FPT but not at MPT. The expression of both genes at MixPT showed a dimorphic profile with individual values resembling either those at the MPT or FPT. Administration of exogenous 17β-estradiol down- and up-regulated the expression of dmrt1 and cyp19a1, respectively, regardless of temperature, and rescued the female phenotype at the MPT. However, treatment with the aromatase inhibitor Fadrozole caused masculinization without changing the pattern of gene expression. These results are strong evidence of the involvement of both genes in the gonadal differentiation process of pejerrey. The involvement of estradiol is discussed.

Environmental Effects on Fish Sex Determination and Differentiation

“…2 ) . Dmrt1 expression in the pejerrey O. bonariensis showed an increase in fry reared at the MPT of 29 ° C after 4 wph before the increase of Cyp19a1 evidenced in fish at FPT of 17 ° C which has reduced levels of Dmrt1 [Fernandino et al, 2008b]. Recently in medaka temperatures of 32 ° C caused 40% increase in the proportion of males [Hattori et al, 2007].…”

“…2 ) [D'Cotta et al, 2001b;Baroiller et al, 2008]. Elevated cyp19a1 levels have also been found in the pejerrey O. bonariensis fry reared at female promoting temperatures (FPT) of 17 ° C after 6 wph, preceding histological differentiation [Karube et al, 2007;Fernandino et al, 2008b]. Similarly high expression levels of cyp19a1 were found in larvae of Japanese flounder reared at feminizing low temperatures of 18 ° C, but down-regulation occurred in offspring reared at the elevated male promoting temperatures of 27 ° C [Kitano et al, 1999].…”

Thermal and Endocrine Regulation of Gonadal Apoptosis during Sex Differentiation in Pejerrey <b><i>Odontesthes</i></b> <b><i>bonariensis</i></b>

“…The aromatase inhibitor fadrozole (Afema, Novartis, Basel, Switzerland) was incorporated in the powder diet at 500 μg/g of diet, which was given to the experimental group ad libitum twice a day as described above between 2 and 10 wah. The fadrozole concentration and administration methods were based on previous studies on pejerrey [Fernandino et al, 2008b] and other teleosts [Uchida et al, 2004]. Larvae were fed untreated diet from 10 wah until the end of the experiment.…”

The effect of rearing temperature in larval development of pejerrey, Odontesthes bonariensis: morphological indicators of development

“…Pejerrey larvae reared from hatching at 13-19ºC produced 100% females, at 29ºC 100% males, and mixed sex proportions at intermediate temperatures, 24-25ºC (Strüssmann et al, 1996b(Strüssmann et al, , 1997Karube et al, 2007;Fernandino et al, 2008a). Sex differentiation is also accelerated by rearing temperature; the ovarian differentiation occurs before at 24ºC than at 17ºC, whereas testis development takes place before at 29ºC than at 24ºC (Ito et al, 2005;Fernandino et al, 2008b). Also, germ cell degeneration usually became histologically recognizable after one to two weeks of exposure to temperatures higher than 29ºC and became more severe with increasing duration of exposure (see Strüssmann et al, 2010).…”