Changes in expression of steroid receptors and aromatase in Atlantic cod during a maturation cycle

A significant hurdle that remains in Atlantic cod farming is precocious maturation of the fish, which results in decreased growth rates and reduced flesh quality. In order to develop more effective methods to deal with this issue it will be important to improve our knowledge of the hormonal regulation involved in sexual maturation. The sex steroids androgen and oestrogen are mainly produced in the gonads and plasma levels of these hormones are known to vary during maturation of the testis. Androgen receptor (ar) and estrogen receptors (er) belong to the nuclear receptor superfamily and operate as ligand-activated transcription factors. In the gonads, these receptors play a key role in mediating the activity of steroid hormones during sexual maturation. The enzyme P450 aromatase (cyp19) is also crucial for this process, as it is responsible for estrogen production from an androgen substrate. In the present study we performed quantitative real-time PCR (qPCR) analysis to examine the relative expression levels of ar, er, and cyp19 in the testis and ovaries of two-year old Atlantic cod during a complete maturation cycle. This study will shed light on the molecular basis of gonadal maturation in this species.