Soya isoflavones, genistein and daidzein, induce differential transcriptional modulation in the ovary and testis of zebrafish Danio rerio

Abstract

Most research into the effects of phytochemical isoflavones has focussed on endocrine disruptions, and especially on oestrogenic imbalances; however, little is known about their effects on other molecular signals such as transcriptional coregulators and choriolytic enzymatic pathways, which are also important in reproductive processes. In male and female zebrafish Danio rerio, the soya isoflavones genistein and daidzein (provided at 10 mg l-1 for 15 d) modulated the basal expression levels of oestrogen receptor transcripts (ERβ) in variable and differential ways. Exposure to genistein resulted in decreased levels of ERβ in the zebrafish ovary; conversely, this isoflavone increased the basal expression levels of the hatching enzyme (HE1) in both gonads. On the other hand, daidzein increased the basal expression levels of the bromodomain testis-specific gene (BRDT) in the male gonad, but not in the ovary. Both isoflavones also differentially modulated (up-down regulations) the basal expression patterns of the 3 molecular signals studied in other regions of the body (e.g. head, digestive system, skeletal musculature). Despite all these transcriptional imbalances, neither of the phytoestrogens modified gonadal histomorphology or the baseline histochemical pattern of proteins, carbohydrates and glycoconjugates distributed in either the vitelline structures or in the developing and maturing germ cells of Danio rerio.