Molecular Cloning Of Partial CDNA Sequences Of Duplicate Genes Encoding Sterodigogenic Enzymes In Pelteobagrus Filvidraco And Their Expressions In Response To EE2

As is known, sex steroids play important roles in the process of sex differentiation, reproduction and growth in teleosts. Among these steroids, estrogens play critical role in sex differentiation and maturation of fish. P450c17α and 20β-HSD are the key steroidogenic enzymes responsible for the production of both sex steroid and progenstins. In the present study, duplicate genes of P450c17α(P450c17α-II) and 20β-HSD(20β-HSD-I) were isolated from the testis of yellow catfish(Pelteobagrus filvidraco) by RT-PCR and RACE methods. Results showed that, P450c17α-II and 20β-HSD-I fragment was 1203 bp and 1198 bp in length, respectively. Futher multiple alignments of vertebrate P450c17 s and 20β-HSDs revealed common domains conserved between tetrapods and fishes, respectively. Phylogenetic anaylsis revealed high homology of P450c17α-I/-II and 20β-HSD-I/-II between yellow catfish and other Siluriformes fishes. Tissue distribution analysis showed that, the expression of yellow catfish P450c17α-I and-II was restricted in testis and ovary, with additional expression of P450c17α-II in head kidney. However, yellow catfish 20β-HSD-I and-II were ubiquitously expressed in various tissues. Seasonal expression pattern analysis showed that, in both sexes, m RNA level of P450c17α-I peaked in January, P450c17α-II and 20β-HSD-II in May and 20β-HSD-I in November.With the frequency of human production and life, much attention has been focused on the potential health threats of endocrine disrupting chemicals capable of disrupting the endocrine systems of animal and human population. Research mostly focused on estrogenic compounds. In the present study, EE2, the estrogenic model compounds, was exposed to male yellow catfish adults for 28 days. The influence of EE2 on testicular development and spermatogenesis and the the expression levels of genes mentioned above were investigated by histology and quantitative real-time PCR, respectively. Result showed that, EE2 seriously impaired catfish testicular development(including spermatogenic arrest, germ cell reduce, somatic cell proliferation, etc) in a time dependent manner. Furthermore, the expressions of yellow catfish P450c17α-I,-II and 20β-HSD-I were dramatically suppressed by EE2.