Molecular characterization and expression patterns of nuclear androgen receptors in the ovoviviparous black rockfish Sebastes schlegelii

nARs are ligand-activated transcription factors associated with gonadal development and reproductive regulation.In this study,two nuclear androgen receptor genes(ara and arb)were cloned from an ovoviviparous teleost,black rockfish(Sebastes schlegelii).The phylogenetic analysis of nARs showed that nARαand nARβclustered into teleost nARαand nARβ,respectively,but differed from the nARs of tetrapods.Four module domains of the nuclear receptor superfamily are present in the black rockfish nARs,an N-terminal domain(NTD),a DNA-binding domain(DBD),a hinge region(HR)and a ligand-binding domain(LBD).Among the four domains,only the DBD and LBD of nARαand nARβare relatively conserved.Tissue distribution analysis revealed that ara was mainly expressed in the gonad,muscle,intestine and kidney in males and in female,while arb was mainly detected in the gonad,followed by the intestine,kidney and head kidney.During the gonadal development process,the expression levels of ara and arb were significantly decreased from the regenerating to late stages of spermatogenesis and significantly increased in the degeneration stage in the testis(P<0.05).In the ovary,the expression levels of ara and arb were not significantly different in different stages.In situ hybridization revealed that in black rockfish,both ara and arb transcripts were localized to the Sertoli cells of the testis in black rockfish.In general,the present study is the first to characterize and analyse the expression of nuclear androgen receptors,including ara and arb,in black rockfish.