Identification of genes involved in gonadal sex differentiation and the dimorphic expression pattern in undifferentiated gonads of Russian sturgeon<i>Acipenser gueldenstaedtii</i>Brandt &amp; Ratzeburg, 1833

Abstract

The establishment of a sexing technique at an early developmental stage is an important issue in sturgeon aquaculture, yet the mechanism of sex differentiation in sturgeons remains poorly understood. This study aimed to identify genes involved in gonadal sex differentiation and to investigate sexually dimorphic gene expression in undifferentiated gonads. RNA-seq analyses using next-generation sequencers were carried out on undifferentiated gonads of five 9-month-old juvenile Russian sturgeon Acipenser gueldenstaedtii. A total of 45 686 832 (8498 Mb) and 79 743 269 (7887 Mb) quality-controlled reads were obtained using Ion PGM and HiSeq 2000 sequencers, respectively, and were assembled into 338 648 contigs (N50: 532 b). tBLASTx analyses identified 26 transcripts potentially involved in gonadal differentiation. Read-mapping analyses were performed to obtain relative transcript levels (RPKM values). Multivariate analyses of the RPKM values of five transcripts (gsdf, dmrt1a, dmrt1b, foxl2 and cyp19a1a) showed that the five individuals could be separated into two distinct groups. One group, comprising two individuals, had increased levels of foxl2, hsd17b1 and cyp19a1a, suggesting differentiation into females. Alternatively, levels of gsdf were higher in the other three individuals, suggesting differentiation into males. We describe the levels of 26 transcripts potentially involved in gonadal differentiation in undifferentiated sturgeon gonads and suggest that levels of gsdf, foxl2, hsd17b1 and cyp19a1a are appropriate sexing markers for sturgeon at an early developmental stage.