Differential Expression Analysis and Identification of Sex-Related Genes by Gonad Transcriptome Sequencing in Estradiol-Treated and Non-Treated Ussuri Catfish Pseudobagrus Ussuriensis

The Ussuri catfish ( Pseudobagrus ussuriensis ) has an XX/XY sex determination system but its sex determination gene(s) remain unknown. To better understand the molecular sex determination mechanism, transcriptome analysis was conducted to obtain sex-related gene expression profiles. Transcriptome analyses were made of male and female developing/differentiating gonads by high-throughput RNA sequencing, including gonads from fish given an estradiol-induced sex reversal treatment. A total of 81,569 unigenes were assembled and 39,904 were significantly matched to known unique proteins by comparison with public databases. Twenty specifically expressed and 142 differentially expressed sex-related genes were extracted from annotated data by comparing the treatment groups. These genes are involved in spermatogenesis (e.g., Dnali1 , nectin3 , klhl10 , mybl1 , Katnal1 , Eno4 , Mns1 , Spag6 , Tsga10 , Septin7 ), oogenesis (e.g., Lagr5 , Fmn2 , Npm2 , zar1 , Fbxo5 , Fbxo43 , Prdx4 , Nrip1 , Lfng , Atrip ), gonadal development/differentiation (e.g., Cxcr4b , Hmgb2 , Cftr , Ch25h , brip1 , Prdm9 , Tdrd1 , Star , dmrt1 , Tut4 , Hsd17b12a , gdf9 , dnd , arf1 , Spata22 ), and estradiol response (e.g., Mmp14 , Lhcgr , vtg1 , vtg2 , esr2b , Piwil1 , Aifm1 , Hsf1 , gdf9 ). Dmrt1 and gdf9 may play an essential role in sex determination in P. ussuriensis . The expression patterns of six random genes were validated by quantitative real-time PCR, which confirmed the reliability and accuracy of the RNA-seq results. These data provide a valuable resource for future studies of gene expression and for understanding the molecular mechanism of sex determination/differentiation and gonadal development/differentiation (including hormone-induced sexual reversal) in Ussuri catfish. This has the potential to assist in producing monosex Ussuri catfish to increase aquacultural productivity.