Comparative Transcriptomics of Gonads Reveals the Molecular Mechanisms Underlying Gonadal Development in Giant Freshwater Prawns (Macrobrachium rosenbergii)

The giant freshwater prawn, Macrobrachium rosenbergii, is a prawn that has economic significance throughout the world. It exhibits sex-related growth dimorphism, whereby the males grow significantly more rapidly than the females. Therefore, a study on the molecular regulatory mechanism, which underlies the sexual differentiation of M. rosenbergii, is of both scientific and commercial importance. However, a scarcity of genomic and transcriptomic resources severely limits our knowledge of the sexual differentiation mechanisms in M. rosenbergii. Here, transcriptome sequencing of several gonadic samples of males and females in M. rosenbergii was performed to investigate the molecular basis underlying gonadal development. Our results showed that 2149 unigenes presented as differentially expressed genes (DEGs) in the ovaries of females compared to the testes of males, which contained 484 down-regulated and 1665 up-regulated genes. Enrichment analysis of DEGs revealed many of these genes to be related to sexual differentiation and gonadal development. From our transcriptome analyses, and as confirmed by quantitative real-time PCR, male-related genes (Mrr, MRPINK, IR, IAGBP, TESKI, and dsx) in the testes were significantly up-regulated, and female-related genes (ERR, Sxl3, cyclinB, Dmrt99B, PPP2A, and ADCY9) in the ovaries were also significantly up-regulated. This indicates the potential role these genes play in the gonadal development of M. rosenbergii. Furthermore, multiple signal transduction pathways relating to gonadal maturation and spermatogenesis, including MAPK, were identified herein. Our data also supports previous ideas that IAG and IAGBP-IR signaling schemes could help in the regulation of testis' development in M. rosenbergii and the ERR gene could regulate ovarian development by affecting the expression of cyclinB, PPP2A, and ADCY9. The data from this study provides incredibly usefully genomic resources for future research on the sexual differentiation and practical aquaculture of M. rosenbergii.