Integration of RNAi and RNA-seq uncovers the regulation mechanism of DDX20 on vitellogenin expression in Scylla paramamosain

Abstract

Vitellogenesis in crustaceans is controlled by several steroid hormones. In humans, the expression of SF-1, a gene that regulates gonadal development and the synthesis of steroid hormones, is affected by DDX20. However, how the homologous gene FTZ-F1 is regulated by DDX20 and its association with vitellogenesis remains unknown in the mud crab Scylla paramamosain. In this study, SpDDX20 and SpFTZ-F1 were identified in the transcriptome of mature ovarian tissue from the mud crab. qRT-PCR results revealed that the expression levels of SpFTZ-F1 and SpVTG in the ovaries of crab in the experimental group injected with dsDDX20 (EO) were significantly higher (P < 0.05) than those in the negative control group injected with dsEGFP (NO) and the blank control group injected with SPSS (BO). The differentially expressed genes (DEGs) identified by comparative transcriptome analysis of the EO group and NO group were enriched into five pathways related to ovarian steroidogenesis. The expression of CYP17, CYP3A4, CYP1A1 and 3β-HSD were up-regulated in pathways related to steroid hormone production and biosynthesis. The expression of the INSR, IRS and PI3K genes in the insulin signaling pathway were significantly increased (P < 0.05). The expression level of the TGF-β gene was up-regulated (P < 0.05) in the transforming growth factor pathway, whereas the expression level of the Smad2 gene was down-regulated (P < 0.05). The expression of GnRHR, GS, AC and PKA genes in the gonadotropin-releasing hormone signaling pathway were up-regulated. Our data provide a foundation for investigating the relationship between DDX20 and FTZ-F1 in the regulation of vitellogenin expression in S. paramamosain.