Transcriptomic analyses of hermaphroditic gonads at different stages revealing candidate genes for sex differentiation and gonad growth/maturation in QN Orange scallops

Argopecten scallops are hermaphroditic bivalves and commercially important in aquaculture. Up to now, the molecular mechanism of sex differentiation and gonad growth/maturation in hermaphroditic animals is still largely unknown. In this study, we analyzed the transcriptome of the gonads at different stages of the QN Orange scallop, a new scallop strain selected from the hybrids between the bay scallop and the Peruvian scallop. Among sex differentiation-related genes, 5 transcription factors (TFs) (1 SOX, 2 FOXL and 2 GATA) and 2 TGF-beta s (2 BMP) were mainly expressed in the male part and 2 TFs (1 FOXL and 1GATA) and 2 TGF-beta s (2 BMP) were mainly expressed in the female part of the gonads. Among gonad growth/maturation related genes, 1 TF (GATA) might be only involved in male gonad growth/maturation, 8 TFs (1 SOX, 1 WNT, 2 FOXL and 4 GATA) and 3 TGF-beta s (1 GDF and 2 BMP) only participated in ovarian growth/maturation, 3TFs (1 SOX, 1 DMRT and 1 FOXL) and 2 TGF-beta s (1 GDF and 1 BMP) might be involved in both male and female gonad growth/maturation. Based on the results of transcriptome and qRT-PCR, 11 genes were screened to be involved in sex differentiation and 16 genes might be involved in gonad growth/maturation. The results of this study may provide new insights into the understanding of the mechanisms of sex differentiation and gonad growth/maturation in hermaphroditic scallops