RNA-Seq-based transcriptome analysis of reproduction- and growth-related genes in Lateolabrax japonicus ovaries at four different ages

Comparison of differential expression genes in ovaries and testes of Pearlscale angelfish Centropyge vrolikii based on RNA-Seq analysis

Pearlscale angelfish Centropyge vrolikii is a kind of protogynous hermaphrodite fish with a natural sexual reversion. Under appropriate social conditions, a female fish can transform into a male fish spontaneously. It is an important prerequisite for artificial breeding to understand the process of its gonadal development and sexual reversion. Gonadal development is regulated by many sex-related genes. In this study, we used unreferenced RNA-Seq technology to sequence the ovary at the perinucleolus stage (O_II), ovary at the yolk vesicle stage (O_IV),IV and testis (T), respectively; screened the gonadal differential expression genes (DEGs); and analyzed the expression of these genes in different developmental stages of ovary and different sex gonads. The results showed that a total of 142,589 all-unigene samples were assembled, and gene annotation was performed by COG, GO, KEGG, KOG, Pfam, Swissprot, eggNOG, and NR functional database. Comparative analysis revealed that there were 1919 genes that were up-regulated and 1289 genes were down-regulated in comparison to O_IV vs O_II, while there were 3653 genes that were up-regulated and 2874 genes were down-regulated in comparison of O_IV vs T, there were 3345 genes that were up-regulated and 2995 genes were down-regulated in comparison of the O_II vs the T. At the same time, the results verified by RT-qPCR were consistent with the variation trend of transcriptome data. Among the results, amh, sox9b, dmrt1, dmrt2, cyp11a, cyp17a, and cyp19a were significantly expressed in the testes, while sox3, sox4, sox11, sox17, and hsd3b7 were significantly expressed in the ovaries. And, the expression of the amh, sox9b, dmrt2, and dmrt1 were low in the O_II and O_IV, while significantly increased during the ovotestis in the hermaphroditic period (O_T), and finally reached the highest level in pure testis after sex reversal. The expression of sox3, sox4, hsd3b7, sox11, and sox17 was significantly reduced during the hermaphroditic period (O_T). These results suggested that these genes may play an important role in the process of sex reversal. This study is helpful to further understand the molecular regulation mechanism of gonadal development and sexual reversion in Pearlscale angelfish and also provide important clues for future studies.

De novo transcriptome assembly from the gonads of a scleractinian coral, Euphyllia ancora: molecular mechanisms underlying scleractinian gametogenesis

BACKGROUND

Sexual reproduction of scleractinians has captured the attention of researchers and the general public for decades. Although extensive ecological data has been acquired, underlying molecular and cellular mechanisms remain largely unknown. In this study, to better understand mechanisms underlying gametogenesis, we isolated ovaries and testes at different developmental phases from a gonochoric coral, Euphyllia ancora, and adopted a transcriptomic approach to reveal sex- and phase-specific gene expression profiles. In particular, we explored genes associated with oocyte development and maturation, spermiogenesis, sperm motility / capacitation, and fertilization.

RESULTS

1.6 billion raw reads were obtained from 24 gonadal samples. De novo assembly of trimmed reads, and elimination of contigs derived from symbiotic dinoflagellates (Symbiodiniaceae) and other organisms yielded a reference E. ancora gonadal transcriptome of 35,802 contigs. Analysis of 4 developmental phases identified 2023 genes that were differentially expressed during oogenesis and 678 during spermatogenesis. In premature/mature ovaries, 631 genes were specifically upregulated, with 538 in mature testes. Upregulated genes included those involved in gametogenesis, gamete maturation, sperm motility / capacitation, and fertilization in other metazoans, including humans. Meanwhile, a large number of genes without homology to sequences in the SWISS-PROT database were also observed among upregulated genes in premature / mature ovaries and mature testes.

CONCLUSIONS

Our findings show that scleractinian gametogenesis shares many molecular characteristics with that of other metazoans, but it also possesses unique characteristics developed during cnidarian and/or scleractinian evolution. To the best of our knowledge, this study is the first to create a gonadal transcriptome assembly from any scleractinian. This study and associated datasets provide a foundation for future studies regarding gametogenesis and differences between male and female colonies from molecular and cellular perspectives. Furthermore, our transcriptome assembly will be a useful reference for future development of sex-specific and/or stage-specific germ cell markers that can be used in coral aquaculture and ecological studies.