Full-length gonad transcriptome analysis of Amur sturgeon Dmrt family genes: identification, characterization, and expression patterns during gonadal differentiation

Genome-wide identification and expression profiles of sex-related gene families in the Pacific abalone Haliotis discus hannai

In recent years, members of the Dmrt family, TGF-β superfamily and Sox family have been recognized as crucial genes for sex determination/differentiation across diverse animal species. Nevertheless, knowledge regarding the abundance and potential functions of these genes in abalone remains limited. In this study, a total of 5, 10, and 7 members of the Dmrt family, the TGF-β superfamily and the Sox family, respectively, were identified in the Pacific abalone Haliotis discus hannai. Sequence characteristics, phylogenetic relationships and spatiotemporal expression profiles of these genes were investigated. Notably, HdDmrt-04 (Dmrt1/1L-like) emerged as a potential mollusc-specific gene with a preponderance for expression in the testis. Interestingly, none of the TGF-β superfamily members exhibited specific or elevated expression in the gonads, highlighting the need for further investigation into their role in abalone sex differentiation. The Sox proteins in H. discus hannai were categorized into 7 subfamilies: B1, B2, C, D, E, F, and H. Among them, HdSox-07 (SoxH-like) was observed to play a crucial role in testis development, while HdSox-03 (SoxB1-like) and HdSox-04 (SoxC-like) probably cooperate in abalone ovary development. Taken together, the results of the present study suggested that HdDmrt-04 and HdSox-07 can be used as male-specific markers for gonad differentiation in H. discus hannai and imply conservation of their functions across invertebrates and vertebrates. Our findings provide new insights into the evolution and genetic structure of the Dmrt family, the TGF-β superfamily and the Sox family in abalone and pave the way for a deeper understanding of sex differentiation in gastropods.

Genome-wide investigation of the DMRT gene family sheds new insight into the regulation of sex differentiation in spotted knifejaw (Oplegnathus punctatus) with fusion chromosomes (Y)

The role of the DMRT family in male sex determination and differentiation is significant, but its regulatory role in spotted knifejaw with Y fusion chromosomes remains unclear. Through genome-wide scanning, transcriptome analysis, qPCR, FISH, and RNA interference (RNAi), we investigated the DMRT family and the dmrt1-based sex regulation network. Seven DMRTs were identified (DMRT1/2 (2a,2b)/6, DMRT4/5, DMRT3), and dmrt gene dispersion among chromosomes is possibly driven by three whole-genome duplications. Transcriptome analysis enriched genes were associated with sex regulation and constructed a network associated with dmrt1. qPCR and FISH results showed the expression dimorphism of sex-related genes in dmrt-related regulatory networks. RNAi experiments indicated a distinct sex regulation mode in spotted knifejaw. Dmrt1 knockdown upregulated male-related genes (sox9a, sox9b, dmrt1, amh, amhr2) and hsd11b2 expression, which is critical for androgen synthesis. Amhr2 is located on the heterozygous chromosome (Y) and is specifically localized in primary spermatocytes, and is extremely upregulated after dmrt1 knockdown which suggested besides the important role of dmrt1 in male differentiation, the amhr2 along with amhr2/amh system, also play important regulatory roles in maintaining high expression of the hsd11b2 and male differentiation. This study aims to further investigate sex regulatory mechanisms in species with fusion chromosomes.

hsd17b1 is a key gene for ovarian differentiation of the Siberian sturgeon

This is the first work using gonads from undifferentiated, genetically-sexed Siberian sturgeon describing expression changes in genes related to steroid synthesis and female and male sex differentiation. One factor identified as relevant for ovarian differentiation was the gene coding for the enzyme Hsd17b1, which converts estrone into estradiol-17β. hsd17b1 was highly activated in female gonads at 2.5 months of age, around the onset of sex differentiation, preceding activation of two other genes involved in estrogen production (cyp19a1 and foxl2). hsd17b1 was also strongly repressed in males. Two known foxl2 paralogs are found in Siberian sturgeon-foxl2 and foxl2l-but only foxl2 appeared to be associated with ovarian differentiation. With regard to the male pathway, neither 11-oxygenated androgens nor classic male genes (amh, dmrt1, sox9, and dhh) were found to be involved in male sex differentiation, leaving open the question of which genes participate in early male gonad development in this ancient fish. Taken together, these results indicate an estrogen-dependence of female sex differentiation and 11-oxygenated androgen-independence of male sex differentiation.