A Testis-Specific DMRT1 (Double Sex and Mab-3-Related Transcription Factor 1) Plays a Role in Spermatogenesis and Gonadal Development in the Hermaphrodite Boring Giant Clam Tridacna crocea.

ABSTRACT

The testis-specific double sex and mab-3-related transcription factor 1 (DMRT1) has long been recognized as a crucial player in sex determination across vertebrates, and its essential role in gonadal development and the regulation of spermatogenesis is well established. Here, we report the cloning of the key spermatogenesis-related DMRT1 cDNA, named Tc-DMRT1, from the gonads of Tridacna crocea (T. crocea), with a molecular weight of 41.93 kDa and an isoelectric point of 7.83 (pI). Our hypothesis is that DMRT1 machinery governs spermatogenesis and regulates gonadogenesis. RNAi-mediated Tc-DMRT1 knockdown revealed its critical role in hindering spermatogenesis and reducing expression levels in boring giant clams. A histological analysis showed structural changes, with normal sperm cell counts in the control group (ds-EGFP) but significantly lower concentrations of sperm cells in the experimental group (ds-DMRT1). DMRT1 transcripts during embryogenesis exhibited a significantly high expression pattern (p < 0.05) during the early zygote stage, and whole-embryo in-situ hybridization confirmed its expression pattern throughout embryogenesis. A qRT-PCR analysis of various reproductive stages revealed an abundant expression of Tc-DMRT1 in the gonads during the male reproductive stage. In-situ hybridization showed tissue-specific expression of DMRT1, with a positive signal detected in male-stage gonadal tissues comprising sperm cells, while no signal was detected in other stages. Our study findings provide an initial understanding of the DMRT1 molecular machinery controlling spermatogenesis and its specificity in male-stage gonads of the key bivalve species, Tridacna crocea, and suggest that DMRT1 predominantly functions as a key regulator of spermatogenesis in giant clams.