Regulation of early spermatogenesis in the giant prawn Macrobrachium rosenbergii by a GCL homolog

Abstract

The germ cell-less (GCL) gene is crucial for gonad development in various organisms. Early interventions in its expression suggested a regulatory role at the mitotic stages of spermatogenesis, and its early knockout resulted in complete sterility in Drosophila. Genomic and transcriptomic data available for the catadromous giant prawn Macrobrachium rosenbergii enabled the identification of a GCL homolog for this species, which we termed MroGCL (mRNA accession number OQ533056). An open reading frame (ORF) containing 494 amino acids and a typical evolutionarily conserved BTB/POZ domain suggests possible protein-protein interaction functions in keeping with the Drosophila GCL protein. Genomic mapping of MroGCL showed a full length of 120,896 bases. Analysis of the temporal expression of MroGCL showed constant expression in early prawn embryonic and larval stages, but a significant increase 10 days after metamorphosis when crucial sexual differentiation processes occur in prawns. In adult animals, high expression was detected in the gonads compared to the somatic tissues. RNAi-based knock-down experiments showed that both the silenced and control groups reached advanced spermatogenic stages, but that there was a significant decrease in the yield of spermatozoa in about half of the silenced animals. This finding supports our hypothesis that MroGCL is crucial for mitosis during early-stage spermatogenesis. This study thus contributes to the understanding of crustacean gonad development and provides a stepping stone in the development of environmentally valuable sterile crustacean populations.

Keywords: Crustacea; Decapoda; Germ-Cell Less; Gonad development; Macrobrachium rosenbergii; Spermatogenesis.