Functional characterization of MrOrb in Macrobrachium rosenbergii reveals its crucial role in spermatogenesis

Orb proteins, members of the cytoplasmic polyadenylation element-binding (CPEB) family, play critical roles in germline development in various organisms. Studies in Drosophila melanogaster have indicated that Orb genes are essential for oocyte development, and are crucial for spermatogenesis, including meiotic completion and spermatid differentiation. However, their role in crustacean spermatogenesis remains largely unexplored. This study investigates the function of an Orb homolog in the crustacean freshwater prawn Macrobrachium rosenbergii. We identified and characterized MrOrb, revealing its genomic structure, including 14 exons and two conserved RNA-binding domains, CPEB and RNA recognition motif (RRM). Expression analysis showed high MrOrb expression in mature male and female gonads and during early larval stages. Knockdown of MrOrb in sexually mature males via RNA interference (RNAi) significantly reduced MrOrb transcript levels in the testes resulting in the arrest of advanced spermatogenesis stages with a marked decrease in overall sperm count. These results demonstrate a crucial role for MrOrb in M. rosenbergii spermatogenesis, thereby contributing to our understanding of the functions of Orb in crustacean reproduction and indicating potential applications of the gene in crustacean aquaculture.