Somatic Cells Induce Male-Biased Translational Activity in the Germline of Drosophila melanogaster

The germline of Drosophila melanogaster originates from primordial germ cells (PGCs). The sex of PGCs is determined during mid-to-late embryogenesis, and PGCs subsequently begin to differentiate into eggs or sperm. Several genes involved in the sex determination of PGCs have been identified, but the mechanisms underlying sex differentiation remain unclear. To clarify these mechanisms, identifying the sex-specific differences in PGCs and elucidating how these differences arise is necessary. We previously found that translational activity in PGCs was higher in males than in females at the late embryonic stage. However, it remains unclear when male-biased translational activity is initiated and the mechanisms that induce this bias are unknown. Here, we show that male-biased translational activity in PGCs is observed from the stage when the JAK/STAT pathway, a known masculinizing pathway in PGCs, is activated. Furthermore, this male-biased translational activity depended on the sex of the surrounding somatic cells. Moreover, the JAK/STAT pathway did not affect male-biased translational activity in embryonic PGCs, although it did affect larval germline cells. These findings suggest that embryonic PGCs respond to previously unidentified signals, rather than to the JAK/STAT pathway, from somatic cells, which in turn induces male-biased translational activity.