Our findings show a spatio-temporal regulation of the piRNA biogenesis in the follicle cells of Drosophila ovaries, that involves coordinated control of both piRNA precursors and components of the piRNA processing machinery. Both events lead to a reduction of Yb-body assembly in late stages of oogenesis, which likely results in a drop in piRNA production. As oogenesis proceeds, the cytoplasmic delivery steadily decreases concomitantly with the decrease in the protein levels of Armi and Yb, two components of the Yb-bodies.
Early in oogenesis, flamenco transcripts are rapidly transferred to the cytoplasm making their initial nuclear gathering in Dot COM too transient to be visualized. Precursor RNAs first gather in a single nuclear focus, Dot COM, close to the nuclear periphery, and transit through the membrane before being delivered to the cytoplasmic Yb-bodies. Here we show that the nucleo-cytoplasmic traffic of piRNA precursors encoded by the flamenco locus is subjected to a spatio-temporal regulation. In Drosophila ovarian somatic cells, piRNAs arise from long RNA precursors presumably processed within cytoplasmic Yb-bodies. PIWI-interacting RNAs (piRNAs) are the effectors of transposable element silencing in the reproductive apparatus.
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