Théron et al. show that Piwi decrease in Pilp is due to the Argonaute protein Aubergine (Aub). Consequently, the transcriptional repression exerted on transposable elements (TEs) is weakened. The resulting mRNAs encoded by active TEs are wired into the ping-pong cycle to give an increased amount of piRNAs that can ultimately target TEs for silencing throughout the downstream developmental stages.
In mutant flies when Aub is specifically knocked down in the Pilp, Piwi expression is recovered, transcriptional repression of TEs increases, homologous piRNA amplification decreases. This leads to flies which lay eggs that do not hatch.
Strikingly, when Aub is depleted, the Pilp has the capacity to sense changes in TE control and to drive adaptation in ageing flies