piRNA loss unleashes episodic transposition bursts.

In the Drosophila male germline, piRNA loss (via HP1D/Rhino disruption) mobilizes multiple transposon families after 10–45 generations, with copia producing dozens of new insertions.

• Why it matters: It was unclear whether piRNA-driven increases in transposon expression translate into actual mobilization, and how frequently and when transposons move after piRNA pathway disruption.
• What they did: The authors tracked transposon copy accumulation across generations on a single nonrecombining haploid genome using single-fly Nanopore DNA sequencing, and validated/dated copia insertions from genomic DNA collected each generation.
• The result: copia mobilization occurred in episodic bursts that deviated strongly from a Poisson process, and mdg3 and invader3 also mobilized episodically, directly showing tight piRNA suppression of germline transposition.