Preprint: piRNA pathway loss triggers episodic transposition bursts across generations in Drosophila

A preprint deposited on bioRxiv reports that loss of the piRNA pathway in Drosophila does not produce steady continuous transposon mobilisation but instead drives episodic bursts of transposition events, with marked variation between individual flies and across generations.

The piRNA (PIWI-interacting RNA) pathway is the primary mechanism by which metazoan germlines suppress transposable elements. Disruption of this pathway is known to cause elevated transposon transcript levels, but whether increased expression translates reliably into new genomic insertions — and at what frequency — had remained difficult to quantify.

The research team developed a single-fly Nanopore long-read DNA sequencing framework to track the accumulation of new transposon copies at single-insertion resolution across successive generations of male Drosophila lacking HP1D/Rhino, a core piRNA biogenesis factor. Their data showed that several distinct transposon families mobilise upon piRNA loss, but do so in episodic bursts rather than at a constant rate, and that the identity and frequency of mobilising elements varied between lineages.

The findings have implications for understanding germline genome instability, the evolutionary dynamics of transposable elements, and the functional consequences of piRNA pathway disruption. The preprint has not yet been peer-reviewed.