Evolution of piRNA-guided defense against transposable elements.

Transposable elements (TEs) shape every aspect of genome biology, influencing genome stability, size, and organismal fitness. Following the 2007 discovery of the piRNA defense system, researchers have made numerous findings about organisms' defenses against these genomic invaders. TEs are suppressed by a 'genomic immune system', where TE insertions within specialized regions called PIWI-interacting RNA (piRNA) clusters produce small RNAs responsible for their suppression.

The impact of insertion bias into piRNA clusters on the invasion of transposable elements.

In our current understanding of transposable element (TE) invasions TEs move freely until they accidentally insert into a piRNA cluster. They are then silenced by the production of piRNA cognate to the TE. Under this model, one would expect that TEs might evolve to avoid piRNA clusters.