Precise excision of TTAA-specific lepidopteran transposons piggyBac (IFP2) and tagalong (TFP3) from the baculovirus genome in cell lines from two species of Lepidoptera

Key findings

Fraser et al. demonstrated that piggyBac transposase catalyzes precise excision of transposon elements from baculovirus genomes without leaving sequence alterations at the donor site. Excision events occurred at high frequency in lepidopteran cell lines derived from Trichoplusia ni and Spodoptera frugiperda, restoring exact TTAA target sequences through a cut-and-paste mechanism.

Molecular analysis of excision products revealed perfect reconstitution of TTAA sites at vacated donor loci, with no footprint mutations detected across multiple independent excision events. This precise reversal mechanism distinguishes piggyBac from other transposable elements that typically leave small deletions or insertions upon excision. The transposase-mediated process required functional inverted terminal repeats and occurred bidirectionally.

Transposon excision frequency was enhanced by co-expression of piggyBac transposase, increasing from basal rates to >10% of cells in transient transfection assays. The tagalong (TFP3) element, sharing similar TTAA specificity, exhibited comparable precise excision properties. These findings established piggyBac as a reversible genetic tool with utility for transient and stable genomic modifications in insect systems.