Improved <em>piggyBac</em> Transformation with Capped Transposase mRNA in Pest Insects

Creating transgenic insects is a key technology in insect genetics and molecular biology. A widely used instrument in insect transgenesis is the piggyBac transposase, resulting in essentially ran-dom genomic integrations. In contrast, site-specific recombinases allow the targeted integration of the transgene construct into a specific genomic target site. Both strategies, however, often face limitations due to low transgenesis rates. We aimed to enhance transgenesis rates by utilizing a capped mRNA as a source of transposase or recombinase instead of a helper plasmid. A system-atic comparison of transgenesis rates in Aedes mosquitoes, as models for hard to transform in-sects, showed that suppling piggyBac transposase as mRNA increased the average transfor-mation efficiency in Aedes aegypti from less than 5% with the plasmid source to about 50% with mRNA. Similar high transformation activity was observed in Ae. albopictus with pBac mRNA. No efficiency differences between plasmid and mRNA were observed in recombination experi-ments. Furthermore, a codon-optimized version of piggyBac transposase delivered as plasmid didn’t improve the transformation efficiency in Ae. aegypti or the agricultural pest D. suzukii. We believe that the use of mRNA has strong potential for enhancing pBac transformation efficiencies in other mosquitoes and important agricultural pests such as tephritids.