Recombination technologies for enhanced transgene stability in bioengineered insects

Transposon-based vectors currently provide the most suitable gene transfer systems for insect germ-line transformation and are used for molecular improvement of the Sterile Insect Technique. However, the long time stability of genome-integrated transposon constructs depends on the absence of transposase activity that could remobilize the transposon-embedded transgenes. To achieve transgene stability transposon vectors are usually non-autonomous, lacking a functional transposase gene, and chosen so that endogenous or related transposon activities are not present in the host. Nevertheless, the non-autonomous transposon-embedded transgenes could become unstable by the unintended presence of a mobilizing transposase that may have been undetected or subsequently entered the host species by horizontal gene transfer. Since the field release of transgenic insects will present environmental concerns relating to large populations and high mobility, it will be important to ensure that transgene constructs are stably integrated for maintaining strain integrity and eliminating the possibility for unintentional transfer into the genome of another organism. Here we review efficient methods to delete or rearrange terminal repeat sequences of transposons necessary for their mobility, subsequent to their initial genomic integration. These procedures should prevent transposase-mediated remobilization of the transgenes, ensuring their genomic stability.