CRISPR-Engineered Intragenic Genetic Sexing Strain in Medflies

In this study, we generated a method to engineer intragenic genetic sexing strains (IGSS) in insects. We use CRISPR/Cas9-mediated homology-directed repair to seamlessly translocate a sex-specific alternatively spliced intron into a dominant phenotypic gene generating a genetically stable strain that enables visual sex-sorting by eye. To achieve this, we use C. capitata as our model and relied on the sex-specifically spliced intron of the endogenous transformer gene, which was inserted into the pupal colouration-implicated white pupae gene. This minimal modification resulted in the generation of a homozygous strain that was phenotypically stable where all female pupae are brown while male pupae are white with overall good fitness. By minimally editing the genome, our CGSS approach can be applied to related global fruit fly pests, which may aid more efficient and economically suitable agricultural pest control.