The transformer gene controls sexual development in Drosophila suzukii

The genetic network of sex determination in the model organism Drosophila melanogaster was investigated in great detail. Such knowledge not only advances our understanding of the evolution and regulation of sexual dimorphism in insects, but also serves as a basis for developing genetic control strategies for pest species. In this study, we isolated the sex determination gene transformer (Dstra) from a global fruit pest, the spotted-wing Drosophila (Drosophila suzukii), and characterized its gene organization. By comparing the deduced protein sequence of Dstra with its orthologs from 22 species, we found that tra genes from Dipteran species are divergent. Our research demonstrated that Dstra undergoes sex-specific splicing, and we validated its developmental expression profile. We engineered a piggyBac-based transformation vector expressing the complete Dstra coding sequence under the control of the Tetracycline-Off system. Through germ-line transformation, we generated 4 independent transgenic lines, producing pseudo-females from chromosomal males in the absence of tetracycline. This observation indicated ectopic expression of Dstra, confirmed by the detection of female Dstra transcripts in transgenic males. The pseudo-females exhibited altered wing patterns, feminized abdomen, abnormal reproductive organs, and disrupted sexual behavior. Ectopic expression of Dstra affected the sex-specific splicing pattern of the downstream gene fruitless, but not doublesex. In conclusion, our study provides comprehensive genetic, morphological, and behavioral evidence that Dstra controls sexual development in D. suzukii. We discuss the potential applications of this research for genetic control strategies targeting Dstra or using its gene elements.