Temperature-dependent sex-reversal by a transformer-2 gene-edited mutation in the spotted wing drosophila, Drosophila suzukii

Authors: LI, JIANWEI - University Of Florida; Handler, Alfred - Al

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2017
Publication Date: 9/28/2017
Citation: Li, J., Handler, A.M. 2017. Temperature-dependent sex-reversal by a transformer-2 gene-edited mutation in the spotted wing drosophila, Drosophila suzukii. Scientific Reports. 7:12363. https://doi.org/10.1038/s41598-017-12405-4.
DOI: https://doi.org/10.1038/s41598-017-12405-4

Interpretive Summary: The spotted-wing drosophila, Drosophila suzukii, is an emerging agricultural insect pest in the continental U.S. for a variety of stone fruits. To provide an additional tool for the Integrated Pest Management program (IPM), genetically modified strains to improve and expand upon existing biocontrol programs such as the sterile insect technique (SIT) have been constructed. One strategy for an efficient means of producing strains with all sterile-male progeny is to create mutations in specific sex-determination genes that are temperature-dependent and that result in sterile all-male development at elevated temperatures. Scientists at USDA, Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, have used the CRISPR/Cas9 gene-editing techniques in the spotted-wing drosophila that produced predominantly sterile males at elevated temperatures. This study confirmed the creation of a temperature-dependent function for a gene-edited mutation in a critical sex-determination gene and provided proof of principle that such mutations can be used to create sterile male-only strains for SIT programs targeting the spotted-wing drosophila or other related insect pests.

Technical Abstract: Female to male sex reversal was achieved in an emerging agricultural insect pest, Drosophila suzukii, by creating a temperature-sensitive point mutation in the sex-determination gene, transformer-2 (tra-2) using CRISPR/Cas9 (clustered regularly interspaced palindromic repeats/ CRISPR-associated) homology-directed repair gene-editing. Ds-tra-2ts2 mutants developed as normal fertile XX and XY adults at permissive temperatures below 20°C, but at higher restrictive temperatures (26 to 29°C) chromosomal XX females developed as sterile intersexuals with a predominant male phenotype, while XY males developed with normal morphology, but were sterile. The temperature-dependent function of the Ds-TRA-2ts2 protein was also evident by the up- and down-regulation of female-specific Ds-Yolk protein 1 (Ds-Yp1) gene expression by temperature shifts during adulthood. This study confirmed the temperature-dependent function of a gene-edited mutation and provided proof of principle for the more general creation of conditional mutations for functional genomic analysis in insects, and other organisms. Furthermore, it provides a temperature-dependent system for creating sterile male populations useful for enhancing the efficacy of biologically-based programs, such as the sterile insect technique (SIT), to control D. suzukii and other insect pest species of agricultural and medical importance.