CRISPR/Cas9-based homing gene drive for control of the crop pest, Drosophila suzukii

CRISPR/Cas9-based engineered gene-drive systems are currently being explored for the genetic control of human disease-vectors and agriculture pest populations. Genes required for female development, such as doublesex (dsx), have been identified as a potential target of gene-drives for pest population suppression. dsx transcripts undergo sex-specific alternative-splicing to produce male and female Dsx isoforms required for proper sexual and somatic tissue differentiation. Here, we have established split homing drives which target the doublesex (dsx) gene in Drosophila suzukii, an invasive crop pest. The gene drive element, containing dsx single guide RNA and DsRed genes, was introduced into the coding region (CDS) of female-specific exon of dsx, which is essential for function in females but not males. However, in most strains, hemizygous females showed dominant sterility due to male dsx transcript production. With a modified homing drive that included an optimal splice acceptor site to prevent the male splice site use significantly rescued the dominant sterility in females. Super-Mendelian inheritance of the gene-drive cassette (94-99%) were noted with a line that expressed Cas9 with two nuclear localization sequences (NLS) under the D. suzukii nanos promoter. Interestingly, mathematical modeling suggests that these strains could be used for suppression of lab cage populations of D. suzukii with repeated releases at relatively low release ratios (1:4). The potential of the homing strains for genetic suppression remains to be evaluated for caged populations.