Expanding the CRISPR base editing toolbox in Drosophila melanogaster.

CRISPR base editors can introduce point mutations into DNA precisely, and cytosine base editors (CBEs) catalyze C to T transitions. While CBEs have been thoroughly explored in cell culture and organisms such as mice, little is known about DNA base editing in insects. In this study, we evaluated germline editing rates of three different CBEs expressed under actin (ubiquitous) or nanos (germline) promoters utilizing Drosophila melanogaster. The original Rattus norvegicus-derived cytosine deaminase APOBEC1 (rAPO-1) displayed high base editing rates (~99%) with undetectable indel formation. Additionally, we show that base editors can be used for generating male sterility and female lethality. Overall, this study highlights the importance of promoter choice and sex-specific transmission for efficient base editing in flies while providing new insights for future genetic biocontrol designs in insects.