Spatiotemporal control of cell ablation using Ronidazole with Nitroreductase in Drosophila.

The ability to induce cell death in a controlled stereotypic manner has led to the discovery of evolutionary conserved molecules and signaling pathways necessary for tissue growth, repair, and regeneration. Here we report the development of a new method to genetically induce cell death in a controlled stereotypic manner in Drosophila. This method has advantages over other current methods and relies on expression of the E. coli enzyme Nitroreductase (NTR) with exogenous application of the nitroimidazole prodrug, Ronidazole. NTR expression is controlled spatially using the GAL4/UAS system while temporal control of cell death is achieved through timed feeding of Ronidazole supplied in the diet. In cells expressing NTR, Ronidazole is converted to a toxic substance inducing DNA damage and cell death. Caspase cell death is achieved in a range of NTR-expressing cell types with Ronidazole feeding, including epithelial, neurons, and glia. Removing Ronidazole from the diet restores cell death to normal unperturbed levels. Unlike other genetic ablation methods, temporal control is achieved through feeding not temperature, circumventing developmental complications associated with temperature changes. Ronidazole-NTR also requires only two transgenes, a GAL4 driver and UAS-NTR, which is generated as a GFP-NTR fusion allowing for easy setup of large-scale screening of UAS-RNAi lines. Altogether, Ronidazole-NTR provides a new streamlined method for inducing cell death in Drosophila with temperature-independent ON/OFF control.