INDUCIBLE CELL ABLATION IN DROSOPHILA BY COLD-SENSITIVE RICIN-A CHAIN

We have developed a system for temperature-inducible killing of specific cells in the fruitfly Drosophila melanogaster. The system overcomes many of the limitations of existing cell ablation methods and is in principle applicable to any non-homeothermic eukaryote. Temperature-sensitive and cold-sensitive mutations in the ricin toxin A chain (RTA) of castor bean were generated in yeast. One cold-sensitive mutation, RAcs2, produced temperature-dependent ablation of eye cells in Drosophila when expressed under control of the eye-specific sev enhancer. At 29-degrees-C, cell death was observed within 7 hours in the developing eye and no obvious toxic effects were observed elsewhere; at 18-degrees-C, extremely low toxicity was observed. DNA sequencing of RAcs2 revealed a single amino acid substitution in the RTA active site cleft.