Using the vital dye acridine orange to detect dying cells in Drosophila.

Acridine orange is a cell-permeable fluorescent dye that binds to nucleic acids, resulting in an altered spectral emission. Acridine orange staining has been shown to be highly selective for apoptotic cells in Drosophila; however, the precise mechanism underlying this effect is not known. Advantages of acridine orange staining include the speed and ease of the staining. But there are disadvantages: It should be performed on unfixed tissue that therefore must be examined immediately, and multiple labeling cannot be performed. Slightly different protocols for the uptake of acridine orange are required for different developmental stages. Here, we present protocols for use of acridine orange to detect apoptosis in Drosophila embryos and in larval tissue. Slight modifications might be required for other Drosophila tissues.