A method to stain nuclei of Drosophila for confocal microscopy

We report a method of staining nurse cell and follicle cell nuclei in Drosophila ovaries and nuclei in Drosophila embryos with the fluorescent dye propidium iodide. This technique was used to replace more commonly used 4', 6-diamidino-2-phenylindole (DAPI) and Hoechst staining as a method of visualizing nuclear material in Drosophila. Propidium iodide has its maximum excitation at about 530 nm and maximum fluorescence at 615 nm, and therefore it can be used as a fluorescent marker with confocal microscopes that do not have a UV excitation source. Another advantage of the described method is the convenience of simultaneous use of fluorescein as a second fluorophore in multicolor fluorescence. We show that the nuclear material in Drosophila ovaries and early embryos can be visualized with propidium iodide using both confocal and conventional fluorescence microscopy. We also test the combination of two fluorophores-propidium iodide for nuclear staining and fluorescein-labeled phalloidin for membrane-bound actin--in the same tissue.