Immunolabeling of thin sections of Drosophila tissues for transmission electron microscopy

The main advantage of electron microscopy (EM) for immunolabeling is resolution, but there is also another aspect that is often overlooked. For many investigators, the definitive image of an organelle is the one generated by EM. This is especially true for membranous organelles, with the possible exception of the nucleus and plant vacuoles. For example, references to the Golgi apparatus, smooth and rough endoplasmic reticulum, centriole, kinetochore, or mitochondrion typically bring to mind the images in an electron micrograph. The components of the cytoskeleton also have characteristic structural features that are associated with their EM image. Thus, it can be more effective for investigators to view gold particles superimposed over the image of a microtubule (MT) or mitochondrion using EM than to see bright dots or lines in the light microscope. This is especially true if the immunofluorescence image is of fixed cells. Here, we provide an overview of methods of EM immunolabeling used for localizing specific antigens on thin sections of Drosophila tissues.