Nonradioactive In Situ Hybridization Methods for Drosophila Embryos Detecting Signals by Immunogold‐Silver or Immunoperoxidase Method for Electron Microscopy

We present details of in situ hybridization methods for electron microscopy applicable for Drosophila embryos. Improvements upon the foregoing methods were made at 1) hybridization and visualization of signals were carried out with whole embryos that were then processed for electron microscopy, and 2) digoxigenin-labeled probes were detected by the immunogold silver enhancement method or by the immunoperoxidase method. Using these methods. we demonstrated the localization of fushi tarazu transcripts in the apical region of blastodermal cells. We also showed that mitochondrial large ribosomal RNA is associated with polar granules in pole plasm of cleavage embryos. These methods will make a useful tool to determine the precise subcellular distribution of specific transcripts in Drosophila embryos.