3D gold in situ labelling in the EM.

We have developed a novel pre-embedding in situ hybridization labelling method for electron microscopy which has given much greater sensitivity and higher labelling levels than have been achieved previously, together with good ultrastructural preservation. Vibratome sections of plant tissue were labelled throughout their thickness with 1 nm gold antibodies and then silver enhanced, embedded in resin and sectioned for electron microscopy. Because the labelling extends throughout the depth of the specimen, this method permits the study of the 3D arrangement of the labelling at the electron microscope level by either stereo-pair recording, tomographic reconstruction or 3D reconstruction from serial sections. In this paper we describe the application of this method to study the organization of rDNA in pea root tissue.