Electron Microscopy of Tobacco Mosaic Virus Infection in Tobacco Mesophyll Protoplasts

Abstract

Isolated protoplasts from tobacco mesophyll tissues were inoculated with tobacco mosaic virus (TMV), and the process of TMV infection in the protoplasts was observed by electron microscope at various times after inoculation. TMV particles attached to the cell membrane with their particle ends immediately after inoculation. And an average of 10-10² virus particles per protoplast was taken up by phagocytosis within 10 minutes after inoculation. By 30 minutes, 46% of virions which had been taken up into the protoplast disappeared from the phagosomes and this value rose to 72% after 6 hours. Virus particles were first seen in the ground cytoplasm after 9-12 hours as individuals or small aggregates, and after 48 hours, a level of 10⁶ virus particles per protoplast appeared as semi-crystalline aggregates in the ground cytoplasm. Specific morphological changes of nuclei, chloroplasts and mitochondria resulting from the virus infection were not observed and no virus particles were seen in these subcellular organelles till 48 hours after inoculation.