Three-dimensional quantitative imaging of Tobacco mosaic virus and Zucchini yellow mosaic virus induced ultrastructural changes

Two-dimensional ultrastructural changes of Tobacco mosaic virus (TMV) and Zucchini yellow mosaic virus (ZYMV) in tobacco and pumpkin plants, respectively, are well studied. To provide 3D data, representative control and infected cells were reconstructed using serial sectioning and transmission electron microscopy. Quantitative data of 3D ultrastructural changes were then extracted from the cytosol and organelles by image analysis. While TMV induced the accumulation of an average of 40 virus inclusion bodies in the cytosol, which covered about 13% of the cell volume, ZYMV caused the accumulation of an average of 1752 cylindrical inclusions in the cytosol, which covered about 2.7% of the total volume of the cell. TMV infection significantly decreased the number and size of mitochondria (- 49 and - 20%) and peroxisomes (- 62 and - 28%) of the reconstructed cell. The reconstructed ZYMV-infected cell contained more (105%) and larger (109%) mitochondria when compared to the control cell. While the reconstructed TMV-infected cell contained larger (20%) and the ZYMV-infected smaller (19%) chloroplasts, both contained less chloroplasts (- 40% for TMV and - 23% for ZYMV). In chloroplasts, the volume of starch and plastoglobules increased (664% and 150% for TMV and 1324% and 1300% for ZYMV) when compared to the control. The latter was correlated with a decrease in the volume of thylakoids in the reconstructed ZYMV-infected cell (- 31%) indicating that degradation products from thylakoids are transported and stored in plastoglobules. Summing up, the data collected in this study give a comprehensive overview of 3D changes induced by TMV and ZYMV in plants.