SARS-Coronavirus Replication Is Supported by a Reticulovesicular Network of Modified Endoplasmic Reticulum
Figure 3
Electron Tomography Revealing the Interconnected Nature of SARS-CoV–Induced DMVs
The series of images at the top illustrates how a 3-D surface-rendered model was derived by applying ET on a semi-thick section of a SARS-CoV–infected Vero E6 cell cryofixed at 7 h p.i.
(A) A 0°-tilt transmission EM image of a 200-nm-thick resin-embedded section showing ER and a cluster of DMVs. The 10-nm gold particles were layered on top of the sections and were used as fiducial markers during subsequent image alignment. Scale bar represents 100 nm.
(B) Using the IMOD software package (see Materials and Methods), tomograms were computed from dual-axis tilt series of the 200-nm-thick section shown in (A) (see also Videos S1 and S2). The tomographic slice shown here has a thickness of 1.2 nm.
(C) The improved image from (B) following anisotropic diffusion filtering. The optimized signal-to-noise ratio facilitates thresholding and DMV surface rendering. See Figure S2 for a stereo image of this model.
(D) Final 3-D surface-rendered model showing interconnected DMVs (outer membrane, gold; inner membrane, silver) and their connection to an ER stack (depicted in bronze). Arrows (I, II, and III) point to three clearly visible outer membrane continuities, with insets highlighting these connections in corresponding tomographic slices. Scale bar represents 50 nm.