Fig. 2: The influence of membrane reinforcement and viral RNA in shaping the replication organelles.

A Slices through tomograms of empty and filled ROs in LGTV-infected cells. Blue and red arrows indicate the thickness of the ER and RO membranes, respectively. Scale bar, 50 nm. B, C Membrane thickness estimation by dual Gaussian fitting to radial density plots through a representative ER membrane (B) and RO membrane (C). Solid red and blue lines, experimental membrane density profile; dashed lines, fitted composite (black) and dual Gaussian (purple/green); shaded area, estimated thickness. D ER and ROs membranes from a representative tomogram of an LGTV-infected cell, color coded by apparent membrane thickness. ER membrane is partially transparent. E Apparent membrane thickness quantification in four tomograms of LGTV-infected cells, comparing individual ROs (N = 133) and the surrounding ER regions (N = 103). Red lines, median. Statistical significance by unpaired two-tailed Student’s t test, p = 8.15 × 10⁻⁴⁷. F Relationship between radius of curvature and apparent membrane thickness for individual ROs (N = 132 from six tomograms). G Model of the mechanisms determining viral RO size. Two RO states exist in infected cells: empty ROs with a baseline size set independent of luminal RNA, and filled ROs, whose larger size is due to intraluminal pressure from ~2000 to 10,000 bp dsRNA.