Fig. 7: Virions appear to bud into VCs coated in S glycoprotein that are transferred from the limiting membrane.

a, b Virions (red arrowheads) appear to be budding into a VC which has a S glycoprotein coat. c–f Slices from tomograms indicating budding at the limiting membrane of a VC. Microtubules were seen running into budding virions (c) or nearby (d) as indicated by the yellow arrowheads. The boxed region in (e) is shown at higher magnification in (f) that includes two different slices from a tomogram. The nucleocapsid protein appeared to be concentrated at the membrane of the budding virions (false coloured blue in (f) and green arrowhead in (c, d)). The boxed region in (g) is shown at higher magnification (h) of a VC that contains a virus (red arrowhead) and has S glycoprotein (blue arrowheads) on the limiting membrane facing the lumen. i, j Slices from tomograms generated of VCs showing S glycoprotein on the limiting membrane in more detail. Viral particles were within the VCs as well as surrounded by membranes in structures close by. Scale bars (a, b, e, g, h) 200 nm and (c, d, f, i, j) 100 nm.