Structural changes accompanying infection of tobacco protoplasts with two spherical viruses.

Ultrastructural changes occurring in isolated tobacco leaf protoplasts following infection with cowpea chlorotic mottle virus and bromegrass mosaic virus variant 5, have been examined. Only the endoplasmic reticulum/nuclear membrane complex has shown a consistent series of changes in structure and distribution. Both viruses induce proliferation of the endoplasmic reticulum and its modification. The nuclear membrane gives rise to small cytoplasmic vacuoles probably containing nucleic acid by a process of blebbing involving both its inner and outer membrane. This is a prominent feature of CCMV infection. BMV5 infection is particularly characterised by the appearance of local organised arrays of assembled virus particles. The results are discussed in terms of possible nucleocytoplasmic interactions.