Viral RNA synthesis is renewed in protoplasts isolated from TMV-infected Xanthi tobacco leaves in an advanced stage of virus infection.

TMV-RNA synthesis was shown to be renewed in protoplasts isolated from TMV-infected Xanthi tobacco leaves in which virus synthesis has already slowed down or stopped. This was demonstrated by the use of isotope techniques in three different disease situations: (a) in primarily infected leaves 8-10 days after infection, (b) in secondarily infected leaves 2 mo after infection, and (c) in stable green areas ("true dark green islands" according to the terminology of Atkinson and Matthews, 1970) of leaves exhibiting mosaic symptoms.