Kinetics of TMV-RNA synthesis and its correlation with virus accumulation and crystalline viral inclusion formation in tobacco tissue culture

Abstract

Tobacco mosaic virus ribonucleic acid (TMV-RNA) synthesis and the formation of complete virus were studied at 12-hr intervals after inoculation of tobacco ( Nicotiana tabacum L. var. Havana 38) tissue culture. The rate of TMV-RNA synthesis, as measured by the incorporation of uridine- 3H into viral nucleic acid, increased in a nearly linear manner during the first 60 hr after inoculation, reaching a peak during the 48–60-hr period. At this time the rate of viral RNA synthesis was approximately 6 times that of the 12–24-hr period. After the first 60 hr, the rate of viral RNA synthesis declined. The peak rate of accumulation of complete virus occurred during the 48–60-hr period, the period of most rapid viral RNA synthesis. Up to 48 hr after inoculation, crystalline viral inclusions were rarely observed, but at 72 hr large aggregates of crystal-bearing cells were present. After this time no increase in the number of crystal-bearing aggregates was observed. It is likely that plasmodesmata allow for rapid spread of the virus throughout inoculated cell aggregates. The close correlation between viral RNA synthesis, accumulation of complete virus and crystal formation in inoculated tissue culture indicate that the maximum rate of virus synthesis occurred during the first 60 hr. After this time virus synthesis declined and further spread of virus was probably limited to division of virus-infected cells.