Comparison of the early stages of infection by tobacco mosaic virus and its nucleic acid

SUMMARY: The early events in the infection of tobacco and Nicotiana glutinosa by tobacco mosaic virus occur sooner when the inoculum is the nucleic acid of the virus than the whole virus. In plants a t 28 " newly formed virus becomes detectable between 6 and 8 hr. after inoculation with the nucleic acid and after 8-10 hr. with whole virus. Although the latent period is lengthened by lowering temperature, the difference between the lengths of the latent periods given by the two inocula is little changed. Infective centres initiated by nucleic acid also become resistant to hot-water treatment (a 30 sec. dip in water at BOO) about 2 4 hr. sooner than do those initiated by whole virus. Exposure of inoculated plants to 37 ' decreases the number of lesions produced by the nucleic acid much more than by whole virus; resistance to this treatment develops from 30 to 120 min. after inoculation with the nucleic acid, depending on the temperature a t which the plants are kept. Siegel, Ginoza & Wildman (1957) compared the time course of infections with tobacco mosaic virus (TMV) and with its nucleic acid (NA) by ultraviole