Studies of Virus Reproduction

Despite the fact that the introduction of one unit of a virus within a living cell of a susceptible host is followed by the production of millions of virus units, almost nothing is known about the reproductive process. It seemed possible that preparation and isolation of tobacco mosaic virus containing radioactive phosphorus and inoculation of this virus into the diseased plants with the subsequent extensive multiplication of the virus should provide some information concerning the process of virus reproduction. This line of thought induced Stanley (169) to investigate the radioactivity of Turkish tobacco plants inoculated with labeled tobacco virus. Similar investigations were also carried out by Born and associates (25). 

When mosaic-diseased Turkish tobacco plants were fed a nutrient solution containing radioactive phosphorus in the form of disodium phosphate over a period of several weeks, about 30% of the phosphorus taken up by the plants was isolated (by Stanley) in the form of purified tobacco mo,saic virus. The tobacco mosaic virus growing, in contrast to the plant, at a rapid rate is bound to take up a large percentage of the labeled phosphate which reaches the plant. While an organ or a substance grown in a labeled 

The virus containing radioactive phosphorus, to a large extent present as a constituent of the ribonucleic acid molecule, was rubbed into the lower leaves of Turkish tobacco plants. After twelve days the lower inoculated and the upper uninoculated leaves were investigated, with the result shown in Table XLVIII. 

Distribution of in Turkish Tobacco Plants Twelve Davs after Inoculation OF Lower Leaves with 58 Ma. Labeled Tobacco Mosaic Virus (169) 

in Stanley s experiments (as seen in Table XLIX) most of the radioactivity was found associated with nonvirus components in both inoculated and uninoculated portions of the plants, it was impossible to determine whether or not the small amount of radioactive virus found in the uninoculated portions resulted from movement of the inoculated virus. In view of these results it is exceedingly difficult to distinguish between taken up by the plant in the form of virus and that taken up in the form of virus disintegration products. 

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