LOCALIZATION OF TOBACCO MOSAIC VIRUS PROTEIN IN TOBACCO LEAF CELLS DURING EARLY STAGES OF INFECTION

Antibodies specific to tobacco mosaic virus were labeled with 125I and used to localize the site of protein synthesis during the early stages of virus infection by means of radioautography. The development of the methods used is presented in some detail. Counts of silver grains over the nucleus, cytoplasm, and chloroplasts of cells from inoculated leaves were compared with similar counts made on healthy leaves. As early as 5-6 hours after inoculation significantly more label was present in both the nucleus and the cytoplasm of cells of inoculated tobacco leaves. The amount of label over the nucleus gradually increased until it was approximately 4 times the control at 48 hours after inoculation. On the other hand, the amount of label over the cytoplasm began a very rapid increase at about 12 hours after inoculation, and by 48 hours it was estimated to be approximately 10 times as heavily labeled as the healthy controls. No association of label was found with the chloroplasts or with specific areas of the cytoplasm. © 1969.