Time course of TMV 30K protein accumulation in intact leaves.

The kinetics of accumulation of the 30K and coat proteins of tobacco mosaic virus (TMV) which are expressed via subgenomic mRNAs were determined in near-synchronously infected cells of intact tobacco leaves. The 30K protein accumulated to maximal levels during the early stages of the infection as previously reported in tobacco protoplasts. However, in intact leaves, 30K protein accumulated for longer periods and attained higher concentrations than in protoplasts, remaining detectable in all later time samples. Detection of the coat protein, and also the 126K and 183K proteins, began at approximately the same time as the 30K protein (9-12 hr after initiation of replication), but their accumulation continued throughout the 72-hr sampling period. Most of the 30K protein accumulated before 24 hr, whereas most of the coat protein accumulated after 24 hr. This confirms that these two genes are regulated differently, both temporally and quantitatively.