Incorporation of two radioactive amino acids into the nucleic acid fractions in tobacco leaves infected with tobacco mosaic virus

Abstract

The incorporation of H 3-aspartic acid and C 14-glutamic acid into the nucleic acid fractions of tobacco leaves uninfected and infected with TMV was determined through a short incubation period. RNA extracted with phenol from TMV-infected leaves was separated, by means of passage through a methylated albumin column, into 4 S, 17 S, 19 S, 23 S, and 28 S components. The sRNA, the DNA, and the RNA of ribosomes were separated from the mixture in a single run starting with low salt concentration. Concentrations of the sRNA and of the 17 S RNA, as determined by OD 260 measurements, were increased markedly by infection. In this case, H 3 was incorporated mostly into the 17 S RNA, but also into the other RNA to a lesser extent. C 14-glutamic acid was incorporated mainly into the sRNA and the ribosome RNA in healthy leaves. In infected leaves C 14 radioactivity was found mainly in the sRNA and less in the other RNA. In both healthy and diseased leaves incorporation of C 14-glutamic acid into ribosome RNA was markedly suppressed if actinomycin D was taken up simultaneously with C 14-glutamic acid. However, incorporation into sRNA was inhibited less. Blasticidin S had no inhibitory effect on the metabolism of RNA in healthy leaves. When applied to TMV-infected leaves it enhanced incorporation of C 14-glutamic acid into the ribosome RNA, reversing the suppressing effect of TMV infection. On the other hand, the amount of sRNA and incorporation of C 14-glutamic acid into sRNA in TMV-infected leaves remained at high levels even after treatment with blasticidin S.