Stein, A., Virus Laboratory, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Loebenstein, G., Virus Laboratory, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Spiegel, S., Virus Laboratory, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel

Injection of ethylene maleic anhydride copolymer (EMA-31) into the leaves of Samsun NN tobacco induced resistance to tobacco mosaic virus (TMV), decreasing both lesion number and lesion size. Interference was not due to lack of attachment of virus particles during the first stage of infection, nor to inhibition of uncoating of viriom. Interference was completely suppressed in plants kept before and after injection of the polyanion at 40°C, while actinomycin D given together with polyanion application resulted in partial suppression. Incorporation of uracil increased significantly in induced-resistant compared with control tissue, but not in plants kept at 40°C, nor in polyanion-treated Samson tobacco, a systemic host for TMV. This indicates that during the induction period the cellular transcription mechanism must operate. Monosomes from induced-resistant tissue of Samsun NN were more stable to dissociation in high-KC1 media than monosomes from control or polyanion-treated Samsun plants, indicating that active protein synthesis occurs. In the antiviral state, good correlations were observed between resistance and a specific ribosomal fraction (R2), recovered by a two-step procedure. This fraction was considerably increased during the development of resistance. Actinomycin D and high temperatures, which suppressed development of interference, also abolished differences between R2 from EMA-31-treated tissue and from control tissue. No differences were observed between EMA-31-treated and control tissues from Samsun, or in Samsun NN′ injected with polyanions that did not induce interference. It seems that in vitro concentrated preparations of R2 form an unstable aggregate. It may be that "sticky" ribosomes are participating in maintaining the resistant state. © 1979.