Incorporation of Cytokinin N6-Benzyladenine into Tobacco Callus Transfer Ribonucleic Acid and Ribosomal Ribonucleic Acid Preparations 1

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The incorporation of the cytokinin N6-benzyladenine into tobacco (Nicotiana tabacum) callus tRNA and rRNA preparations isolated from tissue grown on medium containing either N6-benzyladenine-8-14C or N6-benzyladenine-8-14C: benzene-3H(G) has been examined. N6-benzyladenine was incorporated into both the tRNA and rRNA preparations as the intact base. Over 90% of the radioactive N6-benzyladenosine recovered from the RNA preparations was associated with the rRNA. Purification of the crude rRNA by either MAK chromatography or Sephadex G-200 gel filtration had no effect on the N6-benzyladenosine content of the RNA preparation. The distribution of N6-benzyladenosine moieties in tobacco callus tRNA fractionated by BD-cellulose chromatography did not correspond to the distribution of ribosylzeatin activity. N6-benzyladenosine was released from the rRNA preparation by treatment with venom phosphodiesterase and phosphatase, ribonuclease T2 and phosphatase, or ribonuclease T2 and a 3′-nucleotidase. N6-benzyladenosine was not released from the RNA preparation by treatment with either ribonuclease T2 or phosphatase alone or by successive treatment with ribonuclease T2 and a 5′-nucleotidase. Brief treatment of the rRNA preparation with ribonuclease T1 and pancreatic ribonuclease converted the N6-benzyladenosine moieties into an ethyl alcohol soluble form. On the basis of these and earlier results, the N6-benzyladenosine recovered from the tobacco callus RNA preparations appears to be present as a constituent of RNA and not as a nonpolynucleotide contaminant.

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