[The effect of auxin and cytokinin on RNA-synthesis in sterile tobacco tissue].

The influence of auxin and cytokinin on RNA synthesis was investigated by measuring (32)PO4 (3-)-incorporation into polysomes and polysomal RNAs of tissue grown from pith of Nicotiana tabacum L. The test tissue grown on a medium containing a minimum of auxin and cytokinin was further starved for a period of 12 h prior to the experiments. The tests were carried out under the following different conditions: 1. without any growth substances, 2. with auxin only, 3. with kinetin only, and 4. with auxin and kinetin. The tissues were incubated in small volumes of the test medium for 1-8 h on a shaker. The last hour of incubation was carried out in the presence of (32)PO4 (3-).Differences in (32)PO4 (3-) uptake into the polysomes were observed as early as after 3 h of incubation. Kinetin alone shows no effect at all, auxin causes increased synthesis of polysomal RNAs, and kinetin administered together with auxin augments the increase of (32)PO4 (3-) uptake into polysomes and polysomal RNAs observed with auxin alone. These results and those of Seth and Wareing [J. exp. Bot. 18, 65-77 (1967)], Bhattacharyya and Roy [Biochem. biophys. Res. Commun. 35, 606-610 (1969)], and Venis [Proc. nat. Acad. Sci. (Wash.) 68, 1824-1827 (1971)] lead to the following working hypothesis: while auxins exert their influence on the RNA transcription, cytokinins may possibly influence the translation process.