Does tobacco mosaic virus RNA contain cytokinins?

Tobacco mosaic virus was previously reported to contain between 5 and 17 modified nucleosides with cytokinin activity per RNA molecule. Using a new and highly sensitive method for gas chromatography of permethylated cytokinins, we were unable to detect cytokinins in enzymic or alkaline digests of TMV RNA. The method was sensitive enough to assay 1 cytokinin nucleoside per 10 TMV RNA molecules. Soybean callus bioassay also failed to detect activity in TMV RNA hydrolysates which corresponded to any of the cytokinin nucleosides known to occur in RNA. We therefore suggest that TMV RNA does not contain cytokinin nucleosides.