Wheat embryo ribonucleates. IX. Generation of N2-dimethylguanylate when bulk wheat embryo tRNA is used as substrate for wheat embryo S-adenosylmethionine-tRNA methyltransferases, in vitro.

Although the cellular ribonucleates in normally growing cells are virtually saturated with respect to their customary complement of methyl substituents, it has often been reported that 'marginal' levels of (homologous) methylation can be detected when ribonucleates and enzymes from the same source material are incubated, together with S-adenosylmethionine, in vitro. Experiments were designed to acquire new insights that might be useful for circumscribing the number of possible interpretations that could be advanced to account for the introduction of 'supernumerary' methyl groups during (homologous) methylation of wheat RNA by wheat enzymes, in vitro. For a large fraction of the supernumerary methyl groups that can be introduced into wheat RNA, in vitro, it was not possible to adduce convincing evidence in support of the view that any appreciable quantity of methyl groups is ever introduced at these same sites, in vivo. The possibility that these supernumerary methyl groups might have transient existence, in vivo, and the potential physiological significance of any such occurrence are dealt with as part of a more general discussion of the experimental findings.