RNA EDITING IN WHEAT MITOCHONDRIA PROCEEDS BY A DEAMINATION MECHANISM

Most if not all mitochondrial messenger RNAs from seed plants undergo a post-transcriptional modification (RNA editing) involving the conversion of some cytidine residues to uridine, Using a molecular hybridization approach, an in vitro RNA editing system, able to faithfully reproduce the in vivo observed C to U changes of subunit 9 (atp9) of wheat mitochondrial ATP synthase mRNA, has been described [Araya et al, (1992) Proc, Natl, Acad, Sci, USA 89, 1040-1044]. In this work we extend these studies to better understand the biochemical mechanism of this process. RNA editing mas analysed by P1 nuclease digestion of the reaction product followed by thin layer chromatography. Experiments performed with unedited [H-3]RNA labelled on the base and with unedited [P-32]RNA labelled at the alpha-phosphate of cytidine residues, indicate that plant mitochondrial RNA editing operates through a deamination mechanism.