RNA editing of larch mitochondrial tRNA(His) precursors is a prerequisite for processing

Abstract

Larch mitochondria contain a'native'tRNAHis which is absent from angiosperms. Sequence comparisons of genomic DNA and cDNA obtained from unprocessed primary transcripts of the larch mitochondrial gene trnH encoding this tRNA revealed three nucleotide discrepancies. These three nucleotide alterations, in the acceptor stem, D stem and anticodon stem respectively, are conversions of genomic cytidines to thymidines in the cDNA (uridines in the tRNA) and thus resemble the RNA editing events observed in nearly all plant mitochondrial mRNAs. Two cases of editing affecting mitochondrial tRNAs from angiosperms have already been described, but we present here the first example of such events in a gymnosperm mitochondrial tRNA. All three editing events correct mismatched C x A base pairs which appear when folding the gene sequence into the standard cloverleaf structure, thereby improving the secondary structure of the tRNA. When incubated with a heterologous potato mitochondrial processing extract, only the edited form of the larch mitochondrial tRNAHis precursor was efficiently processed in vitro. These data strongly suggest that editing of larch mitochondrial tRNAHis is a prerequisite for its processing.

RNA editing in Arabidopsis mitochondria effects 441 C to U changes in ORFs

“…Functionally important RNA editing events have been found in several plant mitochondrial tRNAs in potato and Oenothera (18).…”

RNA editing in plant mitochondria, cytoplasmic male sterility and plant breeding

“…While RNA editing is abondant in mitochondrial mRNAs, some C to U events involve organellar tRNAs and some intronic regions (Maréchal-Drouard et al, 1993;Zanlungo et al, 1995). In the case of tRNA, editing is absolutely required to produce this macromolecule from the long precursor (Maréchal-Drouard et al,1996;Marchfelder et al, 1996).…”

“…While RNA editing is abondant in mitochondrial mRNAs, some C to U events involve organellar tRNAs and some intronic regions (Maréchal-Drouard et al, 1993;Zanlungo et al, 1995). In the case of tRNA, editing is absolutely required to produce this macromolecule from the long precursor (Maréchal-Drouard et al,1996;Marchfelder et al, 1996).Incompletely edited transcripts have been detected. Soon after RNA editing discovery it was believed that only completely edited mRNA were translated into proteins as deduced from the analysis of the polysomal mRNA population (Gualberto et al, 1991) and the protein sequencing of the protein ATP9 (Bégu et al, 1991).…”

Post-transcriptional Regulation in Mitochondria of Rice and Wheat at Low Temperatures

“…A major role of this editing is to change the identity of genomically encoded amino acid residues, making the sequences more conserved and/or functional. In addition, RNA editing in plant mitochondria is required in several tRNAs to make them fold correctly by improving the intra-molecular base pairing and thus making them functional 49 . RNA editing in plant mitochondria is an essential step of RNA maturation, without which neither a working respiratory chain nor functional mitochondria can be assembled and maintained in the cell 74 .…”