Editing corrects mispairing intheacceptor stemofbean andpotato mitochondrial phenylalanine transfer RNAs

Editing isa general eventinplantmitochondrial messenger RNAs,buthasneverbeendetected ina plantmitochondrial transfer RNA (tRNA).We demonstrate heretheoccurence ofatRNAediting eventinhigher plant mitochondria: inbothbeanand potato, theCencoded atposition 4inthemitochondrial tRNAPhO(GAA) geneisconverted into aUinthemature tRNA.Thisnucleotide change corrects themismatched C4-A89 base-pair whichappears whenfolding thegene sequenceintothecloverleaf structure anditis consistent withthefactthatC toU transitions constitute thecommonediting events affecting plant mitochondrial messenger RNAs.ThetRNAPhe(GAA) geneislocated upstreamofthesingle copy tRNAPrm(UGG) geneinboththepotato andthebean mitochondrial DNAs.Thesequences ofpotato and beantRNAPro(UGG) genesarecolinear withthe sequenceofthematurebeanmitochondrial tRNAPrm(UGG), demonstrating thatthistRNAisnot edited. A single copytRNATer(GCU) genewasfound upstreamofthetRNAPhe geneinthepotato mitochondrial DNA.A U6-U67 mismatched base-pair appears inthecloverleaf folding ofthis geneandis maintained inthematurepotatomitochondrial tRNASer(GCU), whicharguesinfavourofthe hypothesis thattheediting systemof plant mitochondria canonly perform CtoUoroccasionally UtoCchanges.