Editing corrects mispairing in the acceptor stem of bean and potato mitochondrial phenylalanine transfer RNAs

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Abstract
Editing is a general event in plant mitochondrial messenger RNAs, but has never been detected in a plant mitochondrial transfer RNA (tRNA). We demonstrate here the occurence of a tRNA editing event in higher plant mitochondria: in both bean and potato, the C encoded at position 4 in the mitochondrial tRNAPhe(GAA) gene is converted into a U in the mature tRNA. This nucleotide change corrects the mismatched C4-A69 base-pair which appears when foldin the gene sequence into the cloverleaf structure and it is consistent with the fact that C to U transitions constitute the common editing events affecting plant mitochondrial messenger RNAs. The tRNAPhe(GAA) gene is located upstream of the single copy tRNAPro(UGG) gene in both the potato and the bean mitochondrial DNAs. The sequences of potatoand bean tRNAPro(UGG) genes are colinear with the sequence of the mature bean mitochondrial tRNAPro(UGG), demonstrating that this tRNA is not edited. A single copy tRNAserGCU) gene was found upstream of the tRNAPhe gene in the potato mitochondrial DNA. A U6-U67 mismatched base-pair appears in the cloverleaf folding of this gene and is maintained in the mature potato mitochondrial tRNASer(GCU), which argues in favour of the hypothesis that the editing system of plant mitochondria can only perform C to U or occasionally U to C changes.