Three mitochondria! tRNA genes from Arabidopsis thaliana: evidence for the conversion of a tRNA"* gene into a tRNA gene

Three tRNA genes have been isolated from a genomic library of Arabidopsis thaliana: a tRNA (GCU), a tRNA (GUA) and a tRNA (UUC) genes. These genes are located closely on the same DNA fragment. The tRNA and the tRNA genes have both 99% sequence similarity with their mitochondrial counterparts from higher plants indicating that these three tRNA genes are mitochondrial. The tRNAv gene shows a particular high sequence similarity with the mitochondrial tRNA pseudogene from maize, and both genes are flanked by a tRNA gene in the upstream region. Extensive sequence comparisons of the Arabidopsis thaliana mitochondrial sequence containing the three tRNA genes and the corresponding region from maize and soybean mitochondria have shown evidence that the lRNAy gene has been generated from a mitochondrial tRNA gene. The conversion was accomplished by three genetic events: a 4 base-pair deletion, a mutation and a recombination, which led to the transformation of the acceptor stem and the anticodon.