Location and nucleotide sequence of two tRNA genes and a tRNA pseudo-gene in the maize mitochondrial genome: evidence for the transcription of a chloroplast gene in mitochondria.

We report the nucleotide sequence of three tRNA genes from maize mitochondria. The genes are located in two BamHI fragments, 3.55 and 5.7 kb long, adjacent to the S2 sequence in the maize mitochondrial genome. On the 3.55 kb BamHI fragment, we have characterized a tRNA(Cys)(GCA) gene. A strong sequence homology of this tRNA(Cys)(GCA) gene with its chloroplast counterpart in wheat suggests that it may be part of a chloroplast DNA insertion into the mitochondrial genome. This gene has been found to be transcribed in the mitochondrion. Two tRNA genes are located on the 5.7 kb BamHI fragment, separated from each other by 250 bp. One is a mitochondrial tRNA(Ser)(GCU) gene. The other, a non-transcribed tRNA(Phe)-like gene, is interrupted by a 49 base-pair inserted DNA sequence in the variable loop and has a Leu (UAA) anticodon.