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Genes for tRNA(Asp), tRNA(Pro), tRNA(Tyr) and two tRNAs(Ser) in wheat mitochondrial DNA

Joyce, P.B.M., Spencer, D.F., Bonen, L., Gray, M.W.
Plant molecular biology 1988 v.10 no.3 pp. 251-262
protein secondary structure, serine, aspartic acid, restriction mapping, mitochondrial DNA, transfer RNA, proline, tyrosine, genes, Triticum aestivum, molecular conformation, promoter regions
We have begun a systematic search for potential tRNA genes in wheat mtDNA, and present here the sequences of regions of the wheat mitochondrial genome that encode genes for tRNA Asp (anticodon GUC), tRNAPro (UGG), tRNATyr (GUA), and two tRNAsSer (UGA and GCU). These genes are all solitary, not immediately adjacent to other tRNA or known protein coding genes. Each of the encoded tRNAs can assume a secondary structure that conforms to the standard cloverleaf model, and that displays none of the structural aberrations peculiar to some of the corresponding mitochondrial tRNAs from other eukaryotes. The wheat mitochondrial tRNA sequences are, on average, substantially more similar to their eubacterial and chloroplast counterparts than to their homologues in fungal and animal mitochondria. However, an analysis of regions approximately 150 nucleotides upstream and approximately 100 nucleotides downstream of the tRNA coding regions has revealed no obvious conserved sequences that resemble the promoter and terminator motifs that regulate the expression of eubacterial and some chloroplast tRNA genes. When restriction digests of wheat mtDNA are probed with 32P-labelled wheat mitochondrial tRNAs, < 20 hybridizing bands are detected, whether enzymes with 4 bp or 6 bp recognition sites are used. This suggests that the wheat mitochondrial genome, despite its large size, may carry a relatively small number of tRNA genes.