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EMBO J. 1992 Nov;11(11):3815-20.

Silent mitochondrial and active nuclear genes for subunit 2 of cytochrome c oxidase (cox2) in soybean: evidence for RNA-mediated gene transfer.

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Canadian Institute for Advanced Research, Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia.


In most plants and other eukaryotes investigated, the mitochondrial genome carries the gene encoding subunit 2 of cytochrome c oxidase (cox2). In this paper, we show that the previously reported mitochondrial cox2 of soybean is actually silent, and that there is an expressed, single-copy, nucleus-encoded cox2. Molecular cloning and sequence analysis of cox2 cDNA and genomic clones show that the soybean nuclear gene encodes an N-terminal extension that resembles a signal sequence for mitochondrial import and whose coding sequence is separated by an intron from that corresponding to mtDNA-encoded cox2. Comparison of soybean mitochondrial and nuclear cox2 sequences clearly indicates that in an ancestor of soybean, cox2 was transferred from the mitochondrion to the nucleus via a C-to-U edited RNA intermediate.

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