Cytochrome Oxidase Subunit II Gene from Carrot


Introhs in the cytochrome oxidase subunit II (COXII) gene of plant mitochondrial DNA (mtDNA) have been observed only in monocots. The COXII genes in dicots investigated to date do not contain introns. This is the rirst report of an intron in the COXII gene of a dicot. The presence ofan intron in the carrot COXII intron was verified by restriction mapping and hybridization using specific maize and wheat COXII probes. Regions of the carrot COXII intron are homologous to the maize COXII intron and homologous to the wheat COXII intron-insert as demonstrated by hybridization. Homology of these regions was confirmed by sequencing portions of the gene. A comparison of the restriction map of the carrot COXII gene with the restriction maps of the COXII genes from pea, Oeaothera, maize, wheat, and rice revealed that the carrot map coincides with the rice restriction map. Cyt oxidase, an important part of the respiratory chain, is located in the inner mitochondrial membrane and directs the transfer of electrons from Cyt c to 02. The enzyme complex is composed of seven subunits. Three subunits (I, II, and III) are encoded by mitochondrial DNA, while the other four subunits (IV, V, VI, and VII) are encoded by nuclear DNA. The nucleotide sequence of the COXII gene from five plants, pea (12), Oenothera (8), maize (7), wheat (4), and rice (9), is highly conserved. Nucleotide homology of the COXII gene within monocots is 99%, within dicots is 89%, and between the two groups is 89%. The monocots, maize (7), wheat (4), rice (9), and rye (4), have introns in the COXII gene, while the dicots, pea (12), Oenothera (8), broad bean (4), and cucumber (4) do not contain introns. The COXII genes of all three monocots contain introns which begin at 391 bp;4 however, the introns vary in size (Fig. 1). The introns are 794 bp, 1217 bp, and 1318 bp long in maize, wheat, and rice, respectively. The wheat intron 'This research was supported in part by a Grant-in-Aid of Research from Sigma Xi and a Graduate Enrichment Grant from the Department of Botany, Miami University, Oxford, 45056 (F. J. T.) and by a United States Department ofAgriculture-Agricultural Research Service Postdoctoral Fellowship (L. R. D.). 2A portion ofthis work was submitted by F. J. Turano to the Graduate School of Miami University, Oxford, OH, in partial fulfillment for the Ph.D. degree. Present address: USDA-ARS, Plant Molecular Genetics Laboratory, Beltsville, MD 20705. 3 Present address: DNA Plant Technology Corporation, Cinnaminson, NJ, 08077. 4Abbreviation: bp, base pairs. contains a region equal in size and 99.3% homologous to the maize intron. This region is interrupted by a 422 bp insert (wheat intron-insert) at 1062 bp from the start codon (4). Rice contains a 1217 bp region that is 98% homologous to the wheat COXII intron and it contains a 52 bp insertion at 1318 bp from the start codon. Thus, the rice intron contains regions that are homologous to the 794 bp maize intron, the 422 bp wheat intron-insert, and contains a unique 52 bp rice intron-insert. It is now possible to determine if these regions of the intron are present in the COXII gene based on DNA restriction analysis using specific endonucleases, namely BamHI, EcoRI, and Sall. The restriction

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@inproceedings{DebonteCytochromeOS, title={Cytochrome Oxidase Subunit II Gene from Carrot}, author={L R Debonte and Kenneth G. Wilson and Benjamin F. Matthews} }