The Use Of A Mitochondrial (Mt) Gene Library For Characterization Of Mt Genomes And The Search Of New Mt Genes In Higher-Plants

The mt genome of higher plants (size varying from 200 to 560 kb according to the species) consists of a heterogeneous population of molecules resulting from intra- or inter-molecular recombination. Besides the highly conserved coding sequences of mt genes, other sequences, for example, promiscuous chloroplast sequences, may be found. The genes may be interrupted by introns; in some cases, one or more introns have been split, leading to the scattering of the gene segments to remote parts of the genome; this structure requires trans-splicing steps for the mature messenger RNA to be obtained. Over 25 genes have been identified so far that are usable, as universal polymorphism markers in RFLP (restriction fragment length polymorphism) characterization of mt genomes due to sequence conservation. During the search for new genes we identified 2 new coding sequences, nad5 and nad6; nad6 consists of a single reading frame whereas nad5 is a split gene whose 3 independent segments are independently transcribed.