MOSAIC OPEN READING FRAMES IN THE ARABIDOPSIS-THALIANA MITOCHONDRIAL GENOME

In the mitochondrial genome of Arabidopsis thaliana eight mosaic open reading frames arose by recombination of fragments duplicated from one or more mitochondrial genes. These duplications represent unedited se quences, suggesting their derivation from genomic DNA rather than RNA. Five of the chimeric reading frames contain the information for the N -terminus of the original polypeptide and 5' upstream regions. These o bservations suggest that the generation of novel open reading frames i n plant mitochondria can occur rather easily by chance extensions of d uplicated gene fragments. The presence of so many mosaic open reading frames in the normal Arabidopsis thaliana mitochondrial genome suggest s that such recombined sequences interfere only occasionally and fortu itously with the peak mitochondrial performance presumably required du ring pollen maturation, and usually do not cause a cytoplasmic male st erile phenotype.