The mitochondrial genome of Nicotinia plumbaginifolia: I. Electron microscopy reveals linear molecules falling in different size classes

DNA was isolated from DNase-treated, osmotically shocked mitochondria from leaves and calli of Nicotiana plumbaginifolia. Electron microscopic analysis only revealed linear molecules, although the same technique yielded a sizable fraction of circular mitochondrial DNA molecules in the fission yeast Schizosaccharomyces pombe. Most of the plant mitochondrial DNA molecules could be assigned to six size classes of 3.11 ± 0.19, 7.08 ± 0.53, 11.2 ± 0.29, 14.10 ± 0.23, 18.13 ± 0.39, and 23.17 ± 0.51 μm length (mean ± 95% confidence intervals). These results are compared with those obtained for mitochondrial genomes of other higher plants.