Rearrangement amplification, and assortment of mitochondrial DNA molecules in cultured cells of Brassica campestris. Theor Appl Genet 77: 17–25. 8 G. Bartoszewski et al

Summary. We compared Brassica campestr is mitochon-drial and chloroplast DNAs from whole plants and from a 2-year-old cell culture. No differences were observed in the chloroplast DNAs (cpDNAs), whereas the culture mitochondrial DNA (mtDNA) was extensively altered. Hybridization analysis revealed that the alterations are due entirely to rearrangement. At least two inversions and one large duplication are found in the culture mtDNA. The duplication element is shown to have the usual properties of a plant mtDNA high frequency "recombination repeat". The culture mtDNA exists as a complex heterogeneous population of rearranged and unrearranged molecules. Some of the culture-associated rearranged molecules are present in low levels in native plant tissue and appear to have sorted out and amplified in the culture. Other mtDNA rearrangements may have occurred e novo. In addition to alterations of the main mitochondrial genome, an 11.3 kb linear mtDNA plas-mid present in whole plants is absent from the culture. Contrary to findings in cultured cells of other plants, small circular mtDNA molecules were not detected in the B. campestr is cell culture