Multiple patterns of mtDNA reorganization in plants regenerated from different in vitro cultured explants of a single wheat variety.

We have previously shown that tissue cultures derived from various explants of the wheat variety Chinese Spring exhibit organ/tissue-specific changes in the organization of their mitochondrial genome. The aim of this work was to study the influence of passage out of in-vitro culture, and subsequent plant regeneration, on the in vitro "induced" reorganization of this genome. In all cases but one, subgenomic configurations present in both the donor parent and the tissue culture were evident, in corresponding regenerated plants. The presence, in regenerated plants, of subgenomic configurations found in tissue culture but undetectable in the donor parent appeared to be both timeand organ/tissue-dependent. Moreover, when present, these novel organizations were not systematically found in all regenerated plants. Finally, novel subgenomic configurations were specifically detected after passage out of in-vitro culture. As these results were obtained from a single plant variety, they clearly confirm the extreme plasticity of mitochondrial genome structure in response to in-vitro culture.