Transfection of plant mitochondria and in organello gene integration

Investigation and manipulation of mitochondrial genetics in animal and plant cells remains restricted by the lack of an efficient in vivo transformation methodology. Mitochondrial transfection in whole cells and maintenance of the transfected DNA are main issues on this track. We showed earlier that isolated mitochondria from different organisms can import DNA. Exploiting this mechanism, we assessed the possibility to maintain exogenous DNA in plant organelles. Whereas homologous recombination is scarce in the higher plant nuclear compartment, recombination between large repeats generates the multipartite structure of the plant mitochondrial genome. These processes are under strict surveillance to avoid extensive genomic rearrangements. Nevertheless, following transfection of isolated organelles with constructs composed of a partial gfp gene flanked by fragments of mitochondrial DNA, we demonstrated in organello homologous recombination of the imported DNA with the resident DNA and integration of the reporter gene. Recombination yielded insertion of a continuous exogenous DNA fragment including the gfp sequence and at least 0.5 kb of flanking sequence on each side. According to our observations, transfection constructs carrying multiple sequences homologous to the mitochondrial DNA should be suitable and targeting of most regions in the organelle genome should be feasible, making the approach of general interest.