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Title: “Cell-to-Cell Movement of Plastics and Mitochondria in Plants”

Host: Meng Chen

Abstract: To detect organelle movement between cells, we grafted two different species of tobacco, Nicotiana tabacum and Nicotiana sylvestris. We initiated tissue culture from sliced graft junctions and selected for clonal lines in which gentamycin resistance encoded in the N. tabacum nucleus was combined with spectinomycin resistance encoded in N. sylvestris plastids. We obtained evidence for cell-to-cell movement of the entire 161-kb plastid genome in these plants, most likely in intact plastids 1. In some of the clones, mitochondrial DNA movement was also detected in regenerated plants by restoration of pollen fertility in the cytoplasmic male sterile (CMS) graft partner 2. Homologous recombination yielded fertile and sterile mitochondrial genomes due to recombination at alternative sites, linking CMS to a unique open reading frame in CMS mitochondria. Cell-to-cell movement of plastids and mitochondria supports the universality of intercellular organelle trafficking and enables modification of the mitochondrial genome by DNA transmitted from a sexually incompatible species. A mitochondrial trait of commercial interest could be CMS in species, such as tomato, where CMS currently does not exist.