Movement of Genetic Material Between the Chloroplast and Mitochondrion in Higher Plants

The organelles within the eukaryotic cell have originated in one of two ways: I, the mitochondrion and chloroplast originally descended from free living bacteria-like organisms which entered into an endosymbiotic relationship within a host cell having a nuclear genome, or II, that the nuclear and organelle genomes became physically compartmentalized and functionally specialized within a single cell. The arguments relating to these two evolutionary hypotheses have been discussed in detail elsewhere (Gray and Doolittle, 1982) and will not be subject to discussion here, though it does appear that the endosymbiont hypothesis is more acceptable for the origin of both the mitochondrion and chloroplast.