Mitochondria are highly dynamic organelles that can rapidly change their form and their distribution in response to hanging cellular energy needs. In plants they have been reported to be oval or sausage-like organelles capable of undergoing rounds of fusion and fission. With some exceptions, the observation of reticulartype morphologies has been restricted to mitochondrial mutants or to cells subjected to experimental perturbations. Although mitochondria contain their own DNA, mtDNA, and can synthesize proteins, they are only semi-autonomous organelles, since most of