Dynamin and FtsZ: Missing links in mitochondrial and bacterial division

FtsZ forms the cytoskeletal framework of the cytokinetic ring in bacteria, and appears to play the major role in constriction of the furrow at septation. Until recently, FtsZ had been found in every eubacterium and archaebacterium, and was thought to be the major and essential component of the division machine (Erickson, 1997). FtsZ has also been found in chloroplasts (Osteryoung et al., 1998), which was expected since these plastids originated from bacterial ancestors. An apparent missing link was that FtsZ was absent from mitochondria, which are also of prokaryotic origin. There is no FtsZ in the completed genomes of Saccharomyces cerevisiae and Caenorhabditis elegans, and none in the extensive EST databases from human and animals. Now the mystery of mitochondrial cell division seems well on its way to resolution: most mitochondria have replaced FtsZ with dynamin for division. An important missing link is the recent discovery by Beech et al. (2000), of a mitochondrion that still uses FtsZ. But even as the division of mitochondria is being resolved, a new paradox has appeared, as several prokaryotes have now been discovered to have no FtsZ.