Conservation and differences of the Min system in the chloroplast and bacterial division site placement.

Chloroplasts are descended from a cyanobacterial endosymbiont and divide by binary fission. Reminiscent of the process in their bacterial ancestor, chloroplast division involves a part of cyanobacteria-derived division machineries in addition to those acquired during chloroplast evolution.1,2 In both bacterial and chloroplast division, formation of the FtsZ ring at the mid position is required for subsequent constriction and fission at the mid division site.1-4 As in bacteria, positioning of the FtsZ ring at the mid-chloroplast is mediated by the Min system.1,2 Recently, we identified the MCD1 protein, a plant-specific component of the Min system in Arabidopsis thaliana chloroplasts.5 Unlike other division components that have been acquired after endosymbiosis and function outside of the chloroplasts (i.e., in/on the outer envelope membrane),6-9 MCD1 functions inside the chloroplast. Since we already discussed about the function and significance of MCD1 as a division component of plant origin,5 here we focus on and discuss about the diversity and evolution of the Min system.