Abstract
Chloroplasts evolved from a cyanobacterial endosymbiont and chloroplast division requires the formation of an FtsZ division ring, which is descended from the cytokinetic machinery of cyanobacteria. As in bacteria, the positioning of the chloroplast FtsZ ring is regulated by MinD and MinE proteins. However, chloroplast division also involves mechanisms invented by the eukaryotic host cell. Here we show that a plant-specific protein MULTIPLE CHLOROPLAST DIVISION SITE 1 (MCD1) regulates FtsZ ring positioning in Arabidopsis thaliana chloroplasts. MCD1 is required for chloroplast division, localizing at the division sites and punctate structures dispersed on the inner envelope. Further analyses revealed that MCD1 and MinD affect each other through direct interaction to position the FtsZ ring. These results suggest that the plant cell has a new component to modulate the bacteria-derived Min system in the initiation of the chloroplast division.
