Endosymbiosis and evolution of the plant cell

The bacterial origins of plastid division and protein import by plastids ar e beginning to emerge - thanks largely to the availability of a total genom e sequence for a cyanobacterium, Despite existing for hundreds of millions of years within the plant cell host, the chloroplast endosymbiont retains c lear hallmarks of its bacterial ancestry. Plastid division relies on protei ns that are also responsible for bacterial division, although may of the ge nes for these proteins have been confiscated by the host. Plastid protein i mport on the other hand relies on proteins that seem to have functioned ori ginally as exporters but that have now been persuaded to operate in the rev erse direction to traffic proteins from the host cell into the endosymbiont .