Endosymbiosis, carbon metabolism, metabolite transport, chloroplast envelope membrane, plastid evolution
All plastids trace their origin to a single ancient endo-symbiotic event approximately 1.6 billion years ago in which a photoautotrophic cyanobacterium was engulfed by a primitive mitochondriate eukaryote, which resulted in the birth of the first photosynthetic eukaryote. One of the crucial steps in forging endosymbiosis was connecting and coordinating the metabolisms of host and cyanobiont. Establishing such connection mandated the recruitment of solute transporters to the evolving plastid envelope membrane. Despite their importance for both understanding endosymbiosis and function of photosynthetic eukaryotic cells, still surprisingly little is known about the molecular identities of the metabolite transporters that connect the plastid with the cytosol. Here we provide an update on the current knowledge about chloroplast solute transporters and we will summarize recent achievements in elucidating their evolutionary history.