Solute transporters as connecting elements between cytosol and plastid stroma

Metabolite translocators in the inner membrane of the plastid envelope are the interface between cytosolic and plastidial metabolism. Hence, they integrate plastidial pathways, such as photosynthesis, starch biosynthesis, the oxidative pentose phosphate pathway and the shikimate pathway, into the metabolic network of plant cells. Metabolite transporters not only catalyze the flux of metabolites between compartments but also represent information pathways that communicate the metabolic status of the various compartments within plant cells. Recently, a pentose-phosphate translocator was shown to be a novel member of the phosphate translocator protein family. Furthermore, a protein of previously unknown function was identified as a novel type of maltose transporter, and a glutamate/malate translocator that is involved in photorespiration was discovered. In addition, the pathway for maltose metabolism in the cytosol has been unraveled.