Abstract
Transport of dicarboxylates across the inner chloroplastic envelope membranes plays important roles such as the transfer of carbon skeletons to nitrogen assimilation pathway and transport of reducing equivalents. We have characterized transport properties of Arabidopsis 2-oxoglutarate/malate transporter (OMT) and general dicarboxylate transporter (DCT). In this study, we further investigated the physiological functions of both the transporters with Arabidopsis knock-out mutants. A knock-out mutant of DCT gene was non-viable in normal air but able to grow under the high CO2 condition to suppress photorespiration. The same phenotype was reported in an Arabidopsis CS156 mutant line. We found that DCT gene in the CS156 line has a single nucleotide mutation to cause an amino acid substitution. The OMT and DCT proteins can also transport oxaloacetate effectively. The profiles of oxaloacete uptake into chloroplasts isolated from the OMT or DCT knock-out mutants did not support the presence of a new oxaloacetate transporter.
