title: The Arabidopsis mutant dct is deficient in the plastidic glutamate/malate translocator DiT2.
abstract: The Arabidopsis mutant dicarboxylate transport (dct) is one of the classic mutants in the photorespiratory pathway. It requires high CO2 levels for survival. Physiologic and biochemical characterization of dct indicated that dct is deficient in the transport of dicarboxylates across the chloroplast envelope membrane. Hence, re-assimilation of ammonia generated by the photorespiratory cycle is blocked. However, the defective gene in dct has not been identified at the molecular level. Here, we report on the molecular characterization of the defective gene in dct, on the complementation of the mutant phenotype with a wild-type cDNA, and on the functional characterization of the gene product, DiT2, in a recombinant reconstituted system. Furthermore, we provide the kinetic constants of recombinant DiT1 and DiT2, and we discuss these data with respect to their functions in ammonia assimilation. Moreover, an analysis of the transcript levels of DiT1 and DiT2 in different C3- and C4-type plant species is presented, and we demonstrate that the substrate specificity of DiT2 from the C4-plant Flaveria bidentis is similar to its counterpart from C3 plants.
authors.affiliation: Lehrstuhl Botanik II, Universität zu Köln, Gyrhofstr. 15, D-50931, Köln, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Renné
authors.forename: Uta
authors.initials: U
authors.lastname: Dressen
authors.forename: Ulrike
authors.initials: U
authors.lastname: Hebbeker
authors.forename: Diana
authors.initials: D
authors.lastname: Hille
authors.forename: Ulf-Ingo
authors.initials: UI
authors.lastname: Flügge
authors.forename: Peter
authors.initials: P
authors.lastname: Westhoff
authors.forename: Andreas P M
authors.initials: AP
authors.lastname: Weber
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D029382:Dicarboxylic Acid Transporters / Q000235:genetics* / Q000378:metabolism*; D037142:Flaveria / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D017343:Genes, Plant; D007700:Kinetics; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D018087:Plastids / Q000378:metabolism; D017354:Point Mutation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D018724:Spinacia oleracea / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D018744:DNA, Plant; D029382:Dicarboxylic Acid Transporters; D024101:Mitochondrial Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; C066909:2-oxoglutarate-malate carrier protein