The plant homolog to the human sodium/dicarboxylic cotransporter is the vacuolar malate carrier.
Malate plays a central role in plant metabolism. It is an intermediate in the Krebs and glyoxylate cycles, it is the store for CO2 in C4 and crassulacean acid metabolism plants, it protects plants from aluminum toxicity, it is essential for maintaining the osmotic pressure and charge balance, and it is therefore involved in regulation of stomatal aperture. To fulfil many of these roles, malate has to be accumulated within the large central vacuole. Many unsuccessful efforts have been made in the past to identify the vacuolar malate transporter; here, we describe the identification of the vacuolar malate transporter [A. thaliana tonoplast dicarboxylate transporter (AttDT)]. This transporter exhibits highest sequence similarity to the human sodium/dicarboxylate cotransporter. Independent T-DNA [portion of the Ti (tumor-inducing) plasmid that is transferred to plant cells] Arabidopsis mutants exhibit substantially reduced levels of leaf malate, but respire exogenously applied [14C]malate faster than the WT. An AttDT-GFP fusion protein was localized to vacuole. Vacuoles isolated from Arabidopsis WT leaves exhibited carbonylcyanide m-chlorophenylhydrazone and citrate inhibitable malate transport, which was not stimulated by sodium. Vacuoles isolated from mutant plants import [14C]-malate at strongly reduced rates, confirming that this protein is the vacuolar malate transporter.
Emmerlich
Vera
V
Universität Kaiserslautern, Pflanzenphysiologie, Erwin Schrödinger-Strasse, D-67653 Kaiserslautern, Germany.
Linka
Nicole
N
Reinhold
Thomas
T
Hurth
Marco A
MA
Traub
Michaela
M
Martinoia
Enrico
E
Neuhaus
H Ekkehard
HE
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D017931:DNA Primers; D006801:Humans; D008293:Malates / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D029363:Organic Anion Transporters, Sodium-Dependent / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000378:metabolism*
D002352:Carrier Proteins; D017931:DNA Primers; D008293:Malates; D029363:Organic Anion Transporters, Sodium-Dependent