TY - JOUR
T1 - Identifying and characterizing plastidic 2-oxoglutarate/malate and dicarboxylate transporters in Arabidopsis thaliana
AU - Taniguchi, Mitsutaka
AU - Taniguchi, Yojiro
AU - Kawasaki, Michio
AU - Takeda, Satomi
AU - Kato, Tomohiko
AU - Sato, Shusei
AU - Tabata, Satoshi
AU - Miyake, Hiroshi
AU - Sugiyama, Tatsuo
N1 - Funding Information:
We are grateful to Dr. Makiko Aichi (Chubu University) and Mr. Takatoshi Kiba (Nagoya University) for their invaluable suggestions. This work was supported by grants from the Ministry of Education, Culture, Sports, Science and Technology (Grant No. 12740434 and 14540593).
PY - 2002
Y1 - 2002
N2 - We characterized three Arabidopsis genes, AtpOMT1, AtpDCT1 and AtpDCT2, localized on chromosome 5 and homologous to spinach chloroplastic 2-oxoglutarate/malate transporter (OMT) gene. The yeast-expressed recombinant AtpOMT1 protein transported malate and 2-oxoglutarate but not glutamate. By contrast, the recombinant AtpDCT1 protein transported 2-oxoglutarate and glutamate at similar affinities in exchange for malate. These findings suggested that AtpOMT1 is OMT and AtpDCT1 is a general dicarboxylate transporter (DCT). The recombinant proteins could also transport oxaloacetate at the same binding sites for dicarboxylates. In particular, the AtpOMT1 had a Km value for oxaloacetate one order of magnitude lower than those for malate and 2-oxoglutarate. Although the transcripts for the three genes were accumulated in all tissues examined, the expression of the genes in leaf tissues was light inducible. The expression of the three genes was also induced by nitrate supplement but the induction was most prominent and transient in AtpOMT1 similar to nitrate reductase gene. These findings lead to a proposition that AtpOMT1 functions as an oxaloacetate transporter in the malate-oxaloacetate shuttle across chloroplast membranes. We identified T-DNA insertional mutants of AtpOMT1 and AtpDCT1. Although the AtpOMT1 mutants could grow normally in normal air, the AtpDCT1 mutants were non-viable under the same conditions. The AtpDCT1 mutants were able to grow under the high CO2 condition to suppress photorespiration. These findings suggested that at least AtpDCT1 is a necessary component for photorespiratory nitrogen recycling.
AB - We characterized three Arabidopsis genes, AtpOMT1, AtpDCT1 and AtpDCT2, localized on chromosome 5 and homologous to spinach chloroplastic 2-oxoglutarate/malate transporter (OMT) gene. The yeast-expressed recombinant AtpOMT1 protein transported malate and 2-oxoglutarate but not glutamate. By contrast, the recombinant AtpDCT1 protein transported 2-oxoglutarate and glutamate at similar affinities in exchange for malate. These findings suggested that AtpOMT1 is OMT and AtpDCT1 is a general dicarboxylate transporter (DCT). The recombinant proteins could also transport oxaloacetate at the same binding sites for dicarboxylates. In particular, the AtpOMT1 had a Km value for oxaloacetate one order of magnitude lower than those for malate and 2-oxoglutarate. Although the transcripts for the three genes were accumulated in all tissues examined, the expression of the genes in leaf tissues was light inducible. The expression of the three genes was also induced by nitrate supplement but the induction was most prominent and transient in AtpOMT1 similar to nitrate reductase gene. These findings lead to a proposition that AtpOMT1 functions as an oxaloacetate transporter in the malate-oxaloacetate shuttle across chloroplast membranes. We identified T-DNA insertional mutants of AtpOMT1 and AtpDCT1. Although the AtpOMT1 mutants could grow normally in normal air, the AtpDCT1 mutants were non-viable under the same conditions. The AtpDCT1 mutants were able to grow under the high CO2 condition to suppress photorespiration. These findings suggested that at least AtpDCT1 is a necessary component for photorespiratory nitrogen recycling.
KW - 2-Oxoglutarate/malate transporter
KW - Arabidopsis thaliana
KW - Dicarboxylate transporter
KW - Oxaloacetate transporter
KW - Plastid
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U2 - 10.1093/pcp/pcf109
DO - 10.1093/pcp/pcf109
M3 - Article
C2 - 12154133
AN - SCOPUS:0036345904
VL - 43
SP - 706
EP - 717
JO - Plant and Cell Physiology
JF - Plant and Cell Physiology
SN - 0032-0781
IS - 7
ER -