Abstract
2-Oxoglutarate/malate transporter (OMT) and general dicarboxylate transporter (DCT) are located in the inner plastidic envelope membrane and cooperatively function in import of cytosolic 2-oxoglutarate generated from TCA cycle and photorespiration, and export of glutamate generated from stromal GS/GOGAT cycle. Therefore, the OMT/DCT transport system is thought to connect carbon and nitrogen metabolic pathways. We are extensively investigating the physiological functions of both the transporters with Arabidopsis knock-out and overexpression lines. A new T-DNA insertion mutant of the OMT gene showed a delay in growth compared with wild-type plant. In contrast, overexpression lines that had several ten-fold higher accumulation of OMT mRNA and two-fold higher activities of substrate transport showed no difference in phenotype compared with the wild-type plant. The Arabidopsis OMT gene expresses transiently in response to inorganic nitrogen supplementation. We revealed that this gene expression is triggered by nitrate ion.
