Molecular cloning and characterization of a mitochondrial dicarboxylate/tricarboxylate transporter gene in Citrus junos response to aluminum stress

A mitochondrial dicarboxylate/tricarboxylate carrier gene, CjDTC, was isolated from Citrus junos by the rapid amplification of cDNA ends and the Y-shaped adaptor-dependent extension methods. It consisted of a 472-base pair (bp) upstream regulatory region and an 897-bp open reading frame encoding a protein of 299 amino acids. Homologous analysis revealed that CjDTC protein might be a plant dicarboxylate/tricarboxylate carrier protein involved in the mitochondria dicarboxylate/tricarboxylate transport. The putative light responsiveness and salicylic acid responsiveness regulatory elements were identified in the upstream regulatory region of CjDTC. Southern blot analysis demonstrated the presence of a single CjDTC gene located on the genome of citrus. As shown by northern hybridization, CjDTC was expressed in all plant tissues examined and the highest transcript level was observed in roots with significantly lower transcript amounts in leaves and stems. Moreover, real-time polymerase chain reaction analysis demonstrated that CjDTC expression was induced by aluminum treatment, suggesting that CjDTC protein might be involved in the excretion of organic acids and rhizotoxic aluminum tolerance.