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First published online March 4, 2004; 10.1104/pp.103.032102 Plant Physiology 134:969-978 (2004) © 2004 American Society of Plant Biologists A Nodule-Specific Dicarboxylate Transporter from Alder Is a Member of the Peptide Transporter Family1Department of Life Science, Pohang University of Science and Technology, Hyoja-dong, san 31, Pohang 790–784, Korea (J.J., S.S., Y.L.); Department of Molecular Biology, Agricultural University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands (C.G., K.P.); Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, 50829 Köln, Germany (C.G.); Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan (Y.-F.T.); Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food, and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel (N.M.); School of Biological Sciences, Seoul National University, Kwanak-gu, Seoul 151–742, Korea (C.J.O., C.S.A.); and Albrecht von Haller Institute for Plant Sciences, Plant Biochemistry, Göttingen University, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany (K.N.D., K.P.)
Alder (Alnus glutinosa) and more than 200 angiosperms that encompass 24 genera are collectively called actinorhizal plants. These plants form a symbiotic relationship with the nitrogen-fixing actinomycete Frankia strain HFPArI3. The plants provide the bacteria with carbon sources in exchange for fixed nitrogen, but this metabolite exchange in actinorhizal nodules has not been well defined. We isolated an alder cDNA from a nodule cDNA library by differential screening with nodule versus root cDNA and found that it encoded a transporter of the PTR (peptide transporter) family, AgDCAT1. AgDCAT1 mRNA was detected only in the nodules and not in other plant organs. Immunolocalization analysis showed that AgDCAT1 protein is localized at the symbiotic interface. The AgDCAT1 substrate was determined by its heterologous expression in two systems. Xenopus laevis oocytes injected with AgDCAT1 cRNA showed an outward current when perfused with malate or succinate, and AgDCAT1 was able to complement a dicarboxylate uptake-deficient Escherichia coli mutant. Using the E. coli system, AgDCAT1 was shown to be a dicarboxylate transporter with a Km of 70 µM for malate. It also transported succinate, fumarate, and oxaloacetate. To our knowledge, AgDCAT1 is the first dicarboxylate transporter to be isolated from the nodules of symbiotic plants, and we suggest that it may supply the intracellular bacteria with dicarboxylates as carbon sources.
Article, publication date, and citation information can be found at http://www.plantphysiol.org/cgi/doi/10.1104/pp.103.032102. 1 This work was supported in part by the National Science Council of Taiwan (grant no. NSC86–2811–B–001–076R to Y.L. when at Academia Sinica), by the National Research Laboratory program of Ministry of Science and Technology of Korea (to Y.L.), and by the Dutch Organization for Scientific Research (to C.G. and K.P. when at Wageningen University). 2 These authors contributed equally to the work. 3 These authors contributed equally to the manuscript. * Corresponding author; e-mail ylee{at}postech.ac.kr; fax 82–54–2792199. Received August 22, 2003; returned for revision October 12, 2003; accepted December 23, 2003. This article has been cited by other articles:
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