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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Plastidial Glyceraldehyde-3-Phosphate Dehydrogenase Deficiency Leads to Altered Root Development and Affects the Sugar and Amino Acid Balance in Arabidopsis^1,[W]

Departament de Biologia Vegetal, Facultat de Farmàcia, Universitat de València, 46100 Burjassot, Valencia, Spain (J.M.-B., B.C.-M., J.S., R.R.); Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, 46022 Valencia, Spain (J.M.M.); Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas, Universidad Pública de Navarra, Gobierno de Navarra, 31192 Mutiloabeti, Nafarroa, Spain (E.B.-F., J.P.-R.); and Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla, California 92093–0116 (J.M.K.)

Glycolysis is a central metabolic pathway that, in plants, occurs in both the cytosol and the plastids. The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate with concomitant reduction of NAD⁺ to NADH. Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described. However, the in vivo functions of the plastidial isoforms remain unresolved. In this work, we have identified two Arabidopsis (Arabidopsis thaliana) chloroplast/plastid-localized GAPDH isoforms (GAPCp1 and GAPCp2). gapcp double mutants display a drastic phenotype of arrested root development, dwarfism, and sterility. In spite of their low gene expression level as compared with other GAPDHs, GAPCp down-regulation leads to altered gene expression and to drastic changes in the sugar and amino acid balance of the plant. We demonstrate that GAPCps are important for the synthesis of serine in roots. Serine supplementation to the growth medium rescues root developmental arrest and restores normal levels of carbohydrates and sugar biosynthetic activities in gapcp double mutants. We provide evidence that the phosphorylated pathway of Ser biosynthesis plays an important role in supplying serine to roots. Overall, these studies provide insights into the in vivo functions of the GAPCps in plants. Our results emphasize the importance of the plastidial glycolytic pathway, and specifically of GAPCps, in plant primary metabolism.

² Present address: BASF Plant Science Company GmbH, Carl-Bosch-Strasse 64, 67117 Limburgerhof, Germany.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Roc Ros (roc.ros{at}uv.es).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.143701

^* Corresponding author; e-mail roc.ros{at}uv.es.

Received June 26, 2009; accepted August 4, 2009; published August 12, 2009.