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SYSTEMS BIOLOGY, MOLECULAR BIOLOGY, AND GENE REGULATION

Oxidative Pentose Phosphate Pathway-Dependent Sugar Sensing as a Mechanism for Regulation of Root Ion Transporters by Photosynthesis^1,[W]

Institut de Biologie Intégrative des Plantes, UMR 5004, Biochimie et Physiologie Moléculaire des Plantes, Agro-M/CNRS/INRA/SupAgro/UM2, F–34060 Montpellier, France (L.L., J.W., P.T., A.G.); Institut de Biologie Intégrative des Plantes, UMR 759, Ecophysiologie des Plantes Sous Stress Environnementaux, Agro-M/INRA/SupAgro, F–34060 Montpellier, France (M.P.); and Max Planck Institute for Molecular Plant Physiology, Wissenschaftspark Golm, D–14476 Potsdam, Germany (J.M.F.C.)

Root ion transport systems are regulated by light and/or sugars, but the signaling mechanisms are unknown. We showed previously that induction of the NRT2.1 NO₃^– transporter gene by sugars was dependent on carbon metabolism downstream hexokinase (HXK) in glycolysis. To gain further insights on this signaling pathway and to explore more systematically the mechanisms coordinating root nutrient uptake with photosynthesis, we studied the regulation of 19 light-/sugar-induced ion transporter genes. A combination of sugar, sugar analogs, light, and CO₂ treatments provided evidence that these genes are not regulated by a common mechanism and unraveled at least four different signaling pathways involved: regulation by light per se, by HXK-dependent sugar sensing, and by sugar sensing upstream or downstream HXK, respectively. More specific investigation of sugar-sensing downstream HXK, using NRT2.1 and NRT1.1 NO₃^– transporter genes as models, highlighted a correlation between expression of these genes and the concentration of glucose-6-P in the roots. Furthermore, the phosphogluconate dehydrogenase inhibitor 6-aminonicotinamide almost completely prevented induction of NRT2.1 and NRT1.1 by sucrose, indicating that glucose-6-P metabolization within the oxidative pentose phosphate pathway is required for generating the sugar signal. Out of the 19 genes investigated, most of those belonging to the NO₃^–, NH₄⁺, and SO₄^2– transporter families were regulated like NRT2.1 and NRT1.1. These data suggest that a yet-unidentified oxidative pentose phosphate pathway-dependent sugar-sensing pathway governs the regulation of root nitrogen and sulfur acquisition by the carbon status of the plant to coordinate the availability of these three elements for amino acid synthesis.

² These authors contributed equally to the article.

³ Present address: Institute of Plant Sciences, ETH Zurich, Universitätsstrasse 2, CH–8092 Zurich, Switzerland.

⁴ Present address: Michigan State University, S302 Plant Biology Lab, East Lansing, MI 48824–1312.

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: Laurence Lejay (lejay{at}supagro.inra.fr).

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

www.plantphysiol.org/cgi/doi/10.1104/pp.107.114710

^* Corresponding author; e-mail lejay{at}supagro.inra.fr.

Received December 7, 2007; accepted February 20, 2008; published February 27, 2008.

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