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First published online August 14, 2003; 10.1104/pp.102.016766 Plant Physiology 133:253-262 (2003) © 2003 American Society of Plant Biologists Does Lowering Glutamine Synthetase Activity in Nodules Modify Nitrogen Metabolism and Growth of Lotus japonicus?1Laboratoire Nutrition Azotée des Plantes, Institut National de la Recherche Agronomique, Route de St. Cyr, 78280 Versailles cedex, France (J.H., M.-A.P.d.C., O.S., B.H.); and Laboratoire de Biochimie et Biologie Moléculaire, Unité Mixte de Recherche Physiologie Moléculaire des Semences, Unité de Formation et de Recherche Sciences, Université d'Angers, 2 Boulevard Lavoisier 49045 Angers cedex 01, France (M.-A.P.d.C.)
A cDNA encoding cytosolic glutamine synthetase (GS) from Lotus japonicus was fused in the antisense orientation relative to the nodule-specific LBC3 promoter of soybean (Glycine max) and introduced into L. japonicus via transformation with Agrobacterium tumefaciens. Among the 12 independent transformed lines into which the construct was introduced, some of them showed diminished levels of GS1 mRNA and lower levels of GS activity. Three of these lines were selected and their T1 progeny was further analyzed both for plant biomass production and carbon and nitrogen (N) metabolites content under symbiotic N-fixing conditions. Analysis of these plants revealed an increase in fresh weight in nodules, roots and shoots. The reduction in GS activity was found to correlate with an increase in amino acid content of the nodules, which was primarily due to an increase in asparagine content. Thus, this study supports the hypothesis that when GS becomes limiting, other enzymes (e.g. asparagine synthetase) that have the capacity to assimilate ammonium may be important in controlling the flux of reduced N in temperate legumes such as L. japonicus. Whether these alternative metabolic pathways are important in the control of plant biomass production still remains to be fully elucidated.
1 This work was supported by the Biotechnology and Biological Science Research Council-Institut National de la Recherche Agronomique (postdoctoral fellowship to J.H.). 2 These authors contributed equally to the paper. 3 Present address: Laboratoire de Microbiologie et Biologie Végétales, Université de Nice-Sophia-Antipolis, 06100 Nice, France. * Corresponding author; e-mail hirel{at}versailles.inra.fr; fax 33-1-30 -83-30-96. Received October 28, 2002; returned for revision February 17, 2003; accepted May 29, 2003. This article has been cited by other articles:
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