Jose F. Moran,3
Esther M. González,1 and
1Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, E-31006 Pamplona, Spain; 2Institute for Genome Research and Systems Biology, Center for Biotechnology, Bielefeld University, D-33594 Bielefeld, Germany; 3Instituto de Agrobiotecnología, Universidad Pública de Navarra-CSIC-Gobierno de Navarra, Campus de Arrosadia, E-31192-Mutilva Baja, Spain; 4Interactions Biotiques, UMR INRA 1301/Université de Nice Sophia-Antipolis/CNRS 6243, F-06903 Sophia-Antipolis, France; 5Agronomy Physiology Laboratory, Department of Agronomy, University of Florida, POB 110965, Gainesville, FL 32611, U.S.A.
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Accepted 11 January 2008.
Nitrogen fixation (NF) in legume nodules is very sensitive to environmental constraints. Nodule sucrose synthase (SS; EC 188.8.131.52) has been suggested to play a crucial role in those circumstances because its downregulation leads to an impaired glycolytic carbon flux and, therefore, a depletion of carbon substrates for bacteroids. In the present study, the likelihood of SS being regulated by oxidative signaling has been addressed by the in vivo supply of paraquat (PQ) to nodulated pea plants and the in vitro effects of oxidizing and reducing agents on nodule SS. PQ produced cellular redox imbalance leading to an inhibition of NF. This was preceded by the downregulation of SS gene expression, protein content, and activity. In vitro, oxidizing agents were able to inhibit SS activity and this inhibition was completely reversed by the addition of dithiothreitol. The overall results are consistent with a regulation model of nodule SS exerted by the cellular redox state at both the transcriptional and post-translational levels. The importance of such mechanisms for the regulation of NF in response to environmental stresses are discussed.
Additional keywords:carbon metabolism, Pisum sativum L.
© 2008 The American Phytopathological Society