Evidence for transcriptional and post-translational regulation of sucrose synthase in pea nodules by the cellular redox state.
Nitrogen fixation (NF) in legume nodules is very sensitive to environmental constraints. Nodule sucrose synthase (SS; EC 2.4.1.13) 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.
Marino
Daniel
D
Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, E-31006 Pamplona, Spain.
Hohnjec
Natalija
N
Küster
Helge
H
Moran
Jose F
JF
González
Esther M
EM
Arrese-Igor
Cesar
C
D003958:Diamide / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015151:Immunoblotting; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053204:Root Nodules, Plant / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D010940:Plant Proteins; D003958:Diamide; D006861:Hydrogen Peroxide; D005964:Glucosyltransferases; C022699:sucrose synthase