NADPH recycling systems in oxidative stressed pea nodules: a key role for the NADP+ -dependent isocitrate dehydrogenase.
The symbiosis between legumes and rhizobia is characterised by the formation of dinitrogen-fixing root nodules. In natural conditions, nitrogen fixation is strongly impaired by abiotic stresses which generate over-production of reactive oxygen species. Since one of the nodule main antioxidant systems is the ascorbate-glutathione cycle, NADPH recycling that is involved in glutathione reduction is of great relevance under stress conditions. NADPH is mainly produced by glucose 6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) from the oxidative pentose phosphate pathway, and also by NADP(+)-dependent isocitrate dehydrogenase (ICDH; EC 1.1.1.42). In this work, 10 microM paraquat (PQ) was applied to pea roots in order to determine the in vivo relationship between oxidative stress and the activity of the NADPH-generating enzymes in nodules. Whereas G6PDH and 6PGDH activities remained unchanged, a remarkable induction of ICDH gene expression and a dramatic increase of the ICDH activity was observed during the PQ treatment. These results support that ICDH has a key role in NADPH recycling under oxidative stress conditions in pea root nodules.
Marino
Daniel
D
Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadía, 31006, Pamplona, Spain.
González
Esther M
EM
Frendo
Pierre
P
Puppo
Alain
A
Arrese-Igor
Cesar
C
D002244:Carbon / Q000378:metabolism; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D006540:Herbicides / Q000494:pharmacology; D007521:Isocitrate Dehydrogenase / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D018384:Oxidative Stress; D010269:Paraquat / Q000494:pharmacology; D018532:Pisum sativum / Q000187:drug effects / Q000378:metabolism*; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D053204:Root Nodules, Plant / Q000187:drug effects / Q000378:metabolism
D006540:Herbicides; D009249:NADP; D002244:Carbon; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+); D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D010269:Paraquat