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Marino D, Gonzalez EM, Frendo P, Puppo A, Arrese-Igor C: NADPH recycling systems in oxidative stressed pea nodules: a key role for the NADP+ -dependent isocitrate dehydrogenase. Planta. 2007 Jan;225(2):413-21. Epub 2006 Aug 2.
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. |
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