Redox-activated expression of the cytosolic copper/zinc superoxide dismutase gene in Nicotiana.

Superoxide dismutases (SODs; superoxide: superoxide oxidoreductase, EC 1.15.1.1) play a key role in protection against oxygen radicals, and SOD gene expression is highly induced during environmental stress. To determine the conditions of SOD induction, the promoter of the cytosolic copper/zinc SOD (Cu/ZnSODcyt) gene was isolated in Nicotiana plumbaginifolia and fused to the beta-glucuronidase reporter gene. Oxidative stress is likely to alter the cellular redox in favor of the oxidized status. Surprisingly, the expression of the Cu/ZnSODcyt gene is induced by sulfhydryl antioxidants such as reduced glutathione, cysteine, and dithiothreitol, whereas the oxidized forms of glutathione and cysteine have no effect. It is therefore possible that reduced glutathione directly acts as an antioxidant and simultaneously activates the Cu/ZnSODcyt gene during oxidative stress

Immunolocalization of ferritin in determinate and indeterminate legume root nodules

10 páginas,5 figurasIn eukaryotic organisms ferritin is a protein involved in the storage of iron. The occurrence of ferritin and its relationship to the effectiveness of the nitrogen-fixing activity have been previously studied during the early stages of the nodule development by biochemical methods. We have used immunocytochemistry techniques to determine the precise location of ferritin and the behavior of this protein along the nodule development. The major localization was found in plastids and amyloplasts of infected and uninfected cells of the three legume nodules studied. A decrease of the immunolabelling was observed in infected cells of lupin and soybean senescing nodules and in the senescent zone of indeterminate alfalfa nodules. In the cortex of soybean and lupin nodules, ferritin increased during nodule ageing and the immunogold particles were mainly located in crystalline structures. The putative role of ferritin and plastids during nodule development is discussed.This work was supported by an EC Human and Capital Mobility grant, Project CHRX-CT94-0605.Peer reviewe