Immunolocalization of ferritin in determinate and indeterminate legume root nodules

In 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.