Fe modulates Cd-induced oxidative stress and the expression of stress responsive proteins in the nodules of Vigna radiata

The aim of this study was to investigate the protective role of Fe in providing tolerance against Cd-stress in root nodules of Vigna radiata, because Cd may be more deleterious in the absence of Fe. Biochemical, histological and proteomic responses to Cd-exposure (50 mu M CdCl2) were examined under Fe-sufficient (+Fe/+Cd) or Fe-deficient (-Fe/+Cd) soils by comparing non -Cd exposed control (+Fe/-Cd) plants with additional control of Fe-deficient and non-exposed Cd plants (-Fe/-Cd). Cd-exposure negatively affected on growth and some physiological parameters of host plant and nodules, and also induced oxidative stress with the decline of antioxidative enzyme activities. The negative effects of Cd-exposure in +Fe/+Cd plants were much less than those in -Fe/+Cd and -Fe/-Cd ones. When compared with -Fe/Cd and -Fe/-Cd plants, a marked improvement of bacteriod development and cell division was observed and deformation of cell wall remarkably alleviated in the nodules of (+Fe/Cd) plants. Proteomic study revealed that 20 proteins were differentially expressed by Fe/Cd combined treatment. Eleven proteins of interest were identified and classified as precursor for RNA metabolism, storage of seeds, hypothetical proteins, and unknown proteins. These results indicate that Fe plays a pivotal role in alleviating Cd-stress, as evidence by reduction in oxidative damage and protection of cell wall and bacteriods in nodules.