Abstract
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 μM 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.
Highlights
Cadmium is non-essential element that negatively affects plant growth and development of plant including root nodules
The content of Fe in all four treated soils were estimated and it was observed that Fe content in -Fe/-Cd was decreased compared to control and was more severely decreased in -Fe-deficient condition (Fe/?Cd) plants (Fig. 1a) whereas in ?Fe/ ?Cd plants the content of Fe was increased
The Cd content increased in ?Fe/?Cd compared to control which was more severely increased in -Fe/?Cd plants in -Fe/-Cd and in control plants the content of Cd was found in trace amounts (Fig. 1b)
Summary
Cadmium is non-essential element that negatively affects plant growth and development of plant including root nodules. It is recognized as a significant major pollutant due to its considerable solubility and high toxicity (Pinto et al 2004). Cd is well known to induce oxidative stress in plants including legume (Balestrasse et al 2004). Cadmium can exert toxic effects through its high affinity for sulfuhydral groups in proteins and other biological molecules (Sanita di Toppi and Gabbrielli 1999; Fagioni et al 2009) and may inhibit metabolic reactions in cell organelles of root-nodules. Cd-induced oxidative damage is often severe in Fe-defiency because Fe-deficiency provokes a
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