Transcriptional and physiological changes in relation to Fe uptake under conditions of Fe-deficiency and Cd-toxicity in roots of Vigna radiata L.

ABSTRACT

We investigated transcriptional and physiological changes in relation to Fe transport and uptake under various conditions of iron (Fe)-deficiency and cadmium (Cd) toxicity. Responses to four such Fe/Cd conditions were evaluated, revealing that oxidative stress was generated in the presence of Cd, followed by a decrease in Fe and an increase in Cd concentrations in green gram (Vigna radiata) material, whereas supplementation with Fe had a protective effect against Cd toxicity. The involvement of enzymes in Fe-uptake for the formation of root-nodules was largely reduced in the presence of Cd toxicity, a condition recovered by Fe-supplementation. Insufficient ferric chelate reducing activity in Fe-deprived roots in the presence of Cd was also largely improved by Fe supplementation. The expression of Fe(2+) transporters (IRT1, IRT2, and IRT3), Fe(III) chelate reductase (FRO1-FRO8) and phytochelatin synthase (PCS1, PCS2 and PCS3) genes was up regulated for the first 5 days and decreased after 10 days in roots in the presence of Cd toxicity, but was sustained with Fe-supplementation. Additionally, root biomass was fully recovered in plants in the presence of Fe during Cd toxicity. Our results suggest that Fe-status plays a significant role in ameliorating the damage in Fe transport for chelation and its uptake caused by Cd toxicity. This supports the hypothesis that leguminous plants, particularly those that are sensitive to Fe such as green gram, can cope to some extent with Cd toxicity by improving the uptake and transport of Fe.