Abstract
Cadmium (Cd) contamination of agricultural soils is an increasingly serious problem. Measures need to be developed to minimize Cd entering the human food chain from contaminated soils. We report here that, under Cd exposure condition, application with low doses of (0.1–0.5 μM) abscisic acid (ABA) clearly inhibited Cd uptake by roots and decreased Cd level in Arabidopsis wild-type plants (Col-0). Expression of IRT1 in roots was also strongly inhibited by ABA treatment. Decrease in Cd uptake and the inhibition of IRT1 expression were clearly lesser pronounced in an ABA-insensitive double mutant snrk2.2/2.3 than in the Col-0 in response to ABA application. The ABA-decreased Cd uptake was found to correlate with the ABA-inhibited IRT1 expression in the roots of Col-0 plants fed two different levels of iron. Furthermore, the Cd uptake of irt1 mutants was barely affected by ABA application. These results indicated that inhibition of IRT1 expression is involved in the decrease of Cd uptake in response to exogenous ABA application. Interestingly, ABA application increased the iron level in both Col-0 plants and irt1 mutants, suggesting that ABA-increased Fe acquisition does not depend on the IRT1 function, but on the contrary, the ABA-mediated inhibition of IRT1 expression may be due to the elevation of iron level in plants. From our results, we concluded that ABA application might increase iron acquisition, followed by the decrease in Cd uptake by inhibition of IRT1 activity. Thus, for crop production in Cd contaminated soils, developing techniques based on ABA application potentially is a promising approach for reducing Cd accumulation in edible organs in plants.
Highlights
Cadmium (Cd) is recognized as an important pollutant due to its high toxicity
The Cd uptake of irt1 mutants was barely affected by abscisic acid (ABA) application. These results indicated that inhibition of IRON-REGULATED TRANSPORTER 1 (IRT1) expression is involved in the decrease of Cd uptake in response to exogenous ABA application
Evidence presented in this study indicates that application of low-dose ABA decreases Cd levels in plants, which is associated with the inhibition of IRT1 activity in roots
Summary
Cadmium (Cd) is recognized as an important pollutant due to its high toxicity. In the human body, Cd adversely affects kidneys and bones (Ronald, 2000; Pan and Wang, 2012). The primary route of Cd entry into the human body is through crops grown in Cd-contaminated soil (Meharg et al, 2013). Many different strategies have been proposed for remediating Cd-contaminated soil to prevent Cd uptake by crops. These include the following: (1) “dig-and-dump” or encapsulation of the contaminated soil (Pulford and Watson, 2003; Khan et al, 2004); (2) chemical immobilization or extraction of Cd (Chen et al, 2000; Muehe et al, 2013); (3) phytoremediation by Cdhyperaccumulating plants (Marques et al, 2009; Gupta et al, 2013); (4) screening or breeding of crop genotypes with lower Cd accumulation (Liu et al, 2010; Meharg et al, 2013); and (5)
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