Abstract
Previously, we reported that OsNRAMP5 functions as a manganese, iron, and cadmium (Cd) transporter. The shoot Cd content in OsNRAMP5 RNAi plants was higher than that in wild-type (WT) plants, whereas the total Cd content (roots plus shoots) was lower. For efficient Cd phytoremediation, we produced OsNRAMP5 RNAi plants using the natural high Cd-accumulating cultivar Anjana Dhan (A5i). Using a positron-emitting tracer imaging system, we assessed the time-course of Cd absorption and accumulation in A5i plants. Enhanced 107Cd translocation from the roots to the shoots was observed in A5i plants. To evaluate the phytoremediation capability of A5i plants, we performed a field experiment in a Cd-contaminated paddy field. The biomass of the A5i plants was unchanged by the suppression of OsNRAMP5 expression; the A5i plants accumulated twice as much Cd in their shoots as WT plants. Thus, A5i plants could be used for rapid Cd extraction and the efficient phytoremediation of Cd from paddy fields, leading to safer food production.
Highlights
Cadmium (Cd) is a toxic heavy metal that causes serious health problems in humans
We showed that OsNRAMP5 functions as a Cd, Fe, and Mn transporter in rice [29,42]
OsNRAMP5 is expressed mainly in roots, and the protein is localized to the plasma membrane [29]
Summary
Cadmium (Cd) is a toxic heavy metal that causes serious health problems in humans. Cd, which was a well-known cause of ‘itaiitai’ in Japan in the past, was recently classified as a human carcinogen by the International Agency for Research on Cancer [1]. Cd accumulates in the human body through food, and the main source of dietary Cd intake among Asians is rice [2,3,4]. Reducing the Cd level in paddy field soil is necessary to ensure food safety. Phytoremediation is an effective method for removing various soil contaminants using plants. There is significant genotypic variation in the Cd levels of rice grains and shoots [8,9,10]; this said, the cultivar Anjana Dhan naturally accumulates more Cd in its grains and shoots than any other cultivar in the world [10]. Phytoremediation using high Cd-accumulating cultivars successfully reduced the total soil Cd content and subsequent grain Cd content [11,12]
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