Root Aeration Promotes Cadmium Accumulation in Rice by Regulating Iron Uptake-Associated System

Different cadmium (Cd)-accumulated rice genotypes (Erjiunan 1 and Fupin 36) were used to explore the effect of rice rhizosphere aeration on Cd uptake and accumulation. Aeration in the nutrient solution influenced the agronomic characteristics induced by Cd-stress, such as the increases of rice root length and root vigor, but the reductions of plant height and shoot dry weight. Aeration also alleviated the decreasing effects of Cd stress on antioxidant enzyme activities and soluble protein, malonaldehyde and nicotianamine contents in rice. Moreover, with aeration treatment, the accumulation and bioavailability of metal elements changed significantly, with a Cd increase and an Fe reduction in both rice genotypes. In addition, at the molecular level, aeration upregulated the expression of Fe-inducible genes (such as OsIRT1 , OsNRAMP1 , OsYSL15 and OsNAS3). Furthermore, as a Cd2+/Fe(2+)transporter, the high transcription level of OsNRAMP1 can elevate the Cd uptake and translocation in rice due to the Fe reduction caused by aeration and Cd-exposure, which indicated that OsNRAMP1 might play a crucial role in the effect of aeration on Cd uptake and accumulation.