Abstract
By ponding water release from the paddy field, soil becomes aerobic and Cd changes to the soluble form such as CdSO4. The solubility of Fe in the rhizosphere is opposite to that of Cd. The oxidative soil conditions induces Fe-deficiency signals in a rice plant body, which results in the induction of various Fe-deficiency inducible genes. In addition to Strategy-II Fe acquisition system, rice plant also has Fe2+-transporters, which are components of Strategy-I system. We have previously isolated Fe2+ transporter genes, OsIRT1 and OsIRT2, from rice. We hypothesized that Cd could be taken up and transported through the Fe uptake and transport system induced by Fe shortage in rice plant. Hydroponically cultured Fe-deficient rice absorbed more Cd than Fe-sufficient rice and co-existence of Fe enhanced translocation of Cd to shoots. Yeast mutants expressing OsIRT1 and OsIRT2 became more sensitive to Cd, suggesting that Cd was absorbed by OsIRT1 and OsIRT2.
