Isolation and characterization of a rice line with high Cd accumulation for potential use in phytoremediation

Aims: To reduce cadmium (Cd) intake, remediation of Cd-contaminated soil and breeding crops with low Cd accumulation are important. This study aims to isolate rice mutants with altered accumulation of Cd. Methods: We used rice seeds mutated by N-methyl-N-nitrosourea for screening. The mutant was physiologically, genetically, and molecularly characterized. Cd accumulation was compared among five rice varieties cultivated in a Cd-contaminated soil. Results: From 1000 lines screened, we isolated a line (TCM213) with high Cd accumulation. There was no difference in the root Cd uptake, but a higher root-to-shoot translocation of Cd was found in TCM213 compared with a common rice cultivar, T-65. The expression and sequence of OsNramp5 and OsHMA2 did not differ between TCM213 and T-65. However, several SNPs and deletion were found in the sequence of OsHMA3, although its expression and tissue localization were similar to those of T-65. Genetic analysis of an F₂ population derived from T-65 and TCM213 showed that the variation of OsHMA3 explained 72 % of variation in total Cd accumulation. TCM213 accumulated the largest Cd amount in the shoots among five Cd-accumulating varieties. Conclusions: High Cd accumulation in TCM213 results from loss of function of OsHMA3, and its high Cd accumulation has potential for efficient phytoremediation of Cd-contaminated soil.