The mutation in the critical sterility-inducing temperature-regulating gene OsTMS5 and OsCSIT1 enhances cadmium tolerance in rice seedlings

Cadmium (Cd) contamination in farmland poses a threat to food security and human health. This study explores the role of the OsCSIT1 gene in Cd tolerance in rice, using an EMS-mutagenized Ostms5/Oscsit1 double mutant (st1). The st1 mutant exhibited enhanced Cd resistance, with reduced root growth inhibition under 5 μM CdCl2 treatment compared to the Ostms5 parent line (1892S). Gene expression analysis revealed downregulation of Cd uptake genes (OsNRAMP5, OsCd1) and the transporter OsHMA2, alongside upregulation of detoxification genes (OsABCG36, OsZIP1, OsMTP1) in st1 under Cd stress. These changes correlated with 36% lower Cd accumulation in stems. The findings suggest that OsCSIT1 mutation may alter metal homeostasis by modulating transporter activity, limiting Cd uptake and enhancing vacuolar sequestration. The dual functionality of OsCSIT1—regulating both thermosensitive sterility and Cd tolerance—highlights its potential for developing hybrid rice varieties with reduced grain Cd accumulation. The study provides critical insights into developing climate-resilient, low-Cd rice varieties to address food safety challenges in Cd-contaminated environments.