Water-saving cultivation practices, such as intermittent irrigation, are essential for sustainable rice production but often exacerbate grain cadmium (Cd) accumulation due to aerobic-soil-induced increases in Cd bioavailability. Uncoupling this trade-off is a critical challenge for global food safety. Here, we identify the transcription factor OsNAC4 as a key positive regulator of Cd uptake. Loss-of-function osnac4 mutants significantly reduce grain Cd accumulation by 30%-50% across diverse genetic backgrounds without compromising grain yield or agronomic traits. Mechanistically, we reveal that the drought/abscisic acid (ABA)-activated kinase OsSAPK2 interacts with and phosphorylates OsNAC4, thereby stabilizing the protein and enhancing its transcriptional activation of the Cd transporter gene OsNRAMP1. This signaling cascade establishes a direct molecular link whereby environmental water stress signaling cascades effectively "hijack" the basal Cd uptake machinery. Crucially, multi-location field trials demonstrate that osnac4 mutation effectively suppresses the aerobic-induced Cd elevation typically observed under water-saving regimes. Our findings elucidate the molecular mechanism underlying the conflict between water conservation and Cd accumulation, providing a robust genetic resource for breeding safe, climate-resilient rice varieties suitable for water-limited agriculture.
Xiao-Fang Zhu, Fangwei Yu, Changzhao Chen et al.· Current Biology· 0 citations
Cadmium (Cd) pollution in paddy soils threatens global food safety. Identifying molecular gateways controlling grain Cd accumulation is essential for breeding low-Cd rice. A field-based screen of a large-scale CRISPR/Cas9 mutant library identified OsGONST3, a Golgi nucleotide sugar transporter family member localized to the plasma membrane. After 1 μM Cd treatment for 7 d, OsGONST3 transcript abundance increased approximately 3.4-fold in root and 5.7-fold in shoot, accompanied by increased OsGONST3-GFP protein accumulation. Heterologous OsGONST3 expression increased yeast Cd content by approximately 23% relative to the empty-vector control. Under hydroponic exposure to 1 μM Cd for 7 d, two independent osgonst3 mutants contained 22-25% less Cd in root, approximately 13% less in shoot, and 16-21% less in xylem sap than Nipponbare. Conversely, OsGONST3-overexpressing lines contained 40-42%, 38-40%, and 28-37% more Cd in root, shoot, and xylem sap, respectively. Under tested field condition, OsGONST3 disruption reduced grain Cd by approximately 25-26% without a significant yield penalty and was associated with secondary transcriptional adjustments in Cd-homeostasis genes. These findings identify OsGONST3 as a plasma membrane-localized Cd influx-associated protein and a promising target for breeding low-Cd rice.
Jing Huang, Qiang Zhang, Fangwei Yu et al.· Journal of Hazardous Materia...· 0 citations
