An OsWRKY1-OsPht1;4 Regulatory Module Restricts Arsenic Uptake and Accumulation in Rice Grain

Arsenic (As) contamination in paddy soils poses a threat to human health through rice consumption. Arsenate (AsV) uptake contributes to grain As accumulation, yet its upstream regulatory mechanisms remain largely unknown. Here, we identified a WRKY transcription factor, OsWRKY1, as a key regulator of AsV uptake in rice plant, whose expression is strongly induced by AsV at both transcript and protein levels. Loss of OsWRKY1 function increased rice root As concentration by 2.8-fold under hydroponic conditions and raised grain As concentration by 19-22% in soil-grown plants compared with wild type, indicating that OsWRKY1 is a negative regulator of As accumulation. Chromatin immunoprecipitation sequencing revealed that OsWRKY1 directly binds to the promoter of P-transporter OsPht1;4, an also major AsV transporter gene in rice, but not to other Pht1 family members. Dual-luciferase assays further showed that OsWRKY1 represses OsPht1;4 promoter activity. Under AsV exposure, OsPht1;4 transcript levels were upregulated by 2.5-fold in oswrky1 mutants and were downregulated by 90% compared with wild type in OsWRKY1-overexpressing lines. These results define the OsWRKY1-OsPht1;4 module as a critical transcriptional repression mechanism that limits AsV uptake and accumulation in rice grain, providing a mechanistic basis for restricting As accumulation through specific transcriptional regulation of AsV uptake.