Integrated cellular, physiological, and transcriptomic analyses reveal the synergistic effects of boron and silicon in alleviating antimony toxicity in rice (Oryza sativa L.)

Antimony (Sb) contamination poses a serious threat to rice productivity and crop safety. While boron (B) and silicon (Si) individually alleviate heavy metal stress, their synergistic effects in alleviating Sb toxicity remain underexplored. In this study, we employed a dual-application strategy-foliar-applied B and root-supplied Si-to investigate their individual and combined roles in enhancing Sb tolerance in rice. High level of Sb exposure (100 μM) impaired plant growth, disrupted chlorophyll biosynthesis, elevated reactive oxygen species (ROS) accumulation, and damaged membrane integrity. Although B or Si alone provided partial protection, their co-application significantly improved growth, reduced Sb uptake and translocation, and enhanced antioxidant capacity and cell viability. Transcriptomic analysis demonstrated that B + Si co-treatment upregulated photosynthesis-related genes (Lhcb, Psb, Psa) while downregulating genes involved in phenylpropanoid biosynthesis (PAL, PTAL, HCT, CSE, F5H) and hormone signaling pathways (AUX/IAA, PP2C, JAZ, NPR1). These transcriptional changes alleviated stress-induced overactivation of defense metabolism, thereby conserving energy for growth and resilience. Our findings highlight the synergistic potential of B and Si in mitigating Sb phytotoxicity and propose an efficient, sustainable strategy for improving rice productivity in Sb-contaminated soils.