Silicon Enhances Rice Tolerance to Drought and Blast Disease Through Modulating ROS Accumulation and Stress-Related Genes

Silicon (Si) serves as a beneficial element that enhances plant resistance to both abiotic and biotic stresses. Although its positive effects have been widely investigated, the molecular mechanisms by which silicon improves stress tolerance in rice (<i>Oryza sativa</i> L.) remain unclear. Here, we show that Si displayed an optimal improved effect at concentrations of 2-4 mM in hydroponic system, and Si enhanced rice tolerance to drought and blast disease by maintaining reactive oxygen species (ROS) homeostasis and reducing root cell damage. In addition, Si at 4 mM upregulated the ABA biosynthesis gene <i>OsNCED3</i>, stress- and ABA-responsive genes <i>OsDREB2A</i> and <i>OsLEA5</i>, as well as the catalase gene <i>OsCatB</i>, while suppressing the drought-responsive negative regulator <i>OsWRKY5</i>, thereby enhancing drought tolerance through an ABA-dependent signaling pathway. Si at 4 mM enhanced resistance to rice blast by activating defense-related genes <i>OsPBZ1</i>, <i>OsPR10a</i>, <i>OsPR5</i> and <i>OsWRKY45</i> while simultaneously boosting ROS-scavenging capacity. Collectively, our results demonstrate that Si enhances rice tolerance to drought and blast disease through the coordinated modulation of ABA signaling, ROS homeostasis, and stress-related gene expression.