OsWRKY18, a WRKY transcription factor, is involved in rice salt tolerance.

Abstract

Salinity stress significantly impairs plant growth and leads to substantial yield losses in rice and other crops. WRKY transcription factors (TFs) are well-documented regulators of plant stress responses, yet their specific roles in rice salt tolerance remain largely unexplored. This study investigates the function of OsWRKY18, a rice WRKY TF with transcriptional activation activity, in salt stress adaptation. Bioinformatics analysis revealed that OsWRKY18 contains conserved motifs and domains shared with other salt-tolerant WRKY TFs, indicating its potential involvement in stress response. Expression analysis showed that OsWRKY18 is predominantly expressed in roots, with significant upregulation under salt stress. Subcellular localization in rice protoplasts revealed that OsWRKY18 is primarily localized in the nucleus. Immunostaining assays confirmed its widespread expression in root tissues, particularly in the stele, but not in epidermal cells. Using CRISPR/Cas9, we generated Oswrky18 knockout mutants, which displayed increased salt sensitivity, marked by elevated Na+ accumulation in shoots and stunted growth compared to wild-type plants. Transcriptome sequencing and quantitative real-time PCR analysis revealed that OsWRKY18 regulates key genes involved in ABA signaling, osmotic adjustment, and ion homeostasis, including OsHOX22, OsSALP1, OsNHX4, and OsHKT1;5. Yeast one-hybrid assays further confirmed the direct binding of OsWRKY18 to the OsHKT1;5 promoter. These results highlight OsWRKY18's critical role in enhancing rice salt tolerance by maintaining ion balance and activating stress-responsive gene networks. This study advances our understanding of the molecular mechanisms underlying OsWRKY18-mediated salt-stress responses and the functional roles of WRKY TFs in rice.