Dual Repression by IPA1 Fine‐Tunes OsbZIP79‐Mediated Salt Tolerance in Rice

Soil salinity severely impairs rice yield and quality, yet the molecular mechanisms of its salt tolerance remain unclear. In this study, we first discovered OsbZIP79, a novel basic leucine zipper (bZIP)-type transcription factor, as a positive regulator of salt tolerance in rice. We uncovered that OsbZIP79 positively regulates the expression of OsHAK26 (encoding a potassium transporter) and OsMPG1 (encoding a mannose-1-phosphate guanylyltransferase) to confer salt tolerance in rice. In vivo and in vitro evidence demonstrate that OsbZIP79 physically interacts with Ideal Plant Architecture1 (IPA1), a known negative regulator of salt stress responses. IPA1 represses the expression of OsbZIP79 and competes with the OsbZIP79 C-terminus for binding to the promoters of its target genes. Haplotype analysis of 4726 rice accessions identified Hap3 of OsbZIP79 as a favorable allele that confers significantly enhanced salinity tolerance compared to Hap1 and Hap2. These findings reveal a novel salt tolerance regulatory network governed by the OsbZIP79-IPA1 module. This work provides insights to facilitate the improvement of salt tolerance in rice through advanced breeding.