OsbZIP60 Positively Regulates Salt-Stress Tolerance in Rice

Soil salinity is a major abiotic stress limiting rice growth and grain productivity worldwide. Basic leucine zipper (bZIP) transcription factors serve as central regulators of plant environmental stress responses, yet the biological function and molecular regulatory mechanism of rice OsbZIP60 (LOC_Os07g44950) underlying salinity tolerance remain largely uncharacterized. In this study, we systematically characterized the salt-stress regulatory function of OsbZIP60 in rice. Tissue expression profiling revealed that OsbZIP60 was ubiquitously transcribed across all examined rice tissues, and its encoded protein predominantly localizes to the cell nucleus. Transcript abundance of OsbZIP60 was significantly induced by salt, the osmotic phase, abscisic acid (ABA), and oxidative stress signals. Phenotypic assays demonstrated that overexpression of OsbZIP60 substantially enhanced rice salt tolerance, whereas the bzip60 knockout mutant exhibited aggravated salt hypersensitivity. Physiological quantification revealed that OsbZIP60 promoted the accumulation of osmoprotectants, alleviated salt-triggered oxidative damage, and elevated the activities of core antioxidant enzymes under saline conditions. Moreover, OsbZIP60 maintained intracellular Na⁺/K⁺ homeostasis and positively modulated the transcript levels of a series of salt-responsive downstream genes. Collectively, our results demonstrate that OsbZIP60 acts as a positive regulatory hub that coordinates osmotic adjustment, antioxidant defense, and ion balance to confer salt tolerance in rice, providing a promising genetic target for molecular breeding of salt-tolerant rice varieties.