OsbZIP35 Interacts with OsSAPK3 and Enhances Drought Stress Tolerance and Yield in Rice

OsbZIP35 is a member of the B subfamily of bZIP transcription factors in rice ( Oryza sativa L.). The function of OsbZIP35 has not been reported previously. In this study, drought, H ₂ O ₂ , abscisic acid, and NaCl treatments strongly induced the expression of OsbZIP35 , whereas treatment with gibberellin, indoleacetic acid, and jasmonic acid did not affect OsbZIP35 expression. We used the CRISPR/Cas9 gene-editing technology to construct OsbZIP35 knockout mutants ( bzip35-1 and bzip35-2 ) and evaluated the function of OsbZIP35 . The results showed that, compared with the wild type, the bzip35 mutants were more sensitive to drought stress during the germination, post-germination growth, and seedling stages. Specifically, the bzip35 mutants exhibited a lower germination percentage, a weaker growth phenotype, and an increase in reactive oxygen species accumulation. Further analysis indicated that, under drought stress, OsbZIP35 regulated reactive oxygen species accumulation by modulating the contents of antioxidants, thereby positively regulating the response of rice seedlings to drought stress. In addition, we observed that OsbZIP35 could be phosphorylated by OsSAPK3 and participated in the abscisic acid signaling pathway in response to drought stress. Agronomic trait analysis revealed that, under drought stress at the heading stage, the panicle length and seed-set rate of bzip35 mutants were significantly lower than those of the wild type. This study examined the role of OsbZIP35 in rice stress tolerance and yield regulation, and identified an upstream regulatory gene, OsSAPK3 . The results provide novel information on the mechanisms of stress tolerance and yield regulation in rice.