miR156j-3p negatively regulates rice salt tolerance via ROS scavenging and ABA signaling

MicroRNAs (miRNAs) are crucial regulators of abiotic stress responses in plants. Among them, miR156 is a highly conserved miRNA family with two mature isoforms: miR156-5p and miR156-3p. While miR156-5p has been extensively studied for its functions in plant growth and stress responses, the roles of miR156-3p remain less explored. In this study, we illustrated that miR156j-3p negatively regulated rice salt tolerance by targeting OsRePRP1.2. Genetic evidence showed that miR156j-3p downregulation (STTM156j-3p) plants exhibited enhanced salt tolerance. Furthermore, OsRePRP1.2 was confirmed as a direct target of miR156j-3p via 5' RNA ligase-mediated rapid amplification of cDNA ends (5'-RLM-RACEs) assay in vivo and a rapid transient assay in tobacco. Consistently, OsRePRP1.2 positively regulated rice salt tolerance. Furthermore, both STTM156j-3p and OsRePRP1.2 overexpression (RePRP1.2-ox) plants showed enhanced hypersensitivity to exogenous ABA treatment. Besides, physiological assays revealed that the enhanced salt tolerance was associated with reduced accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), along with elevated antioxidant enzyme activities. Finally, we found that the genes involved in ABA signaling, ABA biosynthetic and ROS-scavenging system were up-regulated in STTM156j-3p and RePRP1.2-ox plants. Taken together, our findings strongly suggest that miR156j-3p targets OsRePRP1.2 and negatively regulates rice salt tolerance through the ROS scavenging and ABA signaling pathways.