ShPP2C.F2-1 from sugarcane enhances salt tolerance in rice through modulation of ROS detoxification and ion homeostasis

Protein phosphatase 2Cs (PP2Cs) are key regulators of plant growth, hormone signaling, and abiotic stress responses. However, systematic characterization of the PP2C gene family in sugarcane (Saccharum spp. hybrids) remains limited. In this study, 536 PP2C genes (ShPP2Cs) were identified from the sugarcane cultivar Xintaitang 22 (XTT22) and classified into 12 phylogenetic subgroups, with closely related members exhibiting similar gene structures and conserved motifs. A full-length cDNA of ShPP2C.F2–1 was cloned and functionally characterized. Subcellular localization showed that ShPP2C.F2–1 is distributed in the nucleus and plasma membrane, and its expression was strongly induced by NaCl treatment. Heterologous expression in yeast demonstrated that ShPP2C.F2–1 significantly enhanced salt tolerance. Furthermore, transgenic rice plants overexpressing ShPP2C.F2–1 exhibited improved survival rates and growth performance under salt stress. Physiological analyses revealed significantly increased peroxidase (POD) activity, accompanied by reduced accumulation of malondialdehyde (MDA) and H₂O₂ in transgenic lines. In contrast, superoxide dismutase (SOD) and catalase (CAT) activities were lower in transgenic lines than in wild-type plants under salt stress and recovery conditions, suggesting that ShPP2C.F2–1 promotes a POD-dominant rather than a broadly activated SOD–CAT–POD antioxidant response. Consistently, expression of the peroxidase gene OsPRX109 was markedly upregulated. Moreover, transgenic lines exhibited reduced Na⁺ accumulation and lower Na⁺/K⁺ ratios under salt stress. Several salt-responsive genes, including OsDST, OsEREBP1, OsMYB2, OsNHX1, OsSOS1, and OsHKT1;1, were also significantly regulated in transgenic rice. Transcriptome analysis further indicated that ShPP2C.F2–1 enhances salt tolerance primarily through a peroxidase-centered reactive oxygen species (ROS) scavenging system, together with associated regulation of stress-responsive and ion transport-related pathways. Collectively, these findings demonstrate that ShPP2C.F2–1 positively regulates salt stress tolerance mainly via a POD-dominant ROS detoxification mechanism and coordinated Na⁺ homeostasis, providing valuable insights into PP2C-mediated stress adaptation and offering a potential target for improving salinity tolerance in crops.