Overexpression of stress-associated protein 2 (CdSAP2) from Cynodon dactylon enhances salt tolerance

Excess salt reduces soil fertility and limits plant growth and development. Enhancing salt tolerance is crucial for improving land utilization and crop yield. Bermudagrass (Cynodon dactylon) is a widely cultivated warm-season turfgrass worldwide, with high tolerance to heat, drought, and salinity stresses. In the present study, a stress-associated protein 2 (CdSAP2) was cloned from bermudagrass. The domain analysis showed that CdSAP2 had A20 and AN1 zinc-finger domains. Expression pattern analysis revealed that the transcript level of CdSAP2 in leaves was significantly induced by abscisic acid, drought, NaCl, and cold treatments. CdSAP2 overexpression significantly enhanced salt tolerance in Arabidopsis, as manifested by significantly increased germination rate, higher chlorophyll content, photochemical efficiency, and net photosynthetic rate, higher contents of osmotic regulatory substances (proline and soluble sugar), but lower leaf scorch rate, lower electrolyte leakage, lower Na⁺/K⁺ ratio, and lower reactive oxygen species accumulation under salt stress. RT-qPCR analysis showed that improved salt stress tolerance by CdSAP2 overexpression might be related to upregulated expression of genes involved in ionic translocation (SOS1, NHX1), antioxidant defense (APX, SOD, POD), and osmotic adjustment (BADH and P5CS).