Identification and Regulation of antiporters in Strawberry (Fragaria x ananassa) under salinity stress

Soil salinity is a major abiotic constraint that adversely affects plant growth and yield. The strawberry cultivar Sweet Charlie, previously reported as salt tolerant, was selected to evaluate physiological responses and to identify and characterize the differential regulation of antiporter genes under salinity stress. In total, ten antiporters were identified in cultivated strawberry, belonging to six gene families. The SOS (Salt Overly Sensitive) family comprised three members (FaSOS1.1, FaSOS1.2, and FaSOS1.3), while SOS2, SOS3, SOS4, and SOS5 were each represented by a single gene (FaSOS2, FaSOS3, FaSOS4, and FaSOS5). The NHX (cation/H⁺ exchanger) family included three members (FaNHX1.1, FaNHX1.2, and FaNHX2). The cultivar Sweet Charlie exhibited a high level of salt tolerance, with an LT₅₀ corresponding to 85 mM NaCl after 7 days of stress exposure. Physiological adaptations such as maintenance of leaf area, preservation of relative water content through stomatal regulation, osmotic adjustment, and sustained chlorophyll levels contributed to mitigating the detrimental effects of short-term salinity stress. At the molecular level, increased expression of FaSOS1.2 and FaSOS3 in roots, along with FaNHX1.2 in both roots and shoots, suggests their involvement in alleviating salt-induced toxicity. Short-term salinity stress also induced cellular damage, as evidenced by enhanced reactive oxygen species (ROS) accumulation, elevated malondialdehyde (MDA) levels, and increased electrolyte leakage. Future work will focus on the overexpression of selected upregulated antiporters (FaSOS1, FaSOS3, and FaNHX1.2) in Arabidopsis thaliana to further elucidate their functional roles in salinity tolerance.