Overexpression of SeTIP2;3 and SePIP1;4 from Salicornia europaea Enhances Drought Tolerance in Arabidopsis

Aquaporins (AQPs) are key channels for water and small molecule transport across membranes, and represent early targets of stress signaling pathways in plants. Salicornia europaea is a typical halophyte adapted to saline-alkaline and nutrient-poor soils. However, studies on AQPs from S. europaea and their precise roles in abiotic stress responses remain limited. In this study, SeTIP2;3 and SePIP1;4 were cloned from S. europaea. Bioinformatics analysis confirmed that they belong to the TIP and PIP subfamilies of AQPs, respectively. Subcellular localization analysis revealed that SeTIP2;3 and SePIP1;4 were localized to the tonoplast and plasma membrane, respectively. Under polyethylene glycol (PEG) treatment, SeTIP2;3 showed increased transcription levels in the roots, and SePIP1;4 showed varied degrees of increased transcription in both roots and shoots. Heterologous expression of both genes in Arabidopsis thaliana was performed to investigate their functions. Under germination assays, the overexpression (OE) lines exhibited faster germination rates and longer primary roots (1.2–1.4 cm) compared to the wild-type (WT) plants (1.2 cm). Under mannitol-simulated drought stress, the transgenic lines showed reduced MDA content (23.8–28.7 nmol/g), increased accumulation of proline (2.5–3.8 mg/g) and soluble sugars (39.4–49.3 mg/g), and higher chlorophyll content (0.7–0.9 mg/g) than WT plants (30.9 nmol/g; 2.4 mg/g; 30.6 mg/g; 0.7 mg/g). Furthermore, under natural drought conditions, the OE lines displayed lower water loss rates and higher survival rates. Collectively, the findings of this study provide a theoretical basis for the potential application of Salicornia aquaporins in enhancing drought tolerance.