Heterologous expression of Sesuvium portulacastrum SpCIPK2 confers salt tolerance in transgenic Arabidopsis thaliana

Calcineurin B-like interacting protein kinases (CIPKs) play critical roles in plant adaptation to salt stress. However, the biological functions of CIPKs in Sesuvium portulacastrum, a halophyte flourishing in coastal mudflats, remain poorly understood. Here, a highly expressed CIPK gene, SpCIPK2, was identified from transcriptomic analyses of S. portulacastrum root systems under salt stress. Subcellular localization assays confirmed the cytoplasmic presence of SpCIPK2. Arabidopsis thaliana plants overexpressing SpCIPK2 exhibited markedly improved salt tolerance, characterized by increased fresh weight under salt stress. Transgenic plants demonstrated significantly lower levels of O2<middle dot>- and H2O2 compared to wild-type plants. Furthermore, transgenic plants revealed a reduced relative conductivity and enhanced peroxidase (POD) activity in the leaves. Salt treatment accelerated Na+ efflux while slowing K+ efflux in transgenic plants, resulting in diminished Na+ accumulation and an elevated K+/Na+ ratio during salt stress. This evidence suggests that SpCIPK2 enhances salt tolerance by regulating ion homeostasis, activating antioxidant enzymes activity, and scavenging reactive oxygen species (ROS) in salt-stressed plants.