Overexpression of PvWAK3 from seashore paspalum increases salt tolerance in transgenic Arabidopsis via maintenance of ion and ROS homeostasis

Seashore paspalum (Paspalum vaginatum O. Swartz) is an important warm-season turfgrass species with extreme salt tolerance, but investigations on its salt tolerance mechanism are limited. A salt induced PvWAK3 from halophyte seashore paspalum was identified in this study. Overexpression of PvWAK3 in Arabidopsis led to increased salt tolerance. Transgenic plants had higher levels of seed germination rate, root length, number of lateral roots, shoot weight, survival rate, F-v/F-m, ETR, and NPQ compared with the wild type (WT) under salt stress. Na+ content was increased and K+ content was decreased after salinity treatment, with lower levels of Na+ and Na+/K+ ratio but higher level of K+ in transgenic plants than in WT under salt stress. The improved maintenance of Na+ and K+ homeostasis was associated with the higher transcript levels of K + -Uptake Permease 4 (KUP4), Potassium Transport 2/3 (AKT2), Salt Overly Sensitive 1 (SOS1) and High-Affinity K + Transporter 5 (HAK5) in transgenic plants compared with WT. Superoxide dismutase (SOD), catalase (CAT) and ascorbate-peroxidase (APX) activities, proline concentration, and P5CS1 transcript were increased after salinity treatment, with higher levels in transgenic lines compared with WT, which led to reduced accumulation of O-2 center dot(-) and H2O2 under salt stress. It is suggested that PvWAK3 regulates salt tolerance positively, which is associated with promoted Na+ and K+ homeostasis, activated antioxidant enzymes, and proline biosynthesis under salt stress.