Enhanced Tolerance to Low-K+ Stress in Tobacco Plants, that Ectopically Express the CBL-interacting Protein Kinase CIPK23 Gene

Tobacco (Nicotiana tabacum) has a relatively high requirement for potassium (K+). However, the molecular basis of tolerance to low-K+ stresses in tobacco still remains unknown. Here, we report the role of a member of the A. thaliana CBL (calcineurin B-like) interacting protein kinase (CIPK) family, AtCIPK23, in low-K+ stress responses in tobacco. Molecular analyses revealed that the AtCIPK23 gene was successfully transferred into a tobacco cultivar K326 via Agrobacterium tumefaciens-mediated transformation. Overexpression of AtCIPK23 in tobacco resulted in increased low-K+ tolerance, which was demonstrated by higher dry biomass, longer primary root length, higher K+ content and better growth status of transgenic tobacco plants compared to controls when both were treated in low-K+ MS medium and low-K+ hydroponics. Moreover, transgenic lines conferred tolerance to low-K+ stress by increasing the K+ uptake rate under low-K+ conditions. Taken together, these results provide evidence that AtCIPK23 may be involved in the CBL-CIPK signalling network in tobacco responses to low-K+ stress.