Arabidopsis casein kinase 1-like 8 enhances NaCI tolerance, early flowering, and the expression of flowering-related genes

Members of the casein kinase 1 (CK1) family are evolutionarily conserved eukaryotic protein kinases involved in various cellular, Physiological, and developmental processes in yeast. However, the biological roles of CK1 members in plants are poorly understood. Here, we report that an Arabidopsis CK1 member named casein kinase 1-like 8 (CKL8) was ubiquitously expressed in all plant organs, mainly in the stems of seedlings according to quantitative real-time PCR. Western blotting showed a remarkable exPression of the At0(1-8 gene in transgenic plants induced by high salinity. IA histochemical assay of AtCKL8 promoter:GUS expression revealed that the AtCKL8 promoter is very active in both seedlings and adult plants subjected to the salinity stress, while no GUS activity was detectable in all the transgenic plants grown under normal conditions. In a subcellular distribution analysis, the AtCKL8-GFP fusion protein was localized mainly in the cell membrane. AtCKL8-overexpressing transgenic plants showed an insensitivity to high salinity and an early flowering phenotype. Overall, these findings suggest that AtCKL8 plays a positive role in NaCI signaling and improves salt stress tolerance in transgenic Arabidopsis.