Versatile casein kinase 1: multiple locations and functions.

Members of casein kinase 1 (CK1) are evolutionarily conserved eukaryotic protein kinases, which play fundamental roles in various cellular, physiological and developmental processes. One of the key mechanisms by which the activity of these multifunctional CK1 members is controlled appears to be their specific spatiotemporal compartmentalization within the cell. Plant genomes encode dozens of CK1 homologs, the function of which are not yet well characterized, however, evolutionary conservation of these genes predicts their fundamental roles in plants. Characterization of Arabidopsis CK1-like 6 (CKL6) that we have recently reported sheds new light on the existence of parallel and unique aspects of the mechanism involved in specific subcellular targeting as well as cellular function of CK1 in plants. In this addendum, I will focus my discussion on the versatility of CKL6 partitioning at different subcellular compartments and propose that this capability likely reflects its multiple functions in modulating an array of cellular targets.