The prenylation status of a novel plant calmodulin directs plasma membrane or nuclear localization of the protein

Post‐translational attachment of isoprenyl groups to conserved cysteine residues at the C‐terminus of a number of regulatory proteins is important for their function and subcellular localization. We have identified a novel calmodulin, CaM53, with an extended C‐terminal basic domain and a CTIL CaaX‐box motif which are required for efficient prenylation of the protein in vitro and in vivo . Ectopic expression of wild‐type CaM53 or a non‐prenylated mutant protein in plants causes distinct morphological changes. Prenylated CaM53 associates with the plasma membrane, but the non‐prenylated mutant protein localizes to the nucleus, indicating a dual role for the C‐terminal domain. The subcellular localization of CaM53 can be altered by a block in isoprenoid biosynthesis or sugar depletion, suggesting that CaM53 activates different targets in response to metabolic changes. Thus, prenylation of CaM53 appears to be a novel mechanism by which plant cells can coordinate Ca 2+ signaling with changes in metabolic activities.