Decoding Ca2+ signals in plants

Different input signals create their own characteristic Ca2+ fingerprints.These fingerprints are distinguished by frequency, amplitude, duration, and number of Ca2+ oscillations. Ca2+-binding proteins and protein kineses decode these complex Ca2+ finger-prints through conformational coupling and covalent modifications of proteins. This decoding of signals can lead to a physiological response with or without changes in gene expression. In plants, Ca2+-dependent protein kinases and Ca2 +lcalmodulin-dependent protein kinases are involved in decoding Ca2+ signals into phosphorylation signals. This review summarizes the elements of conformational coupling and molecular mechanisms of regulation of the two groups of protein kinases by Cap2+ and Ca2+/calmodulin in plants.