Calcium signaling in plants

Changes in the cytosolic concentration of calcium ions ([Ca2+](i)) play a k ey second messenger role in signal transduction. These changes are visualiz ed by making use of either Ca2+-sensitive fluorescent dyes or the Ca2+-sens itive photoprotein, aequorin. Here we describe the advances made over the l ast 10 years or so, which have conclusively demonstrated a second messenger role for [Ca2+](i) in a few model plant systems. Characteristic changes in [Ca2+](i) have been seen to precede the responses of plant cells and whole plants to physiological stimuli. This has had a major impact on our unders tanding of cell signaling in plants. The next challenge will be to establis h how the Ca2+ signals are encrypted and decoded in order to provide specif icity, and we discuss the current understanding of how this may be achieved .