Calcium signaling in plants

Changes in the cytosolic concentration of calcium ions ([Ca2+](i)) play a key second messenger role in signal transduction. These changes are visualized by making use of either Ca2+-sensitive fluorescent dyes or the Ca2+-sensitive photoprotein, aequorin. Here we describe the advances made over the last 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 understanding of cell signaling in plants. The next challenge will be to establish how the Ca2+ signals are encrypted and decoded in order to provide specificity, and we discuss the current understanding of how this may be achieved.