Calcium signalling: linking environmental signals to cellular functions

Topics discussed in this review include Ca in signal-response coupling and the specificity of Ca2+ signals. It is concluded that Ca is the most important signalling molecule in plants. The source of Ca and the type of cell responding to a particular signal confers specificity at the primary level. At other levels, specificity is achieved by the strength of the Ca signal and the specific patterns of Ca change. Another level of control is achieved by changes in activity of various other proteins and factors that become activated or modulated by changes in Ca levels. Ca-dependent kinases and phosphatases belong to this category and are main components of signal response coupling. Changes in the level of other factors in concert with Ca also activate a specific set of proteins, and this could also be involved in contribution to the specificity of signalling. Ca directly affecting the expression of certain genes gives another level of control on specificity. Other components in the regulation of Ca signalling are also discussed