Various signaling pathways rely on changes in cytosolic calcium ion concentration ([Ca²⁺]_i). In plants, resting [Ca²⁺]_i oscillates diurnally. We show that in Arabidopsis thaliana, [Ca²⁺]_i oscillations are synchronized to extracellular Ca²⁺ concentration ([Ca²⁺]_o) oscillations largely through the Ca²⁺-sensing receptor CAS. CAS regulates concentrations of inositol 1,4,5-trisphosphate (IP₃), whichinturndirects release of Ca²⁺ from internal stores. The oscillating amplitudes of [Ca²⁺]_o and [Ca²⁺]_i are controlled by soil Ca²⁺ concentrations and transpiration rates. The phase and period of oscillations are likely determined by stomatal conductance. Thus, the internal concentration of Ca²⁺ in plant cells is constantly being actively revised.

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Selected media links: Duke News 3/8/07