The involvement of calmodulin and protein kinases in the upstream of cytosolic and nucleic calcium signaling induced by hypoosmotic shock in tobacco cells.

Changes in Ca concentrations in cytosol ([Ca]) or nucleus ([Ca]) may play some vital roles in plants under hypoosmotic shock (Hypo-OS). Here, we observed that Hypo-OS induces biphasic increases in [Ca] and [Ca] in two tobacco cell lines (BY-2) expressing apoaequorin either in the cytosol or in the nucleus. Both [Ca] and [Ca] were sensitively modulated by the inhibitors of calmodulin and protein kinases, supporting the view that calmodulin suppresses the 1 peaks and and protein kinases enhance 2 peaks in [Ca] and [Ca]. Data also suggested that the 1 and 2 events depend on the internal and extracellular Ca sources, respectively.