Figure 1.

Time course of calcium-dependent kinase activity from soluble and membrane fractions from cold-treated rice plants. Rice plants were grown at 27°C for 2 weeks and then either kept at 27°C (control plants) or shifted to 12°C (cold-treated plants). Shoots were harvested at different periods of time and soluble and membrane fractions were prepared. The kinase activity was assayed using syntide-2 as substrate (see “Materials and Methods”) in soluble (A) and membrane (B) fractions. C, Phosphorylation of endogenous proteins present in membranes prepared from control and cold-treated plants. The intensity of the bands was quantified using the TN Image software (version 2.13, T.J. Nelson, Rockville, MD). The experiment was repeated four times with similar results.