LIGHT INDUCES RAPID CHANGES OF THE PHOSPHORYLATION PATTERN IN THE CYTOSOL OF EVACUOLATED PARSLEY PROTOPLASTS

The fractionation of cells of a parsley suspension culture [Petroselin um crispum (Mill.) A. Hill] by protoplasting and subsequent removal of the vacuoles led to physiologically intact evacuolated protoplasts re taining light inducibility of chalcone synthase expression. Lysis of t he evacuolated protoplasts permitted the isolation of a pure, highly c oncentrated cytosolic fraction containing major cytosolic membranes bu t only minor contamination by proplastids, mitochondria, and nuclei. S hort-time irradiations of the cytosol with red or UV-containing white light resulted in very fast changes of the phosphorylation pattern of 18-, 40-, 48-, 55- to 70-, and 120-kDa proteins. Major differences wer e observed between the phosphorylation patterns obtained by red or UV- containing white light treatment, indicating a different primary actio n of the excited photoreceptors in vitro. Separation of the microsomal fraction from the cytosolic matrix established the localization of th ese proteins. Chase and photoreversibility experiments revealed that p hytochrome in vitro regulates the phosphorylation of the 40-kDa protei n by modifying a soluble cytosolic kinase/phosphatase system.