Intracellular protein phosphorylation in oat (Avena sativa L.) protoplasts by phytochrome action. 1. Measurement of action spectra for the protein phosphorylation.

The effects of red light and wavelength dependency of the protein phosphorylation in oat protoplasts were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. Red light (660 nm) irradiation of the protoplasts increased the phosphorylation of 15 different proteins, and the phosphorylation of 2 proteins (27 KDa, 32 KDa) out of 15 were observed to be dependent on the wavelength of the irradiating light. The phosphorylation densities of these two proteins increased up to two or three hundred percent during a three-minute period of irradiation. The phosphorylation of these two proteins revealed a red/far-red photoreversibility of phytochrome. When a calcium ion chelator (2 mM EGTA) was added into the cell suspension, the phosphorylations of all the proteins were reduced about 200%. These findings suggest that phytochrome action and Ca2+ influx are certainly involved in the in vivo phosphorylation of proteins in oat protoplasts.