Phytochrome and calcium stimulation of protein phosphorylation in isolated pea nuclei

The phosphorylation of several proteins in pea nuclei was promoted by Ca2+ and by red light. The red light-induced stimulation was reversed by far-red light, indicating that the photoreceptor modulating this response was the photochromic pigment, phytochrome. Both the red light and the Ca2+-promoted enhancement of phosphorylation were inhibited by the calcium chelator, ethylene glycol bis(beta-aminoethyl ether) N, N'-tetraacetic acid, and by the calmodulin inhibitors, chlorpromazine and compound 48/80.