Implication of Universal Messengers in Phytochrome-mediated
Control of Ca²⁺ Uptake by Protoplasts

S. G. Sokolovsky, O. V. Yatsevich, and I. D. Volotovski

Institute of Photobiology, Belarussian Academy of Sciences, ul. F. Skorina 27, Minsk, 220072 Belarus

Received June 15, 1995

Abstract—Effects of cyclic mononucleotides (dibutiryl cAMP, dibutiryl cGMP), phorbol myristic acid (phor-
bol 12-myristate 13-acetate, an analog of diacylglycerol), and the calmodulin antagonist R24571 on the phyto-
chrome-regulated accumulation of Ca²⁺ by oat (Avena sativa L.) protoplasts were studied. All the compounds
tested, except for dibutiryl cAMP, caused a dose-dependent stimulation of Ca²⁺ uptake by darkened protoplasts,
mimicking the effect of red light. It is argued that the aforementioned compounds attack a variety of specific
intracellular targets, protein kinases in particular. The results suggest that the phytochrome-mediated signal
transduction, which leads to Ca²⁺ accumulation in plant cells, may involve at least three of the aforementioned
messengers (cGMP, calmodulin, and diacylglycerol).

Key words: Avena sativa - protoplasts - phytochrome - Ca²⁺ accumulation - cyclic mononucleotides - phorbol
12-myristate 13-acetate - calmodulin inhibitor

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