Abstract
In green maize (Zea mays L.) leaves, a dependence of the activity of fumarate hydratase (FH) on light conditions was revealed. It was established that the phytochrome system is involved in the photo-regulation of the activity of this enzyme, and red light (RL) retarded the rate of its functioning. Investigation of the level of fum 1 and fum 2 gene expression in green leaves showed that only gene fum 1 is actively expressed, whereas expression of fum 2 gene is blocked. The data obtained provide evidence that calcium ions in maize leaves are capable of acting as a second messenger in the light signal transduction, and the active phytochrome form being formed under RL action caused an accumulation of calcium ions behaving as a regulator of Krebs cycle functioning. Employment of ruthenium red, a known inhibitor of cell membrane Ca2+-channels, and Ca2+ chelator, EGTA, allowed us to find that the RL-induced change in the content of free calcium ions in cell nuclei of maize leaves is associated with their redistribution between cell compartments. The active phytochrome form caused the increase in the rate of pif3 gene transcription that was accompanied by inhibiting the functioning of fum 1 gene. Based on these results, it is suggested that transcription factor PIF3 can mediate the transduction of the phytochrome signal in the nucleus.
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