Abstract

Circadian clock allows organisms to anticipate daily light and temperature cycles. In plants, circadian rhythms control many biological processes like gene expression and the circadian oscillations of cytosolic-free Ca2+ ([Ca2+]cyt). Since the first model of the oscillator was proposed, the plant clock has been expanded into a complex network of interconnected feedback loops including the cytosolic molecule, cyclic adenosine diphosphate ribose which was proposed to be required to drive circadian [Ca2+]cyt oscillations and modulate the nuclear transcriptional feedback loop of the Arabidopsis circadian oscillator. These findings and the scarce information about the function of circadian [Ca2+]cyt oscillations in both plants and animals, raised the question about whether [Ca2+]cyt regulates the clock.

I will present the different approaches undertaken in the lab to demonstrate that Ca2+cyt is a switch in the Arabidopsis circadian clock that regulates circadian clock gene expression. I will also show that calcium-binding Calmodulin Like Protein 23 (CML23) and CML24 act as Ca2+-signalling components that regulate the circadian network through genetic interaction with CCA1 HIKING EXPEDITION (CHE).