Circadian oscillations of cytosolic free calcium regulate the Arabidopsis circadian clock

In the last decade, the view of circadian oscillators has expanded from transcriptional feedback to incorporate post-transcriptional, post-translational, metabolic processes and ionic signalling. In plants and animals, there are circadian oscillations in the concentration of cytosolic free Ca 2+ ([Ca 2+ ] cyt ), though their purpose has not been fully characterized. We investigated whether circadian oscillations of [Ca 2+ ] cyt regulate the circadian oscillator of Arabidopsis thaliana . We report that in Arabidopsis , [Ca 2+ ] cyt circadian oscillations can regulate circadian clock function through the Ca 2+ -dependent action of CALMODULIN-LIKE24 (CML24). Genetic analyses demonstrate a linkage between CML24 and the circadian oscillator, through pathways involving the circadian oscillator gene TIMING OF CAB2 EXPRESSION1 ( TOC1 ).