The Arabidopsis Circadian Clock Incorporates a cADPR-Based Feedback Loop

Abstract

Transcriptional feedback loops are a feature of circadian clocks in both animals and plants. We show that the plant circadian clock also incorporates the cytosolic signaling molecule cyclic adenosine diphosphate ribose (cADPR). cADPR modulates the circadian oscillator's transcriptional feedback loops and drives circadian oscillations of Ca2+ release. The effects of antagonists of cADPR signaling, manipulation of cADPR synthesis, and mathematical simulation of the interaction of cADPR with the circadian clock indicate that cADPR forms a feedback loop within the plant circadian clock.

Comparison of global responses to mild deficiency and excess copper levels in Arabidopsis seedlings

“…Moreover Ca 2+ fluxes and ROS production have already been reported to participate in both Cu signalling 54 and circadian rhythm regulation. 55 In light of this, some Cu-regulated categories in our microarray well fit processes that have been previously reported to be circadian clock-regulated: ion homeostasis, osmotic stress responses and cell growth. 56,57 The SDH1-2 expression increased at Cu levels of 5 mM in the growth medium (Fig.…”

Abiotic stress and the plant circadian clock

“…A key piece of molecular-genetic evidence mediating between the plant circadian clock and metabolism was provided by Dodd et al 64 These authors found that cyclic adenosine diphosphate ribose (cADPR), which is synthesized from NAD by the ADP ribosyl cyclase, peaked early in the morning and affected the oscillator. A decrease in the concentration of cADPR lengthened the period of clock-controlled genes, whereas nicotinamide inhibited the ADP ribosyl cyclase and weakened circadian calcium oscillations.…”

“…A decrease in the concentration of cADPR lengthened the period of clock-controlled genes, whereas nicotinamide inhibited the ADP ribosyl cyclase and weakened circadian calcium oscillations. 64 Previously it was demonstrated that ADPR cyclase activity was induced by ABA and that 30% of all ABA responsive genes were expressed in a similar pattern that those from cADPR. 75 Recalling that circadian clock microarray datasets overlapped with ABA transcriptomic profiles, 63 a link between the circadian clock and metabolism in plants through cADPR has been suggested.…”

“…Consequently the changes in cADPR and ABA would alter the pace of the clock. 64 Conceptually, any of these molecules could provide signals of stress to the oscillator. Taken together, these results suggest that a link exists between energy homeostasis and the plant circadian clock, though this interaction has not been completely defined.…”

“…75 Recalling that circadian clock microarray datasets overlapped with ABA transcriptomic profiles, 63 a link between the circadian clock and metabolism in plants through cADPR has been suggested. 64 What could emerge as a common factor between the clock, ABA and energy is the status of carbon availability throughout the day. Previously several screens for altered sugar responses led to the description of glucose insensitive (gin), sugar insensitive (sis) and sucrose uncoupled (sun) mutants.…”