Dodd et al. (Reports, 14 December 2007, p. 1789) reported that the Arabidopsis circadian clock incorporates the signaling molecule cyclic adenosine diphosphate ribose (cADPR In contrast, we found that there is no rhythm of cADPR levels nor are there any significant effects on the rhythm by cADPR overexpression, thus raising questions about the conclusions of Dodd et al.
