Abstract
Although circadian rhythms of various processes have been observed in higher plants, few examples have been examined in relatively primitive land plants such as pteridophytes and bryophytes. Recently, the author's group observed circadian expression of the PpLhcb2 gene, which encodes a light-harvesting chlorophyll a/b-binding protein, in the moss Physcomitrella patens. Analyses of this rhythm suggest that the regulatory mechanism of the circadian clock of P. patens may be at least partly different from that of higher plants. In this short essay, the author briefly summarizes current studies on the mechanism of the circadian clock in Arabidopsis thaliana, and on circadian rhythms of primitive plant species. In particular, the essay will focus on recent observations by the author's group about circadian clock-related genes in P. patens, and discuss the possibility that P. patens could be a useful model for studies on the molecular mechanisms of the circadian clock.
