Abstract
The results of recent extensive studies on Arabidopsis have begun to shed light on the molecular mechanisms underlying the circadian rhythm. Among Arabidopsis clock-associated factors, we have been characterizing a family of pseudo response regulators (PRRs), consisting of five members, considering the fact that one (PRR1) of them is identical to TOC1 which is believed to be a component of the central oscillator. It should be emphasized that we demonstrated that rice also has the analogous set of OsPRR genes, the expression of which are circadian-regulated. To clarify the function of OsPRR1, which seemed to be orthologous to AtPRR1 (or TOC1), the OsPRR1 gene was overexpressed in Arabidopsis plants, and the resultant OsPRR1-ox transgenic lines were compared with AtPRR1-ox with reference to certain circadian-associated phenotypes. This and other results strongly supported the idea that OsPRR1 is indeed orthologous to the AtPRR1 clock-component, as judged by its functional properties in Arabidopsis.
