Abstract
Arabidopsis has the family of pseudo response regulators (PRRs): one of the members (PRR1/TOC1) is believed to be a component of the central oscillator, in which the CCA1 and LHY transcription factors are also implicated. PRRs are nuclear-localized proteins, otherwise nothing is known about their molecular function(s). In their primary amino acid sequences, however, they share an intriguing structural design. Each contains an N-terminal pseudo receiver domain, followed by C-terminal CCT motif found also in CONSTANS. To clarify the molecular function(s), here we constructed a series of transgenic lines, each of which was designed so as to overexpress only the N-terminal or C-terminal domain separately. Such transgenic lines were constructed for PRR1, PRR5, and PRR9, and then they were characterized with special reference to the circadian clock-associated phenotypes. We present the results of such extensive genetic analyses in the context of the current idea of the clock-associated functions of PRRs.
