title: PSEUDO-RESPONSE REGULATORS, PRR9, PRR7 and PRR5, together play essential roles close to the circadian clock of Arabidopsis thaliana.
abstract: In Arabidopsis thaliana, a number of clock-associated protein components have been identified. Among them, CCA1 (CIRCADIAN CLOCK-ASSOCIATED 1)/LHY (LATE ELONGATED HYPOCOTYL) and TOC1 (TIMING OF CAB EXPRESSION 1) are believed to be the essential components of the central oscillator. CCA1 and LHY are homologous and partially redundant Myb-related DNA-binding proteins, whereas TOC1 is a member of a small family of proteins, designated as PSEUDO-RESPONSE REGULATOR. It is also believed that these two different types of clock components form an autoregulatory positive/negative feedback loop at the levels of transcription/translation that generates intrinsic rhythms. Nonetheless, it was not yet certain whether or not other PRR family members (PRR9, PRR7, PRR5 and PRR3) are implicated in clock function per se. Employing a set of prr9, prr7 and prr5 mutant alleles, here we established all possible single, double and triple prr mutants. They were examined extensively by comparing them with each other with regard to their phenotypes of circadian rhythms, photoperiodicity-dependent control of flowering time and photomorphogenic responses to red light during de-etiolation. Notably, the prr9 prr7 prr5 triple lesions in plants resulted in severe phenotypes: (i) arrhythmia in the continuous light conditions, and an anomalous phasing of diurnal oscillation of certain circadian-controlled genes even in the entrained light/dark cycle conditions; (ii) late flowering that was no longer sensitive to the photoperiodicity; and (iii) hyposensitivity (or blind) to red light in the photomorphogenic responses. The phenotypes of the single and double mutants were also characterized extensively, showing that they exhibited circadian-associated phenotypes characteristic for each. These results are discussed from the viewpoint that PRR9/PRR7/PRR5 together act as period-controlling factors, and they play overlapping and distinctive roles close to (or within) the central oscillator in which the relative, PRR1/TOC1, plays an essential role.
authors.affiliation: Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Norihito
authors.initials: N
authors.lastname: Nakamichi
authors.forename: Masanori
authors.initials: M
authors.lastname: Kita
authors.forename: Shogo
authors.initials: S
authors.lastname: Ito
authors.forename: Takafumi
authors.initials: T
authors.lastname: Yamashino
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mizuno
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001683:Biological Clocks / Q000235:genetics* / Q000528:radiation effects; D002940:Circadian Rhythm / Q000235:genetics* / Q000528:radiation effects; D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics* / Q000528:radiation effects; D055537:Light Signal Transduction / Q000187:drug effects / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D010775:Photic Stimulation; D017440:Photoperiod; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; D009687:Nuclear Proteins; C411822:TOC1 protein, Arabidopsis; D014157:Transcription Factors