Journal Article

The <i>Arabidopsis</i> Pseudo-response Regulators, PRR5 and PRR7, Coordinately Play Essential Roles for Circadian Clock Function

Norihito Nakamichi, Masanori Kita, Shogo Ito, Eriko Sato, Takafumi Yamashino and Takeshi Mizuno

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 4, pages 609-619
Published in print April 2005 | ISSN: 0032-0781
Published online April 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci061
The Arabidopsis Pseudo-response Regulators, PRR5 and PRR7, Coordinately Play Essential Roles for Circadian Clock Function

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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In Arabidopsis thaliana, a number of clock-associated protein factors have been identified. Among them, TOC1 (TIMING OF CAB EXPRESSION 1) is believed to be a component of the central oscillator. TOC1 is a member of a small family of proteins, designated as ARABIDOPSIS PSEUDO-RESPONSE REGULATOR, including PRR1/TOC1, PRR3, PRR5, PRR7 and PRR9. It has not been certain whether or not other PRR family members are also implicated in clock function per se. To clarify this problem, here we constructed a double mutant line, which is assumed to have severe lesions in both the PRR5 and PRR7 genes. Resulting homozygous prr5-11 prr7-11 young seedlings showed a marked phenotype of hyposensitivity to red light during de-etiolation. In addition, they displayed a phenotype of extremely late flowering under long-day photoperiod conditions, but not short-day conditions. The rhythms at the level of transcription of certain clock-controlled genes were severely perturbed in the double mutant plants when they were released into continuous light (LL) and darkness (DD). The observed phenotype was best interpreted as ‘arrhythmic in both LL and DD’ and/or ‘very short period with markedly reduced amplitude’. Even under the light entrainment (LD) conditions, the mutant plants showed anomalous diurnal oscillation profiles with altered amplitude and/or phase with regard to certain clock-controlled genes, including the clock component CCA1 (CIRCADIAN CLOCK-ASSOCIATED 1) gene. Such events were observed even under temperature entrainment conditions, suggesting that the prr5-11 prr7-11 lesions cannot simply be attributed to a defect in the light signal input pathway. These pleiotropic circadian-associated phenotypes of the double mutant were very remarkable, as compared with those observed previously for each single mutant. Taking these results together, we propose for the first time that PRR5 and PRR7 coordinately (or synergistically) play essential clock-associated roles close to the central oscillator.

Keywords: Arabidopsis; Circadian rhythms; Control of flowering; Light signaling; Pseudo-response regulator; DD, darkness; FFT-NLLS, fast Fourier transform-non-linear least squares; LD, 12 h light/12 h dark; LL, continuous light

Journal Article.  8202 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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