title: Real-time monitoring of chloroplast gene expression by a luciferase reporter: evidence for nuclear regulation of chloroplast circadian period.
abstract: Chloroplast-encoded genes, like nucleus-encoded genes, exhibit circadian expression. How the circadian clock exerts its control over chloroplast gene expression, however, is poorly understood. To facilitate the study of chloroplast circadian gene expression, we developed a codon-optimized firefly luciferase gene for the chloroplast of Chlamydomonas reinhardtii as a real-time bioluminescence reporter and introduced it into the chloroplast genome. The bioluminescence of the reporter strain correlated well with the circadian expression pattern of the introduced gene and satisfied all three criteria for circadian rhythms. Moreover, the period of the rhythm was lengthened in per mutants, which are phototactic rhythm mutants carrying a long-period gene in their nuclear genome. These results demonstrate that chloroplast gene expression rhythm is a bona fide circadian rhythm and that the nucleus-encoded circadian oscillator determines the period length of the chloroplast rhythm. Our reporter strains can serve as a powerful tool not only for analysis of the circadian regulation mechanisms of chloroplast gene expression but also for a genetic approach to the molecular oscillator of the algal circadian clock.
authors.affiliation: Center for Gene Research, Nagoya University, Furo, Chikusa, Nagoya 464-8602, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsuo
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Onai
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Okamoto
authors.forename: Jun
authors.initials: J
authors.lastname: Minagawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ishiura
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics*; D016825:Chlamydomonas reinhardtii / Q000235:genetics*; D002736:Chloroplasts / Q000201:enzymology / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D018742:DNA, Chloroplast / Q000235:genetics; D015870:Gene Expression; D017125:Genes, Protozoan / Q000235:genetics*; D017930:Genes, Reporter; D008156:Luciferases / Q000032:analysis / Q000235:genetics; D008163:Luminescent Measurements; D008969:Molecular Sequence Data; D013696:Temperature
chemical_list: D018742:DNA, Chloroplast; D008156:Luciferases