title: The EC night-time repressor plays a crucial role in modulating circadian clock transcriptional circuitry by conservatively double-checking both warm-night and night-time-light signals in a synergistic manner in Arabidopsis thaliana.
abstract: During the last decade, significant research progress has been made in Arabidopsis thaliana in defining the molecular mechanisms behind the plant circadian clock. The circadian clock must have the ability to integrate both external light and ambient temperature signals into its transcriptional circuitry to regulate its function properly. We previously showed that transcription of a set of clock genes including LUX (LUX ARRHYTHMO), GI (GIGANTEA), LNK1 (NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED GENE 1), PRR9 (PSEUDO-RESPONSE REGULATOR 9) and PRR7 is commonly regulated through the evening complex (EC) night-time repressor in response to both moderate changes in temperature (Δ6°C) and differences in steady-state growth-compatible temperature (16-28°C). Here, we further show that a night-time-light signal also feeds into the circadian clock transcriptional circuitry through the EC night-time repressor, so that the same set of EC target genes is up-regulated in response to a night-time-light pulse. This light-induced event is dependent on phytochromes, but not cryptochromes. Interestingly, both the warm-night and night-time-light signals negatively modulate the activity of the EC night-time repressor in a synergistic manner. In other words, an exponential burst of transcription of the EC target genes is observed only when these signals are simultaneously fed into the repressor. Taken together, we propose that the EC night-time repressor plays a crucial role in modulating the clock transcriptional circuitry to keep track properly of seasonal changes in photo- and thermal cycles by conservatively double-checking the external light and ambient temperature signals.
authors.affiliation: Laboratory of Molecular and Functional Genomics, School of Agriculture, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mizuno
authors.affiliation: Laboratory of Molecular and Functional Genomics, School of Agriculture, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Kitayama
authors.affiliation: Laboratory of Molecular and Functional Genomics, School of Agriculture, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Oka
authors.affiliation: Laboratory of Molecular and Functional Genomics, School of Agriculture, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Mayuka
authors.initials: M
authors.lastname: Tsubouchi
authors.affiliation: Laboratory of Molecular and Functional Genomics, School of Agriculture, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Chieko
authors.initials: C
authors.lastname: Takayama
authors.affiliation: Laboratory of Molecular and Functional Genomics, School of Agriculture, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nomoto
authors.affiliation: Laboratory of Molecular and Functional Genomics, School of Agriculture, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan yamasino@agr.nagoya-u.ac.jp.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Yamashino
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D057906:Circadian Clocks / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D008027:Light; D046912:Multiprotein Complexes; D009154:Mutation; D015398:Signal Transduction; D013696:Temperature
chemical_list: D029681:Arabidopsis Proteins; D046912:Multiprotein Complexes
keywords: Arabidopsis thaliana; Circadian clock; Light response; Temperature response; Transcriptional regulation