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Topological difference of core regulatory networks induces different entrainment characteristics of plant and animal circadian clocks.

ABSTRACT: The plant circadian rhythm is quickly entrained to the change of a light stimulus but the mammalian circadian rhythm shows a relatively slow entrainment. Where does such a different entrainment feature of plants and mammals originate? To answer this question, we have investigated circadian regulatory networks of various species and identified the respective core structures of plants and animals. The core circadian regulatory network of plants is composed of two coupled negative feedback loops while the core network of animals consists of coupled negative and positive feedback loops. In addition, the way of regulation (gene transcription or protein degradation) induced by a light stimulus differs depending on species. Mathematical simulations revealed that the topological difference of the core regulatory networks as well as the different way of regulation induced by a light stimulus leads to the different entrainment characteristics of plant and animal circadian clocks.

SUBMITTER: Kim JR

PROVIDER: S-EPMC1914418 | biostudies-literature | 2007 Jul

REPOSITORIES: biostudies-literature

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Topological difference of core regulatory networks induces different entrainment characteristics of plant and animal circadian clocks.

Kim Jeong-Rae JR Bae Won-Soung WS Yoon Yeoin Y Cho Kwang-Hyun KH

Biophysical journal 20070420 1

The plant circadian rhythm is quickly entrained to the change of a light stimulus but the mammalian circadian rhythm shows a relatively slow entrainment. Where does such a different entrainment feature of plants and mammals originate? To answer this question, we have investigated circadian regulatory networks of various species and identified the respective core structures of plants and animals. The core circadian regulatory network of plants is composed of two coupled negative feedback loops wh ...[more]

PMID: 17449676

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Project description:BackgroundCircadian rhythms are endogenous, self-sustained oscillations with approximately 24-hr rhythmicity that are manifested in various physiological and metabolic processes. The circadian organization of these processes in mammals is governed by the master oscillator within the suprachiasmatic nuclei (SCN) of the hypothalamus. Recent findings revealed that circadian oscillators exist in most organs, tissues, and even in immortalized cells, and that the oscillators in peripheral tissues are likely to be coordinated by SCN, the master oscillator. Some candidates for endogenous entrainment factors have sporadically been reported, however, their details remain mainly obscure.ResultsWe developed the in vitro real-time oscillation monitoring system (IV-ROMS) by measuring the activity of luciferase coupled to the oscillatory gene promoter using photomultiplier tubes and applied this system to screen and identify factors able to influence circadian rhythmicity. Using this IV-ROMS as the primary screening of entrainment factors for circadian clocks, we identified 12 candidates as the potential entrainment factor in a total of 299 peptides and bioactive lipids. Among them, four candidates (endothelin-1, all-trans retinoic acid, 9-cis retinoic acid, and 13-cis retinoic acid) have already been reported as the entrainment factors in vivo and in vitro. We demonstrated that one of the novel candidates, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), a natural ligand of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma), triggers the rhythmic expression of endogenous clock genes in NIH3T3 cells. Furthermore, we showed that 15d-PGJ2 transiently induces Cry1, Cry2, and Roralpha mRNA expressions and that 15d-PGJ2-induced entrainment signaling pathway is PPAR-gamma--and MAPKs (ERK, JNK, p38MAPK)-independent.ConclusionHere, we identified 15d-PGJ2 as an entrainment factor in vitro. Using our developed IV-ROMS to screen 299 compounds, we found eight novel and four known molecules to be potential entrainment factors for circadian clocks, indicating that this assay system is a powerful and useful tool in initial screenings.

Dataset Information

Topological difference of core regulatory networks induces different entrainment characteristics of plant and animal circadian clocks.

Publications

Topological difference of core regulatory networks induces different entrainment characteristics of plant and animal circadian clocks.

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