title: Modeling the photoperiodic entrainment of the plant circadian clock.
abstract: The circadian clock is an endogenous 24 hour rhythm that helps organisms anticipate and adapt to daily and seasonal variations in environment, such as the day/night cycle or changing temperatures. The plant clock is a complex network of transcription factors that regulate each other, forming interlocked feedback loops. Most of its components are light-regulated in some way, making the system highly sensitive to changes in light conditions. Here, we explore the mechanisms by which the plant clock adapts to changing day length. We first present some experimental data illustrating the variety of behaviors found in seedlings exposed to external day/night cycles different from 24h. We then use a mathematical model to characterize the response of the clock to a wide range of external cycle lengths and photoperiods. We show the existence of several domains of periodic entrainment with different ratios between the external cycle length and the period of the clock, and the presence of quasiperiodic and chaotic behaviors outside of the entrainment range. We simulate knockout mutants with impaired clock function and theoretical variants with diminished light sensitivity to highlight the role of a complex network and multiple light inputs in keeping the clock entrained over a wide range of conditions.
authors.affiliation: Unité de Chronobiologie Théorique, Faculté des Sciences, CP 231, Université Libre de Bruxelles, Bvd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Joëlle
authors.initials: J
authors.lastname: De Caluwé
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Interfaculty School of Bioengineers, CP 242, Université Libre de Bruxelles, Bvd du Triomphe, 1050 Brussels, Belgium.
authors.forename: José Romário Fernandes
authors.initials: JRF
authors.lastname: de Melo
authors.affiliation: Unité de Chronobiologie Théorique, Faculté des Sciences, CP 231, Université Libre de Bruxelles, Bvd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Alen
authors.initials: A
authors.lastname: Tosenberger
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Interfaculty School of Bioengineers, CP 242, Université Libre de Bruxelles, Bvd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Christian
authors.initials: C
authors.lastname: Hermans
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Interfaculty School of Bioengineers, CP 242, Université Libre de Bruxelles, Bvd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Verbruggen
authors.affiliation: Unité de Chronobiologie Théorique, Faculté des Sciences, CP 231, Université Libre de Bruxelles, Bvd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Leloup
authors.affiliation: Unité de Chronobiologie Théorique, Faculté des Sciences, CP 231, Université Libre de Bruxelles, Bvd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Didier
authors.initials: D
authors.lastname: Gonze
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology; D057906:Circadian Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D008027:Light; D008954:Models, Biological; D017440:Photoperiod; D014157:Transcription Factors / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D014157:Transcription Factors
keywords: Arabidopsis thaliana; Arnold onion; Chaos; Light-dark cycles; Limit cycle oscillations