Quantitative analysis of regulatory flexibility under changing environmental conditions

Mol Syst Biol. 2010 Nov 2;6:424. doi: 10.1038/msb.2010.81.

Abstract

The circadian clock controls 24-h rhythms in many biological processes, allowing appropriate timing of biological rhythms relative to dawn and dusk. Known clock circuits include multiple, interlocked feedback loops. Theory suggested that multiple loops contribute the flexibility for molecular rhythms to track multiple phases of the external cycle. Clear dawn- and dusk-tracking rhythms illustrate the flexibility of timing in Ipomoea nil. Molecular clock components in Arabidopsis thaliana showed complex, photoperiod-dependent regulation, which was analysed by comparison with three contrasting models. A simple, quantitative measure, Dusk Sensitivity, was introduced to compare the behaviour of clock models with varying loop complexity. Evening-expressed clock genes showed photoperiod-dependent dusk sensitivity, as predicted by the three-loop model, whereas the one- and two-loop models tracked dawn and dusk, respectively. Output genes for starch degradation achieved dusk-tracking expression through light regulation, rather than a dusk-tracking rhythm. Model analysis predicted which biochemical processes could be manipulated to extend dusk tracking. Our results reveal how an operating principle of biological regulators applies specifically to the plant circadian clock.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / physiology
  • CLOCK Proteins / genetics
  • CLOCK Proteins / physiology
  • Circadian Clocks / genetics
  • Circadian Clocks / physiology*
  • Gene Regulatory Networks / physiology*
  • Genes, Reporter
  • Ipomoea nil / physiology
  • Models, Biological
  • Photoperiod
  • Systems Biology / methods*

Substances

  • CLOCK Proteins