 | Figure 2
Nature Genetics
22, 217 - 219 (1999)
doi:10.1038/10270
Clocks, criteria and critical genesRussell G Foster
& Robert J Lucas | | | | Figure 2. A simple conceptualization of the circadian light entrainment pathway,
in which the first stage is the absorption of a photon by a light-sensitive
pigment.
The change induced by the photon is then transmitted by a signal transduction
process to induce a phase adjustment of the circadian oscillator. The components
of this system can therefore be defined using the following criteria.
Photopigment: components that absorb light, showing a consequent change
in their activity and have an absorption spectrum matching the action spectrum
for circadian phase shifts; genetic ablation of these reduces circadian photosensitivity,
alters the action spectrum in a predictable manner or abolishes photoentrainment.
Transduction pathway: non-light absorbing components, genetic ablation
of which abolishes photoentrainment or reduces circadian photosensitivity.
Oscillator component: for criteria, see Fig. 1.
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