This model consists of a single feedback loop. LHY transcription has a light-induced component, that is dependent on the concentration of the protein 'P', and a light-independent component that is activated by TOC1 protein. LHY translation and reversible transport into the nucleus are modelled as linear processes. Nuclear LHY protein acts as a repressor of TOC1 transcription. TOC1 translation and reversible transport into the nucleus are also modelled as linear processes.
Both RNAs and proteins are degraded enzymatically, according to Michaelis-Menten kinetics.
Protein 'P', is probably PIF3. Its production is switched on during darkness and off during the light period. In the presence of light it acts as an activator of LHY transciption. 'P' degradation has two components, a light-dependent linear process, and a light independent Michaelis-Menten process.