2nd Nov., 2013. In an article titled, “Photosynthetic entrainment of  the Arabidopsis thaliana  circadian clock,” published online  23rd October, ’13, edition of Nature, Alex AR Webb and four of his associates draw our attention to the fact that circadian clocks consist of transcription-translation feedback loops. The latter is controlled by environmental signals such as light and temperature to adjust the phase of rhythms to match the local environment.

By inhibiting photosynthesis, the authors have demonstrated that endogenous oscillations in sugar levels provide metabolic feedback to the circadian oscillator through the morning-expressed gene PSEUDO-RESPONSE REGULATOR 7 (PRR7). Furthermore the authors have identified that the recessive form of this allele, namely, prr7 mutants are insensitive to the effects of sucrose on the circadian period. Thus, the experimental results reveal that photosynthesis has a marked effect on the entrainment and maintenance of robust circadian rhythms in A. thaliana.  These results demonstrate that metabolism has a crucial role in regulation of the circadian clock.