在植物中，糖通過光合作用的生成是生物鐘的一個關鍵代謝輸出。
這項研究顯示，節律性的內源糖信號能通過調控生物鐘基因的表達設定擬南芥的生物鐘的時間。
作者提出了「代謝黎明」這樣一個概念，用來描述生物鐘響應於光合作用所生成的內源性的糖的某一峰值而發生的重設。（生物谷Bioon.com）
生物谷推薦的英文摘要
Nature doi:10.1038/nature12603
Photosynthetic entrainment of the Arabidopsis thaliana circadian clock
Michael J. Haydon，Olga Mielczarek，Fiona C. Robertson，E. Hubbard& Alex A. R. Webb
Circadian clocks provide a competitive advantage in an environment that is heavily influenced by the rotation of the Earth1， 2， by driving daily rhythms in behaviour， physiology and metabolism in bacteria， fungi， plants and animals3， 4. Circadian clocks comprise transcription–translation feedback loops， which are entrained by environmental signals such as light and temperature to adjust the phase of rhythms to match the local environment3. The production of sugars by photosynthesis is a key metabolic output of the circadian clock in plants2， 5. Here we show that these rhythmic， endogenous sugar signals can entrain circadian rhythms in Arabidopsis thaliana by regulating the gene expression of circadian clock components early in the photoperiod， thus defining a 『metabolic dawn』. By inhibiting photosynthesis， we demonstrate that endogenous oscillations in sugar levels provide metabolic feedback to the circadian oscillator through the morning-expressed gene PSEUDO-RESPONSE REGULATOR 7 (PRR7)， and we identify that prr7 mutants are insensitive to the effects of sucrose on the circadian period. Thus， photosynthesis has a marked effect on the entrainment and maintenance of robust circadian rhythms in A. thaliana， demonstrating that metabolism has a crucial role in regulation of the circadian clock.