Recently, our school and the Institute of Biotechnology of the Chinese Academy of Agricultural Sciences have revealed the molecular mechanism of the natural light signal pathway and the biological clock interaction in plants to coordinately regulate the rhythmic expression of the key gene of the biological clock CCA1. Related research results are in the internationally renowned journal Plant Cell Cell (IF5Y = 9.848) was officially published. (Link to the paper: www.plantcell.org/cgi/doi/10.1105/tpc.19.00981)

  During the long-term evolution of natural selection, plants produced a circadian clock with a period of nearly 24 hours. The circadian clock is involved in regulating almost all the metabolism and growth and development of the plant. Light is the main factor regulating the biological clock under natural environmental conditions. Plants transmit the changes of external signals to the biological clock central oscillator through the input pathway to regulate the expression of the core gene of the central oscillator, and then regulate various rhythmic responses in the plant through the output pathway. The Arabidopsis CCA1 gene encodes a MYB transcription factor protein, which is a core member of the central oscillator of the circadian clock. Its expression shows obvious rhythm. In the morning, it is activated by light induction and the transcription level is increased, thereby suppressing the evening genes (such as TOC1). expression. The expression of CCA1 is suppressed in the late day and night, and the suppression of the evening gene is gradually released, so that the evening gene can be expressed. Such feedback regulation constitutes the core central oscillator of the biological clock. However, the rhythmic expression of the CCA1 gene and the molecular mechanism of light activation remain unclear.

　　Researchers found that the important factors of light signal transduction, FHY3 and FAR1, directly bind to the promoter of the CCA1 gene, which is crucial for the light-induced activation of CCA1. The photosensitizing pigment binding protein PIF5 inhibits its expression level by directly binding to the CCA1 promoter. The researchers further found that PIF5 and other key factors of the biological clock, TOC1, can directly interact with FHY3 and FAR1 proteins, and inhibit the transcriptional activation function of FHY3 and FAR1. Finally, the researchers found that the protein expression levels of FHY3, PIF5, and TOC1 were rhythmic, and their ability to bind the CCA1 promoter showed significant differences under day-night cycle conditions. In the early morning, high levels of FHY3 and lower levels of PIF5 and TOC1 proteins together maintained the expression of CCA1 gene peaking in the early morning. The study established a molecular network of light and circadian clock synergistic regulation of the key gene CCA1 of the circadian clock, which is of great significance to elucidate the molecular regulation mechanism of the reset of the entire circadian clock and to cultivate new varieties of crops with wide adaptability.

  The research was completed with the Institute of Biotechnology, Chinese Academy of Agricultural Sciences as the first unit, Associate Researcher Liu Yang and Assistant Researcher Ma Mengdi as the co-first authors, and Professor Wang Haiyang of our school as the corresponding author. The research was supported by the National Natural Science Foundation of China and the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences.