The regulation of circadian clock and circadian rhythms

Most of organisms on the earth evolve circadian clocks to control the oscillations of multiple physiological pathways in sync with the ~24-h period, upon the day-night cycles resulted from the earth rotation, such oscillations are called “circadian rhythms”. Besides the predictable day-night and seasonal cycles, plants are sessile in circumstances with numerous unpredictable transient changes during their growth and development. The rhythmicity of the “circadian clock” profoundly keeps plants on the track without over reacting to the random cues, therefore sustains propagating on an optimal season time. The circadian clock comprises genes tightly interlocked in regulatory feedback loops, in other words, clock related genes are directly or indirectly regulated by their downstream genes. Such regulatory feedback loops make genes peak at a specific time of the day and oscillate according to the external cues like light and temperature through the day-night cycles. In the model plant, Arabidopsis , LIGHT-REGULATED WD1 (LWD1) plays a role in the morning activation of circadian clock. The five WD repeats of LWD1 form a propeller structure and serve as a protein-protein interaction platform. In our previous study, we have revealed that LWDs form co-activator protein complexes with specific TCP members to directly activate the expression of morning gene CCA1 , thus, secure the normal operation of the circadian clock at dawn. However, expressions of several clock genes in the lwd1 lwd2 double mutant don't obey the interlocking gene circuits, e.g. genes and their repressors are down regulated simultaneously when lacking LWDs. This indicates that our knowledge of the circadian clock is not thorough. To investigate the regulatory mechanism of circadian clock, we will use LWD1 as bait to identify transcription factors with similar transcription trends through a plenty of transcriptomes. We will reveal the molecular mechanism of the circadian clock operation via the study of the LWD1 co-expressed transcription factors. Our study would unravel multifaceted connections between circadian clock and plant developmental processes.