Shining a light on the Arabidopsis circadian clock

Abstract

The circadian clock provides essential timing information to ensure optimal growth to prevailing external environmental conditions. A major time-setting mechanism (zeitgeber) in clock synchronization is light. Differing light wavelengths, intensities, and photoperiodic duration are processed for the clock-setting mechanism. Many studies on light-input pathways to the clock have focused on Arabidopsis thaliana. Photoreceptors are specific chromic proteins that detect light signals and transmit this information to the central circadian oscillator through a number of different signalling mechanisms. The most well-characterized clock-mediating photoreceptors are cryptochromes and phytochromes, detecting blue, red, and far-red wavelengths of light. Ultraviolet and shaded light are also processed signals to the oscillator. Notably, the clock reciprocally generates rhythms of photoreceptor action leading to so-called gating of light responses. Intermediate proteins, such as Phytochrome interacting factors (PIFs), constitutive photomorphogenic 1 (COP1) and EARLY FLOWERING 3 (ELF3), have been established in signalling pathways downstream of photoreceptor activation. However, the precise details for these signalling mechanisms are not fully established. This review highlights both historical and recent efforts made to understand overall light input to the oscillator, first looking at how each wavelength of light is detected, this is then related to known input mechanisms and their interactions.

OsPRR37confers an expanded regulation of the diurnal rhythms of the transcriptome and photoperiodic flowering pathways in rice

“…OsPRR37 in regulating gene transcription and the response to light or other stimuli. These findings are consistent with OsPRR37 as both a transcriptional repressor and a clock gene that is regulated by light and other stimuli (Dubois, Claeys, Van den Broeck, & Inze, 2017;Farré & Kay, 2007;Haydon, Mielczarek, Robertson, Hubbard, & Webb, 2013;Murphy et al, 2011;Oakenfull & Davis, 2017). However, we found that the enriched GO categories in the up-regulated rhythmic DEGs were the protein amino acid phosphorylation, protein modification process, phosphate metabolic process, signal transducer activity and protein kinase activity, etc.…”

On the move through time – a historical review of plant clock research

“…, 1995b; Somers et al . ; Oakenfull & Davis ). An essential function of the clock is to direct downstream processes to take place at the optimal time of day.…”

Retrograde signalling as an informant of circadian timing

“…The expression of dawn‐phased clock components tends to be induced by light, whereas the Evening Complex has been identified as a likely hub for signal integration as it interacts directly with the photo‐ and thermo‐sensor phytochromeB (phyB; Hsu & Harmer, ; H. Huang et al ., ; Ezer et al ., ). The role of phytochrome, cryptochrome and UVR8 photoreceptors in the circadian system has recently been discussed elsewhere (Oakenfull & Davis, ). Instead, this review focuses on our understanding of how metabolic changes induced by environmental fluctuations affect circadian timing.…”

“…Huang et al, 2016;Ezer et al, 2017). The role of phytochrome, cryptochrome and UVR8 photoreceptors in the circadian system has recently been discussed elsewhere (Oakenfull & Davis, 2017). Instead, this review focuses on our understanding of how metabolic changes induced by environmental fluctuations affect circadian timing.…”