Temperature is an overlooked player in studies of the circadian clock. While it is true that light has the strongest influence on setting the circadian clock, temperature is also crucial in regulating circadian rhythms. While plants are in constant conditions in terms of light (continuous light or continuous dark), 24-hour cycles of warm/cool are sufficient to set oscillations correctly: dawn corresponds to a rise in temperature and dusk to a decrease in temperature. In addition, circadian rhythms exhibit temperature compensation, which is the ability to maintain precise 24-hour rhythms despite external temperature fluctuations. The circadian clock is thus able to “learn” from temperature cycles whether it is day or night, while also making sure circadian rhythms never speed up or slow down if the environment gets hot or cold.
It is evident that temperature plays a very important role in the plant circadian clock, but very little is understood about which genes sense temperature cues and how this information is transmitted to the circadian clock. Studying the effect of temperature on plants is of particular interest in the face of global climate change. Considering that the circadian clock is a master regulator of many developmental and metabolic processes in plants, the global changes in the environment’s temperature could have a profound impact on any of these processes. One of the projects in the Harmon Lab is to use the model plant Arabidopsis thaliana to discover new genes involved in sensing or transmitting temperature cues to the circadian clock. An EMS mutagenesis screen has unveiled the warm acute response of prr7 mutants (warp). These mutants are the first step in exploring the relationship between plant circadian rhythms and temperature.
